Magnetic Recording Medium, Method of Manufacturing the Magnetic Recording Medium, and Magnetic Storage Device

Abstract

An object of the present invention is to provide a magnetic recording medium capable of containing magnetic particles having a fine crystal grain size on the surface layer and in the vicinity thereof of a magnetic recording layer. The magnetic recording medium according to the present invention includes a substrate and a magnetic recording layer containing magnetic particles having an L10 structure, the magnetic recording layer is (001)-oriented, the growth surface of the magnetic recording layer has a (001) plane, a (111) plane, and equivalent planes thereof, and the area ratio of the (111) plane and the equivalent planes thereof in the growth surface (((111) plane + (111) equivalent planes) / ((001) plane + (111) plane + (111) equivalent planes)) is 0.2 to 0.7.

Description

Technical Field

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

[0002] Generally, a magnetic recording medium includes a substrate and a magnetic recording layer laminated in sequence. As a method for recording magnetic information on the magnetic recording medium, there are a heat-assisted recording method or a microwave-assisted recording method in which a laser or microwave is irradiated onto the magnetic recording medium to locally reduce the coercive force for recording. These assisted recording methods can achieve a high areal recording density of the order of 2 Tbit / inch 2 level, and thus, with the miniaturization and high recording density of the magnetic recording medium, it has been studied as a next-generation recording method capable of increasing the storage capacity.

[0003] In such an assisted recording method, a magnetic recording medium having a magnetic recording layer with a coercive force of several tens of kOe at room temperature can be used. Therefore, as the magnetic particles included in the magnetic recording layer, magnetic particles having a high crystalline magnetic anisotropy constant (Ku) can be used. As magnetic particles with a high Ku, FePt alloy particles having a Ku of about 7×10 6 J / m 3 or so, CoPt alloy particles having a Ku of about 5×10 6 J / m 3 or so, and other magnetic particles having an L10 structure are known.

[0004] As a magnetic recording medium having a magnetic recording layer containing magnetic particles with a high Ku, for example, a magnetic recording medium including a magnetic layer containing FePt or CoPt having an L10 structure as a main component on a plurality of base layers such as an MgO base layer formed on a substrate is disclosed (for example, refer to Patent Document 1).

[0005] In addition, it has been reported that (111) planes appear on the side surfaces of FePt particles on MgO (for example, refer to Non-Patent Document 1).

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2016-26368

[0009] Non-Patent Documents

[0010] Non-Patent Document 1: PHYSICAL REVIEW APPLIED 9, 034023 (2018) Summary of the Invention

[0011] Problems to be Solved by the Invention

[0012] In the case of writing information to a magnetic layer that constitutes a magnetic recording layer of a magnetic recording medium, the magnetic layer is magnetized in magnetic particle units. Therefore, in order to increase the recording density of the magnetic recording medium, it is important to make the magnetic particles finer. On the other hand, at the initial stage of growth of the magnetic layer, the nucleation density of the magnetic particles is high. However, after entering the middle stage of growth, there is a problem that the magnetic particles combine with each other, the nucleation density decreases, the crystal grain size increases, and the magnetic particles coarsen.

[0013] An object of one aspect of the present invention is to provide a magnetic recording medium capable of including magnetic particles having a fine crystal grain size in the surface layer and its vicinity of the magnetic recording layer.

[0014] Method for solving the problem

[0015] One aspect of the magnetic recording medium according to the present invention includes a substrate and a magnetic recording layer containing magnetic particles having an L10 structure. The magnetic recording layer is (001)-oriented, the growth surface of the magnetic recording layer has (001) plane, (111) plane and their equivalent planes, and the area ratio of the (111) plane and its equivalent planes in the growth surface ((((111) plane + (111) equivalent plane) / ((001) plane + (111) plane + (111) equivalent plane)))) is 0.2 to 0.7.

[0016] Another aspect of the magnetic recording medium according to the present invention includes a substrate and a magnetic recording layer containing magnetic particles having an L10 structure. The magnetic recording layer is (001)-oriented, the growth surface of the magnetic recording layer has (001) plane, (111) plane and their equivalent planes, and the Rku in the growth surface is 4 to 5.

[0017] In one aspect of the method for manufacturing a magnetic recording medium according to the present invention, on a substrate, a magnetic recording layer containing magnetic particles having an L10 structure and having (001) orientation is formed with (001) plane, (111) plane and their equivalent planes as the growth surface, and the area ratio of the (111) plane and its equivalent planes in the growth surface ((((111) plane + (111) equivalent plane) / ((001) plane + (111) plane + (111) equivalent plane)))) is 0.2 to 0.7. Then, a protective film is formed on the magnetic recording layer, and the surface of the protective film is polished so that the Rku becomes 2.5 to 3.5.

[0018] In another aspect of the method for manufacturing a magnetic recording medium according to the present invention, on a substrate, a magnetic recording layer containing magnetic particles having an L10 structure and having a (001) orientation is formed with the (001) plane, (111) plane, and their equivalent planes as growth planes, and the Rku in the above growth plane is 4 to 5. Then, a protective film is formed on the magnetic recording layer, and the surface of the protective film is polished so that the Rku is 2.5 to 3.5.

[0019] Effects of the Invention

[0020] According to one aspect of the magnetic recording medium of the present invention, magnetic particles having a fine crystal grain size can be included in the surface layer and its vicinity of the magnetic recording layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram showing a crystal plane when magnetic particles having an L10 structure are (001)-oriented.

[0022] Figure 2 It is a graph showing the relationship between the crystal shape (height of a frustum of a square pyramid) and the ratio of the (111) plane and its equivalent planes in the case of using an FePt alloy having an L10 structure.

[0023] Figure 3 It is a graph showing the region where the ratio of the (111) plane and its equivalent planes is 0.2 to 0.7.

[0024] Figure 4 It is a graph showing an example of the layer structure of the magnetic recording medium according to the present embodiment.

[0025] Figure 5 It is a perspective view showing an example of a magnetic storage device using the magnetic recording medium according to the embodiment of the present invention.

[0026] Figure 6 It is a schematic diagram showing an example of a magnetic head.

[0027] Description of Reference Numerals

[0028] 1, 101 Magnetic recording medium

[0029] 10 Substrate

[0030] 20 Base layer

[0031] 30 Magnetic recording layer

[0032] 100 Magnetic storage device DETAILED DESCRIPTION OF THE INVENTION

[0033] Hereinafter, embodiments of the present invention will be described in detail. In addition, for easier understanding of the description, the same reference numerals are assigned to the same components in the respective drawings, and repeated descriptions are omitted. In addition, the scales of the respective components in the drawings may sometimes be different from the actual ones. In this specification, "~" indicating a numerical range means including the values described before and after it as the lower limit value and the upper limit value, unless otherwise specified.

[0034] <Magnetic Recording Medium>

[0035] The magnetic recording medium according to this embodiment has, on a substrate, a magnetic recording layer containing magnetic particles as a magnetic material having an L10 structure, and the magnetic recording layer is (001)-oriented. By orienting the magnetic particles having an L10 structure contained in the magnetic recording layer in the (001) direction, the magnetic recording layer obtains a high degree of regularity.

[0036] In this embodiment, when growing the magnetic particles in the (001) orientation, the growth is carried out in such a way that the growth surface has a (001) plane, a (111) plane, and their equivalent planes.

[0037] Figure 1 FIG. is a schematic diagram showing the crystal planes when orienting magnetic particles having an L10 structure in the (001) direction. If the magnetic particles having an L10 structure are grown in such a way that the (001) plane and the (111) plane are also present, then Figure 1 the crystal shown as a frustum of a square pyramid is formed. As equivalent planes of the (111) plane, (-111) plane, (1-11) plane, and (-1-11) plane are generated. If the growth is carried out in such a way that the (001) plane disappears, the crystal becomes a square pyramid. If the growth is carried out in such a way that the (111) plane disappears, a flat crystal with only the (001) plane in the shape of a square is formed.

[0038] In this embodiment, the area ratio of the (111) plane and its equivalent planes in the growth surface, that is, the value obtained by dividing the area of the (111) plane and the (111) equivalent planes by the total area of the (001) plane, the (111) plane, and the (111) equivalent planes, is preferably 0.2 to 0.7, more preferably 0.25 to 0.6, and further preferably 0.3 to 0.6. In this embodiment, by configuring the magnetic particles contained in the magnetic recording layer as described above, the aggregation of magnetic particles can be suppressed, and thus the coarsening of magnetic particles can be suppressed. Therefore, the magnetic recording medium can reduce the increase in the particle diameter of the magnetic particles contained in the magnetic recording layer.

[0039] If the area ratio of the (111) plane and its equivalent planes in the growth plane is 0.2 or more, the distance to the (001) plane of adjacent particles increases, and thus the bonding between the (001) planes of adjacent particles is suppressed. On the other hand, if the area ratio of the (111) plane and its equivalent planes in the growth plane is less than 0.2, the distance to the (001) plane of adjacent magnetic particles approaches, the (001) planes of adjacent magnetic particles bond to each other, and the magnetic particles tend to coarsen. In addition, if the area ratio of the (111) plane and its equivalent planes in the growth plane is greater than 0.7, the unevenness of the growth plane increases, the surface smoothness of the magnetic recording medium deteriorates, and thus the floating movement stability of the magnetic head decreases and the electromagnetic conversion characteristics deteriorate.

[0040] An example of a method for manufacturing a magnetic recording medium according to the present embodiment is illustrated.

[0041] In the magnetic recording medium according to the present embodiment, for example, the magnetic layer included in the magnetic recording layer has a granular structure including a grain boundary portion that makes the magnetic particles and their surroundings non-magnetic, and this can be achieved by gradually reducing the volume ratio of the grain boundary portion during the film formation of the magnetic layer. In addition, the magnetic recording layer can have a multilayer structure, and the volume ratio of the grain boundary portion in each magnetic layer can be gradually reduced.

[0042] In addition, the magnetic recording layer can have a multilayer structure and include a vacuum heating process between the film formation processes of each layer. In magnetic particles having an L10 structure, the (111) plane and its equivalent planes are the most closely packed planes, and thus it is easy to dilute the crystal plane in a vacuum. Therefore, by vacuum heating the growth plane of the magnetic particles, the growth of the magnetic particles can be promoted.

[0043] The area ratio can be calculated by observing the cross-section of the magnetic recording medium using TEM. That is, the crystal plane having an inclination of about 53° with respect to the substrate plane is the (111) plane and its equivalent planes, and the crystal plane horizontal with respect to the substrate plane is the (001) plane. Therefore, the ratio can be calculated by observing the cross-section using TEM.

[0044] In addition, the ratio of the (111) plane and its equivalent planes to the (001) plane in the growth plane can also be measured by azimuth measurement of atomic scattering surface analysis. That is, the measurement sample can be rotated in the azimuth direction, the scattering intensity at each angle can be measured, and the ratio of each crystal plane can be understood from the axis azimuth and symmetry of the measurement sample surface.

[0045] Figure 2It shows the relationship between the crystal shape (height of frustum of a square pyramid) and the ratio of the (111) plane and its equivalent planes when using an FePt alloy as magnetic particles having an L10 structure. The (111) plane of the FePt alloy is an isosceles triangle with a base angle of 53° and a vertex angle of 74°. Therefore, when the horizontal axis is 100%, the crystal shape becomes a frustum of a square pyramid, and when it is zero, it becomes a plane (square).

[0046] In the case of an FePt alloy, when the ratio of the (111) plane and its equivalent planes is in the range of 0.2 to 0.7, it is at a position approximately 10% to 40% below the frustum of a square pyramid ( Figure 3 in the shaded part). Thus, by observing the cross-section of the magnetic recording medium using TEM to measure the height of the frustum of a square pyramid constituting the magnetic particles, the area ratio can be calculated.

[0047] In addition, the magnetic recording medium according to the present embodiment can also be defined by kurtosis (RKu).

[0048] That is, the magnetic recording medium according to the present embodiment has, on a substrate, a magnetic recording layer containing magnetic particles having an L10 structure, and the magnetic particles are (001)-oriented and have (001) plane, (111) plane, and their equivalent planes as growth surfaces. Moreover, the magnetic particles have Rku of the growth surface in the range of 4 to 5.

[0049] RKu represents the sharpness of the unevenness of the planes of the crystals contained in the magnetic particles. When the plane has an average sharpness, Rku becomes 3 (Rku = 3), when the plane has no sharpness like a polished surface, RKu is less than 3 (RKu < 3), and when the plane has sharp unevenness, RKu exceeds 3 (RKu > 3).

[0050] According to the research of the inventors of the present application, it was found that when the magnetic recording layer containing magnetic particles having an L10 structure is (001)-oriented in such a way as to have (001) plane, (111) plane, and their equivalent planes, and the area ratio of the (111) plane and its equivalent planes (((111) plane + (111) equivalent plane) / ((001) plane + (111) plane + (111) equivalent plane))) is in the range of 0.2 to 0.7, the Rku of its growth surface becomes 4 to 5.

[0051] If RKu of the growth surface of the magnetic particles contained in the magnetic recording layer is less than 4, the magnetic particles combine with each other and the magnetic particles coarsen. On the other hand, if RKu of the growth surface of the magnetic particles is greater than 5, the surface of the magnetic recording layer becomes rough, the surface smoothness of the magnetic recording medium deteriorates, and the electromagnetic conversion characteristics deteriorate.

[0052] RKu in the growth surface of the magnetic recording layer can be calculated by observing the cross-section of the magnetic recording medium using TEM. In addition, in the manufacturing process of the magnetic recording medium, a sample after forming the magnetic recording layer can be taken out, and its surface can be measured using a general roughness measuring device such as a non-contact roughness meter to identify it.

[0053] Figure 4 Fig. 4 shows an example of the layer structure of the magnetic recording medium according to this embodiment. As Figure 4 shown, the magnetic recording medium 1 has a substrate 10, an underlayer 20, and a magnetic recording layer 30.

[0054] The substrate 10 can use the substrates generally used in magnetic recording media. As the substrate 10, for example, a heat-resistant glass substrate with a softening temperature of 500 °C or higher, preferably 600 °C or higher, is preferably used. When manufacturing the magnetic recording medium 1, the substrate 10 is sometimes heated to a temperature of 500 °C or higher, so that it can have a heat-resistant glass substrate even when heated to 500 °C or higher.

[0055] If the underlayer 20 can be a layer containing MgO and can orient the magnetic particles with the L10 structure contained in the magnetic recording layer 30 in the (001) direction, it can be a multilayer structure containing other layers.

[0056] The underlayer 20 preferably contains an NaCl-type compound. As the NaCl-type compound, in addition to MgO, for example, TiO, NiO, TiN, TaN, HfN, NbN, ZrC, HfC, TaC, NbC, TiC, etc. can be cited. They can be used alone or in combination of two or more.

[0057] The magnetic recording layer 30 contains magnetic particles having an L10 structure. As the magnetic particles having an L10 structure, for example, FePt alloy particles, CoPt alloy particles, etc. can be cited.

[0058] The particle size of the magnetic particles is preferably 3 nm to 10 nm, more preferably 4 nm to 7 nm. In addition, the particle size of the magnetic particles can be measured by observing the plane using TEM.

[0059] The distance between magnetic particles is preferably 4 nm to 12 nm, more preferably 5 nm to 9 nm. In addition, the distance between magnetic particles refers to the distance between the centers of gravity of adjacent magnetic particles. The distance between magnetic particles can be measured by observing the plane using TEM.

[0060] In addition, the magnetic recording layer 30 can have a granular structure including grain boundary portions.

[0061] In the case where the magnetic recording layer 30 has a granular structure, the content of the grain boundary portion in the magnetic recording layer 30 is preferably 25 vol% to 50 vol%, more preferably 35 vol% to 45 vol%. If the content of the grain boundary portion in the magnetic recording layer 30 is within the above preferred range, the anisotropy of the magnetic particles contained in the magnetic recording layer 30 can be improved.

[0062] Here, the grain boundary portion can contain carbides, nitrides, oxides, borides, etc. Specifically, BN, B4C, C, MoO3, GeO2, etc. can be cited.

[0063] The magnetic particles are preferably c-axis oriented, that is, (001) oriented, with respect to the substrate 10.

[0064] The thickness of the magnetic recording layer 30 is preferably 8 nm to 20 nm, more preferably 10 nm to 18 nm, and further preferably 10 nm to 15 nm. If the thickness of the magnetic recording layer 30 is within the above preferred range, high recording density can be achieved.

[0065] In addition, in this specification, the thickness of the magnetic recording layer 30 refers to the length in the direction perpendicular to the main surface of the magnetic recording layer 30. For example, the thickness of the magnetic recording layer 30 is the thickness measured at an arbitrary location in the cross-section of the magnetic recording layer 30. In the case where several locations are measured at arbitrary locations in the cross-section of the magnetic recording layer 30, the average value of the thicknesses measured at these locations can be adopted. Hereinafter, the same measurement method as the thickness of the magnetic recording layer 30 can also be used for other layers.

[0066] The magnetic recording layer 30 can be formed on the base layer 20 by a sputtering method or the like.

[0067] The magnetic recording layer 30 can include one magnetic layer, or can include multiple magnetic layers stacked. In the case where the magnetic recording layer 30 includes multiple magnetic layers, each magnetic layer can be formed using the same type of material, or can be formed using different types of materials. In addition, a non-magnetic layer can be included between each magnetic layer. The non-magnetic layer can be formed using a general material used for magnetic recording media.

[0068] The magnetic recording medium 1 preferably further has a protective layer on the magnetic recording layer 30.

[0069] As the protective layer, for example, a hard carbon film, etc. can be cited.

[0070] Examples of the method for forming the protective layer include, for example, the RF-CVD (Radio Frequency-Chemical Vapor Deposition) method in which a hydrocarbon (source gas) is decomposed by high-frequency plasma and deposited, the IBD (Ion Beam Deposition) method in which the source gas is ionized by electrons emitted from an electron beam and deposited, and the FCVA (Filtered Cathodic Vacuum Arc) method in which a solid carbon target is used instead of a source gas for deposition.

[0071] The thickness of the protective layer is preferably 1 nm to 6 nm. If the thickness of the protective layer is 1 nm or more, the flying characteristics of the magnetic head become good, and if it is 6 nm or less, the magnetic gap becomes small and the SNR (Signal / Noise Ratio (S / N ratio)) of the magnetic recording medium 1 is improved.

[0072] The magnetic recording medium 1 may further have a lubricant layer on the protective layer.

[0073] The lubricant layer can be formed using a liquid lubricant layer. As the liquid lubricant, a fluororesin-based lubricant such as a perfluoropolyether-based lubricant containing a compound having a perfluoropolyether structure, which is chemically stable, has low friction, and has low adsorptivity, is preferably used.

[0074] The thickness of the lubricant layer is preferably in the range of 1 nm to 3 nm.

[0075] Thus, the magnetic recording medium according to the present embodiment includes, on a substrate, a magnetic recording layer containing magnetic particles as a magnetic material having an L10 structure, and the magnetic recording layer has a (001) orientation. Further, the growth surface of the magnetic recording layer has a (001) plane, a (111) plane, and their equivalent planes, and the area ratio of the (111) plane and its equivalent planes in the growth surface is 0.2 to 0.7. Thereby, from the initial stage to the later stage of growth of the magnetic recording layer, the aggregation of magnetic particles with each other is suppressed, whereby an increase in the crystal grain size can be suppressed and coarsening of the magnetic particles can be suppressed. Therefore, the crystal grain size of the magnetic particles present in the surface layer (upper layer) and the vicinity thereof of the magnetic recording layer in the later stage of growth as magnetic particles can be maintained substantially the same as the crystal grain size of the magnetic particles present in the lower layer and the vicinity thereof of the magnetic recording layer in the initial stage of growth as magnetic particles. Thus, the magnetic recording medium according to the present embodiment can include magnetic particles having a fine crystal grain size in the upper layer and the vicinity of the magnetic recording layer.

[0076] The magnetic recording medium according to the present embodiment can improve the surface smoothness of the growth surface of the magnetic recording layer by making the crystal grain size of the magnetic particles present in the surface layer and the vicinity thereof of the magnetic recording layer fine, and thereby can exhibit excellent electromagnetic conversion characteristics such as an increase in the recording density.

[0077] The magnetic recording medium according to this embodiment has a magnetic recording layer containing magnetic particles as a magnetic material having an L10 structure on a substrate, and the magnetic recording layer has a (001) orientation. Moreover, the growth surface of the magnetic recording layer has a (001) plane, a (111) plane, and their equivalent planes, and Rku in the growth surface is 4 to 5. In this case, similarly to the above, the crystal grain size of the magnetic particles existing in the surface layer (upper layer) and its vicinity of the magnetic recording layer in the late stage of growth of the magnetic particles can be maintained substantially the same as the crystal grain size of the magnetic particles existing in the lower layer and its vicinity of the magnetic recording layer at the initial stage of growth of the magnetic particles. Thus, the magnetic recording medium according to this embodiment can contain magnetic particles having a fine crystal grain size in the upper layer of the magnetic recording layer and its vicinity. The magnetic recording medium according to this embodiment can improve the surface smoothness of the growth surface of the magnetic recording layer, and thus can exhibit excellent electromagnetic conversion characteristics such as an increased recording density.

[0078] The magnetic recording medium according to this embodiment can have a crystal grain size of the magnetic particles of 8 nm or less and contains at least one component selected from the group consisting of FePt, CoPt, FePd, and CoPd. Thus, the magnetic recording medium according to this embodiment can improve the magnetic properties by making the crystal grain size of the magnetic particles fine. Thus, the magnetic recording medium according to this embodiment can further have a high recording density.

[0079] The manufacturing method of the magnetic recording medium according to this embodiment forms a magnetic recording layer containing magnetic particles having an L10 structure with a (001) orientation on a substrate, using a (001) plane, a (111) plane, and their equivalent planes as the growth surface, and the area ratio of the (111) plane and its equivalent planes in the growth surface is 0.2 to 0.7. Moreover, a protective film is formed on the magnetic recording layer, and the surface of the protective film is polished so that Rku becomes 2.5 to 3.5. Thus, at the time of forming the magnetic recording layer, from the initial stage to the late stage of growth of the magnetic particles, the combination of magnetic particles with each other is suppressed, so that an increase in the crystal grain size can be suppressed and coarsening of the magnetic particles can be suppressed. Therefore, the crystal grain size of the magnetic particles existing in the surface layer (upper layer) and its vicinity of the magnetic recording layer in the late stage of growth of the magnetic particles can be maintained substantially the same as the crystal grain size of the magnetic particles existing in the lower layer and its vicinity of the magnetic recording layer at the initial stage of growth of the magnetic particles. Thus, according to the manufacturing method of the magnetic recording medium according to this embodiment, the crystal grain size of the magnetic particles existing in the upper layer of the magnetic recording layer and its vicinity becomes small, and the magnetic particles can become fine. Since the surface smoothness of the growth surface of the obtained magnetic recording layer can be improved, a magnetic recording medium having excellent electromagnetic conversion characteristics such as an increased recording density can be obtained.

[0080] In the method for manufacturing a magnetic recording medium according to this embodiment, on a substrate, a magnetic recording layer containing magnetic particles having an L10 structure and having a (001) orientation is formed with the (001) plane, (111) plane, and their equivalent planes as growth planes, and the Rku in the growth plane is 4 to 5. Further, a protective film is formed on the magnetic recording layer, and the surface of the protective film is polished so that the Rku is 2.5 to 3.5. In this case, as in the above, the crystal grain size of the magnetic particles existing in the surface layer (upper layer) and the vicinity of the magnetic recording layer in the later stage of growth of the magnetic particles can be maintained substantially the same as the crystal grain size of the magnetic particles existing in the lower layer and the vicinity of the magnetic recording layer in the initial stage of growth of the magnetic particles. Thus, according to the method for manufacturing a magnetic recording medium according to this embodiment, the crystal grain size of the magnetic particles existing in the upper layer and the vicinity of the magnetic recording layer becomes smaller, and the magnetic particles can be made finer. Since the surface smoothness of the growth plane of the obtained magnetic recording layer can be improved, a magnetic recording medium having excellent electromagnetic conversion characteristics such as an increased recording density can be obtained.

[0081] The magnetic recording medium according to this embodiment has the above-described characteristics, so that the distance between the magnetic head and the magnetic recording medium is narrowed, and even if the flying height of the magnetic head is further reduced, it is possible to use while reducing the collision with the magnetic head 4. Thus, the magnetic recording and reproducing apparatus 1 can be suitably used for a magnetic recording and reproducing apparatus having an even higher recording density.

[0082] In addition, in the magnetic recording medium 1, any layer can be appropriately included in addition to the protective layer and the lubricant layer. For example, the magnetic recording medium 1 can appropriately include an adhesion layer, a soft magnetic base layer, an orientation control layer, etc. between the substrate 10 and the magnetic recording layer 30 as needed. The soft magnetic base layer can be composed of, for example, a first soft magnetic layer, an intermediate layer, and a second soft magnetic layer. The orientation control layer can be one layer or two or more layers (for example, a first orientation control layer, a second orientation control layer, etc.). Materials for forming the adhesion layer, the soft magnetic base layer, the orientation control layer, etc. can be general materials used for magnetic recording media.

[0083] [Magnetic storage device]

[0084] A magnetic storage device including the 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 the magnetic recording medium according to this embodiment. Here, a case where the magnetic storage device records magnetic information on the magnetic recording medium using a heat-assisted recording method will be described.

[0085] The magnetic storage device according to this embodiment can have, for example: a magnetic recording medium driving unit that rotates the magnetic recording medium according to this embodiment; a magnetic head provided with a near-field light generating element at its front end; a magnetic head driving unit that moves the magnetic head; and a recording / reproducing signal processing unit.

[0086] The magnetic head is a magnetic head for thermally assisted recording, and has, for example, a laser generating unit that generates a laser to heat the magnetic recording medium, and a waveguide that guides the laser generated by the laser generating unit to the near-field light generating element.

[0087] Figure 5 FIG. is a perspective view showing an example of a magnetic storage device using the magnetic recording medium according to this embodiment. As Figure 5 shown, the magnetic storage device 100 can have: a magnetic recording medium 101, a magnetic recording medium driving unit 102 that rotates the magnetic recording medium 101, a magnetic head 103 having a near-field light generating element at its front end, a magnetic head driving unit 104 that moves the magnetic head 103, and a recording / reproducing signal processing unit 105. The magnetic recording medium 101 uses the magnetic recording medium 1 according to the above-described embodiment.

[0088] Figure 6 FIG. is a schematic view showing an example of the magnetic head 103. As Figure 6 shown, the magnetic head 103 has a recording head 110 and a reproducing head 120.

[0089] 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 as a laser generating unit, and a waveguide 116 that transmits the laser L generated by the LD 114 to the near-field light generating element 115.

[0090] The reproducing head 120 has a shield 121 and a reproducing element 122 held by the shield 121.

[0091] As Figure 6 shown, the magnetic storage device 100 mounts the central portion of the magnetic recording medium 101 on the rotating shaft of the spindle motor, and while the magnetic head 103 floats and moves onto the surface of the magnetic recording medium 101 rotated by the spindle motor, information is written to or read from the magnetic recording medium 101.

[0092] The magnetic storage device 100 according to this embodiment can increase the recording density of the magnetic recording medium 101 by using the magnetic recording medium 1 according to this embodiment, and thus can improve the recording density.

[0093] In addition, in the magnetic storage device, the magnetic head 103 can be replaced with a magnetic head for thermally assisted recording, and a magnetic head for microwave-assisted recording can be used.

[0094] Example

[0095] Hereinafter, examples and comparative examples are shown to more specifically illustrate the embodiments, and the embodiments are not limited to these examples and comparative examples.

[0096] <Manufacture of Magnetic Recording Medium>

[0097] [Example 1]

[0098] On a MgO single crystal substrate with the (100) plane exposed, as a base layer, a Cr-50at%Ti alloy layer with a thickness of 100 nm and a Co-27at%Fe-5at%Zr-5at%B alloy layer with a thickness of 30 nm are sequentially formed. Next, after heating the glass substrate to 250 °C, a Cr layer with a thickness of 10 nm and a MgO-C layer with a thickness of 5 nm are sequentially formed. Next, after heating the MgO single crystal substrate to 450 °C, as a magnetic recording layer, a FePt-40mol%C (first magnetic layer) with a thickness of 1 nm is formed. Next, after annealing the substrate at 650 °C for 20 seconds in a high vacuum of 10 -5 Pa, a FePt-40mol%C (second magnetic layer) with a thickness of 2 nm is formed. Then, a FePt-16SiO2 (third magnetic layer) with a thickness of 3 nm and a FePt-25BN (fourth magnetic layer) with a thickness of 2 nm are formed. After annealing the substrate at 550 °C for 20 seconds at 3 Pa, a FePt-16SiO2 (fifth magnetic layer) with a thickness of 5 nm is formed.

[0099] Then, the average particle diameter of the magnetic particles, the average distance between adjacent magnetic particles (magnetic particle distance), the area ratio of the (111) plane and its equivalent planes (((111) plane + (111) equivalent plane) / ((001) plane + (111) plane + (111) equivalent plane))), and RKu are measured on the surface of the magnetic recording layer (the surface of the fifth magnetic layer).

[0100] Then, a carbon film with a thickness of 3 nm is formed as a protective layer. Then, using an alumina tape adhered with alumina abrasive grains with an average particle diameter of 1 μm, the surface of the protective layer is polished. The polishing conditions are that the rotation speed of the substrate is 500 revolutions per minute, the pressing force of the alumina tape on the substrate is 0.1 MPa, and the polishing time is 3 seconds. Then, RKu after polishing the surface of the protective layer is measured.

[0101] The measurement results of the crystal grain diameter, the distance between magnetic particles, the area ratio of the (111) plane and its equivalent planes, RKu on the surface of the magnetic recording layer, and RKu after polishing the surface of the protective layer are shown in Table 1.

[0102] [Examples 2 to 11, Comparative Examples 1 to 7]

[0103] In Example 1, the production conditions of the magnetic recording medium were changed as shown in Table 1, and the magnetic recording medium was manufactured and evaluated. Except for this, the operation was carried out in the same manner as in Example 1. The measurement results of the crystal grain size, the distance between magnetic particles, the area ratio of the (111) plane and its equivalent plane, RKu on the surface of the magnetic recording layer, and RKu after polishing the surface of the protective layer are shown in Table 1.

[0104] [Table 1]

[0105]

[0106] From Table 1, in Examples 1 to 11, the crystal grain size of the magnetic particles on the surface layer of the fifth magnetic layer was 8.7 nm or less. On the other hand, in Comparative Examples 1 to 7, the crystal grain size of the magnetic particles on the surface layer of the fifth magnetic layer was 9.3 nm or more.

[0107] Thus, the magnetic recording media of Examples 1 to 11 are different from the magnetic recording media of Comparative Examples 1 to 7, and the area ratio of the (111) plane and its equivalent plane on the surface of the magnetic recording layer is 23% to 63%. Thus, the magnetic recording media of Examples 1 to 11 can reduce the particle size of the magnetic particles contained in the surface layer and its vicinity of the fifth magnetic layer of the magnetic recording layer. Thus, it can be said that the magnetic recording media of Examples 1 to 11 can exhibit excellent electromagnetic conversion characteristics when used in a magnetic storage device.

[0108] As described above, the embodiments have been described, but the above embodiments 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, changes, etc. can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and its equivalents.

Claims

1. A magnetic recording medium comprising: a substrate, and a magnetic recording layer containing magnetic particles having an L10 structure, wherein the magnetic recording layer is (001)-oriented, the growth surface of the magnetic recording layer has a (001) plane, a (111) plane, and equivalent planes of the (111) plane, the (001) plane being a crystal plane horizontal with respect to the substrate plane, and the (111) plane and the equivalent planes of the (111) plane being crystal planes having an inclination of about 53° with respect to the substrate plane, the area ratio of the (111) plane and the equivalent planes of the (111) plane in the growth surface, i.e., ((111) plane + (111) equivalent plane) / ((001) plane + (111) plane + (111) equivalent plane)) is 0.2 to 0.

7.

2. A magnetic recording medium comprising: a substrate, and a magnetic recording layer containing magnetic particles having an L10 structure, wherein the magnetic recording layer is (001)-oriented, the growth surface of the magnetic recording layer has a (001) plane, a (111) plane, and equivalent planes of the (111) plane, the (001) plane being a crystal plane horizontal with respect to the substrate plane, and the (111) plane and the equivalent planes of the (111) plane being crystal planes having an inclination of about 53° with respect to the substrate plane, and Rku in the growth surface is 4 to 5.

3. The magnetic recording medium according to claim 1 or 2, wherein the crystal grain size of the magnetic particles is 8 nm or less and contains at least one component selected from the group consisting of FePt, CoPt, FePd, and CoPd.

4. A method for manufacturing a magnetic recording medium, wherein on a substrate, a magnetic recording layer containing magnetic particles having an L10 structure and being (001)-oriented is formed with a (001) plane, a (111) plane, and equivalent planes of the (111) plane as growth surfaces, and the area ratio of the (111) plane and the equivalent planes of the (111) plane in the growth surface, i.e., ((111) plane + (111) equivalent plane) / ((001) plane + (111) plane + (111) equivalent plane)) is 0.2 to 0.7, the (001) plane being a crystal plane horizontal with respect to the substrate plane, and the (111) plane and the equivalent planes of the (111) plane being crystal planes having an inclination of about 53° with respect to the substrate plane, then, a protective film is formed on the magnetic recording layer, and the surface of the protective film is polished to make Rku 2.5 to 3.

5.

5. A method for manufacturing a magnetic recording medium, wherein on a substrate, a magnetic recording layer containing magnetic particles having an L10 structure and being (001)-oriented is formed with a (001) plane, a (111) plane, and equivalent planes of the (111) plane as growth surfaces, and Rku in the growth surface is 4 to 5, the (001) plane being a crystal plane horizontal with respect to the substrate plane, and the (111) plane and the equivalent planes of the (111) plane being crystal planes having an inclination of about 53° with respect to the substrate plane, then, a protective film is formed on the magnetic recording layer, and the surface of the protective film is polished to make Rku 2.5 to 3.

5.

6. A magnetic storage device comprising the magnetic recording medium according to any one of claims 1 to 3.

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