Electrolysis: processes – compositions used therein – and methods – Electrolytic coating – Depositing predominantly single metal or alloy coating on...
Patent
1994-02-22
1996-09-03
Niebling, John
Electrolysis: processes, compositions used therein, and methods
Electrolytic coating
Depositing predominantly single metal or alloy coating on...
205106, 205176, 205180, 205227, C25D 518, C25D 1100, C25D 510, C25D 550
Patent
active
055520308
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a method of making a magnetic material in the form of a multilayer thin film by alloy electroplating, and more particularly to a method of making such a magnetic thin film that is suitable for use as a magnetic head and for magnetic storage.
BACKGROUND OF THE INVENTION
Methods of making amorphous alloy magnetic materials by liquid cooling or sputtering are well known. The method of liquid cooling provides the magnetic material only in the form of a ribbon or wire. The ribbon or wire can not be used as a magnetic thin film on a substrate unless it is bonded to the substrate by the use of an adhesive agent. This has the problem that the bonding strength between the film and the substrate is not always reliable due to secular deterioration of the adhesive agent. The method of sputtering has another problem in that it is very costly.
The conventional method of plating provides no other than a monolayer magnetic thin film. The monolayer thin film is formable on the substrate without the adhesive agent, even if the substrate is complicated in shape. However, the monolayer thin film tends to have scattered, uneven portions and is unable to provide a desired saturation magnetic flux density of more than 8000 (gauss).
The inventors of the present application have developed a method of alloy electroplating into the present invention, considering that the aforementioned problems might be solved by electroplating an improved magnetic multilayer thin film directly onto the substrate.
An object of the present invention is to provide a method of making a magnetic material in the form of a multilayer thin film by alloy electroplating. Another object of the present invention is to provide a method of making such a multilayer thin film that is superior in uniformity as well as magnetic characteristics and directly formable on the substrate, even if the substrate is complicated in shape.
DISCLOSURE OF THE INVENTION
In order to complete the objects as described above, the present invention consists in the method comprising the step of instantly changing the electric current value at predetermined intervals during plating to form different alloy-content plated layers, laminating the thus formed different alloy-content layers into a multilayer thin film, and improving the multilayer thin film in magnetic properties by heat treatment. The electric current value or the plating current density defines the alloy content in each layer plated in the course of the plating operation. The obtained multilayer thin film is superior in uniformity as well as magnetic characteristics.
An instant rise in the electric current value or plating current density alters the alloy content in the plating layer at the same time, so that another alloy-content layer is plated over a previous alloy-content layer. For example, a fresh crystal alloy layer is plated over a previous amorphous alloy layer. Thereafter, an instant reduction in the electric current value alters the alloy content again, for example, another amorphous alloy layer is plated over the crystal alloy layer. When the electric current value is repeatedly changed at intervals during plating to laminate the different alloy-content layers over one another. It is easy to control the multilayer film in content and thickness, because the alloy content and the thickness of each layer are freely determined by adjusting the current value and time interval while the layer is plated.
Thus, different alloy-content layers are laminate over one another to form a mulilayer thin film. It is easy to improve the film in magnetic characteristics by heat treatment. For example, if a multilayer thin film has its amorphous alloy layers modified in full or partly into crystal alloy layers by a heat treatment, it will have a larger saturation magnetic flux density after the heat treatment than before the heat treatment. The heat-treatment temperature can be determined from the data of thermal analysis on different alloy-content plated layers.
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Cohen et al., "Electroplating of Cyclic Multilayered Alloy (CMA) Coatings", J. Electrochem. Soc. , vol. 130, No. 10 Oct. 1983, pp. 1987-1995.
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Onoda Motonobu
Shimizu Kazuo
Tsuchiya Takeji
Watanabe Tohru
Niebling John
Nippon Piston Ring Co. Ltd.
Wong Edna
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