JPS6281008A - Amorphous high saturable magnetic flux density material - Google Patents

Abstract

PURPOSE:To provide an amorphous magnetic material having high saturated magnetic flux density and low coercive force by using high Co density rare earth metals-Co alloy having specific composition. CONSTITUTION:An amorphous cobalt alloy having a composition formula of Co1-a-bMaXb and satisfying 0<=a, b<=0.1, 0.04<=a+b<=0.1 (where M is at least one of Y and La, and X is at least one of Ta, W, Nb, Mo, V and Cr) is useful as a magnetic core magnetic material having a larger saturated magnetic flux density (15,000-16,000 gausses) than conventional NiFe, Co-Zr, thereby performing a thin-film magnetic head which can record in high density.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to an amorphous magnetic material having a high saturation magnetic flux density and a low coercive force, and particularly to a cobalt alloy suitable for use in a core for a thin film magnetic head.

[Background of the invention]

Conventionally, coercive force He applied to core materials for thin film magnetic heads
As soft magnetic materials with a small value, crystalline magnetic materials such as Ni-Fe alloys and amorphous materials such as Co-Nb-Zr alloys are used. Ni-Fe alloys are chemically and thermally stable, while CO-Nb-Zr alloys are easy to fabricate and have high magnetic permeability.

The saturation magnetization of these materials is about too Gauss.

However, in recent years, the capacity of magnetic recording devices has increased, and at the same time, there is a demand for space saving and cost reduction of the devices themselves. For this reason, increasing magnetic recording density has become an important issue. The increase in recording density is achieved by increasing the track density by decreasing the track width and increasing the linear density by decreasing the recording bit length, as indicated by Tw in FIG. Here, it is shown in Japanese Patent Publication No. 40245/1983 that in order to reduce the recording wavelength on the medium, it is necessary to reduce the core thickness of the thin film magnetic head. That is, in the cross section of the thin film magnetic head in FIG.
Between the upper core thickness tu, the lower core thickness 1 m, the gap length tg, and the recording wavelength λ, λ)1. +t, @+tm relationships are established. Therefore, in order to decrease the recording wavelength λ, it is necessary to decrease the core thicknesses tu and ta and the gap length tg.

However, when the core thickness is reduced, the write magnetic field emitted from the tip of the head to the medium during writing is reduced. Therefore, coil 3
If the write current applied to the magnetic core 1 is increased, the magnetic flux in the magnetic core 1 will be saturated, and a sufficient write magnetic field will not be obtained. code 2
4 indicates a coil terminal, and 4 indicates a board. The saturation limit of the magnetic flux within the magnetic core increases as the saturation density of the core material increases, provided the core shape is the same.

The saturation magnetic flux density of 80% NiFe alloy (permalloy) for thin-film magnetic heads is 10,000 Gauss, and in order to compensate for the decrease in core thickness due to higher recording densities, it is necessary to use high saturation magnetic flux density materials that have a saturation magnetic flux density higher than permalloy. It is necessary to adopt it in the magnetic core. At the same time, in order to ensure sufficient magnetic permeability for reading, the coercive force He of the core material must be 30e or less.

The saturation magnetic flux density (hereinafter abbreviated as Bs) of crystalline materials is too
oo or more is F, which is an alloy system centered on Fe.
e-8i, Fe-Ti, etc., but these inherently have the disadvantage of being easily rusted. On the other hand, there is a CO-based amorphous magnetic alloy in which CO is the main component and 10 atomic % or less of additional elements are added to make it amorphous.

The Go-Zr system is typical, and a B s of 15,000 Gauss has been obtained in C0-5% Zr. Amorphous materials have the following characteristics compared to crystalline materials. Namely: 1) It is amorphous and has no crystal magnetic anisotropy. 2) Amorphous metals have 3 to 5 times higher electrical resistance than crystalline metals. 3) High hardness, etc. For this reason, amorphous magnetic materials have 1) crystal grain size,
There is no troublesome orientation control, 2) there is little reduction in high frequency magnetic permeability due to eddy current loss, and 3) there are advantages of excellent durability.

Depending on the manufacturing method, the amorphous magnetic alloy includes a metal-metalloid amorphous alloy manufactured by a molten metal quenching method and a metal-metallic amorphous alloy manufactured by a sputtering method or a vacuum evaporation method. The former is mainly used for laminated cores of transformers and bulk-type magnetic heads, but thin-film magnetic heads cannot be manufactured using this method.
This is done by alloying i with a metal having a larger atomic radius than those metals and making it amorphous. In the sputtering method, Fe,
An alloy film is created by creating a target with Go and Ni, placing chips of additive elements on the target surface, and sputtering.In the vacuum evaporation method, Fe, Co, and Ni and the alloy components are simultaneously evaporated and alloyed on the substrate. let The saturation magnetization of a simple metal is F e (22000 Gauss)
, Co (17000 Gauss), and Ni (6
000 Gauss), and Fe and Co are selected for the development of high BS materials. However, alloys based on Fe have problems with corrosion resistance, and most of the alloys being studied as high Bs materials are c.

It is an amorphous alloy.

As CO-based amorphous alloys, Go-Zr, Co-Zr-Ta, and the like produced by sputtering are being considered. Z
In addition to r, it is Co-Zr magnetostriction 2 that alloys Ta.
Since X10-8 is large and may deteriorate the magnetic properties of the magnetic head due to the magnetoelastic effect with film stress, the purpose is to alloy Ta, which has the function of making magnetostriction negative, to reduce magnetostriction. J, Appl, Phys, 55 (198
4) Co-Nb+C as shown in 1769
The magnetostriction of the o-Ta and Co-W amorphous alloys is negative, and V, C:r, and 'Mo, which belong to the same 5A and 6A groups, also have the function of making the magnetostriction of the amorphous Go alloy negative. Although magnetostriction can be reduced by adding these 5A and 6A group elements to Co-Zr, Bs decreases depending on the amount of added elements.

By the way, there are alloy systems that are the same amorphous CO-based magnetic alloy but have completely different properties. Rare earth-XX series amorphous alloys are being studied as magneto-optical recording media, have perpendicular magnetic anisotropy, and have a large coercive force of several hundred oersteds. Gd-
Co, Dy-Co.

Typical examples include Ho-G O. As an alloy of this system, Phys, Rev. B7 (1978),
2215 with Go-Y, Co-La, and Co-
Although there are examples of investigating the magnetic moment of S c -based amorphous magnetic alloys, the magnetic properties on the high CO side were unknown.

[Purpose of the invention]

An object of the present invention is to provide a soft magnetic material for a magnetic core having a high saturation magnetic flux density.

[Summary of the invention]

In order to investigate the magneto-optical effect of rare earth-XX alloys with high CO concentrations, the present inventors fabricated Co-Y alloys by sputtering and investigated their magnetic properties, which are difficult to achieve with Go-Y amorphous alloys. It has been found that the coercive force in the axial direction is 20e or less. Y is Gd.

Since it belongs to the same rare earth group as Dy and Ha and forms intermetallic compounds such as < Y Cos, which is the same as G d Cos, it is difficult to imagine that the Go-Y based amorphous alloy exhibits soft magnetism. Therefore, the reason why the Go-Y alloy exhibits soft magnetism will be considered.

As shown in Table 1, the ionic radius of rare earth elements is larger than that of CO8+, which is 0.53 (human). In general, alloy systems that form an amorphous state need to have large ionic radii, and the larger the difference, the wider the concentration difference that forms the amorphous state. In other words, an element having a large difference in ionic radius from Co can make CO amorphous by adding a small amount. Therefore, it is considered that rare earth elements tend to make CO amorphous. By the way, from Table 1, Y, La
.

Eu and Lu have no magnetic moment. on the other hand.

Gd, Tb, Ha, etc. used in magneto-optical recording media all have magnetic moments. It is known that the magnetic moments of the rare earth and Go point in opposite directions and cancel each other out, so that the 1-alloy gold body becomes a ferrimagnetic material with low spontaneous magnetization. Namely.

The magnetic moment of rare earth ions such as Gd is
They interfere with the magnetic moment of O ions (exchange interaction) and try to reverse each other's magnetization. Therefore, in order to reverse the magnetic moment of a rare earth ion, it is necessary to simultaneously reverse the magnetic moments of a large number of surrounding CO ions, and it is therefore thought that the coercive force increases. On the other hand, in Y, La, Eu, and Lu, there is no interaction between rare earth elements and Co, and magnetization reversal is thought to be easy, resulting in a decrease in magnetic force. To confirm this, Sm has a magnetic moment and La has no magnetic moment.
The magnetic properties of amorphous materials alloyed with CO were investigated (Examples 2 and 3). As a result, G o
In the -S m system, soft magnetism was not obtained, and in the Co-La system, a coercive force of 30 e or less and a B s of 16,000 Gauss were obtained. This value exceeds the B s of 15000 Gauss for the Go-Zr system. From the above, it is presumed that Eu and Lu can similarly amorphize Co and obtain soft magnetic properties.

Table 1 Magnetic moments of rare earth elements (Ion is the value of trivalent ion) [Embodiments of the invention] The present invention will be explained in detail below.

Example 1 20 to 4 Y plates (4 x 4 x 1 mm) with a purity of 99.9% were placed on a CO target with a purity of 99.9% (4 inches in diameter above).
0 sheets, 99.9% purity W plate (4×4XIIm) from 0 to
A Co--Y(--W) film was sputtered on every 30 glass substrates with a diameter of 3 inches and a thickness of 5 m. The composition was changed by changing the number of each plate. Ar gas pressure is 5 x 1'O
-'Torr, and the input power was 37 kW/rrr. Bliss sputtering was carried out for 3 hours. It was a sputter-up method, and the glass substrate was directly attached with wax to a water-cooled baffle plate located 70 rm above the target. A unidirectional magnetic field was applied to the substrate by a pair of magnets. The structure of the film was examined by X-ray diffraction, and the magnetic properties were examined using a B-H meter and a vibrating sample magnetometer. The results are shown in Table 2.

Example 2 A 99.9% pure Sm plate (4X4X1rrn) and a 99.9% pure Ta plate (4X4X1nn) were placed on a 99.9% pure CO metal (diameter 4 inches). Sputtering was performed under the same conditions. The results are shown in Table 3.

Example 3 A 99.9% pure La plate (4x4xlrm) and a 99.9% pure Ta plate (4x4x1ma+) were placed on a 99.9% pure cot (4 inch diameter). Sputtering was performed under the same conditions. Its structure and magnetic properties are shown in Table 4.

Table 2 Magnetic properties of Go-Y-W alloy Table 3 Magnetic properties of Co-8m-Ta alloy Table 4 Co-La
-Magnetic properties of Ta-based alloy [Effect of the invention] According to the present invention, it is possible to provide a magnetic material for a magnetic core having a larger saturation magnetic flux density (15,000 to 16,000 Gauss) than conventional NiFe, Co--Zr, etc. A thin-film magnetic head capable of high-density recording can be realized.

[Brief explanation of drawings]

FIG. 1 is an external view of the thin film magnetic head, and FIG. 2 is a sectional view of the magnetic core of the thin film magnetic head. 1... Magnetic core, 2... Coil terminal, 3... Coil, 4... Board.

Claims (1)

[Claims] 1, Co_1_-_a_-_bM_aX_b, 0≦a, b≦0.1, 0.04≦a+b≦0.
1, where M is at least one of Y and La, and X is Ta, W, Nb, Mo, V, and Cr.
An amorphous high saturation magnetic flux density material comprising at least one of the following.