Magnetic recording medium, magnetic recording / reproducing device, and method for manufacturing magnetic recording medium

Abstract

The invention provides a magnetic recording medium, a magnetic recording / reproducing apparatus, and a method of manufacturing the magnetic recording medium. The present invention addresses the problem of providing a magnetic recording medium having high corrosion resistance. A magnetic recording medium according to the present invention is provided with an underlayer, a perpendicular magnetic layer, a diffusion prevention layer, and a protective layer in this order on a non-magnetic substrate, the perpendicular magnetic layer having a multilayer structure, the uppermost layer of the perpendicular magnetic layer containing Co or Fe in magnetic particles, at least one layer other than the uppermost layer of the perpendicular magnetic layer containing an oxide, and the protective layer containing Co or Fe in magnetic particles. The diffusion prevention layer is provided between the perpendicular magnetic layer and the protective layer, and contains one or more components selected from the group consisting of Si, Ti, Cr, B, and Ru, or at least one of a carbide and an oxide thereof.

Description

[0001] This application is a divisional application, and the Chinese national application number of the application to which it is directed is 202210092809.6, the application date is January 26, 2022, and the name of the invention is “Magnetic recording medium, magnetic recording regeneration device, and method for manufacturing magnetic recording medium”. Technical Field

[0002] The present invention relates to a magnetic recording medium, a magnetic recording and reproducing device, and a method for manufacturing the magnetic recording medium. Background Art

[0003] Magnetic recording media are widely used as recording media for recording and storing various data. Magnetic recording media are generally composed of a base layer, a perpendicular magnetic layer, and a protective layer stacked in this order on a non-magnetic substrate.

[0004] In order to improve the recording density of a magnetic recording medium, the crystal orientation of a perpendicular magnetic layer is important. Therefore, a magnetic recording medium has been developed that uses a magnetic layer having a so-called granular structure in which columnar magnetic grains are covered with oxides or the like on a perpendicular magnetic layer.

[0005] As a magnetic recording medium using a magnetic layer having such a granular structure, for example, a magnetic recording medium is disclosed, which includes, on a non-magnetic substrate, at least an orientation control layer for controlling the orientation of a layer directly above and a perpendicular magnetic layer whose easy magnetization axis is oriented mainly perpendicularly to the non-magnetic substrate, wherein the perpendicular magnetic layer is formed of two or more magnetic layers, at least one of which is a layer containing Co as a main component and containing Pt and containing an oxide, and at least one other layer is a layer containing Co as a main component and containing Cr and not containing an oxide (for example, refer to patent document 1).

[0006] Prior art literature

[0007] Patent Literature

[0008] Patent Document 1: Japanese Patent Application Publication No. 2004-310910 Summary of the invention

[0009] Problems to be solved by the invention

[0010] Here, as the application range of magnetic recording and reproducing devices expands, the recording density of magnetic recording media is required to be further improved. As a method of improving the recording density of magnetic recording media, there is a method of increasing the film forming temperature of the perpendicular magnetic layer to improve the crystal orientation of the perpendicular magnetic layer.

[0011] However, if the film forming temperature during the formation of the perpendicular magnetic layer is increased, the elements constituting the perpendicular magnetic layer diffuse into other layers constituting the magnetic recording medium, thereby causing a change in the composition of the perpendicular magnetic layer, resulting in a reduction in magnetic properties, etc. In particular, the oxide contained in the perpendicular magnetic layer is thermally diffused to the surface of the magnetic recording medium due to heating during manufacturing, and there is a problem that impurities in the atmosphere penetrate into the interior of the magnetic recording medium through the diffusion path, causing the magnetic recording medium to corrode.

[0012] An object of one method of the present invention is to provide a magnetic recording medium having high corrosion resistance.

[0013] Methods for solving problems

[0014] A magnetic recording medium involved in a method of the present invention comprises, on a non-magnetic substrate, a base layer, a perpendicular magnetic layer, a diffusion prevention layer and a protective layer in sequence, wherein the perpendicular magnetic layer is a multi-layer structure, the uppermost layer of the perpendicular magnetic layer contains Co or Fe in magnetic particles, at least one layer other than the uppermost layer of the perpendicular magnetic layer contains an oxide, and the diffusion prevention layer is arranged between the perpendicular magnetic layer and the protective layer, and contains one or more components selected from the group consisting of Si, Ti, Cr, B and Ru, or at least one of their carbides and oxides.

[0015] Effects of the Invention

[0016] According to a method of the present invention, a magnetic recording medium having high corrosion resistance can be provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic cross-sectional view showing an example of the structure of the magnetic recording medium according to the present embodiment.

[0018] Figure 2 It is a schematic cross-sectional view showing an example of the structure of the magnetic recording medium according to the present embodiment.

[0019] Figure 3 It is a schematic diagram showing an example of a magnetic recording and reproducing device according to the present embodiment. DETAILED DESCRIPTION

[0020] The following is a detailed description of the embodiments of the present invention. In addition, in order to facilitate the understanding of the description, the same symbols are attached to the same components in each drawing, and repeated descriptions are omitted. In addition, the scales of the components in the drawings are sometimes different from the actual ones. In this specification, the wavy line "~" indicating the range of values ​​means that the values ​​recorded before and after it are included as the lower limit and upper limit unless otherwise specified.

[0021] <First embodiment>

[0022] [Magnetic recording media]

[0023] A magnetic recording medium according to a first embodiment of the present invention is described. The magnetic recording medium according to this embodiment includes a soft magnetic layer, a seed layer, a base layer, a perpendicular magnetic layer, a diffusion prevention layer, and a protective layer stacked in sequence from the non-magnetic substrate side on a non-magnetic substrate, and the perpendicular magnetic layer includes a CoCr alloy.

[0024] Figure 1 1 is a schematic cross-sectional view showing an example of the structure of the magnetic recording medium involved in this embodiment. Figure 1 As shown, the magnetic recording medium 10 includes a nonmagnetic substrate 11 , a soft magnetic layer 12 , a seed layer 13 , an underlayer 14 , a perpendicular magnetic layer 15 , a diffusion prevention layer 16 , and a protective layer 17 stacked in this order from the nonmagnetic substrate 11 side.

[0025] Examples of the material constituting the nonmagnetic substrate 11 include Al alloys such as AlMg alloys, soda glass, aluminosilicate glass, amorphous glass, silicon, titanium, ceramics, sapphire, quartz, and resins. Among these, Al alloys, crystallized glass, amorphous glass, and other glasses are preferred.

[0026] The soft magnetic layer 12 is provided on the nonmagnetic substrate 11 , and has a function of guiding the recording magnetic field from the magnetic head and efficiently applying the perpendicular component of the recording magnetic field to the perpendicular magnetic layer 15 when recording signals on the magnetic recording medium 10 .

[0027] Examples of the material constituting the soft magnetic layer 12 include soft magnetic alloys such as FeCo alloys, CoZrNb alloys, and CoTaZr alloys.

[0028] The soft magnetic layer 12 preferably has an amorphous structure. This can improve the surface smoothness of the soft magnetic layer 12, resulting in a reduction in the flying height of the magnetic head, and further improve the recording density of the magnetic recording medium 10.

[0029] Alternatively, the soft magnetic layer 12 may be formed into a multilayer film through non-magnetic layers such as Ru films to form an antiferromagnetic exchange bonding (AFC) film.

[0030] The total thickness of the soft magnetic layer 12 is appropriately determined by the balance between the recording and reproducing characteristics and the OW (Over Write) characteristics of the magnetic recording medium 10 , and is preferably 20 nm to 120 nm.

[0031] The seed layer 13 is provided on the soft magnetic layer 12 , and has a function of improving the (002) plane orientation of the base layer 14 .

[0032] As a material constituting the seed layer 13 , a material having an hcp structure, an fcc structure, or an amorphous structure is preferably used, and examples thereof include Ru-based alloys, Ni-based alloys, Co-based alloys, Pt-based alloys, and Cu-based alloys.

[0033] The thickness of the seed layer 13 is preferably in the range of 0.5 nm to 20 nm, and more preferably in the range of 3 nm to 10 nm. When the thickness of the seed layer 13 is in the above preferred range, the base layer 14 can be stably oriented in the (002) plane.

[0034] The underlayer 14 is provided on the seed layer 13 , and has a function of improving the (002) plane orientation of the perpendicular magnetic layer 15 .

[0035] As a material constituting the base layer 14 , Ru having an hcp structure or an alloy thereof can be used.

[0036] The average crystal grain size of the base layer 14 is preferably within a range of 6 nm to 20 nm, and more preferably within a range of 6 nm to 8 nm.

[0037] The thickness of the base layer 14 can be appropriately designed, and is preferably, for example, 5 nm to 30 nm.

[0038] The vertical magnetic layer 15 is provided on the base layer 14 to record information. The vertical magnetic layer 15 is a multilayer structure formed of an uppermost layer 151 and a layer 152 other than the uppermost layer. In this embodiment, the vertical magnetic layer 15 includes a CoCr alloy, so the uppermost layer 151 includes Co in the magnetic grains, and the layer 152 other than the uppermost layer includes an oxide. When the layer 152 other than the uppermost layer includes a plurality of layers, at least one layer of the layer 152 other than the uppermost layer only needs to include an oxide.

[0039] As a material constituting the vertical magnetic layer 15, for example, when the vertical magnetic layer 15 does not contain oxide, CoCr, CoCrPt, CoCrPtB, etc. can be cited. As a material constituting the vertical magnetic layer 15, when the vertical magnetic layer 15 contains oxide, CoCrPt-B2O3, CoCrPt-SiO2, CoCrPt-Cr2O3, CoCrPt-TiO2, CoCrPt-ZrO2, CoCrPt-Nb2O5, CoCrPt-Ta2O5, CoCrPt-TiO2, etc. can be cited.

[0040] When the perpendicular magnetic layer 15 includes an oxide, the oxide surrounds the crystal grains of the CoCr-based alloy to form a granular structure, thereby reducing the magnetic interaction between the crystal grains of the CoCr-based alloy and reducing noise.

[0041] As a method for forming the soft magnetic layer 12 , the seed layer 13 , the base layer 14 , and the perpendicular magnetic layer 15 , a DC magnetron sputtering method or an RF sputtering method can be used.

[0042] When forming the soft magnetic layer 12 , the seed layer 13 , the base layer 14 , and the perpendicular magnetic layer 15 , RF (Radio Frequency) bias, DC bias, pulse DC, pulse DC bias, etc. may be used as necessary.

[0043] As the reactive gas, O 2 gas, H 2 O gas, N 2 gas, etc. can be used.

[0044] The sputtering gas pressure is appropriately adjusted so that the characteristics of each layer are optimized, and is usually within the range of about 0.1 Pa to 30 Pa.

[0045] The diffusion prevention layer 16 is provided between the vertical magnetic layer 15 and the protective layer 17 of the multilayer structure, and has the function of preventing the oxide contained in the vertical magnetic layer 15 from diffusing to the surface of the magnetic recording medium 10. The diffusion prevention layer 16 prevents the oxide contained in the vertical magnetic layer 15 from diffusing to the surface of the magnetic recording medium 10, thereby eliminating the corrosion path of the magnetic recording medium 10 and improving the corrosion resistance.

[0046] According to the research of the inventors of the present application, it is noted that the oxide contained in the perpendicular magnetic layer 15 diffuses to the surface portion through the crystal grain boundaries of the perpendicular magnetic layer 15 and the protective layer 17, etc., by heating the non-magnetic substrate 11 when manufacturing the magnetic recording medium 10. Furthermore, through the diffusion path at this time, impurities in the atmosphere invade the inside of the magnetic recording medium 10 and corrode the various layers constituting the magnetic recording medium 10. In particular, as substances that are easily diffused in the surface portion of the magnetic recording medium 10, there are oxides of Co and Fe, and it is important to focus on suppressing their diffusion.

[0047] Therefore, it is studied to set a diffusion prevention layer 16 of a specific composition between the perpendicular magnetic layer 15 and the protective layer 17. The diffusion prevention layer 16 is basically a layer that does not participate in information recording, so if it is set between the perpendicular magnetic layer 15 and the magnetic head, it is far away from the distance between the two and becomes an obstacle to information reading and writing. Therefore, even if the diffusion prevention layer 16 is a thin film, it prevents the diffusion of the above-mentioned oxide, and it is necessary to obtain high adhesion and lattice integration between the uppermost layer 151 of the perpendicular magnetic layer 15 and the protective layer 17.

[0048] The inventors of the present application studied materials that meet these requirements and found that one or more selected from the group consisting of Si, Ti, Cr, B and Ru, or their carbides or oxides can be used as the diffusion prevention layer 16. Specifically, as monomers, Si, Ti, Cr, B, Ru, etc. can be cited, and as their carbides, SiC, TiC, Cr, etc. can be cited.23 C6, Cr7C3, B4C, RuC, etc., and their oxides include TiO2, Cr2O3, B2O3, RuO2, RuO4, etc.

[0049] The content of Si, Ti, Cr, B, and Ru contained in the diffusion prevention layer 16 is preferably 0.5 at % to 10 at %, more preferably 2 at % to 4 at %, from the viewpoint of suppressing the diffusion of oxides.

[0050] The thickness of the diffusion prevention layer 16 is preferably 0.02 nm to 0.4 nm, and more preferably 0.4 nm to 2 nm, from the viewpoint of preventing the diffusion of oxides and making the thickness as thin as possible.

[0051] The diffusion prevention layer 16 preferably further contains cobalt oxide or iron oxide. As described above, the substances that easily diffuse in the surface layer of the magnetic recording medium 10 include Co oxide and Fe oxide. However, the diffusion prevention layer 16 containing these substances can enhance the effect of preventing the diffusion of oxides.

[0052] Specific examples of cobalt oxide and iron oxide include CoO, Fe2O3, and FeO.

[0053] The content of cobalt oxide and iron oxide is preferably 0.1 mol% to 4 mol%.

[0054] The diffusion prevention layer 16 preferably further contains C. If the diffusion prevention layer 16 contains C, the adhesion and lattice conformity between the uppermost layer 151 of the perpendicular magnetic layer 15 and the protective layer 17 can be improved. In addition, C includes a film-forming gas when forming the diffusion prevention layer 16, a precipitate from a target, a diffused product from the protective layer 17, and the like.

[0055] The C content is preferably 20 at % or more.

[0056] The diffusion prevention layer 16 can be formed by a known method such as sputtering. The diffusion prevention layer 16 can be thinned by improving its crystallinity and improving the adhesion and lattice conformity of the layer in contact with the diffusion prevention layer 16. Therefore, reactive sputtering, ion implantation, ion etching, etc. can be used.

[0057] When using reactive sputtering to form the diffusion prevention layer 16 containing Si, targets such as Si, SiC, SiO2, Si-Co, SiO2-Co, SiO2-CoO, and SiC-CoO are used, oxygen is added to the sputtering gas, and RF sputtering, DC magnetron sputtering, etc. are used as the film formation method, thereby forming the diffusion prevention layer 16 containing Si.

[0058] When the diffusion prevention layer 16 containing Si is formed by ion implantation, Si is ion implanted into the film-forming surface of the perpendicular magnetic layer 15. As a Si source, a gas containing an organic silicon compound is preferably used. The organic silicon compound contains C in addition to Si, so C can be efficiently contained in the diffusion prevention layer 16. In addition, the organic silicon compound contains H, so the plasma in the film-forming space can be activated. Therefore, the diffusion prevention layer 16 can have high crystallinity.

[0059] When ion implantation is used, the diffusion prevention layer 16 containing Si can be formed by implanting oxygen ions or carbon ions into the Si film, Si—Co film, etc. after forming the Si film, Si—Co film, etc. on the surface of the perpendicular magnetic layer 15 .

[0060] When the diffusion prevention layer 16 including Si is formed using ion etching, the diffusion prevention layer 16 including Si can be formed by forming a Si film, a Si—Co film, etc. on the surface of the perpendicular magnetic layer 15 and then etching the film surface using oxygen ions or carbon ions.

[0061] It is also effective to etch the surface of the perpendicular magnetic layer 15 with a gas containing an organic silicon compound. Since the organic silicon compound contains C, C can be efficiently contained in the diffusion prevention layer 16 .

[0062] When the diffusion prevention layer 16 contains Ti, Cr, B, Ru, or the like, the same manufacturing method as that of the case where the diffusion prevention layer 16 contains Si can be used.

[0063] The protective layer 17 has a function of protecting the magnetic recording medium 10 from damage caused by contact between the magnetic head and the magnetic recording medium 10 .

[0064] The protective layer 17 can contain carbon.

[0065] As a film-forming method of the protective layer 17 , for example, a sputtering method, a plasma CVD method, an ion beam method, or the like can be used.

[0066] The thickness of the protective layer 17 is preferably 1 nm to 10 nm, and more preferably 2 nm to 6 nm.

[0067] The magnetic recording medium 10 involved in this embodiment has a base layer 14, a perpendicular magnetic layer 15, a diffusion prevention layer 16 and a protective layer 17 on a non-magnetic substrate 11 in sequence, so that the perpendicular magnetic layer 15 has a multilayer structure, the uppermost layer 151 of the perpendicular magnetic layer 15 contains Co or Fe in the magnetic particles, and the layer 152 other than the uppermost layer of the perpendicular magnetic layer 15 contains oxides. In addition, the diffusion prevention layer 16 is arranged between the perpendicular magnetic layer 15 and the protective layer 17, and contains one or more components selected from the group consisting of Si, Ti, Cr, B and Ru, or at least one of their carbides and oxides. Thus, by preventing the oxide contained in the perpendicular magnetic layer 15 from diffusing to the surface of the magnetic recording medium 10, the corrosion path of the magnetic recording medium 10 can be reduced. Thus, the magnetic recording medium 10 can have high corrosion resistance.

[0068] The magnetic recording medium 10 can make the content of Si, Ti, Cr, B and Ru contained in the diffusion prevention layer 16 0.5 at% to 10 at%. This can inhibit the diffusion of Co oxide and Fe oxide to the surface layer of the magnetic recording medium 10, thereby more reliably inhibiting the progress of corrosion of each layer constituting the magnetic recording medium 10. As a result, the magnetic recording medium 10 can further improve the corrosion resistance.

[0069] The magnetic recording medium 10 can make the thickness of the diffusion prevention layer 16 0.02nm to 0.4nm. As a result, it is possible to suppress the diffusion of Co oxide and Fe oxide to the surface layer of the magnetic recording medium 10, so that the corrosion of each layer constituting the magnetic recording medium 10 can be more reliably suppressed, and the increase in the thickness of the diffusion prevention layer 16 can be suppressed. As a result, the magnetic recording medium 10 can further improve the corrosion resistance and can be thinned.

[0070] The magnetic recording medium 10 can include cobalt oxide or iron oxide in the diffusion prevention layer 16. Cobalt oxide or iron oxide is a substance that is particularly easy to diffuse to the surface layer of the magnetic recording medium 10 even among oxides, and the diffusion prevention effect of the oxide can be improved by including these oxides in the diffusion prevention layer 16. As a result, the magnetic recording medium 10 can more reliably improve corrosion resistance.

[0071] The magnetic recording medium 10 can include C in the diffusion prevention layer 16 . The diffusion prevention layer 16 includes C to improve the adhesion and lattice conformity between the uppermost layer 151 of the perpendicular magnetic layer 15 and the protective layer 17 . Therefore, the magnetic recording medium 10 can improve the adhesion between the perpendicular magnetic layer 15 and the protective layer 17 .

[0072] <Magnetic recording and reproducing device>

[0073] A magnetic recording and reproducing device using the magnetic recording medium according to the present embodiment will be described. Figure 3FIG. 2 is a perspective view showing an example of a magnetic recording and reproducing device according to the present embodiment. Figure 3 As shown, the magnetic recording and reproducing device 30 can include: a magnetic recording medium 31, a magnetic recording medium driving unit 32 for rotating the magnetic recording medium 31, a magnetic head 33 having a near-field light generating element at the front end, a magnetic head driving unit 34 for moving the magnetic head 33, and a recording and reproducing signal processing unit 35. The magnetic recording medium 31 uses the magnetic recording media 10 and 20 involved in the above-mentioned present embodiment.

[0074] The magnetic recording and reproducing device 30 mounts the center of a magnetic recording medium 31 on the rotating shaft of a spindle motor, and writes or reads information from the magnetic recording medium 31 while a magnetic head 33 floats above the surface of the magnetic recording medium 31 which is rotationally driven by the spindle motor.

[0075] The magnetic recording and reproducing device 30 according to the present embodiment can suppress corrosion of the magnetic recording medium 10 or 20 by using the magnetic recording medium 10 or 20 according to the present embodiment, and thus can have high durability.

[0076] <Second embodiment>

[0077] A magnetic recording medium according to a second embodiment of the present invention is described. The magnetic recording medium according to this embodiment is stacked on a non-magnetic substrate in sequence from the non-magnetic substrate side and includes a seed layer, a base layer, a perpendicular magnetic layer, a diffusion prevention layer, and a protective layer, wherein the base layer is composed of a plurality of layers, and the perpendicular magnetic layer includes at least one of a FePt-based alloy and a CoPt-based alloy.

[0078] Figure 2 1 is a schematic cross-sectional view showing an example of the structure of the magnetic recording medium involved in this embodiment. Figure 2 As shown in FIG. 1 , the magnetic recording medium 20 includes a non-magnetic substrate 21, a seed layer 22, a base layer 23, a perpendicular magnetic layer 24, a diffusion prevention layer 25, and a protective layer 26, which are stacked in sequence from the non-magnetic substrate 21 side. The base layer 23 includes a first base layer 23-1 and a second base layer 23-2, which are stacked in sequence from the non-magnetic substrate 1 side. The non-magnetic substrate 21, the diffusion prevention layer 25, and the protective layer 26 are similar to the above-mentioned base layer 23. Figure 1 The nonmagnetic substrate 11 , the diffusion prevention layer 16 , and the protective layer 17 included in the magnetic recording medium 10 according to the first embodiment shown are the same, and therefore their descriptions are omitted.

[0079] The seed layer 22, the first underlayer 23-1, and the second underlayer 23-2 are preferably lattice-aligned with the perpendicular magnetic layer 24. This further improves the (001) orientation of the perpendicular magnetic layer 24.

[0080] As the seed layer 22, the first base layer 23-1 and the second base layer 23-2, for example, (100)-oriented Cr, W, MgO, etc. can be used. By forming the seed layer 22, the first base layer 23-1 and the second base layer 23-2 from (100)-oriented Cr, W, MgO, etc., these layers are made into a multilayer structure, so that the lattice mismatch between the seed layer 22, the first base layer 23-1 and the second base layer 23-2 can be less than 10%.

[0081] In order to ensure that the first base layer 23-1 and the second base layer 23-2 are (100) oriented, a Cr layer with a bcc structure or a Cr alloy layer with Cr as the main component, or an alloy layer with a B2 structure can be further formed under the seed layer 22, the first base layer 23-1 or the second base layer 23-2.

[0082] Examples of the Cr alloy forming the Cr alloy layer include Cr—Mn alloy, Cr—Mo alloy, Cr—W alloy, Cr—V alloy, Cr—Ti alloy, and Cr—Ru alloy.

[0083] Examples of the alloy having a B2 structure include a Ru—Al alloy and a Ni—Al alloy.

[0084] In addition, at least one of the seed layer 22 , the first base layer 23 - 1 , and the second base layer 23 - 2 may include an oxide, so that at least one of the seed layer 22 , the first base layer 23 - 1 , and the second base layer 23 - 2 can improve lattice conformity with the perpendicular magnetic layer 24 .

[0085] Examples of the oxide include oxides of one or more metals selected from the group consisting of Ni, Cr, Mo, Nb, Ta, V, and W. Among these, preferred metal oxides include NiO, CrO, Cr2O3, CrO3, MoO2, MoO3, Nb2O5, Ta2O5, V2O3, VO2, WO2, WO3, and WO6.

[0086] The content of oxide in at least one of the seed layer 22, the first base layer 23-1, and the second base layer 23-2 is preferably in the range of 2 mol% to 30 mol%, and more preferably in the range of 10 mol% to 25 mol%. If the content of oxide in at least one of the seed layer 22, the first base layer 23-1, and the second base layer 23-2 is within the above preferred range, the (001) orientation of the perpendicular magnetic layer 24 can be further improved, and the (100) orientation of at least one of the seed layer 22, the first base layer 23-1, and the second base layer 23-2 can be further improved.

[0087] As a material forming the first base layer 23-1, for example, a CoTi alloy containing 50 at% Ti and the remainder Co can be used. The thickness of the first base layer 23-1 is preferably 30 nm to 100 nm, and more preferably about 50 nm, for example.

[0088] As a material forming the second underlayer 23-2, for example, NiO can be used. The thickness of the second underlayer 23-2 is, for example, preferably 3 nm to 10 nm, and more preferably about 5 nm.

[0089] As a method for forming the seed layer 22 , the first base layer 23 - 1 , and the second base layer 23 - 2 , a known method such as a sputtering method can be used.

[0090] The perpendicular magnetic layer 24 is provided on the second base layer 23 - 2 and includes a FePt-based alloy or a CoPt-based alloy.

[0091] The perpendicular magnetic layer 24 includes an alloy having an L10 type crystal structure, and preferably has a (001) orientation.

[0092] The alloy having the L10 type structure preferably has a high magnetic anisotropy constant Ku, and in order to promote regularization of the alloy, it is preferably subjected to a heat treatment during film formation.

[0093] The vertical magnetic layer 24 has a function of recording information and is composed of a multilayer structure. When the vertical magnetic layer 24 includes a FePt-based alloy or a CoPt-based alloy, the top layer 241 of the vertical magnetic layer 24 includes Co or Fe in magnetic particles, and the layers 242 other than the top layer include oxides. When the layers 242 other than the top layer include a plurality of layers, at least one layer of the layers 242 other than the top layer only needs to include oxides.

[0094] The Co or Fe contained in the magnetic grains of the uppermost layer 151 may be Co or Fe of FePt alloy or CoPt alloy, or may be Co or Fe of other alloys. For example, a Co magnetic layer, a Fe magnetic layer, a CoCr magnetic layer, or a CoCrPt magnetic layer may be provided on a magnetic layer having an L10 structure and containing a FePt alloy or a CoPt alloy. These magnetic layers may form an hcp structure or a bcc structure.

[0095] The layer 152 other than the uppermost layer included in the perpendicular magnetic layer 24 is preferably a structure including magnetic particles of FePt alloy or CoPt alloy having an L10 type structure and one or more oxides selected from the group consisting of SiO2, TiO2, Cr2O3, Al2O3, Ta2O5, ZrO2, Y2O3, CeO2, GeO2, MnO, TiO, ZnO, and B2O3. Thus, the exchange bonding between the crystal particles is more reliably cut off, and the signal-to-noise ratio (SNR) of the magnetic recording medium 20 can be further improved.

[0096] Specifically, the vertical magnetic layer 24 can use, for example, a (Fe-45at%Pt)-8mol%SiO2-4mol%Cr2O3 alloy (an alloy containing 8mol%SiO2, 4mol%Cr2O3 and the remainder (45at%Pt and Fe)).

[0097] The average particle size of the magnetic grains included in the perpendicular magnetic layer 24 is preferably 10 nm or less from the viewpoint of increasing the recording density. Generally, if the average particle size of the magnetic grains is small, the magnetic layer 44 is easily affected by thermal fluctuations immediately after magnetic information is written.

[0098] In addition, the average particle size of the magnetic particles can be determined using TEM observation images. For example, the particle sizes (equivalent circle diameters) of 200 magnetic particles can be measured from the TEM observation images, and the particle size at the cumulative value of 50% can be taken as the average particle size. Here, the average grain boundary width of the magnetic particles is preferably 0.3nm to 2.0nm.

[0099] The thickness of the vertical magnetic layer 24 is preferably 1 nm to 20 nm, and more preferably 3 nm to 15 nm. If the thickness of the vertical magnetic layer 24 is within the above preferred range, the regeneration output can be improved and the hypertrophy of the crystal particles can be suppressed. In addition, when the vertical magnetic layer 24 has a multilayer structure, the thickness of the vertical magnetic layer 24 refers to the total thickness of all layers.

[0100] The seed layer 22 , the first underlayer 23 - 1 , the second underlayer 23 - 2 , and the perpendicular magnetic layer 24 can all be formed by using a known method such as sputtering.

[0101] The magnetic recording medium 20 according to the present embodiment includes a base layer 23, a perpendicular magnetic layer 24, a diffusion prevention layer 25, and a protective layer 26 on a non-magnetic substrate 21 in this order, and the perpendicular magnetic layer 24 has a multilayer structure, and the uppermost layer 241 of the perpendicular magnetic layer 24 contains Co or Fe in magnetic particles, and the layers 242 other than the uppermost layer of the perpendicular magnetic layer 24 contain oxides. Furthermore, the diffusion prevention layer 25 has the same structure as the diffusion prevention layer 16 of the magnetic recording medium 10 according to the first embodiment, so that the oxide contained in the diffusion prevention layer 25 is prevented from diffusing to the surface of the magnetic recording medium 20, thereby reducing the corrosion path of the magnetic recording medium 20. As a result, the magnetic recording medium 20 can have high corrosion resistance like the magnetic recording medium 10.

[0102] Since the diffusion prevention layer 25 has the same configuration as the diffusion prevention layer 16 of the magnetic recording medium 10 according to the first embodiment, the magnetic recording medium 20 can achieve the following effects similarly to the magnetic recording medium 10 .

[0103] That is, the magnetic recording medium 20 can make the content of Si, Ti, Cr, B and Ru contained in the diffusion prevention layer 25 0.5at% to 10at%. As a result, it is possible to suppress the diffusion of Co oxide and Fe oxide to the surface layer of the magnetic recording medium 20, so that the corrosion of each layer constituting the magnetic recording medium 20 can be more reliably suppressed. As a result, the magnetic recording medium 20 can further improve the corrosion resistance.

[0104] The magnetic recording medium 20 can make the thickness of the diffusion prevention layer 25 0.02nm to 0.4nm. As a result, it is possible to suppress the diffusion of Co oxide and Fe oxide to the surface layer of the magnetic recording medium 20, so that the corrosion of each layer constituting the magnetic recording medium 20 can be more reliably suppressed, and the increase in the thickness of the diffusion prevention layer 25 can be suppressed. As a result, the magnetic recording medium 20 can further improve the corrosion resistance and can be thinned.

[0105] The magnetic recording medium 20 can contain cobalt oxide or iron oxide in the diffusion prevention layer 25. Cobalt oxide or iron oxide is a substance that is particularly easy to diffuse to the surface layer of the magnetic recording medium 20 even among oxides, and the diffusion prevention effect of the oxide can be improved by including these oxides in the diffusion prevention layer 25. As a result, the magnetic recording medium 20 can more reliably improve corrosion resistance.

[0106] The magnetic recording medium 20 can include C in the diffusion prevention layer 25 . The diffusion prevention layer 25 includes C to improve the adhesion and lattice conformity between the uppermost layer 241 of the perpendicular magnetic layer 24 and the protective layer 26 . Thus, the magnetic recording medium 20 can improve the adhesion between the perpendicular magnetic layer 24 and the protective layer 26 .

[0107] Example

[0108] Hereinafter, although an Example and a comparative example are shown and an embodiment is specifically described, an embodiment is not limited to these Examples and comparative examples.

[0109] <Example 1>

[0110] [Manufacturing of magnetic recording media]

[0111] A magnetic recording medium was produced by the following method.

[0112] A cleaned non-magnetic glass substrate with an outer diameter of 2.5 inches (manufactured by HOYA) was placed in a film forming chamber of a DC magnetron sputtering apparatus (C-3040, manufactured by ANELVA), and the film forming chamber was evacuated to a vacuum degree of 1×10 -5 Pa.

[0113] Next, a 10 nm thick adhesion layer was formed on the nonmagnetic substrate using a Cr-50 at % Ti (Ti content 50 at %, and the remainder Cr) target.

[0114] Next, using a target of Co-20at%Fe-5at%Zr-5at%Ta (Fe content 20at%, Zr content 5at%, Ta content 5at%, and the remainder Co), the temperature of the non-magnetic substrate is set below 100°C, and a soft magnetic layer with a thickness of 25nm is formed on the bonding layer.

[0115] Next, using a Ru target, a Ru layer having a thickness of 0.7 nm was formed as a non-magnetic layer on the soft magnetic layer.

[0116] Next, using a target of Co-20at%Fe-5at%Zr-5at%Ta, a soft magnetic layer having a thickness of 25 nm was formed on the Ru layer as a soft magnetic underlayer while keeping the temperature of the nonmagnetic substrate at 100°C or lower.

[0117] Next, using a Ni-6at% W (W content 6at%, the remainder Ni) target and a Ru target, a 5nm thick Ni-6at% W layer and a 20nm thick Ru layer were formed on the soft magnetic base layer respectively as orientation control base layers.

[0118] Next, a 9nm thick vertical magnetic layer having a granular structure was formed on the orientation control base layer using a target of 91mol% (Co-15at%Cr-18at%Pt)-6mol%SiO2-3mol%TiO2 (Cr content 15at%, Pt content 18at%, the remaining Co alloy content 91mol%, SiO2 content 6mol%, TiO2 content 3mol%). At this time, the sputtering pressure was set to 2Pa.

[0119] Next, using a target of 88mol% (Co-30at% Cr)-12mol% TiO2 (Cr content 30at%, the remaining Co alloy content 8mol%, TiO2 content 12mol%), a non-magnetic layer with a granular structure with a thickness of 0.3nm is formed on the vertical magnetic layer.

[0120] Next, a 6 nm thick vertical magnetic layer having a granular structure was formed on the non-magnetic layer using a target of 92 mol% (Co-11 at% Cr-18 at% Pt)-5 mol% SiO2-3 mol% TiO2 (Cr content 11 at%, Pt content 18 at%, the remaining Co alloy content 92 mol%, SiO2 content 5 mol%, TiO2 content 3 mol%). At this time, the sputtering pressure was set to 2 Pa.

[0121] Next, a Co-11at%Cr-18at%Pt target (Cr content 11at%, Pt content 18at%, the remainder being Co alloy) was used to form a 10nm thick perpendicular magnetic layer. At this time, the sputtering pressure was set to 0.6 Pa. In addition, the substrate temperature during the formation of the perpendicular magnetic layer was 310°C.

[0122] Next, ion implantation was performed on the surface of the perpendicular magnetic layer produced using a Co-11at%Cr-18at%Pt target to form a diffusion prevention layer. In the reaction gas, tetramethylsilane (C4H 12 Si) and argon mixed gas (C4H 12 The ionization was performed by using RF plasma (Si:Ar=1:10).

[0123] Next, a protective layer was formed by an ion beam method, and the total thickness of the diffusion prevention layer and the protective layer was 2.6 nm.

[0124] After forming the protective layer, the diffusion prevention layer was studied by XPS, and the result was that a 3 mol% C-SiO2-3 mol% CoO (SiO2 is 3 mol%, CoO is 3 mol%, and the remainder is C) layer with a thickness of 0.1 nm was formed. In addition, it is believed that the CoO contained in the diffusion prevention layer is a diffused product from the perpendicular magnetic layer, and C is a precipitate from tetramethylsilane and a diffused product from the protective layer.

[0125] Next, a lubricating layer made of perfluoropolyether was formed on the protective layer by a dipping method, thereby obtaining a magnetic recording medium.

[0126] Table 1 shows the type and film formation temperature of the perpendicular magnetic layer, the composition, thickness, and formation method of the diffusion prevention layer, the type of target and the gas used for formation, and the total thickness of the diffusion prevention layer and the protective layer constituting the magnetic recording medium.

[0127] [performance]

[0128] (Corrosion resistance)

[0129] After the magnetic recording medium was placed in an environment of 90°C and 90% RH for 96 hours, the corrosion spots [pieces / face] generated on the surface of the magnetic recording medium were counted using an optical surface inspection machine to evaluate the corrosion resistance. At this time, the detection accuracy was set to a diameter of 5 μm or more. The measurement results of the corrosion spots are shown in Table 1.

[0130] <Examples 2 to 10>

[0131] In Example 1, the same procedure as in Example 1 was carried out except that the diffusion prevention layer was produced under the conditions shown in Table 1.

[0132] <Example 11>

[0133] In Example 1, the same procedure as in Example 1 was carried out except that [Fabrication of Magnetic Recording Medium] was changed to the following method.

[0134] [Manufacturing of magnetic recording media]

[0135] On a heat-resistant glass substrate, a 50 nm thick base layer formed of 50 at% Cr-50 at% Ti (50 at% Cr-50 at% Ti alloy) and a 25 nm thick soft magnetic base layer formed of 75 at% Co-20 at% Ta-5 at% B alloy were sequentially formed. Next, after the substrate was heated to 250°C, a 10 nm thick Cr base layer was formed. The film formation was performed using a DC magnetron sputtering method.

[0136] Next, a MgO base layer was formed into a film with a thickness of 2 nm by using an RF sputtering method.

[0137] Next, the substrate is heated to 520°C and then a DC magnetron sputtering method is used to form a 5nm thick vertical magnetic layer formed by 82mol% (52at% Fe-48at% Pt)-18mol% SiO2 and a 3nm thick vertical magnetic layer formed by 52at% Fe-48at% Pt.

[0138] Next, ion implantation is performed on the surface of the FePt perpendicular magnetic layer to form a diffusion prevention layer. In the reaction gas, the reaction gas is tetramethylsilane (C4H 12 Si) and argon mixed gas (C4H 12 The method is carried out by ionization using RF plasma (Si:Ar=1:10).

[0139] Next, a protective layer was formed by an ion beam method, and the combined thickness of the diffusion prevention layer and the protective layer was 2.2 nm.

[0140] After the protective layer was formed, the diffusion prevention layer was studied by XPS, and the result showed that a 3SiO2-2Fe2O3-C (SiO2 is 3 mol%, Fe2O3 is 2 mol%, and the remainder is C) layer with a thickness of 0.15 nm was formed. In addition, it is believed that the Fe2O3 contained in the diffusion prevention layer is a diffused product from the perpendicular magnetic layer, and C is a precipitate from tetramethylsilane and a diffused product from the protective layer.

[0141] Next, a lubricating layer made of perfluoropolyether was formed on the protective layer by a dipping method, thereby obtaining a magnetic recording medium.

[0142] <Examples 12 to 19>

[0143] In Example 11, the same procedure as in Example 11 was carried out except that the diffusion prevention layer was produced under the conditions shown in Table 1.

[0144] <Comparative Examples 1 and 2>

[0145] In Example 1, the diffusion prevention layer was not formed in [Fabrication of Magnetic Recording Medium] and the film thickness of the protective layer was changed to 2.4 nm. The formation temperature of the perpendicular magnetic layer was 290°C in Comparative Example 1 and 310°C in Comparative Example 2.

[0146] <Comparative Example 3>

[0147] In Example 11, the same procedure as in Example 11 was carried out except that the diffusion prevention layer was not formed in [Production of Magnetic Recording Medium] and the film thickness of the protective layer was changed to 2.2 nm.

[0148] Table 1 shows the type and film formation temperature of the perpendicular magnetic layer constituting the magnetic recording medium, the composition, thickness, formation method, target type and gas used for the diffusion prevention layer, the combined thickness of the diffusion prevention layer and the protective layer, and the measurement results of corrosion spots of each embodiment and comparative example.

[0149] [Table 1]

[0150]

[0151] From Table 1, the number of corrosion spots in Examples 1 to 19 was 108 or less per surface. On the other hand, the number of corrosion spots in Comparative Examples 1 to 3 was 150 or more per surface.

[0152] The magnetic recording media of Examples 1 to 19 are different from the magnetic recording media of Comparative Examples 1 to 3, and it is confirmed that the number of corrosion spots can be reduced and the corrosion resistance can be improved by providing a diffusion prevention layer containing at least one component selected from the group consisting of Si, Ti, Cr, B and Ru, or at least one of their carbides and oxides between the perpendicular magnetic layer and the protective layer. Therefore, it can be said that the magnetic recording medium involved in this embodiment can be effectively used in a magnetic recording and reproducing device.

[0153] As described above, the embodiments are described, but the above embodiments are provided 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 scope of the subject matter of the invention. These embodiments and their variations are included in the scope and subject matter of the invention, and are included in the invention described in the claims and their equivalents.

[0154] Explanation of symbols

[0155] 10, 20, 31 Magnetic recording media

[0156] 11, 21 Non-magnetic substrate

[0157] 12Soft magnetic layer

[0158] 13, 22 seed layer

[0159] 14 Basal layer

[0160] 15, 24 vertical magnetic layer

[0161] 151, 241 top floor

[0162] 152, 242 Layers other than the top layer

[0163] 16, 25 diffusion prevention layer

[0164] 17, 26 protection layer

[0165] 23-1 The first basal layer

[0166] 23-2 Second basal layer

[0167] 30 Magnetic recording and reproducing device

[0168] 32. Magnetic recording medium drive unit

[0169] 33 Magnetic Head

[0170] 34 Head drive unit

[0171] 35 Recording and reproduction signal processing unit.

Claims

1. A magnetic recording medium comprising, on a non-magnetic substrate, an underlayer, a perpendicular magnetic layer, a diffusion prevention layer and a protective layer in this order, The vertical magnetic layer is a multi-layer structure. The uppermost layer of the perpendicular magnetic layer contains Co or Fe in magnetic grains, At least one of the layers other than the uppermost layer of the perpendicular magnetic layer contains an oxide, The diffusion prevention layer is provided between the perpendicular magnetic layer and the protective layer, and includes one or more components selected from the group consisting of Si, Ti, and B, or at least one of carbides and oxides thereof. The average particle diameter of the magnetic grains included in the perpendicular magnetic layer is 10 nm or less. 2 . The magnetic recording medium according to claim 1 , wherein the diffusion prevention layer contains Si, Ti and B in an amount of 0.5 at % to 10 at %. 3 . The magnetic recording medium according to claim 1 , wherein the diffusion prevention layer has a thickness of 0.02 nm to 0.4 nm. 4 . The magnetic recording medium according to claim 1 , wherein the diffusion prevention layer comprises cobalt oxide or iron oxide. 5 . 5 . The magnetic recording medium according to claim 1 , wherein the diffusion prevention layer contains C. 6 . The magnetic recording medium according to claim 1 , wherein the protective layer contains carbon. 7 . The magnetic recording medium according to claim 1 , wherein the protective layer has a thickness of 1 nm to 10 nm.

8. The magnetic recording medium according to any one of claims 1 to 7, wherein the perpendicular magnetic layer comprises 10 The alloy has a (001) orientation. 9 . The magnetic recording medium according to claim 1 , wherein an average particle diameter of magnetic grains included in the perpendicular magnetic layer is 10 nm or less. 10 . The magnetic recording medium according to claim 1 , wherein the perpendicular magnetic layer has a thickness of 1 nm to 20 nm. 11 . A magnetic recording and reproducing device comprising the magnetic recording medium according to claim 1 .

12. A method for producing a magnetic recording medium, which is the method for producing a magnetic recording medium according to any one of claims 1 to 10, The diffusion prevention layer is formed using reactive sputtering, ion implantation, or ion etching.

13. The method for manufacturing a magnetic recording medium according to claim 12, In the case of ion implantation, The diffusion prevention layer is formed using a gas containing an organic silicon compound as a Si source.

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