Magnetic recording medium, method of manufacturing magnetic recording medium, and magnetic storage device

Abstract

To provide a magnetic recording medium in which surface recording density is further improved by stably maintaining a state where a granular structure is formed inside a granular magnetic layer.SOLUTION: A substrate, an underlayer, a first magnetic layer, and a second magnetic layer in this order, the first magnetic layer including magnetic grains having a L10 structure, and the second magnetic layer including magnetic grains having a L10 structure and a granular structure having a grain boundary part containing hexagonal boron nitride, the (111) planes of the magnetic grains included in the first magnetic layer are covered with aluminum nitride at the interface with the second magnetic layer, the magnetic grains included in the second magnetic layer are epitaxially grown from the (001) planes of the magnetic grains included in the first magnetic layer, and the magnetic grains included in the first magnetic layer and the magnetic grains included in the second magnetic layer are columnar crystals penetrating the first magnetic layer and the second magnetic layer, respectively.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a magnetic recording medium, a method for manufacturing a magnetic recording medium, and a magnetic storage device. [Background technology]

[0002] In recent years, the thermally assisted recording method or microwave assisted recording method, which records by irradiating near-field light or microwaves to the magnetic recording medium and locally heating it, has achieved a data rate of 2 Tbit / inch. 2 It is attracting attention as a next-generation recording method that can achieve a high surface recording density.

[0003] Using such an assisted recording magnetic head, it is possible to easily record on a magnetic recording medium with a coercive force of several tens of kOe at room temperature. The magnetic layer of the magnetic recording medium contains magnetic particles with a high magnetocrystalline anisotropy constant (Ku), for example. Magnetic particles with a high magnetocrystalline anisotropy constant (Ku) can be miniaturized while maintaining thermal stability, increasing the coercive force at room temperature.

[0004] As magnetic particles with a high magnetocrystalline anisotropy constant (Ku), for example, Fe-Pt alloy particles (Ku: up to 7 × 10 6 J / m 3 ), Co-Pt alloy particles (Ku: up to 5 × 10 6 J / m 3 Magnetic particles having an L10 structure such as ZnO, ZnO, and ZnO are known.

[0005] As an example of a magnetic layer using magnetic particles having an L10 structure, Non-Patent Document 1 discloses a magnetic layer with a granular structure in which FePt magnetic particles having an L10 structure are covered with layers of hexagonal boron nitride. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] BSD Ch. S. Varaprasad et al., AIP Advances, 13, 035002(2023) Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, it is desirable to further improve the areal recording density of magnetic recording media. To achieve this, it is important to further reduce the particle size of the magnetic particles contained in the magnetic layer and further increase the anisotropy of the magnetic particles.

[0008] As such a magnetic layer, a granular structure magnetic layer (hereinafter simply referred to as "FePt-hBN granular magnetic layer") has been proposed, which contains FePt magnetic grains oriented in the (001) direction in an L10 structure and hexagonal boron nitride at the grain boundaries.

[0009] Hexagonal boron nitride has a layered structure in which the (001) planes are stacked parallel to one another, but it is easy to form grain boundaries between the FePt magnetic particles, which allows the FePt magnetic particles to have smaller particle sizes. Furthermore, because hexagonal boron nitride has low reactivity with the FePt magnetic particles, it does not inhibit the ordering of the magnetic particles. It is preferable that such hexagonal boron nitride be formed so that its (001) plane surrounds the side surfaces of the FePt magnetic particles.

[0010] However, in conventional FePt-hBN granular magnetic layers, the magnetic grains and the grain boundaries tend to be separated and layered, often failing to form a granular structure. Furthermore, the grain boundary components, such as BN, often do not crystallize sufficiently and remain amorphous. Therefore, even if a magnetic layer with a granular structure (also called a granular magnetic layer) is used, there is a problem that the areal recording density of the magnetic recording medium may not be improved.

[0011] An object of one aspect of the present invention is to provide a magnetic recording medium in which a granular magnetic layer stably maintains a state in which a granular structure is formed inside, and in which areal recording density is further improved. [Means for solving the problem]

[0012] The above objectives can be achieved by the following:

[0013] (1) A magnetic recording medium having a substrate, an underlayer, a first magnetic layer, and a second magnetic layer in this order; the first magnetic layer includes magnetic grains having an L10 structure; the second magnetic layer has a granular structure having magnetic grains with an L10 structure and grain boundaries containing hexagonal boron nitride; the (111) plane of the magnetic grains included in the first magnetic layer is covered with aluminum nitride at the interface with the second magnetic layer; the magnetic grains contained in the second magnetic layer are epitaxially grown from the (001) plane of the magnetic grains contained in the first magnetic layer; A magnetic recording medium, wherein the magnetic grains contained in the first magnetic layer and the magnetic grains contained in the second magnetic layer are columnar crystals that penetrate the first magnetic layer and the second magnetic layer, respectively. (2) The magnetic recording medium according to (1), wherein the magnetic particles having an L10 structure contained in the first magnetic layer and the second magnetic layer are FePt alloy particles. (3) A method for producing a magnetic recording medium according to (1) or (2), The manufacturing method includes a step of forming an aluminum nitride layer by sputtering between a step of forming the first magnetic layer by sputtering and a step of forming the second magnetic layer by sputtering. (4) A magnetic storage device having the magnetic recording medium according to (1) or (2). [Effects of the Invention]

[0014] According to one aspect of the present invention, it is possible to provide a magnetic recording medium in which the granular magnetic layer stably maintains the state in which a granular structure is formed inside, and in which the areal recording density is further improved.

[0015] According to another aspect of the present invention, it is possible to provide a method for manufacturing a magnetic recording medium in which the granular magnetic layer stably maintains the state in which a granular structure is formed inside, and in which the areal recording density is further improved.

[0016] According to another aspect of the present invention, a magnetic storage device with a high recording capacity can be provided. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a cross-sectional view showing an example of a layer structure of a magnetic recording medium according to an embodiment of the present invention. [Figure 2] 1A and 1B are cross-sectional schematic diagrams illustrating crystal growth during the formation of the first magnetic layer and the second magnetic layer, where (a) is a cross-sectional schematic diagram showing conventional crystal growth, and (b) is a cross-sectional schematic diagram showing crystal growth in an embodiment of the present invention. [Figure 3] 1 is a perspective view showing an example of a magnetic storage device according to an embodiment of the present invention; [Figure 4] FIG. 4 is a schematic diagram showing the magnetic head of FIG. 3. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The drawings used in the following description may show characteristic portions enlarged for ease of understanding, and the dimensional ratios of each component element may not be the same. Furthermore, in this specification, unless otherwise specified, "to" indicating a numerical range means that the numerical values ​​before and after it are included as the lower and upper limits. Furthermore, when only the upper limit value in a numerical range expressed by "to" is specified in units, the lower limit value is also specified in the same units.

[0019] [Magnetic recording media] An example of the layer structure of a magnetic recording medium according to this embodiment is shown in Figure 1. As shown in Figure 1, the magnetic recording medium 1 includes a substrate 10, an underlayer 20, a first magnetic layer 30, and a second magnetic layer 40, stacked in this order.

[0020] The substrate 10 may be a substrate that is generally used for the magnetic recording medium 1. For example, a heat-resistant glass substrate with a softening temperature of 500°C or higher, preferably 600°C or higher, is preferably used as the substrate 10. The substrate 10 can also be used when it is heated to a temperature of 500°C or higher during the manufacture of the magnetic recording medium 1.

[0021] The material for forming the underlayer 20 is not particularly limited as long as it can orient the magnetic grains having the L10 structure contained in the first magnetic layer 30 and the second magnetic layer 40 in the (001) plane.

[0022] The underlayer 20 may have a multi-layer structure.

[0023] The underlayer 20 preferably contains an NaCl-type compound.

[0024] Examples of NaCl type compounds include MgO, TiO, NiO, TiN, TaN, HfN, NbN, ZrC, HfC, TaC, NbC, TiC, etc. These may be used alone or in combination of two or more.

[0025] The first magnetic layer 30 includes magnetic grains having an L10 structure.

[0026] Examples of magnetic grains having an L10 structure that constitute the first magnetic layer 30 include FePt alloy grains and CoPt alloy grains. The FePt alloy grains and CoPt alloy grains are magnetic grains with an L10 structure oriented in the (001) direction.

[0027] The magnetic grains contained in the first magnetic layer 30 are columnar crystals that penetrate the first magnetic layer 30 .

[0028] The particle size of the magnetic particles contained in the first magnetic layer 30 is not particularly limited as long as they are columnar, and may be, for example, 3 to 7 nm in equivalent circle diameter. The average particle size of the magnetic particles contained in the first magnetic layer 30 can be measured by observation with a planar transmission electron microscope.

[0029] The aspect ratio of the magnetic grains contained in the first magnetic layer 30 depends on the thickness of the first magnetic layer 30, but for example, when the height (t) of a columnar grain is taken as the diameter (D) of an equivalent circle, it is sufficient if t / D = 0.1 to 1.5. The aspect ratio is the value obtained by dividing the longest axis by the shortest axis of a magnetic grain. The aspect ratio of a magnetic grain is determined by dividing the grain height of the magnetic grain measured by observation with a cross-sectional transmission electron microscope by the average grain size of the magnetic grain measured by observation with a planar transmission electron microscope.

[0030] The center-to-center distance between magnetic particles contained in the first magnetic layer 30 is preferably 4.0 to 8.0 nm. The center-to-center distance between magnetic particles contained in the first magnetic layer 30 is more preferably 7.8 nm or less, and even more preferably 7.6 nm or less. If the center-to-center distance between magnetic particles contained in the first magnetic layer 30 is within the above preferred range, the first magnetic layer 30 can contain magnetic particles with small particle sizes.

[0031] The center-to-center distance between magnetic particles refers to the distance between the centers of gravity of adjacent magnetic particles, and can be measured, for example, by calculating the center-to-center distance between the centers of gravity of adjacent magnetic particles from a surface observation image obtained with a scanning electron microscope (SEM).

[0032] The second magnetic layer 40 is a granular magnetic layer including magnetic grains having an L10 structure and grain boundary portions, and the grain boundary portions include hexagonal boron nitride.

[0033] Examples of magnetic particles having an L10 structure that form the second magnetic layer 40 include FePt alloy particles and CoPt alloy particles.

[0034] The magnetic grains contained in the second magnetic layer 40 are columnar crystals that penetrate the second magnetic layer 40, similar to the magnetic grains contained in the first magnetic layer 30.

[0035] The particle size of the magnetic particles contained in the second magnetic layer 40 is not particularly limited as long as they are columnar, similar to the magnetic particles contained in the first magnetic layer 30, and may be, for example, 3 to 7 nm in equivalent circle diameter. The average particle size of the magnetic particles contained in the second magnetic layer 40 can be measured by the same method as for the magnetic particles contained in the first magnetic layer 30.

[0036] The aspect ratio of the magnetic particles contained in the second magnetic layer 40, like the aspect ratio of the magnetic particles contained in the first magnetic layer 30, depends on the thickness of the second magnetic layer 40, but may be, for example, t / D = 1.2 to 2.5. The aspect ratio is calculated as t / D, where t is the height of a columnar particle and D is its equivalent circle diameter. The aspect ratio of the magnetic particles contained in the second magnetic layer 40 can be measured using the same method as that used to measure the aspect ratio of the magnetic particles contained in the first magnetic layer 30.

[0037] The hexagonal boron nitride contained in the grain boundary portion has a layered structure in which the (001) planes are stacked approximately parallel, and it is easy to form a grain boundary portion between the hexagonal boron nitride and the magnetic grains contained in the second magnetic layer 40, so the grain size of the magnetic grains contained in the second magnetic layer 40 can be reduced. In addition, hexagonal boron nitride has low reactivity with magnetic grains having an L10 structure, so it does not inhibit the ordering of the magnetic grains contained in the second magnetic layer 40. Therefore, it is preferable that the hexagonal boron nitride is formed so that its (001) plane surrounds the side surfaces of the magnetic grains contained in the second magnetic layer 40.

[0038] Using conventional methods, it was difficult to consistently form such granular magnetic layers. Because the reactivity between the magnetic alloy and boron nitride was low, the two often formed separate layers during film formation, resulting in an unstructured granular structure. Furthermore, the boron nitride often became amorphous rather than crystallized.

[0039] The inventors of the present application discovered that by forming the magnetic layer into a two-layer structure consisting of a first magnetic layer 30 and a second magnetic layer 40 from the substrate 10 side, and by epitaxially growing the magnetic grains of the second magnetic layer 40 from the magnetic grains of the first magnetic layer 30, the granular structure of the second magnetic layer 40 can be stably formed.

[0040] In this case, the magnetic grains on the growth surface of the first magnetic layer 30 form a (111) plane in addition to a (001) plane, and therefore, when the second magnetic layer 40 is formed, crystal growth proceeds in a direction perpendicular to the (111) plane, causing the magnetic grains of the second magnetic layer 40 to coarsen. In order to prevent the magnetic grains of the second magnetic layer 40 from coarsening, in this embodiment, the (111) plane of the first magnetic layer 30 is covered with aluminum nitride, thereby suppressing the coarsening of the magnetic grains of the second magnetic layer 40. This point will be explained in detail using FIG. 2.

[0041] 2A and 2B are cross-sectional schematic diagrams illustrating crystal growth during the formation of the first magnetic layer 30 and the second magnetic layer 40, where FIG. 2A is a cross-sectional schematic diagram illustrating crystal growth during the formation of the conventional first magnetic layer 30 and the second magnetic layer 40, and FIG. 2B is a cross-sectional schematic diagram illustrating crystal growth during the formation of the first magnetic layer 30 and the second magnetic layer 40 of this embodiment. As shown in FIG. 2A, a growth surface 311A ​​of a magnetic grain 31 constituting the first magnetic layer 30 having an L10 structure formed on a substrate 10 is formed with a (001) plane 311B parallel to the substrate 10 and a (111) plane 311C tilted at approximately 35° toward the growth surface 311A ​​side (lower side in FIG. 2) with respect to the (001) plane 311B. When the second magnetic layer 40 (dashed line portion) is formed on the (111) surface 311C, the magnetic grains 41 of the second magnetic layer 40 also grow in the direction perpendicular to the (111) surface 311C of the magnetic grains 31, causing the grain size of the magnetic grains 41 to become coarse.

[0042] 2(b), in this embodiment, the (111) faces 311C of the magnetic grains 31 in the first magnetic layer 30 are covered with an aluminum nitride layer 50. This prevents the magnetic grains 41 in the second magnetic layer 40 (indicated by the dashed line) from becoming coarse, and the magnetic grains 41 of the second magnetic layer 40 are epitaxially grown on the (001) faces 311B of the magnetic grains 31 in the first magnetic layer 30, forming the magnetic grains 31, 41 into columnar crystals that penetrate the first magnetic layer 30 and the second magnetic layer 40, thereby allowing the magnetic grains 31, 41 to maintain a fine grain size.

[0043] In this embodiment, the aluminum nitride layer 50 is a layer containing aluminum nitride, preferably containing 50 atomic % or more of aluminum nitride, and most preferably consisting of only aluminum nitride. The aluminum nitride layer 50 is not a continuous film, but is a film that partially penetrates between the magnetic grains 31 and 41.

[0044] The hexagonal boron nitride grain boundary portion 42 contains hexagonal boron nitride, preferably contains 50 atomic % or more of hexagonal boron nitride, and most preferably is composed solely of hexagonal boron nitride.

[0045] The content of the hexagonal boron nitride grain boundary parts 42 in the second magnetic layer 40 is preferably within a range of 25 to 50 volume %, and more preferably within a range of 35 to 45 volume %. When the content of the hexagonal boron nitride grain boundary parts 42 in the second magnetic layer 40 is within a range of 25 to 50 volume %, the coercive force Hc of the magnetic recording medium 1 and the anisotropy of the magnetic grains 31, 41 contained in the first magnetic layer 30 and the second magnetic layer 40 can be increased.

[0046] The method for measuring the content of hexagonal boron nitride grain boundary portion 42 in second magnetic layer 40 is not particularly limited, and a general method for measuring the volume within a grain can be used. For example, the content can be determined by elemental analysis of the grain boundary portion using TEM-EELS.

[0047] In this embodiment, the first magnetic layer 30 may also have a granular structure, similar to the second magnetic layer 40. In this case, the content of the grain boundary portion in the first magnetic layer 30 may be the same as that of the second magnetic layer 40.

[0048] [Magnetic recording medium manufacturing method] An example of a method for manufacturing the magnetic recording medium 1 will be described. The method for manufacturing the magnetic recording medium 1 includes the steps of forming a first magnetic layer 30 by sputtering, forming an aluminum nitride layer 50 by sputtering aluminum nitride on the main surface of the first magnetic layer 30, and forming a second magnetic layer 40 by sputtering on the main surface of the aluminum nitride layer 50. That is, the magnetic recording medium 1 is manufactured by including a step of forming the aluminum nitride layer 50 by sputtering between the steps of forming the first magnetic layer 30 by sputtering and forming the second magnetic layer 40 by sputtering, thereby providing the aluminum nitride layer 50 between the first magnetic layer 30 and the second magnetic layer 40. By using this manufacturing method, the (111) faces 311C of the magnetic grains 31 on the growth surface of the first magnetic layer 30 can be covered with the aluminum nitride layer 50, thereby preventing the magnetic grains 41 of the second magnetic layer 40 from becoming coarse.

[0049] Such a film formation method may, for example, involve using a discharge gas pressure of 2 Pa or less, using RF discharge, setting the target surface potential at 50 to 200 V, and then heating (post-annealing) the film after formation to a temperature about 100° C. higher than the film formation temperature. The gas atmosphere may be an inert gas atmosphere such as nitrogen or argon.

[0050] Alternatively, after forming the aluminum nitride layer 50 so as to cover the entire surface of the magnetic grain 31, the surface may be etched to remove only the aluminum nitride precipitated on the (001) face 311B of the magnetic grain 31, so that the aluminum nitride covers only the (111) face 311C and the aluminum nitride layer 50 is provided only on the (111) face 311C.

[0051] Nitrogen in the aluminum nitride is easily separated from the etched surface of the aluminum nitride, which has the effect of compensating for nitrogen deficiencies in the hexagonal boron nitride grain boundary portions 42 of the second magnetic layer 40 that is subsequently formed. This makes it possible to shift the XPS peak of the hexagonal boron nitride grain boundary portions 42 to the vicinity of 191 eV, which is the nitride peak. The hexagonal boron nitride grain boundary portions 42 with advanced nitridation have better crystallinity, facilitating the separation of the magnetic grains of hexagonal boron nitride and the columnar growth of hexagonal boron nitride.

[0052] The magnetic grains 31, 41 contained in the first magnetic layer 30 and the second magnetic layer 40 form columnar crystals, so it is preferable to enhance the c-axis orientation, that is, the orientation of the (001) plane, relative to the substrate 10.

[0053] A method for orienting the magnetic grains 31, 41 contained in the first magnetic layer 30 and the second magnetic layer 40 in the c-axis direction relative to the substrate 10 includes, for example, a method of epitaxially growing the first magnetic layer 30 and the second magnetic layer 40 in the c-axis direction using an underlayer 20.

[0054] Another magnetic layer may be provided below the first magnetic layer 30 or above the second magnetic layer 40. The newly provided another magnetic layer preferably contains magnetic grains having an L10 structure, similar to the first magnetic layer 30. Furthermore, the magnetic grains preferably form columnar crystals together with the magnetic grains 31 and 41.

[0055] Therefore, by using the manufacturing method of the magnetic recording medium 1, the magnetic recording medium 1 shown in FIG. 1 can be obtained.

[0056] The magnetic recording medium 1 preferably further comprises a protective layer on the first magnetic layer 30 and the second magnetic layer 40 .

[0057] The protective layer may be, for example, a hard carbon film.

[0058] Examples of methods for forming the protective layer include RF-CVD (Radio Frequency-Chemical Vapor Deposition), which forms a film by decomposing hydrocarbon gas (raw material gas) using high-frequency plasma; IBD (Ion Beam Deposition), which forms a film by ionizing raw material gas with electrons emitted from a filament; and FCVA (Filtered Cathodic Vacuum Arc), which forms a film using a solid carbon target without using a raw material gas.

[0059] The thickness of the protective layer is preferably 1 to 6 nm. If the thickness of the protective layer is 1 nm or more, the floating characteristics of the magnetic head are improved, and if it is 6 nm or less, the magnetic spacing is reduced, improving the SNR (signal / noise ratio (S / N ratio)) of the magnetic recording medium 1.

[0060] In this specification, the thickness of the protective layer refers to the length in the direction perpendicular to the main surface of the protective layer. The thickness of the protective layer is, for example, the thickness measured at an arbitrary location on the cross section of the protective layer. When measurements are taken at several arbitrary locations on the cross section of the protective layer, the average value of the thicknesses measured at these locations may be used. The same measurement method as for the thickness of the protective layer can also be used for other layers.

[0061] The magnetic recording medium 1 may further have a lubricant layer on the protective layer.

[0062] The lubricant layer can be formed using a liquid lubricant layer. A liquid lubricant that is chemically stable, has low friction, and has low adsorption is preferably used. Examples of the liquid lubricant include fluororesin-based lubricants such as perfluoropolyether-based lubricants containing compounds having a perfluoropolyether structure.

[0063] The thickness of the lubricant layer is not particularly limited, but may be, for example, 1 to 3 nm.

[0064] In addition to the protective layer and the lubricant layer, the magnetic recording medium 1 may include any other layers as appropriate. For example, the magnetic recording medium 1 may include an adhesion layer, a soft magnetic underlayer, an orientation control layer, etc. between any of the substrate 10, the underlayer 20, and the first magnetic layer 30, as needed. The soft magnetic underlayer may include, for example, a first soft magnetic layer, an intermediate layer, and a second soft magnetic layer. The orientation control layer may be a single layer, or may be two or more layers (e.g., a first orientation control layer, a second orientation control layer, etc.). Materials for forming the adhesion layer, the soft magnetic underlayer, the orientation control layer, etc. may be materials commonly used in magnetic recording media.

[0065] As described above, the magnetic recording medium 1 includes a substrate 10, an underlayer 20, a first magnetic layer 30, and a second magnetic layer 40, in this order. The first magnetic layer 30 includes magnetic grains 31 having an L10 structure. The second magnetic layer 40 is a granular magnetic layer including magnetic grains 41 having an L10 structure and hexagonal boron nitride grain boundary portions 42, and the hexagonal boron nitride grain boundary portions 42 include hexagonal boron nitride. The (111) faces 311C of the magnetic grains 31 are covered with aluminum nitride at the interfaces with the second magnetic layer 40, and the magnetic grains 41 grow epitaxially from the (001) faces 311B of the magnetic grains 31. The magnetic grains 31 and 41 are formed to form columnar crystals that penetrate the first magnetic layer 30 and the second magnetic layer 40. Therefore, the particle diameter of the magnetic particles 31 and 41 is small and minute, and the magnetic particles 31 and 41 are formed continuously in one direction in a columnar shape.

[0066] The magnetic recording medium 1 can enhance anisotropy by reducing the particle size of the magnetic grains 31 and 41 contained in the first magnetic layer 30 and the second magnetic layer 40, respectively, and by containing the magnetic grains 31 and 41 in a state where they are continuously connected in the same direction. Therefore, the magnetic recording medium 1 can stably maintain the state in which a granular structure is formed inside the second magnetic layer 40 and can stably contain the second magnetic layer 40 as a granular magnetic layer, thereby further improving the areal recording density.

[0067] Because the magnetic recording medium 1 has the above-described characteristics, even when a thermally assisted recording method or a microwave-assisted recording method is used as the recording method, the first magnetic layer 30 and the second magnetic layer 40 have a high recording density, and magnetic information can be sufficiently recorded on the first magnetic layer 30 and the second magnetic layer 40 by the recording magnetic field of a magnetic head. Therefore, the magnetic recording medium 1 can be suitably used in a magnetic recording and reproducing device having an even higher recording density.

[0068] [Magnetic storage device] A magnetic storage device including a magnetic recording medium according to this embodiment will be described. The magnetic storage device according to this embodiment is not particularly limited in form as long as it includes the magnetic recording medium according to this embodiment. Here, a case will be described in which the magnetic storage device records magnetic information on the magnetic recording medium using a thermally assisted recording method.

[0069] The magnetic storage device according to this embodiment may include, for example, a magnetic recording medium drive unit that drives and rotates the magnetic recording medium according to this embodiment, a magnetic head having a near-field light generating element at its tip, a magnetic head drive unit that drives and moves the magnetic head, and a recording / reproducing signal processing system.

[0070] The magnetic head is a thermally assisted recording type magnetic head, and has, for example, a laser light generating unit that generates laser light to heat the magnetic recording medium, and a waveguide that guides the laser light generated from the laser light generating unit to a near-field light generating element.

[0071] Fig. 3 shows a perspective view of an example of a magnetic storage device using the magnetic recording medium according to this embodiment. As shown in Fig. 3, the magnetic storage device 100 can include a magnetic recording medium 101, a magnetic recording medium drive unit 102 for rotating the magnetic recording medium 101, a magnetic head 103 equipped with a near-field light generating element at its tip, a magnetic head drive unit 104 for moving the magnetic head 103, and a recording / reproducing signal processing unit 105. The magnetic recording medium 101 is the magnetic recording medium 1 described above.

[0072] 4 is a schematic diagram of an example of the magnetic head 103. As shown in FIG.

[0073] The recording head 110 has a main magnetic pole 111, an auxiliary magnetic pole 112, a coil 113 that generates a magnetic field, a laser diode (LD) 114 that generates laser light, and a waveguide 116 that guides the laser light L generated from the LD 114 to a near-field light generating element 115.

[0074] The read head 120 has a shield 121 and a read element 122 sandwiched between the shields 121 .

[0075] As shown in Figure 3, in the magnetic storage device 100, the center of the magnetic recording medium 101 is attached to the rotating shaft of a spindle motor, and the magnetic head 103 writes or reads information to or from the magnetic recording medium 101 while floating and running above the surface of the magnetic recording medium 101, which is rotated by the spindle motor.

[0076] In the magnetic storage device 100 according to this embodiment, by using the magnetic recording medium 1 as the magnetic recording medium 101, the areal recording density of the magnetic recording medium 101 can be increased, and therefore the recording capacity of the magnetic recording medium 101 can be increased.

[0077] The magnetic storage device may use a microwave-assisted recording magnetic head as the magnetic head 103 instead of a thermally-assisted recording magnetic head.

[0078] Although the embodiments have been described above, they are presented as examples and the present invention is not limited to the above embodiments. The above embodiments can be implemented in various other forms, and various combinations, omissions, substitutions, modifications, etc. can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as set forth in the claims. [Example]

[0079] Hereinafter, the embodiment will be described in more detail with reference to examples and comparative examples, but the embodiment is not limited to these examples and comparative examples.

[0080] <Magnetic Recording Media Manufacturing> Example 1 A 100 nm thick Cr-50 at% Ti alloy layer and a 30 nm thick Co-27 at% Fe-5 at% Zr-5 at% B alloy layer were sequentially formed on a glass substrate as an underlayer by sputtering. The glass substrate was then heated to 250°C, and a 10 nm thick Cr layer and a 5 nm thick MgO layer were sequentially formed by sputtering. The glass substrate was then heated to 450°C, and a 0.5 nm thick (Fe-48 at% Pt-5 at% B) alloy layer (first magnetic layer) was then formed by sputtering.

[0081] Then, a 0.2 nm thick aluminum nitride layer was deposited as a coating layer on the (111) plane by RF sputtering under the conditions of a target surface potential of 100 V, a deposition rate of 0.08 nm / s, and a post-annealing temperature approximately 100°C higher than the deposition temperature.

[0082] Thereafter, etching was performed in an argon atmosphere of 0.5 Pa at 7 W.

[0083] This resulted in a structure in which the (111) planes of the magnetic grains of the first magnetic layer were covered with the aluminum nitride layer.

[0084] Then, a 13 nm thick (Fe-49 at% Pt)-40 volume % hexagonal boron nitride layer (second magnetic layer) was formed by sputtering, followed by a 3 nm thick carbon film as a protective layer, completing the magnetic recording medium.

[0085] Table 1 shows the composition and coating conditions of the first magnetic layer and the composition of the second magnetic layer.

[0086] (Examples 2 to 7, Comparative Examples 1 to 8) A magnetic recording medium was produced in the same manner as in Example 1, except that the coating conditions for the first magnetic layer were changed to those shown in Table 1.

[0087] <Evaluation of magnetic recording media> The magnetic recording media manufactured in each example and comparative example were evaluated by checking the coating state of the (111) faces of the magnetic grains in the first magnetic layer with the aluminum nitride layer and the crystallinity of the hexagonal boron nitride (hBN), and by measuring the coercive force Hc of the magnetic recording media and the center-to-center distance between the magnetic grains in the first magnetic layer.

[0088] (Covering state of the (111) faces of the magnetic particles in the first magnetic layer with the aluminum nitride layer) The coating state of the aluminum nitride layer on the (111) faces of the magnetic particles in the first magnetic layer was evaluated by observing the cross section of the magnetic recording medium using a transmission electron microscope (HD2300, manufactured by Hitachi High-Technologies Corporation). When the thickness of the aluminum nitride layer was not uniform and the magnetic particles were connected to each other, the coating quality was evaluated as being deteriorated.

[0089] (Crystalline nature of hexagonal boron nitride) The crystallinity of the hexagonal boron nitride in the first magnetic layer was evaluated by observing the cross section of the magnetic recording medium using a transmission electron microscope (HD2300, manufactured by Hitachi High-Technologies Corporation) and observing the lattice fringes. When observing a crystalline material with an electron microscope, lattice fringes can be observed at the lattice spacing. Therefore, by observing the cross section of the magnetic recording medium with a transmission electron microscope and observing the lattice fringes, the crystallinity of the hexagonal boron nitride in the first magnetic layer can be confirmed. If the crystallinity of the hexagonal boron nitride is good, the state in which a granular structure is formed inside the second magnetic layer is stably maintained, and it can be evaluated that the second magnetic layer functions as a granular magnetic layer.

[0090] (Coercive force Hc of magnetic recording medium) The coercivity Hc of the magnetic recording medium was evaluated by measuring the Kerr rotation angle when a laser beam (wavelength 408 nm) was irradiated onto the main surface of the magnetic recording medium using a superconducting Kerr measurement device (BH-810-HM7, manufactured by NeoArc Corporation). The coercivity Hc reflects the crystallinity of the magnetic particles in the first and second magnetic layers, and it is believed that the coercivity Hc decreases when the crystal structure of the first and second magnetic layers is disrupted. Therefore, it can be evaluated that the higher the coercivity Hc, the higher the crystallinity of the first and second magnetic layers, and the more likely it is that the areal recording density can be improved.

[0091] (Center-to-center distance between magnetic particles in the first magnetic layer) The center-to-center distance between magnetic particles in the first magnetic layer was obtained by calculating the center-to-center distance between the centers of gravity of adjacent magnetic particles in the first magnetic layer from surface observation images obtained by SEM. The smaller the center-to-center distance between magnetic particles, the smaller the particle size of the magnetic particles. Therefore, the smaller the center-to-center distance between magnetic particles in the first magnetic layer, the smaller the particle size of the magnetic particles in the first magnetic layer, and the more likely it is that the areal recording density can be improved. When evaluating the particle size of the magnetic particles, a one-minute argon etching process was performed to remove the carbon protective film from the surface of the magnetic recording medium.

[0092] Table 1 shows the evaluation results of the coating state of the (111) face of the magnetic grains in the first magnetic layer with the aluminum nitride layer, the crystallinity of the hexagonal boron nitride, and the measurement results of the coercive force Hc of the magnetic recording medium and the center-to-center distance between the magnetic grains in the first magnetic layer.

[0093] [Table 1]

[0094] From Table 1, it was confirmed that the magnetic recording media of each Example had a high coercive force Hc. Therefore, it was confirmed that by coating the (111) plane of the magnetic grains of the first magnetic layer with aluminum nitride, the grain size of the magnetic grains contained in the first magnetic layer and the second magnetic layer can be reduced, and the second magnetic layer can maintain the state in which a granular structure is formed therein and function as a granular magnetic layer. Therefore, it can be said that the magnetic recording media of each Example have a high areal recording density, and therefore, when used in a magnetic storage device, can have a high recording capacity. [Explanation of symbols]

[0095] 1, 101 Magnetic recording media 10 Substrate 20 Base layer 30 First magnetic layer 31, 41 magnetic particles 40 Second magnetic layer 42 Hexagonal boron nitride grain boundary (grain boundary) 50 Aluminum nitride layer 100 Magnetic storage device 311A Growth aspect 42A, 50A, 311B (001) plane 311C (111) side

Claims

1. a substrate, an underlayer, a first magnetic layer, and a second magnetic layer in this order; The first magnetic layer is L1 ０ magnetic particles having a structure, The second magnetic layer is L1 ０ and a granular structure having a grain boundary portion containing hexagonal boron nitride, the (111) faces of the magnetic grains included in the first magnetic layer are covered with aluminum nitride at the interface with the second magnetic layer; the magnetic grains contained in the second magnetic layer are epitaxially grown from the (001) planes of the magnetic grains contained in the first magnetic layer, A magnetic recording medium, wherein the magnetic grains contained in the first magnetic layer and the magnetic grains contained in the second magnetic layer are columnar crystals that penetrate the first magnetic layer and the second magnetic layer, respectively.

2. L1 included in the first magnetic layer and the second magnetic layer ０ 2. The magnetic recording medium according to claim 1, wherein the magnetic particles having the structure are FePt alloy particles.

3. 3. A method for producing a magnetic recording medium according to claim 1 or 2, comprising the steps of: The manufacturing method includes a step of forming an aluminum nitride layer by sputtering between a step of forming the first magnetic layer by sputtering and a step of forming the second magnetic layer by sputtering.

4. 3. A magnetic storage device comprising the magnetic recording medium according to claim 1.

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