CN1768376A - Magnetic recording medum, production process therefor, and magnetic recording and reproducing apparatus - Google Patents

Abstract

The purpose of this invention is to provide a magnetic recording medium that can reduce media noise. This invention provides a magnetic recording medium comprising, in the following order on a non-magnetic substrate, at least a non-magnetic undercoating layer, a first magnetic layer, a non-magnetic coupling layer, a second magnetic layer, and a protective layer, wherein the second magnetic layer is antiferromagnetically coupled to the first magnetic layer, and the first magnetic layer is made of a CoCrZr alloy.

Description

Magnetic recording medium, manufacturing method thereof, and magnetic recording and reproducing device

Cross References to Related Applications

Pursuant to 35 U.S.C. §119(e), this application claims priority to US Provisional Application 60/461802, filed April 11, 2003.

This application is based on Japanese Patent Application No. 2003-103367 filed in Japan on April 7, 2003, the contents of which are incorporated herein by reference.

technical field

The present invention relates to a magnetic recording medium used in a hard disk drive or the like, a method for manufacturing the magnetic recording medium, and a magnetic recording and reproducing device. In particular, the present invention relates to a magnetic recording medium in which medium noise is reduced, a method for manufacturing the magnetic recording medium, and a magnetic recording and reproducing apparatus.

Background technique

Currently, the recording density of a hard disk drive (HDD), which is a magnetic recording and reproducing device, is increasing at a rate of 60% per year, and this trend is expected to continue.

Magnetic recording media used in hard disk drives are desired to have increased recording density, thereby requiring the recording media to have increased coercive force and reduced noise.

Main magnetic recording media used in hard disk drives have a structure in which a metal film is laminated on a magnetic recording medium substrate by sputtering.

Substrates used as magnetic recording medium substrates include aluminum substrates and glass substrates, which are widely used. In this way, a commonly used aluminum substrate is formed, and a layer of NiP film with a thickness of about 10 μm is formed on a mirror-polished Al-Mg alloy substrate by electroless plating, and the surface is mirror-polished. As the glass substrate, an amorphous glass substrate and a glass-ceramic substrate are used. Mirror polish any glass substrate before using it.

At present, magnetic recording media generally used in hard disk drives have a structure in which a nonmagnetic undercoat layer (for example, NiAl alloy, Cr, or Cr alloy), a nonmagnetic intermediate layer (for example, , CoCr alloy or CoCrTa alloy), a magnetic layer (eg, Co-Cr-Pt-Ta-based alloy or Co-Cr-Pt-B-based alloy), and a protective layer (eg, carbon), wherein the protective layer is covered by a lubricating layer.

In order to increase recording density, it is necessary to increase SNR (signal-to-noise ratio) during high-frequency recording. Kenneth, E.J. explained in the article "Magnetic materials and structures for thin-film recording media" published in JOURNAL OF APPLIED PHYSICS 2000, Volume 87, No. 9, Page 5365, that in order to improve SNR, it is necessary to make the recording layer (magnetic layer) The diameter of the crystal particles is small and uniform.

However, when the diameter of the crystal grains in the recording layer (magnetic layer) is made small and uniform to improve SNR, the volume of the crystal grains becomes smaller, and the thermal stability of the crystal grains is poor. This is disclosed in the article "Temperature Dependence of Thermal Stability in Longitudinal Media" published by Sharat Batra et al. in IEEE Trans. Magn. 1999, Vol. 35, No. 5, p. 2736.

As a solution to this problem, Japanese Unexamined Patent Application First Publication No. 2001-56921 has proposed a magnetic recording medium in which magnetic layers are respectively formed above and below a nonmagnetic coupling layer made of ruthenium or the like, And the magnetization directions of these magnetic layers are opposite to and parallel to each other.

In this magnetic recording medium, since the magnetization directions of the two magnetic layers are opposite to each other, the portion involved in magnetic recording and reproduction is sufficiently thinner than the entire recording layer. Thereby the SNR can be improved. On the other hand, the volume of crystal grains in the entire recording layer becomes larger; thus, thermal stability can be improved.

Media using this technique are generally referred to as AFC media (Antiferromagnetic Coupling Media) or SFM (Synthetic Ferrimagnetic Media). Here, it is simply referred to as AFC media or media.

In the magnetic recording medium disclosed in Japanese Unexamined Patent Application First Publication No. 2001-56921, a magnetic layer is formed each above and below the nonmagnetic coupling layer to sandwich them. In this magnetic recording medium, the magnetic layer formed on the nonmagnetic substrate side is a ferromagnetic layer. The ferromagnetic layer is made of at least one material selected from Co, Ni, Fe, Ni-based alloys, Fe-based alloys, and Co-based alloys (including CoCrTa, CoCrPt, and CoCrPtM). In addition, the symbol M represents B, Mo, Nb, Ta, W, Cu, or an alloy containing these elements.

However, in conventional recording media, it is difficult to sufficiently reduce media noise in response to increased recording density.

The present invention is accomplished based on the above, so that an object of the present invention is to provide a magnetic recording medium capable of sufficiently reducing medium noise, a method of manufacturing the magnetic recording medium, and a magnetic recording and reproducing system including the magnetic recording medium. device.

Contents of the invention

The inventors of the present invention have conducted intensive studies to solve these problems, and found that by employing a CoCrZr alloy as the first magnetic layer, it is possible to reduce medium noise and achieve high recording density. The present invention was accomplished based on this finding.

(1) The first invention to solve these problems is a magnetic recording medium comprising, on a nonmagnetic substrate, at least a nonmagnetic undercoat layer, a first magnetic layer, a nonmagnetic coupling layer, a second magnetic layer, and a protective layer, wherein the second magnetic layer is antiferromagnetically coupled to the first magnetic layer; and the first magnetic layer is made of a CoCrZr alloy.

(2) The second invention to solve these problems is a magnetic recording medium comprising, on a nonmagnetic substrate, at least a nonmagnetic undercoat layer, a first magnetic layer, a nonmagnetic coupling layer, a second magnetic layer, a non-magnetic coupling layer, a third magnetic layer, and a protective layer, wherein the third magnetic layer is antiferromagnetically coupled to the second magnetic layer; the second magnetic layer is antiferromagnetically coupled to the first magnetic layer ; and the first magnetic layer is made of CoCrZr alloy.

(3) The third invention for solving these problems is the magnetic recording medium as described in the invention (1) or (2), wherein the first magnetic layer comprises 5 to 22 atomic % of Cr and 1 to 10 atomic % of Zr .

(4) A fourth invention that solves these problems is the magnetic recording medium as described in any one of inventions (1) to (3), wherein the thickness of the first magnetic layer is in the range of 0.5 to 10 nm.

(5) The fifth invention that solves these problems is the magnetic recording medium as described in any one of inventions (1) to (4), wherein the non-magnetic coupling layer is selected from Ru, Rh, Ir, Cr, Re , Ru-based alloy, Rh-based alloy, Ir-based alloy, Cr-based alloy, and Re-based alloy; and the thickness of the non-magnetic coupling layer is in the range of 0.5-1.5 nm.

(6) A sixth invention that solves these problems is the magnetic recording medium as described in any one of inventions (1) to (5), wherein the nonmagnetic undercoat layer has a multilayer structure including a layer made of Cr Or a layer made of a Cr-based alloy including Cr and at least one selected from Ti, Mo, Al, Ta, W, Ni, B, Si and V.

(7) The seventh invention that solves these problems is the magnetic recording medium as described in any one of inventions (1) to (6), wherein the non-magnetic undercoat layer has a multilayer structure including NiAl-based alloy, RuAl A layer of one of Cr-based alloys and Cr-based alloys; wherein the Cr-based alloy includes Cr and at least one of Ti, Mo, Al, Ta, W, Ni, B, Si and V.

(8) An eighth invention that solves these problems is the magnetic recording medium as described in any one of inventions (1) to (7), wherein the nonmagnetic substrate is one of a glass substrate and a silicon substrate.

(9) The ninth invention that solves these problems is the magnetic recording medium according to any one of inventions (1) to (8), wherein the non-magnetic substrate is made of one of Al, Al alloy, glass, and silicon. A substrate made of this kind; on the substrate, a film made of NiP or a NiP alloy is formed.

(10) The tenth invention that solves these problems is the magnetic recording medium according to any one of inventions (1) to (9), wherein the second magnetic layer is made of a CoCrTa-based alloy, a CoCrPtTa-based alloy, a CoCrPtB-based alloy, and At least one of CoCrPtBM-based alloys (where M represents at least one of Ta and Cu).

(11) The eleventh invention that solves these problems is the magnetic recording medium according to any one of inventions (2) to (9), wherein the second magnetic layer and the third magnetic layer are made of a CoCrTa-based alloy, At least one of CoCrPtTa-based alloys, CoCrPtB-based alloys, and CoCrPtBM-based alloys (wherein M represents at least one of Ta and Cu).

(12) The twelfth invention for solving these problems is a method of manufacturing a magnetic recording medium comprising, on a nonmagnetic substrate, at least a nonmagnetic undercoat layer, a first magnetic layer, a nonmagnetic a coupling layer, a second magnetic layer, and a protective layer; wherein the second magnetic layer is antiferromagnetically coupled to the first magnetic layer, wherein the method includes the step, wherein the first magnetic layer is made of a CoCrZr alloy .

(13) A thirteenth invention that solves these problems is a method of manufacturing a magnetic recording medium comprising, on a nonmagnetic substrate, at least a nonmagnetic undercoat layer, a first magnetic layer, a nonmagnetic a coupling layer, a second magnetic layer, a non-magnetic coupling layer, a third magnetic layer, and a protective layer; the third magnetic layer is antiferromagnetically coupled to the second magnetic layer; and the second magnetic layer is coupled to the A first magnetic layer is antiferromagnetically coupled, wherein the method includes the step, wherein the first magnetic layer is made of a CoCrZr alloy.

(14) A fourteenth invention that solves these problems is a magnetic recording and reproducing apparatus comprising the magnetic recording medium as described in any one of claims (1) to (11), and A magnetic head that records information in and reproduces information from the magnetic recording medium.

Description of drawings

1 is a sectional view showing a first embodiment of a magnetic recording medium of the present invention;

2 is a cross-sectional view showing a second embodiment of the magnetic recording medium of the present invention;

3 is a cross-sectional view showing a third embodiment of the magnetic recording medium of the present invention;

4 is a sectional view showing a fourth embodiment of the magnetic recording medium of the present invention;

5 is a sectional view showing a fifth embodiment of the magnetic recording medium of the present invention;

Figure 6 is used to explain the Hex measurement method;

FIG. 7 is a schematic diagram showing an example magnetic recording and reproducing apparatus according to the present invention.

Detailed ways

Fig. 1 schematically shows a first embodiment of the magnetic recording medium of the present invention. In the magnetic recording medium shown in FIG. 1, a nonmagnetic undercoat layer 2, a first magnetic layer 3, a nonmagnetic coupling layer 4, a second magnetic layer 5, a protective Layer 6, and lubricating layer 7.

Fig. 2 schematically shows a second embodiment of the magnetic recording medium of the present invention. In the magnetic recording medium shown in FIG. 2, a non-magnetic undercoat layer 2, a first magnetic layer 3, a first non-magnetic coupling layer 4, and a second magnetic layer 5 are sequentially stacked on a non-magnetic substrate 1 in the following order , the second non-magnetic coupling layer 8 , the third magnetic layer 9 , the protective layer 6 , and the lubricating layer 7 .

The non-magnetic substrate 1 is preferably an Al substrate or an Al alloy substrate including a NiP or NiP-based alloy film thereon.

Examples of the nonmagnetic substrate 1 also include substrates made of nonmetallic materials such as glass, ceramics, silicon, silicon carbide, carbon, or resin. A substrate made of such a non-metallic material and comprising a NiP film or NiP-based alloy film on the non-metallic material can also be used.

In particular, non-magnetic substrate 1 is preferably a substrate made of one selected from Al, Al alloy, glass, and silicon, and including a NiP film or a NiP alloy film.

In terms of surface flatness, the non-metallic material is preferably glass or silicon. In particular, it is more preferable to use a glass substrate from the viewpoints of cost and durability. Examples of glass materials that can be used as the nonmagnetic substrate include amorphous glass and glass ceramics.

Examples of amorphous glass include commonly used soda lime glass, aluminoborosilicate glass, and aluminosilicate glass. Examples of glass ceramics include lithium-containing glass ceramics.

Examples of the ceramic substrate include sintered products mainly containing commonly used alumina, silicon nitride or similar compounds, and fiber-reinforced products thereof.

In a magnetic recording and reproducing apparatus, in order to increase the recording density, it is necessary to lower the flying height of the magnetic head. Therefore, the non-magnetic substrate 1 needs to have improved surface flatness. Specifically, the non-magnetic substrate 1 needs to have a surface average roughness (Ra) of 2 nm or less, preferably 1 nm or less.

The non-magnetic substrate 1 preferably has texturing grooves formed by performing a texturing process on its surface. The texturing process is preferably carried out so that the average surface roughness of the non-magnetic substrate 1 is in the range of 0.1 nm to 0.7 nm, (more preferably in the range of 0.1 nm to 0.5 nm, most preferably in the range of 0.1 nm to 0.35 nm range). From the viewpoint of enhancing the magnetic anisotropy in the circumferential direction of the magnetic recording medium, it is preferable to form textured grooves in the substantially circumferential direction of the non-magnetic substrate 1 .

The non-magnetic substrate 1 preferably has a surface minute waviness (Wa) of 0.3 nm or less (more preferably 0.25 nm or less).

Considering the floating stability of the magnetic head, at least one chamfer section (chamfer section) of the end surface and the side surface of the non-magnetic substrate 1 preferably has a surface average roughness (Ra) of 10 nm or less (more preferably 9.5 nm or smaller).

Surface minute waviness (Wa) can be determined by, for example, a surface average roughness meter (P-12, a product of KLM-Tencor, USA) as a surface average roughness value measured within a range of 80 μm.

On a nonmagnetic substrate 1, a nonmagnetic undercoat layer 2 is formed. The nonmagnetic undercoat layer 2 may have a one-layer structure or a multi-layer structure including a plurality of layers.

The nonmagnetic undercoat layer 2 may be made of a Cr alloy containing Cr and at least one of Ti, Mo, Al, Ta, W, Ni, B, Si, and V. The non-magnetic undercoat layer 2 can also be made of Cr.

When the nonmagnetic undercoat layer 2 has a multilayer structure, at least one of the layers constituting the nonmagnetic undercoat layer 2 may be made of Cr alloy or Cr.

The non-magnetic primer layer 2 is preferably made of at least one of NiAl-based alloys, RuAl-based alloys and Cr alloys, which contain Cr and Ti, Mo, Al, Ta, W, Ni, B, Si and At least one of V.

When the nonmagnetic undercoat layer 2 has a multilayer structure, at least one of the layers constituting the nonmagnetic undercoat layer 2 may be made of at least one of NiAl-based alloys, RuAl-based alloys, and Cr alloys.

The thickness of the nonmagnetic undercoat layer 2 having a single-layer structure is preferably in the range of 1 to 40 nm (more preferably 3 to 15 nm). If the thickness of the nonmagnetic undercoat layer 2 is less than 1 nm, crystal growth is insufficient. If it exceeds 40nm, the crystal grains are too large, resulting in increased medium noise.

The nonmagnetic undercoat layer 2 preferably has a multilayer structure. If the nonmagnetic undercoat layer 2 has a multilayer structure, crystals are oriented, and its electromagnetic conversion characteristics are improved.

When forming the nonmagnetic undercoat layer 2 having a multilayer structure, the thickness of the layers constituting the nonmagnetic undercoat layer 2 may be in the range of 1 to 40 nm (more preferably, 3 to 15 nm). If the thickness of the layer is less than 1 nm, crystal growth is insufficient. On the contrary, if it exceeds 40 nm, the crystal grains are too large, resulting in an increase in medium noise.

The total thickness of the non-magnetic undercoat layer 2 having a multilayer structure may be in the range of 3 to 150 nm.

The first magnetic layer 3 is made of a CoCrZr-based alloy. In the first magnetic layer 3 , the content of Cr is preferably in the range of 5 to 22 atomic %, and the content of Zr is preferably in the range of 1 to 10 atomic % from the viewpoint of SNR.

The thickness of the first magnetic layer 3 is preferably in the range of 0.5 to 10 nm (more preferably 0.5 to 5 nm). If the thickness is less than 0.5 nm, crystal epitaxial growth is insufficient, so that sufficient coercive force cannot be obtained. On the contrary, if the thickness exceeds 10 nm, the portion where antiferromagnetic coupling does not occur increases medium noise.

The CoCrZr-based alloy from which the first magnetic layer 3 is made may include other elements having auxiliary effects (eg, enhanced orientation, reduced grain size). Examples of the other elements include one or more selected from Ti, V, Mn, Hf, Ru, B, Al, Si, and W. The total content of other elements is preferably 10 atomic % or less. If the total content exceeds 10 atomic %, the effect is weakened (increased orientation or reduced particle size). If its content is less than 0.1 atomic %, the effect is also weakened. Therefore, it is more preferable to control the total content in the range of 0.1 to 10 atomic %.

The nonmagnetic coupling layers 4 and 8 are preferably made of one selected from Ru, Rh, Ir, Cr, Re, Ru-based alloys, Rh-based alloys, Ir-based alloys, Cr-based alloys, and Re-based alloys.

Since these materials have a large exchange energy constant, when the non-magnetic coupling layer is made of one of these materials, it is possible to make the magnetization direction of the magnetic layer (located above and below the non-magnetic coupling layer) tend to such a condition that in the conditions, the magnetization directions are opposite to each other and parallel to each other.

In particular, since Ru has the largest coupling energy coefficient among these materials, it is preferable to use Ru in the nonmagnetic coupling layers 4 and 8 .

The coupling energy coefficient represents the strength of the exchange interaction between the magnetic layers (located above and below the non-magnetic coupling layer). The non-magnetic coupling layer preferably has a larger coupling energy coefficient.

The thickness of the nonmagnetic coupling layers 4 and 8 is preferably in the range of 0.5 to 1.5 nm (more preferably in the range of 0.6 to 1.0 nm). If the thicknesses of the nonmagnetic coupling layers 4 and 8 are within this range, the nonmagnetic coupling layers 4 and 8 have sufficient antiferromagnetic coupling.

The above-mentioned nonmagnetic coupling layer is not used in the nonmagnetic coupling layer 4 shown in FIG. 1 , but may be used in the first and second nonmagnetic coupling layers 4 and 8 shown in FIG. 2 .

The second and third magnetic layers may be made of a material other than a CoCrZr-based alloy, such as a Co alloy containing Co as a main component and having a hcp structure.

Specifically, the second and third magnetic layers may be made of CoCrTa-based alloys, CoCrPt-based alloys, CoCrPtTa-based alloys, CoCrPtB-based alloys, CoCrPtBTa-based alloys, CoCrPtBCu-based alloys, CoRuTa-based alloys, and CoCrPtBM-based alloys (wherein, M It is made of one or more alloys of at least one of Ta and Cu).

Among these materials, at least one selected from CoCrTa-based alloys, CoCrPtTa-based alloys, CoCrPtB-based alloys, and CoCrPtBM-based alloys (where M is at least one of Ta and Cu) is preferably used.

When a CoCrPt-based alloy is used for the second and third magnetic layers, the Cr content is preferably in the range of 10 to 25 at%, and the Pt content is preferably in the range of 8 to 16 at%, from the viewpoint of SNR.

When a CoCrPtB-based alloy is used, from the viewpoint of SNR, the Cr content is preferably in the range of 10 to 25 atomic %, the Pt content is preferably in the range of 8 to 16 atomic %, and the B content is preferably in the range of 1 to 20 atomic % % range.

When a CoCrPtBTa-based alloy is used, from the viewpoint of SNR, the Cr content is preferably in the range of 10 to 25 atomic %, the Pt content is preferably in the range of 8 to 16 atomic %, and the B content is preferably in the range of 1 to 20 atomic % In the range of , and the Ta content is preferably in the range of 1 to 4 atomic %.

When a CoCrPtBCu-based alloy is used, from the viewpoint of SNR, the Cr content is preferably in the range of 10 to 25 atomic %, the Pt content is preferably in the range of 8 to 16 atomic %, and the B content is preferably in the range of 1 to 20 atomic % , and the Cu content is preferably in the range of 1 to 4 atomic %.

In a magnetic recording medium including two magnetic layers (i.e., a first magnetic layer 3 and a second magnetic layer 5) as shown in FIG. 1, the second magnetic layer 5 preferably has a thickness of 10nm or larger. From the viewpoint of high recording density, the thickness of the second magnetic layer 5 is preferably 40 nm or less. This is because, if the thickness exceeds 40 nm, satisfactory recording and reproducing characteristics cannot be obtained.

In a magnetic recording medium including three magnetic layers (ie, first to third magnetic layers 3, 5, and 9) as shown in FIG. As for the antiferromagnetic coupling strength and the antiferromagnetic coupling strength between the second magnetic layer 5 and the third magnetic layer 9, the thickness of the second magnetic layer 5 is preferably 2-15 nm.

From the viewpoint of thermal stability characteristics, the thickness of the third magnetic layer 9 is preferably 10 nm or more. From the viewpoint of high recording density, the thickness of the third magnetic layer 9 is preferably 40 nm or less. This is because, if the thickness exceeds 40 nm, satisfactory recording and reproducing characteristics cannot be obtained.

Each magnetic layer (first to third magnetic layers 3, 5, and 9) may have a multilayer structure including a plurality of layers. When the magnetic layer has a multilayer structure, materials used for the first to third magnetic layers may be used for the layers constituting the multilayer structure.

In the present invention, in order to promote the epitaxial growth of the nonmagnetic undercoat layer 2, an orientation adjustment layer made of a metal material may be formed between the nonmagnetic substrate 1 and the nonmagnetic undercoat layer 2.

Examples of materials making the orientation adjustment layer include CoW-based alloys, CoMo-based alloys, CoTa-based alloys, CoNb-based alloys, NiP-based alloys, NiTa-based alloys, FeMo-based alloys, FeW-based alloys, ReW-based alloys, ReMo-based alloys, RuW-based alloys and RuMo-based alloys.

The alignment adjustment layer may be subjected to a surface treatment in which the surface is allowed to come into contact with oxygen and oxygen-containing gas such as air. From the viewpoint of the epitaxial growth of the non-magnetic undercoat layer 2, the thickness of the orientation adjustment layer is preferably in the range of 5 to 50 nm.

FIG. 3 shows an embodiment of a magnetic recording medium including an orientation adjustment layer of the present invention. The magnetic recording medium includes an orientation adjustment layer 10 between a nonmagnetic substrate 1 and a nonmagnetic undercoat layer 2 .

In addition, in order to improve the adhesive force between the nonmagnetic substrate 1 and the orientation adjustment layer 10 , an adhesive layer may be formed between the nonmagnetic substrate 1 and the orientation adjustment layer 10 .

The adhesive layer may be made of at least one of Cr, Ta, Ti, and W. The thickness of the adhesive layer is preferably in the range of 1 to 100 nm (more preferably in the range of 5 to 80 nm, most preferably in the range of 7 to 70 nm) from the viewpoint of adhesion and productivity.

FIG. 4 shows another embodiment of a magnetic recording medium including an adhesive layer of the present invention. The magnetic recording medium includes an adhesive layer 11 between the nonmagnetic substrate 1 and the orientation adjustment layer 10 .

In order to improve the epitaxial growth of the first magnetic layer 3 , a nonmagnetic intermediate layer may be formed between the nonmagnetic undercoat layer 2 and the first magnetic layer 3 . When the nonmagnetic interlayer is formed, the effect of improving magnetic characteristics (such as coercive force) and recording-reproduction characteristics (such as SNR) can be obtained.

The non-magnetic intermediate layer can be made of Co and Cr. When the nonmagnetic intermediate layer is made of a CoCr-based alloy, the Cr content is preferably in the range of 25 to 45 atomic % from the viewpoint of improving SNR. From the viewpoint of improving SNR, the thickness of the nonmagnetic intermediate layer is preferably in the range of 0.5 to 3 nm.

Fig. 5 shows yet another embodiment of the magnetic recording medium including the non-magnetic interlayer of the present invention. The magnetic recording medium includes a nonmagnetic intermediate layer 12 between the nonmagnetic undercoat layer 2 and the first magnetic layer 3 .

The protective layer 6 can be made of a material known as a protective layer, such as carbon and SiC.

The thickness of the protective layer 6 is preferably in the range of 1 to 10 nm from the viewpoint of space loss when increasing the recording density and the durability of the medium.

On the protective layer 6, a lubricating layer 7 made of a fluorine-containing lubricant such as perfluoropolyether may be formed as necessary.

The recording medium of the present invention is an AFC medium in which the magnetization directions of the plurality of magnetic layers provided above and below the nonmagnetic coupling layer can be adjusted to be opposite and parallel to each other.

In other words, in the magnetic recording medium of the present invention, the second magnetic layer 5 can be antiferromagnetically coupled with the first magnetic layer 3 . Furthermore, the third magnetic layer 9 may be antiferromagnetically coupled with the second magnetic layer 5 , and the second magnetic layer 5 may be antiferromagnetically coupled with the first magnetic layer 3 .

Hex (exchange coupling strength) or J (exchange linkage coefficient) can be used as an index representing the antiferromagnetic coupling strength.

Hex is preferably 500 (Oe) or more, and J is preferably 0.2 erg/cm ² or more.

And, 1 erg/cm ² =0.001 J/m ² , 1 Oe≈79.577475 A/m, and 1 emu/cc≈12.5664×10 ⁻⁴ Wb/m ² .

Hex is defined as the magnetic field strength from the center of the local hysteresis loop to 0 when the coercive magnetic field strength is measured and a local hysteresis loop is formed.

The larger Hex is, the stronger the magnetic coupling between the magnetic layers (provided above and below the non-magnetic coupling layer) is, and the more stable they are.

Figure 6 shows an example of a local hysteresis loop. Referring to FIG. 6, one method for forming local hysteresis loops is described.

First, increase the magnetic field strength from 0 (Oe) to the maximum measured magnetic field strength (for example, 10,000 (Oe)) (FIG. 6, step 1→2→3).

Subsequently, the magnetic field is reversed, and then the magnetic field strength is allowed to decrease from the maximum measured value (eg, 10,000 (Oe)). The magnetic field strength gradually decreases, and then the magnetic field strength drops suddenly, so that the magnetization lines form a curve. After that, the magnetic field strength is further decreased to a value (for example, -3,000(Oe)) that is 1,000(Oe) greater than the magnetic field strength at which the magnetic field strength suddenly starts to decrease again (Figure 6, step 4→5→6) . Subsequently, the magnetic field is reversed again, increasing the field strength from a value at which the field reversal occurs (e.g., -3,000(Oe)) to a maximum measured value (e.g., 10,000(Oe)) (Figure 6, step 7 →1→2→3). The hysteresis curve obtained through these steps is the local hysteresis loop.

J is calculated by the following formula:

J＝Hex×Ms ₁ ×t ₁

Wherein, Ms ₁ represents the saturation magnetization (emu/cc) of the first magnetic layer 3 , and t ₁ represents the thickness of the first magnetic layer 3 . Ms ₁ can be obtained by local hysteresis loops.

Next, an example of a method for manufacturing the magnetic recording medium of the present invention will be described.

A texturing process is performed on the surface of the non-magnetic substrate 1, if necessary. For the texturing process, mechanical texturing with abrasive belts may be employed.

The texturing process can be performed simultaneously with the shaking. The "oscillating" process refers to an operation of oscillating the abrasive tape in the radial direction of the nonmagnetic substrate 1 while the abrasive tape moves in the circumferential direction on the nonmagnetic substrate 1 . The oscillation speed is preferably 60 to 1,200 cycles/minute so that the surface of the non-magnetic substrate 1 is uniformly polished.

In addition to the mechanical texturing process using an abrasive belt, a texturing method using a fixed abrasive, a texturing method using a fixed grinding wheel, laser treatment, and the like may be employed.

The texturing process is preferably performed such that grooves having a line density of 7500 lines/mm or higher are formed on the surface of the non-magnetic substrate 1 .

When the rinsing of the non-magnetic substrate 1 is completed, the non-magnetic substrate 1 is placed in the chamber of the film forming apparatus. The nonmagnetic substrate 1 is heated to 100 to 400° C. as necessary.

By sputtering (for example, DC or RF magnetron sputtering), on the non-magnetic substrate 1, a non-magnetic primer layer 2, a first magnetic layer 3, a non-magnetic coupling layer 4, a second magnetic layer 5 (or non-magnetic undercoat layer 2, first magnetic layer 3, first non-magnetic coupling layer 4, second magnetic layer 5, second non-magnetic coupling layer 8 and third magnetic layer 9).

The following sputtering operating conditions can be employed to form these layers.

The non-magnetic substrate 1 is placed in a chamber, and the chamber is evacuated so that the degree of vacuum is in the range of 1×10 ^-4 to 1×10 ^-7 Pa. A sputtering gas (such as Ar) is injected into the chamber, and discharge is performed. The electric power to be supplied is preferably 0.2 to 2.0 kW. By controlling the discharge time and the electric power supplied, the thickness of the formed film can be adjusted.

Specifically, the magnetic recording medium of the present invention can be produced, for example, by the following process.

On the non-magnetic substrate 1, a non-magnetic undercoat layer 2 with a thickness of 3-15 nm is formed by using a sputtering target (such as Cr, Cr alloy, NiAl-based alloy or RuAl-based alloy).

Then, the first magnetic layer 3 is formed with a thickness of 0.5 to 5 nm using a CoCrZr-based alloy.

Subsequently, a sputtering target (such as Ru, Rh, Ir, Cr, Re, Ru-based alloy, Rh-based alloy, Ir-based alloy, Cr-based alloy or Re-based alloy) is used to form a thickness of 0.5 to 1.5 nm (more preferably 0.6 nm). ~1.0nm) non-magnetic coupling layer 4.

Subsequently, a second magnetic layer 5 with a thickness of 10 to 40 nm is formed using a sputtering target (such as a CoCrTa-based alloy, a CoCrPt-based alloy, a CoCrPtTa-based alloy, a CoCrPtB-based alloy, a CoCrPtBTa-based alloy, a CoCrPtBCu-based alloy, or a CoRuTa-based alloy).

Thereafter, protective layer 6 is produced by conventionally known methods (eg, sputtering, plasma CVD).

On the protective layer 6, if necessary, a lubricating layer 7 can be formed by a conventionally known method such as spin coating or dipping.

When the orientation adjustment layer 10 is formed between the nonmagnetic substrate 1 and the nonmagnetic undercoat layer 2 before the nonmagnetic undercoat layer 2 is manufactured, the orientation is formed using a sputtering target selected from materials constituting the orientation adjustment layer 10. Conditioning layer 10.

When forming the adhesive layer 11 between the nonmagnetic substrate 1 and the orientation adjusting layer 10 before manufacturing the orientation adjusting layer 10, the adhesive layer 11 may be formed using a sputtering target selected from materials constituting the adhesive layer 11 .

Since the magnetic recording medium includes the first magnetic layer made of a CoCrZr-based alloy, medium noise can be reduced.

This magnetic recording medium has a feature in which the CoCrZr-based alloy is used only as the first magnetic layer which is the layer positioned closest to the non-magnetic substrate among the plurality of magnetic layers.

For example, in the magnetic recording medium shown in FIG. 1, of the two magnetic layers, namely, the first magnetic layer 3 and the second magnetic layer 5, only the first magnetic layer 3 is made of a CoCrZr-based alloy. In the magnetic recording medium shown in FIG. 2, among the three magnetic layers, namely, the first magnetic layer 3, the second magnetic layer 5, and the third magnetic layer 9, only the first magnetic layer 3 is made of a CoCrZr-based alloy .

Therefore, medium noise can be reduced in the magnetic recording medium of the present invention. In contrast, in a magnetic recording medium including a magnetic layer made of a CoCrZr-based alloy other than the first magnetic layer, medium noise increases.

Since the magnetic recording medium is an AFC medium in which the magnetic layers are antiferromagnetically coupled, thermal stability is improved.

FIG. 7 shows an example magnetic recording and reproducing apparatus according to the present invention.

The magnetic recording and reproducing apparatus shown in FIG. 7 includes a magnetic recording medium 20, a medium driving part 21 for rotating the magnetic recording medium 20, a magnetic head 22 for recording and reproducing information on the magnetic recording medium 20, A magnetic head driving section 23 for moving the magnetic head 22 relative to the magnetic recording medium 20 , and a recording and reproduction signal processing system 24 .

The recording reproduction signal processing system 24 is configured so as to process data from the outside to transmit recording signals to the magnetic head 22 and to process reproduction signals from the magnetic head 22 to transmit data to the outside.

For the magnetic head 22, a magnetic head suitable for high recording density can be used, for example, a magnetic head including not only a magnetoresistive element (MR) based on the anisotropic magnetoresistance effect (AMR) as a reproducing element but also a giant magnetic A giant magnetoresistive element (GMR) of the resistive effect (GMR) is used as a reproducing element. Recording density can be improved by using GMR elements.

Since the magnetic recording and reproducing apparatus employs a magnetic recording medium including a first magnetic layer made of a CoCrZr-based alloy, medium noise can be reduced.

example

Next, the effects of the present invention will be explained with reference to examples.

Example 1

On the surface of a substrate made of Al (outer diameter: 95 mm, inner diameter: 25 mm, and thickness: 1.270 mm), a NiP film (thickness: 12 μm) was formed by electroless plating. Subsequently, the surface of the NiP film is textured to prepare a non-magnetic substrate with an average surface roughness (Ra) of 0.5 nm.

The prepared non-magnetic substrate was placed in a DC magnetron sputtering device (C3010, a product of ANELVA, Japan), and the chamber was evacuated to 2× ^10-7 Torr (2.7× ^10-5 Pa), and subsequently, the The non-magnetic substrate is heated to 250°C.

A non-magnetic undercoat layer is formed on a non-magnetic substrate. The nonmagnetic undercoat layer has a multilayer structure including a first layer made of Cr (thickness: 5 nm) and a second layer made of CrMo alloy (Cr: 80 atomic % and Mo: 20 atomic %) (thickness: 3nm), wherein the second layer is formed on the first layer.

A first magnetic layer (thickness: 2 nm) made of a CoCrZr alloy (Co: 75 atomic %, Cr: 20 atomic %, and Zr: 5 atomic %) was formed on the second layer of the nonmagnetic undercoat layer.

A non-magnetic coupling layer (thickness: 0.8 nm) made of Ru was formed on the first magnetic layer.

A second magnetic layer (thickness: 20 nm) made of a CoCrPtB alloy (Co: 60 atomic%, Cr: 22 atomic%, Pt: 12 atomic%, and B: 6 atomic%) was formed on the nonmagnetic coupling layer.

After that, a protective layer (thickness: 5 nm) made of carbon was formed on the second magnetic layer.

In forming each layer, Ar was used as a sputtering gas, and its gas pressure was adjusted to 3 mTorr.

Subsequently, a lubricant containing perfluoropolyether was applied to the surface of the protective layer to form a lubricant layer (thickness: 2 nm), thereby preparing a magnetic recording medium.

Example 2

A magnetic recording medium was prepared in the same manner as in Example 1 except that the first magnetic layer was made of a CoCrZr alloy (Co: 81 at%, Cr: 14 at%, and Zr: 5 at%).

Example 3

A magnetic recording medium was prepared in the same manner as in Example 1 except that the first magnetic layer was made of a CoCrZr alloy (Co: 79 at%, Cr: 16 at%, and Zr: 5 at%).

Example 4

A magnetic recording medium was prepared in the same manner as in Example 1 except that the first magnetic layer was made of a CoCrZr alloy (Co: 77 at%, Cr: 18 at%, and Zr: 5 at%).

Example 5

A magnetic recording medium was prepared in the same manner as in Example 1 except that the first magnetic layer was made of a CoCrZr alloy (Co: 73 at%, Cr: 22 at%, and Zr: 5 at%).

Example 6

A magnetic recording medium was prepared in the same manner as in Example 1 except that the first magnetic layer was made of a CoCrZr alloy (Co: 71 at%, Cr: 24 at%, and Zr: 5 at%).

Example 7

A magnetic recording medium was prepared in the same manner as in Example 1 except that the first magnetic layer was made of a CoCrZr alloy (Co: 79 at%, Cr: 20 at%, and Zr: 1 at%).

Example 8

A magnetic recording medium was prepared in the same manner as in Example 1, except that the first magnetic layer was made of a CoCrZr alloy (Co: 77 atomic%, Cr: 20 atomic%, and Zr: 3 atomic%).

Example 9

A magnetic recording medium was prepared in the same manner as in Example 1 except that the first magnetic layer was made of a CoCrZr alloy (Co: 73 at%, Cr: 20 at%, and Zr: 7 at%).

Example 10

A magnetic recording medium was prepared in the same manner as in Example 1 except that the first magnetic layer was made of a CoCrZr alloy (Co: 71 at%, Cr: 20 at%, and Zr: 9 at%).

Example 11

A magnetic recording medium was prepared in the same manner as in Example 1 except that the first magnetic layer was made of a CoCrZr alloy (Co: 69 at%, Cr: 20 at%, and Zr: 11 at%).

Example 12

A magnetic recording medium was prepared in the same manner as in Example 1, except that the first magnetic layer was made of a CoCrZrB alloy (Co: 73 at%, Cr: 20 at%, Zr: 5 at%, and B: 2 at%) .

Comparative example 1

A comparative magnetic recording medium was prepared in the same manner as in Example 1 except that the first magnetic layer was made of a CoCr alloy (Co: 80 atomic % and Cr: 20 atomic %).

Comparative example 2

A comparative magnetic recording medium was prepared in the same manner as in Example 1 except that the first magnetic layer was made of a CoCrTa alloy (Co: 75 at%, Cr: 20 at%, and Ta: 5 at%).

Comparative example 3

A comparative magnetic recording medium was prepared in the same manner as in Example 1 except that the second magnetic layer was made of a CoCrZr alloy (Co: 75 at%, Cr: 20 at%, and Zr: 5 at%).

Example 13

A non-magnetic substrate having a surface average roughness (Ra) of 0.3 nm was prepared by subjecting a glass substrate (outer diameter: 65 mm, inner diameter: 20 mm, and thickness: 0.635 mm) to a texturing process.

The prepared non-magnetic substrate was placed in a DC magnetron sputtering device (C3010, product of ANELVA, Japan), and the chamber was evacuated to 2×10 ^-7 Torr (2.7×10 ^-5 Pa).

On the nonmagnetic substrate, an orientation adjustment layer (thickness: 5 nm) made of a CoW alloy (Co: 50 atomic % and W: 50 atomic %) was formed, followed by heating to 250°C.

After that, the surface of the alignment adjusting layer was exposed to oxygen. The oxygen pressure and exposure time were controlled to be 0.05 Pa and 5 seconds, respectively.

A non-magnetic undercoat layer made of CrTiB alloy (Cr: 82 at%, Ti: 16 at%, and B: 2 at%) is formed on the orientation adjustment layer

A first magnetic layer (thickness: 2 nm) made of a CoCrZr alloy (Co: 81 atomic %, Cr: 14 atomic %, and Zr: 5 atomic %) was formed on the nonmagnetic undercoat layer.

A non-magnetic coupling layer (thickness: 0.8 nm) made of Ru was formed on the first magnetic layer.

A second magnetic layer (thickness: 20 nm) made of a CoCrPtB alloy (Co: 60 atomic%, Cr: 22 atomic%, Pt: 12 atomic%, and B: 6 atomic%) was formed on the nonmagnetic coupling layer.

After that, a protective layer (thickness: 5 nm) made of carbon was formed.

In forming each layer, Ar was used as a sputtering gas, and its gas pressure was adjusted to 3 mTorr.

Subsequently, a lubricant containing perfluoropolyether was applied to the surface of the protective layer to form a lubricant layer (thickness: 2 nm), thereby preparing a magnetic recording medium.

Example 14

A magnetic recording medium was prepared in the same manner as in Example 13 except that the first magnetic layer was made of a CoCrZr alloy (Co: 87 at%, Cr: 8 at%, and Zr: 5 at%).

Example 15

A magnetic recording medium was prepared in the same manner as in Example 13 except that the first magnetic layer was made of a CoCrZr alloy (Co: 85 at%, Cr: 10 at%, and Zr: 5 at%).

Example 16

A magnetic recording medium was prepared in the same manner as in Example 13 except that the first magnetic layer was made of a CoCrZr alloy (Co: 83 at%, Cr: 12 at%, and Zr: 5 at%).

Example 17

A magnetic recording medium was prepared in the same manner as in Example 13 except that the first magnetic layer was made of a CoCrZr alloy (Co: 79 at%, Cr: 16 at%, and Zr: 5 at%).

Example 18

A magnetic recording medium was prepared in the same manner as in Example 13 except that the first magnetic layer was made of a CoCrZr alloy (Co: 77 at%, Cr: 18 at%, and Zr: 5 at%).

Example 19

A magnetic recording medium was prepared in the same manner as in Example 13, except that the first magnetic layer was made of a CoCrZr alloy (Co: 85 atomic%, Cr: 14 atomic%, and Zr: 1 atomic%).

Example 20

A magnetic recording medium was prepared in the same manner as in Example 13 except that the first magnetic layer was made of a CoCrZr alloy (Co: 83 at%, Cr: 14 at%, and Zr: 3 at%).

Example 21

A magnetic recording medium was prepared in the same manner as in Example 13 except that the first magnetic layer was made of a CoCrZr alloy (Co: 79 at%, Cr: 14 at%, and Zr: 7 at%).

Example 22

A magnetic recording medium was prepared in the same manner as in Example 13 except that the first magnetic layer was made of a CoCrZr alloy (Co: 77 at%, Cr: 14 at%, and Zr: 9 at%).

Example 23

A magnetic recording medium was prepared in the same manner as in Example 13, except that the first magnetic layer was made of a CoCrZr alloy (Co: 75 atomic %, Cr: 14 atomic %, and Zr: 11 atomic %).

Comparative example 4

A comparative magnetic recording medium was prepared in the same manner as in Example 13 except that the first magnetic layer was made of a CoCr alloy (Co: 86 atomic % and Cr: 14 atomic %).

Comparative example 5

A comparative magnetic recording medium was prepared in the same manner as in Example 13 except that the first magnetic layer was made of a CoCrTa alloy (Co: 81 at%, Cr: 14 at%, and Ta: 5 at%).

Example 24

On the surface of a substrate made of Al (outer diameter: 95 mm, inner diameter: 25 mm, and thickness: 1.270 mm), a NiP film (thickness: 12 μm) was formed by electroless plating. Subsequently, the surface of the NiP-based alloy film is textured to prepare a non-magnetic substrate with an average surface roughness (Ra) of 0.5 nm.

The prepared non-magnetic substrate was placed in a DC magnetron sputtering device (C3010, a product of ANELVA, Japan), and the chamber was evacuated to 2× ^10-7 Torr (2.7× ^10-5 Pa), and subsequently, the The non-magnetic substrate is heated to 250°C.

A non-magnetic undercoat layer is formed on a non-magnetic substrate. The nonmagnetic undercoat layer has a multilayer structure including a first layer made of Cr (thickness: 5 nm) and a second layer made of CrMo alloy (Cr: 80 atomic % and Mo: 20 atomic %) (thickness: 3nm), wherein a second layer is formed over the first layer.

A first magnetic layer (thickness: 2 nm) made of a CoCrZr alloy (Co: 75 atomic %, Cr: 20 atomic %, and Zr: 5 atomic %) was formed on the second layer of the nonmagnetic undercoat layer.

A first non-magnetic coupling layer (thickness: 0.8 nm) made of Ru was formed on the first magnetic layer.

A second magnetic layer (thickness: 4 nm) made of a CoCrPtB alloy (Co: 69 atomic %, Cr: 22 atomic %, Pt: 5 atomic %, and B: 4 atomic %) was formed on the first nonmagnetic coupling layer .

A second nonmagnetic coupling layer (thickness: 0.8 nm) made of Ru was formed on the second magnetic layer.

A third magnetic layer (thickness: 15 nm) made of a CoCrPtB alloy (Co: 60 atomic %, Cr: 22 atomic %, Pt: 12 atomic %, and B: 6 atomic %) was formed on the second nonmagnetic coupling layer .

After that, a protective layer (thickness: 5 nm) made of carbon was formed.

In forming each layer, Ar was used as a sputtering gas, and its gas pressure was adjusted to 3 mTorr.

Subsequently, a lubricant containing perfluoropolyether was applied to the surface of the protective layer to form a lubricant layer (thickness: 2 nm), thereby preparing a magnetic recording medium.

Comparative example 6

A comparative magnetic recording medium was prepared in the same manner as in Example 24, except that the first magnetic layer was made of a CoCr alloy (Co: 80 atomic % and Cr: 20 atomic %).

Comparative example 7

A comparative magnetic recording medium was prepared in the same manner as in Example 24, except that the first magnetic layer was made of a CoCrTa alloy (Co: 75 atomic % and Cr: 20 atomic %, Ta: 5 atomic %).

Each of the magnetic recording media prepared in the above-mentioned examples and comparative examples was subjected to a glide test by using a glide tester in which the glide height was adjusted to 0.3 microinch (1 inch≈25.4 mm). A further investigation was conducted on the recording medium that passed the test in terms of recording and reproduction characteristics by using a read/write analyzer RWA 1632 (product of GUZIK, USA).

Recording and reproduction characteristics were studied in terms of electromagnetic conversion characteristics (Track Average Sum of Amplitudes (TAA), 50% Pulse Width (PW50), SNR, and Overwrite (OW)).

Recording and reproducing characteristics were evaluated using a composite thin-film magnetic recording head including a giant magnetoresistance (GMR) element as a readout section.

Noise was evaluated by measuring integrated noise from 1 MHz to a frequency corresponding to 500 kFCI generated when writing a pattern signal of 500 kFCI. The read output was adjusted to 250 kFCI and the SNR was calculated by the following formula: SNR = 20 x log (read output/integrated noise from 1 MHz to the frequency corresponding to 500 kFCI).

Coercive force (Hc) and squareness ratio (S ^* ) were determined using a Kerr effect magnetic characteristic analyzer (RO1900, product of Hitachi Electronics Engineering, Japan).

The results are shown in Tables 1-1 and 1-2.

Table 1-1 Composition of the first magnetic layer Composition of the second magnetic layer Composition of the third magnetic layer Coercivity (Oe) Square ratio (-) TAA(μV) OW(dB) PW50(ns) SNR(dB) Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Example 9 Example 10 Example 11 Example 12 Example 13 Example 14 Example 15 Example 16 Example 17 Example 18 Example 19 Example 20 Example 21 Example 22 Example 23 Example 24 75Co20Cr5Zr81Co14Cr5Zr79Co16Cr5Zr77Co18Cr5Zr73Co22Cr5Zr71Co24Cr5Zr79Co20Cr1Zr77Co20Cr3Zr73Co20Cr7Zr71Co20Cr9Zr69Co20Cr11Zr73Co20Cr5Zr2B81Co14Cr5Zr87Co8Cr5Zr85Co10Cr5Zr83Co12Cr5Zr79Co16Cr5Zr77Co18Cr5Zr85Co14Cr1Zr83Co14Cr3Zr79Co14Cr7Zr77Co14Cr9Zr75Co14Cr11Zr75Co20Cr5Zr 60Co22Cr12Pt6B60Co22Cr12Pt6B60Co22Cr12Pt6B60Co22Cr12Pt6B60Co22Cr12Pt6B60Co22Cr12Pt6B60Co22Cr12Pt6B60Co22Cr12Pt6B60Co22Cr12Pt6B60Co22Cr12Pt6B60Co22Cr12Pt6B60Co22Cr12Pt6B60Co22Cr12Pt6B60Co22Cr12Pt6B60Co22Cr12Pt6B60Co22Cr12Pt6B60Co22Cr12Pt6B60Co22Cr12Pt6B60Co22Cr12Pt6B60Co22Cr12Pt6B60Co22Cr12Pt6B60Co22Cr12Pt6B60Co22Cr12Pt6B69Co22Cr5Pt4B -----------------------60Co22Cr12Pt6B 4,3514,3254,2954,3354,3674,2714,2514,3254,3964,3574,3114,3524,3924,3114,3554,2954,3714,3814,2914,2884,3124,3624,2784,356 0.810.830.840.810.800.750.780.800.820.810.740.800.810.830.820.810.800.790.780.790.810.820.770.80 1,3541,2251,2491,3291,3851,3961,3021,3171,3681,3961,3921,3651,1969861,0361,1251,2561,2911,1121,1371,2191,2651,2911,351 37.539.239.038.137.137.538.437.936.636.237.537.639.641.040.539.938.637.539.838.937.837.437.235.8 9.429.219.269,379.529.749.589.499.499.559.769.459.309.129.189.259.379.459.349.379.409.519.639.41 18.518.718.718.418.417.518.118.718.618.217.618.718.418.318.418.418.418.217.918.518.418.217.618.1

Table 1-2 Composition of the first magnetic layer Composition of the second magnetic layer Composition of the third magnetic layer Coercivity (Oe) Square ratio (-) TAA(μV) OW(dB) PW50(ns) SNR(dB) Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Comparative Example 6 Comparative Example 7 80Co20Cr75Co20Cr5Ta75Co20Cr5Zr86Co14Cr81Co14Cr5Ta80Co20Cr75Co20Cr5Ta 60Co22Cr12Pt6B60Co22Cr12Pt6B75Co20Cr5Zr60Co22Cr12Pt6B60Co22Cr12Pt6B69Co22Cr5Pt4B69Co22Cr5Pt4B -----60Co22Cr12Pt6B60Co22Cr12Pt6B 4,2164,3191,1264,1964,2154,3114,322 0.760.790.810.740.770.750.74 1,2651,3411,3491,1851,2181,3011,321 37.237.942.538.939.638.238.4 9.629.6410.939.529.699.539.56 17.417.611.617.317.517.217.1

In Tables 1-1 and 1-2, for example, 75Co20Cr5Zr represents Co: 75 at%, Cr: 20 at%, and Zr: 5 at%.

In Examples 1 to 12 and 24, and Comparative Examples 1 to 3 and 6, an Al substrate was used as the nonmagnetic substrate. In Examples 13 to 23 and Comparative Examples 4 and 5, glass substrates were used as nonmagnetic substrates.

It can be clearly seen from Examples 1-6 that the magnetic recording medium has improved SNR when the Cr content in the CoCrZr-based alloy making up the first magnetic layer is in the range of 14-22 atomic %. On the contrary, when the Cr content is 24 atomic %, the magnetization is insufficient, and the SNR is lowered.

It is clear from Examples 1 and 7-11 that the magnetic recording medium has improved SNR when the Zr content in the CoCrZr-based alloy making up the first magnetic layer is in the range of 1-9 atomic %. Especially, when the Zr content is in the range of 3 to 7 atomic %, the SNR is the largest. When the Zr content is 11 atomic %, the magnetization is insufficient, and the SNR is lowered.

As is clear from Example 12, when B is added as an additive element to the CoCrZr-based alloy forming the first magnetic layer, the SNR is improved.

As can be clearly seen from Comparative Examples 1 and 2, when a CoCr-based alloy or a CoCrTa-based alloy is used as the first magnetic layer, the magnetic recording layer has an Poor SNR.

As is clear from Comparative Example 3, when a CoCrZr-based alloy is used as the second magnetic layer, the coercive force is significantly lowered, and the SNR is also significantly lowered.

From Examples 13-18, it can be clearly seen that the magnetic recording medium has improved SNR when the Cr content in the CoCrZr-based alloy making up the first magnetic layer is in the range of 8-18 atomic %.

As is clear from Examples 19-23, when the Zr content in the CoCrZr-based alloy making up the first magnetic layer is in the range of 1-9 atomic %, the magnetic recording medium has improved SNR. In particular, when the Zr content is in the range of 3 to 7 atomic %, the SNR is the largest. When the Zr content was 11 atomic %, there was no effect on magnetization, but the squareness ratio and SNR decreased.

As can be clearly seen from Comparative Examples 3 and 4, when a CoCr-based alloy or a CoCrTa-based alloy is used for the first magnetic layer, the magnetic recording layer has an Poor SNR.

The magnetic recording medium of Example 24 includes a first magnetic layer, a first nonmagnetic coupling layer, a second magnetic layer, a second nonmagnetic coupling layer, and a third magnetic layer (that is, the magnetic recording medium includes three magnetic layers and two non-magnetically coupled layers). In the magnetic recording medium having such a structure, when the first magnetic layer was made of a CoCrZr-based alloy, the magnetic recording medium had a more excellent SNR than those of Comparative Examples 6 and 7.

Industrial Applicability

Since the magnetic recording medium of the present invention includes the first magnetic layer made of a CoCrZr-based alloy, medium noise is reduced.

Claims (14)

1. A magnetic recording medium comprising at least a nonmagnetic undercoat layer, a first magnetic layer, a nonmagnetic coupling layer, a second magnetic layer, and a protective layer on a nonmagnetic substrate in the following order, wherein the second magnetic layer is antiferromagnetically coupled to the first magnetic layer; and The first magnetic layer is made of CoCrZr alloy. 2. A magnetic recording medium comprising at least a nonmagnetic undercoat layer, a first magnetic layer, a nonmagnetic coupling layer, a second magnetic layer, a nonmagnetic coupling layer, and a third magnetic layer on a nonmagnetic substrate in the following order , and the protective layer, wherein the third magnetic layer is antiferromagnetically coupled to the second magnetic layer; the second magnetic layer is antiferromagnetically coupled to the first magnetic layer; and The first magnetic layer is made of CoCrZr alloy. 3. The magnetic recording medium according to claim 1 or 2, wherein the first magnetic layer comprises 5 to 22 atomic % of Cr and 1 to 10 atomic % of Zr. 4. The magnetic recording medium according to any one of claims 1 to 3, wherein the thickness of the first magnetic layer is in the range of 0.5 to 10 nm. 5. The magnetic recording medium as claimed in any one of claims 1 to 4, wherein said non-magnetic coupling layer is selected from Ru, Rh, Ir, Cr, Re, Ru-based alloys, Rh-based alloys, Ir-based alloys , Cr-based alloy, and Re-based alloy; and the thickness of the non-magnetic coupling layer is in the range of 0.5-1.5 nm. 6. The magnetic recording medium according to any one of claims 1 to 5, wherein said nonmagnetic undercoat layer has a multilayer structure comprising a layer made of Cr or a layer made of a Cr-based alloy, said The Cr-based alloy includes Cr and at least one selected from Ti, Mo, Al, Ta, W, Ni, B, Si and V. 7. The magnetic recording medium as claimed in any one of claims 1 to 5, wherein said non-magnetic undercoat layer has a multilayer structure, comprising a layer containing one of NiAl-based alloy, RuAl-based alloy, and Cr-based alloy. layer; wherein the Cr-based alloy includes Cr and one or two or more of Ti, Mo, Al, Ta, W, Ni, B, Si and V. 8. The magnetic recording medium according to any one of claims 1 to 7, wherein the nonmagnetic substrate is one of a glass substrate and a silicon substrate. 9. The magnetic recording medium according to any one of claims 1 to 8, wherein said non-magnetic substrate comprises a substrate made of one of Al, Al-based alloy, glass, and silicon; On the bottom, a film containing one of NiP or a NiP alloy is formed. 10. The magnetic recording medium according to any one of claims 1 to 9, wherein the second magnetic layer is made of at least one of a CoCrTa-based alloy, a CoCrPtTa-based alloy, a CoCrPtB-based alloy, and a CoCrPtBM-based alloy (wherein , M represents at least one of Ta and Cu). 11. The magnetic recording medium according to any one of claims 2 to 9, wherein the second magnetic layer and the third magnetic layer are made of a CoCrTa-based alloy, a CoCrPtTa-based alloy, a CoCrPtB-based alloy, and a CoCrPtBM-based alloy. Made of at least one (where M represents at least one of Ta and Cu). 12. A method of manufacturing a magnetic recording medium comprising at least a nonmagnetic undercoat layer, a first magnetic layer, a nonmagnetic coupling layer, a second magnetic layer, and a protective layer on a nonmagnetic substrate in the following order ; wherein the second magnetic layer is antiferromagnetically coupled to the first magnetic layer, wherein said method comprises the step wherein said first magnetic layer is made of a CoCrZr alloy. 13. A method of manufacturing a magnetic recording medium comprising at least a nonmagnetic undercoat layer, a first magnetic layer, a nonmagnetic coupling layer, a second magnetic layer, a nonmagnetic a coupling layer, a third magnetic layer, and a protective layer; the third magnetic layer is antiferromagnetically coupled to the second magnetic layer; and the second magnetic layer is antiferromagnetically coupled to the first magnetic layer, wherein said method comprises the step wherein said first magnetic layer is made of a CoCrZr alloy. 14. A magnetic recording and reproducing apparatus comprising the magnetic recording medium as claimed in any one of claims 1 to 11, and a magnetic head for recording information in the magnetic recording medium and reproducing information from the magnetic recording medium .

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