MAGNETIC RECORDING MEDIUM AND MAGNETIC STORAGE APPARATUS

Abstract

A magnetic recording medium includes a substrate, an underlayer, and a magnetic layer including an alloy having a L1.sub.0 type crystal structure with a (001) orientation, wherein the substrate, the underlayer, and the magnetic layer are stacked in this order, the underlayer includes a first underlayer, the first underlayer is a crystalline layer that includes a material containing W as a main component and a nitride whose content ranges from 1 mol % to 80 mol %, and the nitride includes one or more elements selected from a group consisting of Al, B, Si, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W.

Claims

1. A magnetic recording medium comprising: a substrate; an underlayer; and a magnetic layer including an alloy having a L1.sub.0 type crystal structure with a (001) orientation, wherein the substrate, the underlayer, and the magnetic layer are stacked in this order, the underlayer includes a first underlayer, the first underlayer is a crystalline layer that includes a material containing W as a main component and a nitride whose content ranges from 1 mol % to 80 mol %, and the nitride includes one or more elements selected from a group consisting of Al, B, Si, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W.

2. The magnetic recording medium according to claim 1, wherein the content of the nitride in the first underlayer ranges from 20 mol % to 30 mol %, and the nitride includes Ti, Zr, or Ta.

3. The magnetic recording medium according to claim 1, wherein the underlayer further includes a second underlayer, and the second underlayer is a crystalline layer provided between the substrate and the first underlayer and containing W as a main component thereof.

4. The magnetic recording medium according to claim 1, further comprising: an orientation control layer between the substrate and the underlayer, wherein the orientation control layer is a Cr layer having a BCC structure, an alloy layer containing Cr as a main component and having a BCC structure, or an alloy layer having a B2 structure.

5. The magnetic recording medium according to claim 1, further comprising: a barrier layer between the underlayer and the magnetic layer, wherein the barrier layer includes one or more compounds selected from a group consisting of MgO, TiO, NiO, TiN, TaN, HfN, NbN, ZrC, HfC, TaC, NbC, and TiC, and has a NaCl type structure.

6. A magnetic storage apparatus comprising the magnetic recording medium according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG. 1 is a schematic diagram illustrating an example of a magnetic recording medium of an embodiment;

[0023] FIG. 2 is a schematic diagram illustrating an example of a magnetic storage apparatus of the embodiment; and

[0024] FIG. 3 is a schematic diagram illustrating an example of a magnetic head of FIG. 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] In the following, embodiments of the present invention will be described with reference to the accompanying drawings. The present invention is not limited to the embodiments as will be described below, and various variations and modifications may be made without departing from the scope of the present invention.

(Magnetic Recording Medium)

[0026] FIG. 1 illustrates an example of a magnetic recording medium of an embodiment.

[0027] A magnetic recording medium 100 includes a substrate 1, an underlayer 2, and a magnetic layer 3 including an alloy having a L1.sub.0 type crystal structure with a (001) orientation. The substrate 1, the underlayer 2, and the magnetic layer 3 are stacked in this order. The underlayer 2 includes a first underlayer 4. The first underlayer 4 is a crystalline layer that includes a material containing W as its main component and a nitride whose content ranges from 1 mol % to 80 mol %. The nitride includes one or more elements selected from a group consisting of Al, B, Si, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W.

[0028] By adopting the above-described configuration, the magnetic recording medium 100 can enhance the (001) orientation of the magnetic layer 3. Accordingly, a magnetic recording medium having a high SNR can be provided. Herein, W included in the first underlayer 4 has a body-centered cubic (BCC) lattice structure and thus has a high (100) orientation. This allows the (001) orientation of the alloy constituting the magnetic layer 3 and having the L1.sub.0 type crystal structure to be enhanced. Also, the nitride included in the first underlayer 4 can enhance a lattice match between the first underlayer 4 and the magnetic layer 3 without degrading the crystallinity and the (100) orientation of W.

[0029] In the present description and the claims, the material containing W as its main component refers to a material with a W content of at least 50 at. %. In the material containing W as its main component, the content of W is preferably at least 70 at. % and more preferably at least 90 at. %.

[0030] Examples of the material containing W as its main component included in the first underlayer 4 include, but are not limited to, W, WMo, WCu, WNi, WFe, WRe, and WC.

[0031] Examples of the nitride included in the first underlayer 4 include, but are not limited to, AlN, BN, Si.sub.3N.sub.4, TiN, ZrN, HfN, VN, NbN, TaN, CrN, MoN, and WN.

[0032] In the present embodiment, the content of the nitride in the first underlayer 4 ranges from 1 mol % to 80 mol %. In a case where the content of the nitride in the first underlayer 4 exceeds 80 mol %, the (100) orientation of the first underlayer 4 becomes poor. In a case where the content of the nitride in the first underlayer 4 is less than 1 mol %, it becomes difficult to enhance the (001) orientation of the magnetic layer 3.

[0033] In the present embodiment, preferably, the content of the nitride in the first underlayer 4 ranges from 20 mol % to 30 mol %. Preferably, a nitride including Ti, Zr, or Ta is used. By adopting this configuration, the (001) orientation of the magnetic layer 3 can be further enhanced.

[0034] In the present embodiment, the underlayer 2 has a two-layer structure. As a second underlayer 5, a crystalline layer containing W as its main component is provided between the substrate 1 and the first underlayer 4. The first underlayer 4 includes the material containing W as its main component as described above, and has a BCC structure. Therefore, the first underlayer 4 has a high (100) orientation and is lattice-matched with the magnetic layer 3, which is formed above the first underlayer 4 and includes the alloy having the L1.sub.0 type crystal structure with the (001) orientation. By providing the crystalline layer containing W as its main component as the second underlayer 5 under the first underlayer 4, the crystallization and the (100) orientation of the first underlayer 4 can be further enhanced.

[0035] In the present description and the claims, the crystalline layer containing W as its main component refers to a crystalline layer with a W content of at least 50 at. %. In the crystalline layer containing W as its main component, the content of W is preferably at least 70 at. % and more preferably at least 90 at. %.

[0036] Examples of the crystalline layer containing W as its main component include, but are not limited to, a W layer, a WMo layer, a WCu layer, a WNi layer, a WFe layer, a WRe layer and a WC layer.

[0037] In the present embodiment, an orientation control layer 6 is provided between the substrate 1 and the underlayer 2. The orientation control layer is a Cr layer having a BCC structure, an alloy layer containing Cr as its main component and having a BCC structure, or an alloy layer having a B2 structure. The orientation control layer 6 has the (100) orientation because the orientation control layer 6 is a layer for ensuring the (100) orientation of the underlayer 2 formed on the orientation control layer 6.

[0038] In the present description and the claims, the alloy containing Cr as its main component refers to an alloy with a Cr content of at least 50 at. %. In the alloy containing Cr as its main component, the content of Cr is preferably at least 70 at. % and more preferably at least 90 at. %.

[0039] Examples of the alloy containing Cr as its main component include, but are not limited to, a CrMn alloy, a CrMo alloy, a CrW alloy, a CrV alloy, a CrTi alloy, and a CrRu alloy.

[0040] Further, in order to improve the size and the dispersity of crystal grains of the underlayer 2, an element such as B, Si, and C may be added to the alloy containing Cr as its main component. However, in a case where such an element is added, the element is preferably added to an extent that the crystallization of the orientation control layer 6 is not deteriorated.

[0041] Moreover, examples of the alloy having a B2 structure include a RuAl alloy and a NiAl alloy.

[0042] In the present embodiment, a barrier layer is provided between the underlayer 2 and the magnetic layer 3.

[0043] The barrier layer 7 includes one or more compounds selected from a group consisting of MgO, TiO, NiO, TiN, TaN, HfN, NbN, ZrC, HfC, TaC, NbC, and TiC, and has a NaCl type structure.

[0044] In the present embodiment, as the magnetic layer 3, a magnetic layer including the alloy having the L1.sub.0 type crystal structure with the (001) orientation is used. In order to promote the ordering of the magnetic layer 3, the substrate 1 may be heated when the magnetic layer 3 is formed. The barrier layer 7 is a layer for suppressing the interfacial diffusion generated between the underlayer 2 and the magnetic layer 3.

[0045] In the present embodiment, the alloy constituting the magnetic layer 3 and having the L1.sub.0 type crystal structure has a high magnetic anisotropy constant Ku.

[0046] Examples of the alloy having the L1.sub.0 type crystal structure include a FePt alloy and a CoPt alloy.

[0047] In order to promote the ordering of the magnetic layer 3, a heating process may be preferably performed when the magnetic layer 3 including the alloy having the L1.sub.0 type crystal structure with the (001) orientation is formed. In this case, Ag, Au, Cu, and Ni, and the like may be added to the alloy having the L1.sub.0 type crystal structure such that the heating temperature (ordering temperature) decreases.

[0048] Also, crystal grains of the alloy having the L1.sub.0 type crystal structure included in the magnetic layer 3 are preferably magnetically isolated. Therefore, the magnetic layer 3 preferably contains one or more materials selected from a group consisting of SiO.sub.2, TiO.sub.2, Cr.sub.2O.sub.3, Al.sub.2O.sub.3Ta.sub.2O.sub.5, ZrO.sub.2, Y.sub.2O.sub.3, CeO.sub.2, MnO, TiO, ZnO, B.sub.2O.sub.3, C, B, and BN. This further ensures separation of exchange couplings between crystal grains, allowing the SNR of the magnetic recording medium 100 to be further improved.

[0049] A carbon protective layer 8 and a lubricant layer 9 made of a perfluoropolyether-based resin are provided on the magnetic layer 3.

[0050] Generally known materials can be used for the carbon protective layer 8 and the lubricant layer 9.

[0051] Further, the second underlayer 5, the orientation control layer 6, the barrier layer 7, the carbon protective layer 8, and the lubricant layer 9 may be omitted as necessary.

[0052] Further, a heat sink layer may be provided to quickly cool the magnetic layer 3.

[0053] The heat sink layer may be formed of a metal having high heat conductivity such as Ag, Cu, Al, and Au, or may be formed of an alloy containing, as its main component, a metal having high heat conductivity such as Ag, Cu, Al, and Au.

[0054] For example, the heat sink layer can be formed under the orientation control layer 6 or can be formed between the orientation control layer 6 and the barrier layer 7.

[0055] Further, a soft magnetic layer may be provided to improve write characteristics.

[0056] Examples of the material of the soft magnetic layer include, but are not limited to, an amorphous alloy such as a CoTaZr alloy, a CoFeTaB alloy, a CoFeTaSi alloy, and a CoFeTaZr alloy, a microcrystalline alloy such as an FeTaC alloy and an FeTaN alloy, and a polycrystalline alloy such as a NiFe alloy.

[0057] The soft magnetic layer may be formed by a single layer film or may have a multi-layer film structure in which layers are antiferromagnetically coupled via a Ru layer of a suitable thickness.

[0058] In addition to the above-described layers, other layers such as a seed layer and a bonding layer may be provided as necessary.

[0059] The magnetic recording medium 100 may be suitably used as a magnetic recording medium employing the heat-assisted magnetic recording method, or a magnetic recording medium employing the microwave-assisted recording method.

(Magnetic Storage Apparatus)

[0060] An example of a configuration of a magnetic storage apparatus of the present embodiment will be described.

[0061] In the present embodiment, the example of the configuration of the magnetic storage apparatus employing the heat-assisted magnetic recording method will be described. However, the magnetic storage apparatus of the present embodiment is not limited to the magnetic storage apparatus employing the heat-assisted magnetic recording method. The magnetic storage apparatus employing the microwave-assisted recording method may be used.

[0062] The magnetic storage apparatus of the present embodiment includes the magnetic recording medium of the present embodiment.

[0063] For example, the magnetic storage apparatus may include a magnetic recording medium driving part configured to rotate the magnetic recording medium, and a magnetic head having a near-field light generating element on its tip. Further, the magnetic storage apparatus may also include a laser generating part configured to heat the magnetic recording medium, a waveguide configured to guide laser light generated by the laser generating part to the near-field light generating element, a magnetic head driving part configured to move the magnetic head, and a recording/reproducing signal processing system.

[0064] FIG. 2 illustrates an example of the magnetic storage apparatus of the present embodiment.

[0065] The magnetic storage apparatus illustrated in FIG. 2 includes the magnetic recording medium 100, a magnetic recording medium driving part 101 configured to rotate the magnetic recording medium 100, a magnetic head 102, a magnetic head driving part 103 configured to move the magnetic head, and a recording/reproducing signal processing system 104.

[0066] FIG. 3 illustrates an example of the magnetic head 102.

[0067] The magnetic head 102 includes a recording head 208 and a reproducing head 211.

[0068] The recording head 208 includes a main magnetic pole 201, an auxiliary magnetic pole 202, a coil 203 that generates a magnetic field, a laser diode (LD) 204 that forms a laser generating part, and a waveguide 207 that transmits laser light 205 generated by the LD to a near-field light generating element 206.

[0069] The reproducing head 211 includes a reproducing element 210 sandwiched between shields 209.

[0070] The magnetic storage apparatus illustrated in FIG. 2 uses the magnetic recording medium 100, allowing the SNR to be improved and the magnetic storage apparatus having a high recording density to be provided.

EXAMPLES

[0071] Although a description will be given of specific examples, the present invention is not limited to these specific examples.

Example 1

[0072] A magnetic recording medium 100 (see FIG. 1) was produced. A process for producing the magnetic recording medium 100 will be described below.

[0073] As a seed layer, a film made of Cr-50 at. % Ti (an alloy with a CR content of 50 at. % and a Ti content of 50 at. %) and having a thickness of 25 nm was formed on a glass substrate 1 having an outer diameter of 2.5 inches. The substrate 1 was heated at 300 C. Subsequently, as an orientation control layer 6, a film made of Cr-5 at. % Mn (an alloy with a Cr content of 95 at. % and a Mn content of 5 at. %) was formed. Next, as a second underlayer 5, a W layer having a thickness of 20 nm was formed. As a first underlayer 4, a film made of W-20TaN (an alloy with a W content of 80 mol % and a TaN content of 20 mol %) was formed on the second underlayer 5. Further, as a barrier layer 7, a MgO film having a thickness of 2 nm was formed. Subsequently, the substrate 1 was heated at 580 C. As a magnetic layer 3, a film made of (Fe-45 at. % Pt)-12 mol % SiO.sub.2-6 mol % BN (an alloy with an FePt alloy content of 82 mol % in which a Fe content is 55 at. % and a Pt content is 45 at. %, a SiO.sub.2 content of 12 mol %, and a BN content of 6 mol %) and having a thickness of 10 nm was formed. Further, a carbon protective layer 8 having a thickness of 3 nm was formed. A lubricant layer 9 made of a perfluoropolyether-based fluororesin was formed on the surface of the carbon protective layer 8. Accordingly, the magnetic recording medium 100 was produced.

Examples 2 Through 5

[0074] Magnetic recording mediums were produced in the same manner as Example 1, except that the composition of the first underlayer 4 was changed to W-25TaN, W-30TaN, W-50TaN, and W-75TaN, respectively.

Examples 6 Through 16

[0075] Magnetic recording mediums were produced in the same manner as Example 1, except that the composition of the first underlayer 4 was changed to W-25ZrN, W-25TiN, W-25VN, W-25NbN, W-25AlN, W-25BN, W-25Si3N4, W-25HfN, W-25CrN, W-25MoN, and W-25WN, respectively.

Example 17

[0076] A magnetic recording medium was produced in the same manner as Example 2, except that the second underlayer 5 was not formed.

Examples 18 Through 20

[0077] Magnetic recording mediums were produced in the same manner as Example 2, except that the composition of the second underlayer 5 was changed to W-10Mo (alloy with a W content of 90 at. % and a Mo content of 10 at. %), W-20Mo, and W-30Mo, respectively.

Comparative Example 1

[0078] A magnetic recording medium was produced in the same manner as Example 1, except that the first underlayer 4 was not formed.

Comparative Examples 2 and 3

[0079] Magnetic recording mediums were produced in the same manner as Example 17 and Example 1, respectively, except that the composition of the first underlayer 4 was changed to TiN.

Comparative Examples 4 and 5

[0080] Magnetic recording mediums were produced in the same manner as Example 17 and Example 1, respectively, except that the composition of the first underlayer 4 was changed to TaN.

Comparative Examples 6 and 7

[0081] Magnetic recording mediums were produced in the same manner as Example 17 and Example 1, respectively, except that the composition of the first underlayer 4 was changed to W-8Si (alloy with a W content of 92 at. % and a Si content of 8 at. %).

Comparative Examples 8 and 9

[0082] Magnetic recording mediums were produced in the same manner as Example 17 and Example 1, respectively, except that the composition of the first underlayer 4 was changed to W-8SiO.sub.2 (alloy with a W content of 92 mol % and a SiO.sub.2 content of 8 at. %).

(Signal Intensity of FePt (001) Peak)

[0083] Using an X-ray diffractometer, the signal intensity of the FePt (001) peak was obtained by measuring X-ray diffraction spectra of a sample of a magnetic recording medium after a step of forming the magnetic layer 3 is completed.

(SNR)

[0084] The SNR was measured by recording an all-one pattern signal with a linear recording density of 1500 kFCI on a magnetic recording medium by using the magnetic head 102 (see FIG. 3). Power supplied to the laser diode was adjusted such that a track width MWW, which was defined as the half width of a track profile, was 60 nm.

[0085] Table 1 illustrates evaluation results of signal intensities of the FePt (001) peak and SNRs.

TABLE-US-00001 TABLE 1 SIGNAL FIRST SECOND INTENSITY UNDER- UNDER- OF FePt SNR LAYER LAYER (001) PEAK [dB] EXAMPLE 1 W-20TaN W 154 9.0 EXAMPLE 2 W-25TaN W 167 9.2 EXAMPLE 3 W-30TaN W 175 9.4 EXAMPLE 4 W-50TaN W 150 8.6 EXAMPLE 5 W-75TaN W 158 8.7 EXAMPLE 6 W-25ZrN W 180 8.6 EXAMPLE 7 W-25TiN W 149 8.5 EXAMPLE 8 W-25VN W 147 8.3 EXAMPLE 9 W-25NbN W 152 8.4 EXAMPLE 10 W-25AlN W 150 8.2 EXAMPLE 11 W-25BN W 155 8.4 EXAMPLE 12 W-25Si.sub.3N.sub.4 W 145 8.1 EXAMPLE 13 W-25HfN W 156 8.6 EXAMPLE 14 W-25CrN W 155 8.5 EXAMPLE 15 W-25MoN W 153 8.4 EXAMPLE 16 W-25WN W 157 8.6 EXAMPLE 17 W-25TaN 147 8.3 EXAMPLE 18 W-25TaN W-10Mo 165 9.2 EXAMPLE 19 W-25TaN W-10Mo 161 9.1 EXAMPLE 20 W-25TaN W-10Mo 155 9.0 COMPARATIVE W 135 7.8 EXAMPLE 1 COMPARATIVE TaN 125 7.5 EXAMPLE 2 COMPARATIVE TaN W 140 8.0 EXAMPLE 3 COMPARATIVE TiN 107 7.0 EXAMPLE 4 COMPARATIVE TiN W 111 7.3 EXAMPLE 5 COMPARATIVE W-8Si 124 7.5 EXAMPLE 6 COMPARATIVE W-8Si W 132 7.8 EXAMPLE 7 COMPARATIVE W-8SiO.sub.2 127 7.7 EXAMPLE 8 COMPARATIVE W-8SiO.sub.2 W 138 8.0 EXAMPLE 9

[0086] As seen from Table 1, the magnetic recording mediums according to Examples 1 through 20 have high signal intensities of the FePt (001) peak and high SNRs.

[0087] Conversely, the magnetic recording medium according to the comparative example 1 has a low signal intensity of the FePt (001) peak and a low SNR because the first underlayer 4 was not formed.

[0088] The magnetic recording mediums according to the comparative examples 2 through 5 have low signal intensities of the FePt (001) peak and low SNRs because the first underlayer 4 does not include W.

[0089] The magnetic recording mediums according to the comparative examples 6 through 9 have low signal intensities of the FePt (001) peak and low SNRs because the first underlayer 4 does not include a nitride.

[0090] According to at least one embodiment, a magnetic recording medium having a high signal-to-noise ratio (SNR) can be provided.

[0091] Further, the present invention is not limited to these embodiments, but various variations and modifications may be made without departing from the scope of the present invention.