Magnetic recording medium, method for manufacturing a magnetic recording medium, and magnetic storage device

Abstract

The present invention provides a magnetic recording medium that stably maintains a state in which a granular magnetic layer forms a granular structure internally, thereby further improving the areal recording density. [Solution] The magnetic recording medium 1 comprises a substrate 10, an underlayer 20, a first magnetic layer 30, and a second magnetic layer 40 in this order. The first magnetic layer contains magnetic particles having an L10 structure, and the second magnetic layer has a granular structure with magnetic particles having an L10 structure and grain boundaries containing hexagonal boron nitride. The (111) plane of the magnetic particles contained in the first magnetic layer is covered with an alloy of VN, Si3N4, YN, or TiN at the interface with the second magnetic layer. The magnetic particles contained in the second magnetic layer are epitaxially grown from the (001) plane of the magnetic particles contained in the first magnetic layer. The magnetic particles contained in the first magnetic layer and the magnetic particles contained in the second magnetic layer are columnar crystals that penetrate the first magnetic layer and the second magnetic layer, respectively.

Description

Technical Field

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

Background Art

[0002] In recent years, a heat assist recording method or a microwave assist recording method in which a magnetic recording medium is irradiated with near-field light or microwaves to be locally heated to reduce the coercive force for recording has attracted attention as a next-generation recording method capable of achieving a high areal recording density of about 2 Tbit / inch , , ,

[0006] , or so.

[0003] When using such an assist recording type magnetic head, it can be easily recorded on a magnetic recording medium having a coercive force of several tens of kOe at room temperature. And, as the magnetic particles contained in the magnetic layer of the magnetic recording medium, for example, magnetic particles having a high crystalline magnetic anisotropy constant (Ku) are used. Magnetic particles having a high crystalline magnetic anisotropy constant (Ku) can be miniaturized while maintaining thermal stability and increase the coercive force at room temperature.

[0004] Examples of magnetic particles having a high crystalline magnetic anisotropy constant (Ku) include 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 ), etc., magnetic particles having an L10 structure are known.

[0005] As a magnetic layer using magnetic particles having an L10 structure, for example, Non-Patent Document 1 discloses a granular structure magnetic layer in which the periphery of FePt magnetic particles having an L10 structure is covered with a layer of hexagonal boron nitride.

Prior Art Documents

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

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

[0009] Hexagonal boron nitride has a layered structure in which (001) planes are stacked in parallel, and it readily forms grain boundaries between FePt magnetic particles, thus allowing for a reduction in the particle size of the FePt magnetic particles. Furthermore, hexagonal boron nitride has low reactivity with FePt magnetic particles, so it does not hinder the order of the magnetic particles. Preferably, such hexagonal boron nitride is formed so that its (001) planes surround the sides of the FePt magnetic particles.

[0010] However, in conventional FePt-hBN granular magnetic layers, the magnetic particles and grain boundaries tended to separate into layers, often resulting in a structure that did not resemble a granular structure. Furthermore, components at the grain boundaries, such as BN, often did not crystallize sufficiently, remaining in an amorphous state. Therefore, even when using a magnetic layer with a granular structure (also called a granular magnetic layer), there was a problem in that the areal recording density of the magnetic recording medium could not always be improved.

[0011] One aspect of this disclosure aims to provide a magnetic recording medium that stably maintains a state in which a granular magnetic layer has formed a granular structure inside, thereby further improving the areal recording density. [Means for solving the problem]

[0012] The above objectives can be achieved as follows:

[0013] (1) The substrate, the underlayer, the first magnetic layer, and the second magnetic layer are arranged in this order. The first magnetic layer comprises magnetic particles having an L10 structure, The second magnetic layer comprises magnetic particles having an L10 structure and a granular structure having grain boundaries containing hexagonal boron nitride. The (111) plane of the magnetic particles contained in the first magnetic layer is covered with an alloy of VN, Si3N4, YN, or TiN at the interface with the second magnetic layer. The magnetic particles contained in the second magnetic layer are epitaxially grown from the (001) plane of the magnetic particles contained in the first magnetic layer. A magnetic recording medium in which the magnetic particles contained in the first magnetic layer and the magnetic particles 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) Having a substrate, an underlayer, a first magnetic layer, and a second magnetic layer in this order, The first magnetic layer includes magnetic particles having an L10 structure, The second magnetic layer has a granular structure having a grain boundary portion containing magnetic particles having an L10 structure and hexagonal boron nitride, The (111) plane of the magnetic particles contained in the first magnetic layer is covered with an alloy of any one of VN, Si3N4, YN or TiN at the interface with the second magnetic layer, The magnetic particles contained in the second magnetic layer are epitaxially grown from the (001) plane of the magnetic particles contained in the first magnetic layer, A method for manufacturing a magnetic recording medium, wherein the magnetic particles contained in the first magnetic layer and the magnetic particles contained in the second magnetic layer are columnar crystals penetrating the first magnetic layer and the second magnetic layer, respectively, A method for manufacturing a magnetic recording medium, including a step of forming an alloy layer of any one of an alloy of VN, Si3N4, YN and TiN 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).

Effect of the Invention

[0014] According to one aspect of the present disclosure, it is possible 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 the areal recording density is further improved.

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

[0016] Also, according to another aspect of the present disclosure, it is possible to provide a magnetic storage device with a high recording capacity.

Brief Description of the Drawings

[0017] [Figure 1]It is a cross-sectional view showing an example of the layer structure of a magnetic recording medium according to an embodiment of the present disclosure. [Figure 2] It is a schematic cross-sectional view for explaining crystal growth during the formation of the first magnetic layer and the second magnetic layer. (a) is a schematic cross-sectional view showing conventional crystal growth, and (b) is a schematic cross-sectional view showing crystal growth of an embodiment of the present disclosure. [Figure 3] It is a perspective view showing an example of a magnetic storage device according to an embodiment of the present disclosure. [Figure 4] It is a schematic view showing the magnetic head of FIG. 3.

Embodiments for Carrying Out the Invention

[0018] Hereinafter, embodiments for carrying out the present disclosure will be described with reference to the drawings. In the drawings used in the following description, for the sake of clarity of the features, the characteristic parts may be enlarged for convenience, and the dimensional ratios of the respective components are not necessarily the same. In this specification, "~" indicating a numerical range means that the numerical values described before and after it are included as the lower limit value and the upper limit value unless otherwise specified. Also, when only the unit of the upper limit value is described in the numerical range represented by "~", it means that the lower limit value is also in the same unit.

[0019] [Magnetic Recording Medium] FIG. 1 shows an example of the layer structure of a magnetic recording medium according to an embodiment of the present disclosure (hereinafter sometimes referred to as the present embodiment). As shown in FIG. 1, the magnetic recording medium 1 includes a substrate 10, an underlayer 20, a first magnetic layer 30, and a second magnetic layer 40 laminated in this order.

[0020] The substrate 10 may be a substrate generally used for the magnetic recording medium 1. As the substrate 10, for example, it is preferable to use a heat-resistant glass substrate having a softening temperature of 500 ° C or higher, preferably 600 ° C or higher. It can be used even when the substrate 10 is heated to a temperature of 500 ° C or higher when manufacturing the magnetic recording medium 1.

[0021] The material constituting the base layer 20 is not particularly limited, as long as it is possible to orient the magnetic particles having the L10 structure contained in the first magnetic layer 30 and the second magnetic layer 40 in the (001) plane.

[0022] The base layer 20 may have a multilayer structure.

[0023] The base layer 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, or TiC. These may be used individually or in combination of two or more.

[0025] The first magnetic layer 30 contains magnetic particles having an L10 structure.

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

[0027] The magnetic particles contained in the first magnetic layer 30 are columnar crystals having a shape that penetrates 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 in shape; for example, it can be 3 to 7 nm in equivalent diameter. The particle size of the magnetic particles contained in the first magnetic layer 30 may be the average particle size of the magnetic particles observed and measured with a planar transmission electron microscope. If the magnetic particles are spherical, their diameter is used; if they are elliptical, the midpoint between their short and long axes is used; and if they are amorphous, the midpoint between their short and long sides is used to determine the particle size and create a particle size distribution of the magnetic particles. The average value of the particle sizes obtained based on the created particle size distribution may be used as the average particle size of the magnetic particles.

[0029] The aspect ratio of the magnetic particles contained in the first magnetic layer 30 depends on the thickness of the first magnetic layer 30. For example, if the height of the magnetic particle is t and the equivalent diameter of the circle is D, the aspect ratio (t / D) of the magnetic particle should be between 0.1 and 1.5. The aspect ratio is the value obtained by dividing the longest axis of a magnetic particle by the shortest axis. The aspect ratio of a magnetic particle can be determined by dividing the particle height of the magnetic particle, measured by observation with a cross-sectional transmission electron microscope, by the average particle size of the magnetic particle, measured by observation with a planar transmission electron microscope.

[0030] The central distance between magnetic particles in the first magnetic layer 30 is preferably 4.0 to 9.0 nm. More preferably, the central distance between magnetic particles in the first magnetic layer 30 is 8.8 nm or less, and even more preferably 8.6 nm or less. If the central distance between magnetic particles in the first magnetic layer 30 is within the above preferred range, the first magnetic layer 30 can contain magnetic particles with smaller particle sizes.

[0031] The central distance between magnetic particles refers to the distance between the centers of mass of adjacent magnetic particles. This central distance can be measured, for example, by calculating the distance between the centers of mass of adjacent magnetic particles from surface observation images obtained with a scanning electron microscope (SEM).

[0032] The second magnetic layer 40 is a granular magnetic layer containing magnetic particles having an L10 structure and grain boundaries, the grain boundaries containing hexagonal boron nitride and also referred to as hexagonal boron nitride grain boundaries.

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

[0034] The magnetic particles contained in the second magnetic layer 40 are columnar crystals that penetrate the second magnetic layer 40, similar to the magnetic particles 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; for example, it can be 3 to 7 nm in equivalent circular diameter. The average particle size of the magnetic particles contained in the second magnetic layer 40 can be measured in the same way as 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 depends on the thickness of the second magnetic layer 40, similar to the aspect ratio of the magnetic particles contained in the first magnetic layer 30. For example, the aspect ratio of the magnetic particles should be between 1.2 and 2.5. The aspect ratio of the magnetic particles can be calculated as t / D, where t is the height of the magnetic particle and D is the equivalent diameter of the circle. The aspect ratio of the magnetic particles contained in the second magnetic layer 40 can be measured using the same method as the method for measuring the aspect ratio of the magnetic particles contained in the first magnetic layer 30.

[0037] The hexagonal boron nitride contained in the grain boundaries has a layered structure in which (001) planes are stacked substantially parallel to each other, and readily forms grain boundaries with the magnetic particles contained in the second magnetic layer 40, thereby reducing the particle size of the magnetic particles contained in the second magnetic layer 40. Furthermore, since hexagonal boron nitride has low reactivity with magnetic particles having an L10 structure, it does not hinder the ordering of the magnetic particles contained in the second magnetic layer 40. For this reason, it is preferable to form the hexagonal boron nitride such that its (001) planes surround the sides of the magnetic particles contained in the second magnetic layer 40.

[0038] Conventional methods have made it difficult to stably deposit such granular magnetic layers. Specifically, because the reactivity between magnetic alloys and boron nitride is low, the two often separate during deposition, forming layered structures that do not develop a granular structure. In addition, boron nitride often remains amorphous instead of crystallizing.

[0039] The inventors of this disclosure have found that by forming a two-layer structure of a magnetic layer consisting of a first magnetic layer 30 and a second magnetic layer 40 from the substrate 10 side, and by epitaxially growing the magnetic particles of the second magnetic layer 40 from the magnetic particles of the first magnetic layer 30, the granular structure of the second magnetic layer 40 can be stably formed.

[0040] In this case, since the magnetic particles on the growth surface of the first magnetic layer 30 form both a (001) plane and a (111) plane, crystal growth proceeds perpendicular to this (111) plane during the deposition of the second magnetic layer 40, causing the magnetic particles of the second magnetic layer 40 to coarseen. To prevent the coarsening of the magnetic particles of the second magnetic layer 40, in this embodiment, the coarsening of the magnetic particles of the second magnetic layer 40 can be suppressed by covering the (111) plane of the first magnetic layer 30 with an alloy made of a nitride of VN, Si3N4, YN, or TiN. This point will be explained in detail with reference to Figure 2.

[0041] Figure 2 is a schematic cross-sectional diagram illustrating crystal growth during the formation of the first magnetic layer 30 and the second magnetic layer 40. (a) is a schematic cross-sectional diagram showing the crystal growth during the formation of the conventional first magnetic layer 30 and the second magnetic layer 40, and Figure 2(b) is a schematic cross-sectional diagram showing the crystal growth during the formation of the first magnetic layer 30 and the second magnetic layer 40 of this embodiment. As shown in Figure 2(a), the growth surface 311A ​​of the magnetic particles 31 constituting the first magnetic layer 30 having an L10 structure formed on the substrate 10 has a (001) surface 311B parallel to the substrate 10 and a (111) surface 311C tilted at approximately 35° toward the growth surface 311A ​​side (downward side in Figure 2) relative to the (001) surface 311B. When a second magnetic layer 40 (dashed line portion) is formed on the (111) plane 311C, the magnetic particles 41 of the second magnetic layer 40 also grow in the direction perpendicular to the (111) plane 311C of the magnetic particles 31, causing the particle size of the magnetic particles 41 to coarseen.

[0042] On the other hand, in this embodiment, as shown in Figure 2(b), the (111) plane 311C of the magnetic particles 31 of the first magnetic layer 30 is covered with a layer 50 of an alloy of VN, Si3N4, YN, or TiN. This suppresses the coarsening of the magnetic particles 41 of the second magnetic layer 40 (dashed line portion), and by epitaxially growing the magnetic particles 41 of the second magnetic layer 40 on the (001) plane 311B of the magnetic particles 31 of the first magnetic layer 30, the magnetic particles 31 and 41 are made into columnar crystals that penetrate the first magnetic layer 30 and the second magnetic layer 40, thereby maintaining a fine particle size.

[0043] In this embodiment, the layer 50 of the alloy of VN, Si3N4, YN, or TiN is a layer containing an alloy made of a nitride of VN, Si3N4, YN, or TiN, preferably containing 50 atomic percent or more of the alloy of VN, Si3N4, YN, or TiN, and most preferably composed only of the alloy of VN, Si3N4, YN, or TiN. Furthermore, the layer 50 of the alloy of VN, Si3N4, YN, or TiN is not a continuous film, but a film that partially penetrates between the magnetic particles 31 and 41.

[0044] The hexagonal boron nitride grain boundary portion 42 of the second magnetic layer 40 contains hexagonal boron nitride, preferably containing 50 atomic percent or more of hexagonal boron nitride, and most preferably consisting solely of hexagonal boron nitride.

[0045] The content of hexagonal boron nitride grain boundaries 42 in the second magnetic layer 40 is preferably in the range of 25 to 50 volume%, and more preferably in the range of 35 to 45 volume%. When the content of hexagonal boron nitride grain boundaries 42 in the second magnetic layer 40 is in the range of 25 to 50 volume%, the coercivity Hc of the magnetic recording medium 1 and the anisotropy of the magnetic particles 31 and 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 boundaries 42 in the second magnetic layer 40 is not particularly limited, and general methods for measuring the volume in particles can be used, but it can be determined, for example, by elemental analysis of the grain boundaries by 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 that case, the content of grain boundaries within the first magnetic layer 30 may be the same as that of the second magnetic layer 40.

[0048] [Manufacturing method for magnetic recording media] An example of a method for manufacturing a magnetic recording medium 1 is described below. The method for manufacturing the magnetic recording medium 1 includes the steps of forming a first magnetic layer 30 by sputtering, forming a layer 50 of an alloy of VN, Si3N4, YN, or TiN on the main surface of the first magnetic layer 30 by sputtering, and forming a second magnetic layer 40 on the main surface of the layer 50 of an alloy of VN, Si3N4, YN, or TiN by sputtering. That is, the magnetic recording medium 1 is manufactured by including a step of forming a layer 50 of an alloy of VN, Si3N4, YN, or TiN by sputtering between the step of forming the first magnetic layer 30 by sputtering and the step of forming the second magnetic layer 40 by sputtering, and providing a layer 50 of an alloy of VN, Si3N4, YN, or TiN between the first magnetic layer 30 and the second magnetic layer 40. By using this manufacturing method, the (111) plane 311C of the magnetic particles 31 on the growth surface of the first magnetic layer 30 can be covered with a layer 50 of any of the alloys VN, Si3N4, YN, or TiN, thereby suppressing the coarsening of the magnetic particles 41 in the second magnetic layer 40.

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

[0050] Alternatively, a layer 50 of an alloy of VN, Si3N4, YN, or TiN may be formed to cover the entire surface of the magnetic particle 31, and then the surface may be etched to remove only the alloy of VN, Si3N4, YN, or TiN deposited on the (001) surface 311B of the magnetic particle 31, so that the alloy of VN, Si3N4, YN, or TiN covers only the (111) surface 311C, and the layer 50 of the alloy of VN, Si3N4, YN, or TiN is provided only on the (111) surface 311C.

[0051] On the etched surface of any of the VN, Si3N4, YN, or TiN alloys, nitrogen contained in the VN, Si3N4, YN, or TiN alloy is more easily separated, which has the effect of filling the nitrogen deficiencies in the hexagonal boron nitride grain boundaries 42 of the second magnetic layer 40 that is subsequently formed. As a result, when the hexagonal boron nitride grain boundaries 42 are chemically analyzed by X-ray photoelectron spectroscopy (XPS), the position of the peak obtained can be shifted to around 191 eV, which is derived from the nitrided hexagonal boron nitride. The hexagonal boron nitride grain boundaries 42 that have undergone nitriding have better crystallinity, making it easier to separate the magnetic particles of hexagonal boron nitride and to grow columnar hexagonal boron nitride.

[0052] Since the magnetic particles 31 contained in the first magnetic layer 30 and the magnetic particles 41 contained in the second magnetic layer 40 form columnar crystals, it is preferable to increase the c-axis orientation, i.e., the orientation of the (001) plane, with respect to the substrate 10.

[0053] One method for orienting the magnetic particles 31 contained in the first magnetic layer 30 and the magnetic particles 41 contained in the second magnetic layer 40 along the c axis with respect to the substrate 10 is to use a base layer 20 to epitaxially grow the first magnetic layer 30 and the second magnetic layer 40 in the c axis direction.

[0054] Another magnetic layer may be provided below the first magnetic layer 30 or on top of the second magnetic layer 40. The newly provided magnetic layer preferably contains magnetic particles having an L10 structure, similar to the first magnetic layer 30. Furthermore, it is preferable that these magnetic particles form columnar crystals with the magnetic particles 31 and 41.

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

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

[0057] Examples of protective layers include hard carbon films.

[0058] Methods for forming a protective layer include, for example, the RF-CVD (Radio Frequency-Chemical Vapor Deposition) method, which involves decomposing hydrocarbon gas (source gas) with high-frequency plasma to form a film; the IBD (Ion Beam Deposition) method, which involves ionizing the source gas with electrons emitted from a filament to form a film; and the FCVA (Filtered Cathodic Vacuum Arc) method, which involves forming a film using a solid carbon target without using a source 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 levitation characteristics of the magnetic head will be good, and if it is 6 nm or less, the magnetic spacing will be reduced, and the SNR (signal-to-noise ratio, also called S / N ratio) of the magnetic recording medium 1 will be improved.

[0060] In this specification, the thickness of the protective layer refers to the length perpendicular to the main surface of the protective layer. The thickness of the protective layer is, for example, the thickness measured at any point in the cross-section of the protective layer. If several measurements are taken at any point in the cross-section of the protective layer, the average of the thicknesses at these measurement points may be used. The same measurement method as for the thickness of the protective layer can be used for other layers.

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

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

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

[0064] The magnetic recording medium 1 may include any additional layers besides the protective layer and lubricant layer. 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 layers of the substrate 10, the underlayer 20, and the first magnetic layer 30 as needed. The soft magnetic underlayer may consist of, 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 two or more layers (for example, a first orientation control layer, a second orientation control layer, etc.). The materials used to form the adhesion layer, soft magnetic underlayer, orientation control layer, etc., can be general materials used for magnetic recording media.

[0065] Thus, the magnetic recording medium 1 comprises 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 contains magnetic particles 31 having an L10 structure, and the second magnetic layer 40 is a granular magnetic layer containing magnetic particles 41 having an L10 structure and hexagonal boron nitride grain boundaries 42, with hexagonal boron nitride contained in the hexagonal boron nitride grain boundaries 42. The (111) plane 311C of the magnetic particles 31 has an interface with the second magnetic layer 40 covered with an alloy of VN, Si3N4, YN, or TiN, and the magnetic particles 41 are epitaxially grown from the (001) plane 311B of the magnetic particles 31. Furthermore, the magnetic particles 31 and 41 are formed to be columnar crystals that penetrate the first magnetic layer 30 and the second magnetic layer 40. Therefore, the particle sizes of the magnetic particles 31 and 41 are small and minute, and the magnetic particles 31 and 41 are formed in a columnar shape, continuously extending in one direction.

[0066] The magnetic recording medium 1 can increase anisotropy by reducing the particle size of the magnetic particles 31 and 41 contained in the first magnetic layer 30 and the second magnetic layer 40, respectively, and by including the magnetic particles 31 and 41 in a state where they are continuously connected in the same direction. Therefore, the magnetic recording medium 1 can stably maintain a state in which a granular structure is formed inside the second magnetic layer 40, and can stably include 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 characteristics described above, even when using a heat-assisted recording method or a microwave-assisted recording method, the first magnetic layer 30 and the second magnetic layer 40 have a high recording density, so that magnetic information can be sufficiently recorded in the first magnetic layer 30 and the second magnetic layer 40 by the recording magnetic field of the magnetic head. Therefore, the magnetic recording medium 1 can be suitably used in magnetic recording and playback devices that have an even higher recording density.

[0068] [Magnetic storage device] A magnetic storage device (also referred to as a "magnetic recording and playback device") equipped with a magnetic recording medium according to this embodiment will be described. The form of the magnetic storage device according to this embodiment is not particularly limited as long as it has a magnetic recording medium according to this embodiment. Here, we will describe the case in which the magnetic storage device records magnetic information on the magnetic recording medium using a heat-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 provided with a near-field light generating element at its tip, a magnetic head drive unit that drives and moves the magnetic head, and a recording / reproduction signal processing system.

[0070] The magnetic head is a heat-assisted recording magnetic head, and for example, it has 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] Figure 3 shows a perspective view of an example of a magnetic storage device using a magnetic recording medium according to this embodiment. As shown in Figure 3, the magnetic storage device 100 may 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 / reproduction signal processing unit 105. The magnetic recording medium 101 is the magnetic recording medium 1 described above.

[0072] Figure 4 schematically shows an example of a magnetic head 103. As shown in Figure 4, the magnetic head 103 has a recording head 110 and a playback head 120.

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

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

[0075] As shown in Figure 3, the magnetic storage device 100 has the center of the magnetic recording medium 101 attached to the rotation axis of the spindle motor, and the magnetic head 103 levitates and travels on the surface of the magnetic recording medium 101, which is rotated by the spindle motor, while writing or reading information to or from the magnetic recording medium 101.

[0076] In this embodiment, the magnetic storage device 100 can increase the recording capacity of the magnetic recording medium 101 by using the magnetic recording medium 1 as the magnetic recording medium 101, thereby increasing the areal recording density of the magnetic recording medium 101.

[0077] Furthermore, the magnetic memory device may use a microwave-assisted recording magnetic head instead of a heat-assisted recording magnetic head for the magnetic head 103.

[0078] As described above, embodiments have been presented, but these embodiments are provided as examples only, and the present disclosure is not limited by these embodiments. The above embodiments can be implemented in various other forms, and various combinations, omissions, substitutions, and modifications are possible without departing from the spirit of the invention. The above embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Examples]

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

[0080] <Manufacturing of magnetic recording media> (Example 1) On a glass substrate, a 100 nm thick Cr-50at%Ti alloy layer and a 30 nm thick Co-27at%Fe-5at%Zr-5at%B alloy layer were sequentially formed as underlayers by sputtering. Next, after heating the glass substrate to 250°C, a 10 nm thick Cr layer and a 5 nm thick MgO layer were sequentially formed by sputtering. Then, after heating the glass substrate to 450°C, a 0.5 nm thick (Fe-48at%Pt-5at%B) alloy layer (first magnetic layer) was formed by sputtering.

[0081] Subsequently, a 0.2 nm thick VN layer was deposited as a coating layer for the (111) surface using RF sputtering. The deposition conditions were a target surface potential of 100 V and a deposition rate of 0.08 nm / second, with the post-annealing temperature being approximately 100°C higher than the deposition temperature.

[0082] Subsequently, etching was performed in an argon atmosphere at 0.5 Pa with a power of 7 W.

[0083] This resulted in a structure in which the (111) plane of the magnetic particles in the first magnetic layer is covered with a VN layer.

[0084] Subsequently, a 13 nm thick (Fe-49at%Pt)-40 volume% hexagonal boron nitride layer (second magnetic layer) was sequentially formed using the sputtering method. Next, a 3 nm thick carbon film was formed as a protective layer to fabricate a 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 2-26, Comparative Examples 1-12) A magnetic recording medium was fabricated in the same manner as in Example 1, except that the coating conditions for the first magnetic layer were changed to the coating conditions shown in Table 1.

[0087] <Evaluation of magnetic recording media> The magnetic recording media produced in each example and comparative example were evaluated. The evaluation involved confirming the coating state of the (111) plane of the magnetic particles in the first magnetic layer by a layer of one of the alloys VN, Si3N4, YN, or TiN, and the crystallinity of hexagonal boron nitride (also known as hBN), as well as measuring the coercivity Hc of the magnetic recording media and the center distance between the magnetic particles in the first magnetic layer.

[0088] (The coating state of the (111) plane of the magnetic particles in the first magnetic layer by a layer of one of the alloys VN, Si3N4, YN, or TiN) The coating state of the (111) plane of the magnetic particles in the first magnetic layer by a layer of one of the alloys VN, Si3N4, YN, or TiN was evaluated by observing the cross-section of the magnetic recording medium using a transmission electron microscope (HD2300, Hitachi High-Tech Corporation). If the thickness of the layer of one of the alloys VN, Si3N4, YN, or TiN was not uniform and connections were observed between the magnetic particles, it was evaluated as deterioration of the coating quality.

[0089] (Crystallization 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, Hitachi High-Tech Corporation), observing the lattice fringes, and determining the position of the peaks in the XPS spectrum obtained during chemical composition analysis by XPS. When crystalline materials are observed 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, observing the lattice fringes, and confirming the position of the peaks in the XPS spectrum using XPS, the crystallinity of the hexagonal boron nitride in the first magnetic layer can be confirmed. If a 191 eV peak originating from hexagonal boron nitride is observed in the XPS spectrum, it can be said that the crystallinity of the hexagonal boron nitride is good. If the crystallinity of the hexagonal boron nitride is good, it can be evaluated that the granular structure formed inside the second magnetic layer is stably maintained, and the second magnetic layer functions as a granular magnetic layer.

[0090] (Distance between the centers of magnetic particles in the first magnetic layer) The center distance between magnetic particles in the first magnetic layer was obtained by calculating the center distance (in nm) between the centers of gravity of adjacent magnetic particles in the first magnetic layer from the surface observation image obtained by SEM. A smaller center distance between magnetic particles indicates a smaller particle size. Therefore, a smaller center distance between magnetic particles in the first magnetic layer indicates a smaller particle size and improved areal recording density. A center distance of 9.5 nm or less was considered good. To evaluate the particle size of the magnetic particles, an argon etching treatment of 1 minute was performed to remove the carbon protective film on the surface of the magnetic recording medium.

[0091] (Coercivity Hc of magnetic recording media) The coercivity Hc of the magnetic recording medium was evaluated by measuring the Kerr rotation angle (unit: "kOe") when laser light (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 thought that the coercivity Hc decreases when the crystal structure of the first and second magnetic layers is disordered. Therefore, the higher the coercivity Hc, the higher the crystallinity of the first and second magnetic layers, and the higher the areal recording density can be evaluated. A coercivity Hc of 32.5 kOe or higher was evaluated as good for the magnetic recording medium.

[0092] Table 1 shows the coating state of the (111) plane of the magnetic particles of the first magnetic layer with one of the following layers: VN, Si3N4, YN, or TiN, the evaluation results of the crystallinity of hexagonal boron nitride, and the measurement results of the inter-center distance between magnetic particles in the first magnetic layer and the coercivity Hc of the magnetic recording medium. In Table 1, the 191 eV peak originating from hexagonal boron nitride is indicated as the "hBN peak" to represent the crystallinity of hexagonal boron nitride.

[0093] [Table 1]

[0094] [Table 2]

[0095] [Table 3]

[0096] Tables 1-3 show that the magnetic recording media of each example exhibited better crystallinity of the hexagonal boron nitride in the first magnetic layer compared to the magnetic recording media of each comparative example, and were able to achieve a coercivity Hc of 32 kOe or more even when the center distance between magnetic particles in the first magnetic layer was 9.0 nm or less. Furthermore, among the comparative examples, in Comparative Examples 2 and 8, the center distance between magnetic particles in the first magnetic layer was large, at 10.5 nm or more. This prevented the reduction of the bit size of the magnetic recording media, and therefore the inability to increase the areal recording density of the magnetic recording media.

[0097] Therefore, it was confirmed that by coating the (111) plane of the magnetic particles in the first magnetic layer with a layer of one of the alloys VN, Si3N4, YN, or TiN, even if the particle size of the magnetic particles contained in the first and second magnetic layers is small, the first magnetic layer can maintain a state in which a granular structure is formed inside it and function as a granular magnetic layer, thereby further improving the areal recording density. Consequently, since the magnetic recording media of each embodiment have a high areal recording density, it can be said that they can have a high recording capacity when used in magnetic storage devices. [Explanation of symbols]

[0098] 1.101 Magnetic recording media 10 circuit boards 20 Base layer 30 First magnetic layer 31, 41 magnetic particles 40 Second magnetic layer 42. Hexagonal boron nitride grain boundary (grain boundary) 50 layers of one of the following alloys: VN, Si3N4, YN, or TiN 100 Magnetic storage devices 311A Growth aspect 42A, 50A, 311B (001) surfaces 311C (111) surface

Claims

1. The device comprises a substrate, an underlayer, a first magnetic layer, and a second magnetic layer, in this order. The first magnetic layer is L1 ０ It contains magnetic particles having a structure, The second magnetic layer is L1 ０ It comprises magnetic particles having a structure and a granular structure having grain boundaries containing hexagonal boron nitride, The (111) plane of the magnetic particles contained in the first magnetic layer has VN and Si at the interface with the second magnetic layer. ３ N ４ , covered with either an alloy of YN or TiN, The magnetic particles contained in the second magnetic layer are epitaxially grown from the (001) plane of the magnetic particles contained in the first magnetic layer. A magnetic recording medium wherein the magnetic particles contained in the first magnetic layer and the magnetic particles contained in the second magnetic layer are columnar crystals that penetrate the first magnetic layer and the second magnetic layer, respectively.

2. L1 ０ The magnetic recording medium according to claim 1, wherein the structured magnetic particles are FePt alloy particles.

3. The device comprises a substrate, an underlayer, a first magnetic layer, and a second magnetic layer, in this order. The first magnetic layer is L1 ０ It contains magnetic particles having a structure, The second magnetic layer is L1 ０ It comprises magnetic particles having a structure and a granular structure having grain boundaries containing hexagonal boron nitride, The (111) plane of the magnetic particles contained in the first magnetic layer is covered with an alloy of any one of VN, Si ３ N ４ , YN or TiN at the interface with the second magnetic layer, The magnetic particles contained in the second magnetic layer are epitaxially grown from the (001) plane of the magnetic particles contained in the first magnetic layer. A method for manufacturing a magnetic recording medium, wherein the magnetic particles contained in the first magnetic layer and the magnetic particles contained in the second magnetic layer are columnar crystals that penetrate the first magnetic layer and the second magnetic layer, respectively. Between the step of forming the first magnetic layer by sputtering and the step of forming the second magnetic layer by sputtering, VN and Si ３ N ４ A method for manufacturing a magnetic recording medium, comprising the step of forming a layer of an alloy of YN or TiN.

4. A magnetic storage device having the magnetic recording medium described in claim 1 or 2.

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