JPH04295615A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the coercive force, accordingly, recording density and medium noise of a magnetic recording medium. CONSTITUTION:In this magnetic recording medium composed of a Cr base layer 4 formed on a non-magnetic substrate 3 and a magnetic recording layer 10 formed on the base layer 4 by alternately piling up magnetic layers 5 formed of a ferromagnetic Co alloy and Cr layers, the layers 5 are formed of a CoCrTa alloy.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to magnetic recording media such as magnetic disks.

0002

[Background Art] In recent years, with the increase in the recording density of magnetic recording media, thin films (magnetic layers) of Co alloy-based ferromagnetic metals having uniaxial magnetocrystalline anisotropy, such as CoNiCr and CoCr, have been deposited on non-magnetic substrates. A thin metal film type magnetic recording medium is used. In order to achieve high-density recording in the magnetic recording medium, it is necessary to have a high coercive force, and it is necessary to promote thinning of the magnetic layer. However, when the film thickness is reduced, the product Brδ of the residual magnetic flux density Br and the film thickness δ becomes smaller, resulting in a problem that the reproduction output becomes smaller.

Therefore, as disclosed in JP-A-1-217723, an underlayer made of Cr is provided on a nonmagnetic substrate, and a Co alloy magnetic layer and a nonmagnetic layer are alternately formed on the underlayer. Laminated magnetic recording media have been developed. In this medium, since a large number of thin film magnetic layers with high coercive force are formed, the sum of Brδ of each magnetic layer becomes a large value, and high-density recording is possible without impairing reproduction output.

0004

[Problems to be Solved by the Invention] However, in the magnetic recording medium in which the magnetic layer is laminated, the magnetic layer is made of Co-Ni, Co-Ni-Cr, Co-Ni-W, C
Since o-Ni-W and Co-Pt alloys are used, there is a limit to the improvement in coercive force and the reduction in medium noise, even though the magnetic recording layer is laminated.

The present invention was made in view of the above problems, and an object of the present invention is to provide a magnetic recording medium having high coercive force and low medium noise.

[0006]

[Means for Solving the Problems] The magnetic recording medium of the present invention, which has been made to achieve the above object, has an underlayer made of Cr formed on a non-magnetic substrate, and a ferromagnetic Co In a magnetic recording medium in which a magnetic recording layer is formed in which a magnetic layer made of an alloy and a Cr layer are alternately laminated, the magnetic layer is formed of a CoCrTa alloy.

[0007]

[Example] FIG. 1 shows a partial sectional view of a magnetic recording medium according to an example, in which a base layer 4 made of Cr is formed on a non-magnetic substrate 3, and a uniaxial crystal magnetic Magnetic layers 5 and 7 made of a predetermined ferromagnetic Co alloy with orientation
, 9 and Cr layers 6, 8 are alternately laminated to form a magnetic recording layer 10 with the uppermost layer being a magnetic layer 9 , and further a protective layer 11 is formed thereon.

[0008] The base body 3 is made of amorphous N of about 10 to 20 μm on the Al alloy substrate 1 to ensure rigidity.
An i-P plating layer 2 is formed. The base body 3 is not limited to this configuration, and glass or ceramics may also be used. Incidentally, the upper surface of the Ni--P plating layer 2 is usually subjected to an uneven process called texture in order to reduce the contact resistance with the magnetic head.

Cr underlayer 4 formed on base 3
is the ferromagnetic Co alloy of the magnetic layer 5 formed thereon (
It is formed to in-plane the c-axis (crystal axis indicating magnetocrystalline anisotropy) of the crystal structure (hcp), and is usually 5
It is formed to a thickness of about 0.00 to 2000 Å. Ferromagnetic Co forming the magnetic layers 5, 7, 9 of the magnetic recording layer 10
As the alloy, a CoCrTa alloy having an hcp crystal structure is used. Preferably, the Cr content is 7 to 18 at%,
It is preferable that the Ta content is 1 to 6 at%. Cr content is 7
When it is less than at% or exceeds 18 at%, the c-axis of the Co alloy shifts to random orientation instead of in-plane orientation, resulting in a decrease in coercive force and a decrease in squareness ratio (Br/Bs), resulting in deterioration of electrical properties. It becomes like this. On the other hand, Ta is effective in promoting segregation of Cr and improving coercive force, but 1
If it is less than 6 at%, this effect will be too small, and if it exceeds 6 at%, the formed Co alloy film will not be crystalline but will become amorphous, resulting in a decrease in coercive force.

Regarding the layer thickness of the magnetic layer, each magnetic layer 5, 7
, 9 is preferably 600 to 800 Å, and the thickness of each layer is preferably 100 Å or more. Total thickness is 6
The reason for setting 00 to 800 Å is that Brδ is 450 to 6 as a magnetic recording medium in order to secure reproduction output and reduce noise.
This is because 00 G·μ is required. The reason why the thickness of each layer is set to be 100 Å or more is because if the thickness is less than 100 Å, the alloy portion will not be a continuous film but will become scattered in the form of islands, superparamagnetism will appear, and the coercive force will decrease rapidly. In the illustrated example, the magnetic layers 5, 7, and 9 are three layers, but the number of layers can be set freely.

Cr formed between the magnetic layers 5, 7, 9
Layers 6 and 8 are provided for in-plane orientation of the c-axis of the Co-based alloy of the magnetic layer and for weakening magnetic interaction between the magnetic layers, and may have a layer thickness of about 50 to 250 Å. 50
If the thickness is less than Å, the magnetic interaction between the magnetic layers sandwiching the Cr layer is too strong, making it difficult to reduce media noise by multilayering. On the other hand, if the thickness exceeds 250 Å, the medium noise will increase and the electrical characteristics will also deteriorate.

A non-magnetic protective layer 11 made of carbon or the like is formed on the magnetic recording layer 10 to a thickness of about 200 to 400 Å, and a lubricant such as fluorinated polyether is further applied thereon to a thickness of about 20 to 50 Å. You can. Note that the protective layer 11 and the lubricant coating layer may be formed as necessary. In addition, as an industrial method for forming the Cr underlayer, magnetic layer, Cr layer, and nonmagnetic protective layer, sputtering equipment equipped with target materials for forming the desired layers is installed in parallel, and the substrate is sputtered for each sputtering process. The layers may be sequentially transferred to the apparatus to form a layered film.

Next, specific examples will be given. (1) A Ni--P plating layer was formed on an Al substrate, and a Cr underlayer 4 of 1200 angstroms was formed on the Ni--P plating layer using a substrate whose surface was textured. On top of that, a magnetic layer with the thickness shown in Table 1 is placed between two to
Laminated with four layers. After forming the uppermost magnetic layer, a carbon layer with a thickness of 250 Å was further formed thereon.

A DC magnetron sputtering device was used as the film forming device, and the film forming conditions were Ar gas pressure of 5 mm To
rr, and the substrate temperature was 250°C. Table 1 also shows the Co alloy composition (composition of the magnetic layer) used as the target.

[0015]

[Table 1]

(2) Coercive force H of the magnetic recording medium after film formation
c. Examined medium noise SNm. Media noise is understood by the squareness ratio S* of coercive force. The smaller S* is, the more S
Nm is large and noise characteristics are good.

[0017]

[Table 2]

(3) From Table 2, it can be seen that the magnetic recording medium of the example has a significant improvement in coercive force compared to the comparative example. Media noise has also been improved.

[0019]

As explained above, in the magnetic recording medium of the present invention, the magnetic layer of the CoCrTa alloy is laminated with the Cr layer interposed therebetween, so that the thinner magnetic layer and the excellent magnetic properties of the CoCrTa alloy can be achieved. In combination, it was possible to significantly improve the coercive force and thus the recording density, and also to reduce medium noise.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a main part of a magnetic recording medium according to an example.

[Explanation of symbols]

3 Base 4 Base layer 5 Magnetic layer 6 Cr layer 7 Magnetic layer 8 Cr layer 9 Magnetic layer 10 Magnetic recording layer

Claims (1)

[Claims] 1. An underlayer made of Cr is formed on a non-magnetic substrate, and a magnetic recording layer is formed on the underlayer, in which magnetic layers made of a ferromagnetic Co alloy and Cr layers are alternately laminated. 1. A magnetic recording medium characterized in that a magnetic layer is formed of a CoCrTa alloy.