JP2012160243A - Thermally assisted magnetic recording medium and magnetic recording device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermally assisted magnetic recording medium having narrow inverse magnetic field dispersing and a magnetic recording device using the same.SOLUTION: In a magnetic recording device comprising a substrate, a plurality of base layers formed on the substrate and a magnetic layer mainly made of alloy having an L1structure, a thermally assisted magnetic recording medium in which at least one of the base layers is TiC is used. In addition, the base layer is formed on a base layer which is Cr or mainly made of Cr and has a BCC structure containing at least one of Ti, V, Mo, W, Mn and Ru.

Description

  The present invention relates to a heat-assisted magnetic recording medium and a magnetic storage device using the same.

Thermally assisted recording, in which writing is performed by irradiating the medium with near-field light to locally heat the surface and reducing the coercive force of the medium, the next-generation recording method that can realize a surface recording density of 1 Tbit / inch ² class It is attracting attention as. When heat-assisted recording is used, even a recording medium having a coercive force of several tens of kOe at room temperature can be easily written by the recording magnetic field of the current head. For this reason, it becomes possible to use a material having high magnetocrystalline anisotropy Ku of 10 ⁶ J / m ³ for the recording layer, and the magnetic particle size can be reduced to 6 nm or less while maintaining the thermal stability. . Examples of such high Ku material, L1 ₀ type FePt alloy ^{(Ku~7 × 10 6 J / m} 3) having a crystalline structure and, CoPt alloy ^{(Ku~5 × 10 6 J / m} 3) rules, such as Alloy It has been known.

The magnetic layer, when using the FePt alloy having an L1 ₀ type crystal structure, the FePt layer must have taken (001) orientation. This can be realized by using an appropriate material for the underlayer. Patent Document 1 shows that the FePt magnetic layer exhibits (001) orientation by using an MgO underlayer. MgO takes a NaCl structure, lattice constant and 0.421nm, L1 ₀ a-axis length of the FePt alloy structure and close. Therefore, by forming the FePt magnetic layer on the (100) -oriented MgO underlayer, the magnetic layer can be (001) -oriented. Non-Patent Document 1 describes that the FePt magnetic layer exhibits (001) orientation by using a TiN underlayer. TiN, like MgO, has an NaCl structure and a lattice constant close to that of MgO. For this reason, as in the case of MgO, the (001) orientation can be taken in the FePt magnetic layer.

Even in the heat-assisted magnetic recording medium, it is necessary to sufficiently reduce exchange coupling between magnetic crystal grains in the magnetic layer in order to obtain a high medium S / N ratio. For this reason, the grain boundary phase for dividing the magnetic crystal grains is added to the magnetic layer. As the grain boundary phase, an oxide such as SiO ₂ , TiO ₂ , MgO, C, or the like is used.

Japanese Patent Laid-Open No. 11-353648

J. et al. Vac. Sci. Technol. B 25 (6), 1892-1895 (2007)

And the magnetic layer L1 ₀ type FePt _alloy, SiO _2, TiO 2, oxides such as MgO, or thermally assisted medium consisting of C, the switching field distribution as compared to the perpendicular magnetic recording medium of the present situation (SFD: Switching Field Distribution) Is significantly larger. This is because the particle size dispersion of the magnetic crystal grains is large. As described above, how to reduce the particle size dispersion and how to reduce the SFD is an important issue in increasing the SNR of the heat-assisted recording medium.

The above object includes a substrate, a plurality of base layer formed on the substrate, a magnetic recording medium comprising a magnetic layer mainly composed of an alloy having an L1 ₀ structure, the underlayer, that the TiC can be solved. That is, the present invention relates to the following.

(1) and the substrate, the substrate and the underlayer formed on the plate, a magnetic recording medium comprising a magnetic layer mainly composed of an alloy having an L1 ₀ structure, underlying layer, characterized in that a TiC Thermally assisted magnetic recording medium.
(2) The heat-assisted magnetic recording medium according to (1), wherein the underlayer is formed of a plurality of layers, and the TiC is formed on the underlayer having a BCC structure.
(3) The TiC is formed on a base layer having a BCC structure containing Cr or Cr as a main component and containing at least one of Ti, V, Mo, W, Mn, and Ru. (2) The heat-assisted magnetic recording medium according to (2).
(4) The TiC contains Cr or Cr as a main component and contains at least one of Ti, V, Mo, W, Mn, and Ru, and at least one of B, C, and Si. The heat-assisted magnetic recording medium according to (1), wherein the heat-assisted magnetic recording medium is formed on an underlayer having a BCC structure containing Nb.
(5) The TiC is formed on a first underlayer having a BCC structure and a second underlayer having a BCC structure formed on the first underlayer, and the second underlayer The heat-assisted magnetic recording medium according to (1), wherein the underlayer has a lattice constant of 0.306 nm or more.
(6) The TiC is formed on a first underlayer made of NiAl or RuAl having a B2 structure and a second underlayer having a BCC structure formed on the first underlayer. The heat-assisted magnetic recording medium according to (1), wherein the second underlayer has a lattice constant of 0.306 nm or more.
(7) The second underlayer having a lattice constant of 0.306 nm or more is Mo, W, Ta, Nb, or an alloy having a BCC structure containing these (5) or (6 The heat-assisted magnetic recording medium according to (1).
(8) The heat-assisted magnetic recording medium according to (1), wherein the TiC is formed on an MgO underlayer.
(9) The magnetic layer is mainly composed of FePt or CoPt alloy having an L1 ₀ structure, and SiO ₂ , TiO ₂ , Cr ₂ O ₃ , Al ₂ O ₃ , Ta ₂ O ₅ , ZrO ₂ , Y ₂ O ₍₃ ) At least one kind of oxide or element selected from CeO ₂ , MnO, TiO, ZnO, and C is contained, (1) Any one of (1) to (8) Thermally assisted magnetic recording medium.
(10) A magnetic recording medium, a drive unit for rotating the magnetic recording medium, a laser generating unit for heating the magnetic recording medium, and a laser beam generated from the laser generating unit for guiding the laser light to the head tip In a magnetic storage device comprising a waveguide, a magnetic head having a near-field light generating unit attached to the tip of the head, a driving unit for moving the magnetic head, and a recording / reproducing signal processing system, the magnetic recording medium Is a heat-assisted medium according to any one of (1) to (9).

  According to the present invention, a heat-assisted recording medium having a low SFD is realized, and a magnetic storage device using the same can be provided.

It is a figure showing an example of the layer structure of the magnetic recording medium of this invention. It is a figure showing an example of the layer structure of the magnetic recording medium of this invention. It is a figure showing the XRD diffraction measurement result of the magnetic recording medium of this invention. It is a perspective view of the magnetic storage device of the present invention. It is a figure showing the magnetic head of this invention.

Thermally assisted magnetic recording medium of the present invention is a substrate, an underlayer formed on the substrate layer, a magnetic recording medium comprising a magnetic layer mainly composed of an alloy having an L1 ₀ structure, a base layer and TiC It is characterized by that. TiC, like MgO, has a NaCl structure and a lattice constant of 0.432 nm, which is close to the lattice constant of MgO. Therefore, when forming a magnetic layer consisting of L1 ₀ type FePt alloy (100) -oriented TiC underlayer, the FePt by epitaxial growth shows a (001) orientation. Inventors have made study various materials as the underlayer material for the L1 ₀ type FePt alloy, by using the TiC underlayer was found to be able to equalize the grain size of the FePt alloy.

In order to make the L1 ₀ -FePt alloy in the magnetic layer take (001) orientation, the TiC underlayer needs to have (100) orientation. In order to realize this, a BCC structure in which the underlayer has a multilayer structure, the TiC underlayer has Cr or Cr as a main component, and contains at least one of Ti, V, Mn, Mo, W, and Ru. It is desirable to form it on a base layer made of an alloy. In order to make the TiC underlayer take (100) orientation, the underlayer formed immediately below the TiC underlayer is hereinafter referred to as an orientation control layer. It is desirable that the orientation control layer has a BCC structure and has a (100) orientation. This can be realized by forming the orientation control layer on a seed layer made of an amorphous alloy. As the amorphous alloy, for example, Co-50 at% Ti, Co-50 at% Ta, Ni-50 at% Ti, Ni-50 at% Ta, Cr-50 at% Ti, Cr-50 at% Ta, or the like can be used. Further, when forming the orientation control layer on the amorphous alloy layer, it is desirable to heat the substrate at 150 ° C. or higher. As a result, the orientation control layer can have a good (100) orientation.

  For the orientation control layer, a material obtained by adding B, C, Si, or the like to the alloy containing Cr as a main component may be used. By adding the above elements, the particle size of the orientation control layer can be reduced to 10 nm or less, and at the same time, the particle size distribution can be made more uniform. Since the TiC underlayer is epitaxially grown on the orientation control layer and the magnetic layer is epitaxially grown on the TiC underlayer, the magnetic grain size can be made fine and uniform by making the orientation control layer grain size fine and uniform. Can do. The amount of additive element added to the orientation control layer containing Cr as a main component is not particularly limited as long as it is within a range that does not significantly deteriorate the BCC structure.

The orientation control layer may have a two-layer structure. For the first orientation control layer (substrate side), the above-described Cr or Cr alloy having a BCC structure can be used. Further, RuAl or NiAl having a B2 structure may be used. For the second orientation control layer (TiC side), a BCC structure metal or alloy having a lattice constant of 0.306 nm or more can be used. By the second orientation control layer lattice constant 0.306nm above, by introducing a tensile stress in the film plane direction of the TiC layer, it can improve the degree of order of FePt having an L1 ₀ structure. The upper limit of the lattice constant for the second orientation control is desirably set so that the lattice misfit with the first orientation control layer is 15% or less. If the lattice misfit exceeds 15%, the (100) orientation of the second orientation control layer deteriorates, which is not preferable.

  Specifically, BCC alloys such as CrMo, CrW, CrTa, CrNb, VMo, VW, VTa, VNb, MoW, MoTa, MoNb, WTa, WNb, and TaNb can be used for the second orientation control layer. However, when using an alloy containing Cr or V among the above alloys, it is necessary to adjust the composition so that the lattice constant is 0.306 nm or more. Moreover, you may use single metals, such as Mo, W, Ta, and Nb, for a 2nd orientation control layer.

  TiC may be formed on a (100) -oriented MgO underlayer. Since MgO is chemically stable and functions as a diffusion barrier layer from the underlayer, the substrate temperature can be set higher than when formed on the underlayer made of metal or alloy.

The magnetic layer, other FePt having an L1 ₀ structure, can also be used CoPt having an L1 ₀ structure. When the magnetic layer has a structure in which magnetic crystal grains are divided by a grain boundary phase, the grain boundary phase material includes SiO ₂ , TiO ₂ , Cr ₂ O ₃ , Al ₂ O ₃ , Ta ₂ O ₅ , ZrO. ₂ , Y ₂ O ₃ , CeO ₂ , MnO, TiO, ZnO, C can be used. The addition amount of the grain boundary phase material is preferably 20% by volume or more and 60% by volume or less by volume ratio. When it is less than 20% by volume, the grain boundary width becomes narrow, and the exchange coupling between the magnetic particles cannot be sufficiently reduced. On the other hand, if it exceeds 60 vol%, since the rule of the L1 ₀ structure of the magnetic crystal grains is lowered, unfavorably.

  A cap layer can be formed on the magnetic layer. Thereby, an appropriate exchange coupling is introduced between the magnetic crystal grains, and the switching field dispersion (SFD) can be further reduced. As the cap layer, HCP alloys such as CoCrPt and CoCrPtB, BCC alloys such as NiFe, NiCr, and FePt, or FCC alloys can be used. An amorphous alloy containing Co or Fe may also be used.

  A material having high thermal conductivity such as Cu, Ag, Al, or Au may be formed as the heat sink layer. In addition, a heat sink layer made of an alloy material combining the above elements can be used. The heat sink layer is preferably formed between the substrate and the base layer. When the soft magnetic layer described later is provided, the heat sink layer can be provided either above or below the soft magnetic layer. However, when the heat sink layer is thick, it should be provided below the soft magnetic underlayer and above it when it is thin. desirable.

  In order to improve the write characteristics, a soft magnetic underlayer can be formed. As the soft underlayer, soft magnetic alloys such as CoTaZr, CoNbZr, FeTaC, FeAlSi, CoFeTaSi, CoFeTaB, and CoFeZrSi can be used. The soft magnetic underlayer may be a single layer film made of the above alloy or a laminated film antiferromagnetically coupled with Ru interposed therebetween.

(Example 1, Comparative Example 1)
FIG. 1 shows an example of the layer structure of the magnetic recording medium produced in this example. On glass substrate 101, 4 nm Si underlayer 102, 10 nm TiC underlayer 103, 10 nm (Fe-50 at% Pt-8 at% Ag) -15 mol% SiO ₂ magnetic layer 104, 3 nm DLC-C protective film 105 Are sequentially formed. A heat-resistant glass substrate having a glass transition temperature of 700 ° C. or higher was used as the substrate, and the substrate was heated at 640 ° C. before forming the TiC underlayer. As a comparative example, a medium in which an MgO underlayer was formed instead of the TiC underlayer was produced.

When the X-ray diffraction measurement of the medium of this example was performed, the TiC underlayer had a NaCl structure, and only the (200) peak was observed. Further, from the magnetic layer, an L1 ₀ (001) peak and a mixed peak of L1 ₀ (002) and FCC (200) were observed. The former peak intensity ratio to the latter mixed peak intensity was 1.9. This indicates that the FePtAg alloy in the magnetic layer has a good degree of order. A clear diffraction peak was not confirmed from the Si underlayer, but as a result of cross-sectional TEM observation, it was found to be an amorphous structure.

On the other hand, when X-ray diffraction measurement was performed on a comparative medium using an MgO underlayer, a (200) peak was also observed from the MgO underlayer. From the magnetic layer, an L1 ₀ (001) peak and a mixed peak of L1 ₀ (002) and FCC (200) were observed. The former peak intensity ratio to the latter mixed peak intensity was 1.3, It was low compared with the Example medium.

  When the coercive force of the example medium and the comparative example medium was measured by applying a 7T magnetic field by PPMS, they were 31 kOe and 23 kOe, respectively. From the above, it was found that by using a TiC underlayer instead of the MgO underlayer, the order of the magnetic layer is improved and a medium having a high coercive force of 30 kOe or more can be obtained.

(Example 2, comparative example 2)
FIG. 2 shows an example of the layer structure of the magnetic recording medium manufactured in this example. On a glass substrate 201, a Ti-50at% Al adhesive layer 202, an Ag-5at% Pd heat sink layer 203, a Cr-50at% Ti seed layer 204, an orientation control layer 205, a TiC underlayer 206, (Fe-50at% Pt- 8 at% Cu) -45 at% C magnetic layer 207, Ni-20 at% Fe cap layer 208, and DLC-C protective film 209 are sequentially formed.

As the substrate, a heat-resistant glass substrate having a glass transition temperature of 650 ° C. or higher was used. Since the Ag alloy film of the heat sink layer has poor adhesion to glass, a 5 nm TiAl alloy film was formed as an adhesive layer between the heat sink layer and the substrate. When the orientation control layer was formed directly on the heat sink layer, the orientation control layer was not (100) oriented, so a 30 nm CrTi seed layer was formed, and an orientation control layer was formed thereon. Note that it is desirable to heat the substrate at 250 to 350 ° C. when forming the orientation control layer. Thereby, a favorable (100) orientation can be taken in the orientation control layer. For the orientation control layer, 12 nm of Cr (Example 2.1), Cr-8 at% Ti (Example 2.2), Cr-20 at% Mn (Example 2.3), Cr-40 at% V (Example) Example 2.4), Cr-25 at% Mo (Example 2.5), Cr-20 at% W (Example 2.6), Cr-20 at% Ru (Example 2.7), Cr-10 at% Ti -3 at% B (Example 2.8), Cr-20 at% Mo-5 at% B alloy (Example 2.9) was used. The thickness of the TiC underlayer was 2 nm. It is desirable to heat the substrate at 550 to 650 ° C. before forming the magnetic layer. Thereby promoting the L1 ₀ ordered the FePtCu alloy. In this example, the substrate was heated at 620 ° C. before the magnetic layer was formed.

  The film thicknesses of the magnetic layer and the cap layer were 10 nm and 4 nm, respectively. The film thickness of DLC-C was 3 nm. As a comparative example, a medium using a 5 nm Si layer as the orientation control layer was prepared (Comparative Example 2).

When X-ray diffraction measurement was performed on the medium of this example, an L1 ₀ (001) peak and a mixed peak of L1 ₀ (002) and FCC (200) were observed from the magnetic layer. The ratio of the former peak intensity to the latter mixed peak intensity was 2.1 or more in all Examples.

  This indicates that the FePtCu alloy in the magnetic layer has a good degree of order. In addition to the above, no diffraction peak from the magnetic layer was observed. On the other hand, only the BCC (200) peak was observed from the orientation control layer. Therefore, it was found that the orientation control layers used in this example all have a BCC structure and have a good (100) orientation. A clear diffraction peak was not observed because the film thickness was thin from the TiC underlayer, but the magnetic layer had a good (001) orientation, so it was epitaxially grown on the orientation control layer and (100) oriented. It is thought that it is taking. Also, no clear diffraction peak was observed from the CrTi seed layer. Therefore, it is considered that the CrTi seed layer has an amorphous or microcrystalline structure.

When the X-ray diffraction measurement of the comparative example medium was performed, only the L1 ₀ (001) peak and the mixed peak of L1 ₀ (002) and FCC (200) were observed from the magnetic layer as in the example medium. It was. However, the former peak intensity ratio with respect to the latter mixed peak intensity was 1.8, which was lower than that of the example medium. A clear diffraction peak was not confirmed from the Si underlayer, but as a result of cross-sectional TEM observation, it was found to be an amorphous structure. From the above, using a Cr alloy having a Cr or BCC structure, the orientation control layer, by forming a TiC underlayer the orientation control layer, further it can be enhanced rules of the magnetic alloy having an L1 ₀ structure all right.

  Next, planar TEM observation of the magnetic layers of the example medium and the comparative example medium was performed. Table 1 shows the average particle size <D> estimated from the TEM image and the particle size dispersion σ / <D> normalized by the average particle size. The average particle size of the magnetic layer of the medium of this example was 5-6 nm, and the normalized particle size dispersion was 0.25 or less. On the other hand, the average particle size of the comparative example medium using the Si underlayer as the orientation control layer was 5.6 nm, which was almost the same as that of the example medium, but the normalized particle size dispersion was 0.32. It was significantly larger than the medium. From this, it was found that the particle size dispersion can be significantly improved by using BCC structure Cr or Cr alloy for the orientation control layer. In Example 2.2 and Example 2.3 in which CrTi and CrMn alloys were used for the orientation control layer, the normalized particle size dispersion was particularly small. Therefore, it was found that using a CrTi or CrMn alloy for the orientation control layer is effective in achieving uniform particle size. In addition, Examples 2.8 and 2.9 in which boron was added to the orientation control layer had a particularly small average particle size. Therefore, it was found that the magnetic crystal grains can be refined by combining the orientation control layer containing boron and the TiC underlayer.

  Table 2 shows the coercive force Hc and the coercive force dispersion ΔHc / Hc of the medium of this example and the comparative medium. Here, Hc was measured by applying a 7T magnetic field by PPMS. ΔHc / Hc was measured by the method described in “IEEE Trans. Magn., Vol. 27, pp 4975-4777, 1991”. Specifically, in the major loop and the minor loop, the magnetic field when the magnetization value is 50% of the saturation value is measured, and from the difference between them, it is assumed that the reversed magnetic field distribution is a Gaussian distribution and ΔHc / Hc was calculated. ΔHc / Hc is a parameter corresponding to the half-value width of the reversal magnetic field distribution. The lower this value, the narrower the SFD and the better the medium SNR. All of the media of this example exhibited a high Hc of 19 kOe or more and a low ΔHc / Hc of 0.33 or less. In particular, Examples 2.5 and 2.6 using CrMo alloy and CrW alloy for the orientation control layer showed high Hc. Further, ΔHc / Hc of Example 2.2 and Example 2.3 in which the normalized particle size dispersion was particularly small was particularly low. On the other hand, Hc of the comparative example medium was almost the same as that of the example medium, but ΔHc / Hc was remarkably large. From the above, it was found that a heat assist medium having a low ΔHc / Hc can be obtained by using Cr or a Cr alloy for the orientation control layer.

(Example 3)
A medium having the same configuration as that of Example 2 and having an orientation control layer having a two-layer structure made of two types of BCC alloys was produced. The first orientation control layer (substrate side) provided on the CrTi seed layer uses 8 nm of Cr, the second orientation control layer (magnetic layer side) uses a 6 nm CrMo alloy, and the Mo concentration is 20 at. % To 100 at% (pure Mo). The layer configuration other than the orientation control layer and the film formation process are the same as those in Example 2.

When XRD diffraction measurement was performed, only the BCC (200) peak was observed from both the upper and lower orientation control layers. Also from the magnetic layer, the L1 ₀ (001) peak and the mixed peak of L1 ₀ (002) and FCC (200) were observed as in Example 2. For L1 ₀ -FePt (200) peak and FCC-FePt (200) mixed peak of _the L1 0 -FePt (001) peak intensity ratio as a function of the second lattice misfit orientation control layer and the TiC underlayer Plotted in FIG. Here, the lattice misfit, the lattice constant _{a 2} of the second orientation control layer, the lattice constant _{a TiC} of TiC underlayer lattice misfit _{= (√2 × a 2 -a TiC} ) / a TiC (% ). a ₂ was calculated from the BCC (200) peak from the second orientation control layer using the Bragg equation, and a _TiC was set to 0.324 nm from the literature value.

The peak intensity ratio increases with an increase in misfit, and shows a significantly higher value when the misfit becomes a positive value. From this, it was found that the degree of order of the L1 ₀ -FePt alloy can be significantly increased by setting the misfit to a positive value. When a Cr alloy having a BCC structure is used for the second orientation control layer, the lattice constant of the second orientation control layer needs to be approximately 0.306 nm or more in order to make the misfit positive. In this case, it is necessary to add a large amount of an element having a large atomic radius to Cr. For example, in the case of Mo addition, the amount of Mo addition is approximately 65% or more. For this reason, it is desirable to form the second orientation control layer on the first orientation control layer made of Cr or a Cr alloy having a small content of additive elements. If the second orientation control layer made of a Cr alloy containing a large amount of the additive element is formed directly on the CrTi seed layer without forming the first orientation control layer, the (100) orientation is lowered, which is not desirable.

  If the lattice misfit with the TiC underlayer is positive, the material of the second orientation control layer is not particularly limited. Specifically, BCC alloys such as CrMo, CrW, CrTa, CrNb, VMo, VW, VTa, VNb, MoW, MoTa, MoNb, WTa, WNb, and TaNb can be used.

The composition of the BCC alloy is not particularly limited as long as the lattice constant is 0.306 nm or more. However, the misfit with the first orientation control layer is preferably about 15% or less. If the misfit with the first orientation control layer exceeds 15%, epitaxial growth is inhibited, and the (100) orientation of the second orientation control layer is deteriorated, which is not preferable. In addition, a single metal such as Mo, W, Ta, or Nb may be used for the second orientation control layer.

  The material of the first orientation control layer is not particularly limited, but when a Cr alloy having a BCC structure is used, the content of the additive element to Cr is preferably 30% or less. If it exceeds 30%, the (100) orientation of the first orientation control layer deteriorates, which is not preferable. In addition, B2 structure NiAl, RuAl, or the like may be used for the first orientation control layer.

Example 4
A perfluoropolyether-based lubricant was applied to the medium shown in Example 2 (Example Mediums 2.1 to 2.9) and then incorporated into the magnetic storage device shown in FIG. This magnetic storage device includes a magnetic recording medium 401, a driving unit 402 for rotating the magnetic recording medium, a magnetic head 403, a driving unit 404 for moving the head, and a recording / reproducing signal processing system 405. The FIG. 5 shows details of the magnetic head. The head includes a main magnetic pole 501, an auxiliary magnetic pole 502, a coil 503 for generating a magnetic field, a laser diode (LD) 504, and a waveguide 507 for transmitting laser light 505 generated from the LD to the near-field generating element 506. And a reproducing head 511 including a reproducing element 510 sandwiched between a recording head 508 and a shield 509. Recording can be performed by heating the medium 512 with near-field light generated from the near-field light element and reducing the coercive force of the medium to a head magnetic field or less. A heating mechanism 513 including an LD, a waveguide, and a near-field generating element may be disposed between the main magnetic pole and the auxiliary magnetic pole. However, in this case, since the leading side of the main magnetic pole needs to be heated, the traveling direction of the medium is on the right side contrary to the figure.

  Table 3 shows the SNR and overwrite characteristic OW when a 1400 kFCI signal was recorded and the recording / reproduction characteristics were evaluated. Here, the LD power during recording was adjusted so that the recording track width defined as the half width of the track profile was 75 nm. All of the example media exhibited a high SNR of 15 dB or more and a high OW of 30 dB or more. Among them, Example Medium 2.2 and Example Medium 2.3 in which ΔHc / Hc was particularly small exhibited high SNR of 16 dB or more. In addition, Example Medium 2.6 and Example Medium 2.7 exhibited particularly high OW characteristics. Therefore, it was found that it is desirable to form a TiC underlayer on the CrV or CrRu underlayer in order to improve the OW characteristics.

DESCRIPTION OF SYMBOLS 101 ... Glass substrate 102 ... Si base layer 103 ... TiC base layer 104 ... Magnetic layer 105 ... DLC protective film 201 ... Glass substrate 202 ... TiAl adhesion layer 203 ... AgPd heat sink layer 204 ... CrTi seed layer 205 ... Orientation control layer 206 ... TiC Underlayer 207 ... magnetic layer 208 ... cap layer 209 ... DLC protective film 401 ... magnetic recording medium 402 ... medium driving unit 403 ... magnetic head 404 ... head driving unit 405 ... recording / reproduction signal processing system 501 ... main magnetic pole 502 ... auxiliary magnetic pole 503 ... Coil 504 ... Semiconductor laser diode 505 ... Laser light 506 ... Near-field light generator 507 ... Waveguide 508 ... Recording head 509 ... Shield 510 ... Reproducing element 511 ... Reproducing head

Claims (10)

A substrate, a base layer formed on the substrate, a magnetic recording medium comprising a magnetic layer mainly composed of an alloy having an L1 ₀ structure, the underlayer is thermally assisted magnetic, characterized in that the TiC recoding media. The heat-assisted magnetic recording medium according to claim 1, wherein the underlayer is formed of a plurality of layers, and the TiC is formed on the underlayer having a BCC structure. The TiC is formed on a base layer having a BCC structure containing Cr or Cr as a main component and containing at least one of Ti, V, Mo, W, Mn, and Ru. The thermally assisted magnetic recording medium according to claim 2. The TiC contains Cr or Cr as a main component and contains at least one of Ti, V, Mo, W, Mn, and Ru, and further contains at least one of B, C, and Si. The heat-assisted magnetic recording medium according to claim 1, wherein the heat-assisted magnetic recording medium is formed on an underlayer having a BCC structure. The TiC is formed on a first underlayer having a BCC structure and a second underlayer having a BCC structure formed on the first underlayer, and the second underlayer The thermally assisted magnetic recording medium according to claim 1, wherein the lattice constant of is 0.66 nm or more. The TiC is formed on a first underlayer made of NiAl or RuAl having a B2 structure and a second underlayer having a BCC structure formed on the first underlayer, The thermally assisted magnetic recording medium according to claim 1, wherein a lattice constant of the second underlayer is 0.306 nm or more. The heat according to claim 5 or 6, wherein the second underlayer having a lattice constant of 0.306 nm or more is Mo, W, Ta, Nb, or an alloy having a BCC structure containing these. Assisted magnetic recording medium. The heat-assisted magnetic recording medium according to claim 1, wherein the TiC is formed on an MgO underlayer. The magnetic layer is mainly composed of FePt or CoPt alloy having an L1 ₀ structure, and SiO ₂ , TiO ₂ , Cr ₂ O ₃ , Al ₂ O ₃ , Ta ₂ O ₅ , ZrO ₂ , Y ₂ O ₃ , CeO. 9. The heat-assisted magnetic recording medium according to claim 1, comprising at least one oxide or element selected from ₂ , MnO, TiO, ZnO, and C. 10. . A magnetic recording medium, a driving unit for rotating the magnetic recording medium, a laser generating unit for heating the magnetic recording medium, a waveguide for guiding laser light generated from the laser generating unit to the head tip, In a magnetic storage device comprising a magnetic head having a near-field light generating unit attached to the tip of the head, a driving unit for moving the magnetic head, and a recording / reproducing signal processing system, the magnetic recording medium is claimed. A magnetic storage device according to any one of 1 to 9, wherein the magnetic storage device is the heat-assisted medium.

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