WO2014129423A1

WO2014129423A1 - MAGNETIC RECORDING-USE Cr-ALLOY, SPUTTERING-USE TARGET MATERIAL, AND VERTICAL MAGNETIC RECORDING MEDIUM USING SAME

Info

Publication number: WO2014129423A1
Application number: PCT/JP2014/053652
Authority: WO
Inventors: 慶明松原; 亮二林
Original assignee: 山陽特殊製鋼株式会社
Priority date: 2013-02-25
Filing date: 2014-02-17
Publication date: 2014-08-28
Also published as: CN105027203B; MY170548A; TWI615836B; SG11201505973XA; SG10201705531QA; CN105027203A; JP2014164780A; JP6180755B2; TW201503120A

Abstract

Provided, as an orientation control layer for an MgO film, is a BCC-structure Cr-based alloy having a lattice constant for which mismatch with a (001) surface of the MgO is minimal, and a fine and uniform crystal grain distribution. Also provided is a sputtering target material comprising the alloy. This alloy is a magnetic recording-use Cr alloy, the alloy including, in atomic percent, one or more types of elements selected from a group comprising Al, Ti, Mo, W, V, and Ru, in total, in amounts for which the value of a in formula (1) is greater than or equal to 2.919 Å and less than or equal to 3.037 Å, a³ = N/ρΣ(M_nA_n) (1) [in the formula, a represents the lattice constant, N represents Avogadro's number, ρ represents calculated density (g/cm³), m represents the number of elements existing within a unit cell, and A represents atomic weight]. The alloy also includes one or more types of elements selected from a group comprising B, C, P, Si and Sn so as to total 0.1 to 5%, and the remainder comprising Cr and unavoidable impurities.

Description

Cr alloy for magnetic recording, target material for sputtering, and perpendicular magnetic recording medium using them

Cross-reference of related applications

This application claims priority based on Japanese Patent Application No. 2013-34228 filed on February 25, 2013, the entire disclosure of which is incorporated herein by reference.

The present invention relates to an alloy for an MgO seed layer and a sputtering target material used for a heat-assisted magnetic recording medium, and a perpendicular magnetic recording medium using them. In particular, the present invention relates to an alloy for an orientation control layer of an MgO seed layer and a sputtering target material used for a thermally assisted magnetic recording medium, and a perpendicular magnetic recording medium using them.

In recent years, the progress of magnetic recording technology has been remarkable, and in order to increase the capacity of the drive, the recording density of magnetic recording media has been increased. Therefore, a perpendicular magnetic recording system that can realize a higher recording density than the in-plane magnetic recording medium that has been widely used has been put into practical use. The perpendicular magnetic recording system is a method suitable for high recording density, in which the easy magnetization axis is oriented in the perpendicular direction with respect to the medium surface in the magnetic film of the perpendicular magnetic recording medium. Further, a method of assisting recording by applying heat by applying a perpendicular magnetic recording method has been studied.

As the recording density of the magnetic recording medium increases, the volume of the magnetic recording medium per bit decreases. Therefore, the problem of recording demagnetization becomes obvious due to thermal disturbance, and magnetic recording films having higher crystal magnetic anisotropy constants (Ku) (for example, CoPt, FePt, etc.) are required. An isotropic material cannot be recorded by a recordable magnetic field of a current recording head. Therefore, in the heat-assisted recording method, by utilizing the fact that the magnetism of the recording material decreases with temperature, the target area is heated only with recording using laser light or near-field light, thereby enabling magnetic recording.

The heat-assisted recording method is a recording method in which magnetic recording technology and optical recording technology are merged, and the recording magnetic part is preserved by heat from laser light irradiation on a high coercive force medium that cannot be recorded by ordinary magnetic recording technology. After recording with the magnetic force lowered locally, it is rapidly cooled to room temperature and stored with an increased coercive force.

A recording film such as FePt used in the heat-assisted recording system has a crystal structure of L ₁ O different from the hexagonal crystal structure of the conventionally used CoCrPt recording film, and MgO is contained in the seed layer. It is used. For example, as disclosed in JP-T-2010-503139 (Patent Document 1) and JP-A-2011-60344 (Patent Document 2), for controlling the orientation and crystal grain size of the MgO seed layer As the orientation control layer, a pure Cr layer or a Cr alloy layer is used.

Special table 2010-503139 JP 2011-60344 A

However, when the material as described above is used as the material for forming the orientation control layer, the lattice constant mismatch with MgO is large, and no element that controls the crystal grains is added. The result is a membrane with a coarse diameter and large dispersion. For this reason, the orientation of the MgO film is deteriorated and the crystal grain size is increased. As a result, the magnetic film has the same tendency and the recording density cannot be increased.

The present invention has been made in view of the above-described problems. As an orientation control layer of an MgO film, a lattice constant having a small mismatch with the (001) plane of MgO and a fine and uniform crystal grain distribution are obtained. An object of the present invention is to provide a Cr-based alloy having a BCC (body-centered cubic) structure and a sputtering target material made of this alloy. In addition, by using such a Cr-based alloy single layer film as the orientation control layer of the MgO film, a uniform magnetic film with a fine crystal grain size is formed on the fine MgO oriented in the (001) plane. Another object of the present invention is to provide a perpendicular magnetic recording medium.

As a result of intensive studies to solve the above problems, the present inventors have found that a BCC structure having a lattice constant with a small mismatch with the (001) face of MgO and a fine and uniform crystal grain distribution. Addition of (M) group element (Al, Ti, Mo, W, V, and Ru) that dissolves in Cr as a Cr-based alloy reduces the lattice constant mismatch with MgO, and (X) group An alloy system was found in which a small amount of elements (B, C, P, Si and Sn) was added to adjust the crystal grain size.

According to one aspect of the invention,
A Cr alloy for magnetic recording,
at. %so,
Contains one or more elements selected from the group consisting of Al, Ti, Mo, W, V and Ru in such a total amount that the value of a in formula (1) is 2.919 to 3.037. And
a ³ = N / ρΣ (m _n A _n ) (1)
[Where:
a represents a lattice constant,
N represents Avogadro's number,
ρ represents the calculated density (g / cm ³ ),
m represents the number of elements present in the unit cell;
A represents atomic weight. ]
Containing at least 0.1 to 5% of one or more elements selected from the group consisting of B, C, P, Si and Sn,
An alloy comprising the balance Cr and inevitable impurities is provided.

According to another aspect of the invention,
at. %, In which the total amount of one or more of the elements consisting of Al, Ti, Mo, W, V, and Ru is such that the value of a in Formula 1 is 2.919 to 3.037. Containing one or more elements of B, C, P, Si, and Sn in a total content of 0.1 to 5%, the balance being Cr and inevitable impurities A magnetic recording Cr alloy is provided.
a ³ = N / ρΣ (m _n A _n ) (Formula 1)
Where a: lattice constant N: Avogadro number ρ: calculation density (g / cm ³ )
m: number of elements present in the unit cell A: atomic weight

According to another aspect of the present invention, a sputtering target material made of the above magnetic recording alloy is provided.

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

As described above, according to the present invention, a Cr-based alloy having a BCC structure having a lattice constant with a small mismatch with the (001) plane of MgO and a fine and uniform crystal grain distribution, and a sputtering target comprising this alloy According to such an alloy, the orientation of the MgO film can be improved in the magnetic recording medium, and the crystal grain size can be finely and uniformly dispersed. Thus, there has been no technical idea in the past to reduce the mismatch of the lattice constant between the MgO film as the recording layer base film and the distribution control layer and at the same time make the crystal grain size fine and uniform. This is a characteristic technical idea of the present invention.

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

The Cr alloy for magnetic recording according to the present invention is selected from the group consisting of one or more elements selected from the group consisting of Al, Ti, Mo, W, V and Ru, and the group consisting of B, C, P, Si and Sn. One or more elements and the balance Cr and inevitable impurities, preferably consisting essentially of these elements and inevitable impurities, more preferably these elements and inevitable impurities It consists only of (consisting of).

Hereinafter, the present invention will be described in detail. When the Cr-based alloy composition of the BCC structure having a lattice constant with a small mismatch with the (001) surface of MgO and a fine and uniform grain distribution was studied, Al (M) group element which dissolves Cr It has been found that the lattice constant can be adjusted from 2.919 to 3.037 by adding an appropriate amount of one or more of Ti, Mo, W, V and Ru. In addition, by adding a trace amount of one or more of the elements consisting of (X) group elements B, C, P, Si and Sn, the crystal grains can be controlled finely and uniformly while maintaining the BCC structure. I found what I could do.

Hereinafter, the reasons for limitation of the Cr alloy for magnetic recording according to the present invention will be described.

The additive amount Cr of the (M) group element (Al, Ti, Mo, W, V, and Ru) has a lattice constant of 2.880 、, which is twice the root (√2), 4.072 Å, There is a mismatch of −3.3% with respect to 4.21% which is the lattice constant of MgO. Therefore, by adding an appropriate amount of (M) group element (Al, Ti, Mo, W, V, and Ru) to Cr, the lattice constant mismatch is within ± 2.0% while maintaining the BCC structure. It can be made 3.037 mm or less.

By forming a Cr alloy film having a lattice constant mismatch of within ± 2.0% and a lattice constant of 2.919 to 3.037 mm, it is possible to satisfactorily form the (001) surface of MgO. it can. When the lattice constant is smaller than 2.919 mm, the MgO orientation is not different from that of pure Cr. When the lattice constant is larger than 3.037 mm, the (110) plane of MgO is observed and the orientation is deteriorated.

A specific range of the addition amount when only one element is added is shown below as an example.
Al: 9.3 to 43.4%
Ti: 7.5-35.4%
Mo: 11.7 to 55.4%
W: 11.2-52.4%
V: 22.8-94.0%
Ru: 24.5-32.0%
Similarly, in the case of two or more types, the addition amount is within the range of the lattice constant obtained by the calculation of the formula (1) of 2.919 to 3037.

(X) Adding 0.1 to 5% of one or more of group elements (B, C, P, Si and Sn) The above elements are elements that hardly form a solid solution in Cr and form a compound with Cr. , The effect of making the crystal grains finer and making the grain size uniform. Therefore, the optimum addition amount is set in the range of 0.1% to 5%. When the addition amount is less than 0.1%, the effect of addition is not observed. On the contrary, when the addition amount is more than 5%, the compound is remarkably produced and a BCC single phase cannot be obtained.

Hereinafter, the present invention will be specifically described with reference to examples. Pure metal (purity 3N or more) raw material powder was mixed with the composition shown in Table 1 and used as a raw material powder for HIP molding (hot isostatic pressing). A V-type mixer was used for mixing. A 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. Using this sputtering target material, an adhesion layer thin film was produced on a glass substrate. 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 at 0.6 Pa to perform sputtering. First, a 20 nm Cr alloy layer was formed on a cleaned glass substrate.

Using the single-layer film produced as described above as a sample, it was confirmed that it was a BCC single phase by X-ray diffraction, the lattice constant was measured, and the average crystal grain size and its dispersion were observed by TEM observation. As for the average crystal grain size, when the Cr value in Comparative Example 1 is 1, the value is larger than 0.9, x is from 0.9 to 0.8, and is smaller than 0.8. Was marked as ○. Further, with respect to the value normalized by the average crystal grain size for the dispersion, when the value of Cr in Comparative Example 1 is 1, the value larger than 0.9 is x, from 0.9 to 0.7 The ones up to were marked with Δ, and those smaller than 0.7 were marked with ○. These results are shown in Table 1.

As shown in Table 1, no. 1 shows Comparative Example 1, Nos. 2 to 24 are examples of the present invention. 25 to 35 are comparative examples.

Comparative Example No. In No. 25, since the content of B as the (X) group element was high, precipitation of the second phase was remarkably generated, and a BCC single phase was not obtained. Comparative Example No. No. 26 has a high content of C which is the (X) group element. Similar to 25, precipitation of the second phase was remarkably generated, and a BCC single phase was not obtained. Comparative Example No. In Nos. 27 to 28, since the (X) group element was not added, the effect of refining crystal grains and uniforming the grain size could not be obtained. Comparative Example No. No. 29 (X) group element is not added and the lattice constant is larger than 3.037Å, so that the effect of refining crystal grains and uniforming the grain size cannot be obtained, and MgO (110 ) Plane was observed and the orientation deteriorated.

Comparative Example No. No. 30 (X) group element is not added, and since the lattice constant is smaller than 2.919 mm, the refinement of crystal grains and the uniformity of grain size are poor, and the orientation of MgO is pure Cr and The difference was not seen. Comparative Example No. In No. 31, since the total content of B and C which are (X) group elements was high, precipitation of the second phase was remarkably generated, and a BCC single phase was not obtained. In addition, since the lattice constant was smaller than 2.919 mm, the MgO orientation was not different from that of pure Cr. Comparative Example No. For 32 to 35, since the lattice constant was larger than 3.037 mm, the (110) plane of MgO was observed, and the orientation deteriorated.

On the other hand, No. which is an example of the present invention. Since all of Nos. 2 to 24 satisfy the conditions of the present invention, it is possible to obtain a Cr-based alloy having a BCC structure having a MgO orientation and a lattice constant with a small mismatch and a fine and uniform grain distribution. I understood that I was able to do it.

As described above, according to the present invention, as the orientation control layer of the MgO film, a Cr-based BCC structure having a lattice constant with a small mismatch with the (001) surface of MgO and a fine and uniform grain distribution. By using an alloy single layer film, it is possible to provide a perpendicular magnetic recording medium in which a uniform magnetic film having a fine crystal grain size is formed on fine MgO oriented in the (001) plane. An effect is produced.

Claims

A Cr alloy for magnetic recording,
at. %so,
Contains one or more elements selected from the group consisting of Al, Ti, Mo, W, V and Ru in such a total amount that the value of a in formula (1) is 2.919 to 3.037. And
a 3 = N / ρΣ (m n A n ) (1)
[Where:
a represents a lattice constant,
N represents Avogadro's number,
ρ represents the calculated density (g / cm 3 ),
m represents the number of elements present in the unit cell;
A represents atomic weight. ]
Containing at least 0.1 to 5% of one or more elements selected from the group consisting of B, C, P, Si and Sn,
An alloy composed of the balance Cr and inevitable impurities.
The alloy according to claim 1, which is used for an orientation control layer in a perpendicular magnetic recording medium.
at. %so,
Any one element selected from the group consisting of Al, Ti, Mo, W, V and Ru is within the following range:
Al: 9.3 to 43.4%
Ti: 7.5-35.4%
Mo: 11.7 to 55.4%
W: 11.2-52.4%
V: 22.8-94.0%, or Ru: 24.5-32.0%
The alloy according to claim 1 or 2, comprising:
A sputtering target material comprising the alloy according to any one of claims 1 to 3.
A perpendicular magnetic recording medium using the alloy according to any one of claims 1 to 3.