WO2013157468A1

WO2013157468A1 - CrTi-BASED ALLOY FOR ADHESION FILM LAYER FOR USE IN MAGNETIC RECORDING MEDIUM, TARGET MATERIAL FOR SPUTTERING, AND PERPENDICULAR MAGNETIC RECORDING MEDIUM OBTAINED USING SAME

Info

Publication number: WO2013157468A1
Application number: PCT/JP2013/060887
Authority: WO
Inventors: 慶明松原; 長谷川　浩之; 澤田　俊之
Original assignee: 山陽特殊製鋼株式会社
Priority date: 2012-04-18
Filing date: 2013-04-11
Publication date: 2013-10-24
Also published as: TWI576835B; JP2013222488A; CN104246884A; JP5964121B2; SG11201405474QA; CN104246884B; TW201411611A; MY170825A

Abstract

Provided are a CrTi-based alloy for adhesion film layers for use in magnetic recording media, a target material for sputtering, and a perpendicular magnetic recording medium obtained using the alloy. This alloy is a CrTi-based alloy in which the empirical formula in terms of atomic ratio is represented by (Cr,Mo,W)_X(Ti,Ta,Zr)_100-X, where 40≤X≤70, in which the Cr element has been replaced with one or the two elements selected from between Mo and W in such an amount that the proportion of Mo+W is in the range of 10 at% to X/2 at%, and in which the Ti element has been replaced with one or the two elements selected from between Ta and Zr in such an amount that (Ta+Zr)≤20 at% (including 0 at%).

Description

CrTi-based alloy for adhesion film layer and sputtering target material used for magnetic recording medium, and perpendicular magnetic recording medium using the same

Cross-reference of related applications

This application claims priority based on Japanese Patent Application No. 2012-94409 filed on Apr. 18, 2012, the entire disclosure of which is incorporated herein by reference.

The present invention relates to a CrTi alloy for an adhesion film layer and a sputtering target material used for a magnetic recording medium, and a perpendicular magnetic recording medium using the same.

In recent years, the magnetic recording technology has been remarkably advanced, and the recording density of magnetic recording media has been increased to increase the capacity of the drive, realizing a higher recording density than the conventional in-plane magnetic recording media. A perpendicular magnetic recording system capable of being used has been put into practical use. Further, a method of assisting recording by applying heat or microwaves by applying a perpendicular magnetic recording method has been studied. Here, the perpendicular magnetic recording method is a method suitable for high recording density, in which the easy axis of magnetization is oriented perpendicularly to the medium surface in the magnetic film of the perpendicular magnetic recording medium.

In the perpendicular magnetic recording system, a combination of a dual-layer perpendicular magnetic recording medium combining a soft magnetic underlayer and a perpendicular magnetic recording layer and a single pole type head is effective in realizing a high recording density. However, since the thickness of the soft magnetic underlayer is as large as several tens to several hundreds of nanometers, the surface flatness is lowered, which may adversely affect the formation of the perpendicular magnetic recording layer and the flying characteristics of the head. Furthermore, since the film stress is large, the adhesion with the glass substrate may be reduced.

As a means for solving such a problem, for example, as disclosed in Japanese Patent Application Laid-Open No. 2006-114162 (Patent Document 1), an adhesion layer for improving adhesion is provided between the glass substrate and the soft magnetic backing layer. The formed magnetic recording medium is used. The alloy used for the adhesion layer needs to be amorphous in order to ensure surface flatness and good adhesion to the substrate and the magnetic layer.

Therefore, as such an adhesion layer material, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2008-10088 (Patent Document 2), CrTi or Amorphized by adding Ti or Ta to Cr having high adhesion CrTa and the like have been proposed. Japanese Patent Laid-Open No. 2010-92567 (Patent Document 3) proposes a NiTa alloy that is made amorphous by adding Ta to Ni.

JP 2006-114162 A JP 2008-10088 A JP 2010-92567 A

However, when the above-described materials are used, since the specific resistance of the film is high, a film thickness of a certain degree (5 nm) or more is required in order to discharge charges accumulated on the film surface during the sputtering process. When the film is used in such a thick film, the particles gradually increase in the adhesion layer when used for a long time, and the occurrence of defects in the magnetic recording medium may increase.

The present invention has been made in view of the problems as described above, and uses an adhesion layer in which charges accumulated on the film surface are easily discharged during the sputtering process even when the film thickness is reduced, and the occurrence of defects is small. An object of the present invention is to provide a perpendicular magnetic recording medium. That is, as a result of intensive studies, the present inventors have been able to reduce the specific resistance of the adhesion layer, that is, increase the electrical conductivity, and reduce the film surface during the sputtering process even if the film thickness is reduced. An alloy was obtained in which the charge accumulated in the electrode was easily discharged. This alloy is obtained by replacing Cr in the CrTi alloy with 10 at% or more of one or two refractory metals selected from Mo and W to improve electrical conductivity. Furthermore, the present inventors have also obtained an alloy with further improved electrical conductivity by replacing Ti in the CrTi-based alloy with one or two refractory metals selected from Zr and Ta. And the sputtering target material for magnetic recording media using these alloys and the perpendicular magnetic recording medium using the same were also obtained.

According to one aspect of the invention,
A CrTi-based alloy for an adhesion film layer used for a magnetic recording medium,
The composition formula in the atomic ratio of the alloy is represented by (Cr, Mo, W) _x (Ti, Ta, Zr) _100-x , 40 ≦ X ≦ 70,
The Cr element in the alloy is replaced with one or two elements selected from Mo and W in a range of Mo + W: 10 at% to X / 2 at%, and the Ti element in the alloy is Ta and Zr There is provided a CrTi-based alloy substituted with one or two elements selected from the group consisting of Ta + Zr ≦ 20 at% (including 0 at%).

According to another aspect of the present invention, a sputtering target material using the above CrTi alloy is provided.

According to still another aspect of the present invention, there is provided a perpendicular magnetic recording medium using the above CrTi alloy.

As described above, the present invention is an amorphous alloy having high electrical conductivity, and can reduce the thickness of the adhesion layer formed between the glass substrate and the soft magnetic backing film in the magnetic recording medium. It is to provide a sputtering target material. By reducing the thickness of the adhesion layer, particles in the adhesion layer can be reduced, and a perpendicular magnetic recording medium with few defects can be provided. As described above, the alloy for the adhesion layer of this application has an effect of increasing the electrical conductivity and reducing the thickness of the adhesion layer.

In order to reduce the film thickness of the adhesion layer, the present inventors have examined a composition that can increase the electric conductivity while maintaining the amorphous property that is the characteristic of the conventional adhesion layer. It has been found that the electric conductivity can be improved by substituting a part of Cr in the inside with Mo and / or W. Moreover, the amorphous property equivalent to the conventional composition was able to be maintained by including 3 or more types of elements, making the atomic ratio of Cr, Mo, and W into an appropriate range.

The present invention will be specifically described below. Unless otherwise specified, “%” in the present specification means at%.

(A) About Mo + W: 10 at% to X / 2 at% In the alloy according to the present invention, Cr is an element that improves the adhesion to the glass substrate and the soft magnetic backing film. Is an element that exhibits similar properties and has a higher electrical conductivity than Cr. By replacing a part of Cr in the CrTi-based alloy with these elements, high electrical conductivity can be obtained. However, if the total content of Mo and W is less than 10 at%, a remarkable effect is not seen, The range was 10 at% or more. The total content of Mo and W is preferably 15 at% or more. The upper limit was set to X / 2 at% from the relationship with the Cr content of the basic element.

(B) (Cr, Mo, W) _X (Ti, Ta, Zr) _100-X , 40 ≦ X ≦ 70 The ratio of Cr-based alloys (Cr, Mo, W) and the types of elements contained in the alloys are alloys. Affects the amorphous nature. When the ratio of (Cr, Mo, W) is less than 40% or more than 70%, the amorphous property necessary for the adhesion film is lowered. The ratio of (Cr, Mo, W) is desirably 45 to 65%. In addition, since the amorphousness increases as the number of element types in the alloy increases, the amorphousness can be improved by including three or more elements.

(C) About Ta + Zr ≦ 20 at% (including 0 at%) Moreover, Ta and / or Zr, which are refractory metals, are elements that improve electrical conductivity by substituting part of Ti. In addition, Zr and Ta, which are the same group in the periodic table, show characteristics close to Ti, and electric conductivity is further improved by replacing Ti with Ta and / or Zr elements (that is, 0 at% <Ta + Zr). Can be made. However, the addition exceeding 20 at% saturates the effect, so the upper limit was made 20 at%.

Hereinafter, the present invention will be specifically described with reference to examples.
Pure metal (purity of 3N or more) raw material powder having the composition shown in Table 1 was mixed and used as a raw material powder for HIP molding (hot isostatic pressing). For mixing, a V-type mixer was used. The billet for HIP molding was prepared by filling a raw material powder into a carbon steel can having a diameter of 200 mm and a length of 10 mm, followed by vacuum degassing and sealing. This powder-filled billet was HIP-molded under the conditions of a temperature of 1050 ° C., a pressure of 120 MPa, and a holding time of 2 hours. Thereafter, a soft magnetic alloy sputtering target material having a diameter of 95 mm and a thickness of 2 mm was produced from the compact. An adhesion layer thin film was produced on a glass substrate using this sputtering target material.

The inside of the chamber was evacuated to 1 × 10 ⁻⁴ Pa or less, and Ar gas with a purity of 99.99% was charged into 0.6 Pa for sputtering. First, a 20 nm adhesion layer was formed on the cleaned glass substrate, and a 5 nm pure Ta film was formed thereon to prevent oxidation. The pure Ta film was formed using a commercially available pure Ta target.

The single-layer film thus prepared was used as a sample, the amorphous property was evaluated by X-ray diffraction, and the electric conductivity was evaluated by the reciprocal of the specific resistance obtained by the four-terminal method. In the evaluation of the crystal structure, “A” indicates amorphous, and “X” indicates that some microcrystals are observed in the amorphous. Evaluation of electrical conductivity was conducted in Comparative Example No. When the value of Cr50Ti of 8 is 1, x is less than 1 to less than 1.1, Δ is less than 1.1 to 1.3, and is less than 1.3 to 1.5 ○, 1.5 or more were marked as ◎. These results are shown in Table 1.

No. shown in Table 1. Nos. 1 to 9 are examples of the present invention. Reference numerals 10 to 14 are comparative examples.

As shown in Table 1, Comparative Example No. 10 is an alloy composed of two elements of Cr and Ti, and therefore has poor electrical conductivity. Comparative Example No. No. 11 has a high total content of Cr, Mo, and W as high as 70% or more and a low Ti content, and therefore has poor amorphous properties. Comparative Example No. No. 12 has a low amorphous property because the total content of Cr, Mo and W is as low as 35% and neither Mo nor W is contained.

Comparative Example No. Since No. 13 does not contain Mo and W, the electrical conductivity is inferior. Comparative Example No. 14 is Comparative Example No. Like 13 and Mo and W are not contained, electrical conductivity is bad. On the other hand, No. which is an example of the present invention. Since all of 1 to 9 satisfy the conditions of the present invention, it can be seen that both electrical conductivity and amorphous properties are excellent.

As described above, according to the present invention, the specific resistance of the adhesion layer can be reduced, that is, the electrical conductivity can be increased, and the charge accumulated on the film surface during the sputtering process can be increased even if the film thickness is reduced. An easily discharged alloy was obtained. This alloy is obtained by replacing Cr in the CrTi alloy with 10 at% or more of one or two refractory metals selected from Mo and W to improve electrical conductivity. Further, Ti in the alloy was replaced with one or two refractory metals selected from Zr and Ta to obtain an alloy with further improved electrical conductivity. A sputtering target material for a magnetic recording medium and a perpendicular magnetic recording medium using the same can be provided using these alloys.

Claims

A CrTi-based alloy for an adhesion film layer used for a magnetic recording medium,
The composition formula in the atomic ratio of the alloy is represented by (Cr, Mo, W) x (Ti, Ta, Zr) 100-x , 40 ≦ X ≦ 70,
The Cr element in the alloy is replaced with one or two elements selected from Mo and W in a range of Mo + W: 10 at% to X / 2 at%, and the Ti element in the alloy is Ta and Zr A CrTi-based alloy substituted with one or two elements selected from the group consisting of Ta + Zr ≦ 20 at% (including 0 at%).
The CrTi alloy according to claim 1, wherein the Ti element in the alloy is substituted with one or two elements selected from Ta and Zr in a range of 0 at% <Ta + Zr ≦ 20 at%.
3. The CrTi-based alloy according to claim 1, wherein a composition formula in an atomic ratio of the alloy is represented by (Cr, Mo, W) X (Ti, Ta, Zr) 100-X , 45 ≦ X ≦ 65.
The Cr element in the alloy is replaced with Mo + W in a range of 15 at% to X / 2 at% by one or two elements selected from Mo and W. The described CrTi alloy.
Sputtering target material using the CrTi alloy according to any one of claims 1 to 4.
A perpendicular magnetic recording medium using the CrTi alloy according to any one of claims 1 to 4.