Abstract:
The magnetic head is capable of preventing variation of magnetic fields working to a read-element, stably generating output signals and improving production yield. The magnetic head comprises: a read-head including a read-element; and a shield for magnetic-shielding the read-element, the shield has a hexagonal planar shape, and one side of the shield is flush with an air bearing surface of the magnetic head.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to a magnetic head, more precisely relates to a magnetic head, which has a unique shield and which is capable of restraining variation of output signals from a read-head and boosting yield. 
         [0002]      FIG. 7  shows a positional relationship between a recording medium  5  and a read-head of a conventional magnetic head, which is reading magnetic data from the recording medium  5 . The read-head has a read-element  10 , which is sandwiched between a lower shield  12  and an upper shield  14 . The lower and upper shields  12  and  14  are soft magnetic films. End faces of the lower and upper shields  12  and  14  are arranged to face a recording surface of the recording medium  5 , so that recorded data can be read by the read-element  10 . The lower and upper shields  12  and  14  magnetically shield the read-element  10 , so that the read-element  10  is capable of sensing data, which are recorded immediately below the read-element  10 , with high resolution. The lower and upper shields  12  and  14  usually have rectangular planar shapes or square planar shapes. 
         [0003]      FIG. 9  shows a schematic view of the read-element  10  seen from an air bearing surface side. The read-element  10  is sandwiched between the lower and upper shields  12  and  14  with an insulating layer, and terminals  22  are respectively provided to the both sides of the read-element  10 . 
         [0004]    The shown read-element  10  is a spin-valve type giant magnetoresistance (GMR) element. The GMR element is constituted by a plurality of magnetic and nonmagnetic layers. The layers are layered from the bottom as an antiferromagnetic layer  101 / a  pin layer  102 / a  free layer  103 / a  cap layer  104 . The antiferromagnetic layer  101  antiferromagnetically couples with the pin layer  102  so as to fix a magnetizing direction in a height-direction of the element. The free layer  103  freely changes its magnetizing direction on the basis of magnetic data recorded in the medium. A GMR effect, which changes resistance, depends on an angle between the magnetizing directions of the pin layer  102  and the free layer  103 ; the magnetic data can be detected, from the medium, as variation of the resistance. 
         [0005]    In the conventional spin-valve type magnetoresistance effect element, hard films  20 , which are made of a permanent magnet material having a relatively great coercive force, are respectively provided on the both sides of the read-element, and the magnetizing direction of the free layer  103  is oriented in the core-width direction (in the right-and-left direction in the drawing) when no external magnetic field works. Therefore, reproducing efficiency can be maximized, and a symmetric property of reproduced output signals can be secured. 
         [0006]    In a production process of the magnetic head, a strong magnetic field of several kOe is applied in the core-width direction so as to orient magnetization directions of the hard films  20  in the magnetizing direction of the magnetic field. In this magnetizing step, magnetic layers of the magnetic head are magnetized in the magnetizing direction. However, their magnetization directions are varied when the magnetic field is disappeared. Namely, the magnetization directions of the hard films are almost the same as the magnetizing direction; the magnetization direction of the free layer is almost the same as the magnetizing direction due to bias magnetic fields of the hard films; and the magnetization direction of the pin layer is oriented in the height direction of the element, without reference to the magnetizing direction, due to the antiferromagnetic coupling with the antiferromagnetic layer  101 . 
         [0007]    On the other hand, the lower and the upper shields  12  and  14  are made of a soft magnetic material having a relatively small coercive force, so their magnetic patterns have a structure for minimizing static magnetic energies. Namely, the entire shield has a magnetic domain structure, in which a macroscopic magnetization of the entire shield is near zero. The conventional rectangular or square shield is divided into four magnetic domains (see  FIGS. 8A and 8B ) or seven magnetic domains (see  FIG. 8C ). Note that, even if shields have the same shapes, the magnetic domain structure is changed from seven-domain structure to four-domain structure by a magnetizing process, and vice versa. 
         [0008]    By the way, a width and a height of the shield is several dozen μm. On the other hand, a width and a height of the read-element is, for example, about 100 nm, so they are much smaller than those of the shield, i.e., from one-1000th to a one-several hundredth. Therefore, the read-element is badly influenced by the magnetization of the upper shield  14 . Especially, in the spin-valve type GMR element, the terminals  22  are provided to the both sides of the element, so asperities are formed in the side face of the upper shield  14  facing the element. With the asperities, great leakage magnetic fields are generated from the projected parts of the asperities. 
         [0009]    Directions of the leakage magnetic fields are the same as the magnetization direction of the shield in the vicinity of the element. The magnetic fields shown in  FIGS. 10A and 10B , which respectively correspond to the magnetic domain structure shown in  FIGS. 8A and 8B , work. In  FIG. 10A , the magnetic field works in the direction equal to the magnetization direction of the hard films  20 ; in  FIG. 10B , the magnetic field works in the opposite direction of the magnetization direction of the hard films  20 . 
         [0010]    According to an experiment, in case of having seven magnetic domains shown in  FIG. 8C , the magnetization direction of the shield was uniquely defined after disappearing the magnetizing field. On the other hand, in case of having four magnetic domains as shown in  FIGS. 8A and 8B , clockwise magnetic domain structures and counterclockwise magnetic domain structures are formed with the same probability after disappearing the magnetizing field. Therefore, intensities of a bias magnetic field working to the read-element, which is a resultant magnetic field of the magnetic fields generated by the hard films  20  and the projected parts of the upper shield, was varied on the basis of the clockwise or counterclockwise magnetic domain structure after disappearing the magnetizing field. As the result of the variation, output signals of the read-element were also varied. 
         [0000]    
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 Patent Document 1 
                 Japanese Patent Gazette No. 2001-229515 
               
               
                   
                 Patent Document 2 
                 Japanese Patent Gazette No. 2005-353666 
               
               
                   
                   
               
             
          
         
       
     
       SUMMARY OF THE INVENTION 
       [0011]    The present invention was conceived to solve the problems: the variation of the magnetic domain structure of the upper shield, the variation of output signals of the read-element and descent of production yield of magnetic heads. 
         [0012]    An object of the present invention is to provide a magnetic head, which is capable of preventing variation of magnetic fields working to a read-element, stably generating output signals and improving production yield. 
         [0013]    Another object is to provide a magnetic disk drive unit having the magnetic head of the present invention. 
         [0014]    To achieve the objects, the present invention has following structures. 
         [0015]    Namely, the magnetic head of the present invention comprises: a read-head including a read-element; and a shield for magnetic-shielding the read-element, the shield has a hexagonal planar shape, and one side of the shield is flush with an air bearing surface of the magnetic head. 
         [0016]    Note that, one or both of a lower shield and an upper shield, which sandwich the read-element as the shield, may have the hexagonal planar shapes. 
         [0017]    In the magnetic head, the shield may be line-symmetrically formed in a core-width direction with respect to a position of the read-element. Further, the shield may be line-symmetrically formed in a height direction. By line-symmetrically forming the shield, a stable magnetic domain structure can be effectively produced. 
         [0018]    Preferably, inner angles of corner sections, which are respectively formed in both side faces in a core-width direction, are 170 degrees or less. 
         [0019]    Another magnetic head comprises: a read-head including a read-element; and a shield for magnetic-shielding the read-element, the shield has a triangular planar shape, and one side of the shield is flush with an air bearing surface of the magnetic head. 
         [0020]    In the magnetic head, the shield may be line-symmetrically formed in a core-width direction with respect to a position of the read-element. 
         [0021]    The magnetic disk drive unit of the present invention comprises the magnetic head of the present invention. By using the magnetic head of the present invention, the magnetic disk drive unit, which has excellent reproduction characteristics, can be produced. 
         [0022]    In the present invention, the shield has the hexagonal or triangular planar shape, so that a magnetic domain structure, which is produced in the shield after the magnetizing step, can be stable and a magnetization direction of a magnetic domain can be uniquely defined with respect to a magnetizing direction. Therefore, variation of output signals of the read-element can be restrained, and the magnetic head having stable characteristics can be realized. Further, by restraining variation of quality, production yield of the magnetic head can be improved. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    Embodiments of the present invention will now be described by way of examples and with reference to the accompanying drawings, in which: 
           [0024]      FIG. 1A  is a plan view of shields of a magnetic head of a first embodiment of the present invention; 
           [0025]      FIG. 1B  is a perspective view of the shields thereof; 
           [0026]      FIGS. 2A and 2B  are explanation views showing magnetic domains and a magnetizing direction of the shields of the first embodiment; 
           [0027]      FIG. 3A  is a plan view of the shields of a second embodiment; 
           [0028]      FIG. 3B  is a perspective view of the shields thereof; 
           [0029]      FIGS. 4A and 4B  are explanation views showing magnetic domains and a magnetizing direction of the shields of the second embodiment; 
           [0030]      FIG. 5  is a plan view of a magnetic disk drive unit including the magnetic head of the present invention; 
           [0031]      FIG. 6  is a perspective view of a head slider; 
           [0032]      FIG. 7  is an explanation view showing the positional relationship between the recording medium and the read-head of the conventional magnetic head; 
           [0033]      FIGS. 8A-8C  are explanation views of the magnetic domain structure of the conventional shields; 
           [0034]      FIG. 9  is a schematic view showing the read-element and the shields; and 
           [0035]      FIGS. 10A and 10B  are explanation views showing the magnetization direction of the shields in the vicinity of the read-element. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0036]    Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. 
         [0037]    The magnetic head of the present invention is characterized by a shape of shields (an upper shield and a lower shield), which are formed in a read-head. Other elements of the magnetic head, e.g., a read-element, a write-head, are the same as elements included in the conventional magnetic head. Therefore, the shields of a read-head will be explained in the following description. 
       First Embodiment 
       [0038]      FIG. 1A  is a plan view of shields of a magnetic head, and  FIG. 1B  is a perspective view of the shields. In the present embodiment, the shields  30  are characterized by hexagonal planar shapes. As shown in  FIG. 1A , one side “A” of each hexagonal shield  30  is flush with an air bearing surface  40  of the magnetic head. Each of the shields  30  is symmetrically formed in the right-and-left direction (in the core-width direction) with respect to a center line “L” of a read-element  10 . The hexagonal shield  30  has six sides “A”, “B”, “C”, “D”, “E” and “F”. The sides “A” and “D” are parallel to the air bearing surface  40 . The shield  30  is symmetrically formed, in the vertical direction (in the height direction), with respect to a straight line, which connects one corner section between the sides “B” and “C” and another corner section between the sides “E” and “F”. The corner section between the sides “B” and “C” and the corner section between the sides “E” and “F” are respectively formed in both side faces in the core-width direction and convexes outward. 
         [0039]    In  FIG. 1B , the read-element  10  is sandwiched between a pair of shields  30 . The shields  30  are made of a soft magnetic material, e.g., NiFe, and have a prescribed thickness. Actually, the shields  30  are short hexagonal columns. 
         [0040]    In case of forming the shields  30  by electrolytic plating, firstly photoresist is applied to a surface of a work piece, then the photoresist is patterned so as to form hexagonal cavities in specific areas, in which the shields  30  will be respectively formed. Finally, the hexagonal cavities are filled with a magnetic material by plating. The planar shapes of the shields  30  may be optionally selected by optionally patterning the photoresist. The conventional rectangular shields are formed by patterning the photoresist to form rectangular cavities. Therefore, the hexagonal shields  30  can be formed, by the conventional method, without additional steps. The magnetic layers of the magnetic material may be formed by sputtering, etc. 
         [0041]    In  FIG. 2A , a magnetic field “H” is applied to the shield  30  shown in  FIG. 1  for magnetization; in  FIG. 2B , the magnetic field is disappeared. The magnetic field “H” is applied in the core-width direction and in parallel to a surface of the shield  30 . 
         [0042]    As shown in  FIG. 2A , by applying the magnetic field “H” to the shield  30 , the shield  30  is magnetized in the same direction and has a single magnetic domain. When the magnetic field “H” is disappeared, the shield has a seven-domain structure as shown in  FIG. 2B . In a magnetic layer, when magnetic domains are formed, the magnetic walls are formed in corner sections of the layer. In the present embodiment, the shield  30  has the hexagonal planar shape, and the magnetic walls are formed at apexes of the side faces of the shield  30  so that the shield  30  has the seven-domain structure. 
         [0043]    Since the shield  30  are line-symmetrically formed in the core-width direction and the height direction, the magnetic domains of the shield  30  are line-symmetrically arranged in the core-width direction and the height direction. Magnetization directions of the magnetic domains constitute a reflux magnetic domain structure via the central magnetic domain. Therefore, the magnetic walls are arranged to minimize static magnetic energy of the entire shield  30 . 
         [0044]    According to an experiment, in case of the seven-domain structure shown in  FIG. 2B , the magnetization directions of the magnetic domains of the shield  30  were uniquely defined by the magnetizing direction. Namely, in case of the seven-domain structure, the central magnetic domain of the shield  30  was magnetized in the direction opposite to the magnetizing direction, i.e., rightward. The magnetic domain corresponding to the read-element  10  was magnetized in the magnetizing direction. 
         [0045]    In  FIG. 2A , the magnetizing direction is leftward, but it may be rightward. In case of magnetizing rightward, the central magnetic domain of the shield  30  is magnetized rightward. In this case too, the magnetic domain corresponding to the read-element  10  is magnetized in the magnetizing direction. 
         [0046]    In the present embodiment, the shields  30  have the hexagonal planar shapes, so that the magnetic domain structures of the shields  30  can be stabilized as the seven-domain structures when the magnetizing field working to the shields  30  is disappeared. Further, the magnetization directions of the magnetic domains, which work to the read-element  10 , can be uniquely defined. 
         [0047]    By uniquely defining the magnetic domains and the magnetization directions of the shields  30 , directions of leakage magnetic fields, which leak from the shields  30  and work to the read-element  10 , can be fixed. Therefore, variation of a bias magnetic field working to the read-element  10  can be prevented, characteristics of the magnetic head can be stabilized and production yield of the magnetic head can be improved. 
         [0048]    To compulsorily form the shields  30  into the seven-domain structures, the shields  30  have the hexagonal planar shapes. In each of the shields  30 , inner angles of a corner section between sides “B” and “C” and a corner section between the sides “E” and “F” are defined so as to induce magnetic walls. Preferably, the inner angles of the corner sections, which are angles between the sides “B” and “C” and between the sides “E” and “F”, are 170 degrees or less. 
         [0049]    The shields  30  may be asymmetrically formed in the height direction and the core-width direction, but the shields  30  symmetrically formed have excellent characteristics. 
         [0050]    In  FIG. 1B , both of the shields  30  are formed into the hexagonal shapes, but the present invention is not limited to the present embodiment. For example, one of the shields  30  may be formed into the hexagonal shape, and the other shield  30  may be formed into other shapes, e.g., rectangular shape. 
       Second Embodiment 
       [0051]    Shields of a second embodiment are shown in  FIGS. 3A and 3B .  FIG. 3A  is a plan view of the shields  32 , and  FIG. 3B  is a perspective view of the shields  32 , which sandwich the read-element  10 . 
         [0052]    The shields  32  of the present embodiment are characterized by the triangular planar shapes. One side “G” of each triangular shield  32  is flush with the air bearing surface  40  of the magnetic head. Each of the shields  30  is line-symmetrically formed in the right-and-left direction (in the core-width direction) with respect to the read-element  10 . 
         [0053]    In  FIG. 4A , the magnetic field “H” is applied to the shield  32  for magnetization;  FIG. 2B  shows a magnetic domain structure of the shield  32  when the magnetic field is disappeared. Note that, the magnetic field “H” is applied to the shield  32  as well as the first embodiment. 
         [0054]    As shown in  FIG. 4A , by applying the magnetic field “H” to the shield  32  having the triangular planar shape, a demagnetizing field, whose direction is opposite to the magnetizing direction, is produced in a corner section defined by sides “J” and “K”. In  FIG. 4A , a magnetic wall is formed in the corner section defined by the sides “J” and “K”, and magnetization, whose direction is opposite to the magnetizing direction, is induced. 
         [0055]    In the shield  32  having the triangular planar shape, by inducing the magnetization which causes the demagnetizing field, three magnetic domains are induced in the shield  32  and their magnetization directions maintain the demagnetizing field when the magnetizing field is disappeared. The magnetic domain structure of the shield  32  and the magnetization directions of the magnetic domains are shown in  FIG. 4B . Since the shield  32  has the triangular planar shape, the magnetic domain corresponding to the read-element  10  is magnetized in the magnetizing direction. In other words, the shield  32  is asymmetrically formed in the vertical direction (the height-direction) with respect to the magnetizing direction, so that the demagnetizing field is slanted and the magnetization directions of the magnetic domains of the shield  32  can be uniquely defined. 
         [0056]    In the present embodiment too, by uniquely defining the magnetic domains and the magnetization directions of the shields  32 , variation of the magnetization directions of the magnetic domains (the magnetization directions are not uniquely defined). Further, variation of the bias magnetic field working to the read-element  10  can be prevented, so that variation of output signals of the read-element  10  can be prevented. Therefore, characteristics of the magnetic head can be stabilized and production yield of the magnetic head can be improved. 
         [0057]    In case of forming the triangular shields  32 , conditions of the triangle shape, e.g., apex angles, are not limited. For example, the shields  32  may be asymmetrically formed in the core-width direction. Preferably, the shields  32  is symmetrically formed in the core-width direction with respect to the position of the read-element  10 , i.e., isosceles triangle. In this case, a stable magnetic domain structure can be produced. 
         [0058]    The present invention is not limited to the GMR type magnetic head and can be applied to magnetic heads, each of which has the shield for magnetically shielding the read-element. For example, the present invention can be applied to MR-type, spin-valve type, GMR type, TMR (Tunneling Magnetoresistance) type and CPP (Current Perpendicular to the Plane)-GMR type magnetic heads. 
       (Magnetic Disk Drive Unit) 
       [0059]    A magnetic disk drive unit, in which the magnetic head of the present invention is attached, is shown in  FIG. 5 . The magnetic disk drive unit  50  has a box-shaped casing  51  and a magnetic recording disk  53 , which is accommodated in the casing  51  and rotated by a spindle motor  52 . A carriage arm  54  is provided near by the magnetic recording disk  53  and capable of turning in parallel to the surface of the magnetic recording disk  53 . A head suspension  55  is attached to a front end of the carriage arm  54  and extended therefrom. A head slider  60  is attached to a front end of the head suspension  55 . The head slider  60  is attached in a face of the head suspension  55  facing the surface of the magnetic recording disk  53 . 
         [0060]      FIG. 6  is a perspective view of the slider  60 . Float rails  62 a and  62 b, which are formed for floating the head slider  60  from the surface of the magnetic recording disk  53 , is formed in an air bearing surface of the head slider  60 , which faces the magnetic recording disk  53 , along edges of a slider body  61 . A magnetic head  63 , which includes the shields having the hexagonal or triangular planar shapes, is provided on the front end side of the head slider  60  (on the downstream side of an air stream) and faced the magnetic recording disk  53 . The magnetic head  63  is protected by a protection film  64  coating the magnetic head  63 . 
         [0061]    When the magnetic recording disk  53  is rotated by the spindle motor  52 , the head slider  60  is floated from the surface of the magnetic recording disk  53  by the air stream generated by rotation of the magnetic recording disk  53 . Then, an actuator  56  performs a seeking action, so that the magnetic head  63  is capable of recording data in and reproducing data from the magnetic recording disk  53 . 
         [0062]    The invention may be embodied in other specific forms without departing from the spirit of essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.