JP2003338027A - Magnetic recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance SNR characteristics and recording density by making a fine grain size and crystallinity compatible with each other using a novel base layer structure. <P>SOLUTION: A magnetic recording layer 13 consists of a Co alloy, first and second non-magnetic base layers 12 and 16 have a pure metal having a bcc structure or a laminated structure of combination of two or more layers selected from alloy and a Cr-Mn layer (an alloy thin film) 15 is provided between the non-magnetic base layers 12 and 16. The magnetic recording layer 13 of a Co alloy has a composition of Co-18Cr-12Pt-6B (at.%) and 15 nm film thickness to be fixed. The first base layer 12 is formed by using pure Cr having a bcc structure and excellent in crystal orientation properties in the circumferential direction of a substrate and the second base layer 16 is formed by using Cr-20Mo (at.%) having high consistency with the Co magnetic recording layer 13 in the crystal lattice spacing. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium used in a storage device for information equipment such as a computer.

[0002]

2. Description of the Related Art In recent years, the recording density of storage devices for information equipment has been increased, and in magnetic recording devices as well, the sophistication of magnetic heads for reading and writing information and the sophistication of magnetic recording media for reading and writing information have resulted in high recording. Densification is in progress. In order to increase the recording density of this magnetic recording medium, it is necessary to increase the SNR, which is the ratio of the reproduced signal and the medium noise when recording and reproducing the information signal.

A magnetic recording medium usually has a laminated structure of a plurality of thin films. FIG. 1 is a diagram showing a layer structure schematic diagram of a general magnetic recording medium, in which reference numeral 1 is a non-magnetic substrate (NiP
A plated aluminum alloy, glass, etc., 2 is a non-magnetic underlayer (Cr alloy, etc.), 3 is a magnetic recording layer (Co alloy, etc.), and 4 is a carbon protective layer.

Generally, a magnetic recording medium has a non-magnetic base layer 1 (hereinafter referred to as a base layer) 2 for controlling crystal orientation and a magnetic recording on which information is recorded on a non-magnetic substrate 1 such as aluminum alloy or glass. It is manufactured by sequentially forming the layer 3 and the carbon protective layer 4 for protecting the magnetic recording layer 3 from sliding with the magnetic head.

Crystalline continuity exists from the underlayer in contact with the non-magnetic substrate to the magnetic recording layer farthest from the non-magnetic substrate. Generally, bc is used for the non-magnetic underlayer material.
A metal thin film such as Cr or Cr alloy having a c structure or an intermetallic compound such as NiAl is used as Co in the magnetic recording layer.
A magnetic thin film mainly composed of an alloy of Cr and Cr, to which several kinds of elements are added, and a thin film mainly composed of carbon are used for the protective layer. As a film forming method, a sputtering method or a CVD method is generally used because the characteristics of the thin film can be easily controlled and a high quality thin film can be obtained.

The underlayer and the magnetic recording layer are composed of an aggregate of fine metal crystal grains. In order to increase the SNR and improve the recording density, it is necessary to control the crystal structure of the magnetic recording layer. Specifically, a crystal structure which is finer and has a small number of defects oriented in a predetermined direction is preferable. The crystal structure of the underlayer initially formed on the nonmagnetic substrate plays an important role in determining the crystal structure of the magnetic recording layer. Therefore, controlling the grain size and crystal orientation of the underlayer is essential for improving the recording density of the magnetic recording medium.

For example, in order to enhance the crystal lattice matching with the magnetic recording layer, the underlayer is appropriately alloyed to select the composition, and the underlayer having a high orientation and the underlayer having a high lattice matching are laminated. Has been adopted. In order to miniaturize the crystal of the underlayer, it is effective to reduce the film thickness so as not to enlarge the crystal grain size, and to increase the film forming gas pressure, which has been conventionally adopted.

[0008]

In order to further increase the recording density, crystal control of the underlayer is essential. However, according to the conventional method, it is difficult to achieve a high degree of compatibility between crystal growth, improvement of crystal orientation, and miniaturization of grain size. For example, the crystal grain size is made fine by excessively reducing the thickness of the underlayer, but the crystal growth becomes insufficient, so that the crystal orientation is deteriorated. Further, although it is possible to enhance the crystallinity by selecting the composition or material system, at the same time, it is necessary to use a method of sacrificing the crystallinity such as reduction of the film thickness in order to perform the miniaturization at the same time.

The present invention has been made in view of the above problems, and an object thereof is to improve the SNR characteristic by making the crystal grain size finer and the crystallinity compatible by the new underlayer structure. Another object of the present invention is to provide a magnetic recording medium having an improved recording density.

[0010]

In order to achieve such an object, the present invention according to claim 1 provides at least a nonmagnetic underlayer and a magnetic recording layer on a nonmagnetic substrate by a sputtering method. In a magnetic recording medium having a laminated structure of thin films sequentially formed and further continuously formed with a protective layer by a sputtering method or a CVD method, the magnetic recording layer is a Co alloy and the non-magnetic underlayer has a bcc structure. It has a laminated structure of two or more layers selected from pure metals or alloys, and Cr-Mn is provided between the non-magnetic underlayers.
An alloy thin film is provided.

The invention described in claim 2 is the same as claim 1.
In the invention described in paragraph 1, the nonmagnetic underlayer is pure Cr or a Cr alloy, and CrM existing between the nonmagnetic underlayers.
The Mn composition in the n alloy thin film is 20 at% or less,
The thickness of the rMn alloy thin film is 0.5 nm or more and 3 nm or less.

The invention described in claim 3 is the same as claim 1
In the invention described in paragraph 1, the nonmagnetic underlayer is pure Cr or a Cr alloy, and CrM existing between the nonmagnetic underlayers.
The Mn composition in the n-alloy thin film is 30 at% or less,
The thickness of the rMn alloy thin film is 0.5 nm or more and 2.5 nm or less.

As described above, the present invention proposes that the non-magnetic underlayer has a laminated structure composed of a plurality of thin films, and a CrMn alloy thin film having a predetermined composition and film thickness is inserted between them. The Mn composition in the Cr-Mn alloy thin film is 20 at% or less, and the thickness of the Cr-Mn alloy thin film is 0.5 nm or more 3
nm or less, or the Mn composition in the Cr-Mn alloy thin film is 30 at% or less, and the thickness of the Cr-Mn alloy thin film is 0.5 nm or more and 2.5 nm or less.
As a result, the SNR characteristic of the magnetic recording medium was enhanced and the recording density was improved.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a sectional view for explaining one embodiment of the magnetic recording medium of the present invention. In the figure, reference numeral 11 is a non-magnetic substrate (aluminum alloy with NiP plating, glass, etc.), and 12 is a first underlayer (pure). Cr), 13 is a magnetic recording layer (Co-18Cr-12Pt-6Bat%), 14 is a carbon protective layer, 15 is a Cr-Mn layer (alloy thin film), 16
Indicates the second underlayer (Cr-20 at% Mo).

According to the present invention, at least a non-magnetic underlayer and a magnetic recording layer are sequentially formed on a non-magnetic substrate by a sputtering method, and the sputtering method or CV is continuously performed.
A magnetic recording medium having a laminated structure of thin films in which a protective layer is formed by the D method, wherein the magnetic recording layer 13 is a Co alloy, and the nonmagnetic underlayers 12 and 16 are two layers selected from pure metals or alloys having a bcc structure. A Cr-Mn layer (alloy thin film) is formed between the nonmagnetic underlayers 12 and 16 having a laminated structure of the above combination.
15 are provided.

A first underlayer 12 and a Cr-Mn layer 15 are formed on an aluminum alloy substrate 11 having a Ni-P plated layer which is textured to have an average roughness of 0.5 nm in the circumferential direction.
The second underlayer 16, the Co alloy magnetic recording layer 13, and the carbon protective layer 14 are sequentially formed by DC magnetron sputtering.

The composition of the magnetic recording layer 13 of Co alloy is Co
-18Cr-12Pt-6B (at%), film thickness is 15n
m was constant. The first underlayer 12 is pure Cr, which has a bcc structure and is excellent in crystal orientation in the circumferential direction of the substrate, and the second underlayer 16 is Cr, which has high crystal lattice spacing matching with the magnetic recording layer 13 of Co alloy. It was set to -20Mo (at%).

The thickness of the first underlayer 12 was constant at 7 nm, and the thickness of the second underlayer was constant at 3 nm. Cr-Mn layer 15
Three types of Mn composition were selected from 10, 20, and 30 at%. It has been confirmed that the target composition and the composition of the formed thin film are almost the same for all the metal thin films.

The outer shape of the non-magnetic substrate 11 is 95 mm in circumference.
-Donut shape with an inner circumference of 25 mm and a thickness of 1.0 mm. The thickness of the carbon protective layer 14 was 5 nm. The argon pressure during sputtering was constant at 5 mTorr. Prior to the sputtering film formation, the substrate is heated so that the substrate temperature immediately before the formation of the first underlayer 12 is about 250 ° C.

FIG. 3 shows the SN with the change of the Cr-Mn film thickness.
It is a figure showing a change of resolution which expresses R characteristic and a high frequency characteristic. A spin stand type R / W tester was used for the measurement. A GMR (giant magnetic resistance) type magnetic head is used for the measurement magnetic head, and the measurement radius is 33 mm,
The substrate rotation speed is 4500 rpm, and the measurement line recording density is 308.
kfci.

By providing the Cr-Mn layer 15 with a film thickness of 0.5 nm, an improvement in SNR over the conventional medium having a Cr-Mn layer 15 of 0 nm is recognized. At the same time, the resolution is increasing, and it is confirmed that the frequency characteristics are improved, that is, the applicability to high recording density is increased. Any of Cr-
Regarding the Mn composition, the SNR decreases as the thickness of the Cr—Mn layer 15 increases.

In the case of Cr-10Mn and Cr-20Mn, the thickness is up to 3 nm, and in the case of Cr-30Mn, the thickness is 2.5n.
Up to m, it maintains a higher SNR value than conventional media,
This film thickness is the upper limit in the present invention. It is difficult to form an extremely thin film having a thickness of 3 nm or less with stable physical properties and film thickness. In particular, in the region of less than 0.5 nm, it becomes remarkable, so that less than 0.5 nm is not applied in this embodiment. In the range of 0.5 nm or more and 3 nm or less,
A thicker film is preferable in view of productivity, and the Cr—Mn layer 1 may be formed depending on the required SNR improvement width.
It is preferable to appropriately select the film thickness of 5.

The range of the composition is limited by the following consideration. In Cr-30Mn, compared with the Mn amount less than that,
The applicable range of the thickness of the Cr—Mn layer 15 is narrow. If Mn is added more than this, the applicable film thickness range will be further narrowed and the production margin will be reduced. Therefore, there is an upper limit for the amount of Mn, and the value is 30% from this example.
Limited to.

It is known that the crystal structure of Mn is a cubic lattice formed by combining a plurality of simple bcc lattices. Therefore, as Mn is added to a bcc crystal such as Cr, the bcc lattice gradually becomes disordered. It is considered that the decrease in SNR due to the excessive addition of Mn is due to the disorder of the lattice. When the amount of Mn added is small, such disorder of the crystal lattice cannot occur, so the lower limit is not particularly limited.

In the present embodiment, Cr-10Mn is 1.6 nm.
It has been confirmed that the activated volume of the inserted magnetic recording medium is about 12% smaller than that of the conventional medium. The activation volume is a value approximately equivalent to the volume of crystal grains, and a small value thereof indicates that finer crystal grains are formed. In addition, from the results of electron beam diffraction measurement, Cr-M
No deterioration in crystallinity or crystal orientation due to n insertion was observed.

From the above, it is considered that the improvement of the SNR characteristics by inserting the Cr—Mn layer is due to the refinement of the crystal grain size without deteriorating the crystallinity and the crystal orientation.

The present invention provides a fine underlayer structure while maintaining crystallinity. Therefore, the effect is not lost by the layer structure after the base layer is formed. A new type of magnetic recording medium reported in various fields, for example, a magnetic recording medium in which a Co alloy thin film is inserted between an underlayer and a magnetic recording layer, and two or more magnetic layers via a Ru layer It is also effective for a medium in which an antiferromagnetic coupling is obtained between.

[0028]

As described above, according to the present invention, the nonmagnetic underlayer has a laminated structure composed of a plurality of thin films, and a CrMn alloy thin film having a predetermined composition and a predetermined thickness is inserted between them to form a thin film. It is possible to reduce the crystal grain size and improve the SNR characteristics without deteriorating the crystallinity. The preferable composition and film thickness are as follows: the Mn composition in the Cr-Mn alloy thin film is 20 at% or less, and the film thickness of the Cr-Mn alloy thin film is 0.5 nm or more and 3 nm or less, or the Mn composition in the Cr-Mn alloy thin film. Is 30 at% or less, and Cr-Mn
The thickness of the alloy thin film is 0.5 nm or more and 2.5 nm or less.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic layer structure of a general magnetic recording medium.

FIG. 2 is a sectional view for explaining one embodiment of the magnetic recording medium of the present invention.

FIG. 3 is a diagram showing changes in SNR characteristics and changes in resolution representing high frequency characteristics with changes in Cr—Mn film thickness.

[Explanation of symbols]

1 Non-magnetic substrate 2 Non-magnetic underlayer 3 Magnetic recording layer 4 Carbon protective layer 11 Non-magnetic substrate 12 First underlayer 13 Magnetic recording layer 14 Carbon protective layer 15 Cr-Mn layer 16 Second underlayer

Continued front page    (72) Inventor Satoshi Ikegami             1-1 Tanabe Nitta, Kawasaki-ku, Kawasaki-shi, Kanagawa             Within Fuji Electric Co., Ltd. F-term (reference) 5D006 BB01 CA01 CA05 CA06 DA03                       EA03 FA09

Claims (3)

[Claims] 1. A nonmagnetic underlayer and a magnetic recording layer are sequentially formed on a nonmagnetic substrate by a sputtering method,
Further, in a magnetic recording medium having a laminated structure of thin films in which a protective layer is continuously formed by a sputtering method or a CVD method, the magnetic recording layer is a Co alloy and the nonmagnetic underlayer is a pure metal or alloy having a bcc structure. A magnetic recording medium having a laminated structure of a combination of two or more layers selected from the above, wherein a Cr—Mn alloy thin film is provided between the non-magnetic underlayers. 2. The nonmagnetic underlayer is pure Cr or a Cr alloy, the Mn composition in the CrMn alloy thin film existing between the nonmagnetic underlayers is 20 at% or less, and the thickness of the CrMn alloy thin film is 0. The magnetic recording medium according to claim 1, wherein the magnetic recording medium has a thickness of 5 nm or more and 3 nm or less. 3. The nonmagnetic underlayer is pure Cr or a Cr alloy, the Mn composition in the CrMn alloy thin film existing between the nonmagnetic underlayers is 30 at% or less, and the thickness of the CrMn alloy thin film is 0. The magnetic recording medium according to claim 1, wherein the magnetic recording medium has a thickness of 5 nm or more and 2.5 nm or less.