JPH0456779B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention is widely applied to magnetic recording media, magneto-optical recording media, magnetic heads, magneto-optical elements, microwave elements, magnetostrictive elements, magnetoacoustic elements, etc.
This method involves the production of spinel-type ferrite films containing Fe ³⁺ , in particular by applying at least ferrous ions to the solid surface, whether metal or non-metal, using an aqueous solution without requiring heat treatment at high temperatures (300°C or higher). The present invention relates to a method for efficiently depositing and producing crystalline ferrite having a spinel structure.

[Background of the Invention] Conventionally, methods for forming a ferrite film on a solid surface are broadly classified into a coating method using a binder, a sheet method, and a method not using a binder.

Examples of ferrite films made by coating methods are currently widely used in magnetic tapes, magnetic disks, etc.; however, (a) magnetic recording density is low due to the presence of nonmagnetic binders between ferrite particles; (b) Utilizes the shape anisotropy of ferrite particles to obtain magnetic anisotropy of the film, which cannot be used for elements that require polycrystals such as optical elements, magnetostrictive elements, and magnetoacoustic elements. However, there was a restriction that the method was limited to γ-Fe ₂ O ₃ and Fe ₃ O ₄ from which needle-like fine particles could be obtained.

In addition, the ferrite film produced by the sheet method has a low filling rate of ferrite particles, so it can only be used as a radio wave absorber as a thick film of 1 mm or more, and cannot be used for the various devices mentioned above that require a high filling rate. There are restrictions.

On the other hand, methods for producing ferrite films that do not use a binder include (1) solution coating, (2) electrophoretic electrodeposition, (3) dry plating methods such as sputtering, vacuum evaporation, and arc discharge, and (4) melt spraying. Methods (1) to (3) described above deposit a film in an amorphous state and then form a film with the desired ferrite crystal structure. Because it is a method to
In (1) and (2), heat treatment is performed at a high temperature of 700℃, and in (3), even if the ferrite contains only iron as a metal element,
℃ or higher, and 700 if it also contains metal elements other than iron.
Heat treatment must be performed at a high temperature of ℃ or higher. Also
In method (4), the substrate must be kept at a temperature of 1000°C or higher during film deposition, and in method (5), the substrate must be made of a single crystal oxide with a high melting point. Even if this method is used, there is a restriction that substances with low melting points and low decomposition temperatures cannot be used as substrates.

Therefore, the present inventors developed a new method whose technical concept is completely different from the conventional method of forming a ferrite film described above, in which a solid surface is brought into contact with an aqueous solution containing at least ferrous ions as metal ions. Therefore, we proposed a method for forming a ferrite film in which FeOH ⁺ or other hydroxide metal ions are adsorbed onto the solid surface, and a ferrite crystallization reaction is carried out by oxidation of the adsorbed FeOH ⁺ (Japanese Patent Application Laid-Open No. 111929/1983). did.

In this ferrite film formation method, for example, in order to precipitate the metal constituting ferrite in an aqueous solution bath as ferrite, metal ions are first transferred to the solid by a reaction on the solid surface using surface activity at the interface between the solid and the aqueous solution. adsorbed on the surface, and then oxidized the metal ions by an appropriate method,
It forms a ferrite film.

Typically, a crystalline ferrite film with a spinel structure containing Fe ³⁺ is formed by the following method.

That is, when a solid with surface activity against adsorption is immersed in an aqueous solution containing at least FeOH ⁺ ,
FeOH ⁺ is adsorbed onto this solid surface. If this is expressed as a chemical formula, it will be as shown in the following formula ().

FeOH ^{+ → FeOH +} − (solid) () Note that ferrous ions in ^an aqueous solution are in a form other than FeOH If SO ^2- ₄ , α=2, β
=1), and with hydrolysis, the above ()
When the reaction of the formula occurs as shown in the following formula, FeA〓 ^+(2- 〓

Claims (1)

[Claims] 1. In order to maintain the solid surface on which the ferrite film is to be formed in a thin liquid film leaking state, a deoxidized aqueous solution containing at least ferrous ions is continuously flowed or sprayed onto the solid surface. , ferrous hydroxide ions or other hydroxide metal ions adsorbed on the solid surface within the liquid film, and oxygen is continuously supplied into the liquid film in parallel with the flowing down or spraying of the aqueous solution. A method for forming a ferrite film, which is characterized by oxidizing the film and causing a ferrite crystallization reaction. 2. The method for forming a ferrite film according to claim 1, characterized in that oxygen is supplied into the liquid film by forming a thin liquid film on the solid surface in an oxygen-containing atmosphere. 3. The method for forming a ferrite film according to claim 1, characterized in that oxygen in the liquid film is supplied by spraying an oxygen-containing gas onto the thin liquid film on the solid surface. 4. The method for forming a ferrite film according to claim 1, characterized in that oxygen is supplied into the liquid film by using an oxygen-containing gas as the gas for spraying the aqueous solution onto the solid surface. 5. The method for forming a ferrite film according to claim 1, wherein the aqueous solution forming the liquid film on the solid surface is given fluidity by gravity or centrifugal force. 6. The ferrite film according to claim 1, wherein the aqueous solution forming the liquid film on the solid surface continuously flows out from the solid surface due to the imparted fluidity. Formation method. 7. The method for forming a ferrite film according to any one of claims 1 to 6, wherein the solid surface is pretreated with plasma.