JP2015153447A - Perpendicular magnetic recording medium, method of producing perpendicular magnetic recording medium, and perpendicular recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a perpendicular magnetic recording medium having recording and reproducing characteristics excellent in SNR.SOLUTION: A perpendicular magnetic recording medium includes, on a non-magnetic substrate, at least one ground layer, and a perpendicular recording layer. The perpendicular recording layer includes: a ferromagnetic layer; and a dielectric magnetic layer having magnetic and dielectric properties and having crystal particles and an amorphous grain boundary region surrounding the crystal particles.

Description

The present invention relates to a perpendicular magnetic recording medium, a method for manufacturing a perpendicular magnetic recording medium, and a perpendicular recording / reproducing apparatus.

  In recent years, the range of application of magnetic recording devices such as magnetic disk devices, flexible disk devices, and magnetic tape devices has been remarkably increased, and the importance has increased, and the recording density of magnetic recording media used in these devices has increased. Significant improvements are being made. Particularly in HDD (Hard Disk Drive), since the introduction of MR (Magneto Resistive) head and PRML (Partial Response Maximum Likelihood) technology, the increase in areal recording density has increased further, and in recent years GMR (Giant Magnet Resistive) head has further increased. TuMR (Tunnel Magneto Resistive) heads have also been introduced, and the surface recording density continues to increase at a rate of about 1.5 times a year.

  On the other hand, a so-called perpendicular magnetic recording system as a magnetic recording system for HDDs has been rapidly used in recent years as a technique to replace the conventional in-plane magnetic recording system. The perpendicular magnetic recording method is suitable for increasing the surface recording density because the crystal grains of the recording layer for recording information have an easy axis of magnetization in the direction perpendicular to the substrate.

  A perpendicular magnetic recording medium is generally composed of a backing layer made of a soft magnetic material on a nonmagnetic substrate, an underlayer for controlling the perpendicular orientation of the magnetic recording layer, and a perpendicularly oriented magnetic recording layer. is there.

  However, as the surface recording density increases, the conventional perpendicular magnetic recording / reproducing system has a limitation due to the fact that the recording is performed by "magnetism (magnetic field)".

  Recording at high density is equivalent to reducing the occupied area on a medium of 1 bit (the minimum unit of magnetically recorded data). In order to cope with this, the magnetic recording layer of the magnetic recording medium is required to have a smaller particle size and magnetic cluster. This is because if the particle diameter and magnetic cluster are kept as they are, the SNR (Signal-to-Noise Ratio) of the data reproduction signal is deteriorated and sufficient characteristics cannot be obtained.

  It is known that when the particle size or magnetic cluster is reduced, the retention of recorded data becomes unstable due to the influence of heat (thermal fluctuation phenomenon). In order to withstand this, it is necessary to use a magnetic material having a high Ku. However, when a high Ku material is used, since the coercive force of the magnetic recording layer increases, a higher write magnetic field is required when recording data.

  On the other hand, on the recording / reproducing head side, the recording magnetic field is largely due to the magnetic material used for the recording element (magnetic pole), and thus there is a limit to the write magnetic field generated.

  As a proposal for solving this problem, a proposal for recording data on a magnetic recording layer by an electric field has been proposed. For example, when recording by magnetism, an electric field is generated on the medium side to reduce the coercive force of the magnetic recording layer (see, for example, Patent Document 1), or the resonance between the high-frequency electric field and the magnetic spin of the magnetic recording layer. There is a method of reducing the coercive force of the recording layer by using it (microwave assisted recording, MAMR) (see, for example, Patent Document 2). However, in the former, there is a problem that the magnetic recording medium side needs to be grounded in the magnetic recording apparatus, and the structure of the head is complicated because a magnetic field and an electric field are generated and controlled simultaneously. The latter has a problem that the structure becomes more complicated because a mechanism for generating a high-frequency magnetic field is incorporated in the head.

  In addition, a method of recording and reproducing data by using an electric field instead of magnetic recording and reproducing by using a ferroelectric as a recording layer has been proposed (for example, see Patent Document 3). According to this method, it is only necessary to apply a voltage when writing data to the recording medium, and since data is also reproduced by an electric field, the recording / reproducing element generates a conductive probe and a magnetic field instead of a magnetic material. The coil can be configured, and the limitation of the writing ability is eliminated. However, this method has problems such as localized polarization instability and slower recording / reproducing speed than the magnetic recording method.

In recent years, materials having both magnetic properties and dielectric properties have been studied as new materials. In particular, multiferroic materials having both ferromagnetism and ferroelectricity are attracting attention. As the multiferroic material, for example, BiFeO ₃ which is a ferroelectric material having magnetism, and a material in which Bi is replaced with Ba and Fe is replaced with Mn are known. A technique has been reported in which these materials are incorporated into a magnetic recording layer made of a conventional magnetic material, and writing is performed by an electric field and reproduction is performed by a magnetic field (see, for example, Non-Patent Documents 1 to 3).

  Since a magnetic recording medium using a material having both magnetism and dielectric properties can be written by an electric field, there is a possibility that a high recording density can be realized by downsizing a writing element that generates an electric field.

JP 2006-139854 A JP 2007-265512 A JP 2008-219007 A

Proceedings of the 60th JSAP Spring Meeting, 28a-D3-8, pp. 06-017 (2013) 37th Annual Meeting of the Magnetic Society of Japan, 3aC-6, pp. 41 (2013) The 58th Annual Magnetics and Magnetic Materials (MMM) Conference, Abstract, FS-15, p. 587 (2013)

  However, when a perpendicular magnetic recording medium is manufactured using a material having both magnetism and dielectric properties, there is a problem that noise is generated during recording and reproduction and it is difficult to sufficiently increase the SNR.

  An object of the present invention is to provide a perpendicular magnetic recording medium having recording / reproducing characteristics excellent in SNR in view of the above-described problems of the prior art.

The present invention has at least one underlayer and a perpendicular recording layer on a nonmagnetic substrate,
The perpendicular recording layer is
A ferromagnetic layer;
Provided is a perpendicular magnetic recording medium having both magnetic properties and dielectric properties, and having a dielectric magnetic layer having crystal grains and an amorphous grain boundary region surrounding the crystal grains.

  According to the present invention, a perpendicular magnetic recording medium having recording / reproducing characteristics excellent in SNR can be provided.

1 is a schematic cross-sectional view of a perpendicular magnetic recording medium according to a first embodiment of the present invention. 1 is a schematic cross-sectional view of a perpendicular recording layer of a perpendicular magnetic recording medium according to a first embodiment of the present invention. The schematic diagram showing the perpendicular recording / reproducing apparatus which concerns on the 2nd Embodiment of this invention.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described. However, the present invention is not limited to the following embodiments, and various modifications and changes can be made to the following embodiments without departing from the scope of the present invention. Substitutions can be added.
[First Embodiment]

  A configuration example of the perpendicular magnetic recording medium of this embodiment will be described.

  The perpendicular magnetic recording medium of this embodiment has at least one underlayer and a perpendicular recording layer on a nonmagnetic substrate. The perpendicular recording layer can include a ferromagnetic layer and a dielectric magnetic layer having both magnetic properties and dielectric properties and having crystal grains and an amorphous grain boundary region surrounding the crystal grains.

  As described above, conventionally, when a perpendicular magnetic recording medium is manufactured using a material having both magnetism and dielectric properties, noise is generated during recording and reproduction, and the SNR cannot be sufficiently increased.

  Therefore, the inventors of the present invention examined the reason why the SNR could not be sufficiently increased.

  First, as described above, multiferroic materials are known as materials having both magnetism and dielectric properties. These materials often have a perovskite structure containing oxygen, etc., and the structure is complicated. Crystallinity is an important factor for the development of properties. In addition, film formation is difficult, and the composition deviates from the stoichiometric ratio. And oxygen deficiency is likely to occur. These structural defects cause noise when reading information from the magnetic head according to the study by the inventors of the present invention. In addition, when the crystallinity of a material having both magnetism and dielectric properties is improved, the crystal grains are significantly enlarged. For this reason, it is difficult to obtain a smooth medium surface, which makes the flight of the head unstable, and structural defects due to oxygen deficiency and enlarged crystal grains cause magnetic noise when reading information using a magnetic head. It became clear that

  The inventors of the present invention have studied to solve the above problems. As a result, in a perpendicular magnetic recording medium having at least one underlayer and a perpendicular recording layer on a nonmagnetic substrate, the perpendicular recording layer is a ferromagnetic layer. And a dielectric magnetic layer having both magnetism and dielectric properties. Further, it has been found that by making the dielectric magnetic layer a structure having crystal grains and an amorphous grain boundary region surrounding the crystal grains, noise of the dielectric magnetic layer can be reduced and recording / reproduction characteristics excellent in SNR can be obtained. Was completed.

  That is, when the perpendicular recording layer has a dielectric magnetic layer having a granular structure, enlargement of crystal grains of the dielectric magnetic layer is suppressed and the grain size is uniformed (reduction in diameter dispersion), and recording / reproduction characteristics with excellent SNR are achieved. can get.

  Further, since the dielectric magnetic layer has a granular structure, the crystal grain size of the crystal grains of the dielectric magnetic layer can be reduced, and the surface of the dielectric magnetic layer becomes smooth. As a result, it has been found that the flying of the recording / reproducing head can be stabilized and the spacing loss can be reduced, and the recording / reproducing characteristics excellent in SNR can be obtained.

  1A to 1D are schematic cross-sectional views showing a configuration example of a perpendicular magnetic recording medium according to this embodiment.

  The perpendicular magnetic recording medium 10 </ b> A shown in FIG. 1A can have, for example, a structure having a base layer 12 and a perpendicular recording layer 13 on a nonmagnetic substrate 11. The perpendicular recording layer 13 can include a ferromagnetic layer 131 and a dielectric magnetic layer 132. At this time, the stacking order of the ferromagnetic layer 131 and the dielectric magnetic layer 132 is not particularly limited. For example, the perpendicular magnetic recording medium 10B shown in FIG. The layers 131 may be stacked in this order. Further, as in the perpendicular magnetic recording medium 10C shown in FIG. 1C, a plurality of ferromagnetic layers (131A to 131C) and dielectric magnetic layers (132A to 132C) may be laminated. In the perpendicular magnetic recording medium 10C shown in FIG. 1C, the stacking order of the ferromagnetic layer and the dielectric magnetic layer is not limited and can be stacked in an arbitrary order.

  Moreover, as shown to Fig.1 (a)-(c), the protective layer 14 can also be arrange | positioned on the outermost surface.

  The perpendicular magnetic recording medium is not limited to the underlayer 12 and the perpendicular recording layer 13 on the nonmagnetic substrate 11 and may include other layers. For example, as shown in FIG. 1D, an adhesion layer 15 and / or a backing layer 16 can be disposed between the nonmagnetic substrate 11 and the base layer 12. In addition to the above-mentioned layers, an arbitrary layer can be arranged.

  Each layer will be described below.

(Non-magnetic substrate)
The nonmagnetic substrate 11 is not particularly limited as long as it is a nonmagnetic substrate, and any substrate can be used. For example, Al alloy substrate such as Al-Mg alloy mainly composed of Al, normal soda glass, aluminosilicate glass, amorphous glass, silicon, titanium, ceramics, sapphire, quartz, various resins, etc. Can be used.

(Adhesion layer)
The adhesion layer 15 smoothes the surface of the nonmagnetic substrate 11 to improve the adhesion between the nonmagnetic substrate 11 and the underlayer 12, and alkaline ions from the nonmagnetic substrate 11 diffuse into the underlayer 12, It is possible to prevent the formation 12 from corroding.

  As the adhesion layer 15, a nonmagnetic metal material can be used, but an amorphous structure is desirable. By adopting an amorphous structure, it becomes a dense structure and has an excellent effect of preventing the diffusion of alkaline ions from the non-magnetic substrate 11, and the surface roughness (Ra) can be kept low, so that the flying height of the head is reduced. This is because the recording density can be further increased. As such a material, for example, CrTi, NiTa, AlTi alloy or the like can be preferably used.

(Lining layer)
The backing layer (soft magnetic backing layer) 16 can more firmly fix the magnetization direction of the perpendicular recording layer 13 in the direction perpendicular to the nonmagnetic substrate 11 and stabilize the reproduction signal.
The backing layer 16 is preferably made of a soft magnetic material. For example, the material of the backing layer 16 is a CoFe alloy (CoFeTaZr, CoFeZrNb, CoFeB, etc.), a FeCo alloy (FeCo, FeCoV, etc.), a CoZr alloy (CoZr, CoZrNb, etc.), a CoTa alloy (CoTa, CoTaZr, etc.), A material having soft magnetic properties such as an FeB alloy can be preferably used.

  It is particularly preferable that the backing layer 16 has an amorphous structure. Since the backing layer 16 has an amorphous structure, it is possible to prevent the surface roughness (Ra) of the surface of the perpendicular magnetic recording medium from increasing, to further reduce the flying height of the head, and to further increase the recording density. It is because it becomes. The structure of the backing layer 16 is not limited to a single soft magnetic layer. For example, an extremely thin nonmagnetic thin film such as Ru may be sandwiched between two soft magnetic layers, and an antiferromagnetic coupling may be provided between the soft magnetic layers. Is more preferable.

  The coercive force (Hc) of the backing layer 16 is not particularly limited, but is preferably 100 Oe or less, and more preferably 20 Oe or less. 1 Oe is 79 A / m. This is because, when the coercive force (Hc) of the backing layer 16 is in the above range, the reproduced waveform can be more reliably maintained in a so-called rectangular wave, which is preferable.

  The saturation magnetic flux density (Bs) of the backing layer 16 is not particularly limited, but is preferably 0.6T or more, and more preferably 1T or more. This is because when the saturation magnetic flux density (Bs) is in the above range, the reproduced waveform can be more reliably maintained as a rectangular wave, which is preferable.

  Further, the product (Bs · T) of the saturation magnetic flux density (Bs) of the backing layer 16 and the film thickness of the backing layer 16 is preferably 15 Tnm or more, and more preferably 25 Tnm or more. This is because when the product (Bs · T) of the saturation magnetic flux density and the film thickness of the backing layer 16 is within the above range, the reproduced waveform can be more reliably maintained in a so-called rectangular wave.

  The backing layer 16 is preferably magnetized in the radial direction parallel to the surface of the nonmagnetic substrate 11 without applying a magnetic field from the outside. This is because the so-called spike noise during reproduction can be particularly suppressed by restricting the magnetization direction of the backing layer 16.

  Since the backing layer 16 has a structure in which the magnetization of the backing layer 16 is oriented parallel to the surface of the nonmagnetic substrate and in the radial direction without applying a magnetic field from the outside, the backing layer 16 is, for example, nonmagnetic between two soft magnetic films. It is preferable to have a laminated structure provided with a metal film. This can be realized by generating a magnetic coupling (bias magnetic field HBias) between the upper and lower soft magnetism.

  The backing layer 16 is preferably a conductor. Thereby, when an electric field is applied during data writing, the backing layer 16 functions as a counter electrode, and therefore the area of the electric field applied to the perpendicular recording layer 13 can be reduced. As a result, the occupied area of one bit can be reduced and the recording density can be increased.

  In the case where the backing layer 16 is made of an insulator, when data is written by an electric field due to charge-up, the area of the electric field applied to the perpendicular recording layer 13 is increased, which may reduce the recording density. . For this reason, it is preferable that the backing layer 16 be a conductor as described above.

(Underlayer)
In the perpendicular magnetic recording medium of the present embodiment, an underlayer 12 that can control at least the vertical orientation of the film immediately above can be provided. For example, the underlayer 12 can control the orientation of the perpendicular recording layer.

  As described above, the underlayer 12 is provided on the nonmagnetic substrate 11, and for example, an adhesion layer 15, a backing layer 16, or the like can be disposed between the nonmagnetic substrate 11 and the underlayer 12. .

  The material of the underlayer 12 is not particularly limited. For example, a nonmagnetic material having an hcp structure (hexagonal close-packed structure), a nonmagnetic material having an fcc structure (face-centered cubic structure), a nonmagnetic material having an amorphous or microcrystalline structure, and the like. A magnetic material can be preferably used.

  Examples of nonmagnetic materials having an hcp structure include Ru, Re, CoCr alloys, RuCo alloys, and the like.

  Nonmagnetic materials having an fcc structure include, for example, Ni, Pt, Pd, Ti, Ni alloys (NiNb alloys, NiTa alloys, NiV alloys, NiW alloys, NiPt alloys, NiCr alloys, etc.), Pt Based alloys (such as PtCr based alloys), CoPd based alloys, AlTi based alloys, Mg based alloys and the like.

  Examples of the nonmagnetic material having an amorphous or microcrystalline structure include Ta, Hf, Zr, alloys containing these as main components, PdSi alloys, CrB alloys, CoB alloys, and the like.

  The underlayer 12 is not limited to a single layer structure, and may have a multilayer structure.

  When the underlayer 12 has a multilayer structure, the configuration of each layer is not particularly limited. For example, a nonmagnetic material layer having an fcc structure such as Pt or a Pt alloy or a nonmagnetic material having an hcp structure such as Ru or Re on a nonmagnetic material layer having an fcc structure such as a Ni-based alloy. It is preferable to provide a layer of material.

  In particular, it is more preferable to make the underlayer 12 multilayer and to provide a layer of a nonmagnetic material having an hcp structure on the perpendicular recording layer 13 side, since the perpendicular orientation and crystallinity of the perpendicular recording layer can be particularly improved.

  The thickness of the underlayer 12 is not particularly limited, but is preferably 5 nm or more and 40 nm or less, and more preferably 10 nm or more and 30 nm or less. This is because, by setting the thickness of the underlayer 12 within such a range, the perpendicular orientation of magnetization of the perpendicular recording layer 13 can be particularly strengthened, and the resolution of the reproduction signal can be further increased.

  By setting the thickness of the underlayer 12 to 5 nm or more, the crystal orientation of the perpendicular recording layer 13 can be further improved and the electromagnetic conversion characteristics can be improved. Further, by setting the thickness of the underlayer 12 to 40 nm or less, the particle diameter of the perpendicular recording layer 13 can be made more appropriate, so that the noise of the reproduction signal can be suppressed and the resolution can be sufficiently increased. And electromagnetic conversion characteristics can be improved.

  The underlayer 12 is preferably a conductor. Thus, when an electric field is applied during data writing, the underlayer 12 functions as a counter electrode, so that the area of the electric field applied to the perpendicular recording layer can be reduced. As a result, the occupied area of one bit can be reduced, and the recording density can be increased. In the case where the underlayer 12 is an insulator, when data is written by an electric field by charge-up, the area of the electric field applied to the perpendicular recording layer is expanded, and the recording density is lowered.

(Vertical recording layer)
As described above, in the perpendicular magnetic recording medium of this embodiment, the perpendicular recording layer 13 can include the ferromagnetic layer 131 and the dielectric magnetic layer 132 having both magnetism and dielectric properties.

  First, the ferromagnetic layer 131 will be described.

  The structure of the ferromagnetic layer 131 is not particularly limited, but preferably has a granular structure like the dielectric magnetic layer 132. Specifically, for example, it is preferable to have a magnetic crystal grain and a nonmagnetic grain boundary region surrounding the magnetic crystal grain.

  For this reason, the ferromagnetic material of the ferromagnetic layer 131 is preferably a material in which the magnetic crystal grains can easily have a structure (granular structure) in which the magnetic crystal grains are dispersed in the nonmagnetic grain boundary region.

  The magnetic crystal particles preferably contain Co and Pt, and more preferably contain Pt containing Co as a main component.

  In addition, as a material for the magnetic crystal grains of the ferromagnetic layer 131, for example, an ordered alloy of Co and Pt can be used. The ordered alloy of CoPt has a larger magnetic anisotropy constant (Ku) than a general magnetic material containing Co and Pt, and can suppress thermal fluctuation. For this reason, it is a material suitable for higher density recording in which the occupied area per bit must be reduced.

Examples of the ordered alloy of Co and Pt include 75Co25Pt <m-DO ₁₉ type>, 50Co50Pt <L1 type ₁ >, 20Co50Pt30Ni <L1 type ₁ >, and the like.

  In the case of the ordered alloy of Co and Pt, the content of Pt is not particularly limited, and is preferably set to an optimum content for obtaining the ordered alloy.

  Although the manufacturing method of an ordered alloy is not specifically limited, For example, it can form into a film with the target which has the composition mentioned above. In addition to the Ru and Re, the base layer 12 can be formed with three layers formed in the order of Cr, MgO and Pt, or two layers formed in the order of Ta and Pt. The isotropic constant (Ku) can be obtained.

  As the material of the ferromagnetic layer 131, for example, a material obtained by adding an oxide to a material that is a raw material of the above-described magnetic crystal particle (magnetic alloy) can be preferably used.

  Examples of the oxide include Si oxide, Ti oxide, W oxide, Cr oxide, Co oxide, Ta oxide, B oxide, Mg oxide, Ce oxide, Y oxide, Ni oxide, It is preferable to include at least one selected from Al oxide and Ru oxide. As will be described later, the oxide forms a nonmagnetic grain boundary region so as to surround the magnetic crystal grains. For this reason, it is preferable that the nonmagnetic grain boundary region contains the oxide.

  Examples of ferromagnetic materials to which these oxides are added include CoCrPt—Si oxide, CoCrPt—Ti oxide, CoCrPt—W oxide, CoCrPt—Cr oxide, CoCrPt—Co oxide, CoCrPt—Ta oxide, Examples thereof include CoCrPt—B oxide, CoCrPt—Ru oxide, CoRuPt—Si oxide, and CoCrPtRu—Si oxide.

  Further, when a ordered alloy of Co and Pt is used as the magnetic crystal particles, for example, an oxide is added to 75Co25Pt, 50Co50Pt, etc., so that the magnetic crystal particles become a ordered alloy of 25Co25Pt, 50Co50Pt. An oxide nonmagnetic grain boundary region is formed so as to surround the magnetic crystal grains.

  Here, an example in which one kind of oxide is added to the magnetic crystal particles as the ferromagnetic material has been described, but two or more kinds of oxides can be added simultaneously as described above.

  The average grain size of the magnetic crystal grains contained in the ferromagnetic layer 131 is preferably 3 nm or more and 12 nm or less, and more preferably 3 nm or more and 8 nm or less. The average particle diameter of the magnetic crystal particles can be calculated using a planar TEM observation image. For example, the particle diameter (equivalent circle diameter) is measured for 200 particles from an observation image of TEM, and the integrated value is 50%. The particle size at can be the average particle size.

  The average particle size of the magnetic crystal particles is preferably within the above range in order to obtain thermal stability. This is because it is preferable to set the average particle size of the magnetic crystal particles to 3 nm or more, thereby suppressing the influence of thermal fluctuation and maintaining the data more reliably. Further, it is preferable to set the average particle size of the magnetic crystal particles to 12 nm or less because a sufficient number of particles per bit can be secured and the SNR during reproduction can be increased.

  The content of the oxide present in the ferromagnetic layer 131 is preferably 3 mol% or more and 18 mol% or less, and preferably 6 mol% or more and 12 mol% or less with respect to the total mol calculated with the composition other than the oxide as one compound. More preferred. When the content of the oxide is in the above range, when the layer is formed, the oxide is precipitated around the magnetic crystal particles, so that the magnetic particles can be isolated and refined more uniformly throughout the layer. preferable. By controlling the content of the oxide present in the ferromagnetic layer 131 to 18 mol% or less, it is possible to prevent the oxide from remaining in the magnetic crystal particles and the oxide from being deposited above and below the magnetic crystal particles. It is preferable because the orientation and crystallinity of the ferromagnetic layer 131 can be sufficiently maintained. Further, it is preferable to set the oxide content to 3 mol% or more because the magnetic particles can be sufficiently separated and refined, and deterioration of electromagnetic conversion characteristics can be suppressed.

  When the magnetic crystal particles contained in the ferromagnetic layer 131 are a material containing Pt containing Co as a main component, the Pt content is preferably 8 at% or more and 25 at% or less, more preferably 10 at% or more and 22 at% or less. preferable. In the case where the magnetic crystal particles are made of a material containing Co as a main component and containing Pt, it is preferable that the Pt content is in the above range because an electromagnetic conversion characteristic suitable for high-density recording can be obtained. By setting the content of Pt to 8 at% or more, it is possible to suppress destabilization due to heat with respect to data retention. That is, the influence of thermal fluctuation can be suppressed. In addition, when the Pt content is 25 at% or less, the occurrence of stacking faults in the magnetic crystal grains can be particularly suppressed. That is, since it is possible to suppress a decrease in crystallinity, it is possible to suppress deterioration of electromagnetic conversion characteristics. In the case where the magnetic crystal grains are ordered alloys of Co and Pt, the Pt content is not particularly limited.

  In addition, when the magnetic crystal grains in the ferromagnetic layer 131 have an hcp structure, if the Pt content increases, an fcc structure layer may be formed in the hcp structure. And in some cases, electromagnetic conversion characteristics may be deteriorated by impairing uniaxial anisotropy. However, when the Pt content is in the above range, the fcc structure layer is more formed in the hcp structure. This is preferable because it can be surely suppressed.

  The ferromagnetic material of the ferromagnetic layer 131 may be Cr, Si, B, C, Ta, Mo, Nd, W, Nb, Sm, Tb, Ru, Re, Cu, in addition to the magnetic crystal grains and the oxides described above, for example. One or more elements selected from can be included. By including the above elements, the miniaturization of the magnetic crystal particles can be promoted or the crystallinity and orientation can be improved, and electromagnetic conversion characteristics suitable for higher density recording can be obtained.

  The total content of the above elements is preferably 24 at% or less for the substances contained in the ferromagnetic layer 131. This is because by setting it to 24 at% or less, it is possible to suppress the formation of a crystal structure other than the hcp structure in the magnetic particles, and to particularly suppress deterioration of electromagnetic conversion characteristics. The content of the element is more preferably 20 at% or less from the viewpoint of further suppressing deterioration of electromagnetic conversion characteristics.

  Although the ferromagnetic layer 131 has been described so far, the ferromagnetic layer 131 is not limited to one layer, and may have a multilayer structure of two or more layers.

  The total film thickness of the ferromagnetic layer 131 included in the perpendicular recording layer 13 is preferably 5 nm or more and 20 nm or less, and more preferably 8 nm or more and 17 nm or less.

  The ferromagnetic layer 131 is preferably a conductor. Thus, when an electric field is applied during data writing, the ferromagnetic layer 131 functions to suppress diffusion by drawing the electric field, so that the area of the electric field applied to the perpendicular recording layer can be reduced. As a result, the occupied area of one bit can be reduced, and the recording density can be increased.

  Next, the dielectric magnetic layer will be described.

  The dielectric magnetic layer 132 has both magnetism and dielectric properties.

  Here, magnetism means ferromagnetism (hard magnetism or soft magnetism) or diamagnetism.

  The dielectric magnetic layer 132 preferably has ferromagnetism and dielectricity or ferroelectricity, and more preferably has ferromagnetism and ferroelectricity.

The material is not particularly limited constituting the dielectric magnetic layer 132, dielectric magnetic layer _preferably includes a _{(Bi 1-a Ba a)} FeO 3. In this case, the substitution rate a preferably satisfies 0.05 ≦ a ≦ 0.8, and by setting the substitution rate a within such a range, a particularly suitable material having both ferromagnetism and ferroelectricity can be obtained. . The substitution rate a more preferably satisfies 0.1 ≦ a ≦ 0.5.

BiFeO ₃ is known as a dielectric material, but by replacing part of Bi of the BiFeO ₃ material with Ba, particularly suitable ferromagnetism and dielectric properties are exhibited. By setting the substitution rate a in this case within the range of 0.05 or more and 0.8 or less, it is possible to form a suitable material having both particularly suitable ferromagnetism and ferroelectricity as described above. The method for forming the dielectric magnetic layer 132 containing (Bi _1-a Ba _a ) FeO ₃ is not particularly limited, but can be formed by, for example, a sputtering method using a target having the same composition material as the above composition. However, in order to prevent oxygen vacancies in the formed film, it is preferable to use a target with an increased oxygen concentration.

In addition, the dielectric magnetic layer 132 may include Bi (Fe _1-b Mn _b ) O ₃ . In this case, the substitution rate b preferably satisfies 0.01 ≦ b ≦ 0.5, and by setting the substitution rate b in such a range, a material having both particularly suitable ferromagnetism and ferroelectricity can be obtained. As described above, BiFeO ₃ is known as a dielectric magnetic material. By substituting a part of Fe of this material with Mn, ferromagnetism and dielectric properties are exhibited, but the substitution rate b is 0.01. By setting it to 0.5 or less, a material having both more suitable ferromagnetism and ferroelectricity can be formed. The substitution rate b more preferably satisfies 0.05 ≦ b ≦ 0.4.

The method for forming the dielectric magnetic layer 132 containing Bi (Fe _1-b Mn _b ) O ₃ (0.01 ≦ b ≦ 0.5) is not particularly limited. For example, a target having the same composition material as that described above is used. The sputtering method can be used. However, in order to prevent oxygen vacancies in the formed film, it is preferable to use a target with an increased oxygen concentration.

The dielectric magnetic layer 132 can include (Bi _1-ac Ba _a La _c ) (Fe _1-b Mn _b ) O ₃ having the characteristics of the two materials. In this case, the substitution rate a satisfies 0 ≦ a ≦ 0.8, b satisfies 0.01 ≦ b ≦ 0.5, c satisfies 0 ≦ c ≦ 0.8, and 0.05 ≦ a + c ≦ 0.8. In this range, a particularly suitable material having both ferromagnetism and ferroelectricity can be formed. It is more preferable that the substitution rates a, b, and c satisfy 0.1 ≦ a + c ≦ 0.5 and 0.05 ≦ b ≦ 0.4.

In addition, the dielectric magnetic layer 132 may include (Bi _1-ac Ba _a La _c ) (Fe _1-bd Mn _b Ti _d ) O ₃ . The substitution rates a, b, c, and d in this case are 0 ≦ a ≦ 0.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.8, 0.01 ≦ d ≦ 0.5, 0 ≦ In addition, it is preferable to satisfy a + c ≦ 0.8 and 0.01 ≦ b + d ≦ 0.5, and by setting such ranges, it is possible to form a material having both particularly suitable ferromagnetism and ferroelectricity. The substitution rates a, b, c and d are more preferably 0.1 ≦ a + c ≦ 0.5 and 0.05 ≦ b + d ≦ 0.4.

In addition, the dielectric magnetic layer 132 can include (Bi _1-c La _c ) FeO ₃ . In this case, the substitution rate c is preferably 0.01 ≦ c ≦ 0.8. By setting the substitution ratio c within this range, a material having both particularly suitable ferromagnetism and ferroelectricity can be formed.

In addition, the dielectric magnetic layer 132 is formed of M-Fe-O, M-Fe-Mn-O, M-Co-O, M-Ni-O, M-Co-Fe-O, M-Fe. -Ni-O, M-Co-Mn-O, M-Ni-Mn-O, M-V-O (M is selected from rare earth elements, Bi, Y, alkaline earth elements) One or more kinds of elements). For example, BiLaFeO ₃ , BiNdMnO ₃ , BiFeCoO ₃ , BiPrFeO _3, etc.

  As described above, the material used for the dielectric magnetic layer 132 may be a material having diamagnetic characteristics and dielectric characteristics. In that case, it should be noted that the polarity of the written data string and the data string at the time of reproduction are reversed.

  The thickness of the dielectric magnetic layer 132 is not particularly limited, but is preferably 50 nm or less. By setting the thickness of the dielectric magnetic layer 132 to 50 nm or less, enlargement of crystal grains in the dielectric magnetic layer 132 can be suppressed, and the surface roughness of the dielectric magnetic layer 132 can be reduced. For this reason, since the surface shape of the obtained magnetic recording medium can be made smooth, the flying height of the head can be lowered, and the electromagnetic conversion characteristics can be improved.

  More preferably, the thickness of the dielectric magnetic layer 132 is 20 nm or less. In particular, when the dielectric magnetic layer 132 is provided on the surface layer side of the perpendicular magnetic recording medium, the distance between the ferromagnetic layer 131 and the reproducing element of the head is increased by the thickness of the dielectric magnetic layer 132. For this reason, the above range is more preferable in order to sufficiently shorten the distance between the head and the ferromagnetic layer 131.

  The lower limit value of the thickness of the dielectric magnetic layer is not particularly limited, but is preferably 2 nm or more, for example, and more preferably 3 nm or more. When the thickness is 2 nm or more, crystal grains are easily formed in the dielectric magnetic layer, which is preferable.

  The average particle size of the crystal particles contained in the dielectric magnetic layer 132 is not particularly limited, but is preferably 3 nm or more and 12 nm or less in order for the crystal particles to obtain sufficient dielectric properties and magnetic properties. The average particle diameter (average crystal particle diameter) of the crystal particles can be calculated using a planar TEM observation image. Calculation of the average particle diameter of the crystal particles by the planar TEM observation image can be performed by the method described above.

  It is preferable to set the average particle size of the crystal particles to 3 nm or more because thermal fluctuation can be suppressed and data can be more reliably maintained. In addition, it is preferable that the average particle size of the crystal particles is 12 nm or less because the number of particles per bit can be sufficiently secured and the SNR during reproduction can be increased.

  As described above, it is preferable that the dielectric magnetic layer 132 has a crystal grain and an amorphous grain boundary region surrounding the crystal grain.

  Moreover, it is preferable that the particles constituting the ferromagnetic layer 131 and the particles constituting the dielectric magnetic layer 132 form a columnar crystal (columnar structure) continuous in the thickness direction. A specific configuration example will be described with reference to FIG. FIG. 2 schematically shows a structure in which the ferromagnetic layer 131 and the dielectric magnetic layer 132 are stacked, and the stacking order is not limited to such a form. Note that description of other layers is omitted. As shown in FIG. 2, it is preferable that the magnetic crystal grains 1312 of the ferromagnetic layer 131 and the crystal grains 1322 of the dielectric magnetic layer 132 form a columnar crystal that is continuous in the thickness direction.

  Since the magnetic crystal particles 1312 and the crystal particles 1322 form columnar crystals, the crystallinity of the crystal grains of the dielectric magnetic layer 132 can be increased, and the crystal grain size can be decreased. Therefore, it is possible to constitute a magnetic layer having an excellent SNR.

  As described above, in the perpendicular magnetic recording medium of this embodiment, it is preferable that the ferromagnetic layer 131 also has a granular structure. When the ferromagnetic layer 131 has a granular structure, by stacking the dielectric magnetic layer 132 on the ferromagnetic layer 131, it is easy to form columnar crystals in which the particles constituting the ferromagnetic layer and the dielectric magnetic layer are continuous in the thickness direction. Become. In addition, the crystal grain size of the crystal grains in each layer can be reduced.

  The perpendicular recording layer 13 of the perpendicular magnetic recording medium according to the present embodiment includes a ferromagnetic layer 131 and a dielectric magnetic layer 132, and can be configured by stacking the ferromagnetic layer 131 and the dielectric magnetic layer 132. The number of ferromagnetic layers 131 and dielectric magnetic layers 132 included in the perpendicular recording layer 13 is not particularly limited. For example, as shown in FIG. 1C, the perpendicular recording layer 13 may have a structure in which two or more ferromagnetic layers 131 and two or more dielectric magnetic layers 132 are stacked. Further, a structure in which one is a single layer and only the other is provided in a plurality of layers may be employed. Further, the perpendicular recording layer 13 may be configured to include one ferromagnetic layer 131 and one dielectric magnetic layer 132.

  Further, the stacking order of the ferromagnetic layer 131 and the dielectric magnetic layer 132 is not particularly limited. For example, the ferromagnetic layer 131 can be disposed on the nonmagnetic substrate 11 side, and the dielectric magnetic layer 132 can be laminated on the upper surface thereof. In this case, the ferromagnetic layer 131 preferably has a granular structure including magnetic crystal grains 1312 and nonmagnetic grain boundary regions 1311. When the ferromagnetic layer 131 has such a structure, the crystal grain 1322 and the amorphous grain boundary region 1321 of the dielectric magnetic layer 132 are easily grown on the magnetic crystal grain 1312 and the nonmagnetic grain boundary region 1311, respectively. Can be made. For this reason, the dielectric magnetic layer 132 can also easily have a granular structure. With such a structure, noise of the dielectric magnetic layer 132 can be suppressed, and electromagnetic conversion characteristics are improved. Further, since the crystallinity and orientation of the ferromagnetic layer 131 are improved by the effect of orientation control by the underlayer 12, the crystallinity and orientation of the dielectric magnetic layer 132 are also improved, and as a result, the electromagnetic conversion characteristics are further improved. can get.

  Further, since the ferromagnetic layer 131 is on the nonmagnetic substrate 11 side, it functions as a counter electrode when data is written by an electric field, so that the area of the electric field applied to the perpendicular recording layer can be reduced. As a result, the occupied area of one bit can be reduced, and the recording density can be increased.

  In addition, since the dielectric magnetic layer 132 is on the surface layer side, the physical distance to the recording / reproducing head is reduced, and the increase in crystal grain size is suppressed by the effect of the granularity of the dielectric magnetic layer 132. For this reason, the surface of the perpendicular magnetic recording medium can be flattened, and the distance between the electric field writing element provided in the recording / reproducing head and the dielectric magnetic layer 132 can be made closer, so that writing to the dielectric magnetic layer 132 is facilitated. As a result, it is easy to increase the recording density of the perpendicular magnetic recording medium.

  On the other hand, the dielectric magnetic layer 132 may be on the nonmagnetic substrate 11 side. For example, the same effect as the granular structure of the ferromagnetic layer 131 can be obtained by providing an alignment layer having a granular structure on the perpendicular recording layer 13 side of the underlayer 12. That is, the orientation adjusting layer in which the grain boundary layer is formed so as to surround the particles allows the crystal grains of the dielectric magnetic layer 132 to be formed on the amorphous particles in the orientation adjusting layer on the crystalline particles in the orientation adjusting layer. An amorphous structure of the dielectric magnetic layer 132 can be grown on the grain boundary layer. Therefore, also in this case, the dielectric magnetic layer 132 can have a granular structure.

  The configuration of the orientation adjusting layer is not particularly limited, but may be configured by a material in which an oxide is added to the material forming the underlayer 12, for example.

  Further, magnetic crystal grains 1312 in the ferromagnetic layer 131 are formed on the crystal grains 1322 in the dielectric magnetic layer 132, and nonmagnetic grains in the ferromagnetic layer 131 are formed on the amorphous grain boundary region 1321 in the dielectric magnetic layer 132. A field region 1311 can grow. For this reason, the enlargement of particles in the perpendicular recording layer can be suppressed and uniformity can be maintained, and as a result, an effect of improving electromagnetic conversion characteristics can be obtained.

  Further, since the ferromagnetic layer 131 is on the surface layer side, the physical distance from the recording / reproducing head is reduced, the signal output at the time of reproduction can be increased, and a reproduced signal having a good SNR can be obtained.

  Further, when data is written by an electric field, the electric field passes through the ferromagnetic layer 131 and is applied to the dielectric magnetic layer 6. At this time, since the ferromagnetic layer 131 is on the surface side, the spread of the electric field can be suppressed, and in addition to the counter electrode effect of the underlayer 12, the area of the electric field applied to the perpendicular recording layer can be further reduced. it can. As a result, the area occupied by one bit is reduced, and the recording density can be further increased.

(Protective layer)
The protective layer 14 is for protecting the perpendicular magnetic recording medium from damage caused by contact between the recording / reproducing head and the perpendicular magnetic recording medium. Although the configuration of the protective layer 14 is not particularly limited, for example, a carbon film, a SiO ₂ film, or the like can be used as the protective layer 14, and a carbon film can be preferably used. Although the formation method of the protective layer 14 is not specifically limited, For example, it can form by sputtering method, plasma CVD method, ion beam method, etc. In particular, the ion beam method can be preferably used. The thickness of the protective layer 14 is not particularly limited, but is preferably 1 nm or more and 10 nm or less, and more preferably 1.5 nm or more and 5 nm or less.

  Next, a configuration example of the method for manufacturing the perpendicular magnetic recording medium of the present embodiment will be described.

  The method for manufacturing a perpendicular magnetic recording medium according to this embodiment relates to a method for manufacturing a perpendicular magnetic recording medium having at least one underlayer and a perpendicular recording layer on a nonmagnetic substrate. The perpendicular recording layer can include a ferromagnetic layer and a dielectric magnetic layer having both magnetic and dielectric properties, and having crystal grains and an amorphous grain boundary region surrounding the crystal grains.

  In addition, the manufacturing method of the perpendicular magnetic recording medium of this embodiment can have the following processes, for example.

  A nonmagnetic substrate preparation process for preparing a nonmagnetic substrate.

  An underlayer forming step of forming at least one underlayer on at least one surface side of the nonmagnetic substrate;

  A perpendicular recording layer forming step of forming a perpendicular recording layer on at least one surface side of the nonmagnetic substrate;

  The perpendicular recording layer forming step includes a ferromagnetic layer forming step for forming a ferromagnetic layer, and a dielectric magnetism having both magnetic and dielectric properties, and crystal grains and an amorphous grain boundary region surrounding the crystal grains. A dielectric magnetic layer forming step of forming the layer can be included.

  Moreover, it is not limited to the said process, Furthermore, if necessary, for example, an adhesion layer forming process for forming an adhesion layer, a backing layer forming process for forming a backing layer, a protective layer forming process for forming a protective layer, etc. It can also be implemented.

  Since the configurations of the nonmagnetic substrate 11 and the underlayer 12 are as already described, description thereof is omitted here. Further, as described above, the adhesion layer 15, the backing layer 16 and the like can be arbitrarily formed.

  In addition, about a base layer formation process, it can implement by sputtering method, for example using the target which has the target composition mentioned above. Similarly, when the adhesion layer 15 or the backing layer is formed, the film can be formed by a sputtering method using a target corresponding to the target composition.

  Hereinafter, a method for forming the perpendicular recording layer 13 will be mainly described.

  First, the ferromagnetic layer will be described.

  Among the perpendicular recording layer forming steps for forming the perpendicular recording layer 13, the ferromagnetic layer forming step for forming the ferromagnetic layer 131 is performed by applying the material constituting the magnetic crystal grains and the oxide on the substrate as described above. It can implement by supplying to. Specifically, for example, it can be carried out by a sputtering method or the like using a target containing the material constituting the magnetic crystal particles described above and an oxide.

  The ferromagnetic layer preferably has magnetic crystal grains and a nonmagnetic grain boundary region surrounding the magnetic crystal grains as described above.

  Next, the dielectric magnetic layer 132 will be described.

  In the method for manufacturing a perpendicular magnetic recording medium of this embodiment, the perpendicular recording layer 13 preferably has a structure in which a ferromagnetic layer 131 and a dielectric magnetic layer 132 having a granular structure are laminated. In particular, the magnetic crystal grains 1312 of the ferromagnetic layer 131 and the crystal grains 1322 of the dielectric magnetic layer 132 are preferably arranged so as to be stacked. That is, it is preferable that the magnetic crystal grains of the ferromagnetic layer and the crystal grains of the dielectric magnetic layer form a columnar crystal that is continuous in the thickness direction. At the same time, the nonmagnetic grain boundary region 1311 of the ferromagnetic layer 131 and the amorphous grain boundary region 1321 of the dielectric magnetic layer 132 are preferably disposed so as to be laminated.

  The dielectric magnetic layer forming step for forming the dielectric magnetic layer is preferably performed with the substrate temperature set lower than the crystallization temperature of the material included in the dielectric magnetic layer 132. Here, the substrate temperature refers to the temperature of the deposition target substrate on which the dielectric magnetic layer 132 is formed, and means the temperature of the substrate including the underlayer 12 formed on the nonmagnetic substrate 11. doing.

  The crystallization temperature of the material included in the dielectric magnetic layer 132 is a temperature at which the material included in the dielectric magnetic layer 132 is crystallized even on an amorphous substrate.

  This is because, if the substrate temperature is equal to or higher than the crystallization temperature of the material contained in the dielectric magnetic layer 132, for example, when the dielectric magnetic layer 132 is formed on the upper surface of the ferromagnetic layer 131, the nonmagnetic grain boundary region of the ferromagnetic layer 131. In some cases, a crystal is generated in a corresponding portion on 1311 and the dielectric magnetic layer 132 does not have a granular structure. For this reason, the crystal grains 1322 of the dielectric magnetic layer 132 are enlarged, and the portion on the nonmagnetic grain boundary region 1311 has a different crystal orientation, leading to an increase in noise, resulting in a deterioration in flatness and electromagnetic conversion characteristics. This is because it is not preferable.

  Further, it is preferable to apply a bias to the nonmagnetic substrate 11 when forming the dielectric magnetic layer 132.

  Even if the substrate temperature is lower than the crystallization temperature of the material included in the dielectric magnetic layer 132, the dielectric magnetic layer 132 may form crystal grains on the upper surface of the highly oriented portion, for example, the magnetic crystal grains of the ferromagnetic layer. . However, the crystallinity of crystal grains formed in such a temperature range may not be sufficient. For this reason, when forming the dielectric magnetic layer 132 as described above, it is preferable to apply a bias to the nonmagnetic substrate 11 to increase the crystallinity of the crystal grains.

  Under such conditions, for example, the dielectric magnetic layer 132 is formed on the ferromagnetic layer 131 having a granular structure or on the orientation adjusting layer, so that the dielectric magnetic layer can easily be crystal grains and an amorphous material surrounding the crystal grains. And a grain boundary region. That is, it is preferable that the dielectric magnetic layer 132 can easily have a granular structure.

  The substrate temperature at the time of forming the dielectric magnetic layer 132 is more preferably in a range that does not reach the crystallization temperature from a temperature that is 300 degrees lower than the crystallization temperature of the material included in the dielectric magnetic layer 132. Furthermore, it is particularly preferable that the substrate temperature is in the range of 300 degrees lower than the crystallization temperature to 50 degrees lower than the crystallization temperature. That is, Tc−300 ≦ Ts <Tc, where Tc is the crystallization temperature of the material included in the dielectric magnetic layer 132 and Ts is the substrate temperature of the nonmagnetic substrate 11 when forming the dielectric magnetic layer 132. Is more preferable, and Tc−300 ≦ Ts ≦ Tc−50 is particularly preferable.

  By setting the substrate temperature when forming the dielectric magnetic layer 132 within the temperature range, the dielectric magnetic layer 132 can easily have a granular structure in which the crystal grain 1322 is surrounded by the amorphous grain boundary region 1321.

  When the dielectric magnetic layer 132 is formed, when the substrate temperature (Ts) is set to a temperature lower than the crystallization temperature (Tc-300) by 300 degrees, the dielectric magnetic layer can be applied even if the nonmagnetic substrate 11 is biased. 132 crystals may not be obtained. In this case, the dielectric magnetic layer 132 is not preferable because the dielectric properties and magnetic properties cannot be obtained.

Examples of the material included in the dielectric magnetic layer include a BiFeO ₃ -based material, a (Bi _1-a Ba _a ) FeO ₃ -based material, a Bi (Fe _b Mn _1-b ) O ₃ -based material, and (Bi _{1-a -c Ba a La c) (Fe} 1-b Mn b) O 3 based _{material, (Bi 1-a-c} Ba a La c) (Fe 1-b-d Mn b Ti d) O 3 based material In the case of using a (Bi _1-c La _c ) FeO ₃ -based material, the substrate temperature is preferably 300 ° C. or higher and lower than 600 ° C. In particular, when the above-described material is used as the material included in the dielectric magnetic layer, the substrate temperature is more preferably 300 ° C. or higher and 550 ° C. or lower.

  When a bias (Bias) is applied to the nonmagnetic substrate, the bias is preferably an AC bias, and particularly preferably a high frequency bias. This is because in the case of DC (direct current) bias, the effect of applying a bias to the nonmagnetic substrate 11 may not be sufficiently obtained due to the charge-up of the dielectric magnetic layer 132. The frequency applied to the nonmagnetic substrate 11 is not particularly limited, but the frequency is preferably 0.1 kHz or more and 2.5 GHz or less, and more preferably 150 kHz or more and 2.45 GHz or less from a practical viewpoint. .

  Hereinafter, a case where the dielectric magnetic layer 132 is formed on the ferromagnetic layer 131 will be described as an example.

  As described above, for example, a substance containing Co as a main component and containing Pt can be used as the magnetic crystal particle 1312 included in the ferromagnetic layer 131, and the hcp crystal has a c-axis perpendicular to the substrate surface ( 002) Orientation. On the other hand, the dielectric magnetic layer 132 preferably has a (111) orientation. Thereby, the directions of dielectric anisotropy and magnetic anisotropy coincide with the direction perpendicular to the substrate surface. Therefore, data can be recorded in the perpendicular recording layer 13 by controlling the magnetic field applied perpendicular to the substrate surface.

  At this time, it is preferable that the lattice constant of the magnetic crystal grains 1312 of the ferromagnetic layer 131 and the lattice constant of the crystal grains 1322 of the dielectric magnetic layer 132 be close to each other. With this configuration, the ferromagnetic layer 131 functions as if it were the orientation control layer of the dielectric magnetic layer 132. This facilitates the growth of crystal grains 1322 of the dielectric magnetic layer 132 on the magnetic crystal grains 1312 of the ferromagnetic layer 131.

  According to the study by the inventors, when the dielectric magnetic layer 132 is formed under such conditions, a bias is applied to the nonmagnetic substrate 11 so that the crystallization temperature of the material included in the dielectric magnetic layer 132 is less than the crystallization temperature. It was confirmed that crystal grains of the dielectric magnetic layer 132 having high crystallinity can be obtained. For this reason, for example, a columnar crystal in which the magnetic crystal grains of the ferromagnetic layer and the crystal grains of the dielectric magnetic layer are continuous in the thickness direction can be more reliably configured.

  On the other hand, the nonmagnetic grain boundary region 1311 of the ferromagnetic layer 131 is formed by precipitation of an oxide when, for example, an oxide is contained in a ferromagnetic material as described above. For this reason, it does not have a clear crystal structure. For example, when the dielectric magnetic layer 132 is formed on the ferromagnetic layer 131, a part of the dielectric magnetic layer 132 corresponding to the nonmagnetic grain boundary region 1311 of the ferromagnetic layer 131 is less than the crystallization temperature. Becomes amorphous and does not exhibit dielectric and magnetic properties. Under such conditions, even if an AC bias is applied to the nonmagnetic substrate 11, it is experimentally confirmed that, of the dielectric magnetic layer 132, the upper surface portion of the nonmagnetic grain boundary region 1311 of the ferromagnetic layer 131 does not form crystal grains. It was confirmed.

  As described above, in the method for manufacturing a perpendicular magnetic recording medium according to the present embodiment, the dielectric magnetic layer 132 is made of, for example, a material whose substrate temperature is included in the dielectric magnetic layer 132 on the ferromagnetic layer 131 having a granular structure. It is preferable to form the film at a temperature lower than the crystallization temperature. Furthermore, it is preferable to apply an AC bias to the nonmagnetic substrate 11 during film formation. Thereby, the dielectric magnetic layer 132 can be easily formed into a structure having crystal grains and an amorphous grain boundary layer surrounding the crystal grains, that is, a granular structure.

  Further, according to this method, the magnetic crystal grains 1312 constituting the ferromagnetic layer 131 and the crystal grains 1322 constituting the dielectric magnetic layer 132 can constitute a columnar crystal continuous in the thickness direction. By adopting such a configuration, it becomes possible to increase the crystallinity of the magnetic crystal grains 1312 of the ferromagnetic layer 131 and to suppress the enlargement of the crystal grain size, so that the SNR is excellent. In addition, the perpendicular recording layer 13 having a smooth surface can be formed.

  Here, although the case where the dielectric magnetic layer 132 is formed on the ferromagnetic layer 131 has been described as an example, the dielectric magnetic layer 132 can also be formed on the nonmagnetic substrate 11 side as described above. At this time, when the dielectric magnetic layer 132 has a granular structure, it can be formed, for example, on the orientation adjusting layer as described above. In this case, since the orientation adjusting layer functions in the same manner as the ferromagnetic layer 131, the dielectric magnetic layer 132 can be easily formed in a granular structure by performing film formation under the above-described conditions.

[Second Embodiment]
In this embodiment, a configuration example of a vertical recording / reproducing apparatus will be described.

  The perpendicular recording / reproducing apparatus of this embodiment can be a perpendicular recording / reproducing apparatus provided with the perpendicular magnetic recording medium described in the first embodiment.

  FIG. 3 shows an example of a perpendicular recording / reproducing apparatus 30 using the perpendicular magnetic recording medium described in the first embodiment. The perpendicular recording / reproducing apparatus shown in FIG. 3 includes the perpendicular magnetic recording medium 31 described in the first embodiment. Further, a medium driving unit 32 that rotates the perpendicular magnetic recording medium 31, a recording / reproducing head 33 that records and reproduces information on the perpendicular magnetic recording medium 31, and a relative movement of the recording / reproducing head 33 with respect to the perpendicular magnetic recording medium 31. The head driving unit 34 and the recording / reproducing signal processing system 35 can be configured.

  The recording / reproducing signal processing system 35 can process data input from the outside and send the recording signal to the recording / reproducing head 33, and can process the reproducing signal from the recording / reproducing head 33 and send the data to the outside. It has become.

  The recording / reproducing head 33 used in the vertical recording / reproducing apparatus 30 of this embodiment can be provided with a recording element and a reproducing element independently. The recording element can be an electric field writing element using a needle electrode, the reproducing element can be a GMR element using a giant magnetoresistance effect (GMR), a TuMR element using a tunnel effect, or the like.

  Since the perpendicular recording / reproducing apparatus 30 of the present embodiment uses the perpendicular magnetic recording medium described in the first embodiment, the SNR of the data recording / reproducing signal is high and the perpendicular recording / reproducing apparatus has a high density. Can do.

  Specific examples will be described below, but the present invention is not limited to these examples.

[Example 1]
In this example, the perpendicular magnetic recording medium shown in FIG. 1A was formed by the following procedure. As described below, in the perpendicular magnetic recording medium of this example, an adhesion layer is provided between the nonmagnetic substrate 11 and the underlayer 12, and a lubricating film is provided on the upper surface of the protective layer 14, as shown in FIG. Is further provided.

  As the non-magnetic substrate 11, a cleaned glass substrate (manufactured by Konica Minolta, outer diameter: 2.5 inches) was prepared.

And after accommodating the said glass substrate in the film-forming chamber of a magnetron sputtering apparatus (Anelva company make: model C-3040), and exhausting the inside of the film-forming chamber until it reaches the ultimate vacuum degree of 1 × 10 ⁻⁵ Pa, Ar gas was introduced to adjust the internal pressure of the chamber to 0.8 Pa. Next, an adhesion layer 15 having a thickness of 10 nm was formed on a glass substrate using a target having a Ti content of 50 at% and the balance being Cr (hereinafter, the composition is referred to as “50Cr-50Ti”).

  Next, a 94Ni-6W layer having a film thickness of 5 nm and a film thickness using a Ru target with a W content of 6 at%, the balance being made of Ni (hereinafter referred to as “94Ni-6W”), and a film thickness And a Ru layer having a thickness of 10 nm were formed in that order. Furthermore, after setting the pressure in the chamber to 6 Pa, a Ru target was used to form a film with a thickness of 10 nm, and these were used as the underlayer 12 (orientation control layer).

90 (70Co10Cr20Pt) -10 (10), which is a target including 10 mol% of Cr, 10 mol% of Pt content, 90 mol% of an alloy made of Co, and 10 mol% of Cr ₂ O ₃ on the underlayer 12. A ferromagnetic layer 131 was formed using Cr ₂ O ₃ ). At the time of film formation, the pressure in the chamber was set to 3 Pa, and the ferromagnetic layer 131 was formed to have a film thickness of 15 nm.

Next, a dielectric magnetic layer 132 was formed. The substrate is heated to 400 ° C., and Bi (Fe _0.9 Mn _0.1 ) O ₃ , which is a compound alloy having a Bi: Fe: Mn: O content molar ratio of 1: 0.9: 0.1: _3. A 12 nm thick dielectric magnetic layer was formed using a target. Note that the crystallization temperature for crystallization on an amorphous substrate of Bi (Fe _0.9 Mn _0.1 ) O ₃ is 650 ° C.

  Further, when the dielectric magnetic layer 132 was formed, 5 W of VHF bias was applied to the nonmagnetic substrate 11. The VHF bias referred to here is a high frequency bias of 40.68 MHz.

  Next, a DLC film having a thickness of 3 nm was formed as the protective layer 14 by an ion beam method, and a tetraol-based lubricant was applied as a lubricating film to a thickness of 2 nm to produce a perpendicular magnetic recording medium.

  The obtained perpendicular magnetic recording medium was evaluated as follows.

(Surface roughness)
When the surface roughness of the lubricating film surface of the perpendicular magnetic recording medium was observed with an AFM, the surface roughness (Ra) was 0.25 nm.

(SNR, OW characteristics)
The recording medium characteristics of the perpendicular magnetic recording medium were measured and evaluated by using a read / write analyzer (US GUZIK TECHNICNIC ENTRPRISES model: RW1632) and a spin stand (US GUZIK TECHNICICAL ENTRISES model: S1701MR).

  In the measurement, the electromagnetic conversion characteristics of the perpendicular magnetic recording medium were measured under the conditions of a measurement radius of 21 mm, a rotational speed of 5400 rpm, a maximum signal frequency of 514.02 MHz (linear recording density of 2139 kilobits per inch), and a writing voltage of 1.5V. The recording / reproducing head used for the measurement has an electrode needle having a tip diameter of 10 nm as a writing element and a TMR thin film as a reproducing element. For data writing, a data string is converted into an electric polarity and a voltage is applied from the electrode needle. The method of applying was used.

  As a result of the evaluation of the recording medium characteristics, the SNR was 20.7 dB.

  Overwrite (OW) writes a signal of 1070 kFCI, then overwrites the signal of 143 kFCI, extracts a high frequency component by a frequency filter, and evaluates the data writing ability by the residual ratio. A value of 40.0 dB is obtained. Obtained.

(Evaluation of growth state of grains in perpendicular recording layer)
Furthermore, the microstructure of the dielectric magnetic layer 132 was observed using a transmission electron microscope (TEM). When observed on a plane perpendicular to the nonmagnetic substrate 11 (cross-sectional TEM observation), the crystal grains of the dielectric magnetic layer 132 are formed in a columnar shape, and adjacent columnar crystal grains are divided by an amorphous grain boundary layer. The observed structure was clearly observed. Further, it was confirmed that the crystal particles 1322 of the dielectric magnetic layer 132 were stacked with substantially the same width on the magnetic crystal particles 1312 of the ferromagnetic layer 131 to form a continuous columnar structure. In other words, in the perpendicular recording layer 13, it was confirmed that the magnetic crystal particles 1312 of the ferromagnetic layer 131 and the crystal particles 1322 of the dielectric magnetic layer 132 constituted a columnar crystal continuous in the thickness direction. Therefore, it can be seen that the ferromagnetic layer 131 and the dielectric magnetic layer 132 have a granular structure. The dielectric magnetic layer 132 having a granular structure means that the crystal grain 1322 is surrounded by the amorphous grain boundary region 1321. The fact that the ferromagnetic layer 131 and the dielectric magnetic layer 132 have such a structure is hereinafter referred to as a columnar structure.

(Average particle size of crystal grains of dielectric magnetic layer)
Next, a granular structure in which the crystal grain 1322 was surrounded by the amorphous grain boundary region 1321 could be observed in the dielectric magnetic layer 132 by observation from the plane direction (plane TEM). The average grain size of the crystal grains 1322 of the dielectric magnetic layer 132 estimated from the planar TEM image was 6.5 nm.

  In the measurement, the particle diameter (equivalent circle diameter) of 200 particles was measured from the TEM observation image, and the particle diameter at an integrated value of 50% was defined as the average particle diameter.

[Examples 2 to 17]
A perpendicular magnetic recording medium was fabricated in the same manner as in Example 1 except that the dielectric magnetic layer and the ferromagnetic layer were changed to the materials and film thicknesses shown in Table 1. The obtained perpendicular magnetic recording medium was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[Comparative Example 1]
A perpendicular magnetic recording medium was manufactured in the same manner as in Example 1 except that the ferromagnetic layer 131 and the dielectric magnetic layer 132 were formed by the following procedure.

  On the underlayer 12, a ferromagnetic layer 131 is formed by using a target of 66Co10Cr20Pt4B, which is an alloy made of Cr content of 10at%, Pt content of 20at%, B content of 4at% and the balance Co, and the pressure in the chamber is 3Pa. The film was formed so as to have a thickness of 15 nm.

A target of Bi (Fe _0.9 Mn _0.1 ) O ₃ which is an alloy having a Bi: Fe: Mn: O content molar ratio of 1: 0.9: 0.1: 3 by heating the substrate to 400 ° C. Was used to form a dielectric magnetic layer 132 having a thickness of 12 nm.

  On the dielectric magnetic layer 132, a DLC film having a thickness of 3 nm is formed as the protective layer 14 by the ion beam method in the same manner as in the first embodiment, and a tetraol-based lubricant is formed to a thickness of 2 nm as the lubricating film. The perpendicular magnetic recording medium was produced by coating.

  The obtained perpendicular magnetic recording medium was evaluated in the same manner as in Example 1.

(Surface roughness)
When the surface roughness of the perpendicular magnetic recording medium obtained in the same manner as in Example 1 was observed using an AFM, the surface roughness (Ra) was 0.92 nm.

(SNR, OW characteristics)
The SNR and OW characteristics were evaluated under the same conditions as in Example 1.

  The SNR was 13.5 dB. The overwrite (OW) was 38.0 dB.

(Evaluation of growth state of grains in perpendicular recording layer)
Further, the microstructure of the dielectric magnetic layer 132 was observed using a transmission electron microscope (TEM). When observed on a plane perpendicular to the nonmagnetic substrate 11 (cross-sectional TEM observation), the crystal grains of the dielectric magnetic layer 132 were irregular in shape, and the boundary between the crystal grains and the crystal grains could not be clearly observed. Further, the crystal particles 1322 of the dielectric magnetic layer 132 are formed regardless of the magnetic crystal particles 1312 of the ferromagnetic layer 131. Hereinafter, such a structure is referred to as an irregular shape.

  Next, the grain boundary portion of the crystal grain 1322 of the dielectric magnetic layer 132 could not be clearly observed by observation from the plane direction (plane TEM). Further, the dielectric magnetic layer 132 did not have a structure having crystal grains and an amorphous grain boundary region surrounding the crystal grains. The average grain size of the crystal grains of the dielectric magnetic layer 132 estimated from the planar TEM image was 14.5 nm.

[Comparative Examples 2 to 4]
A perpendicular magnetic recording medium was prepared in the same manner as in Comparative Example 1 except that the ferromagnetic layer 131 and the dielectric magnetic layer 132 were changed to the materials and film thicknesses shown in Table 1.

  The obtained magnetic recording medium was evaluated in the same manner as in Comparative Example 1. The results are shown in Table 1.

  In addition, when the dielectric magnetic layer 132 was observed for the samples of Comparative Examples 2 to 4 by observation from the planar direction (planar TEM), any sample had a structure having an amorphous grain boundary region surrounding the crystal grains and the crystal grains. It was not.

  From the comparison between Examples 1 to 17 and Comparative Examples 1 to 4, an excellent magnetic recording medium can be obtained by using a magnetic material having a granular structure for the ferromagnetic layer 131 and laminating the dielectric magnetic layer 132 thereon. I was able to confirm.

  In the first to seventeenth embodiments, the dielectric magnetic layer 132 takes on the granular structure of the ferromagnetic layer 131, and the dielectric magnetic layer 132 has a granular structure in which the crystal grain is surrounded by the amorphous grain boundary layer. This is because the magnetic noise from is reduced.

  Further, comparing the results of Examples 1 to 4, it can be seen that a high SNR can be obtained by setting the thickness of the dielectric magnetic layer 132 to 50 nm or less, more preferably 20 nm or less.

  This is because the diameter of the crystal grains is reduced by reducing the film thickness of the dielectric magnetic layer 132, magnetic noise is suppressed, and reproduction is performed by shortening the distance between the ferromagnetic layer 131 and the recording / reproducing head. This is because the electromagnetic conversion characteristics are improved by increasing the signal strength.

From the results of Example 1 and Examples 5 to 8, it can be seen that by using Bi (Fe _1-b Mn _b ) O ₃ for the dielectric magnetic layer 132, the characteristics superior to BiFeO ₃ are exhibited. Moreover, it can be seen that by setting b to a range of 0.01 ≦ b ≦ 0.5, the electromagnetic conversion characteristics are particularly good.

From the results of Example 5 and Example 9-12, by using the dielectric magnetic layer 132 _{(Bi 1-a Ba a)} FeO 3, it is found to exhibit excellent characteristics than BiFeO _3, BaFeO 3. It can also be seen that the electromagnetic conversion characteristics are good when a is in the range of 0.05 ≦ a ≦ 0.8.

From the results of Examples 13 to 17, as a dielectric magnetic _{layer, (Bi 1-a Ba a} ) (Fe 1-b Mn b) O 3 to it can be seen that the use as a dielectric magnetic layer. On the other hand, it can be seen that the film thickness of the ferromagnetic layer is more preferably 5 nm or more and 20 nm or less.

[Examples 18 to 39]
A perpendicular magnetic recording medium was manufactured in the same manner as in Example 1 except that the ferromagnetic layer 131 and the dielectric magnetic layer 132 were changed to the materials shown in Table 2. The obtained perpendicular magnetic recording medium was evaluated in the same manner as in Example 1. The results are shown in Table 2.

  From the results of Examples 18 to 21, it can be seen that the amount of oxide added to the ferromagnetic layer 131 is preferably 18 mol% or less. By setting the oxide added to the ferromagnetic layer 131 to 18 mol% or less, the oxide can be reliably segregated in the nonmagnetic grain boundary region 1311 and can be prevented from remaining in the magnetic crystal grain 1312, so that the magnetic characteristics are improved. It was confirmed that it could be sufficiently increased.

  Further, from the results of Examples 18 and 35, it is found that the oxide added to the ferromagnetic layer 131 is preferably 3 mol% or more. By setting the oxide added to the ferromagnetic layer 131 to 3 mol% or more, the nonmagnetic grain boundary region 1311 can be sufficiently formed and the enlargement of the magnetic particles can be particularly suppressed, so that the magnetic characteristics can be improved. .

  From the results of Examples 22 to 24, it is found that the total amount of elements added to the ferromagnetic layer 131 excluding Co, Pt, and oxide is preferably 24 at% or less. It was confirmed that by adding the elements added to the ferromagnetic layer 131 to 24 at% or less excluding Co, Pt, and oxide, the orientation of the magnetic crystal grains 1312 can be improved and the magnetic characteristics can be improved. .

  Further, from the results of Table 2, the ferromagnetic layer has various oxides (Si oxide, Ti oxide, W oxide, Cr oxide, Co oxide, Ta oxide, B oxide, Mg oxide, Ce Oxide, Y oxide, Ni oxide, Al oxide and Ru oxide) and various elements (Cr, Si, B, C, Ta, Mo, Nd, W, It was confirmed that one or more elements selected from Nb, Sm, Tb, Ru, Re, and Cu) can be added.

From the results of Examples _{36~39, (Bi 1-a-} c Ba a La c) (Fe 1-b-d Mn b Ti d) O 3 by _using, BiFeO _3, BaFeO _3, better than It can be seen that the characteristics are shown.

[Example 40]
A perpendicular magnetic recording medium was fabricated in the same manner as in Example 1 except that the perpendicular recording layer 13 was configured as shown in Table 3.

  In the present embodiment, the first recording layer of the perpendicular recording layer 13 is a first ferromagnetic layer, the second layer is a second ferromagnetic layer, and the third layer is a dielectric magnetic layer. A procedure for forming each layer will be described.

After the film formation up to the underlayer 12 was performed in the same manner as in Example 1, the first ferromagnetic layer was formed on the underlayer 12. The first ferromagnetic layer includes 90 (74 Co 10 Cr 16 Pt) -10 (Cr, containing 10 mol% of Cr, 10 mol% of Pt content, 90 mol% of an alloy made of Co, and 10 mol% of an oxide made of Cr ₂ O _{3. A} film was formed using a ₂ O ₃ ) target. During film formation, the pressure in the chamber was set to 3 Pa, and the film thickness of the first ferromagnetic layer was 5 nm.

Following the first ferromagnetic layer, a Cr content of 8 at%, a Pt content of 18 at%, the remaining alloy of 88 mol% of Co, an oxide of Cr ₂ O ₃ of 8 mol%, and an oxide of SiO ₂ containing 4 mol%, was formed a second ferromagnetic layer using a target of _{88 (74Co8Cr18Pt) -8 (Cr 2} O 3) -4 (SiO 2). During film formation, the pressure in the chamber was set to 3 Pa, and the film thickness of the second ferromagnetic layer was 10 nm.

Next, the substrate is heated to 400 ° C., and Bi _0.6 Ba _0.4 FeO ₃ , which is a compound alloy having a Bi: Ba: Fe: O content molar ratio of 0.6: 0.4: 1: _3. Using this target, a dielectric magnetic layer 132 having a thickness of 12 nm was formed. When forming the dielectric magnetic layer 132, a VHF bias of 5 W was applied to the nonmagnetic substrate 11. The VHF bias referred to here is a high frequency bias of 40.68 MHz.

  After the formation of the dielectric magnetic layer 132, a DLC film having a thickness of 3 nm was formed as a protective layer by an ion beam method in the same manner as in Example 1, and a lubricating film was applied by 2 nm to produce a perpendicular magnetic recording medium.

  The obtained perpendicular magnetic recording medium was evaluated in the same manner as in Example 1. The results are shown in Table 3.

[Examples 41 to 44]
A magnetic recording medium was manufactured in the same manner as in Example 40 except that the configuration of the perpendicular recording layer 13 was changed to the materials and configurations shown in Table 3. The obtained magnetic recording medium was evaluated in the same manner as in Example 1. The results are shown in Table 3.

  In addition, the first layer to the fourth layer in Table 3 were formed in order from the base layer 12 side. Table 3 shows whether each layer is a ferromagnetic layer or a dielectric magnetic layer as the properties of the layer.

[Example 45]
As the non-magnetic substrate 11, a cleaned glass substrate (manufactured by Konica Minolta, outer diameter: 2.5 inches) was prepared.

And after accommodating the said glass substrate in the film-forming chamber of a magnetron sputtering apparatus (Anelva company make: model C-3040), and exhausting the inside of the film-forming chamber until it reaches the ultimate vacuum degree of 1 × 10 ⁻⁵ Pa, Ar gas was introduced to adjust the internal pressure of the chamber to 0.8 Pa. Next, an adhesion layer 15 having a thickness of 10 nm was formed on the glass substrate using a 50Cr-50Ti target.

Next, using a 94Ni-6W (W content 6 at%, remaining Ni) target and a Ru target, a 94Ni-6W layer having a thickness of 5 nm and a Ru layer having a thickness of 10 nm in that order. A film was formed. Then, after setting the pressure in the chamber to 6 Pa, a Ru layer having a thickness of 10 nm was formed using a Ru target. Further, 90 mol% of Ru, an oxide of SiO ₂ containing 10 mol%, was formed a film of thickness 10nm serving as an alignment control layer using a target of _{90 (Ru) -10 (SiO 2} ). These 94Ni-6W layer, Ru layer, Ru layer, and 90 (Ru) -10 (SiO ₂ ) layer were used as the underlayer 12 (orientation control layer).

Next, the substrate is heated to 400 ° C. and is a compound alloy having a Bi: Ba: Fe: O content molar ratio of 0.8: 0.2: 1: 3 (Bi _0.8 Ba _0.2 ). Using a FeO ₃ target, a dielectric magnetic layer having a film thickness of 15 nm was formed. When forming the dielectric magnetic layer 132, a VHF bias of 5 W was applied to the nonmagnetic substrate 11. The VHF bias referred to here is a high frequency bias of 40.68 MHz.

The dielectric magnetic layer 132 has a Cr content of 8 at%, a Pt content of 18 at%, the remaining alloy of 92 mol% of Co and an oxide of B ₂ O ₃ of 8 mol%. 92 (74Co8Cr18Pt) -8 (B _A ferromagnetic layer 131 was formed using a ₂ O ₃ ) target. When forming the ferromagnetic layer, the pressure in the chamber was set to 3 Pa and the film thickness of the ferromagnetic layer 131 was set to 15 nm.

  Next, in the same manner as in Example 1, a DLC film having a thickness of 3 nm was formed as a protective layer by an ion beam method, and a lubricating film was applied by 2 nm to produce a perpendicular magnetic recording medium.

  The obtained perpendicular magnetic recording medium was evaluated in the same manner as in Example 1. The results are shown in Table 3.

[Example 46]
A magnetic recording medium was produced in the same manner as in Example 45 except that the perpendicular recording layer was changed to the materials and configurations shown in Table 3. The obtained magnetic recording medium was evaluated in the same manner as in Example 1. The results are shown in Table 3.

[Comparative Example 5]
As shown in Table 3, a perpendicular magnetic recording medium was manufactured in the same manner as in Example 45 except that only the first dielectric magnetic layer 132 was used as shown in Table 3.

Specifically, after the film formation up to the underlayer 12 was performed in the same manner as in Example 45, the nonmagnetic substrate 11 was heated to 400 ° C., and the molar ratio of Bi: Ba: Fe: O was 0.8: 0.2. A dielectric magnetic layer 132 was formed using a target of (Bi _0.8 Ba _0.2 ) FeO ₃ , which is a 1: 3 compound alloy. Note that the film was formed so that the thickness of the dielectric magnetic layer 132 was 15 nm, and when the dielectric magnetic layer 132 was formed, a VHF bias of 5 W was applied to the nonmagnetic substrate 11. The VHF bias referred to here is a high frequency bias of 40.68 MHz.

  Then, in the same manner as in Example 1, a DLC film having a thickness of 3 nm was formed as a protective layer by an ion beam method, and a lubricating film was applied by 2 nm to produce a perpendicular magnetic recording medium.

  The obtained magnetic recording medium was evaluated in the same manner as in Example 1. The results are shown in Table 3.

[Example 47]
A perpendicular magnetic recording medium was manufactured in the same manner as in Example 1 except that the configuration of the perpendicular recording layer 13 was changed to the following configuration.

  After forming the underlayer 12, the substrate was heated to 400 ° C., and a plurality of ferromagnetic layers 131 and dielectric magnetic layers 132 were alternately stacked to form the perpendicular recording layer 13.

The ferromagnetic layer 131 includes a Cr content of 8 at%, a Pt content of 18 at%, a balance of 92 mol% of an alloy composed of Co, and 8 mol% of an oxide composed of B ₂ O ₃ , 92 (74Co8Cr18Pt) -8 (B ₂ O _The film was formed using the target ₃ ).

Dielectric magnetic layer 132, Bi: Ba: Fe: the molar ratio of the content of O is 0.8: 0.2: 1: 3 of compounds _alloy targets _{(Bi 0.8} Ba 0.2) FeO ₃ Used to form a film.

  Then, the ferromagnetic layer 131 and the dielectric magnetic layer 132 were alternately stacked by 1.5 nm, and the perpendicular recording layer 13 having a total thickness of 30 nm was formed. At this time, the pressure in the chamber was 3 Pa, and a VHF bias of 5 W was applied to the nonmagnetic substrate 11 when the ferromagnetic layer 131 and the dielectric magnetic layer 132 were formed. The VHF bias referred to here is a high frequency bias of 40.68 MHz.

  After the perpendicular recording layer 13 was formed, a DLC film having a thickness of 3 nm was formed as a protective layer by an ion beam method in the same manner as in Example 1, and a lubricating film was applied by 2 nm to produce a perpendicular magnetic recording medium.

  The obtained perpendicular magnetic recording medium was evaluated in the same manner as in Example 1. The results are shown in Table 4.

[Example 48]
As the non-magnetic substrate 11, a cleaned glass substrate (manufactured by Konica Minolta, outer diameter: 2.5 inches) was prepared.

And after accommodating the said glass substrate in the film-forming chamber of a magnetron sputtering apparatus (Anelva company make: model C-3040), and exhausting the inside of the film-forming chamber until it reaches the ultimate vacuum degree of 1 × 10 ⁻⁵ Pa, Ar gas was introduced to adjust the internal pressure of the chamber to 0.8 Pa. Next, an adhesion layer 15 of 10 nm was formed on a glass substrate using a 50Cr-50Ti target having a Ti content of 50 at% and the balance being Cr.

  Then, using a Cr target, an MgO target, and a Pt target, the Cr layer has a thickness of 10 nm, the MgO layer has a thickness of 10 nm, and the Pt layer has a thickness of 20 nm. The Cr layer, the MgO layer, and the Pt layer were used as the underlayer 12 (orientation control layer).

Then, the substrate was heated to 400 ° C., Pt content 50at%, 90 _mol% of the alloy and the balance _Co, including oxide of _{B 2 O 3 10mol%, 90} (50Co50Pt) -10 (B 2 O 3 ) To form a ferromagnetic layer 131. During the film formation, the pressure in the chamber was set to 3 Pa, and the film thickness of the ferromagnetic layer 131 was set to 15 nm.

Next, a Bi (Fe _0.9 Mn _0.1 ) O ₃ target, which is a compound alloy having a Bi: Fe: Mn: O content molar ratio of 1: 0.9: 0.1: 3, is used to form a film. A dielectric magnetic layer 132 having a thickness of 20 nm was formed. When forming the dielectric magnetic layer 132, a VHF bias of 5 W was applied to the nonmagnetic substrate 11. The VHF bias referred to here is a high frequency bias of 40.68 MHz.

  Next, as in the case of Example 1, a DLC film having a thickness of 3 nm was formed as a protective layer by an ion beam method, and a lubricating film was applied by 2 nm to produce a perpendicular magnetic recording medium.

  The obtained perpendicular magnetic recording medium was evaluated in the same manner as in Example 1. The results are shown in Table 4.

In this example, the X-ray diffraction of a perpendicular magnetic recording medium produced by an X-ray diffractometer (X-ray source: Cu) was measured (θ / 2θ method in the range of 15 ° to 80 °). Diffraction peaks derived from the type ₁ (111), (222), and (333) planes were observed. This resulted in it is confirmed that 50Co50Pt ferromagnetic layer 131 is set to L1 ₁ of the ordered alloy.

  From the results of Examples 40 to 46 and 47, it can be seen that by laminating the ferromagnetic layer 131 and the dielectric magnetic layer 132, good SNR and OW characteristics were obtained.

  From the results of Examples 45 and 46, it can be seen that even with the structure in which the dielectric magnetic layer 132 is provided on the nonmagnetic substrate 11 side, good characteristics in terms of SNR and OW characteristics were obtained. In addition, when Examples 45 and 46 are compared with Comparative Example 5, the dielectric magnetic layer 132 alone does not exhibit sufficient characteristics, and it is excellent by forming the ferromagnetic layer 131 on the dielectric magnetic layer 132. It was confirmed that SNR and OW characteristics were exhibited.

  From the results of Example 48, it was confirmed that good characteristics were obtained even when an ordered alloy was used for the ferromagnetic layer.

[Example 49]
As the non-magnetic substrate 11, a cleaned glass substrate (manufactured by Konica Minolta, outer diameter: 2.5 inches) was prepared.

And after accommodating the said glass substrate in the film-forming chamber of a magnetron sputtering apparatus (Anelva company make: model C-3040), and exhausting the inside of the film-forming chamber until it reaches the ultimate vacuum degree of 1 × 10 ⁻⁵ Pa, Ar gas was introduced to adjust the internal pressure of the chamber to 0.8 Pa. Next, an adhesion layer 15 of 10 nm was formed on a glass substrate using a 50Cr-50Ti target having a Ti content of 50 at% and the balance being Cr.

  Next, using a 94Ni-6W target and a Ru target with a W content of 6 at% and the balance being Ni, a 94Ni-6W layer with a thickness of 5 nm and a Ru layer with a thickness of 10 nm Films were formed in order. Furthermore, after setting the pressure in the chamber to 6 Pa, a Ru target was used to form a film with a thickness of 10 nm, and these were used as the underlayer 12 (orientation control layer).

90 (70Co10Cr20Pt) -10 (10), which is a target including 10 mol% of Cr, 10 mol% of Pt content, 90 mol% of an alloy made of Co, and 10 mol% of Cr ₂ O ₃ on the underlayer 12. A ferromagnetic layer 131 was formed using Cr ₂ O ₃ ). At the time of film formation, the pressure in the chamber was set to 3 Pa, and the ferromagnetic layer 131 was formed to have a film thickness of 15 nm.

Next, a dielectric magnetic layer 132 was formed. The substrate is heated to 350 ° C., and is a compound alloy having a Bi: Ba: Fe: Mn: O content molar ratio of 0.7: 0.3: 0.9: 0.1: 3 (Bi _{0.7 Ba 0.3) (Fe 0.9 Mn 0.1} ) the _{O 3} using a target, thereby forming a dielectric magnetic layer having a thickness of 14 nm. Note that the crystallization temperature for crystallization on an amorphous substrate of (Bi _0.7 Ba _0.3 ) (Fe _0.9 Mn _0.1 ) O ₃ is 650 ° C.

  Further, when the dielectric magnetic layer 132 was formed, 5 W of VHF bias was applied to the nonmagnetic substrate 11. The VHF bias referred to here is a high frequency bias of 40.68 MHz.

  Next, a DLC film having a thickness of 3 nm was formed as the protective layer 14 by an ion beam method, and a tetraol-based lubricant was applied as a lubricating film to a thickness of 2 nm to produce a perpendicular magnetic recording medium.

  The obtained perpendicular magnetic recording medium was evaluated in the same manner as in Example 1. The results are shown in Table 5.

[Examples 50 and 51, Comparative Examples 6 to 8]
A magnetic recording medium was manufactured in the same manner as in Example 49 except that the film formation conditions for the dielectric magnetic layer 132 were the conditions shown in Table 5. The obtained magnetic recording medium was evaluated in the same manner as in Example 1. The results are shown in Table 5.

  When the microstructure of the dielectric magnetic layer 132 was observed for the samples of Comparative Examples 6 and 7 using a transmission electron microscope (TEM), no crystal particles were observed in the dielectric magnetic layer. The structure had no surrounding amorphous grain boundary region. In addition, the sample of Comparative Example 8 did not have a structure in which crystal grains were precipitated in the entire dielectric magnetic layer and had an amorphous grain boundary region surrounding the crystal grains.

  From the results of Table 5, it can be seen that it is preferable to set the substrate temperature when forming the dielectric magnetic layer within the range of crystallization temperature −300 ° C. or more and less than the crystallization temperature and to apply the VHF bias to the substrate. By forming the dielectric magnetic layer under such conditions, it can be seen that the dielectric magnetic layer has a structure having crystal grains and an amorphous grain boundary region surrounding the crystal grains, and excellent characteristics can be obtained.

[Example 52]
As the non-magnetic substrate 11, a cleaned glass substrate (manufactured by Konica Minolta, outer diameter: 2.5 inches) was prepared.

And after accommodating the said glass substrate in the film-forming chamber of a magnetron sputtering apparatus (Anelva company make: model C-3040), and exhausting the inside of the film-forming chamber until it reaches the ultimate vacuum degree of 1 × 10 ⁻⁵ Pa, Ar gas was introduced to adjust the internal pressure of the chamber to 0.8 Pa. Next, an adhesion layer 15 of 10 nm was formed on a glass substrate using a 50Cr-50Ti target having a Ti content of 50 at% and the balance being Cr.

  Next, a backing layer was formed using a 91Co5Zr4Nb target and a Ru target having a Zr content of 5 at%, an Nb content of 4 at%, and the balance being Co. Specifically, the backing layer was formed using the 91Co5Zr4Nb target, the Ru target, and the 91Co5Zr4Nb target in this order. Thus, a 91Co5Zr4Nb layer having a thickness of 30 nm, a Ru layer having a thickness of 0.8 nm, and a 91Co5Zr4Nb layer having a thickness of 30 nm were laminated in this order to form a backing layer.

  Next, using a 94Ni-6W target and a Ru target with a W content of 6 at% and the balance being Ni, a 94Ni-6W layer with a thickness of 5 nm and a Ru layer with a thickness of 10 nm Films were formed in order. Furthermore, after setting the pressure in the chamber to 6 Pa, a Ru target was used to form a film with a thickness of 10 nm, and these were used as the underlayer 12 (orientation control layer).

90 (70Co10Cr20Pt) -10 (10), which is a target including 10 mol% of Cr, 10 mol% of Pt content, 90 mol% of an alloy made of Co, and 10 mol% of Cr ₂ O ₃ on the underlayer 12. A ferromagnetic layer 131 was formed using Cr ₂ O ₃ ). At the time of film formation, the pressure in the chamber was set to 3 Pa, and the ferromagnetic layer 131 was formed to have a film thickness of 15 nm.

Next, a dielectric magnetic layer 132 was formed. The substrate is heated to 400 ° C., and Bi (Fe _0.9 Mn _0.1 ) O ₃ , which is a compound alloy having a Bi: Fe: Mn: O content molar ratio of 1: 0.9: 0.1: _3. A 12 nm thick dielectric magnetic layer was formed using a target. Note that the crystallization temperature for crystallization on an amorphous substrate of Bi (Fe _0.9 Mn _0.1 ) O ₃ is 650 ° C.

  Further, when the dielectric magnetic layer 132 was formed, 5 W of VHF bias was applied to the nonmagnetic substrate 11. The VHF bias referred to here is a high frequency bias of 40.68 MHz.

Next, a DLC film having a thickness of 3 nm was formed as the protective layer 14 by an ion beam method, and a tetraol-based lubricant was applied as a lubricating film to a thickness of 2 nm to produce a perpendicular magnetic recording medium.
The obtained magnetic recording medium was evaluated in the same manner as in Example 1. The results are shown in Table 6.

[Examples 53 and 54]
A magnetic recording medium was produced in the same manner as in Example 52 except that the backing layer and the dielectric magnetic layer were changed to the materials and structures shown in Table 6. The obtained magnetic recording medium was evaluated in the same manner as in Example 1. The results are shown in Table 6.

  From a comparison between Example 1 and Examples 52 to 54, it can be seen that a backing layer can be provided under the foundation layer. It can also be seen that the effect of improving the magnetic properties can be obtained by providing the backing layer. This is the effect that the resolution of the signal is improved because the rectangularity of the reproduced waveform is improved by the backing layer and the effect of the counter electrode is added to facilitate the drawing of the electric field.

10A to 10D, 31 Perpendicular magnetic recording medium 11 Nonmagnetic substrate 12 Underlayer 13 Perpendicular recording layer 131 Ferromagnetic layer 132 Dielectric magnetic layer 1311 Nonmagnetic grain boundary region 1312 Magnetic crystal grain 1321 Amorphous grain boundary region 1322 Crystal grain 30 Perpendicular recording Playback device

Claims (17)

On the nonmagnetic substrate, it has at least one underlayer and a perpendicular recording layer,
The perpendicular recording layer is
A ferromagnetic layer;
A perpendicular magnetic recording medium having a magnetic property and a dielectric property, and a dielectric magnetic layer having crystal grains and an amorphous grain boundary region surrounding the crystal grains.   The perpendicular magnetic recording medium according to claim 1, wherein the ferromagnetic layer has magnetic crystal grains and a nonmagnetic grain boundary region surrounding the magnetic crystal grains.   The perpendicular magnetic recording medium according to claim 2, wherein the magnetic crystal grains of the ferromagnetic layer and the crystal grains of the dielectric magnetic layer form a columnar crystal that is continuous in the thickness direction.   The perpendicular magnetic recording medium according to claim 2, wherein the magnetic crystal grains include Co and Pt.   The nonmagnetic grain boundary region includes Si oxide, Ti oxide, W oxide, Cr oxide, Co oxide, Ta oxide, B oxide, Mg oxide, Ce oxide, Y oxide, Ni oxide. 5. The perpendicular magnetic recording medium according to claim 2, comprising at least one oxide selected from an oxide, an Al oxide, and a Ru oxide. The perpendicular magnetic recording medium according to claim ₁ , wherein the dielectric magnetic layer includes (Bi _1−a Ba _a ) FeO ₃ (0.05 ≦ a ≦ 0.8). The perpendicular magnetic recording medium according to claim ₁ , wherein the dielectric magnetic layer includes Bi (Fe _1-b Mn _b ) O ₃ (0.01 ≦ b ≦ 0.5). The dielectric magnetic layer is made of (Bi _1-ac Ba _a La _c ) (Fe _1-b Mn _b ) O ₃ (0 ≦ a ≦ 0.8, 0.01 ≦ b ≦ 0.5, 0 ≦ c The perpendicular magnetic recording medium according to any one of claims 1 to 5, including ≦ 0.8 and 0.05 ≦ a + c ≦ 0.8. The dielectric magnetic _{layer, (Bi 1-a-c} Ba a La c) (Fe 1-b-d Mn b Ti d) O 3 (a and c are 0 ≦ a ≦ 0.8,0 ≦ c ≦ 0 .8 and 0 ≦ a + c ≦ 0.8, b and d are 0 ≦ b ≦ 0.5, 0.01 ≦ d ≦ 0.5 and 0.01 ≦ b + d ≦ 0.5. The perpendicular magnetic recording medium according to claim 1, wherein the perpendicular magnetic recording medium is included. 6. The perpendicular magnetic recording medium according to claim ₁ , wherein the dielectric magnetic layer includes (Bi _1-c La _c ) FeO ₃ (0.01 ≦ c ≦ 0.8).   11. The perpendicular magnetic recording medium according to claim 1, wherein the perpendicular recording layer has a structure in which two or more ferromagnetic layers and two or more dielectric magnetic layers are laminated. On the nonmagnetic substrate, it has at least one underlayer and a perpendicular recording layer,
The perpendicular recording layer is
A ferromagnetic layer;
A method of manufacturing a perpendicular magnetic recording medium, comprising a dielectric magnetic layer having both magnetic properties and dielectric properties, and having crystal grains and an amorphous grain boundary region surrounding the crystal grains. A nonmagnetic substrate preparation step of preparing the nonmagnetic substrate;
An underlayer forming step of forming at least one underlayer on at least one surface side of the nonmagnetic substrate;
A perpendicular recording layer forming step of forming the perpendicular recording layer on at least one surface side of the non-magnetic substrate,
The perpendicular recording layer forming step includes
A ferromagnetic layer forming step of forming the ferromagnetic layer;
A dielectric magnetic layer forming step of forming the dielectric magnetic layer having both magnetic and dielectric properties, the crystal grains, and the amorphous grain boundary region surrounding the crystal grains;
The method for manufacturing a perpendicular magnetic recording medium according to claim 12, comprising:   14. The method of manufacturing a perpendicular magnetic recording medium according to claim 12, wherein the dielectric magnetic layer is formed with a substrate temperature lower than a crystallization temperature of a material included in the dielectric magnetic layer.   The method of manufacturing a perpendicular magnetic recording medium according to claim 12, wherein an AC bias is applied to the nonmagnetic substrate when forming the dielectric magnetic layer. The ferromagnetic layer has magnetic crystal grains and a non-magnetic grain boundary region surrounding the magnetic crystal grains;
The perpendicular recording layer is
The perpendicular magnetic recording medium according to claim 12, wherein the magnetic crystal grains of the ferromagnetic layer and the crystal grains of the dielectric magnetic layer form a columnar crystal that is continuous in the thickness direction. Production method.   A perpendicular recording / reproducing apparatus comprising the perpendicular magnetic recording medium according to claim 1.