JPH0766034A - Soft magnetic material film and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a soft magnetic material film made of NiFeP having low coercive force and favorable characteristics as a soft magnetic material and a method to uniformly and stably manufacture the film by electroless plating. CONSTITUTION:A soft magnetic material film consisting of NIFeP, characterized in that the Ni content is 70-85 weight% and the value of the Fe/P (weight ratio) is 8-1, is obtained by treating the film in an electroless plating bath consisting of metal ions with nickel and iron as main components, as well as a water solution containing a PH adjusting agent, and containing 0.2-0.5mol/L of ammonium sulfate as a PH buffer 0.5-1mol/L of citrate as a complexing agent for the metal ions, and 0.005-0.03mol/L of sodium hypophosphite as a reducing agent for the metal ions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soft magnetic material film used as a magnetic head material, a sensor material, a magnetic shield material, or an underlayer of a perpendicular magnetic recording medium.

[0002]

2. Description of the Related Art For example, in the field of magnetic recording, a perpendicular magnetic recording method, which is advantageous in high recording density as compared with the conventional longitudinal recording method, has been proposed, and in recent years, the perpendicular magnetic recording medium has been actively put into practical use. ing.

As a perpendicular magnetic recording medium, a two-layer film structure having a soft magnetic layer having a high magnetic permeability as an underlayer of the perpendicular recording layer is most advantageous from the viewpoint of recording characteristics. High magnetic permeability and low coercive force are required for the characteristics of the soft magnetic layer, but it is necessary that the soft magnetic layer can be mass-produced industrially at low cost.
Conventionally, a permalloy film is generally widely used for such a soft magnetic layer, and is formed by sputtering or electroplating.

[Problems to be Solved by the Invention]

However, in the case of a permalloy film, it is necessary to form a film having a thickness of several μm from the viewpoint of recording characteristics and resistance to external magnetic fields, and the sputtering method is not suitable.
There are electroplating method and electroless plating method as a method for forming a permalloy film by a plating method. When the film is formed by an electroplating method, the film formation rate is high, but it is necessary to make the electrodes face each other industrially. Considering this, there was a problem that the number of treatments per plating bath was small and the production efficiency was low. Further, there is a problem that a composition distribution is generated due to the unevenness of the current density, and as a result, the magnetic characteristics are distributed. Regarding the composition of the soft magnetic material film by electroless plating, NiFeP
, CoP, CoB, etc. have been studied, but with the composition and manufacturing method known at the current stage, the range of conditions for obtaining compositional control and good magnetic properties is extremely narrow, and continuous plating is performed. In this case, there is a problem in stability of the plating bath, and there is a problem that a bath composition that makes good magnetic properties and plating bath stability (hereinafter referred to as bath stability) compatible cannot be obtained.

The present invention has been made in view of the above problems. The composition of a thin film of a soft magnetic material and a method of manufacturing the thin film are studied, and a good soft magnetic material film composition and a stable composition of this film are continuously stabilized. It was possible to find a manufacturing method in which an electroless plating bath having good bath stability required for film formation was used, and the present invention was completed. That is, it is an object of the present invention to provide a soft magnetic material film exhibiting good soft magnetic characteristics and a manufacturing method by electroless plating capable of stably manufacturing the soft magnetic material film at low cost.

[0006]

The soft magnetic material film of the present invention comprises Ni, Fe and P and has a Ni content of 70-70.
It is characterized in that the value of Fe / P (weight ratio) (hereinafter represented by Fe / P) is 8 to 15 at 85% by weight.
The soft magnetic material film of the present invention is made of NiF by X-ray diffraction.
The full width at half maximum of the rocking curve on the e (111) plane is 1
Those having the above composition of 5 degrees or less are particularly preferable.
Furthermore, the method for producing the soft magnetic material film of the present invention comprises a metal ion containing nickel and iron as main components, and a pH adjusting agent-containing ammonium sulfate as a pH buffering agent of 0.2 to 0.5 mol / L, The substrate was treated in an electroless plating bath containing 0.5 to 1 mol / L citrate as a complexing agent for metal ions and 0.005 to 0.03 mol / L hypophosphite as a reducing agent for metal ions. The soft magnetic material film according to claim 1 is manufactured on the surface of the base material.

[0007]

The present invention will be described in more detail below.

The soft magnetic material film of the present invention comprises Ni, Fe and P, and is usually an alloy of these. The alloy here means an alloy composed of at least two or more compounds of the above atoms and / or at least two or more solid solutions of the above atoms, or a mixture of the above compounds and / or solid solutions and one or more of the above atoms.

The soft magnetic material film of the present invention has a magnetic property that its coercive force is 5 Oe or less, preferably 4 Oe or less.
When the Ni content changes, its coercive force also changes to 70% by weight.
The composition of less than 85% and the composition of more than 85% by weight have a coercive force of more than 5 Oe, which is not preferable.

Further, even if the Ni content is 70 to 85% by weight, if the Fe / P value is too large or too small, the coercive force becomes large, which is not preferable. It exhibits excellent soft magnetic properties of 5 Oe or less. Fe / P is
When it becomes smaller than 8, that is, when the proportion of P (phosphorus) increases, phosphorus taken into the film traps the domain wall as a non-magnetic phosphorus compound and acts to increase the coercive force. Therefore, in order to obtain good soft magnetic characteristics, it is preferable to reduce phosphorus contained in the film as much as possible. Although Fe / P increases even if the P content becomes extremely small, when performing electroless plating with hypophosphite as a reducing agent, an industrially appropriate deposition rate is required, so 1
It is not preferable to set the content to the weight% or less.

Ni, Fe, P having the above composition of the present invention
As a result of studying the structure and magnetic properties of the soft magnetic material film made of, it is possible to specify the structure having excellent magnetic properties from the rocking curve indicating the orientation of the NiFe (111) plane by the half width of X-ray diffraction. I knew I could do it. That is, in the case of the above-described soft magnetic material film of Ni, Fe, and P of the present invention, a magnetic field having a half-width of the rocking curve on the NiFe (111) plane by diffraction of 15 degrees or less shows good magnetic characteristics. The smaller the half-width of the rocking curve, the better, but
The actual result is at least once.

The relationship between the phosphorus content and the structure of the soft magnetic material film of the present invention is generally considered as follows. That is, as the phosphorus content in the film increases, the structure becomes amorphous like. Phosphorus incorporated in the film traps the domain wall as a non-magnetic phosphorus compound and acts to reduce the soft magnetic properties. Therefore, in order to obtain good soft magnetic properties, it is preferable to reduce the phosphorus content contained in the film as much as possible. Further, such a film having a strong crystallographic orientation does not crystallize and change its structure like an amorphous even if it is reheated, and therefore it is excellent in magnetic property stability against heat.

Although the phosphorus content changes depending on the concentration of hypophosphite in the plating bath, it affects the crystal structure of the soft magnetic material film. FIG. 1 shows the X-ray diffraction pattern of the NiFeP soft magnetic material film obtained by electroless plating using hypophosphite as a reducing agent by changing the hypophosphorous acid concentration. The lower the concentration of hypophosphorous acid, the more fcc
The structure NiFe (111) has a sharp diffraction peak and has a strong crystal orientation.

Next, in X-ray diffraction measurement, NiFe
The detector was fixed to the peak angle (2θ) of the (111) plane, the incident angle to the sample was scan-measured, and the rocking curve including the information on the crystal orientation degree in the sample film thickness direction was measured. For example, using Mac Science XMP-18 X-ray diffractometer, CuKα target at 50KV, 50m
FIG. 2 shows the relationship between the full width at half maximum of the rocking curve obtained by measurement under the condition A and the coercive force. It can be seen that the softer the magnetic properties, the better the greater the orientation.

Next, a method of manufacturing the soft magnetic material film of the present invention will be described. The method for producing a soft magnetic material film of the present invention is composed of an aqueous solution containing a metal ion containing nickel and iron as main components, and a pH adjusting agent, and ammonium sulfate of 0.2 to 0.5 mol / L as a pH buffering agent. Treat the substrate in an electroless plating bath containing 0.5 to 1 mol / L citrate as a complexing agent and 0.005 to 0.03 mol / L hypophosphite as a reducing agent for metal ions. The above composition on the surface, that is, Ni content of 70 to 85 wt% and Fe / P of 8
15 is a method for producing a soft magnetic material film.

In the production method of the present invention, the composition of the plating bath is most important for obtaining the composition of the soft magnetic material film, the stable plating bath and the productivity (deposition rate). The components of the basic plating bath are as follows. (Components of plating bath) -Metal ion: nickel sulfate-ferrous sulfate-Complexing agent: sodium citrate-Buffer agent: ammonium sulfate-Reducing agent: sodium hypophosphite-pH adjusting agent: sodium hydroxide-ammonia

The reasons for limiting the above components will be described below.
FIG. 3 shows the relationship between the concentration of ammonium sulfate as a pH buffer and the deposition rate. Ammonium sulfate concentration
When it is less than 0.2 mol / L, the precipitation rate becomes small.
Ammonium sulphate acts as a complexing agent at the same time as a buffer because it coordinates with the metal ion as an ammine group. The decrease in the deposition rate is due to the decrease in the coordination of the ammine group,
This is probably because the metal complex has changed to a difficult-to-reduce type. If the ammonium sulfate concentration is higher than 0.5 mol / L, the metal is likely to precipitate, which is not preferable. Therefore, the ammonium sulfate concentration is preferably 0.2 to 0.5 mol / L. Further, since it evaporates as ammonia under high temperature alkali, it is necessary to keep the concentration of ammonia ions (or ammine groups) in the bath constant by adding aqueous ammonia. The addition of this ammonia water also has the effect of suppressing the pH drop.

Citrate concentration affects bath stability during plating operations. If the citric acid concentration is less than 0.5 mol / L, iron oxide will precipitate and the bath stability will be poor. 0.5 m
If plating is performed at ol / L or more, good bath stability is exhibited even during continuous plating.

At the same time, the citrate concentration also affects the coercive force, and as shown in FIG. 4, the coercive force increases as the citric acid concentration increases. In order to have coercive force of 5 Oe or less in soft magnetic properties, 1.2 mol / L or less is preferable, and in order to have soft magnetic properties of 4 Oe or less, 1 mol / L or less is preferable. Therefore, from the viewpoint of bath stability and magnetic properties, the concentration of citrate is 0.5 to 1.0 mol / L, more preferably 0.6.
~ 0.8 mol / L is recommended.

The concentration of hypophosphite affects the deposition rate and the coercive force of the obtained plated film. From the viewpoint of precipitation rate and soft magnetic properties, the hypophosphite concentration is 0.005 to 0.0
3 mol / L, preferably 0.015 to 0.025 mol / L.
When the hypophosphite concentration is less than 0.005 mol / L, the precipitation rate is slow and unfavorable, and when it is more than 0.03 mol / L, the soft magnetic properties are unfavorably poor. Along with this, when electroless plating is performed in this plating bath, a film with a strong crystal orientation is obtained, so even if it is reheated, it does not crystallize and change its structure like the case of the amorphous structure. Excellent magnetic property stability against heat.

Next, an example of the embodiment of the present invention will be specifically described.

[Examples 1 to 5 and Comparative Examples 1 to 5] Examples 1 to 5 in Table 1 were prepared using an aluminum substrate (diameter 48 mmφ x thickness 0.508 mm) on which an electroless plating film of NiP of about 5000 Å was formed as a base material. And immersed in the plating baths shown in Comparative Examples 1 to 5 in Table 2 and subjected to electroless plating under the same conditions shown in Tables 1 and 2. Thus, a soft magnetic material film having a thickness of about 5 μm was obtained. The properties and bath stability of these membranes are shown in Tables 1 and 2.

[0022]

[Table 1]

[0023]

[Table 2]

In Examples 1 to 5, good soft magnetic properties were exhibited, and the bath stability was also good. On the other hand, Fe / P is too small in Comparative Example 1, and Fe / P in Comparative Example 2.
Was too large, and both had large coercive force and were not good in soft magnetic characteristics. Comparative Example 3 was carried out with a large amount of hypophosphite, but the coercive force was also large and the soft magnetic characteristics were not good as compared with the Examples. This is because the content of P (phosphorus) in the film is large. In Comparative Example 4, boric acid was used instead of ammonium sulfate as a buffer, but the soft magnetic characteristics and bath stability were not good. This indicates that ammonium sulfate is more effective as a complexing agent in stability and magnetic properties than boric acid. In Comparative Example 5, although the plating bath was not decomposed due to the small amount of citrate, precipitation of iron oxide was observed and the bath stability was poor. Examples 1-5
A 0.1 μm thick CoCr ₁₇ Ta ₅ perpendicular magnetic recording layer and a carbon protective layer were formed on each of the soft magnetic material films obtained in 1. by a sputtering method. A perpendicular magnetic recording medium showing excellent magnetic recording characteristics could be manufactured. On the contrary, a perpendicular magnetic recording medium was produced on each of the soft magnetic material films obtained in Comparative Examples 1 to 5 by the same process as in the example, but their magnetic recording characteristics were different from those of the example. It was inferior to.

[0025]

According to the present invention, it is possible to obtain a soft magnetic material film having a small coercive force and excellent soft magnetic characteristics, and also a method of manufacturing by an electroless plating bath which has good reproducibility and can be stably mass-produced. It is now possible to provide. Further, this soft magnetic material film can be effectively used as a magnetic head material, a magnetic recording medium, a sensor material and a shield material for these magnetic materials, for example, a hard disk drive case.

[Brief description of drawings]

FIG. 1 shows an X-ray diffraction pattern of a soft magnetic material film obtained by the method of the present invention.

FIG. 2 is a diagram showing a relationship between a full width at half maximum of a rocking curve and a coercive force.

FIG. 3 is a diagram showing the concentration of ammonium sulfate and the deposition rate in the method of the present invention.

FIG. 4 is a diagram showing the relationship between the citrate concentration and the coercive force in the method of the present invention.

Claims (3)

[Claims] 1. Ni, Fe and P, wherein the content of Ni is 70% by weight to 85% by weight and the value of Fe / P (weight ratio) is
A soft magnetic material film having a thickness of 8 to 15. 2. The soft magnetic material film according to claim 1, wherein a half-value width of a rocking curve on a NiFe (111) plane by X-ray diffraction is 15 degrees or less. 3. An aqueous solution containing metal ions containing nickel and iron as main components, and a pH adjusting agent, wherein ammonium sulfate is 0.2 to 0.5 mol / L as a pH buffer, and citrate is a complexing agent for the metal ions. 0.5 to 1 mol / L and hypophosphite as a reducing agent for metal ions 0.005 to 0.
A method for producing a soft magnetic material film according to claim 1 on a surface of a substrate by treating the substrate in an electroless plating bath containing 03 mol / L.