JP2635421B2 - Soft magnetic alloy film - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soft magnetic alloy film having a small magnetostriction constant and a high electric resistance and suitable for a magnetic head.

[Prior Art] In the field of magnetic recording, a recording medium such as a magnetic tape has been promoted to have a high coercive force in order to increase a recording density. However, as a material of a magnetic head corresponding thereto, a saturation magnetic flux density (Bs) is required. High things are required.

As a conventional soft magnetic material (film) with a high saturation magnetic flux density, Fe
-Si-Al alloy (Sendust) is typical,
In recent years, amorphous alloy films mainly composed of Co, which is a ferromagnetic metal element, have been developed.

As a recent attempt, the influence of the magnetocrystalline anisotropy of Fe (the adverse effect on soft magnetism) has been reduced by an alloy film (Fe-C, Fe-Si, etc.) composed of fine crystals containing Fe as a main component. There is an example in which a film having a high saturation magnetic flux density and excellent soft magnetic characteristics is obtained by reducing the film thickness.

[Problems to be Solved by the Invention] By the way, devices incorporating a magnetic head tend to be reduced in size and weight, and are subject to vibration accompanying movement,
It is increasingly used in adverse environments. Therefore, the magnetic head has excellent magnetic properties and, of course, excellent wear resistance to the magnetic tape,
It is required to have high durability in a temperature or corrosive atmosphere, that is, high environmental resistance and vibration resistance. For this reason, it is necessary to perform the gap formation, the incorporation into the case, and the like by glass welding, and the material of the magnetic head needs to be able to withstand the high temperature of the glass welding step in the head manufacturing process.

However, in the conventional soft magnetic alloy film, the Co-based amorphous alloy film is an amorphous forming element in an attempt to increase the saturation magnetic flux density of the amorphous alloy.
It is necessary to reduce the amount of Ti, Zr, Hf, Nb, Ta, Mo, W, etc., but if the amount is reduced, the stability of the amorphous structure decreases, and the temperature required for glass welding (about 500 ° C.) that's all)
Has an unbearable problem.

Further, the above-mentioned alloy film (Fe-C, Fe-Si, etc.) composed of fine crystals containing Fe as a main component causes crystal growth at a high temperature,
Since the soft magnetic properties are deteriorated, it is still difficult to say that it is suitable for glass welding.

The present invention has been made to solve the above problems,
The magnetostriction constant is small, the deterioration of magnetic properties due to processing strain and thermal strain is small, the electric resistance of the film is high, the decrease in high-frequency magnetic permeability due to eddy current loss does not easily occur, and the number of constituent elements is small and easy to realize. It is an object of the present invention to provide a soft magnetic alloy film having high reliability of glass welding.

[Means for Solving the Problems] In order to solve the problems, the invention described in claim 1 has a composition formula represented by Co x My C z, where M is Ti, Zr, Hf, V, N
b, Ta, Mo, W is a metal element or a mixture of one or more of these elements, and the composition ratio x, y, z is 50 ≦ x in atomic%.
<65, 15 ≦ y <30, 20 <z ≦ 30, x + y + z = 100, and the metal structure is basically composed of crystal grains having an average grain size of 0.05 μm or less, and part of the element M Contains a carbide crystal phase.

According to a second aspect of the present invention, in order to solve the above-mentioned problem, the metal structure according to the first aspect has an average particle diameter of about 0.05.
It is composed of crystal grains of μm or less and an amorphous structure, and a part thereof contains a crystal phase of a carbide of the element M.

 Hereinafter, the present invention will be described in more detail.

As a method of forming the alloy film, the alloy film is sputtered,
It is manufactured by a thin film forming apparatus such as evaporation. As the sputtering apparatus, existing apparatuses such as RF bipolar sputtering, DC sputtering, magnetron sputtering, tripolar sputtering, ion beam sputtering, and facing target type sputtering can be used. As a method of adding C into the film, a method of arranging graphite pellets on a target plate to form a composite target and sputtering it, or a method of adding C
A reactive sputtering method using a target (Co-M-based) that does not contain hydrogen and a gas atmosphere in which a hydrocarbon gas such as methane (CH ₄ ) is mixed in an inert gas such as Ar can be used. In the reactive sputtering method, it is easy to control the C concentration in the film, so that a film excellent in a desired C concentration can be obtained.

Since the film thus produced contains an amorphous phase in a considerable proportion and is unstable,
Microcrystals are precipitated by performing a heat treatment of heating to about 400 to 700 ° C. By performing this heat treatment in a static magnetic field or a rotating magnetic field, more excellent soft magnetic characteristics can be obtained. Further, this heat treatment can be performed also as a glass welding step in the manufacturing process of the magnetic head.

The step of depositing the microcrystals does not need to be performed completely, and a sufficient number of microcrystals (preferably at least 50%) may be deposited. The remaining amorphous component does not hinder the improvement of the characteristics.

The reason for limiting the components as described above will be described below.

Co is a main component and is an element bearing magnetism. In order to obtain a saturation magnetic flux density (Bs ≒ 5000G) at least equal to or higher than ferrite, it is necessary that x ≧ 50%. Also,
The upper limit of the Co content of 65% was determined in comparison with the minimum required contents of the elements M and C.

Element M is necessary for improving soft magnetic properties,
Combines with C to form carbide fine crystals. C is required for improving soft magnetic properties and improving heat resistance, and combines with the element M to form carbide microcrystals. Further, when the concentrations of the elements M and C are too high, the volume ratio of the carbide of the element M in the film increases,
The exchange coupling between the Co crystal grains is cut off, and good soft magnetic properties cannot be obtained.

The fine crystals of the carbide of element M act as pinning sites for the magnetic domain walls, have the function of improving the high-frequency characteristics of magnetic permeability, and are uniformly dispersed in the film, so that microcrystals of Co grow by heat treatment and become soft magnetic. It has the function of preventing damage. In other words, when the crystal grains of Co grow and grow, the adverse effect of the magnetocrystalline anisotropy increases and the soft magnetic properties deteriorate, but the fine crystals of the carbide of the element M act as a barrier for the growth of Co grains. Prevent deterioration of magnetic properties.

And since the metal structure is basically composed of microcrystals of 0.05 μm or less, it has better thermal stability than amorphous, and has a smaller crystal moment than the magnetic moment of Co in the amorphous phase. In this case, the magnetic moment of Co becomes higher, so that the saturation magnetic density can be increased.

[Function] In the soft magnetic alloy film, a high saturation magnetic flux density can be obtained because the structure thereof is composed of microcrystals mainly composed of Co. In addition, while containing the elements M and C,
Since the metal structure is composed of fine crystal grains and the adverse effect on the soft magnetism due to the magnetocrystalline anisotropy is reduced, good soft magnetic properties can be obtained. In addition, carbide of element M precipitates
Since the growth of crystal grains containing Co as a main component can be suppressed, the crystal grains do not become coarse even when heated in the glass welding step.

[Examples] (1) Film formation A sputtering target was used in a mixed gas atmosphere of Ar gas and CH ₄ gas, using an RF bipolar sputtering apparatus and a composite target constituted by appropriately arranging Ta pellets on a Co target. As a result, a Co—Ta—C alloy thin film having a thickness of 5 to 6 μm was formed. The concentration of Ta in the film is changed by changing the number of Ta pellets on the target, and the concentration of C is changed by changing the concentration of CH ₄ in the sputtering gas to produce films having various compositions as shown in FIG. did.

The magnetostriction constant (λs) of the obtained film was measured by the optical lever method (cantilever method), and the specific resistance (ρ) was measured by the four probe method.

The values of the magnetostriction constant and the specific resistance after the heat treatment for holding the obtained films of each composition at 550 ° C. for 20 minutes are also shown in FIG. (In FIG. 1, the numerical value in square brackets near the mark indicating the composition of the sample indicates the specific resistance (ρ), and the numerical value near the mark indicates the magnetostriction constant (λs).) The sample having the composition indicated by ○ is a film having the composition of the present invention, and the magnetostriction constant of the sample having the composition is + 6 × 10 ⁻⁷ , the specific resistance is 161 μΩ · cm, and the sample having the composition of The magnetostriction constant is + 8 × 10 ^-7 and the specific resistance is 156μΩcm
Is shown. Therefore, each sample shows a small magnetostriction constant of the order of 10 ⁻⁷ and a high specific resistance.

On the other hand, in the sample in which the Ta content is 15 at% or less, the magnetostriction constant is on the order of 10 ⁻⁶ and the specific resistance is 120 μΩ · cm. In the sample having a C content of 20 at% or less, the magnetostriction constant was in the order of 10 ^-7 , but the specific resistance was 120 μΩ · cm or less.

In addition, among the samples of the other components, those deviating from the composition of the present invention are not preferable because the absolute value of the magnetostriction constant is large and the specific resistance is small.

Incidentally, the present inventors have disclosed a soft magnetic alloy film having a high saturation magnetic flux density and a low magnetostriction constant and excellent soft magnetic properties, as disclosed in Japanese Patent Application Nos. 63-278303 and 1-196014. Has applied for a patent. However, the alloy films of these patent applications are of the quaternary type, and exhibited a low magnetostriction of the order of 10 ⁻⁷ for the first time by adding a fourth element.
In this regard, the film of the present invention is a ternary film,
Ω · cm or more and low magnetostriction.
It does not require complicated composition control as in the original system, and is characterized in that it is easy to manufacture.

[Effects of the Invention] As described in detail above, the present invention is a soft magnetic alloy film composed of fine crystal grains containing Co as a main component. Therefore, the composition of Co in the microcrystal can be easily controlled, so that there is a feature that the implementation is easy. Further, since the magnetostriction constant is small, the magnetic characteristics are not degraded by any of the distortion generated by processing the magnetic head and the thermal distortion generated by glass welding, so that an excellent magnetic head can be provided. Moreover,
Since the film has a high electric resistance, when used as a magnetic head, a decrease in high-frequency magnetic permeability due to eddy current loss hardly occurs, and a magnetic head having excellent reproduction characteristics even at a high frequency can be obtained.

On the other hand, elements M (Ti, Zr, Hf, Nb, Ta, Mo, W) and C, which improve soft magnetism, are added, and the metal structure is composed of fine crystal grains, and the crystal magnetic anisotropy is increased. Since adverse effects on soft magnetism due to properties are reduced, good soft magnetic properties can be obtained.

Furthermore, since the element M is formed of fine crystal grains and the added element M forms a carbide with C and is uniformly dispersed, the crystal grains do not become coarse even when heated in the glass welding step, and a good magnetic property is obtained. Since the characteristics are maintained, a highly reliable medium to high melting point glass can be used as the welding glass, which is suitable as a material for a magnetic head having high performance required for high density recording.

[Brief description of the drawings]

FIG. 1 is a triangular composition diagram showing the relationship between the magnetostriction constant and the specific resistance corresponding to each composition of the alloy film of the example of the present invention and each composition of each alloy film of the comparative example.

Claims (2)

(57) [Claims] The composition formula is represented by Co x My C z, where M is Ti, Z
Among r, Hf, V, Nb, Ta, Mo, and W, one or more metal elements or a mixture thereof, and the composition ratio x, y, z is atomic%
50 ≦ x <65 15 ≦ y <30 20 <z ≦ 30 x + y + z = 100, and the metal structure is basically composed of crystal grains having an average grain size of 0.05 μm or less, some of which A soft magnetic alloy film comprising a crystal phase of a carbide of M. 2. The metal structure basically comprises crystal grains having an average grain size of 0.05 μm or less and an amorphous structure, and a part thereof includes a crystal phase of a carbide of the element M. Soft magnetic alloy film.