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

Abstract

To provide a magnetic recording medium with high corrosion resistance.SOLUTION: A magnetic recording medium according to the present invention includes a ground layer, a perpendicular magnetic layer, a diffusion prevention layer, and a protective layer in this order on a non-magnetic substrate. The perpendicular magnetic layer has a multilayer structure, the top layer of the perpendicular magnetic layer contains Co or Fe in magnetic grains, at least one of the layers other than the top layer of the perpendicular magnetic layer contains an oxide; and the diffusion prevention layer is provided between the perpendicular magnetic layer and the protective layer and contains one or more components selected from a group consisting of Si, Ti, Cr, B, or Ru, or at least one of carbides and oxides.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Magnetic recording media are widely used as recording media for recording and storing various types of data. Magnetic recording media are generally constructed by laminating an underlayer, a perpendicular magnetic layer, and a protective layer in this order on a non-magnetic substrate.

[0003] In order to improve the recording density of magnetic recording media, the crystal orientation of the perpendicular magnetic layer is important. Therefore, magnetic recording media have been developed that use a magnetic layer having a so-called granular structure in which columnar magnetic grains are covered with an oxide or the like.

[0004] As an example of a magnetic recording medium using a magnetic layer having such a granular structure, a magnetic recording medium has been disclosed in which, on a non-magnetic substrate, at least an orientation control layer that controls the orientation of the layer directly above, and a perpendicular magnetic layer whose axis of easy magnetization is oriented mainly perpendicular to the non-magnetic substrate are provided, the perpendicular magnetic layer being composed of two or more magnetic layers, at least one of which is a layer containing an oxide whose main component is Co and contains Pt, and at least one of which is a layer whose main component is Co and contains Cr and does not contain an oxide (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2004-310910 A Summary of the Invention [Problem to be solved by the invention]

[0006] As the range of application of magnetic recording and reproducing devices becomes wider, there is a demand for further improvement in the recording density of magnetic recording media. One method for increasing the recording density of magnetic recording media is to increase the film formation temperature of the perpendicular magnetic layer and thereby improve the crystal orientation of the perpendicular magnetic layer.

[0007] However, when 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, causing problems such as fluctuations in the composition of the perpendicular magnetic layer and deterioration of the magnetic properties, etc. In particular, when oxides contained in the perpendicular magnetic layer are thermally diffused to the surface of the magnetic recording medium due to heating during production, impurities in the air penetrate into the magnetic recording medium through this diffusion path, causing corrosion of the magnetic recording medium.

[0008] An object of one aspect of the present invention is to provide a magnetic recording medium having high corrosion resistance. [Means for solving the problem]

[0009] A magnetic recording medium according to one embodiment of the present invention comprises an underlayer, a perpendicular magnetic layer, a diffusion prevention layer and a protective layer, in that order, on a non-magnetic substrate, the perpendicular magnetic layer having a multi-layer 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 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 their carbides and oxides. Effect of the Invention

[0010] According to one aspect of the present invention, a magnetic recording medium having high corrosion resistance can be provided. [Brief description of the drawings]

[0011] [Figure 1] 1 is a schematic cross-sectional view showing an example of the structure of a magnetic recording medium according to an embodiment of the present invention. [Diagram 2] 1 is a schematic cross-sectional view showing an example of the structure of a magnetic recording medium according to an embodiment of the present invention. [Diagram 3] 1 is a schematic diagram showing an example of a magnetic recording and reproducing device according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention will be described in detail. In order to facilitate understanding of the description, the same components in each drawing are given the same reference numerals, and duplicated description will be omitted. Also, the scale of each member in the drawings may differ from the actual scale. In this specification, a tilde "~" indicating a numerical range means that the numerical values ​​before and after it are included as the lower and upper limits, unless otherwise specified.

[0013] <First embodiment> [Magnetic recording media] The magnetic recording medium according to the first embodiment of the present invention will be described. The magnetic recording medium according to this embodiment includes a soft magnetic layer, a seed layer, an underlayer, a perpendicular magnetic layer, a diffusion prevention layer, and a protective layer, which are laminated in this order from the non-magnetic substrate side, and the perpendicular magnetic layer contains a CoCr-based alloy.

[0014] Fig. 1 is a schematic cross-sectional view showing an example of the configuration of a magnetic recording medium according to this embodiment. As shown in Fig. 1, a magnetic recording medium 10 includes a non-magnetic 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, which are laminated in this order from the non-magnetic substrate 11 side.

[0015] Examples of materials constituting the non-magnetic substrate 11 include Al alloys such as AlMg alloys, soda glass, aluminosilicate glass, amorphous glasses, silicon, titanium, ceramics, sapphire, quartz, resins, etc. Among these, Al alloys and glasses such as crystallized glass and amorphous glass are preferable.

[0016] The soft magnetic layer 12 is provided on the non-magnetic substrate 11 and has the 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 a signal on the magnetic recording medium 10 .

[0017] Examples of materials constituting the soft magnetic layer 12 include soft magnetic alloys such as FeCo based alloys, CoZrNb based alloys, and CoTaZr based alloys.

[0018] The soft magnetic layer 12 preferably has an amorphous structure, which can improve the surface smoothness of the soft magnetic layer 12, thereby reducing the flying height of the magnetic head and further improving the recording density of the magnetic recording medium 10.

[0019] The soft magnetic layer 12 may be formed in multiple layers with a non-magnetic layer such as a Ru film interposed therebetween to form an antiferromagnetic exchange coupling (AFC) film.

[0020] The total thickness of the soft magnetic layer 12 is appropriately determined based on 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.

[0021] The seed layer 13 is provided on the soft magnetic layer 12 and has the function of improving the (002) plane orientation of the underlayer 14.

[0022] The material constituting the seed layer 13 is preferably a material having an hcp structure, an fcc structure, or an amorphous structure, and examples thereof include Ru-based alloys, Ni-based alloys, Co-based alloys, Pt-based alloys, and Cu-based alloys.

[0023] The thickness of the seed layer 13 is preferably within a range of 0.5 nm to 20 nm, and more preferably within a range of 3 nm to 10 nm. By setting the thickness of the seed layer 13 within the above preferred range, the underlayer 14 can be stably oriented in the (002) plane.

[0024] The underlayer 14 is provided on the seed layer 13, and has the function of improving the (002) plane orientation of the perpendicular magnetic layer 15.

[0025] The material constituting the underlayer 14 may be Ru or an alloy thereof having a hcp structure.

[0026] The average crystal grain size of the underlayer 14 is preferably within a range of 6 nm to 20 nm, and more preferably within a range of 6 nm to 8 nm.

[0027] The thickness of the underlayer 14 can be appropriately designed, and is preferably, for example, 5 nm to 30 nm.

[0028] The perpendicular magnetic layer 15 is provided on the underlayer 14, and information is recorded therein. The perpendicular magnetic layer 15 has a multi-layer structure including a top layer 151 and layers 152 other than the top layer, and in this embodiment, the perpendicular magnetic layer 15 contains a CoCr-based alloy, so that the top layer 151 contains Co in its magnetic particles, and the layers 152 other than the top layer contain an oxide. When the layers 152 other than the top layer include a plurality of layers, it is sufficient that at least one of the layers 152 other than the top layer contains an oxide.

[0029] Examples of materials constituting the perpendicular magnetic layer 15 include CoCr, CoCrPt, CoCrPtB, etc., when the perpendicular magnetic layer 15 does not contain an oxide. Examples of materials constituting the perpendicular magnetic layer 15 include CoCrPt-B, etc., when the perpendicular magnetic layer 15 contains an oxide. 2 O 3 , CoCrPt-SiO 2 , CoCrPt-Cr 2 O 3 , CoCrPt-TiO 2 , CoCrPt-ZrO 2 , CoCrPt-Nb 2 O 5 , CoCrPt-Ta 2 O 5 , CoCrPt-TiO 2 etc.

[0030] When the perpendicular magnetic layer 15 contains an oxide, the oxide surrounds the crystal grains of the CoCr-based alloy to form a granular structure, which reduces the magnetic interaction between the crystal grains of the CoCr-based alloy and reduces noise.

[0031] The soft magnetic layer 12, the seed layer 13, the underlayer 14 and the perpendicular magnetic layer 15 can be formed by DC magnetron sputtering or RF sputtering.

[0032] When depositing the soft magnetic layer 12, the seed layer 13, the underlayer 14, and the perpendicular magnetic layer 15, an RF (Radio Frequency) bias, a DC bias, a pulsed DC, a pulsed DC bias, or the like may be used as necessary.

[0033] Reactive gas: O 2 Gas, H 2 O gas, N 2 A gas or the like may also be used.

[0034] The sputtering gas pressure is appropriately adjusted so as to optimize the characteristics of each layer, but is usually within the range of about 0.1 Pa to 30 Pa.

[0035] The diffusion prevention layer 16 is provided between the perpendicular magnetic layer 15 of the multi-layer structure and the protective layer 17, and has the function of preventing oxides contained in the perpendicular magnetic layer 15 from diffusing to the surface of the magnetic recording medium 10. The diffusion prevention layer 16 prevents oxides contained in the perpendicular magnetic layer 15 from diffusing to the surface of the magnetic recording medium 10, thereby eliminating a corrosion path for the magnetic recording medium 10 and improving the corrosion resistance.

[0036] According to the study of the present inventors, heating of the non-magnetic substrate 11 during the manufacture of the magnetic recording medium 10 causes oxides contained in the perpendicular magnetic layer 15 to diffuse into the surface layer through the crystal grain boundaries of the perpendicular magnetic layer 15 and the protective layer 17. The inventors have focused on the fact that impurities in the air penetrate into the magnetic recording medium 10 through the diffusion path at that time and corrode each layer constituting the magnetic recording medium 10. In particular, the inventors have focused on the fact that substances that are likely to diffuse into the surface layer of the magnetic recording medium 10 include oxides of Co and Fe, and that it is important to suppress the diffusion of these oxides.

[0037] Therefore, we have investigated the provision of 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 is not involved in information recording, so if it is provided between the perpendicular magnetic layer 15 and the magnetic head, it will increase the distance between them, which will hinder the reading and writing of information. Therefore, even if the diffusion prevention layer 16 is a thin film, it is necessary to prevent the diffusion of the oxide and to obtain high adhesion and lattice matching between the top layer 151 of the perpendicular magnetic layer 15 and the protective layer 17.

[0038] The present inventors have investigated materials that satisfy these requirements and found that one or more elements selected from the group consisting of Si, Ti, Cr, B, and Ru, or carbides or oxides thereof can be used for the diffusion prevention layer 16. Specifically, the simple elements are Si, Ti, Cr, B, Ru, etc., and the carbides thereof are SiC, TiC, Cr 23 C 6 , Cr 7 C 3 , B 4 C, RuC, etc., and their oxides include TiO 2 , Cr 2 O 3 , B 2 O 3 , RuO 2 , RuO 4 etc.

[0039] The content of Si, Ti, Cr, B, and Ru in the diffusion prevention layer 16 is preferably 0.5 at % to 10 at %, and more preferably 2 at % to 4 at %, in order to suppress the diffusion of oxides.

[0040] From the viewpoint of preventing the diffusion of oxides and making the thickness as thin as possible, 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.

[0041] It is preferable that the diffusion prevention layer 16 further contains cobalt oxide or iron oxide. As described above, oxides of Co and Fe are substances that tend to diffuse into the surface layer of the magnetic recording medium 10, and by containing these substances in the diffusion prevention layer 16, the effect of preventing the diffusion of the oxides can be improved.

[0042] Specific examples of cobalt oxide and iron oxide are CoO, Fe 2 O 3 , FeO, etc.

[0043] The content of cobalt oxide and iron oxide is preferably 0.1 mol % to 4 mol %.

[0044] The diffusion prevention layer 16 preferably further contains C. When the diffusion prevention layer 16 contains C, it is possible to improve the adhesion and lattice matching between the uppermost layer 151 of the perpendicular magnetic layer 15 and the protective layer 17. Examples of C include deposition gases and deposits from the target when forming the diffusion prevention layer 16, and diffused materials from the protective layer 17.

[0045] The C content is preferably 20 at % or more.

[0046] The diffusion prevention layer 16 can be formed by a known method such as a sputtering method. In order to increase the crystallinity of the diffusion prevention layer 16 to make it thinner and to increase the adhesion and lattice matching between the diffusion prevention layer 16 and layers in contact with it, reactive sputtering, ion implantation, ion etching, etc. can be used.

[0047] When the diffusion prevention layer 16 containing Si is formed by reactive sputtering, Si, SiC, SiO 2 , Si-Co, SiO 2 -Co, SiO 2The diffusion prevention layer 16 containing Si can be formed by using a target such as -CoO or SiC-CoO, adding oxygen to the sputtering gas, and using a film formation method such as RF sputtering or DC magnetron sputtering.

[0048] When forming the diffusion prevention layer 16 containing Si by ion implantation, Si is ion-implanted into the deposition surface of the perpendicular magnetic layer 15. As the Si source, it is preferable to use a gas containing an organosilicon compound. Since the organosilicon compound contains C in addition to Si, it is possible to efficiently include C in the diffusion prevention layer 16. Furthermore, since the organosilicon compound contains H, it is possible to activate the plasma in the deposition space. Therefore, the diffusion prevention layer 16 can have high crystallinity.

[0049] In addition, when ion implantation is used, a Si film, a Si-Co film, etc. can be formed on the surface of the perpendicular magnetic layer 15, and then oxygen ions or carbon ions, etc. can be implanted into the Si film, the Si-Co film, etc. to form the diffusion prevention layer 16 containing Si.

[0050] When forming the diffusion prevention layer 16 containing Si by using ion etching, the diffusion prevention layer 16 containing Si can be formed by forming a Si film, a Si-Co film, or the like on the surface of the perpendicular magnetic layer 15, and then etching the film surface using oxygen ions, carbon ions, or the like.

[0051] It is also effective to etch the surface of the perpendicular magnetic layer 15 with a gas containing an organosilicon compound. Since the organosilicon compound contains C, it is possible to efficiently include C in the diffusion prevention layer 16.

[0052] When the diffusion prevention layer 16 contains Ti, Cr, B, Ru, or the like, the same manufacturing method as that for the case where the diffusion prevention layer 16 contains Si can be used.

[0053] The protective layer 17 has the function of protecting the magnetic recording medium 10 from damage caused by contact between the magnetic head and the magnetic recording medium 10 .

[0054] The protective layer 17 may include carbon.

[0055] The protective layer 17 can be formed by, for example, sputtering, plasma CVD, ion beam deposition, or the like.

[0056] The thickness of the protective layer 17 is preferably from 1 nm to 10 nm, and more preferably from 2 nm to 6 nm.

[0057] The magnetic recording medium 10 according to the present embodiment includes an underlayer 14, a perpendicular magnetic layer 15, a diffusion prevention layer 16, and a protective layer 17 on a non-magnetic substrate 11 in this order. The perpendicular magnetic layer 15 has a multi-layer structure, and the uppermost layer 151 of the perpendicular magnetic layer 15 contains Co or Fe in the magnetic particles, and the layers 152 other than the uppermost layer of the perpendicular magnetic layer 15 contain oxides. The diffusion prevention layer 16 is provided between the perpendicular magnetic layer 15 and the protective layer 17, and contains at least one component selected from the group consisting of Si, Ti, Cr, B, and Ru, or at least one of carbides and oxides thereof. This prevents the oxides contained in the perpendicular magnetic layer 15 from diffusing to the surface of the magnetic recording medium 10, thereby reducing the corrosion path of the magnetic recording medium 10. Therefore, the magnetic recording medium 10 can have high corrosion resistance.

[0058] The magnetic recording medium 10 can have the Si, Ti, Cr, B, and Ru contents in the diffusion prevention layer 16 be 0.5 at % to 10 at %. This can prevent oxides of Co and Fe from diffusing into the surface layer of the magnetic recording medium 10, so that the progress of corrosion of each layer constituting the magnetic recording medium 10 can be more reliably suppressed. Therefore, the magnetic recording medium 10 can have higher corrosion resistance.

[0059] In the magnetic recording medium 10, the thickness of the diffusion prevention layer 16 can be set to 0.02 nm to 0.4 nm. This makes it possible to suppress the diffusion of oxides of Co and Fe into the surface layer of the magnetic recording medium 10, so that the progress of corrosion of each layer constituting the magnetic recording medium 10 can be more reliably suppressed and an increase in the thickness of the diffusion prevention layer 16 can be suppressed. Therefore, the magnetic recording medium 10 can have higher corrosion resistance and can be made thinner.

[0060] The magnetic recording medium 10 may contain cobalt oxide or iron oxide in the diffusion prevention layer 16. Among oxides, cobalt oxide and iron oxide are substances that are particularly likely to diffuse into the surface layer of the magnetic recording medium 10, and by including these oxides in the diffusion prevention layer 16, the effect of preventing the oxide diffusion can be enhanced. Thus, the magnetic recording medium 10 can more reliably improve its corrosion resistance.

[0061] The magnetic recording medium 10 may include C in the diffusion prevention layer 16. When the diffusion prevention layer 16 includes C, the adhesion and lattice matching between the uppermost layer 151 of the perpendicular magnetic layer 15 and the protective layer 17 can be improved, and therefore the magnetic recording medium 10 can improve the adhesion between the perpendicular magnetic layer 15 and the protective layer 17.

[0062] <Magnetic recording and reproducing device> A magnetic recording and reproducing device using the magnetic recording medium according to this embodiment will be described. Fig. 3 is a perspective view showing an example of the magnetic recording and reproducing device according to this embodiment. As shown in Fig. 3, the magnetic recording and reproducing device 30 can have a magnetic recording medium 31, a magnetic recording medium driving unit 32 for rotating the magnetic recording medium 31, a magnetic head 33 equipped with a near-field light generating element at its tip, 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 is the magnetic recording medium 10 and 20 according to this embodiment described above.

[0063] The magnetic recording and reproducing device 30 attaches the center of a magnetic recording medium 31 to the rotating shaft of a spindle motor, and writes or reads information to the magnetic recording medium 31 while a magnetic head 33 floats and runs above the surface of the magnetic recording medium 31, which is rotated by the spindle motor.

[0064] The magnetic recording and reproducing device 30 according to this embodiment can have high durability by using the magnetic recording medium 10 or 20 according to this embodiment, since corrosion of the magnetic recording medium 10 or 20 can be suppressed.

[0065] <Second embodiment> A magnetic recording medium according to a second embodiment of the present invention will be described. The magnetic recording medium according to this embodiment includes a non-magnetic substrate, a seed layer, an underlayer, a perpendicular magnetic layer, a diffusion prevention layer, and a protective layer, which are laminated in this order from the non-magnetic substrate side, the underlayer being composed of multiple layers, and the perpendicular magnetic layer containing at least one of an FePt-based alloy and a CoPt-based alloy.

[0066] Fig. 2 is a schematic cross-sectional view showing an example of the configuration of the magnetic recording medium according to this embodiment. As shown in Fig. 2, the magnetic recording medium 20 includes a non-magnetic substrate 21, a seed layer 22, an underlayer 23, a perpendicular magnetic layer 24, a diffusion prevention layer 25, and a protective layer 26, which are laminated in this order from the non-magnetic substrate 1 side. The underlayer 23 includes a first underlayer 23-1 and a second underlayer 23-2, which are laminated in this order from the non-magnetic substrate 1 side. The non-magnetic substrate 21, the diffusion prevention layer 25, and the protective layer 26 are the same as the non-magnetic substrate 11, the diffusion prevention layer 16, and the protective layer 17 of the magnetic recording medium 10 according to the first embodiment shown in Fig. 1 described above, and therefore their description will be omitted.

[0067] The seed layer 22, the first underlayer 23-1 and the second underlayer 23-2 are preferably lattice-matched with the perpendicular magnetic layer 24. This further improves the (001) orientation of the perpendicular magnetic layer 24.

[0068] The seed layer 22, the first underlayer 23-1, and the second underlayer 23-2 may be made of, for example, (100) oriented Cr, W, MgO, etc. By forming the seed layer 22, the first underlayer 23-1, and the second underlayer 23-2 from, for example, (100) oriented Cr, W, MgO, etc. and forming these layers into a multilayer structure, the lattice misfit between the seed layer 22, the first underlayer 23-1, and the second underlayer 23-2 can be set to 10% or less.

[0069] In order to ensure that the first underlayer 23-1 and the second underlayer 23-2 have a (100) orientation, a Cr layer having a bcc structure, a Cr alloy layer containing Cr as the main component, or an alloy layer having a B2 structure may be further formed under the seed layer 22, the first underlayer 23-1, or the second underlayer 23-2.

[0070] Examples of the Cr alloy that forms the Cr alloy layer include a Cr-Mn alloy, a Cr-Mo alloy, a Cr-W alloy, a Cr-V alloy, a Cr-Ti alloy, and a Cr-Ru alloy.

[0071] Examples of alloys having the B2 structure include Ru-Al alloys and Ni-Al alloys.

[0072] At least one of the seed layer 22, the first underlayer 23-1, and the second underlayer 23-2 may contain an oxide, which can improve the lattice matching of at least one of the seed layer 22, the first underlayer 23-1, and the second underlayer 23-2 with the perpendicular magnetic layer 24.

[0073] 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, Cr 2 O 3 , CrO 3 , MoO 2 , MoO 3 , Nb 2 O 5 , Ta 2 O 5 , V 2O 3 , V.O. 2 , WO 2 , WO 3 , WO 6 etc.

[0074] The oxide content in at least one of the seed layer 22, the first underlayer 23-1, and the second underlayer 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 oxide content in at least one of the seed layer 22, the first underlayer 23-1, and the second underlayer 23-2 is within the above-mentioned 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 underlayer 23-1, and the second underlayer 23-2 can be further improved.

[0075] The material for forming the first underlayer 23-1 can be, for example, a CoTi alloy containing 50 at % Ti and the remainder Co. The thickness of the first underlayer 23-1 is preferably, for example, 30 nm to 100 nm, and more preferably about 50 nm.

[0076] The material for forming the second underlayer 23-2 may be, for example, NiO. The thickness of the second underlayer 23-2 is preferably, for example, 3 nm to 10 nm, and more preferably about 5 nm.

[0077] The seed layer 22, the first underlayer 23-1 and the second underlayer 23-2 can be formed by a known method such as a sputtering method.

[0078] The perpendicular magnetic layer 24 is provided on the second underlayer 23-2 and contains an FePt-based alloy or a CoPt-based alloy.

[0079] The perpendicular magnetic layer 24 is L1 0 It preferably contains an alloy having a crystalline structure of the type 100 and is (001) oriented.

[0080] L10 The alloy having the type structure preferably has a high magnetic anisotropy constant Ku, and is preferably heat-treated during film formation in order to promote ordering of the alloy.

[0081] The perpendicular magnetic layer 24 has a function of recording information and is configured with a multi-layer structure. When the perpendicular magnetic layer 24 contains an FePt-based alloy or a CoPt-based alloy, the uppermost layer 241 of the perpendicular magnetic layer 24 contains Co or Fe in the magnetic particles, and the layers 242 other than the uppermost layer contain an oxide. When the layers 242 other than the uppermost layer include a plurality of layers, it is sufficient that at least one of the layers 242 other than the uppermost layer contains an oxide.

[0082] The Co or Fe contained in the magnetic particles of the uppermost layer 151 may be Co or Fe in an FePt-based alloy or a CoPt-based alloy, or may be Co or Fe in other alloys. For example, L1 0 A Co magnetic layer, an Fe magnetic layer, a CoCr magnetic layer, or a CoCrPt magnetic layer may be provided on a magnetic layer containing an FePt alloy or a CoPt alloy having the type structure. These magnetic layers may have an hcp structure or a bcc structure.

[0083] The layer 152 other than the top layer included in the perpendicular magnetic layer 24 is L1 0 FePt-based alloy and CoPt-based alloy magnetic particles with a SiO 2 , TiO 2 , Cr 2 O 3 , Al 2 O 3 , Ta 2 O 5 , ZrO 2 , Y 2 O 3 , CEO 2 , GeO 2 , MnO, TiO, ZnO, B 2 O 3 It is preferable that the structure contains one or more oxides selected from the group consisting of: This makes it possible to more reliably break the exchange coupling between crystal grains and further improve the signal-to-noise ratio (SNR) of the magnetic recording medium 20.

[0084] Specifically, the perpendicular magnetic layer 24 is, for example, (Fe-45 at % Pt)-8 mol % SiO 2 -4mol%Cr 2 O 3 Alloys (SiO 2 The content is 8mol%, Cr 2 O 3 An alloy having a Pt content of 4 mol % and the remainder (Pt content of 45 at %, and the remainder Fe) can be used.

[0085] From the viewpoint of increasing the recording density, the average grain size of the magnetic grains contained in the perpendicular magnetic layer 24 is preferably 10 nm or less. In general, as the average grain size of the magnetic grains becomes smaller, the magnetic layer 44 becomes more susceptible to the influence of thermal fluctuation immediately after magnetic information is written thereto.

[0086] The average particle size of the magnetic particles can be determined using a TEM observation image. For example, the particle sizes (equivalent circle diameters) of 200 magnetic particles can be measured from the TEM observation image, and the particle size at an integrated value of 50% can be regarded as the average particle size. Here, the average grain boundary width of the magnetic particles is preferably 0.3 nm to 2.0 nm.

[0087] The thickness of the perpendicular magnetic layer 24 is preferably 1 nm to 20 nm, and more preferably 3 nm to 15 nm. If the thickness of the perpendicular magnetic layer 24 is within the above-mentioned preferred range, the reproduction output can be improved and the enlargement of crystal grains can be suppressed. When the perpendicular magnetic layer 24 has a multi-layer structure, the thickness of the perpendicular magnetic layer 24 means the total thickness of all layers.

[0088] 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 a sputtering method.

[0089] The magnetic recording medium 20 according to this embodiment includes an underlayer 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 multi-layer structure, and the uppermost layer 241 of the perpendicular magnetic layer 24 contains Co or Fe in the magnetic particles, and the layers 242 other than the uppermost layer of the perpendicular magnetic layer 24 contain oxides. The diffusion prevention layer 25 has a similar structure to the diffusion prevention layer 16 of the magnetic recording medium 10 according to the first embodiment, and therefore, by preventing the oxides contained in the diffusion prevention layer 25 from diffusing to the surface of the magnetic recording medium 20, the corrosion path of the magnetic recording medium 20 can be reduced. Thus, the magnetic recording medium 20 can have high corrosion resistance, similar to the magnetic recording medium 10.

[0090] Since the diffusion prevention layer 25 has a similar structure to 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, similar to the magnetic recording medium 10.

[0091] That is, the magnetic recording medium 20 can have the Si, Ti, Cr, B, and Ru contents in the diffusion prevention layer 25 be 0.5 at % to 10 at %. This can prevent oxides of Co and Fe from diffusing into the surface layer of the magnetic recording medium 10, so that the progress of corrosion of each layer constituting the magnetic recording medium 20 can be more reliably suppressed. Therefore, the magnetic recording medium 20 can have higher corrosion resistance.

[0092] In the magnetic recording medium 20, the thickness of the diffusion prevention layer 25 can be set to 0.02 nm to 0.4 nm. This makes it possible to suppress the diffusion of oxides of Co and Fe into the surface layer of the magnetic recording medium 20, so that the progress of corrosion of each layer constituting the magnetic recording medium 20 can be more reliably suppressed and an increase in the thickness of the diffusion prevention layer 25 can be suppressed. Therefore, the magnetic recording medium 20 can have a higher corrosion resistance and can be made thinner.

[0093] The magnetic recording medium 20 may contain cobalt oxide or iron oxide in the diffusion prevention layer 25. Among oxides, cobalt oxide and iron oxide are substances that are particularly likely to diffuse into the surface layer portion of the magnetic recording medium 20, and by including these oxides in the diffusion prevention layer 25, the effect of preventing the oxide diffusion can be enhanced. Therefore, the magnetic recording medium 20 can more reliably improve its corrosion resistance.

[0094] The magnetic recording medium 20 may include C in the diffusion prevention layer 25. When the diffusion prevention layer 25 includes C, the adhesion and lattice matching between the uppermost layer 241 of the perpendicular magnetic layer 24 and the protective layer 26 can be improved, and therefore the magnetic recording medium 20 can improve the adhesion between the perpendicular magnetic layer 24 and the protective layer 26. EXAMPLES

[0095] Hereinafter, the embodiment will be specifically described with reference to examples and comparative examples, but the embodiment is not limited to these examples and comparative examples.

[0096] <Example 1> [Magnetic recording medium production] A magnetic recording medium was prepared by the following method.

[0097] A cleaned non-magnetic glass substrate (HOYA) with an outer diameter of 2.5 inches was placed in the deposition chamber of a DC magnetron sputtering device (C-3040, ANELVA) and the ultimate vacuum was set to 1×10 -5 The deposition chamber was evacuated until the pressure reached 100 Pa.

[0098] Next, a 10 nm thick adhesion layer was formed on the non-magnetic substrate using a target of Cr-50 at % Ti (Ti content 50 at %, balance Cr).

[0099] Next, using a target of Co-20at%Fe-5at%Zr-5at%Ta (Fe content 20at%, Zr content 5at%, Ta content 5at%, remainder Co), the temperature of the non-magnetic substrate was lowered to below 100°C, and a soft magnetic layer 25nm thick was formed on the adhesion layer.

[0100] Next, a Ru layer having a thickness of 0.7 nm was formed as a nonmagnetic layer on the soft magnetic layer using a Ru target.

[0101] Next, using a target of Co-20at%Fe-5at%Zr-5at%Ta, the temperature of the non-magnetic substrate was lowered to 100°C or less, and a soft magnetic layer of 25 nm thickness was formed on the Ru layer as a soft magnetic underlayer.

[0102] Next, using a Ni-6at%W (W content 6at%, remainder Ni) target and a Ru target, a Ni-6at%W layer with a thickness of 5 nm and a Ru layer with a thickness of 20 nm were formed in that order on the soft magnetic underlayer to form an orientation control underlayer.

[0103] Next, 91mol%(Co-15at%Cr-18at%Pt)-6mol%SiO 2 -3mol%TiO 2 (Cr content 15 at%, Pt content 18 at%, balance Co alloy content 91 mol%, SiO 2 Content 6mol%, TiO 2 A perpendicular magnetic layer having a granular structure and a thickness of 9 nm was formed on the orientation control underlayer using a target containing 3 mol % of ZnO. The sputtering pressure was set to 2 Pa.

[0104] Next, 88mol%(Co-30at%Cr)-12mol%TiO 2 (Cr content 30 at%, Co alloy content 8 mol%, TiO 2 A nonmagnetic layer having a granular structure and a thickness of 0.3 nm was formed on the perpendicular magnetic layer using a target having a content of 12 mol %.

[0105] Next, 92mol%(Co-11at%Cr-18at%Pt)-5mol%SiO 2 -3mol%TiO 2 (Cr content 11 at%, Pt content 18 at%, balance Co alloy content 92 mol%, SiO 2Content 5 mol%, TiO 2 A perpendicular magnetic layer having a granular structure and a thickness of 6 nm was formed on the non-magnetic layer using a target containing 3 mol % of Cr. The sputtering pressure was set to 2 Pa.

[0106] Next, a perpendicular magnetic layer having a thickness of 10 nm was formed using a target of Co-11at%Cr-18at%Pt (an alloy with Cr content of 11at%, Pt content of 18at%, and the remainder Co). At this time, the sputtering pressure was set to 0.6 Pa. The substrate temperature during the formation of the perpendicular magnetic layer was 310°C.

[0107] Next, a diffusion prevention layer was formed by ion implantation on the surface of the perpendicular magnetic layer prepared using a Co-11at%Cr-18at%Pt target. The reaction gas for ion implantation was tetramethylsilane (C 4 H 12 Si) and argon gas mixture (C 4 H 12 Si:Ar=1:10) was ionized with RF plasma.

[0108] Next, a protective layer was formed by an ion beam method so that the total thickness of the diffusion prevention layer and the protective layer became 2.6 nm.

[0109] After forming the protective layer, the diffusion prevention layer was examined by XPS and found to be 0.1 nm thick, 3 mol% C-SiO 2 -3mol%CoO(SiO 2 The diffusion prevention layer was formed with 3 mol% of tetramethylsilane, 3 mol% of CoO, and the remainder being C. The CoO contained in the diffusion prevention layer is thought to be a diffused material from the perpendicular magnetic layer, and the C is thought to be a precipitate from tetramethylsilane and a diffused material from the protective layer.

[0110] Next, a lubricating layer made of perfluoropolyether was formed on the protective layer by a dipping method to obtain a magnetic recording medium.

[0111] Table 1 shows the type and deposition temperature of the perpendicular magnetic layer that constitutes the magnetic recording medium, the composition, thickness, formation method, target type, and gas used in formation of the diffusion prevention layer, and the total thickness of the diffusion prevention layer and protective layer.

[0112] [Performance] (corrosion resistant) After leaving the magnetic recording medium for 96 hours in an environment of 90°C and 90% RH, the corrosion resistance was evaluated by counting the number of corrosion spots [pieces / surface] that occurred on the surface of the magnetic recording medium using an optical surface inspection machine. 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.

[0113] <Examples 2 to 10> The same procedure as in Example 1 was carried out, except that the diffusion prevention layer was formed under the conditions shown in Table 1.

[0114] <Example 11> The same procedure as in Example 1 was carried out, except that the [Preparation of magnetic recording medium] in Example 1 was changed to the following method.

[0115] [Magnetic recording medium production] On a heat-resistant glass substrate, a 50 nm thick underlayer made of 50 at% Cr-50 at% Ti (50 at% Cr-50 at% Ti alloy) and a 25 nm thick soft magnetic underlayer made of 75 at% Co-20 at% Ta-5 at% B alloy were deposited in that order. Next, the substrate was heated to 250°C, and a 10 nm thick Cr underlayer was deposited. The deposition was performed using a DC magnetron sputtering method.

[0116] Next, a 2 nm thick MgO underlayer was formed by RF sputtering.

[0117] Next, the substrate was heated to 520°C, and then a 5-nm-thick 82 mol% (52 at% Fe-48 at% Pt)-18 mol% SiO was deposited on the substrate by DC magnetron sputtering. 2 A perpendicular magnetic layer made of 52 at % Fe-48 at % Pt and a perpendicular magnetic layer made of 52 at % Fe-48 at % Pt were formed to a thickness of 3 nm.

[0118] Next, an anti-diffusion layer was formed on the surface of the FePt perpendicular magnetic layer by ion implantation. The reactive gas for the ion implantation was tetramethylsilane (C 4 H 12 Si) and argon gas mixture (C 4 H 12 Si:Ar=1:10) was ionized with RF plasma.

[0119] Next, a protective layer was formed by an ion beam method so that the combined thickness of the diffusion prevention layer and the protective layer was 2.2 nm.

[0120] After forming the protective layer, the diffusion prevention layer was examined by XPS and found to be a 0.15 nm thick 3SiO 2 -2Fe 2 O 3 -C(SiO 2 3 mol%, Fe 2 O 3 The Fe diffusion barrier layer contained 2 mol% Fe and the remainder was C layer. 2 O 3 is considered to be a diffusion product from the perpendicular magnetic layer, and C is considered to be a precipitate from tetramethylsilane and a diffusion product from the protective layer.

[0121] Next, a lubricating layer made of perfluoropolyether was formed on the protective layer by a dipping method to obtain a magnetic recording medium.

[0122] <Examples 12 to 19> The same procedure as in Example 11 was carried out, except that the diffusion prevention layer was formed under the conditions shown in Table 1.

[0123] <Comparative Examples 1 and 2> The same procedure was followed as in Example 1, except that the diffusion prevention layer was not formed during [Magnetic recording medium production] and the thickness of the protective layer was changed to 2.4 nm. The perpendicular magnetic layer was formed at a temperature of 290°C in Comparative Example 1 and 310°C in Comparative Example 2.

[0124] <Comparative Example 3> The same procedure as in Example 11 was carried out except that in [Preparation of a magnetic recording medium], the diffusion prevention layer was not formed and the thickness of the protective layer was changed to 2.2 nm.

[0125] Table 1 shows the type and deposition temperature of the perpendicular magnetic layer constituting the magnetic recording medium for each embodiment and comparative example, the composition, thickness, formation method, target type and gas used in the formation of the diffusion prevention layer, the total thickness of the diffusion prevention layer and protective layer, and the measurement results of corrosion spots.

[0126] [Table 1]

[0127] As can be seen from Table 1, the number of corrosion spots was 108 or less per surface in Examples 1 to 19. On the other hand, the number of corrosion spots was 150 or more per surface in Comparative Examples 1 to 3.

[0128] The magnetic recording media of Examples 1 to 19 are different from the magnetic recording media of Comparative Examples 1 to 3 in that they have a diffusion prevention layer between the perpendicular magnetic layer and the protective layer, which contains at least one component selected from the group consisting of Si, Ti, Cr, B, and Ru, or at least one of its carbides and oxides, and it has been confirmed that the number of corrosion spots can be reduced and corrosion resistance can be improved. Therefore, it can be said that the magnetic recording media according to this embodiment can be effectively used in magnetic recording and reproducing devices.

[0129] Although the embodiment has been described above, the above embodiment is presented as an example, and the present invention is not limited to the above embodiment. The above embodiment can be implemented in various other forms, and various combinations, omissions, substitutions, modifications, 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 scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0130] 10, 20, 31 Magnetic recording media 11, 21 Non-magnetic substrate 12 Soft magnetic layer 13, 22 Seed layer 14 Base layer 15, 24 perpendicular magnetic layer 151, 241 Top floor 152, 242 Layers other than the top layer 16, 25 Diffusion prevention layer 17, 26 protective layer 23-1 First Undercoat Layer 23-2 Second Undercoat Layer 30 Magnetic recording and reproducing device 32 Magnetic recording medium drive unit 33 Magnetic Head 34 Magnetic head drive unit 35 Recording / playback signal processing section

Claims

1. A non-magnetic substrate is provided with an underlayer, a perpendicular magnetic layer, a diffusion prevention layer, and a protective layer in this order, the perpendicular magnetic layer has a multi-layer structure, the uppermost layer of the perpendicular magnetic layer contains Co or Fe in magnetic grains; At least one layer 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 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; the diffusion prevention layer contains Si, Ti, Cr, B, and Ru in an amount of 3 mol % to 10 mol %, A magnetic recording medium, wherein the diffusion prevention layer has a thickness of 0.02 nm to 0.15 nm.

2. 2. The magnetic recording medium according to claim 1, wherein the diffusion prevention layer contains cobalt oxide or iron oxide.

3. 3. The magnetic recording medium according to claim 1, wherein the diffusion prevention layer contains C.

4. A magnetic recording and reproducing device comprising the magnetic recording medium according to any one of claims 1 to 3.

5. A method for producing a magnetic recording medium according to any one of claims 1 to 3, comprising the steps of: A method for producing a magnetic recording medium, comprising forming the diffusion prevention layer by using reactive sputtering, ion implantation or ion etching.

6. When using ion implantation, 6. The method for producing a magnetic recording medium according to claim 5, wherein the diffusion prevention layer is formed using a gas containing an organosilicon compound as a silicon source.

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