CN100414611C - Magnetic recording medium and magnetic recording and reproducing device - Google Patents

Abstract

A magnetic recording medium includes an orientation adjusting layer, a nonmagnetic under layer, a nonmagnetic intermediate layer, a magnetic layer and a protective layer sequentially stacked on a nonmagnetic substrate provided on a first surface thereof with a texture streak and used for a magnetic disc. The nonmagnetic under layer contains at least a layer formed of a Cr-Mn-based alloy and possesses magnetic anisotropy having an axis of easy magnetization in a circumferential direction thereof. A magnetic recording and reproducing device includes the magnetic recording medium and a magnetic head for enabling information to be recorded in and reproduced from the magnetic recording medium.

Description

magnetic recording medium

Cross References to Related Applications

This application is an application filed under 35 U.S.C. §111(a) and is entitled, respectively, to provisional application No. 60/604489, filed August 26, 2004, under 35 U.S.C. § 119(e)(1) and under 35U .S.C. §111(b) filing date of Japanese Application No. 2004-236454 filed August 16, 2004.

technical field

The present invention relates to a magnetic recording medium having an orientation adjustment layer, a nonmagnetic underlayer, a nonmagnetic intermediate layer, a magnetic layer and a protective layer stacked in this order on a magnetic substrate provided on its first surface with Texture streak and is used for a magnetic disk, and relates to a magnetic recording and reproducing apparatus for recording and reproducing magnetic signals on the magnetic recording medium.

Background technique

The recording density of a hard disk drive (HDD), which is currently a magnetic recording and reproducing device, is increasing at a rate of 60% per year. This trend is said to continue in the future. As a consequence of this trend, research on magnetic recording heads and research on magnetic recording media suitable for high recording densities has been advancing.

Magnetic recording media used in hard disk drives need to follow this trend toward higher recording densities, and thus enhance coercivity and enhance signal-to-noise ratio (SNR).

For a magnetic recording medium to be used in the hard disk drive, such a structure in which a metal film is deposited on a substrate suitable for a magnetic recording medium by a sputtering process is currently dominant. As substrates suitable for magnetic recording media, aluminum substrates and glass substrates are widely used. The aluminum substrate was obtained by performing electroless plating on an Al-Mg alloy substrate ground to a mirror finish to form a Ni-P-based alloy layer with a thickness of about 10 μm, and further grinding this layer. The surface is mirror polished. Various types of glass substrates are known, such as amorphous glass and crystallized glass. Both glass substrates were ground to a mirror finish before use.

The magnetic recording medium commonly used in hard disk drives at present has such a structure: it has a non-magnetic liner layer (for example, made of Cr, Cr-based alloy, Ni-Al-based alloy) stacked on a non-magnetic substrate in sequence, a non-magnetic intermediate layer (for example, made of Co-Cr base or Co-Cr-Ta type alloy), magnetic layer (for example, made of Co-Cr-Pt-Ta base or Co-Cr-Pt-B type alloy), and a protective film (for example, made of carbon), and has a lubricating oil film made of liquid lubricating oil formed thereon.

In order to enhance the coercivity of magnetic recording media, several methods can be employed. For an alloy-based magnetic recording medium in which Co is the main component of the magnetic layer, for example, a method of adding Pt has been proven to be effective. A large number of reports have been published on this method. In addition, it has been proposed to use CrMn-based alloys as non-magnetic underlayers (see US Patent No. 5,993,956).

Regarding the static magnetostatic properties of magnetic recording media, it is effective to impart magnetic anisotropy having an easy axis of magnetization in the circumferential direction and to strengthen this property, as well as to enhance the coercive force while enhancing the recording properties of the medium and homogenizing the characteristics method is also effective. Therefore, at present, as is generally known, a magnetic recording medium using a substrate (otherwise called an aluminum substrate) obtained by electroplating an aluminum alloy with a Ni-P-based alloy layer passes through the surface of the Ni-P-based alloy in the circumferential direction Texturing of mechanically scribed microgrooves can exhibit magnetic anisotropy with an easy axis of magnetization in the circumferential direction (see IEEE Transon Mag. Vol. Mag-22, No. 5 (1986), 379 and Journal of Japan Applied Magnetism Society , Vol.17, No.5(1993)784).

As a non-magnetic substrate, such as a glass substrate, it has strong rigidity against impact and also has excellent flatness, so it can certainly be considered as a non-magnetic substrate suitable for high recording density. When magnetic anisotropy in the circumferential direction is imparted to a magnetic recording medium using glass as a nonmagnetic substrate, superior recording and reproducing performance can be expected.

Several methods of forming textures on glass substrates by subjecting them to texturing are known. In order to form a fine and uniform texture, an idea has been proposed to use a fabric tape comprising a polishing powder suspension containing a solution having hydroxyl groups and plastic fibers (see Japanese Patent No. 3117438).

In addition, in order to form a fine and uniform texture, someone proposed an idea: use diamond polishing powder and _CeO2 polishing powder at the same time.

However, it is difficult to impart completely satisfactory magnetic anisotropy in the circumferential direction to a glass substrate only by forming texture therein. Therefore, in order to impart magnetic anisotropy along the circumferential direction to a glass substrate formed with a linear texture on its first surface, someone has proposed the idea of forming a precoat by a sputtering process (see JP-A HEI 4-205916) , forming an amorphous layer containing at least Ni and P (see JP-A 2001-209927), and forming a direction adjustment layer of a Co-W-based alloy or a Co-Mo-based alloy (see JP-A 2004-86936).

As described above, several methods of imparting magnetic anisotropy to glass substrates on which textures are formed have been proposed. However, in general, the degree of anisotropy is smaller than in the case of using an aluminum substrate. The anisotropy needs to be further enhanced not only when a glass substrate is used but also when an aluminum substrate is used.

The present invention has been made in view of the above-mentioned state of affairs, and an object thereof is to provide a magnetic recording medium and a magnetic recording and reproducing apparatus rich in magnetic anisotropy suitable for high-density recording and having excellent recording performance.

Contents of the invention

In order to achieve the above-mentioned purpose, the first aspect of the present invention provides a magnetic recording medium, which includes a direction adjustment layer, a non-magnetic underlayer, a non-magnetic intermediate layer, a magnetic layer and a protective layer stacked on a non-magnetic substrate in sequence. layer, the nonmagnetic substrate provided with a texture on its first surface and used for a magnetic disk, wherein the nonmagnetic underlayer contains at least one layer formed of a Cr-Mn based alloy and has an easy axis of magnetization along its circumferential direction magnetic anisotropy.

In a second aspect including the first aspect of the present invention, the magnetic anisotropy in the amount of residual magnetization has an index greater than or equal to 1.3, the index being the amount of residual magnetization in the circumferential direction divided by the amount in the radial direction residual magnetization.

In a third aspect including the first or second aspect of the present invention, the Cr—Mn-based alloy layer forming at least a part of the nonmagnetic underlayer has a Mn content in the range of 1 to 60 at%.

In a fourth aspect including the first or second aspect of the present invention, the Cr—Mn-based alloy layer forming at least a part of the nonmagnetic underlayer has a Mn content in the range of 5 to 40 at%.

In a fifth aspect including any one of the first to fourth aspects of the present invention, the nonmagnetic underlayer has at least one stacked structure consisting of a Cr-Mn-based alloy layer and a Cr-Mo-based alloy layer formed thereon. layer composition.

In a sixth aspect including any one of the first to fourth aspects of the present invention, the nonmagnetic underlayer has at least one stacked structure consisting of a Cr-Mn-based alloy layer and a Cr-Ti-based alloy layer formed thereon. layer composition.

In a seventh aspect including any one of the first to sixth aspects of the present invention, the nonmagnetic underlayer is formed of amorphous glass or crystallized glass.

In an eighth aspect including any one of the first to sixth aspects of the present invention, the nonmagnetic underlayer is formed of single crystal Si or polycrystalline Si.

In a ninth aspect including any one of the first to eighth aspects of the present invention, the texture on the nonmagnetic substrate for magnetic disk has a linear density of 750 lines/mm or more.

In a tenth aspect including any one of the first to ninth aspects of the present invention, the direction adjustment layer is formed of at least one layer of alloy, and the at least one layer of alloy is made of Co-W type alloy, Co-Mo type alloy , Co-Ta-based alloys, Co-Nb-based alloys, Ni-Ta-based alloys, Ni-Nb-based alloys, Fe-W-based alloys, Fe-Mo-based alloys, and Fe-Nb-based alloys.

In an eleventh aspect including any one of the first to tenth aspects of the present invention, the nonmagnetic intermediate layer is formed of at least one layer of alloy, and the at least one layer of alloy is made of Co-Cr-based alloys, Co-Cr - selected from the group consisting of Ta-based alloys, Co-Cr-Ru-based alloys, Co-Cr-Zr-based alloys and Co-Cr-Pt-based alloys.

In a twelfth aspect including any one of the first to eleventh aspects of the present invention, the nonmagnetic intermediate layer has a stack structure consisting of a layer of at least one alloy and a layer formed thereon Ru or Ru alloy, the at least one alloy is from Co-Cr alloys, Co-Cr-Ta alloys, Co-Cr-Ru alloys, Co-Cr-Zr alloys and Co-Cr-Pt alloys selected from the group consisting of alloys.

In a thirteenth aspect including any one of the first to twelfth aspects of the present invention, the magnetic layer contains a material selected from Co-Cr-Pt-based alloys, Co-Cr-Pt-Ta-based alloys, Co-Cr- One or more alloys selected from the group consisting of Pt-B alloys, Co-Cr-Pt-B-Ta alloys and Co-Cr-Pt-B-Cu alloys.

In a fourteenth aspect including any one of the first to thirteenth aspects of the present invention, the first surface of the direction adjusting layer is exposed to ambient gas containing oxygen equal to or greater than 5×10 ^-4 Pa processing.

A fifteenth aspect of the present invention provides a magnetic recording and reproducing apparatus including the magnetic recording medium described in any one of the first to fourteenth aspects of the present invention and capable of recording information on the magnetic recording medium and from The magnetic head reproduces the magnetic recording medium.

The magnetic recording medium of the present invention includes a direction adjustment layer, a non-magnetic underlayer, a non-magnetic intermediate layer, a magnetic layer and a protective layer, which are sequentially stacked on a non-magnetic substrate provided on its first surface with textured and used for magnetic disks, wherein the non-magnetic underlayer is formed in a structure including at least one layer of Cr-Mn-based alloy. This specific configuration leads to the enhancement of the characteristics of the magnetic recording medium exhibiting strong magnetic anisotropy with the circumferential direction as the easy axis of magnetization. As a result, a magnetic recording medium and a magnetic recording and reproducing apparatus suitably high in recording density, rich in magnetic anisotropy and excellent in recording performance can be obtained.

The above and other objects, features and advantages of the present invention will become apparent to those skilled in the art from the description given herein when taken in conjunction with the following drawings.

Description of drawings

FIG. 1 is a schematic diagram for showing a preferred embodiment of the magnetic recording medium of the present invention.

Detailed ways

The magnetic recording medium of the present invention is structured to have a direction adjustment layer, a non-magnetic underlayer, a non-magnetic intermediate layer, a magnetic layer and a protective layer, which are sequentially stacked on a non-magnetic substrate, and the first surface of the non-magnetic substrate is provided with Textured and used for a magnetic disk, the magnetic recording medium is characterized in that the non-magnetic underlayer is provided with a structure including at least a layer formed of a Cr-Mn-based alloy and having a magnetic axis with the circumferential direction as an easy magnetization axis. Anisotropy.

1 is a schematic view showing an embodiment of the magnetic recording medium of the present invention, wherein reference numeral 1 denotes a nonmagnetic substrate, 2 denotes an orientation adjustment layer, 3 denotes a nonmagnetic backing layer, 4 denotes a nonmagnetic intermediate layer, and 5 denotes a magnetic layer and 6 denotes a protective layer. The respective layers 1 to 6 are not necessarily limited to a single-layer structure, and may alternatively have a stacked structure formed of multiple layers.

As the non-magnetic substrate 1, a substrate formed of a non-magnetic metal obtained by electroplating an aluminum alloy with a Ni-P-based alloy layer, such as the aforementioned aluminum substrate, and a substrate formed of a non-magnetic, non-metallic material can be used. substrate, such as amorphous glass or crystallized glass, or single crystal Si or polycrystalline Si. As the amorphous glass, general-purpose soda lime glass, aluminoborosilicate glass, and aluminosilicate glass can be used. Then, as crystallized glass, lithium-based crystallized glass can be used. Among the other glasses listed above, the use of an amorphous glass with uniform solid state properties, such as hardness, is advantageous in subjecting a given first surface to a uniform texturing.

The first surface of the non-magnetic substrate 1 is such that a texture can be formed thereon, for example, using a packing tape using a non-volatile polishing powder, or by a texture treatment using a free polishing powder. The stripes formed on the first surface preferably extend in the circumferential direction of the substrate. Said substrate whose first surface has striations has an average surface roughness Ra in the range of 0.05 to 1 nm, preferably in the range of 0.1 to 0.5 nm.

If the average surface roughness Ra is less than 0.05 nm, this deficiency will cause the substrate to be too flat and reduce the effect of increasing the magnetic anisotropy of the magnetic layer 5 . On the contrary, if the average surface roughness Ra exceeds 1 nm, this excess will cause deterioration of the flatness of the medium surface and make it difficult to lower the flying height of the magnetic head during recording and reproducing processes.

The linear density of the texture is preferably 7500 lines/mm or more. The linear density is determined in the radial direction of the non-magnetic substrate 1 . The linear density is specified to be 7500 lines/mm or more because the effect of stripes is reflected by magnetism (eg, effect of enhancing diamagnetic force) and recording and reproducing performance (eg, effect of enhancing SNR). When the linear density is increased to 20,000 lines/mm or more, the above-mentioned effects are significantly increased.

For example, the stripes are preferably formed by packaging tape using non-volatile polishing powder, or by mechanical texturing using free polishing powder.

The direction adjustment layer 2 is used to correct the crystal orientation of the non-magnetic underlayer 3 formed on its first surface, adjust the crystal orientation of the non-magnetic intermediate layer 4 and the magnetic layer 5 further formed thereon, and strengthen the magnetic layer 5 along the circumferential direction. magnetic anisotropy. The direction adjusting layer 2 not only adjusts crystal orientation but also performs a function of finely refining the crystal grains in the nonmagnetic underlayer 3 , nonmagnetic intermediate layer 4 and magnetic layer 5 .

Although the material surrounding the direction adjustment layer 2 is not particularly limited, this layer is preferably made of Co-W-based alloys, Co-Mo-based alloys, Co-Ta-based alloys, Co-Nb-based alloys, Ni-Ta At least one alloy selected from the group consisting of Fe-Nb-based alloys, Ni-Nb-based alloys, Fe-W-based alloys, Fe-Mo-based alloys, and Fe-Nb-based alloys. It is considered that the use of an alloy containing an Fe ₇ W ₆ structure can increase the magnetic anisotropy of the magnetic film in the circumferential direction.

The direction adjustment layer 2 can introduce elements with auxiliary effects in it. As a specific example of the element that can be introduced, Ti, V, Cr, Mn, Zr, Hf, Ru, B, Al, Si, and P can be introduced. The total content of added elements is preferably 20 at% or less. If the total content exceeds 20 at%, this excess will lead to deterioration of the aforementioned effect of the direction adjusting layer. The lower limit of the total content is 0.1 at%. If the total content is less than 0.1 at%, the deficiency will lead to ineffectiveness of the effect of the added elements.

The direction adjusting layer 2 preferably has a thickness in the range of 1 to 30 nm. If the thickness of the direction adjusting layer 2 is less than 1 nm, this deficiency will cause the non-magnetic underlayer 3 not to obtain sufficient crystal orientation and deteriorate its coercive force. If the thickness of the direction adjusting layer exceeds 30 nm, this excess will lead to deterioration of the magnetic anisotropy of the magnetic film in the circumferential direction. In order to enhance the magnetic anisotropy of the magnetic film in the circumferential direction, the thickness of the direction adjusting film is preferably in the range of 2 to 10 nm.

It is advantageous to form, between the orientation adjusting layer 2 and the nonmagnetic substrate 1, a layer containing Ti, Cr, etc. as a main component in order to enhance the adhesion. Although the material for the layer thus interposed is not particularly limited, Ti, Cr, Cr-Ti-based alloys, Cr-Mo-based alloys, and Cr-Ta-based alloys can be employed. In this alloy system, the content of the second element is preferably in the range of 10 to 60 at%.

After forming the orientation adjusting layer 2, it is advantageous to oxidize its first surface by exposing this layer to an oxygen atmosphere. The oxygen atmosphere used for this purpose is preferably an atmosphere containing 5 x 10 ^-4 Pa or more of oxygen. The gas used in this exposure can be used while it remains in contact with water. The duration of this exposure is preferably in the range of 0.5 to 15 seconds. For example, the orientation adjusting film is preferably taken out of the chamber and exposed to the surrounding atmosphere or an oxygen atmosphere as soon as it is formed. In addition, it is also advantageous to keep the freshly formed film out of the chamber, to introduce ambient air or oxygen into the chamber and to expose the film thereto. The method of carrying out the exposure inside the chamber proves to be particularly advantageous because it avoids the complicated step of having to take the film out of the vacuum chamber and enables the formation of the film within a process involving the formation of the non-magnetic underlayer 3 and the magnetic layer 5. completed in a continuous film-forming sequence. In this case, the atmosphere preferably includes 5 x 10 ^-4 Pa or more of oxygen in a limit vacuum of 1 x 10 ^-6 Pa or less. Incidentally, during the exposure to oxygen, the upper limit of the oxygen pressure is preferably 5 x 10 ^-2 Pa or less, although the exposure may be performed under air pressure.

The non-magnetic underlayer 3 has a structure including at least a Cr—Mn-based alloy layer. The Mn content in the Cr-Mn type alloy is preferably in the range of 1 to 60 at%, and more preferably in the range of 5 to 40 at%, where a body centered cubic structure (BCC structure) can be obtained. If the content is less than 1 at%, this deficiency will not bring about a significant effect of enhancing the magnetic anisotropy. On the contrary, if the content exceeds 60 at%, this excess will lead to a decrease in the ratio of the BCC structure and deterioration of the coercive force. In order to increase the lattice constant of the Cr-Mn alloy layer, take the introduction of Mo, W, V, Ti, etc. to increase the lattice constant of the Cr-Mn alloy layer and make the lattice constant of the alloy comparable to that of the nonmagnetic intermediate layer 4 Measures adapted to the lattice constant of the Co alloy in the magnetic layer 5 have proven to be advantageous. Addition of B is advantageous from the viewpoint of carrying out refinement of the crystal of the magnetic recording medium and enhancement of SNR performance.

The crystal orientation of the Cr-Mn based alloy layer of the non-magnetic underlayer 3 is preferably such that the (100) crystal plane is the preferred crystal plane for orientation. As a result, since the crystal orientation of the Co alloy of the magnetic layer 5 formed on the nonmagnetic backing layer 3 is strongly indicated (11.0), this selection brings about the effect of enhancing magnetic properties such as coercive force, and improves recording and reproduction characteristics, for example, improved SNR.

Incidentally, the symbol "·" in the representation of the crystal plane represents an abbreviated form of the Miller Bravais index representing the crystal plane. Specifically, in expressing crystal planes, in a hexagonal system such as Co, four indices (hkil) are generally used. Among these indices, the index "i" is defined as i=-(h+k). In abbreviated form, this "i" part is represented as (hk·l).

It is preferable to employ the non-magnetic underlayer 3 so as to obtain a stacked structure comprising at least a Cr-Mn-based alloy layer and a Cr-Mo-based alloy layer formed thereon. In this stacked structure, the Cr—Ti alloy layer, Cr—W alloy layer or Cr—V alloy layer can be used instead of the Cr—Mo alloy layer.

In order to enhance the matching state of the lattice constant of the non-magnetic intermediate layer 4 and the lattice constant of the magnetic layer 5, it is preferable to form a layer composed of Cr-Mo alloy layer, Cr - at least one layer selected from the group consisting of Ti-based alloy layer, Cr-W-based alloy layer and Cr-V-based alloy layer. As a result, this improved lattice matching brings about the effect of enhancing magnetic characteristics such as coercive force and enhancing recording and reproducing performance such as SNR, because the Co The crystal orientation of the alloy is more strongly indicative of (11·0).

Although the material used for the nonmagnetic intermediate layer 4 is not particularly limited, a Co alloy having Co as a main component and exhibiting a hexagonal close-packed structure (HCP structure) is preferable. The material preferably contains materials selected from the group consisting of, for example, Co-Cr-based alloys, Co-Cr-Ta-based alloys, Co-Cr-Ru-based alloys, Co-Cr-Zr-based alloys, and Co-Cr-Pt alloys. an alloy. When selecting a Co-Cr type alloy, from the viewpoint of enhancing SNR, the Cr content is preferably in the range of 25 to 45 at%. Addition of B proved to be advantageous from the viewpoint of realizing refined crystal of the magnetic recording medium and enhancing SNR performance. From the viewpoint of enhancing SNR, the thickness of the nonmagnetic intermediate layer 4 is preferably in the range of 0.5 to 3 nm.

It is more favorable to form a nonmagnetic alloy layer composed of Ru or composed of Ru as a main component on the nonmagnetic Co alloy layer. This stacking results in enhanced coercivity.

The magnetic layer 5 is preferably made of a material which constitutes a Co alloy with Co as its main component, which has a very satisfactory matching with, for example, the (100) crystal plane of the non-magnetic intermediate layer 4 lying directly below. lattice, and exhibits the HCP structure. It preferably comprises components selected from, for example, Co-Cr-Ta types, Co-Cr-Pt types, Co-Cr-Pt-Ta types, Co-Cr-Pt-B-Ta types and Co-Cr-Pt-B-Cu types Any alloy selected from the group consisting of alloys.

For example, Co-Cr-Pt-based alloys, from the viewpoint of improving SNR, the content of Cr is preferably in the range of 8 to 28 at%, and the content of Pt is preferably in the range of 8 to 18 at%.

For example, Co-Cr-Pt-B alloys, from the perspective of improving SNR, the content of Cr is preferably in the range of 8 to 28 at%, the content of Pt is preferably in the range of 8 to 18 at%, and the content of B is preferably in the range of 1 to 28 at%. 20at% range.

For example, Co-Cr-Pt-B-Ta alloys, from the perspective of improving SNR, the content of Cr is preferably in the range of 8 to 25 at%, the content of Pt is preferably in the range of 8 to 18 at%, and the content of B is in the range of 1 to the range of 20at%, while the Ta content is in the range of 1 to 4at%.

For example, Co-Cr-Pt-B-Cu alloys, from the perspective of improving SNR, the content of Cr is preferably in the range of 8 to 28 at%, the content of Pt is preferably in the range of 8 to 18 at%, and the content of B is in the range of 1 to the range of 20 at%, while the Cu content is in the range of 1 to 8 at%.

From the viewpoint of thermal fluctuation, the thickness of the magnetic layer 5 does not pose a problem as long as it is greater than or equal to 10 nm. However, it is preferably less than or equal to 30 nm from the viewpoint of requiring a high recording density. If the thickness exceeds 30 nm, the excess will lead to an increase in the grain diameter of the magnetic layer 5 and will cause this layer to fail to obtain satisfactory recording and reproducing performance. The magnetic layer 5 may be formed in a multilayer structure, and the material therein may be an appropriate combination of various materials selected from the above group.

The protective layer 6 may be made of any one of known materials such as simple substances of carbon, SiC, and SiN, and materials having these simple substances as their main components. The thickness of the protective layer is preferably in the range of 1 to 10 nm from the viewpoint of reducing magnetic spacing in the case where the magnetic recording medium is used at a high recording density and ensuring durability. The magnetic gap refers to the distance between the read-write device of the magnetic head and the magnetic layer 5 . Electromagnetic conversion performance is correspondingly enhanced when the magnetic spacing is narrowed. Incidentally, the protective layer constitutes a factor for widening the magnetic gap because it is interposed between the read-write device of the magnetic head and the magnetic layer 5 .

The protective layer 6 may optionally be covered by a lubricating layer formed of a fluorine-based lubricant such as perfluoropolyether.

In the magnetic layer 5 of the magnetic recording medium of the present invention, when the index of the magnetic anisotropy of the residual magnetization (the residual magnetization in the circumferential direction/the residual magnetization in the radial direction) is greater than or equal to 1.3, preferably greater than or equal to 1.5, Effects of enhancing magnetic properties such as diamagnetic force and effects of enhancing recording and reproducing performance such as SNR and half power width (PW50) such as isolated inversion signals can be obtained. The index of magnetic anisotropy can be measured with a sample vibration magnetometer (SVM).

An example of the method of production realized by the present invention is now described.

As the nonmagnetic substrate 1, a substrate formed of a nonmagnetic metal obtained by electroplating an aluminum alloy with a Ni-P alloy layer or a nonmagnetic substrate made of amorphous glass or crystallized glass, or single crystal Si or polycrystalline Si is used. Substrates formed of non-metallic materials. As the amorphous glass, general-purpose soda lime glass, aluminoborosilicate glass, and aluminosilicate glass are usable. As the crystallized glass, lithium-based crystallized glass can be used. Among the other glasses mentioned above, the use of an amorphous glass having uniform solid state properties, including hardness, is particularly advantageous because it enables a given first surface to be uniformly textured.

The average surface roughness Ra of the non-magnetic substrate 1 is less than or equal to 2 nm, preferably less than or equal to 1 nm.

The minute wave (Minute wave, Wa) on the first surface is preferably less than or equal to 0.3 nm (more preferably less than or equal to 0.25 nm). For the stability of the flight of the magnetic head, it is advantageous to use a substrate having an average surface roughness Ra of less than or equal to 10 nm in either or both of the chamfered part and the lateral part of the end face of the substrate (preferably less than or equal to 9.5nm). Micro waviness (Wa) can be determined as an average surface roughness measured using a surface roughness tester P-12 (manufactured by KLM-Tencor K.K.) within a measurement range of 80 μm.

Initially, the first surface of the non-magnetic substrate 1 is textured to form stripes with a linear density greater than or equal to 7500/mm on the first surface. The first surface of, for example, a glass substrate is textured in the circumferential direction by mechanical treatment (sometimes referred to as "mechanical texturing") with non-volatile polishing powder and/or free polishing powder to form a textured surface on the front surface. Textures with a linear density greater than or equal to 7500 lines/mm. The texturing is accomplished, for example, by pressing the abrasive tape against the first surface of the substrate until intimate contact, feeding an abrasive slurry containing polishing powder into the interface between the substrate and the abrasive tape, and rotating the substrate and simultaneously Feed into the grinding belt. The rotation of the substrate can be done at a speed of 200 to 1000 rpm. The feed rate of the milling slurry can be in the range of 10 to 100 ml/min. The feed speed of the abrasive belt can be in the range of 1.5 to 150 mm/min. The D90 particle diameter (the size of the particle diameter formed when the cumulative mass is equal to 90% by mass) of the polishing powder contained in the grinding slurry may be in the range of 0.05 to 0.3 μm. The pressure exerted on the belt may be in the range of 1 to 15 kgf (9.8 to 147N). These conditions are preferably set so as to ensure the formation of textures with a linear density of 7,500 or more lines/mm (more preferably, 20,000 or more lines/mm).

)范围内并且优选在0.1到0.5nm(1到5

)范围内。The average surface roughness Ra of the textured glass substrate 1 formed on its first surface is 0.05 to 1 nm (0.5 to 10

) range and preferably in the range of 0.1 to 0.5 nm (1 to 5

) range.

This texturing can be performed in the presence of oscillations. The term "oscillating" as used herein refers to an operation of keeping the belt in motion in the circumferential direction of the substrate while shaking the belt in the radial direction of the substrate. Conditions for this oscillation are preferably between 60 and 1200 oscillations per minute.

As a way of implementing this texture processing, a method including forming a texture having a linear density of 7500 lines/mm or more can be used. In addition to the above-mentioned method by mechanical texture, a method using non-volatile polishing powder, a method using a fixed grindstone, and a method by laser treatment are available.

As a method of forming the film, a general sputtering method can be used. Conditions for such sputtering are determined as follows, for example. The chamber used for the forming process is evacuated until the degree of vacuum reaches a level in the range of 10 ⁻⁴ to 10 ⁻⁷ Pa. The non-magnetic substrate 1 whose first surface was textured was placed in the chamber and Ar gas as a sputtering gas was introduced into the chamber to be discharged therein to achieve film formation by sputtering. Here, the supplied power is in the range of 0.05 to 2.0 kW. A desired film thickness can be obtained by adjusting the duration of the discharge and the supplied power.

Crystal orientation in the nonmagnetic underlayer 3 and magnetic layer 5 can be enhanced by heating the nonmagnetic substrate 1 . The heating temperature of the non-magnetic substrate 1 is preferably in the range of 100 to 400°C. In addition, this heating is more preferably performed after the orientation adjustment film has been formed.

On the non-magnetic substrate 1, the orientation adjustment layer 2 is formed by a sputtering process using a sputtering target made of the material of the orientation adjustment layer 2. As the sputtering target, used is made of Co-W alloy, Co-Mo alloy, Co-Ta alloy, Co-Nb alloy, Ni-Ta alloy, Ni-Nb alloy, Fe-W alloy, A layer of at least one alloy selected from the group consisting of Fe-Mo-based alloys and Fe-Nb-based alloys is advantageous. Direction Adjustment Layer 2 can add an element with a secondary effect. As specific examples suitable for such additive elements, Ti, V, Cr, Mn, Zr, Hf, Ru, B, Al, Si, and P can be introduced. The total content of added elements is preferably less than or equal to 20 at%. If the total content exceeds 20 at%, this excess will lead to a decrease in the effect of the above-mentioned orientation adjustment film. The lower limit of the total content is 0.1 at%. If the total content is less than 0.1 at%, the deficiency will lead to ineffectiveness of the effect of the added elements.

The thickness of the direction adjusting layer 2 is preferably in the range of 1 to 30 nm. If the thickness of the direction adjusting film is less than 1 nm, this deficiency will result in failure to obtain a satisfactory crystal orientation of the nonmagnetic underlayer 3 and a decrease in the coercive force. If the thickness of the direction adjusting film exceeds 30 nm, this excess leads to an inevitable decrease in the magnetic anisotropy of the magnetic film in the circumferential direction. In order to enhance the magnetic anisotropy of the magnetic film in the circumferential direction, the thickness of the direction adjusting film is more preferably in the range of 2 to 10 nm.

In order to enhance the adhesion, it is advantageous to interpose a layer having, for example, Ti and Cr as its main components, between the orientation adjustment layer 2 and the nonmagnetic substrate 1 . Although the material used for the intervening layer is not particularly limited, Ti, Cr, Cr-Ti-based alloys, Cr-Mo-based alloys, and Cr-Ta-based alloys are preferable examples of such materials. The content of the second element in these alloy systems is preferably in the range of 10 to 75 at%.

It is recommended to introduce a step of exposing the first surface of the orientation adjusting layer 2 (orientation adjusting film) to an oxygen atmosphere in the manufacturing method. This exposure is preferably performed in an atmosphere containing oxygen at 5×10 ⁻⁴ Pa or more. The gas used for this exposure can be used to maintain contact with water. The duration of the exposure is preferably in the range of 0.5 to 15 seconds. For example, the produced orientation adjusting film is preferably exposed to the surrounding atmosphere or an oxygen atmosphere after it is taken out of the chamber. In addition, the method of exposing the produced membrane by leaving the membrane in the chamber and introducing ambient air or oxygen into the chamber proves to be advantageous. In particular, the method of performing the exposure inside the chamber proves to be particularly advantageous, since it avoids the necessity of a complicated step of taking the film out of the vacuum chamber and thus enables the formation of the film in a It is implemented in the continuous film-forming process of formation. In this case, the atmosphere preferably contains oxygen gas of 5×10 ⁻⁴ Pa or more at a limit degree of vacuum of 10 ⁻⁶ Pa or less. As for the upper limit of the oxygen pressure during exposure to oxygen, although the exposure can be made under atmospheric pressure, the oxygen pressure is preferably less than or equal to 5 x 10 ^-2 Pa.

After the orientation adjustment layer 2 is formed, the non-magnetic underlayer 3 having a structure including at least a Cr—Mn-based alloy layer is formed by a sputtering method. The Mn content of the Cr-Mn type alloy is preferably in the range of 1 to 60 at%, more preferably in the range of 5 to 40 at%. In order to increase the lattice constant, the Cr-Mn-based alloy layer may be added with, for example, Mo, W, V, and Ti. Then, addition of B and Si is effective for refining the crystals, and proves to be advantageous from the viewpoint of improving the SNR performance of the magnetic recording medium.

The thickness of the nonmagnetic underlayer 3 is preferably in the range of 0.5 to 15 nm. If the thickness of the direction adjusting film is less than 0.5 nm, this deficiency leads to failure to obtain sufficient crystal orientation of the non-magnetic underlayer 3 and a decrease in the coercive force. If the thickness of the direction adjusting film exceeds 15 nm, this excess will lead to inevitable deterioration of the magnetic anisotropy of the magnetic film in the circumferential direction.

In order to enhance the matching condition of the lattice constant between the non-magnetic intermediate layer 4 and the magnetic layer 5, a layer composed of Cr-Mo alloy layer, Cr-Ti alloy layer is formed between the non-magnetic lining layer 3 and the non-magnetic intermediate layer 4. At least one alloy layer selected from the group consisting of Cr-W-based alloy layer and Cr-V-based alloy layer is advantageous. This insertion layer brings about the effect of enhancing magnetic properties such as coercive force and enhancing recording performance such as SNR because it enables the Co alloy in the nonmagnetic intermediate layer 4 and magnetic layer 5 formed on the nonmagnetic backing layer 3 to show stronger tends to the (11·0) crystal orientation.

After the nonmagnetic underlayer 3 is formed, the nonmagnetic intermediate layer 4 is similarly formed by a sputtering method using a sputtering target formed of a material having Co as a main component for the nonmagnetic Co alloy layer. The non-magnetic intermediate layer 4 preferably comprises a material composed of Co-Cr-based alloys, Co-Cr-Ta-based alloys, Co-Cr-Ru-based alloys, Co-Cr-Zr-based alloys, and Co-Cr-Pt-based alloys. Any alloy selected from the group. When selecting a Co-Cr type alloy, the content of Cr is preferably in the range of 25 to 45 at% from the viewpoint of enhancing SNR. In addition, addition of B is effective for refining crystals and is advantageous from the viewpoint of enhancing the SNR performance of magnetic recording media. From the standpoint of enhancing SNR, the thickness of the nonmagnetic intermediate layer 4 is preferably in the range of 0.5 to 3 nm.

It is advantageous to use Ru alone or to form a nonmagnetic alloy layer with Ru as a main component on the nonmagnetic Co alloy layer.

After the nonmagnetic intermediate layer 4 is formed, similarly, using a sputtering target made of the material of the magnetic layer 5, the magnetic layer 5 is formed to a thickness of 5 to 40 nm by a sputtering method. The sputtering target consists of Co-Cr-Pt alloys, Co-Cr-Pt-B alloys, Co-Cr-Pt-B-Ta alloys and Co-Cr-Pt-B-Cu alloys Any alloy selected from the group is advantageous. For, for example, Co-Cr-Pt-based alloys, it is advantageous to determine the Cr content in the range of 8 to 28 at % and the Pt content in the range of 8 to 18 at % from the viewpoint of enhancing SNR. For example, Co-Cr-Pt-B type alloys, from the standpoint of enhancing SNR, the Cr content is determined to be in the range of 8 to 18 at%, the Pt content is in the range of 8 to 18 at%, and the B content is in the range of 1 to 20 at%. is favorable. For example, for Co-Cr-Pt-B-Ta alloys, from the viewpoint of enhancing SNR, the Cr content is determined to be in the range of 8 to 25 at%, the Pt content is in the range of 8 to 18 at%, and the B content is in the range of 1 to 20 at%. range and Ta content in the range of 1 to 4 at % is favorable. For example, Co-Cr-Pt-B-Cu alloys, from the viewpoint of enhancing SNR, the Cr content is determined to be in the range of 8 to 28 at%, the Pt content is in the range of 8 to 18 at%, and the B content is in the range of 1 to 20 at%. range and Cu content in the range of 1 to 8 at % is favorable.

From the viewpoint of thermal fluctuation, the thickness of the magnetic layer 5 is preferably greater than or equal to 10 nm. In view of the requirement of high recording density, it is preferably less than or equal to 30nm. If the thickness exceeds 30 nm, this excess inevitably leads to an increase in the grain diameter of the magnetic layer 5 and prevents satisfactory recording and reproducing performance from being obtained. Magnetic layer 5 may be formed in a multilayer structure. Materials for such a structure can be obtained by combining alloys appropriately selected from the above-mentioned alloy groups. When the multilayer structure is selected, from the viewpoint of improving the SNR performance in recording and reproducing performance, the nonmagnetic backing layer 3 is preferably made of Co-Cr-Pt-B-Ta-based alloy or Co-Cr-Pt-B- Cu-based alloys or Co-Cr-Pt-B-based alloys are directly covered and formed. From the viewpoint of improving SNR performance in recording and reproducing performance, the uppermost layer is preferably formed of a Co-Cr-Pt-B-Cu-based alloy or a Co-Cr-Pt-B-based alloy.

After the magnetic layer 5 is formed, a protective film, such as a protective film containing carbon as a main component, is formed using any of known methods such as sputtering, plasma CVC, or combinations thereof.

In addition, optionally, a fluorine-based lubricant such as perfluoropolyether may be applied to the first surface of the protective film by a dipping method or a spin coating method, thereby forming a lubricating film on the protective film.

By combining the magnetic recording medium of the present invention with a magnetic head for recording and reproducing information in the magnetic recording medium, a magnetic recording and reproducing apparatus having excellent performance can be produced.

example 1

As the non-magnetic substrate, an amorphous glass substrate manufactured by MYG Corporation and sold under the designated trademark of MEL-3 was used. The glass substrate measured an outer diameter of 65 mm, an inner diameter of 20 mm and a plate thickness of 0.635 mm.

This glass substrate was subjected to mechanical texturing. The conditions of the mechanical texturing were as follows. The slurry used contained diamond polishing powder with a D90 of 0.12 μm. The slurry was added dropwise at a rate of 50 ml/min for 2 seconds prior to the treatment. A woven fabric made of polyester was used as the abrasive belt. The abrasive belt was fed at a speed of 75mm/min. The rotation frequency of the disk was 600 rpm. The disk was vibrated at a rate of 120 times/min. The pressure applied to the belt was 2.0kgf (19.6N). The duration of the treatment is 10 seconds. When the first surface of the prepared glass substrate was tested with an instrument manufactured by Digital Instrument Corp. and sold under the designated trademark "AFM", it was found that the glass substrate had an average roughness Ra of 0.3 nm and contained Texture with a density of 29,000 lines/mm.

This substrate was thoroughly cleaned and dried, then placed in a DC magnetron sputtering apparatus (manufactured by Anelva Corporation of Japan, sold under the product code "C3010"). While evacuating the apparatus until the final vacuum degree reaches 2×10 ^-7 Torr (2.7×10 ^-5 Pa), an orientation adjustment film is deposited at normal room temperature using a target formed of Cr to a thickness of 1 nm, and then used The target formed of Co-W alloy was deposited Co-W alloy (Co: 45 at%, W: 55 at %) to a thickness of 1 nm at normal room temperature.

After that, the substrate was heated to 250°C. After this heating, it was exposed to oxygen at 0.05 Pa for 5 seconds. As the nonmagnetic underlayer, a target made of Cr-Mn alloy (Cr: 70 at%, Mn: 30 at%) was used to deposit the alloy in a thickness of 6 nm. As the nonmagnetic intermediate layer, a target made of a Co—Cr alloy (Co: 65 at%, Cr: 35 at %) was used to deposit the alloy in a thickness of 2 nm. As the magnetic layer, magnetic Co-Cr-Pt with a thickness of 17 nm was deposited using a target made of Co-Cr-Pt-B alloy (Co: 60at%, Cr: 20at%, Pt: 13at%, B: 7at%) -B alloy layer. A protective film (carbon) was deposited to a thickness of 3 nm on the magnetic layer. The Ar pressure during film formation was set at 3m Torr (0.4Pa). By the dipping method, a lubricant made of perfluoropolyester was applied to form a lubricant layer with a thickness of 2 nm.

After that, a glide test was carried out by using a glide tester and determining that the glide height was 0.3 μin as a test condition. The recording and reproducing performance of the magnetic recording medium that passed the skid test was tested using a read-write analyzer (manufactured by Guzik Corporation and sold under the designated trademark of "RWA 2550"). The recording and reproducing performance thus tested included TAA (reproduced signal output), PW50 (half power width of isolated inversion signal), and SNR (signal-to-noise ratio). In order to evaluate the recording and reproducing performance, a synthesized thin-film magnetic recording head was used, which was provided in a reproducing portion having a large magnetoresistance (GMR) element. The noise used for the test is the integrated noise between 1 MHz and a frequency corresponding to 515.3 kFCl recorded when a pattern signal of 343.5 FCl was written on the medium. The reproduced output was tested at 343.5 kFCl and calculated when SNR = 20xlog (reproduced output/integrated noise recorded between 1 MHz and equivalent to 515.3 kFCl). To determine the coercive force (Hc), a Ker effect type magnetic tester (manufactured by Hitachi Electronic Engineering K.K. and sold under the product code "RO1900") was used. In order to measure the index of magnetic anisotropy, a VSM (manufactured by Riken Denshisha K.K. of Japan and sold under the designated trademark of "BHV-35") was used. The test results are shown in Table 1 below.

Table 1

Examples 2 to 12:

While changing the composition of the non-magnetic underlayer to the various compositions shown in Table 1, relevant treatments were carried out in accordance with the steps in Example 1.

Comparative Examples 1 to 3:

While changing the composition of the non-magnetic underlayer to various compositions shown in Table 1, relevant treatments were carried out according to the steps of Example 1.

Table 1 shows the test results of magnetic properties (indices of coercive force and magnetic anisotropy) and recording and reproducing performance carried out in Examples 1 to 12 and Comparative Examples 1 to 3.

Example 1 covers the case of using a single Cr-Mn alloy layer as the nonmagnetic backing layer. Examples 2 to 7 include the case of using a stacked structure formed of a Cr-Mn alloy layer and a Cr-Mo alloy layer. These examples always show that the index of magnetic anisotropy is higher than 1.3 and are excellent in recording and reproducing performance.

Examples 9 to 12 include the case of using a stacked structure formed of a Cr—Mn alloy layer and a Cr—Mo alloy layer to which the third element was added. They showed that the index of magnetic anisotropy was in the range of 1.5 to 1.7, exhibited strong magnetic anisotropy, and were excellent in recording and reproducing performance.

Comparative Examples 1 and 2 include cases where the nonmagnetic underlayer does not contain a Cr-Mn alloy layer. Comparative Example 1 includes the case of a single Cr-Mo alloy layer. Then, Comparative Example 2 includes the case of using a two-layer structure formed of a Cr layer and a Cr—Mo alloy layer. Comparative Example 3 includes the case of using a Cr-Mn alloy layer having a Mn content of 80 at%. They yielded magnetic anisotropy indices always less than 1.3 and showed recording and reproducing properties which were always inferior to those obtained in Examples 1 to 12 above.

Thus, the magnetic recording medium of the present invention has a direction adjustment layer, a nonmagnetic underlayer, a nonmagnetic intermediate layer, a magnetic layer and a protective layer stacked in sequence on a nonmagnetic substrate having a texture on its first surface And for a magnetic disk, it is characterized in that the non-magnetic underlayer includes at least one layer formed of a Cr-Mn alloy. Due to this specific structure, it is possible to exhibit strong magnetic anisotropy with the circumferential direction as the easy axis of magnetization and to enhance the characteristics of the magnetic recording medium. Therefore, the present invention enables the manufacture of a magnetic recording medium suitable for high recording density.

Industrial Applicability

According to the present invention, the magnetic recording and reproducing apparatus composed of the above-mentioned magnetic recording medium and a magnetic head for recording and reproducing information in the magnetic recording medium enables recording and reproducing of magnetic signals in the magnetic recording medium at high density implemented with excellent recording performance.

Claims (17)

1. magnetic recording media; it comprises direction adjustment layer, non-magnetic under layer, nonmagnetic intermediate layer, magnetosphere and the protective seam that stacks gradually on non magnetic substrate; this its first surface of non magnetic substrate is provided with texture and is used for disk; wherein this non-magnetic under layer contains the layer that one deck is at least formed by Cr-Mn class alloy, and has along the magnetic anisotropy of the easy magnetizing axis of its circumferencial direction.

2. magnetic recording media as claimed in claim 1, wherein this Cr-Mn class alloy comprises one or more elements of selecting from the group that is made of Mo, W, V and Ti.

3. magnetic recording media as claimed in claim 1, wherein this Cr-Mn class alloy is formed by the Cr-Mn-Mo alloy.

4. as each described magnetic recording media of claim 1 to 3, this non-magnetic under layer containing element B wherein.

5. magnetic recording media as claimed in claim 1, the magnetic anisotropy of wherein remanent magnetization amount have and are greater than or equal to 1.3 index, and this index is that along the circumferential direction remanent magnetization amount is divided by radially remanent magnetization amount.

6. magnetic recording media as claimed in claim 1, this Cr-Mn class alloy-layer that wherein forms at least a portion of this non-magnetic under layer has the Mn content that arrives in the 60at% scope 1.

7. magnetic recording media as claimed in claim 1, this Cr-Mn class alloy-layer that wherein forms at least a portion of this non-magnetic under layer has the Mn content that arrives in the 40at% scope 5.

8. magnetic recording media as claimed in claim 1, wherein this non-magnetic under layer has a stacked structure at least, and it is made of Cr-Mn class alloy-layer and Cr-Mo class alloy-layer formed thereon.

9. magnetic recording media as claimed in claim 1, wherein this non-magnetic under layer has a stacked structure at least, and it is made of Cr-Mn class alloy-layer and Cr-Ti class alloy-layer formed thereon.

10. magnetic recording media as claimed in claim 1, wherein this non-magnetic under layer is formed by amorphous glass or crystallized glass.

11. magnetic recording media as claimed in claim 1, wherein this non-magnetic under layer is formed by single crystalline Si or polycrystalline Si.

12. magnetic recording media as claimed in claim 1, this texture that wherein is positioned on this non magnetic substrate that is used for disk has the linear density that is greater than or equal to 7500/mm.

13. magnetic recording media as claimed in claim 1, wherein this direction adjustment layer is formed by at least one laminated gold, and this at least one laminated gold is to select from the group that is made of Co-W class alloy, Co-Mo class alloy, Co-Ta class alloy, Co-Nb class alloy, Ni-Ta class alloy, Ni-Nb class alloy, Fe-W class alloy, Fe-Mo class alloy and Fe-Nb class alloy.

14. magnetic recording media as claimed in claim 1, wherein this nonmagnetic intermediate layer is formed by at least one laminated gold, and this at least one laminated gold is to select from the group that is made of Co-Cr class alloy, Co-Cr-Ta class alloy, Co-Cr-Ru class alloy, Co-Cr-Zr class alloy and Co-Cr-Pt class alloy.

15. magnetic recording media as claimed in claim 1, wherein this nonmagnetic intermediate layer has a stacked structure, this stacked structure is made of layer and one deck Ru or the Ru alloy formed thereon that at least a alloy forms, and this at least a alloy is to select from the group that is made of Co-Cr class alloy, Co-Cr-Ta class alloy, Co-Cr-Ru class alloy, Co-Cr-Zr class alloy and Co-Cr-Pt class alloy.

16. magnetic recording media as claimed in claim 1, wherein this magnetosphere contains one or more alloys of selecting from the group that is made of Co-Cr-Pt class alloy, Co-Cr-Pt-Ta class alloy, Co-Cr-Pt-B class alloy, Co-Cr-Pt-B-Ta class alloy and Co-Cr-Pt-B-Cu class alloy.

17. magnetic recording media as claimed in claim 1, wherein the first surface of this direction adjustment layer is greater than or equal to 5 * 10 through being exposed to contain ^-4Processing in the ambient gas of the oxygen of Pa.

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