Abstract:
A perpendicular type of magnetic recording medium includes a substrate, a soft magnetic underlying section including a plurality of distinct layers soft magnetic material, a recording section, and an intermediate section upon which the recording section is formed. The intermediate section is provided to improve the crystal orientation and impart a desired magnetic characteristic to the recording section. An uppermost one of the layers of soft magnetic material which, of all of the layers of soft magnetic material, is disposed closest to the intermediate section is predisposed to induce the intermediate section to crystallize in a desired way as it is formed. Therefore, the intermediate section may have a minimal thickness and yet achieve a crystallization that is sufficient to control the forming of the recording section.

Description:
PRIORITY STATEMENT  
       [0001]    This application claims the benefit of Korean Patent Application No. 10-2009-0021883, filed on Mar. 13, 2009, in the Korean Intellectual Property Office. 
       BACKGROUND  
       [0002]    The inventive concept relates to magnetic recording media. More particularly, the inventive concept relates to a perpendicular magnetic recording medium in which the direction of magnetization of bits of recorded data is perpendicular to the surface of a magnetic layer. 
         [0003]    The amount of information or data that must be processed by today&#39;s electronic devices is constantly rapidly increasing. Accordingly, the data must be recorded (stored) with a high-density and the data must be capable of being recorded/reproduced at a rapid rate. In this regard, magnetic recording devices have characteristics such as large storage capacity and fast access time. Accordingly, magnetic recording devices are being widely used as information memory devices by various digital devices, as well as by computers. These magnetic recording devices employ a magnetic recording medium to record (store) data, and a magnetic head (having a magnetic recording mechanism and a reproducing sensor) to write data onto/read data from the magnetic recording medium. 
         [0004]    A magnetic recording medium of a magnetic recording device may be of a longitudinal magnetic recording type or a perpendicular magnetic recording type according to the way in which the medium records (stores) data. In a longitudinal type of magnetic recording medium, the direction of magnetization of bits of recorded data is parallel to a surface of a magnetic layer. In a perpendicular type of magnetic recording medium, the direction of magnetization of bits of recorded data is perpendicular to the surface of the magnetic layer. Data can be recorded with a higher recording density on a perpendicular type of magnetic recording medium than on a longitudinal type of magnetic recording medium. 
         [0005]    A conventional perpendicular magnetic recording medium includes a soft magnetic underlayer, a recording layer having tracks along which data is recorded, and a passivation layer. The intermediate layer is provided, in part, to impart a specific crystallographic orientation to the recording layer formed thereon. However, the intermediate layer must be at least about 20 nm if it is to have a sufficient affect on the crystallization of the recording layer. Furthermore, the intermediate layer is formed of a relatively expensive material such as Ru. Thus, the thick intermediate layer of the conventional perpendicular magnetic recording medium contributes a significant amount to the relatively high cost of manufacturing the medium. 
         [0006]    The soft magnetic layer serves to attract the magnetic field generated by magentic head during a recording (write) operation However, the magnetic head is spaced relatively far from the soft magnetic underlayer because the intermediate layer is interposed between the recording layer and the soft magnetic underlayer. Thus, magnetic field generated by the head to write data onto the recording layer is dispersed by the provision of the intermediate layer. That is, the intermediate layer counteracts the effect of the soft magnetic underlayer. 
       SUMMARY  
       [0007]    According to an aspect of the inventive concept, there is provided a perpendicular magnetic recording medium including a substrate, a soft magnetic material section including a plurality of distinct layers of soft magnetic material disposed on the substrate, an intermediate section and disposed on the soft magnetic material section, and a recording section comprising a crystalline layer of magnetic material disposed on the intermediate section. The intermediate section comprises crystalline material predisposed to control a crystallizing of the material of the recording section when the recording section is formed on the intermediate section. Also, an uppermost one of the layers of soft magnetic material which, of all of the layers of soft magnetic material, is disposed closest to the intermediate section, is predisposed to impart a desired crystalline structure to material of the intermediate section when the intermediate section is formed on the soft magnetic material section. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0008]    The inventive concept will be more clearly understood from the following detailed description of the preferred embodiments thereof made in conjunction with the accompanying drawings in which: 
           [0009]      FIG. 1  is a sectional view of an embodiment of a perpendicular type of magnetic recording medium according to the inventive concept; 
           [0010]      FIG. 2  is a sectional view of diagram of another embodiment of a perpendicular type of magnetic recording medium according to the inventive concept; and 
           [0011]      FIG. 3  is a sectional view of still another embodiment of a perpendicular type of magnetic recording medium according to the inventive concept. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0012]    The inventive concept will now be described more fully with reference to the accompanying drawings. In the drawings, the thicknesses of layers and regions may be exaggerated for clarity. Furthermore, like reference numerals denote like elements throughout the drawings. 
         [0013]    Referring to  FIG. 1 , a perpendicular type of magnetic recording medium  100  according to the inventive concept includes a substrate  110 , a soft magnetic material section  130 , an intermediate section  150 , a recording section  170 , and a passivation layer  190  that are sequentially stacked one atop the other in the foregoing order. 
         [0014]    The substrate  110  may be of the same material that is used to form the substrate of a conventional perpendicular type of magnetic recording medium. For example, the substrate  110  may be of glass, MgO, AlMg, Si, and the like. Also, the substrate  110  may be circular. 
         [0015]    A seed layer (not shown) of Ta or a Ta alloy may be provided on the substrate  110 . Such a seed layer is used to facilitate the growth of the material (crystals) of the soft magnetic material section  130  on the substrate. In this case, therefore, the seed layer is interposed between the substrate  110  and the resulting soft magnetic material section  130 . Also, a buffer layer (not shown) or a magnetic domain control layer (not shown) may also be provided on the substrate  110  before the soft magnetic material section  130  is formed. Such buffer and magnetic domain control layers are conventional, per se, and therefore, will not be described in further detail. 
         [0016]    The soft magnetic material section  130  functions to attract a magnetic field generated by a magnetic head (not shown) during a magnetic recording (write) operation (hereinafter referred to as “writing magnetic field”) such that the field lines of the writing magnetic field extend perpendicular to the plane of the recording section  170 . 
         [0017]    In the embodiment of  FIG. 1 , the soft magnetic material section  130  includes a lower layer  131  of soft magnetic material, an upper layer  134  of soft magnetic material, and a separation layer  133  interposed between the lower layer  131  of soft magnetic material and the upper layer  134  of soft magnetic material so as to (magnetically) insulate the lower and upper layers  131  and  134  from each other. The lower layer  131  may be a layer of a material selected from the group consisting of an NiFe alloy, CoZrNb, CoZrTa, an FeTa alloy, and an FeCo alloy. The upper layer  134  may also be a layer of a material selected from the group consisting of an NiFe alloy, CoZrNb, CoZrTa, an FeTa alloy, and an FeCo alloy. The separation layer  133  may be of a non-magnetic material such as Ru. 
         [0018]    In order to induce a desired crystallization in the material used to form the intermediate section  150 , the upper layer  134  is preferably formed of soft magnetic material having the same crystalline structure as that desired for the intermediate section  150 . For example, the upper soft magnetic layer  134  may have a face centered cubic (FCC) crystalline structure or a hexagonal close packed (HCP) crystalline structure. Also, the separation layer  133  may function to orient the crystal unit cell structures of the upper layer  134  of soft magnetic material. For example, the separation layer  133  may be formed of Ru having an HCP crystalline structure. 
         [0019]    Furthermore, the upper layer  134  of soft magnetic material is formed to generate an anisotropic magnetic field (Hk) stronger (greater magnetic flux) than that generated by the lower layer  131  of soft magnetic material. Also, each of the lower layer  131  and the upper layer  134  is oriented such that its easy axis extends in a cross-track direction of the perpendicular magnetic recording medium  100 , i.e., across the tracks of the recording section  170 . The lower soft magnetic layer  131  may be thicker than the upper soft magnetic layer  134  so as to more effectively attract the writing magnetic field onto the recording medium  100 , and thereby align the field lines of the writing magnetic field so as to be perpendicular to the plane of the recording section  170 . For example, the lower soft magnetic layer  131  may have a thickness of 10 nm to 100 nm, and the upper soft magnetic layer  134  may have a thickness of 1 nm to 20 nm. 
         [0020]    According to the present embodiment, the lower layer  131  of soft magnetic material, which generates the relatively weak anisotropic magnetic field (Hk), effectively attracts the writing magnetic field so that the writing magnetic field is condensed on the recording section  170 . That is, when data is written on the recording section, the lower layer  131  of soft magnetic material is magnetized in a direction of its hard axis so the field lines of the writing magnetic field emanating from a pole of the magnetic head pass through the recording layer  170  and the soft magnetic section  130  and return to a return to the pole of the magnetic head. In this case, the high permeability of the lower layer  131  ensures that the flux of the writing magnetic field passing through the recording section  170  is high and remains constant. Because the lower layer  131  of soft magnetic material having such high permeability increases the intensity of the writing magnetic field, the overwrite-ability of the perpendicular type of magnetic recording medium  100  is improved, which overwrite-ability is otherwise degraded when the perpendicular magnetic anisotropy energy (Ku) is high. 
         [0021]    Furthermore, the lower soft magnetic layer  131  has a relatively insecure magnetic domain structure because it is fabricated to generate the weaker anisotropic magnetic field (Hk) to assure a high permeability. As a result, a stray field may be generated in the lower soft magnetic layer  131 . However, during a read operation, in which data is reproduced from the recording section  170 , the stray magnetic field generated in the lower layer  131  of soft magnetic material is dispersed in the upper layer  134  of soft magnetic material because the upper soft magnetic layer  134  generates the relatively strong anisotropic magnetic field (Hk). Therefore, the stray field is prevented from being noise in the recording section  170  disposed above the upper layer  134 . In other words, the field lines of the stray magnetic field are formed in the direction of the hard axis of magnetization of the upper soft magnetic layer  134 . Therefore, the stray field generated in the lower soft magnetic layer  131  during data reproduction will not be detected by (the reading sensor of) the magnetic head. 
         [0022]    The intermediate section  150  functions to impart a desired crystallographic orientation and magnetic characteristic to the recording section  170 . That is, the intermediate layer  150  is formed based on the material and crystalline structure desired for the recording section  170 . In this respect, the intermediate section  150  may consist of a single layer of material or may have a multi-layered structure formed of at least a material selected from the group consisting of Ru, a Ru oxide, MgO, and Ni. 
         [0023]    For example, in the case in which the recording section  170  is a layer of a Co-alloy or a Co-alloy oxide, the intermediate section  150  is preferably formed of Ru having the same type of crystalline structure as the Co-alloy. 
         [0024]    In an example of the embodiment of  FIG. 1 , the recording section  170  comprises a layer of magnetic grains of material, and the intermediate section  150  has a first intermediate layer  151  of Ru, and a second intermediate layer  152  of Ru and an oxide. The second intermediate layer  152  is disposed on the first intermediate layer  151  and preferably, is thinner than the first intermediate layer  151 . For example, the thickness of the first intermediate layer  151  is preferably in a range of 3 nm to 8 nm, and the thickness of the second intermediate layer  152  is preferably in a range of 5 nm to 8 nm. The first intermediate layer  151  and the second intermediate layer  152  also each have a granular structure. In particular, Ru grains of the second intermediate layer  152  are separated from one another by an oxide component of the layer. In this regard, the second intermediate layer  152  can be formed by reactive sputtering in an atmosphere having an oxygen concentration of 0.1 to 5% (═O 2 /(Ar+O 2 ). 
         [0025]    The first intermediate layer  151  functions to improve the crystallographic orientation of the layer of material of the recording section  170 , and the second intermediate layer  152  functions to control the formation of the grains of the layer of material of the recording section  170 . More specifically, the second intermediate layer  152  functions to minimize the grain size (average size of the grains) and to make the size of the grains as uniform as possible. 
         [0026]    In the embodiment of  FIG. 1  described above, the intermediate section  150  has a thickness in a range of 8 nm to 16 nm, which is significantly less than the thickness (about 20 nm) of an Ru intermediate layer of a conventional perpendicular type of recording medium. The intermediate section  150  has a sufficient thickness, though, because it comprises an epitaxial layer grown on a similar crystalline structure of the upper soft magnetic layer  134 . Thus, a magnetic recording medium according to the inventive concept may employ less Ru, which is a relatively expensive material. Therefore, a magnetic recording medium according to the inventive concept may be manufactured at a lower cost. 
         [0027]    Also, the magnetic head will be located relatively close to the soft magnetic section  130  (closer than a conventional recording medium which is comparable but which must employ a thicker intermediate section). Thus, dispersion of the writing magnetic field is suppressed. Accordingly, the recording section  170  can be magnetized with a relatively narrow magnetic field. This allows the perpendicular type of magnetic recording medium  100  to have relatively narrow tracks and thus, a correspondingly greater data storage capacity. 
         [0028]    The recording section  170 , at which data is magnetically recorded, may consist of a single layer of material or may have a multi-layered structure. Furthermore, the recording section  170  can be of the same material as the recording layer of a conventional perpendicular type of magnetic recording medium. Examples of the material include include CoPt alloys, CoPt alloy oxides, FePt alloys, and FePt alloy oxides. Also, the recording section  170  may have an FCC crystalline structure or an HCP crystalline structure. The crystallinity of the recording layer  170  is enhanced during its formation by the intermediate section  150  on which the recording section  170  is formed. 
         [0029]    The passivation layer  190  protects the recording section  170 , and may be a Diamond Like Carbon (DLC) passivation layer. In this case, the DLC passivation layer enhances the surface hardness of the perpendicular type of magnetic recording medium  100 . In addition, a lubricating layer (not shown) of a tetraol lubricant, or the like, may be formed on the passivation layer  190 . Such a lubricating layer would minimize any abrasion of a magnetic head and the (DLC) passivation layer which may occur if the head is caused to slide along the recording medium  100 . 
         [0030]      FIG. 2  illustrates another embodiment of a perpendicular type of magnetic recording medium  200  according to the inventive concept. 
         [0031]    Referring to  FIG. 2 , the perpendicular type of magnetic recording medium  200  includes a substrate  110 , a soft magnetic material section  230 , an intermediate section  150 , a recording section  170 , and a passivation layer  190  that are sequentially stacked one atop the other in the foregoing order. The substrate  110 , the intermediate section  150 , the recording section  170 , and the passivation layer  190  are substantially the same as those of the embodiment of  FIG. 1  and thus, will not be described in further detail. 
         [0032]    The soft magnetic material section  230  includes a lower layer  131  of soft magnetic material, an upper portion  234  comprising soft magnetic material, and a separation layer  133  interposed between and magnetically insulating the lower layer  131  of soft magnetic material and the upper portion  234 . Furthermore, the upper portion  234  includes first and second unit layers  235  and  237  of soft magnetic material, and a spacer  236  interposed between the first and second unit layers  235  and  237 . In this embodiment, the first and second unit soft magnetic layers  235  and  237  have a Ruderman-Kittel-Kasuya-Yosida (RKKY) coupling structure in which the layers are anti-ferromagnetically coupled through the non-magnetic metal layer, i.e., the spacer  236 , interposed therebetween. The spacer  236 , in addition to being of a non-magnetic material, preferably has a thickness of no more than 2 nm, e.g., 0.8 nm, thereby allowing the first and second unit layers  235  and  237  to be anti-ferromagnetically coupled. 
         [0033]    The thickness of the first and second unit layers  235  and  237  of soft magnetic material are selected such that the upper layer  234  of soft magnetic material generates a strong anisotropic magnetic field (Hk) to suppress the generation of a domain wall, which would otherwise be a source of noise. For example, the thickness of the first and second unit layers  235  and  237  of soft magnetic material is preferably 5 nm or less. Also, the second unit layer  237  may be formed to have the same type of crystalline structure as that desired for the intermediate layer  150  so that the intermediate layer  150  takes on the desired crystallinity as it is formed. For example, the second unit layer  237  of soft magnetic material may have an FCC crystalline structure or an HCP crystalline structure. Also, the spacer  236  may function to orient the crystal unit cell structures of the second unit layer  237  of soft magnetic material. To this end, the spacer  236  may be formed of Ru having an HCP crystalline structure, for example. 
         [0034]    As mentioned above, the upper portion  234  of soft magnetic material has an RKKY coupling structure. Therefore, the lower layer  131  and the upper portion  234  can be formed of the same soft magnetic material, and the upper portion  234  of soft magnetic material may generate an anisotropic magnetic field (Hk) whose flux is greater than that generated by the lower layer  131 . In this way, the writing magnetic field is effectively attracted to the recording section  170  but noise due to a stray magnetic field can be prevented. 
         [0035]    Furthermore, the crystallinity of the intermediate section  150  is assured during its formation, even though the intermediate section  150  is formed to be relatively thin, by forming the second unit layer  237 , i.e., the uppermost layer of upper portion  234 , of soft magnetic material having the same type of crystalline structure as that intended for the intermediate section  150 . Thus, the embodiment of  FIG. 2  may employ less Ru, which is a relatively expensive material. Therefore, a magnetic recording medium according to the inventive concept may be manufactured at a lower cost. Also, the magnetic head will be located relatively close to the section  230  of soft magnetic material (closer than a conventional recording medium which is comparable but which must employ a thicker intermediate section). Thus, dispersion of the writing magnetic field is suppressed. Accordingly, the recording section  170  can be magnetized with a relatively narrow magnetic field. This allows the perpendicular type of magnetic recording medium  200  to have relatively narrow tracks and thus, a correspondingly greater data storage capacity. 
         [0036]      FIG. 3  illustrates another embodiment of a perpendicular type of magnetic recording medium  300  according to the inventive concept. 
         [0037]    The magnetic recording medium  300  has a soft magnetic section  330  including a lower layer  131  of soft magnetic material, a separation layer  133 , and an upper portion  334  of soft magnetic material. The lower layer  131  and the separation layer  133  are substantially the same as those of the embodiment of  FIG. 1  and thus, will not be described in further detail. 
         [0038]    The upper portion  334  of soft magnetic material ha a plurality of unit layers  335 ,  337 , and  339  of soft magnetic material, and a plurality of spacers  336  and  338  each of which is interposed between adjacent ones of a respective pair of the unit layers  335 ,  337 , and  339 . Of the unit layers  335 ,  337 , and  339  of soft magnetic material, the unit layer  339  disposed closest to the intermediate section  150  (which unit layer  339  will be referred to hereinafter as “the uppermost unit layer  339 ”) may be formed of material having the same type of crystalline structure as that intended fro the intermediate section  150  so as to facilitate the crystallization of the material of the intermediate section  150  as the intermediate section  150  is formed. For example, the uppermost unit layer  339  of soft magnetic material may have an FCC crystalline structure or an HCP crystalline structure. Also, of the spacers  336  and  338 , the spacer  336  disposed under the uppermost unit layer  339  of magnetic material (which spacer  336  will be referred to hereinafter as “the uppermost spacer  336 ”) may serve to orient the crystal unit cell structures of the uppermost unit layer  339 . To this end, the uppermost spacer  336  may be formed of Ru having an HCP crystalline structure, for example. Thus, the crystallinity of the intermediate section  150  is assured during its formation, even when the intermediate section  150  is formed to be relatively thin. 
         [0039]    Finally, embodiments of the inventive concept have been described herein in detail. The inventive concept may, however, be embodied in many different forms and should not be construed as being limited to the embodiments described above. Rather, these embodiments were described so that this disclosure is thorough and complete, and fully conveys the inventive concept to those skilled in the art. Thus, the true spirit and scope of the inventive concept is not limited by the embodiments described above but by the following claims.