JPH04356728A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To additionally improve the coercive force and recording density of the magnetic recording medium laminated with magnetic layers via nonmagnetic layers. CONSTITUTION:Films are formed by an ion beam sputtering method as a sputtering method in the process for producing the magnetic recording medium by forming a substrate layer 4 consisting of Cr on a nonmagnetic base body 3 and alternately laminating the magnetic layers 5 consisting of a ferromagnetic Co alloy and the Cr layers 6 by the sputtering method on this substrate layer, thereby forming a magnetic recording layer 10.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing magnetic recording media such as magnetic disks, and more particularly to a method for improving holding force.

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. Metal thin film magnetic recording media formed by sputtering are 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 promoting thinning, the residual magnetic flux density Br and the film thickness δ
There is a problem in that the product Brδ becomes small, and the reproduction output becomes small.

Therefore, as disclosed in JP-A-1-217723, an underlayer made of Cr is provided on a non-magnetic substrate, and Co is deposited thereon by plasma sputtering.
A method has been developed in which alloy magnetic layers and nonmagnetic layers are alternately laminated. According to this method, since a plurality of thin film magnetic layers with high coercive force are formed, the sum of Brδ of each magnetic layer becomes a large value, and the recording density can be improved without impairing the reproduction output.

[0004] As is well known, the plasma sputtering method is
Plasma is generated directly in the space near the surface of the target (film forming material) in the sputtering tank, ions in the plasma are accelerated and collided with the target at a high negative potential, and the sputtered atoms ejected from the target are transferred onto the substrate. This is a method of forming a film while depositing it on the surface.

[0005]

[Problems to be Solved by the Invention] However, when a film is formed by plasma sputtering, the surface of the film is exposed to plasma during film formation, and sputtering gas (mainly Ar gas) exists at a pressure of about 3 to 20 mmTorr, so that the magnetic layer The purity of the ferromagnetic Co alloy forming the ferromagnetic Co alloy decreases, and the orientation of the c-axis, which exhibits uniaxial magnetocrystalline anisotropy, is poor, improving the coercive force,
As a result, there was a limit to the improvement in recording density.

The present invention was devised in view of this problem, and provides a method for manufacturing a magnetic recording medium that can further improve the coercive force and recording density of a magnetic recording medium in which a magnetic layer is laminated with a non-magnetic layer interposed therebetween. The purpose is to provide

[0007]

[Means for Solving the Problems] In the manufacturing method of the present invention, an underlayer made of Cr is formed on a non-magnetic substrate, and a magnetic layer made of a ferromagnetic Co alloy and a Cr In a method of manufacturing a magnetic recording medium in which a magnetic recording layer is formed by alternately stacking layers, the invention is characterized in that the film is formed by an ion beam sputtering method as the sputtering method.

[0008]

[Operation] In the ion beam sputtering method, the ions that collide with the target and eject the sputtered atoms are generated in an ion generation layer independent of the sputtering tank, so there is no need to generate plasma in the sputtering tank. A high vacuum of usually 0.05 to 0.5 mmTorr can be maintained inside the chamber. Therefore, the sputtered atoms ejected from the target hardly collide with the sputtering gas on the way, and reach the substrate as they are, where they are deposited. Therefore, when forming the magnetic layer, the crystal orientation of the Co alloy film is significantly improved, and the coercive force and recording density can be significantly improved.

[0009]

Embodiments The manufacturing of the magnetic recording medium shown in FIG. 1 will be described below as an example. This medium has an underlayer 4 made of Cr formed on a nonmagnetic substrate 3, and magnetic layers 5, 7, 9 made of ferromagnetic Co alloy having uniaxial magnetocrystalline anisotropy and Cr. A magnetic recording layer 10 is formed in which layers 6 and 8 are alternately laminated and the uppermost layer is a magnetic layer 9, and a protective layer 11 is further formed thereon.

FIG. 2 shows a conceptual diagram of an ion beam sputtering apparatus for carrying out the present invention. A target 22 is installed inside a sputtering tank 21 in a direction oblique to the direction of incidence of the ion beam. A base 3 is placed perpendicular to the traveling direction of the sputtered atoms ejected from the sputtered atoms 22. 24 is an exhaust pipe. An ion generating tank 25 is attached to the sputtering tank 21, and A
Sputtering gas such as r gas is supplied to the ion generating tank 25 through the supply pipe 2.
6. A plurality of targets 22 are attached to a target holder 23, and by rotating the target holder 23, a desired target can be selected and used.

Incidentally, in order to improve the uniaxial orientation of the magnetic layer, a heater for heating the substrate 3 may be provided in the sputtering tank 21. Sputtering conditions vary depending on the sputtering equipment, substrate, target material, etc. used, but generally the sputtering chamber vacuum level is 0.05 to 0.5 mm.
Torr, and the substrate temperature is approximately 150 to 300°C.

[0012] In addition, as for the base body 3, in FIG.
Although the amorphous Ni--P plating layer 2 having a thickness of about m is shown, the structure is not limited to this, and glass or ceramics may also be used. Note that 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 orient the c-axis (crystalline axis indicating magnetocrystalline anisotropy) of (crystalline structure hcp) in the plane, and usually
It is formed by sputtering to a thickness of about 500 to 2000 Å. Magnetic layers 5, 7, 9 of the magnetic recording layer 10
As the ferromagnetic Co alloy forming the
Examples include iCr, CoCrTa, CoCrPt, and the like. The total thickness of each magnetic layer 5, 7, 9 is 600~
The thickness is preferably 800 Å. Total thickness 600~800
Brδ is set as 450 to 600 G・μ as a magnetic recording medium in order to secure reproduction output and reduce noise.
This is because things are in demand. The thickness of each magnetic layer is preferably 100 Å or more. This is because if the thickness is less than 100 Å, the alloy portions 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 by sputtering to a thickness of about 200 to 400 Å, and a lubricant such as fluorinated polyether is further applied thereon to a thickness of 20 to 50 Å. It may be applied to a certain extent. Note that the protective layer 11 and the lubricant coating layer may be formed as necessary. Note that for the Cr underlayer, magnetic layer, Cr layer, and nonmagnetic protective layer, the targets for film formation of each layer are attached to the target holder 23, and the target holder is rotated each time each layer is formed to select a predetermined target. It is sufficient to form a layered film by using this method. Of course, ion beam sputtering equipment without a target holder can also be used, and as an industrial film-forming method, sputtering equipment equipped with a target material for depositing the desired layer is installed in parallel, and each substrate is The layers may be sequentially transferred to a sputtering 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 was formed to a thickness of 900 Å on the Ni--P plating layer using a substrate whose surface was textured. Three or four magnetic layers having the thickness shown in Table 1 were laminated thereon with a Cr layer interposed therebetween. After forming the upper magnetic layer, a carbon layer with a thickness of 250 Å was further formed thereon.

An ion beam sputtering device is used as the film forming device, and the acceleration voltage of the sputtering ion source is set to 120°C.
0V, accelerating current 400mA, and film formation conditions were Ar.
The gas pressure was 0.1 mm Torr, and the substrate temperature was 250°C. Table 1 also shows the Co alloy composition (composition of the magnetic layer) used as the target. As a comparative example, a magnetic recording medium having the layer structure shown in Table 1 was
The film was formed using a magnetron plasma sputtering device. The base, Cr underlayer, and carbon layer are the same as in the example. The film forming conditions were an Ar gas pressure of 5 mm Torr and a substrate temperature of 250°C.

[0018]

[Table 1]

(2) Coercive force H of 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 larger SNm is, and the better the noise characteristics are.

[0020]

[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.

[0022]

As explained above, in the method for manufacturing a magnetic recording medium of the present invention, a plurality of magnetic layers are laminated with a Cr layer interposed therebetween by ion beam sputtering.
The crystal orientation of the alloy can be significantly improved, thereby making it possible to significantly improve the coercive force and thus the recording density.

[Brief explanation of the drawing]

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

FIG. 2 is a conceptual diagram of an ion beam sputtering apparatus for implementing the present invention.

[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 21 Sputtering tank 22 Target 25 Ion generation tank

Claims (1)

[Claims] 1. An underlayer made of Cr is formed on a non-magnetic substrate, and ferromagnetic Co is deposited on the underlayer by sputtering.
A method for manufacturing a magnetic recording medium in which a magnetic recording layer is formed by alternately laminating a magnetic layer made of an alloy and a Cr layer, characterized in that the film is formed by an ion beam sputtering method as the sputtering method. Media manufacturing method.