JPH07109596A - Production of soft magnetic multilayered film - Google Patents

Abstract

PURPOSE:To produce an Fe-Ni multilayered film excellent in soft magnetic characteristics at a low cost. CONSTITUTION:An electric conductive substrate 3 as the cathode is alternately immersed in an electrolytic soln. 2 contg. 0.01-2.0mol/l Ni<2+> ions and an electrolytic soln. 1 contg. 0.01-2.0mol/l Fe<2+> ions. Every time the substrate 3 is immersed, electric current is supplied at 1-100mA/cm<2> density for 0.5-15sec and Ni and Fe layers are alternately laminated on the substrate 3 to produce the objective soft magnetic multilayered film. Since a vacuum device is not required, even a large-sized soft magnetic material is economically produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a multilayer film having excellent soft magnetic characteristics for use in magnetic heads, magnetic sensors, etc. To the manufacturing method.

[0002]

2. Description of the Related Art A magnetic material such as FeNi alloy called Permalloy (registered trademark) is used in a portion such as a magnetic head or a yoke that needs soft magnetic characteristics.
For these magnetic materials, it is desired to develop a new technology that satisfies the requirements for miniaturization and high density.

Permalloy, which has a high magnetic permeability and excellent magnetic properties, has a problem that the saturation magnetization is small because the Fe content is 20 to 30 atomic%. When a material with low saturation magnetization is used for a magnetic head, the film thickness must be increased to maintain the head output at a value sufficient for recording, and the track width was reduced for high-density magnetic recording. It cannot be used as a medium.

In order to solve these problems, a magnetic material having a multi-layer structure (hereinafter referred to as a multi-layer film) has attracted attention.
In the case of a multilayer film, its magnetism can be variously changed depending on the composition, structure, and thickness of the laminated body, so that characteristics that cannot be obtained with a uniform film are expected. For example, a soft magnetic multilayer film having high saturation magnetic flux density, high magnetic permeability and low magnetostriction constant has been developed by alternately laminating layers having different magnetic properties (Japanese Patent Laid-Open No. 64-81208). When a magnetic layer and a non-magnetic layer are alternately laminated in this way to manufacture a multilayer film, the film is formed by a dry process such as a vacuum evaporation method or a sputtering method.

This method of forming a film by the dry process is advantageous in that various materials can be used,
It is necessary to use a vacuum device and there is a limit to the size of the substrate that can be used. In addition, the process is complicated and the cost is disadvantageous.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for inexpensively producing a multilayer film having high saturation magnetization and exhibiting excellent soft magnetic characteristics.

[0007]

SUMMARY OF THE INVENTION The gist of the present invention is that "a conductive substrate is used as a cathode and Ni ²⁺ ions are added in an amount of 0.01 to 2.0 m
Electrolyte solution containing ol / liter and Fe ²⁺ ion 0.01 to 2.0m
Alternatingly immersed in an electrolyte solution containing ol / liter, each time applying a current of density of 1 mA / cm ² or more and 100 mA / cm ² or less 0.5 to 15
The method of manufacturing a soft magnetic multilayer film in which Ni layers and Fe layers are alternately laminated on a substrate by applying a second current.

[0008]

[Function] When Fe and Ni, which have the highest saturation magnetization among the ferromagnetic metals, are laminated, the Fe crystals and magnetic domains are subdivided to reduce the coercive force and improve the soft magnetic characteristics.

In the present invention, a multilayer film is manufactured by laminating magnetic layers by electrodeposition using a conductive substrate as a cathode.

Any substrate can be used so long as Fe and Ni can be laminated by an electrodeposition method. Therefore, if the substrate has conductivity, a glass or plastic substrate coated with a metal or the like can be used. Although it may be used, a metal substrate is preferably used in terms of economy. The surface of this substrate is preferably mirror-finished by mechanical polishing, chemical polishing, electrolytic polishing or the like in order to make the structure of the magnetic film laminated later uniform. By doing so, a multilayer film having a flat interface can be stably manufactured. The electrolytic solution for alternately leaching the substrate contained 0.01% Ni ²⁺ ions.
Electrolyte containing ~ 2.0mol / liter and Fe ²⁺ ion and
The electrolytic solution contains 0.01 to 2.0 mol / liter. At this time, the outermost layer is preferably a Ni layer having excellent corrosion resistance. With either electrolyte, the concentration of the target ion is 0.01 mol /
If it is less than 1 liter, electrolysis does not occur and the current efficiency is extremely poor, and diffusion of solute ions to the electrode surface is the rate-determining process of film formation, so dendritic crystals may form and a continuous film can be stably manufactured. Can not. Further, the concentration of the electrolyte of 2.0 mol / liter is sufficient for laminating the multilayer film by the method of the present invention, and it is uneconomical to use an electrolyte solution having a concentration higher than this, and the concentration of the electrolyte is If it exceeds 2.0 mol / liter, the viscosity of the electrolytic solution may increase and the thickness of the electrodeposited film may vary.

The electrolytic solution is, for example, ferrous sulfate or ferric chloride.
Iron, ferrous nitrate, nickel sulfate, nickel chloride, nickel nitrate, and the like that generate iron ions or nickel ions in an aqueous solution can be used alone or as a mixture as each ion source. In addition to these active ion species, a supporting electrolyte such as sodium sulfate (Na ₂ SO ₄ ) that reduces electrical resistance, and an additive such as a surfactant to obtain a smooth electrodeposited film are added to the electrolytic solution. You may use it.

The electrolytic solution may be basically acidic, but it is preferable to use a strong acid having a pH of about 2 to 3.

The current density for energization is 1 to 100 mA / cm ² , and the energization time is 0.5 to 15 seconds. If the density of current applied is less than 1 mA / cm ^2, to Ni of interest, it is less likely to cause deposition precipitation of Fe are difficult, sharply electrolytic deposition if it exceeds 100 mA / cm ² As a result, the supply of ions to the electrode surface may not catch up, and undesired crystals such as dendrites may grow to form a multilayer film.

According to the method of the present invention, it is possible to obtain a multilayer film having a fine grain structure and good soft magnetic characteristics, but the soft magnetic characteristics deteriorate when the thickness of each layer exceeds 50 nm. On the other hand, 1 nm
If it is less than the above range, the structure as an alternate layer may not be obtained, which is not preferable. Therefore, in order to control the film thickness of each layer to 1 to 50 nm, it is preferable to set the energization time to 0.5 to 15 seconds.

[0015]

FIG. 1 is a diagram for explaining the method of the present invention.

An electrolytic bath was prepared in the rectangular water tanks 1 and 2 having a capacity of 1 liter as follows. Ferrous sulfate (FeSO ₄ ) was used as the Fe ²⁺ source, and nickel sulfate (NiSO ₄ ) was used as the Ni ²⁺ source.
^An aqueous solution containing ²⁺ and an aqueous solution containing various concentrations of Ni ²⁺ were prepared, sulfuric acid was added, and the pH thereof was adjusted to be 1 to 3 as an electrolytic solution (hereinafter, Each of them is called Fe bath and Ni bath).

A copper plate 3 having a size of 40 mm × 40 mm, which is mirror-finished by mechanical polishing, is used as a substrate for the cathode. As shown in FIG. 1, the copper plate 5 (length 160 mm, width 40 mm, thickness 0.4) is used. mm)
Fixed at the bottom of. Further, a pure platinum plate 4 having the same area was similarly fixed to a copper plate 6 to serve as an anode. These two electrodes were fixed to an acrylic sample holder 7 at intervals of 1 cm to form a hanging type parallel counter electrode as shown in the figure.

Next, using a magnetic rotor of a device 9 having a magnetic stirrer and a heater built therein, the electrodes were immersed in an electrolytic bath maintained at 50 ° C. by a heater while stirring at a speed of 800 rpm, and a constant current direct current was applied. The solution was done. Constant current power source 8
The counter electrode was alternately immersed in two types of electrolytic baths for a predetermined energization time to form a multilayer film on the cathode. The current density and the energizing time applied during dipping in the Ni bath and dipping in the Fe bath were constant.

Tables 1 and 2 show the ion concentrations of various electrolytic baths, the density of the applied current, and the application time. Table 1 corresponds to an example of the present invention, and Table 2 is a comparative example.

The electrolysis was terminated when the thickness of the formed multilayer film became 1.0 μm, and the coercive force of the obtained Fe—Ni multilayer film was measured with a coercive force meter. The results are also shown in Table 1 and Table 2. The multilayer film having a coercive force of 1.0 (Oe) or less was evaluated as "suitable", and the multilayer film having a coercive force of more than 1.0 (Oe) was evaluated as "unsuitable".

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

The soft magnetic multilayer film produced by the method of the present invention has a small coercive force and is suitable for use as a magnetic head, a magnetic sensor or the like. Further, since the multilayer film having excellent soft magnetic characteristics can be obtained by appropriately controlling the electrodeposition conditions, it is economically advantageous and can be manufactured even if it is large.

[Brief description of drawings]

FIG. 1 is a diagram for explaining an example of a device configuration for implementing the method of the present embodiment.

[Explanation of symbols]

1: Fe bath, 2: Ni bath, 3: Copper substrate, 4: Platinum plate,
5, 6: Copper plate 7: Sample holder, 8: Constant current power supply, 9: Stirrer / heater

Claims (1)

[Claims] 1. A substrate having conductivity is used as a cathode and is alternately immersed in an electrolytic solution containing 0.01 to 2.0 mol / liter of Ni ²⁺ ions and an electrolytic solution containing 0.01 to 2.0 mol / liter of Fe ²⁺ ions. The soft magnetic multilayer film is characterized in that a Ni layer and a Fe layer are alternately laminated on the substrate by conducting a current having a density of 1 mA / cm ² or more and 100 mA / cm ² or less for 0.5 to 15 seconds each time. Manufacturing method.