JPS62218596A - Cobalt-gadolinium alloy plating bath - Google Patents

Abstract

PURPOSE:To obtain an amorphous and ferromagnetic Co-Gd alloy film by electrodeposition at a low bath temp. by adding a Co salt, a Gd salt, a nonaqueous solvent solubilizing the salts and an amine to a plating bath. CONSTITUTION:This Co-Gd alloy plating bath contains a Co salt, a Gd salt, a nonaqueous solvent solubilizing the salts and and amine. The kinds of the Co and Gd salts used are not especially limited but the preferred concn. of each of the salts is about 0.001-2mol/l and the preferred molar ratio between the Co and Gd salts is about 1:1-1:20. The kind of the nonaqueous solvent used is not necessarily limited but formamide is suitable for use as the solvent. Ethylenediamine or alkanolamine is suitable for use as the amine, and the amine stabilizes the bath, enables plating at a low temp. and can increase the amount of Gd in a deposited film.

Description

[Detailed Description of the Invention] Hiko Shishishi Om1 year old Chuichi The present invention produces cobalt-gadolinium (Go) by electrodeposition method.
The present invention relates to a cobalt-gadolinium alloy plating bath capable of obtaining a -Gd) alloy plating film.

11 evil cobalt that the next growth ■ tries to do
Since gadolinium (Go-Gd) amorphous alloy thin films have ferrimagnetism and perpendicular magnetic anisotropy, their use as magneto-optical disk memories has attracted attention. This one-sided memory type is capable of higher density recording than conventional magnetic memory, and is therefore expected to be the next generation one-sided memory type.

Conventionally, this G o -G d amorphous alloy thin film has been created by a dry method such as a sputtering method or a vacuum distillation method, but these dry methods require vacuum conditions.
Further, it is difficult to apply only relatively small parts, which poses problems in terms of productivity and high cost.

For this reason, there is a method of obtaining a G o -G d amorphous alloy thin film using an electrodeposition method, which has the advantages of high productivity, large area production, and low production cost because it does not use a vacuum system. desired.

Means for Solving the Problems and Production In order to meet the above-mentioned needs, the present inventors conducted various studies on obtaining a Go-Gd amorphous alloy thin film by a wet electrodeposition method. As a result, like alkali gold Jρt, gadolinium is an electrochemically quite base metal, so it was difficult to deposit it from an aqueous solution. For example, it has been found that when formamide is used, cobalt and gadolinium can be electrodeposited in an amorphous state as an alloy. However, in a bath in which a cobalt salt or a gadolinium salt is merely dissolved in a nonaqueous solvent, the plating bath temperature needs to be kept at a high temperature, preferably about 100°C. For this reason, the present inventors have found that even if the plating bath temperature is lowered, good G o -
As a result of further studies on Co-Gd alloy plating baths that can obtain Gd alloy plating films, we found that ethylenediamine It is effective to add amines such as amines, and when using a G o -G d alloy plating bath to which such amines are added, the stability of the bath increases, and even at low temperatures of about 50 ° C. Good Co-G that is amorphous and ferromagnetic and has an increased amount of Gd
It was discovered that a d-alloy plating film could be obtained, and the present invention was completed.

Therefore, the present invention provides a cobalt salt, a gadolinium salt,
The present invention provides a Go-Gd alloy plating bath containing a nonaqueous solvent that solubilizes these salts and amines.

The present invention will be explained in more detail below.

The Go-Gd alloy plating bath of the present invention contains a cobalt salt, a gadolinium salt, and a nonaqueous solvent that solubilizes them, as described in 1.

Here, the cobalt salt is not particularly limited, but for example, cobalt hydrochloride, cobalt sulfate, etc. are used, and the gadolinium salt is also not limited, but gadolinium chloride, gadolinium sulfate, etc. are used. The concentrations of these cobalt salts and gadolinium salts are 0.001 to 2 mol/Q, respectively.
In particular, it is preferably 0.005 to 0.5 mol/Q, and the molar ratio of cobalt salt to gadolinium salt is preferably 1:1 to 1:20, particularly 1:2 to 1:15. preferable.

Further, the non-aqueous solvent for solubilizing the cobalt salt and gadolinium salt is not necessarily limited, but formamide or the like is preferably used.

The plating bath of the present invention further adds amines to the above-mentioned bath, thereby stabilizing the bath, making low-temperature plating possible, and increasing the amount of Gd in the deposited film. Here, ethylenediamine, alkanolamine, etc. can be suitably used as the amines, and the concentration thereof is preferably 0.01 to 1 mol IQ, particularly 0.02 to 0.2 mol/Q.

The conditions for plating with this plating bath are as follows:
It is preferable to adopt conditions such that the amount of d is 1 wt. Since a good plating film can be obtained with 4
Temperature conditions of 0-80°C, especially 40-60°C can be employed. In addition, the cathode current density is 20m*A/aJ ~
It is preferable to set it to about 500 wa A/aJ.

G o -G d alloy obtained from the plating bath of the present invention 4
The single film is amorphous with a Gd content of 1% by weight or more;
o -G d The thermal stability of the amorphous alloy film is high, and 40
It does not crystallize with heat treatment at about 0°C, but crystallizes with heat treatment at about 500°C. Further, this Co--Gd alloy plating film is a ferromagnetic material, and the magnetic permeability in the direction perpendicular to the film surface increases as the amount of Gd in the film increases.

According to the plating bath of the present invention, the bath stability is high, and a Co-Gd alloy plating film that is amorphous, ferromagnetic, and has a high crystallization temperature can be formed by electrodeposition with a thickness exceeding 10 μm. It can be stably deposited at a relatively low temperature, and the amount of Gd in the plating film can be easily increased.

Next, examples and comparative examples will be shown to specifically explain the present invention.

[Example, comparative example]

A Co-Gd alloy plating bath (electrolytic solution) with the following composition was created, and the bath temperature was 30 to 80°C and the cathode current density was 10 to 80 mA.
Plating was performed under conditions in the range of /cd.

Heavy-primordial formamide 500 mfl C,oCQ, 0.01 mol/QGd (1
20,09II Ethylenediamine 0.1° For comparison, a bath was prepared in which ethylenediamine was removed from the above electrolytic solution, and plating was performed in the same manner.

Here, the electrolytic cell used for plating had an inner diameter of 120ffl1
11. It is made of a Pyrex container with a depth of 110 mm, allowing dry nitrogen gas to be sent into the solution and into the cell, and is completely sealed. The anode is 25m! I
IX A 20mm platinum plate is used, and the cathode as a base is 10mm x 10mm 1. T,O glass was used after being degreased with acetone. The electrolytic cell has approximately 20
After replacing with dry nitrogen gas for a minute, electrolysis was carried out at constant current density.

The crystal structure of the resulting precipitated film was examined by X-ray diffraction, and Co and Gd were quantified by X-ray fluorescence analysis. The crystallization temperature of the amorphous film was determined by X-ray diffraction method using a high vacuum infrared heat treatment furnace.

FIG. 1 shows the relationship between the current density and the Gd concentration in the deposited film in the bath of the present invention (A) and the comparative bath (B).

Here, the results are obtained when plating was performed at a bath temperature of 50° C. for the bath of the present invention (A) and at a bath temperature of 90° C. for the comparative bath (B). 1st
From the figure, it was confirmed that the bath of the present invention can be operated at a low temperature and that more Gd can be precipitated.

In addition, Figure 2 shows the relationship between the bath temperature of the present invention bath (A) and the Gd concentration in the deposited film. From this result, it is recognized that the lower the bath temperature, the higher the Gd concentration. It was found that Go was induced to eutectoid and electrodeposited.

Next, in the above experiment, the crystal structure of the deposited film was investigated as the current density changed when the liquid composition and bath temperature were kept constant. At current densities below, it takes on a structure as an aggregate of fine crystal grains, and at over 20 mA/cJ, it takes on an amorphous structure, and when the current density and bath temperature are kept constant, it takes on an amorphous structure. As a result of examining the crystal structure of the deposited film, it was found that when the electrolyte concentration ratio is 1:1, the deposited film has a crystalline structure, but in all other cases, it has an amorphous structure.From these results, Gd It was observed that the alloy deposited film containing 1% by weight or more of A was in an amorphous state. Therefore, in order to obtain a Go-Gd amorphous alloy film by the electrodeposition method, it is preferable to adopt plating conditions that form a co-Gd alloy film containing 1% by weight or more of Gd. Something was discovered.

In addition, as a result of investigating the crystallization temperature of the obtained Co-Gd amorphous alloy film, it was found that it did not crystallize even after heat treatment at about 400°C, but crystallization was observed at about 500°C. It was found that the Go-Gd amorphous alloy film is thermally stable.

Note that all the deposited films obtained under normal conditions were smooth and free of cracks.

Here, FIG. 3 shows the Gd concentration in the deposited film and the saturation magnetization (Ms
), the relationship between the coercivity and the coercive force is shown, and FIG. 4 shows the relationship between the Gd concentration in the deposited film and the magnetic permeability. In addition, in Fig. 4, M indicates magnetic permeability in the perpendicular direction, and N indicates magnetic permeability in the parallel direction.From Fig. 4, when the Gd concentration in the deposited film exceeds about 20% by weight, it has perpendicular magnetic anisotropy. You can see that it will become like this.

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between current density and Gd concentration in the deposited film in the bath of the present invention and the comparative bath, and Figure 2 is a graph showing the relationship between bath temperature and Gd concentration in the deposited film in the bath of the present invention. , FIG. 3 is a graph showing the relationship between the Gd concentration in the deposited film, saturation magnetization, and coercive force, and FIG. 4 is a graph showing the relationship between the Gd concentration in the deposited film and magnetic permeability.

Claims (1)

[Scope of Claims] 1. A cobalt-gadolinium alloy plating bath characterized by containing a cobalt salt, a gadolinium salt, a nonaqueous solvent that solubilizes these salts, and amines. 2. Claim 1 in which the non-aqueous solvent is formamide
Plating bath described in section. 3. The plating bath according to claim 1 or 2, wherein the amine is ethylenediamine.