Patent Publication Number: US-2015085629-A1

Title: Thermally assisted magnetic head, method of manufacturing the same, head gimbal assembly, and hard disk drive

Description:
BACKGROUND 
     1. Field of the Invention 
     The present invention relates to a thermally assisted magnetic head recording data on a magnetic recording medium by thermally assisted magnetic recording using near-field light and a method of manufacturing the same, and a head gimbal assembly and a hard disk drive each having a thermally assisted magnetic head. 
     2. Related Background Art 
     In recent years, as hard disk drives have been increasing their recording densities, thin-film magnetic heads recording data on magnetic recording media have been required to further improve their performances. As the thin-film magnetic heads, those of composite type having a structure in which a reproducing head having a magnetoresistive device (hereinafter, referred to also as an “MR device”) for read and a recording head having an electromagnetic coil device for write are laminated have been conventionally in wide use. In a magnetic disk drive, the thin-film magnetic head is provided on a slider which very slightly floats from the magnetic recording medium. 
     Incidentally, the magnetic disk drive records data by magnetizing magnetic fine particles on the magnetic recording medium using the recording head. In order to increase the recording density of the magnetic recording medium, it is effective to make the magnetic fine particles smaller. 
     When the magnetic fine particles are made smaller, however, there arises a problem that the magnetization thereof becomes unstable with respect to heat as the particles reduce in volume, thereby increasing the possibility that the data recorded on the magnetic recording medium is lost. To solve the problem, it is effective to increase the magnetic energy of the magnetic fine particles to thereby enhance the stability of magnetization. When the magnetic energy of the magnetic fine particles is increased, however, there arises another problem that the coercive force (difficulty in reversing magnetization) of the magnetic recording medium increases to deteriorate the data recording performance. 
     To solve such problems, a method called thermally assisted magnetic recording has been conventionally proposed. When recording data on a magnetic recording medium having a large coercive force, the thin-film magnetic head employing the thermally assisted magnetic recording (hereinafter, referred to as a “thermally assisted magnetic head”) records data while instantaneously heating and thereby increasing the temperature of a portion of the magnetic recording medium where data will be recorded. 
     Since the magnetic fine particles decrease in coercive force when the temperature is increased, instantaneous heating makes it possible to record data even on the magnetic recording medium having a high coercive force at room temperature. The portion of the magnetic recording medium where the data has been recorded is decreased in temperature after the recording of data and thereby increases in coercive force. Therefore, by using the thermally assisted magnetic head, it becomes possible to make the magnetic fine particles finer as well as stabilize recording in the magnetic disk drive. 
     On the other hand, near-field light is used as means for heating the magnetic recording medium in the conventional thermally assisted magnetic head. When light enters an opening smaller than the wavelength of light, the light slightly seeps from the opening and locally exists near the opening. The light locally existing near the opening is called near-field light. The near-field light is confined in a region much smaller than that of a spot light obtained by collecting light using a lens, so that use of the near-field light makes it possible to heat only a limited extremely small recording region of the magnetic recording medium. 
     Known as a method of generating the near-field light in the conventional thermally assisted magnetic head is a method using a plasmon generator (also called a plasmon probe) that is a minute metal piece. In this method, the near-field light is generated by guiding laser light to the plasmon generator via an optical waveguide. 
     As a conventional plasmon generator, a light scattering body in a triangular thin plate structure is disclosed in Japanese Patent Application Laid-Open No. 2005-4901 (referred also to as patent document 1), for example. Further, a plasmon probe made of metal such as gold, silver, aluminum or the like in the shape of a triangle pole is disclosed in Japanese Patent Application Laid-Open No. 2007-257753 (referred also to as patent document 2). Furthermore, a near-field light generating part in an isosceles triangle including a tip end reaching a medium-opposing surface is disclosed in Japanese Patent Application Laid-Open No. 2007-164935 (referred also to as patent document 3). A near-field light generating part in a triangle pole shape formed on an optical waveguide is disclosed in Japanese Patent Application Laid-Open No. 2012-3830 (referred also to as patent document 4). A near-field light generating part in a triangle shape formed on an optical emitting surface of a medium-opposing surface side of an optical waveguide is disclosed in Japanese Patent Application Laid-Open No. 2008-257819 (referred also to as patent document 5). 
     SUMMARY OF THE INVENTION 
     As described above, in the conventional thermally assisted magnetic head, the laser light are guided to the plasmon generator to excite surface plasmons to generate the near-field light based on the surface plasmons. This near-field light is used as means for heating the magnetic recording medium. 
     The plasmon generator, however, generates heat in itself accompanying the generation of the near-field light. In addition, the plasmon generator has a very small size and made of metal such as gold, silver, aluminum, palladium or the like and thus causes self expansion due to its own heat generation. Then, since the thermally assisted magnetic head has a medium-opposing surface opposing the magnetic recording medium and the plasmon generator has a tip end portion reaching the medium-opposing surface, the tip end portion projects to approach from the medium-opposing surface to the magnetic recording medium. Thus, the conventional thermally assisted magnetic head has a problem that the medium-opposing surface is likely to project and collide with the magnetic recording medium due to the magnetic recording action. 
     Further, the plasmon generator is likely to melt, when it becomes high temperature due to the self heat generation. Then, the shape of the plasmon generator changes, and thereby it becomes difficult that an extremely small recording region of the magnetic recording medium is heated intensively. 
     In addition, after the self-expansion due to the self heat generation, the plasmon generator shrinks when it&#39;s temperature falls down. On that occasion, a front end face of the plasmon generator sometimes has receded more than another part of the medium-opposing surface. 
     To increase the recording density in a magnetic recording apparatus, a smaller spot diameter of the near-field light is more preferable. To generate the near-field light having a small spot diameter and sufficient intensity, it is effective to concentrate much surface plasmons to the tip end part of the plasmon generator. In such a configuration, however, there is another problem that though near-field light having a high electric field intensity is generated from the tip end part, the generated heat also increases to cause the tip end part to be more likely to project from the medium-opposing surface and to be more likely to melt. 
     In addition, gold or silver is softer than other metals and thus causes especially the following problem when the plasmon generator is formed only of gold or silver. Specifically, polishing for forming the medium-opposing surface is performed in the manufacturing process of the thermally assisted magnetic head. In this event, etching is sometimes performed on a portion to be polished, and the etching sometimes causes the plasmon generator to recede more than the other part of the medium-opposing surface. 
     For the above-described reasons, there is a problem that the reliability of the thermally assisted magnetic head is low, especially when the plasmon generator is formed only of gold or silver. 
     The present invention is made to solve the above problems, and it is an object to provide a thermally assisted magnetic head having a structure in which projection, melting, deformation and recess of a plasmon generator is reduced to increase the reliability of the thermally assisted magnetic head and a method of manufacturing the same, and a head gimbal assembly and a hard disk drive each including the thermally assisted magnetic head. 
     To solve the above problems, the present invention is a thermally assisted magnetic head including a main magnetic pole layer having a magnetic pole end face arranged within a medium-opposing surface opposing a magnetic recording medium; a near-field light generating layer having a generating end part arranged within the medium-opposing surface, the generating end part generating near-field light for heating the magnetic recording medium; and an optical waveguide guiding light to the near-field light generating layer, the near-field light generating layer has a laminated structure in which a first thin-film metal layer formed in a thin film form along a direction intersecting the medium-opposing surface and a second thin-film metal layer formed in a thin film form along the direction intersecting the medium-opposing surface and formed using a second metal larger in hardness than a first metal forming the first thin-film metal layer are alternately laminated, and in the second thin-film metal layer, a defect part is formed, the defect part is a part smaller in thickness than another part or is a hole part, and a flat layer part other than the defect part surrounds the defect part. 
     In the thermally assisted magnetic head, the near-field light generating layer has a laminated structure in which a first thin-film metal layer and a second thin-film metal layer are alternately laminated, a defect part is formed in the second thin-film metal layer, and a flat layer part other than the defect part surrounds the defect part. The second thin-film metal layer is formed using a second metal larger in hardness than a first metal and thus exerts an effect of stopping deformation of the first thin-film metal layer, and the defect part is formed in the second thin-film metal layer to reduce the volume of the second metal contained in the near-field light generating layer. 
     In the above-described thermally assisted magnetic head, it is preferable that in the near-field light generating layer, at least two second thin-film metal layers are laminated, and the first thin-film metal layer is laminated between the two second thin-film metal layers, and the second thin-film metal layer has a net-like structure in which a plurality of the defect parts are scattered not in contact with one another and the flat layer part surrounds the respective defect parts, the flat layer part continues without a break due to the defect parts. 
     When the second thin-film metal layer has a net-like structure in which the flat layer part continues without a break due to the defect parts, the defect parts are arranged in balanced manner, so that the second thin-film metal layer maintains its outer shape even if external force is applied thereto from any direction. 
     Further, in the above-described thermally assisted magnetic head, it is preferable that the optical waveguide has a waveguide end face arranged within the medium-opposing surface, and extends in a depth direction intersecting the medium-opposing surface from the waveguide end face, and has an upper end face on a side closer to the main magnetic pole layer, the thermally assisted magnetic head further includes an interposed layer which is in direct contact with the upper end face of the optical waveguide, and a closely adhesive layer which makes the near-field light generating layer closely adhere to the interposed layer, and in the closely adhesive layer, a closely adhesive layer defect part similar to the defect part in the second thin-film metal layer is formed and a closely adhesive layer flat layer part other than the closely adhesive layer defect part surrounds the closely adhesive layer defect part. 
     The thermally assisted magnetic head has the closely adhesive layer, whereby the adhesion between the near-field light generating layer and the interposed layer increases, and thereby it becomes difficult that the near-field light generating layer exfoliate from the interposed layer. 
     Further, in the above-described thermally assisted magnetic head, it is preferable that the optical waveguide has a waveguide end face arranged within the medium-opposing surface, and extends in a depth direction intersecting the medium-opposing surface from the waveguide end face, and has an upper end face on a side closer to the main magnetic pole layer, the thermally assisted magnetic head further includes an interposed layer which is in direct contact with the upper end face of the optical waveguide, and a closely adhesive layer which makes the near-field light generating layer closely adhere to the interposed layer, and the closely adhesive layer has a net-like structure in which a plurality of closely adhesive layer defect parts similar to the defect parts in the second thin-film metal layer are scattered not in contact with one another and a closely adhesive layer flat layer part other than the closely adhesive layer defect parts surrounds the respective closely adhesive layer defect parts, the closely adhesive layer flat layer part continues without a break due to the closely adhesive layer defect parts. 
     Further, it is possible that the second thin-film metal layer has a quasi-honeycomb structure approximate to a honeycomb structure in which each of the plurality of defect parts is formed in a hexagonal shape. 
     It is possible that the second thin-film metal layer has an annular structure, the annular structure is a structure in which a part of the second thin-film metal layer disposed along an outer peripheral part of it and distanced at an almost regular interval from the outer peripheral part is formed as the flat layer part, and only one defect part is formed inside the flat layer part. 
     Further, it is possible that the closely adhesive layer has an annular structure, the annular structure is a structure in which a part of the closely adhesive layer disposed along an outer peripheral part of it and distanced at an almost regular interval from the outer peripheral part is formed as the closely adhesive layer flat layer part, and only one closely adhesive layer defect part is formed inside the closely adhesive layer flat layer part. 
     It is preferable that the first thin-film metal layer is formed to be smaller in thickness than the second thin-film metal layer. 
     It is preferable that in the near-field light generating layer, the second thin-film metal layer is laminated on the outside most distant from the optical waveguide. 
     Further, in the above-described thermally assisted magnetic head, it is preferable that in the near-field light generating layer, only a near-field light generating part having the generating end part on the magnetic recording medium side has the laminated structure, and a metal component part formed using the first metal is disposed at a part more distant from the medium-opposing surface than is the near-field light generating part. 
     It is also possible that in the near-field light generating layer, a sloping surface sloping with respect to the medium-opposing surface is formed in the near-field light generating part having the generating end part on the magnetic recording medium side. 
     It is also possible that the optical waveguide has a depression formed on the upper end face, and the near-field light generating layer is formed integrally with a metal component part, the metal component part is formed inside the depression using the first metal. 
     Further, the present invention provides a method of manufacturing a thermally assisted magnetic head including a main magnetic pole layer having a magnetic pole end face arranged within a medium-opposing surface opposing a magnetic recording medium; a near-field light generating layer having a generating end part arranged within the medium-opposing surface, the generating end part generating near-field light for heating the magnetic recording medium; and an optical waveguide guiding light to the near-field light generating layer, including a near-field light generating layer forming step of forming the near-field light generating layer, the near-field light generating layer forming step including the following steps (1) to (3): 
     (1) a first metal layer forming step of forming a first metal layer in a thin film form along a direction intersecting the medium-opposing surface 
     (2) a second metal layer forming step of forming, on the first metal layer, a second metal layer in a thin film form along the direction intersecting the medium-opposing surface using a second metal larger in hardness than a first metal forming the first metal layer 
     (3) a metal layer defect step of forming a defect part in the second metal layer, the defect part is a part smaller in thickness than another part or is a hole part, such that a flat layer part other than the defect part surrounds the defect part. 
     In the above-described method of manufacturing, it is preferable that the metal layer defect step is performed such that a plurality of the defect parts are scattered not in contact with one another and the flat layer part surrounds the respective defect parts, and the flat layer part continues without a break due to the defect parts, to make the second metal layer have a net-like structure composed of the plurality of defect parts and the flat layer part. 
     In the above-described method of manufacturing, it is preferable that the method of manufacturing a thermally assisted magnetic head further including an optical waveguide forming step of forming an optical waveguide on a surface of a laminated body to have a rectangular parallelepiped-shape part on a side of a planned opposing surface position which will become the medium-opposing surface afterward; an interposed layer forming step of forming an interposed layer using a dielectric substance on an upper end face of the optical waveguide; a metal thin-film layer forming step of forming a metal thin-film layer which becomes a closely adhesive layer afterward, the closely adhesive layer making the near-field light generating layer closely adhere to the interposed layer; and a closely adhesive layer defect step of forming, in the metal thin-film layer, a closely adhesive layer defect part similar to the defect part in the second metal layer such that a closely adhesive layer flat layer part other than the closely adhesive layer defect part surrounds the closely adhesive layer defect part. 
     Further, it is preferable that the closely adhesive layer defect step is performed such that a plurality of the closely adhesive layer defect parts are scattered not in contact with one another and the closely adhesive layer flat layer part surrounds the respective closely adhesive layer defect parts, and the closely adhesive layer flat layer part continues without a break due to the closely adhesive layer defect parts to make the metal thin-film layer have a net-like structure composed of the plurality of closely adhesive layer defect parts and the closely adhesive layer flat layer part. 
     It is possible that the metal layer defect step is performed such that each of the plurality of defect parts is formed in a hexagonal shape to make the second metal layer have a quasi-honeycomb structure approximate to a honeycomb structure. 
     In case of the above-described method of manufacturing, it is preferable that the second metal layer forming step is performed such that the second metal layer is laminated on the outside most distant from the optical waveguide. 
     Further, the present invention provides a head gimbal assembly including a slider having a thermally assisted magnetic head formed thereon, the thermally assisted magnetic head including a main magnetic pole layer having a magnetic pole end face arranged within a medium-opposing surface opposing a magnetic recording medium; a near-field light generating layer having a generating end part arranged within the medium-opposing surface, the generating end part generating near-field light for heating the magnetic recording medium; and an optical waveguide guiding light to the near-field light generating layer, the near-field light generating layer has a laminated structure in which a first thin-film metal layer formed in a thin film form along a direction intersecting the medium-opposing surface and a second thin-film metal layer formed in a thin film form along the direction intersecting the medium-opposing surface and formed using a second metal larger in hardness than a first metal forming the first thin-film metal layer are alternately laminated, and in the second thin-film metal layer, a defect part is formed, the defect part is a part smaller in thickness than another part or is a hole part, and a flat layer part other than the defect part surrounds the defect part. 
     Further, the present invention provides a hard disk drive including a head gimbal assembly having a thermally assisted magnetic head, and a magnetic recording medium opposing the thermally assisted magnetic head, the thermally assisted magnetic head including a main magnetic pole layer having a magnetic pole end face arranged within a medium-opposing surface opposing the magnetic recording medium; a near-field light generating layer having a generating end part arranged within the medium-opposing surface, the generating end part generating near-field light for heating the magnetic recording medium; and an optical waveguide guiding light to the near-field light generating layer, the near-field light generating layer has a laminated structure in which a first thin-film metal layer formed in a thin film form along a direction intersecting the medium-opposing surface and a second thin-film metal layer formed in a thin film form along the direction intersecting the medium-opposing surface and formed using a second metal larger in hardness than a first metal forming the first thin-film metal layer are alternately laminated, and in the second thin-film metal layer, a defect part is formed, the defect part is a part smaller in thickness than another part or is a hole part, and a flat layer part other than the defect part surrounds the defect part. 
     The present invention will be more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view of the thermally assisted magnetic head in accordance with an embodiment of the present invention taken along the line  1 - 1  of  FIG. 2 , which is a direction intersecting with an air bearing surface (which will hereinafter be referred also to as “ABS”); 
         FIG. 2  is a front view illustrating the ABS of the thermally assisted magnetic head; 
         FIG. 3  is a perspective view illustrating principal parts of a near-field light generating layer, a closely adhesive layer, an interposed layer and an optical waveguide; 
         FIG. 4  is a sectional view of the near-field light generating layer and closely adhesive layer taken along the line  4 - 4  in  FIG. 3 ; 
         FIG. 5  is an exploded perspective view of the near-field light generating layer and closely adhesive layer, which are partially omitted; 
         FIG. 6  is a plan view of a second thin-film metal layer; 
         FIG. 7  is a sectional view taken along the line  7 - 7  in  FIG. 6 ; 
         FIG. 8  is a plan view of the closely adhesive layer; 
         FIG. 9  is a sectional view similar to  FIG. 1 , illustrating principal part of the thermally assisted magnetic head in accordance with an embodiment of the present invention; 
         FIG. 10  is a front view similar to  FIG. 2 , illustrating principal part of the thermally assisted magnetic head in accordance with an embodiment of the present invention; 
         FIG. 11  is a plan view illustrating principal parts of the near-field light generating layer, the interposed layer, the optical waveguide and a heat sink; 
         FIG. 12  is a view illustrating a process of manufacturing the thermally assisted magnetic head in accordance with an embodiment of the present invention, in which (A) is a sectional view corresponding to  FIG. 1 , (B) is a front view corresponding to  FIG. 2 ; 
         FIG. 13  is a view illustrating a process subsequent to that in  FIG. 12 , in which (A) is a sectional view corresponding to  FIG. 1 , (B) is a front view corresponding to  FIG. 2 ; 
         FIG. 14  is a view illustrating a process subsequent to that in  FIG. 13 , in which (A) is a sectional view corresponding to  FIG. 1 , (B) is a front view corresponding to  FIG. 2 ; 
         FIG. 15  is a view illustrating a process subsequent to that in  FIG. 14 , in which (A) is a sectional view corresponding to  FIG. 1 , (B) is a front view corresponding to  FIG. 2 ; 
         FIG. 16  is a view illustrating a process subsequent to that in  FIG. 15 , in which (A) is a sectional view corresponding to  FIG. 1 , (B) is a front view corresponding to  FIG. 2 ; 
         FIG. 17  is a sectional view illustrating a principal part of a process subsequent to that in  FIG. 16  (A); 
         FIG. 18  is a plan view corresponding to  FIG. 17 ; 
         FIG. 19  is a sectional view illustrating a principal part of a process subsequent to that in  FIG. 17 ; 
         FIG. 20  is a plan view corresponding to  FIG. 19 ; 
         FIG. 21  is a sectional view illustrating a principal part of a process subsequent to that in  FIG. 19 ; 
         FIG. 22  is a plan view corresponding to  FIG. 21 ; 
         FIG. 23  is a sectional view illustrating a principal part of a process subsequent to that in  FIG. 21 ; 
         FIG. 24  is a plan view corresponding to  FIG. 23 ; 
         FIG. 25  is a sectional view illustrating a principal part of a process subsequent to that in  FIG. 23 ; 
         FIG. 26  is a plan view corresponding to  FIG. 25 ; 
         FIG. 27  is a perspective view illustrating the near-field light generating layer and closely adhesive layer according to a modified example 1; 
         FIG. 28  is a perspective view illustrating the near-field light generating layer and closely adhesive layer according to a modified example 2; 
         FIG. 29  is a perspective view illustrating principal parts of the near-field light generating layer, the interposed layer and optical waveguide; 
         FIG. 30  is a sectional view of the near-field light generating layer and closely adhesive layer taken along the line  30 - 30  in  FIG. 29 ; 
         FIG. 31  is a perspective view illustrating principal parts of the near-field light generating layer, closely adhesive layer, the interposed layer and optical waveguide; 
         FIG. 32  is a sectional view of the thermally assisted magnetic head, corresponding to  FIG. 9 , having the near-field light generating layer illustrated in  FIG. 31 ; 
         FIG. 33  is a sectional view of the thermally assisted magnetic head, corresponding to  FIG. 9 , having the near-field light generating layer according to a modified example 5; 
         FIG. 34  is a sectional view of the thermally assisted magnetic head, corresponding to  FIG. 9 , having the near-field light generating layer according to another modified example 5; 
         FIG. 35  is a plan view of the second thin-film metal layer according to a modified example 6; 
         FIG. 36  (A) is a plan view illustrating the second thin-film metal layer  180  according to a modified example,  FIG. 36  (B) is a plan view illustrating the second thin-film metal layer  181  according to a modified example; 
         FIG. 37  is a perspective view illustrating the near-field light generating layer and closely adhesive layer according to a modified example 7; 
         FIG. 38  is an exploded perspective view of the near-field light generating layer and closely adhesive layer according to a modified example 7, which are partially omitted; 
         FIG. 39  is an exploded perspective view of the near-field light generating layer and another closely adhesive layer according to a modified example 7, which are partially omitted; 
         FIG. 40  is a perspective view illustrating principal parts of the near-field light generating layer, interposed layer and optical waveguide according to a modified example 8; and 
         FIG. 41  ( a ) is a perspective view illustrating a hard disk drive equipped with a thermally assisted magnetic head in  FIG. 1 ,  FIG. 41  ( b ) is a perspective view illustrating a rear side of HGA. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     In the following, embodiments of the present invention will be described with reference to the drawings. Note that the same components will be referred to with the same numerals or letters, while omitting their overlapping descriptions. 
     (Structures of Thermally Assisted Magnetic Head) 
     To begin with, the structure of a thermally assisted magnetic head will be explained with reference to  FIG. 1  to  FIG. 11 . 
     Here,  FIG. 1  is a sectional view of a thermally assisted magnetic head  100  in accordance with an embodiment of the present invention taken along the line  1 - 1  of  FIG. 2 , which is a direction intersecting with an air bearing surface (which will hereinafter be referred also to as “ABS”), while  FIG. 2  is a front view illustrating an ABS  101  of the thermally assisted magnetic head  100 .  FIG. 3  is a perspective view illustrating principal parts of a near-field light generating layer  28 , a closely adhesive layer  37 , an interposed layer  18  and an optical waveguide  31 .  FIG. 4  is a sectional view of the near-field light generating layer  28  and closely adhesive layer  37  taken along the line  4 - 4  in  FIG. 3 ,  FIG. 5  is an exploded perspective view of the near-field light generating layer  28  and the closely adhesive layer  37 , which are partially omitted. Further,  FIG. 6  is a plan view of a second thin-film metal layer  39 A,  FIG. 7  is a sectional view taken along the line  7 - 7  in  FIG. 6 .  FIG. 8  is a plan view of the closely adhesive layer  37 .  FIG. 9  is a sectional view similar to  FIG. 1 , illustrating principal part of the thermally assisted magnetic head  100 .  FIG. 10  is a front view similar to  FIG. 2 , illustrating principal part of the thermally assisted magnetic head  100 .  FIG. 11  is a plan view illustrating principal parts of the near-field light generating layer  28 , the interposed layer  18 , the optical waveguide  31  and a heat sink  35 . 
     In the thermally assisted magnetic head  100 , the near-field light generating layer  28  has, as illustrated in  FIG. 3  to  FIG. 5 , a laminated structure in which first thin-film metal layers  38  and second thin-film metal layers  39  are alternately laminated. Further, the second thin-film metal layer  39  is formed using a second metal such as Zr, Ru, Ta or the like larger in hardness than the first thin-film metal layer  38 , so that the near-field light generating layer  28  is higher in mechanical strength and less likely to be deformed than a near-field light generating layer (not illustrated) formed using only a first metal such as Au, Ag or the like. In addition, defect parts  58  are formed in the second thin-film metal layer  39  and a flat layer part  59  surrounds the defect parts  58 , whereby the volume of the second metal contained in the near-field light generating layer  28  is reduced, resulting in a reduction of the volume of heat generation in the second thin-film metal layers  39 . Therefore, projection, melting, deformation and recess of the near-field light generating layer  28  is reduced, and deformation, melting, and chipping of a main magnetic pole layer  40  arranged close thereto is also reduced. 
     Note that the right and left direction in  FIG. 2  is the track width direction, the upper direction is the moving direction of a magnetic recording medium, and the direction perpendicular to the paper surface is the direction perpendicular to the surface of the magnetic recording medium. 
     Thermally assisted magnetic head  100  comprises a substrate  1 , reproducing head and recording head laminated on the substrate  1 , while having the ABS  101  as a medium-opposing surface opposing a magnetic recording medium, as illustrated in  FIG. 1 . 
     The following will explain structures of main parts of the thermally assisted magnetic head  100 , while structures of parts other than the main parts will later be explained in manufacturing processes. 
     The reproducing head has an MR device  5 , arranged near the ABS  101 , for detecting a magnetic signal. The reproducing head comprises a lower shield layer  3 , a lower shield gap film  4 , an upper shield gap film  6  and an upper shield layer  7 . 
     An insulating layer  2  is further formed on the substrate  1 , and the lower shield layer  3  made of a magnetic material is formed on the insulating layer  2 . The lower shield gap film  4  as an insulating film is further formed on the lower shield layer  3 , and the upper shield gap film  6  shielding the MR device  5  is formed on the lower shield gap film  4 . The upper shield layer  7  made of a magnetic material is formed on the upper shield gap film  6 , and an insulating layer  8  is formed on the upper shield layer  7 . 
     The MR device  5  is constituted by a magnetosensitive film exhibiting a magnetoresistive effect, such as AMR (anisotropic magnetoresistive), GMR (giant magnetoresistive), and TMR (tunneling magnetoresistive) devices. 
     The GMR device may be of a CIP (Current In Plane) type or a CPP (Current Perpendicular to Plane) type. In the CIP type, current for detecting a magnetic signal flows in a direction almost parallel to planes of the layers constituting the GMR device. In the CPP type, current for detecting a magnetic signal flows in a direction almost perpendicular to planes of the layers constituting the GMR device. 
     Next, the recording head will be explained. The recording head has a lower thin-film coil  11 , a shield magnetic pole layer  20 , the interposed layer  18 , the near-field light generating layer  28 , the optical waveguide  31 , the closely adhesive layer  37 , the main magnetic pole layer  40 , a yoke magnetic pole layer  41 , a linking magnetic pole layer  42  and an upper thin-film coil  51 , and has a structure in which they are stacked on the substrate  1 . 
     The lower thin-film coil  11  has three turn parts. The respective turn parts are insulated from each other by a photoresist  15 . The lower thin-film coil  11  is wound like a flat spiral about the linking magnetic pole layer  42  of the shield magnetic pole layer  20 . 
     The lower thin-film coil  11  is connected to the upper thin-film coil  51 . The upper thin-film coil  51  has also three turn parts. The upper thin-film coil  51  is wound like a flat spiral about the yoke magnetic pole layer  41 . 
     Further, a current modulated according to data to be recorded on the magnetic recording medium flows through the lower thin-film coil  11  and upper thin-film coil  51 , the current causes the lower thin-film coil  11  and upper thin-film coil  51  to generate a recording magnetic field. 
     The shield magnetic pole layer  20  has a shield layer  21 , a connecting magnetic pole layer  22  and a linking magnetic pole layer  23 . 
     The shield layer  21  has an end face arranged within the ABS  101 . The shield layer  21  is junctioned to the connecting magnetic pole layer  22  on a side closer to the ABS  101  than is the lower thin-film coil  11 . 
     The connecting magnetic pole layer  22  has an end face arranged within the ABS  101  and has a part that is more distant from the ABS  101  than is the end face being embedded in the insulating layer  8 . Further, to the connecting magnetic pole layer  22 , the shield layer  21  is junctioned on the side closer to the ABS  101  than is the lower thin-film coil  11 , and the linking magnetic pole layer  23  is junctioned at a position more distant from the ABS  101  than is the three turn parts of the lower thin-film coil  11 . 
     The linking magnetic pole layer  23  is arranged at a position more distant from the ABS  101  than is the three turn parts of the lower thin-film coil  11 , and is junctioned to the connecting magnetic pole layer  22 . 
     The shield magnetic pole layer  20  is provided to return a magnetic flux to the main magnetic pole layer  40 . When a magnetic flux generated by the recording magnetic field is emitted from a later-described magnetic pole end face  40   a  of the main magnetic pole layer  40  to the magnetic recording medium, the magnetic flux flows back to the shield magnetic pole layer  20  via the magnetic recording medium (a not-depicted soft magnetic layer in detail). This magnetic flux passes through the linking magnetic pole layer  23  and reaches the main magnetic pole layer  40 . 
     The interposed layer  18  is in direct contact with an upper end face  31   b  of the optical waveguide  31 . The interposed layer  18  is formed using a dielectric substance having a lower refractive index than that of the optical waveguide  31 , and for example, using alumina (Al 2 O 3 ). The interposed layer  18  has a thickness of, for example, about 10 nm to about 70 nm, which is much smaller than those of the main magnetic pole layer  40  and the optical waveguide  31 , and is thus referred also to as a very-thin interposed layer. Further, the near-field light generating layer  28  is formed on the interposed layer  18  via the closely adhesive layer  37 . 
     The near-field light generating layer  28  has, as illustrated in  FIG. 3  to  FIG. 10 , a first thin-film metal layers  38  and a second thin-film metal layers  39 , and has a laminated structure which the first thin-film metal layers  38  and the second thin-film metal layers  39  are laminated alternatively. Further, the near-field light generating layer  28  has a generating end part  28   a  which generates a near-field light. The generating end part  28   a  is arranged within the ABS  101 . The generating end part  28   a  generates a near-field light for heating the magnetic recording medium. 
     The near-field light generating layer  28  has three first thin-film metal layers  38 A,  38 B,  38 C as the first thin-film metal layers  38  and three second thin-film metal layers  39 A,  39 B,  39 C as the second thin-film metal layers  39 . The second thin-film metal layer  39 A is laminated between the first thin-film metal layers  38 A,  38 B, and the second thin-film metal layer  39 B is laminated between the first thin-film metal layers  38 B,  38 C. Further, in the near-field light generating layer  28 , the second thin-film metal layer  39 C is laminated on the outside most distant from the optical waveguide  31 . 
     Every one of the first thin-film metal layers  38 A,  38 B,  38 C is formed in a thin-film form along a direction intersecting the ABS  101  (a direction perpendicularly intersecting the ABS  101 ), and formed equal in shape and thickness. Every one of the second thin-film metal layers  39 A,  39 B,  39 C is also formed in a thin-film form along the direction intersecting the ABS  101  and formed equal in shape and thickness. 
     The first thin-film metal layers  38 A,  38 B,  38 C are formed using the first metal. The first metal here is a metal having a low resistivity and a high conductivity and can be, for example, any one of Au, Ag, Al, Cu. 
     The second thin-film metal layers  39 A,  39 B,  39 C are formed using the second metal. The second metal is a metal having a hardness (Vickers hardness is assumed in this embodiment but another index may be used) higher than that of the first metal and can be, for example, any one of Ru, Zr, ZrN, Ta, Mo, Pt, Cr, Ni, Fe, Pd, Ti, NiCr, TiW, TiN, Hf. The second metal is higher in mechanical strength than the first metal. Note that when the first metal is a metal other than Cu, Cu can be used as the second metal. 
     Further, the thickness of the first thin-film metal layer  38 A,  38 B,  38 C is, for example, about 5 nm to about 20 nm, whereas the thickness of the second thin-film metal layer  39 A,  39 B,  39 C is, for example, about 0.3 nm to about 5 nm, preferably, about 0.2 nm to about 0.6 nm. Therefore, the second thin-film metal layers  39 A,  39 B,  39 C are formed to be smaller in thickness than the first thin-film metal layers  38 A,  38 B,  38 C. 
     Further, in each of the second thin-film metal layers  39 A,  39 B,  39 C, a plurality (about 10 to 20 in  FIG. 3 ) of defect parts  58  are formed to be scattered not in contact with one another. Each of the defect parts  58  is a part that is smaller in thickness than the other part or is a hole part. The thickness of each defect part  58  is about 0 nm to about 0.2 nm. 
     In every one of the second thin-film metal layers  39 A,  39 B,  39 C, the flat layer part  59  surrounds almost all of the plurality of defect parts  58 . The flat layer part  59  is a part other than the defect parts  58  in each of the second thin-film metal layers  39 A,  39 B,  39 C and is a flat part having a fixed thickness. The flat layer part  59  continues without a break due to the defect parts  58 , so that each of the second thin-film metal layers  39 A,  39 B,  39 C is thus formed as one layer. 
     The second thin-film metal layer  39 A,  39 B,  39 C has a structure like a net-like pattern because of the plurality of defect parts  58  scattered as illustrated in  FIG. 3 . The structure like the net-like pattern is called a net-like structure in this embodiment. 
     Note that since a defect part  58  is arranged at a portion of the peripheral part of the second thin-film metal layer  39 A,  39 B,  39 C in  FIG. 3 , the defect part  58  is far from being surrounded by the flat layer part  59 . However, the whole peripheries of many other defect parts  58  are surrounded by the flat layer part  59 . 
     In  FIG. 3 , the plurality of defect parts  58  in the second thin-film metal layer  39 C are illustrated. The defect parts  58  are scattered in the second thin-film metal layer  39 C and form respective hole parts having no thickness (namely, penetrating from the front side to the rear side). Therefore, the front surface of the first thin-film metal layer  38 C arranged under the defect parts  58  is exposed inside each of the defect parts  58  (dots in  FIG. 3  illustrate the front surface of the first thin-film metal layers  38 C). 
     Every one of the defect parts  58  illustrated in  FIG. 3 ,  FIG. 5  and the like is formed in an approximately oval shape. The defect parts  58  are non-uniform in size and shape and are not unified. An arrangement spot has no regularity and is thus irregular. 
     In the second thin-film metal layers  39 A,  39 B,  39 C, the defect parts  58  are able to be unified in size, shape, arrangement spot, unlike the illustrated case, but may not be unified as in the illustrated case. However, in each of the second thin-film metal layers  39 A,  39 B,  39 C, it is preferable to arrange the defect parts  58  in a manner to evenly disperse them as much as possible without unevenly distributing them at a specific spot, namely, to scatter the plurality of the defect parts  58  as illustrated in  FIG. 3 . 
     The near-field light generating layer  28  closely adheres to the interposed layer  18  with the closely adhesive layer  37 . The closely adhesive layer  37  is formed to make the near-field light generating layer  28  closely adhere to the interposed layer  18  so as to prevent the near-field light generating layer  28  from exfoliating from the interposed layer  18 . 
     The closely adhesive layer  37  has an outer shape in common with the first thin-film metal layer  38 A, the second thin-film metal layer  39 A and the like, and formed in a thin-film form having a thickness of about 0.3 nm to about 1 nm. The closely adhesive layer  37  is formed using, for example, a third metal such as Zr, Ti, Cr, Ta, W. The third metal is known as a closely adhesive material with a property of making the first metal such as Au, Ag or the like closely adhere to alumina (Al 2 O 3 ). 
     As illustrated in  FIG. 5 , a plurality of closely adhesive layer defect parts  88  similar to the defect parts  58  are formed in the closely adhesive layer  37 . The closely adhesive layer defect parts  88  are formed to be scattered not in contact with one another. Also in the closely adhesive layer  37 , a closely adhesive layer flat layer part  89  surrounds almost all of the plurality of closely adhesive layer defect parts  88 . The closely adhesive layer flat layer part  89  is a part other than the closely adhesive layer defect parts  88  of the closely adhesive layer  37  and is a flat part having a fixed thickness. The closely adhesive layer flat layer part  89  continues without a break due to the closely adhesive layer defect parts  88 , so that the closely adhesive layer  37  is formed as one layer. The closely adhesive layer  37  also has a net-like structure because of the plurality of scattered closely adhesive layer defect parts  88 . 
     Note that the closely adhesive layer defect parts  88  can be made similar to the defect parts  58  in size, shape, arrangement spot but may be made different therefrom. 
     On the other hand, a surrounding dielectric substance layer  32  is filled in the surrounding space of the near-field light generating layer  28 , as illustrated in  FIG. 1 ,  FIG. 2 ,  FIG. 9 . The surrounding dielectric substance layer  32  is formed using a dielectric substance such as alumina or the like. 
     Further, the near-field light generating layer  28  has a part whose width along the ABS  101  (lateral width) is fixed, and a part whose width gradually increases as it is distanced more from the ABS  101  (wider part). Further, a heat sink  35  is connected to the wider part. The heat sink  35  is formed of a material having a high thermal conductivity, such as Au, Ag, Al, Cu or the like. 
     The optical waveguide  31  has, as illustrated in  FIG. 3 , the waveguide end face  31   a  arranged within the ABS  101 . Further, the optical waveguide  31  extends from the ABS  101  in a direction perpendicular to the ABS  101  (referred also to as a depth direction), and the optical waveguide  31  is formed to approach from the rear side to the ABS  101  passing through (penetrating) the linking magnetic pole layer  42 . The optical waveguide  31  has the upper end face  31   b  on the main magnetic pole layer  40  side. 
     The optical waveguide  31  is formed using a dielectric substance which transmits laser light, such as Ta 2 O 5  or the like and has a thickness of about 0.4 μm to about 1.5 μm. An optical fiber  208  is connected to the optical waveguide  31 , as illustrated in  FIG. 41 . Laser light generated by a semiconductor laser  207  are inputted to the optical waveguide  31  via the optical fiber  208 . Note that the semiconductor laser  207  and the optical fiber  208  are illustrated in  FIG. 41  (both of them will be described later in detail). 
     Next, the main magnetic pole layer  40  will be explained with reference to  FIG. 1  and  FIG. 2 . The main magnetic pole layer  40  is arranged on an upper side of the near-field light generating layer  28  (side distant from the substrate  1 ). The main magnetic pole layer  40  has a magnetic pole end face  40   a  arranged within the ABS  101 . Further, the main magnetic pole layer  40  opposes to the generating end part  28   a  via a dielectric substance layer  29  within the ABS  101  and is formed to decrease its height along the ABS  101 , as it is distanced more from the ABS  101 . The upper end part of the main magnetic pole layer  40  is a flat surface along the intersecting direction, the yoke magnetic pole layer  41  is connected to the flat surface. 
     Further, the main magnetic pole layer  40  have a symmetrical structure in width direction formed to be bilaterally symmetrical about part thereof opposed to the generating end part  28   a.    
     The yoke magnetic pole layer  41  is arranged in a position recedes from the ABS  101 . The yoke magnetic pole layer  41  is junctioned to a flat upper side part of the main magnetic pole layer  40 . Further, the yoke magnetic pole layer  41  extends along the depth direction, and is connected to the linking magnetic pole layer  42  straddling the upper thin-film coil  51  and the insulating layer  52 . The upper surface of yoke magnetic pole layer  41  (surface of the side distant from the substrate  1 ) is partially formed flat. 
     The linking magnetic pole layer  42  is connected to the yoke magnetic pole layer  41  at a position distant from the ABS  101  than are the three turn parts of the upper thin-film coil  51 . Further, the linking magnetic pole layer  42  is arranged in a manner to hold the optical waveguide  31  and the interposed layer  18  from both right and left sides. 
     The linking magnetic pole layer  42  is a magnetic pole layer magnetically links the shield magnetic pole layer  20  to the yoke magnetic pole layer  41 . The linking magnetic pole layer  42  has a role of returning, to the main magnetic pole layer  40 , the magnetic flux flown back to the shield magnetic pole layer  20 . 
     (Operation Contents of Thermally Assisted Magnetic Head) 
     Subsequently, the magnetic recording operation of the thermally assisted magnetic head having the above structure will be explained as follows. 
     When a current modulated according to data to be recorded on the magnetic recording medium is caused to flow through the lower thin-film coil  11  and upper thin-film coil  51 , the current generates a recording magnetic field. The recording magnetic field passes through the main magnetic pole layer  40 , and a magnetic flux caused by the recording magnetic field is emitted from the magnetic pole end face  40   a  to the magnetic recording medium. With this magnetic flux, the data is recorded on the magnetic recording medium. 
     On the other hand, when the semiconductor laser  207  generates laser light, the laser light are transmitted to the optical waveguide  31  via the optical fiber  208 . The laser light move through the optical waveguide  31  to the ABS  101 . Since the interposed layer  18  is formed so as to cover with the outer face of the optical waveguide  31 , and the near-field light generating layer  28  is formed outside of the interposed layer  18 , the laser light is applied to the near-field light generating layer  28  via the interposed layer  18 . 
     Further, the interposed layer  18  having a lower refractive index than that of optical waveguide  31  is in contact with the optical waveguide  31 . Therefore, when laser light enter the interposed layer  18  having lower refractive index from the optical waveguide  31  having higher refractive index and are totally reflected, evanescent light seeps near the surface of the interposed layer  18  having a lower refractive index. The use of the evanescent light makes it possible to match the phase speed thereof with the phase speed of surface plasmons and excite surface plasmons. 
     The surface plasmons propagate to the generating end part  28   a  of the near-field light generating layer  28 . The surface plasmons are concentrated on the generating end part  28   a . Then, a near-field light having a very high electric field intensity is generated near the generating end part  28   a.    
     The near-field light is applied from the generating end part  28   a  to the magnetic recording medium and reaches the surface of the magnetic recording medium. Then, a limited extremely small region in the magnetic recording layer of the magnetic recording medium is intensively heated by the near-field light. In the magnetic recording layer, the coercive force reduces to an extent at which data is able to be recorded by the magnetic flux caused by the recording magnetic field. 
     In the thermally assisted magnetic head  100 , the coercive force is able to be reduced in the above-descried manner, so that data can be recorded also on a magnetic recording medium having a high coercive force for high-density recording. 
     (Operation and Effect of the Thermally Assisted Magnetic Head) 
     The near-field light generating layer  28  generates the near-field light when the thermally assisted magnetic head  100  performs the above-described magnetic recording operation. 
     Now, a case, where a near-field light generating layer is formed using only Au or Ag as in the conventional thermally assisted magnetic head, is considered. In the near-field light generating layer, a temperature increase occurs accompanying generation of near-field light, thus causing self expansion. 
     Since Au or Ag is particularly higher in coefficient of thermal expansion than other metals, the near-field light generating layer largely expands accompanying the generation of near-field light to project from the ABS when the near-field light generating layer is formed using only Au or Ag. Thus, in the conventional thermally assisted magnetic head, collision with the magnetic recording medium is likely to occur and the hard disk drive is likely to fail. Further, when temperature decreases, the near-field light generating layer shrinks and a front end surface of the near-field light generating layer sometimes recedes from the ABS. In addition, if the heat generated by the near-field light generating layer is conducted to the main magnetic pole layer, the heat may deform or chip a portion on the ABS side of the main magnetic pole layer. 
     On the other hand, since Au or Ag is not so high in melting point as compared with other metals, the near-field light generating layer highly possibly melts or deforms accompanying an increase in temperature. 
     In the thermally assisted magnetic head  100  according to the embodiment of the present invention, however, the near-field light generating layer  28  has the above-described laminated structure and the defect parts  58  and the flat layer part  59  are formed in the second thin-film metal layer  39 , so that the operation and effect described below can be provided to solve the above problems. 
     First, in the near-field light generating layer  28 , the first thin-film metal layer  38  is formed using the first metal such as Au, Ag, Al, Cu or the like as in the conventional near-field light generating layer, whereas the second thin-film metal layer  39  is formed using the second metal. The second metal is composed of Ru, Zr, Pt, Pd, ZrN or the like which is higher in hardness (Vickers hardness) and mechanical strength than the first metal, and so the second metal is higher in stiffness. 
     For this reason, the second thin-film metal layer  39  is less likely to be deformed than the first thin-film metal layer  38 . The second thin-film metal layer  39  is included in the near-field light generating layer  28 , so that the near-field light generating layer  28  increases in mechanical strength as a whole. 
     Furthermore, the second thin-film metal layers  39  and the first thin-film metal layers  38  are alternately laminated and are in direct contact with each other, so that even if the first thin-film metal layer  38  tries to deform, the second thin-film metal layer  39  displays an operation of stopping the deformation. This makes it possible to suppress as much as possible the deformation of the near-field light generating layer  28  due to its own heat generation and to prevent as much as possible the projection thereof from the ABS  101 . 
     Further, even if the second thin-film metal layer  39  is included in the near-field light generating layer  28 , the first thin-film metal layer  38  high in electric conductivity is included in the near-field light generating layer  28  and can thus make the near-field light generating layer  28  efficiently generate near-field light. 
     The second metal (for example, Zr), however, is higher in hardness than the first metal (for example, Au) but lower in thermal conductivity than the first metal (for example, Au). Therefore, the second metal (for example, Zr) is less likely to conduct heat to the outside than the first metal. Accordingly, the second thin-film metal layer  39  is more likely to accumulate heat inside thereof than the first thin-film metal layer  38 . 
     When the second thin-film metal layer  39  is included in part of the near-field light generating layer  28 , the near-field light generating layer  28  will generate more heat, as a whole, than the conventional near-field light generating layer including no second metal. 
     When the near-field light generating layer  28  generates more heat, surface plasmons excited thereby will decrease. To compensate for the decrease, the output of the semiconductor laser  207  needs to be increased. Then, laser light with higher energy is guided into the near-field light generating layer  28 , resulting in an increase in heat generation by the near-field light generating layer  28 . 
     To improve such a situation, in the thermally assisted magnetic head  100  according to the embodiment of the present invention, the defect parts  58  and the flat layer part  59  are formed in the second thin-film metal layer  39  constituting the near-field light generating layer  28 . 
     As has been described above, the defect parts  58  are parts that are smaller in thickness than the other part or are hole parts. Therefore, the defect parts  58  are formed in the second thin-film metal layer  39 , whereby the volume of the second metal contained in the near-field light generating layer  28  is smaller than that in the case of not including the defect parts  58 . When the second metal lower in thermal conductivity than the first metal is decreased in volume, the heat remaining in the second thin-film metal layer  39  is accordingly decreased, whereby the volume of heat generation in the near-field light generating layer  28  is able to be reduced as a whole. 
     Accordingly, the near-field light generating layer  28  can be prevented from melting, deforming, and projecting from the ABS  101  due to its own heat generation. 
     This eliminates the situation in which the generating end part  28   a  melts and deforms, and therefore the generating end part  28   a  is able to heat surely the very small recording region of the magnetic recording medium. Therefore a reliability of the thermally assisted magnetic head  100  is able to be increased. 
     Further, in the thermally assisted magnetic head  100 , the main magnetic pole layer  40  is arranged very near the near-field light generating layer  28 , and the heat generated at the near-field light generating layer  28  unlikely to reach the main magnetic pole layer  40 . Therefore, chipping and deformation of the main magnetic pole layer  40  are also able to be effectively prevented. 
     On the other hand, when the defect parts  58  are not formed in the second thin-film metal layer  39 , the second thin-film metal layer  39  comes to be in contact with the entire front surface and rear surface of the first thin-film metal layer  38 , thereby possibly decreasing the generation efficiency of the near-field light. 
     However, since the defect parts  58  are formed in the second thin-film metal layer  39 , the portion of the first thin-film metal layer  38  with which the second thin-film metal layer  39  comes into contact is smaller than that in the case where the defect parts  58  are not formed. Accordingly, the near-field light generating layer  28  is configured such that it does not decrease so much in generation efficiency of the near-field light though it includes the second thin-film metal layer  39 . 
     Further, the thermally assisted magnetic head  100  is able to prevent a situation that the near-field light generating layer  28  projects from the ABS  101 , and thus is able to prevent failure of the hard disk drive. 
     On the other hand, in the second thin-film metal layer  39 , the peripheries of the plurality of defect parts  58  are surrounded by the flat layer part  59 . Therefore, in the near-field light generating layer  28 , the volume of the second metal is reduced while the mechanical strength of the second thin-film metal layer  39  is substantially maintained as a whole. 
     Especially, the near-field light generating layer  28  has the net-like structure in which the flat layer part  59  continues without a break and the defect parts  58  are arranged in balanced manner as a whole in the second thin-film metal layer  39 . Therefore, the second thin-film metal layer  39  is one thin film though the volume of the second metal is small. Accordingly, the second thin-film metal layer  39  can maintain its outer shape as a whole even if external force is applied thereto from any direction. 
     If the flat layer part  59  is broken by the defect parts  58 , for example, if the flat layer part  59  is divided into two parts by the defect parts  58 , the second thin-film metal layer  39  may become difficult to maintain its outer shape depending on the direction in which the external force is applied thereto. Then, the function of stopping the deformation of the first thin-film metal layer  38  by the second thin-film metal layer  39  decreases to make it also difficult to prevent deformation and the like of the near-field light generating layer  28  due to its own heat generation. 
     Hence, the near-field light generating layer  28  is made such that the second thin-film metal layer  39  is formed in the net-like structure in which the flat layer part  59  continues without a break due to the defect parts  58  so that the second thin-film metal layer  39  can maintain its outer shape as a whole. 
     In addition, in the near-field light generating layer  28 , at least two second thin-film metal layers  39  are laminated and the first thin-film metal layer  38  is laminated between them. Therefore, the near-field light generating layer  28  has a structure in which the first thin-film metal layer  38  which is comparatively soft, is covered from the outside by the second thin-film metal layers  39  which are high in mechanical strength. Accordingly, the mechanical strength of the near-field light generating layer  28  can be made higher as a whole. 
     Further, the second thin-film metal layer  39  has the net-like structure by the plurality of defect parts  58 , and the defect parts  58  are substantially evenly arranged without being unevenly distributed at a portion in the second thin-film metal layer  39 . Therefore, there is no part that is relatively low in mechanical strength in second thin-film metal layer  39 . Even if the volume of the second metal is reduced, the mechanical strength of the second thin-film metal layer  39  is maintained as a whole. 
     Furthermore, the near-field light generating layer  28  is formed on the interposed layer  18  via the closely adhesive layer  37  so as to avoid such a situation that the near-field light generating layer  28  exfoliates from them. The closely adhesive layer  37  is formed using the third metal and is formed also with the closely adhesive layer defect parts  88  and the closely adhesive layer flat layer part  89 . Therefore, the volume of the closely adhesive layer  37  is also reduced while the mechanical strength is maintained as a whole. Accordingly, since accumulation of heat in the closely adhesive layer  37  is also suppressed, the heat conducted from the closely adhesive layer  37  to the near-field light generating layer  28  is reduced. 
     Further, since the second thin-film metal layer  39  is formed to be smaller in thickness than the first thin-film metal layer  38 , the proportion of the second thin-film metal layer  39  with a lower thermal conductivity in the near-field light generating layer  28  is able to be decreased. This makes it possible to reduce the volume of heat generation in the near-field light generating layer  28  as a whole. 
     In the near-field light generating layer  28 , the second thin-film metal layer  39 C is laminated on the outside most distant from the optical waveguide  31 . If the second thin-film metal layer  39 C is not laminated, the second thin-film metal layer in contact with the outside of the first thin-film metal layer  38 C no longer exists, and the function of stopping the deformation of the first thin-film metal layer  38 C possibly decreases. However, since the second thin-film metal layer  39 C is laminated in the near-field light generating layer  28 , there is no such possibility. 
     (Method of Manufacturing Thermally Assisted Magnetic Head) 
     Next, a method of manufacturing the thermally assisted magnetic head  100  having the structure mentioned above will now be explained with reference to  FIG. 12  (A), (B) to  FIG. 16  (A), (B) and  FIG. 17  to  FIG. 26  together with  FIG. 1  and  FIG. 2  mentioned above. 
     Here,  FIG. 12(A)  to  FIG. 16(A)  are sectional views corresponding to  FIG. 1  in the processes of manufacturing the thermally assisted magnetic head  100 , and  FIG. 12(B)  to  FIG. 16(B)  are front views corresponding to  FIG. 2  in the processes of manufacturing the thermally assisted magnetic head  100 . In each drawing, the left end face in (A) indicates a position (a planned opposing surface position) which will become the ABS  101  afterward. Further,  FIG. 17 ,  19 ,  21 ,  23 ,  25  are sectional views illustrating principal part in the subsequent processes of  FIG. 16  (A) in order.  FIG. 18 ,  20 ,  22 ,  24 ,  26  are plan views corresponding to  FIG. 17 ,  19 ,  21 ,  23 ,  25  respectively. 
     First, the substrate  1  made of a ceramic material such as aluminum oxide-titanium carbide (Al 2 O 3 .TiC) is prepared. Subsequently, as shown in  FIG. 12  (A), (B), the insulating layer  2  made of an insulating material such as alumina (Al 2 O 3 ), the lower shield layer  3  made of a magnetic material and the lower shield gap film  4  are successively laminated on the substrate  1 . 
     Next, the upper shield gap film  6  is formed by an insulating material such as to shield the MR device  5 . Here, an undepicted lead connected to the MR device  5  is formed, and the MR device  5  and lead are covered with the upper shield gap film  6 . Thereafter, using a magnetic material, the upper shield layer  7  is formed on the upper shield gap film  6 . 
     Then, on the upper shield layer  7 , the insulating layer  8  is formed using an insulating material such as alumina (Al 2 O 3 ) or the like. Thereafter, a portion of the insulating layer  8  which is located on the planned opposing surface position side is removed, and the connecting magnetic pole layer  22  is formed using a magnetic material such as CoNiFe, CoFe, NiFe, CoFeN or the like. 
     Then, as illustrated in  FIG. 13(A) , (B), an insulating layer  14  is formed on the whole surface of the laminated body using an insulating material such as alumina (Al 2 O 3 ) or the like, and parts of the insulating layer  14 , that the shield layer  21  and the linking magnetic pole layer  23  are formed, are removed. 
     Then, the shield layer  21  and the linking magnetic pole layer  23  are formed at the opened parts of the insulating layer  14  in the surface of the laminated body, for example, by the frame plating method. 
     Next, as illustrated in  FIG. 14(A) ,  FIG. 14(B) , an insulating layer  16  (having a thickness of about 0.02 μm to 0.3 μm, preferably about 0.1 μm to 0.2 μm) made of alumina (Al 2 O 3 ) is formed on the whole surface of the laminated body by CVD (Chemical Vapor Deposition) according to an atomic layer method. The insulating layer  16  is formed so as to cover the shield layer  21  and the linking magnetic pole layer  23 . 
     Then, a conductor layer for forming the lower thin-film coil  11  is formed between the shield layer  21  and the linking magnetic pole layer  23  by the frame plating method. Next, a photoresist layer  91  (having a thickness of about 1.5 μm to 2.5 μm) is formed so as to fill up the interstice part of the conductor layer. Next, an insulating film  26  adapted to cover the surface of the laminated body is formed using alumina (Al 2 O 3 ) by a thickness of about 3 μm to 4 μm. Subsequently, the surface of the laminated body is polished by CMP until the shield layer  21  and the linking magnetic pole layer  23  emerge, so as to become flat. 
     Then, as illustrated in  FIG. 15(A) , (B), flattening step of the shield layer  21  and the linking magnetic pole layer  23  together with the conductor layer is performed. By this, the lower thin-film coil  11  and the photoresist  15  are formed. 
     Subsequently, as illustrated in  FIG. 16(A) , (B), an insulating layer  17  adapted to cover the surface of the laminated body is formed using alumina (Al 2 O 3 ). Then, an optical waveguide forming step is performed. In this step, the optical waveguide  31  is formed on the surface of the laminated body, as illustrated in  FIG. 1 . The optical waveguide  31  is formed using a dielectric substance such as Ta 2 O 5  or the like transmitting the laser light. The optical waveguide  31  is formed to have a rectangular parallelepiped-shape part on the planned opposing surface position side. 
     Next, a first dielectric substance layer forming step is performed. In this step, a dielectric substance layer  19  is formed on the surface of the laminated body, using a dielectric substance such as alumina or the like. 
     Subsequently, a flattening step is performed. In this step, the surface of the laminated body is polished by chemical mechanical polishing (hereinafter, referred to as “CMP”) until a surface of the optical waveguide  31  emerges, so as to be made flat. 
     Next, an interposed layer forming step is performed. In this step, the interposed layer  18  is formed on the whole surface of the laminated body, including the upper end face  31   b  of the optical waveguide  31 , for example, by the atomic layer deposition, using a dielectric substance such as alumina or the like. 
     Next, a metal thin-film layer forming step and a closely adhesive layer defect step are performed. A metal thin-film layer  65  which becomes the closely adhesive layer afterward is formed in the metal thin-film layer forming step, as illustrated in  FIG. 17 ,  18 . This metal thin-film layer  65  is able to be formed with the above-described third metal by sputtering, for example. 
     Subsequent to the metal thin-film layer forming step, the closely adhesive layer defect step is performed. In this step, the plurality of closely adhesive layer defect parts  88  are formed in the metal thin-film layer  65  as illustrated in  FIG. 19 ,  FIG. 20 . In this case, the closely adhesive layer defect parts  88  are formed such that the closely adhesive layer flat layer part  89  surrounds the plurality of closely adhesive layer defect parts  88  respectively and the closely adhesive layer flat layer part  89  continues without a break. Thus, the closely adhesive layer defect step is performed so that the metal thin-film layer  65  has the above-described net-like structure and will become the closely adhesive layer  37  afterward. 
     The closely adhesive layer defect step can be performed, for example, by the electron beam irradiation method. The electron beam irradiation method is performed as follows. First, electrons are generated in vacuum and accelerated. Then, the group of the electrons are focused into a thin flux of high energy using a not-illustrated electromagnetic lens and applied to a workpiece. This instantaneously melts the irradiated part and vaporizes and removes it. 
     The above electron beam irradiation method is used to remove portions of the metal thin-film layer  65  to form the plurality of closely adhesive layer defect parts  88 . In this case, the plurality of closely adhesive layer defect parts  88  are formed not to be uneven in size, shape and arrangement spot. 
     Subsequently, the near-field light generating layer  28  is formed by performing a near-field light generating layer forming step. This near-field light generating layer forming step has a first metal layer forming step, a second metal layer forming step and a metal layer defect step. 
     To begin with, a first metal layer forming step is performed. In this first metal layer forming step, a first metal layer  66  having thin-film like form is formed, as illustrated in  FIG. 21 ,  FIG. 22 . The first metal layer  66  is formed along the direction intersecting the ABS  101 , and it becomes the first thin-film metal layer  38 A afterward. The first metal layer  66  is able to be formed with the above-described first metal for example, by sputtering. 
     Subsequently, a second metal layer forming step is performed. In this second metal layer forming step, a second metal layer  67  having thin-film like form is formed on the first metal layer  66 , as illustrated in  FIG. 23 ,  FIG. 24 . The second metal layer  67  is formed along the direction intersecting the ABS  101 , and it becomes the second thin-film metal layer  39 A afterward. The second metal layer  67  is able to be formed with the above-described second metal for example, by sputtering. 
     Thereafter, the metal layer defect step is performed on the second metal layer  67 . In the metal layer defect step, the plurality of defect parts  58  are formed in the second metal layer  67  as illustrated in  FIG. 23 ,  FIG. 24 . In this case, the defect parts  58  are formed such that the flat layer part  59  surrounds the plurality of defect parts  58  respectively and the flat layer part  59  continues without a break. Thus, the metal layer defect step is performed so that the second metal layer  67  has the net-like structure composed of the plurality of defect parts  58  and the flat layer part  59 . The metal layer defect step can be performed, for example, by the electron beam irradiation method as in the closely adhesive layer defect step. 
     Next, the first metal layer forming step is performed again. In this step, a first metal layer  68  having thin-film like form is formed, as illustrated in  FIG. 25 ,  FIG. 26 . The first metal layer  68  will become the first thin-film metal layer  38 B afterward. 
     Thereafter, the second metal layer forming step is performed to form a second metal layer  69  which will become the second thin-film metal layer  39 B afterward. Subsequently, the metal layer defect step is performed on the second metal layer  69  to form the plurality of defect parts  58 . Further, the first metal layer forming step is performed again to form a first metal layer  70  which will become the first thin-film metal layer  38 C afterward. Thereafter, the second metal layer forming step is performed again to form a second metal layer  71  which will become the second thin-film metal layer  39 C afterward. By forming the second metal layer  71 , the second metal layer forming step is performed such that the second metal layer  71  is laminated on the outside most distant from the optical waveguide  31 . Then, the metal layer defect step is performed on the second metal layer  71  to form the plurality of defect parts  58 . Thus, a metal laminated part  72  which will become the near-field light generating layer  28  afterward is formed. 
     Next, a photomask is formed on the metal laminated part  72  using a photoresist and then, for example, RIE or ion beam etching is performed using the photomask to pattern the metal laminated part  72 . By removing an unnecessary portion of the metal laminated part  72  in this manner, the above-described near-field light generating layer  28  is formed. 
     Next, as illustrated in  FIG. 1 , the surrounding insulating layer  32  is formed using an insulating material such as alumina (Al 2 O 3 ) or the like on the surface of the laminated body. Subsequently, the surface of the laminated body is polished by CMP until the surface of the near-field light generating layer  28  emerges. 
     Subsequently, the heat sink  35  is formed so as to cover a part of the near-field light generating layer  28  and a part of the surrounding insulating layer  32 . 
     Next, an insulating layer  33  is formed so as to cover the heat sink  35 . Next, an insulating layer  29  is formed so as to cover the insulating layer  33 . After that, etching is performed selectively to the interposed layer  18  and the insulating layers  32 ,  33 ,  29 . 
     Next, the main magnetic pole layer  40  is formed on the ABS  101  side of the insulating layer  29 , and the linking magnetic pole layer  42  is formed on a part distanced from the ABS  101 . 
     After that, an insulating layer  49  is formed on the whole surface of the laminated body. The surface of the laminated body is polished by CMP afterward, until the surfaces of the main magnetic pole layer  40  and the linking magnetic pole layer  42  emerge. Furthermore, the upper thin-film coil  51  is formed on the insulating layer  49 . After that, an insulating layer  52  is formed so as to cover the upper thin-film coil  51 . 
     Then, the yoke magnetic pole layer  41  is formed so as to cover the main magnetic pole layer  40 , the linking magnetic pole layer  42  and the insulating layer  52 . After that, a protective insulating layer  60  is formed on the surface of the laminated body so as to cover the yoke magnetic pole layer  41 . After that, the thermally assisted magnetic head  100  having the above-described structure is manufactured by being formed the ABS  101 . 
     Modified Example 1 
     Successively, the near-field light generating layer  128  in accordance with modified example illustrated in  FIG. 27  will be explained.  FIG. 27  is a perspective view illustrating the near-field light generating layer  128  and closely adhesive layer  37  according to a modified example. The near-field light generating layer  128  is different in that it has second thin-film metal layers  139  ( 139 A,  139 B,  139 C) in place of the second thin-film metal layers  39  ( 39 A,  39 B,  39 C), as compared with the near-field light generating layer  28 . 
     The respective second thin-film metal layers  139 A,  139 B,  139 C are different in that a plurality of defect parts  158  are formed in place of the plurality of defect parts  58  as compared with the respective second thin-film metal layers  39 A,  39 B,  39 C. 
     In the case of the above-described near-field light generating layer  28 , every one of the plurality of defect parts  58  is formed in an approximately oval shape but non-uniform in size and shape, and thus has no regularity in arrangement spot. 
     In contrast to the above, every one of the plurality of defect parts  158  is formed in a hexagonal shape and their size are also unified except for a part of them. Further, the vertical and lateral intervals thereof are unified and the directions in which they are arranged are also unified. The number of arranged defect parts  158  regularly changes to be one, two, three, four toward the direction more distant from the ABS  101  side so that the defect parts  158  have regularity also in arrangement spot. 
     By forming the plurality of defect parts  158 , the second thin-film metal layer  139 A,  139 B,  139 C has a structure approximate to the honeycomb structure (also referred to as a quasi-honeycomb structure). 
     Generally, the honeycomb structure is a structure in which regular hexagons are arranged without gap therebetween, and is known as a structure which can maintain the strength of the member formed with the structure while reducing its volume. The second thin-film metal layer  139 A,  139 B,  139 C has the quasi-honeycomb structure approximate to the honeycomb structure, so that the volume of the material constituting the respective second thin-film metal layer, namely, the second metal can be reduced even though it can maintain the strength. 
     Accordingly, since the volume of the second metal is reduced, the volume of heat generation can further be suppressed in the near-field light generating layer  128 , and it can be more efficiently prevented from melting, deforming, and projecting due to heat generation. 
     Modified Example 2 
     Next, the near-field light generating layer  148  in accordance with modified example illustrated in  FIG. 28  will be explained.  FIG. 28  is a perspective view illustrating the near-field light generating layer  148  and closely adhesive layer  37 . The near-field light generating layer  148  is different in that it has first thin-film metal layers  138  ( 38 A,  38 B,  138 C) in place of the first thin-film metal layers  38  ( 38 A,  38 B,  38 C), and it has second thin-film metal layers  140  ( 139 A,  139 B,  140 C) in place of the second thin-film metal layers  139  ( 139 A,  139 B,  139 C) as compared with the above-described near-field light generating layer  128 . 
     The first thin-film metal layers  138  are different in that they have a first thin-film metal layer  138 C in place of the first thin-film metal layer  38 C as compared with the first thin-film metal layers  38 . The first thin-film metal layer  138 C is different in that a sloping surface  138 Ca is formed on the ABS  101  side as compared with the first thin-film metal layer  38 C. 
     The second thin-film metal layers  140  are different in that they have second thin-film metal layer  140 C in place of the second thin-film metal layer  139 C. The second thin-film metal layer  140 C is different in that a sloping surface  140 Ca is formed on the ABS  101  side as compared with the second thin-film metal layer  139 C. 
     In the near-field light generating layer  148 , the second thin-film metal layers  139 A,  139 B,  140 C have the quasi-honeycomb structure as in the near-field light generating layer  128 , so that the volume of the second metal constituting the respective second thin-film metal layer can be reduced even though it can maintain the strength. Accordingly, the near-field light generating layer  148  can also suppress its own volume of heat generation and can be more efficiently prevented from melting, deforming, and projecting due to heat generation as with the near-field light generating layer  128 . 
     To efficiently generate the near-field light by the near-field light generating layer  128 , it is desirable to have the plurality of first thin-film metal layers  38 A,  38 B,  38 C which are formed to be large in thickness as in the near-field light generating layer  128 . 
     This, however, increases the thickness of the near-field light generating layer  128  as a whole, so that the near-field light generating layer  128  exposed to the ABS  101  may increase in height. This makes it difficult to keep the height of the near-field light generating layer  128  exposed to the ABS  101  in a fixed size. 
     In this case, it is desirable to form sloping surfaces like the sloping surfaces  138 Ca,  140 Ca on the ABS  101  side as in the near-field light generating layer  148 . Formation of the sloping surfaces like the sloping surfaces  138 Ca,  140 Ca makes it possible to keep the height of the near-field light generating layer  148  exposed to the ABS  101  in a fixed size while the near-field light generating layer  148  is made large in height. 
     Modified Example 3 
     Further, in the thermally assisted magnetic head  100  in accordance with an embodiment of the present invention, a near-field light generating layer  149  illustrated in  FIG. 29 ,  FIG. 30  may be formed in place of the near-field light generating layer  28 . 
     The near-field light generating layer  149  is different in that it has a protective layer  141  in place of the second thin-film metal layer  39 C as compared with the above-described near-field light generating layer  28 . The protective layer  141  is a layer for preventing a material constituting the first thin-film metal layer  38 C from diffusing. The protective layer  141  is formed of a dielectric substance. The protective layer  141  is able to form with either one of SiO 2 , alumina, MgO, ZrO 2 , Amorphous SiC for example. 
     The protective layer  141  is not formed with the plurality of defect parts  58  unlike the second thin-film metal layer  39 C, but the near-field light generating layer  149  has the second thin-film metal layers  39 A,  39 B each having the plurality of defect parts  58  and the flat layer part  59 . Accordingly, the near-field light generating layer  149  is also able to suppress its own volume of heat generation and is able to be prevented from melting, deforming, and projecting due to heat generation. 
     Modified Example 4 
     Further, in the thermally assisted magnetic head  100  in accordance with an embodiment of the present invention, a near-field light generating layer  151  illustrated in  FIG. 31  to  FIG. 32  may be formed in place of the near-field light generating layer  149 . 
     The near-field light generating layer  151  is different in that it has a metal component part  150  as compared with the above-described near-field light generating layer  149 . The metal component part  150  is disposed at a part distanced from the ABS  101 , in the first thin-film metal layers  38 B,  38 C and second thin-film metal layers  39 A,  39 B. The metal component part  150  is formed of the first metal. The second thin-film metal layers  39 A,  39 B made of the second metal are arranged on the ABS  101  side of the near-field light generating layer  151 . Therefore, in the near-field light generating layer  151 , mechanical strength is able to increase in a part which influence due to melting and deformation likely to occur, and prevent from deforming and projecting. 
     Further, the volume of the second metal in the near-field light generating layer  151  is reduced as compared with that in the near-field light generating layer  149  because the metal component part  150  is disposed. In addition to that, the second thin-film metal layer  39 A,  39 B have the net-like structure to further reduce the volume of the second metal contained in the near-field light generating layer  151 . 
     Modified Example 5 
     Further, in the thermally assisted magnetic head  100  in accordance with an embodiment of the present invention, a near-field light generating layer  152  illustrated in  FIG. 33  may be formed in place of the near-field light generating layer  28 . 
     The near-field light generating layer  152  is different in that it has a metal component part  160  as compared with the above-described near-field light generating layer  28 . The metal component part  160  is formed with the above-described first metal. The metal component part  160  is formed in a depression  31   c  of the optical waveguide  31 . The depression  31   c  is formed on the upper end face  31   b  of the optical waveguide  31 . The interposed layer  18  is inserted in the depression  31   c , and the metal component part  160  is formed on the interposed layer  18 . The metal component part  160  is connected to the first thin-film metal layer  38  ( 38 A) on the substrate  1  side of the near-field light generating layer  152 . 
     The near-field light generating layer  152  has the metal component part  160  and is thus high in electric conductivity as a whole but is likely to be low in mechanical strength as a whole because the metal component part  160  is formed using the first metal. 
     The near-field light generating layer  152  has, however, the second thin-film metal layers  39 A,  39 B,  39 C and thus can be prevented from being reduced in mechanical strength. In addition, since each of them has the net-like structure, the volume of the second metal contained in the near-field light generating layer  152  can be reduced. Accordingly, the near-field light generating layer  152  can also be prevented from melting, deforming, and projecting from the ABS  101  due to its own heat generation. 
     Note that a dielectric substance layer  131  may be formed on the upper end face  31   b  side of the optical waveguide  31 , as illustrated in  FIG. 34 . The dielectric substance layer  131  is formed on the upper end face  31   b . A depression may be formed in the dielectric substance layer  131 , and the metal component part  160  may be formed in the depression. 
     Modified Example 6 
     Furthermore, the near-field light generating layer  28  may have a second thin-film metal layer  170  as illustrated in  FIG. 35 , in place of the second thin-film metal layer  39 . A plurality of defect parts  168  and a flat layer part  169  are formed in the second thin-film metal layer  170 . The respective defect parts  168  are formed rectangular shape having equal size. Further, an interval in every direction is unified, and an arrangement direction is also unified, about respective defect parts  168 . An arrangement spot has also regularity. 
     The second thin-film metal layer  170  can maintain its strength while reducing the volume of the second metal, and thus can provide the same operation and effect as those of the second thin-film metal layer  39 . 
     Besides, the near-field light generating layer  28  may have second thin-film metal layer  180  as illustrated in  FIG. 36  (A), in place of the second thin-film metal layer  39 . Further, the near-field light generating layer  28  may have second thin-film metal layer  181  as illustrated in  FIG. 36  (B). 
     A defect part  178  having approximately oval shape is formed at the almost center of the second thin-film metal layer  180 , and a flat layer part  179  is formed so as to surround the defect part  178 . Three defect parts  188  having approximately oval shape are formed in the second thin-film metal layer  181 , and a flat layer part  189  is formed so as to surround the respective defect parts  188 . 
     Modified Example 7 
     Next, a near-field light generating layer  228  and closely adhesive layer  237  in accordance with modified example illustrated in  FIG. 37 ,  38  will be explained.  FIG. 37  is a perspective view illustrating the near-field light generating layer  228  and closely adhesive layer  237 .  FIG. 38  is an exploded perspective view of the near-field light generating layer  228  and closely adhesive layer  237 , which are partially omitted. 
     The near-field light generating layer  228  is different in that it has second thin-film metal layers  239  ( 239 A,  239 B,  239 C) in place of the second thin-film metal layers  39  ( 39 A,  39 B,  39 C) as compared with the above-described near-field light generating layer  28 . 
     The second thin-film metal layers  239  ( 239 A,  239 B,  239 C) are different in that any one of them have one defect part  258  and flat layer part  259  in place of the plurality of defect parts  58  and flat layer part  59 , as compared with the second thin-film metal layers  39  ( 39 A,  39 B,  39 C). Only one the defect part  258  is formed inside of the flat layer part  259 . The flat layer part  259  is formed along an outer peripheral part  239 E of the second thin-film metal layers  239 . The flat layer part  259  has a narrow band shape of a part, distanced from the outer peripheral part  239 E at an almost regular interval. 
     Since the flat layer part  259  is formed in an annular shape trimming narrowly the outside of one defect part  258  as in the illustration, the second thin-film metal layer  239  has an annular structure composed of the defect part  258  and the flat layer part  259 . 
     In the second thin-film metal layer  239 , since the flat layer part  259  is formed along the outer peripheral part  239 E which is sensitive to deformation, the volume of the second metal contained in the near-field light generating layer  228  can be reduced while the reduction in mechanical strength is prevented. Accordingly, the near-field light generating layer  228  can also be prevented from melting, deforming, and projecting from the ABS  101  due to its own heat generation. 
     Further, the closely adhesive layer  237  is different in that it has one closely adhesive layer defect part  268  and one closely adhesive layer flat layer part  269  in place of the plurality of closely adhesive layer defect parts  88  and the closely adhesive layer flat layer part  89 , as compared with the closely adhesive layer  37 . Only one closely adhesive layer defect part  268  is formed inside the closely adhesive layer flat layer part  269 . The closely adhesive layer flat layer part  269  is formed in the same narrow band shape as that of the flat layer part  259 . The closely adhesive layer  237  has the same annular structure as that of the second thin-film metal layer  239 . The volume of the closely adhesive layer  237  is also reduced while the mechanical strength is maintained as a whole. 
     Further, a closely adhesive layer  247  illustrated in  FIG. 39  may be formed in place of the closely adhesive layer  237 , about the near-field light generating layer  228 . The closely adhesive layer  247  has a closely adhesive layer defect part  278  and a closely adhesive layer flat layer part  279 . Though the closely adhesive layer flat layer part  279  is formed by narrow band shape similar to the closely adhesive layer flat layer part  269 , a part of the closely adhesive layer flat layer part  279  near the ABS  101  is divided. The volume of the closely adhesive layer  247  is also reduced while the mechanical strength is maintained as a whole. 
     Since the part of closely adhesive layer  247  near the ABS  101  is divided, the size of the closely adhesive layer  247  being in contact with the near-field light generating layer  228  is small, as compared with closely adhesive layer  237 . Accordingly, the near-field light is generated effectively by using the closely adhesive layer  247  than the closely adhesive layer  237 . 
     Modified Example 8 
     Furthermore, in the thermally assisted magnetic head  100  in accordance with an embodiment of the present invention, a near-field light generating layer  153  illustrated in  FIG. 40  may be formed in place of the near-field light generating layer  28 . 
     The near-field light generating layer  153  is different in that it has a second thin-film metal layer  99  in place of the second thin-film metal layers  39 C, as compared with the above-described near-field light generating layer  149 . The second thin-film metal layer  99  is different in that it has a second thin-film metal layer  39 D in place of the second thin-film metal layer  39 A, as compared with the second thin-film metal layer  39 . A depth from the ABS  101  about the second thin-film metal layer  39 D is small than that of the second thin-film metal layer  39 A. 
     (Embodiments of Head Gimbal Assembly and Hard Disk Drive) 
     Next, embodiments of the head gimbal assembly and hard disk drive will now be explained with reference to  FIG. 41 . 
       FIG. 41  ( a ) is a perspective view showing a hard disk drive  201  equipped with the above-mentioned thermally assisted magnetic head  100 . The hard disk drive  201  includes a hard disk (magnetic recording medium)  202  rotating at a high speed and a head gimbal assembly (HGA)  210 . The hard disk drive  201  is an apparatus which actuates the HGA  210 , so as to record/reproduce data onto/from recording surfaces of the hard disk  202 . The hard disk  202  has a plurality of (4 in the drawing) platters. Each platter has a recording surface opposing its corresponding thermally assisted magnetic head  100 . 
     The hard disk drive  201  positions a slider  230  on a track by an assembly carriage device  203 . Further, the hard disk drive  201  has a plurality of drive arms  209 . The drive arms pivot about a pivot bearing shaft  206  by means of a voice coil motor (VCM)  205 , and are stacked in a direction along the pivot bearing shaft  206 . Further, an HGA  210  is attached to the tip of each drive arm. 
     Further, the hard disk drive  201  has a semiconductor laser  207  generating laser light for heating, a control circuit  204  controlling recording/reproducing and the generation of light by the semiconductor laser  207 , and an optical fiber  208  guiding the laser light to the slider  230 . 
     The HGA  210  will now be described with reference to  FIG. 41  ( b ).  FIG. 41  ( b ) is a perspective view illustrating a rear face side of the HGA  210 . In the HGA  210 , the slider  230  is fixed to a tip portion of a suspension  220 . Further, in the HGA  210 , one end portion of a wiring member  224  is electrically connected to a terminal electrode of the slider  230 . 
     The suspension  220  has a load beam  222 , a base plate  221  provided at a base portion of the load beam  222 , a flexure  223  fixed to and supported on the load beam  222  from the tip end side to the front side of the base plate  221  and having elasticity, and the wiring member  224 . The wiring member  224  has a lead conductor and connection pads electrically connected to both ends of the lead conductor. 
     Next, the slider  230  will be explained. The slider  230  has a slider base plate having the ABS  101  and a device formation part, and an output end part of the optical fiber  208  is inserted into the slider  230 . Further, the thermally assisted magnetic head  100  is formed at the device formation part. This slider  230  floats from the magnetic recording medium  202  by a minute distance. 
     In the hard disk drive  201 , when the HGA  210  is rotated, the slider  230  moves in a radial direction of the hard disk  202 , i.e., a direction traversing track lines. 
     Since the aforementioned HGA  210  and hard disk drive  201  have the thermally assisted magnetic head  100 , they are capable of preventing a melting and deformation of the near-field light generating layer, and are capable of preventing a deformation, melting and chipping of the magnetic layer arranged near the near-field light generating layer. 
     Though the above-mentioned embodiments explain a type in which a thin-film coil is wound like a flat spiral about the linking magnetic pole layer by way of example, the present invention is also applicable to a thermally assisted magnetic head of a type in which the thin-film coil is wound about the main magnetic pole layer.