JPS5935432B2 - Heat treatment method for amorphous magnetic materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heat treatment method for an amorphous magnetic material, and is intended to improve the magnetic properties of the amorphous magnetic material.

In recent years, materials have been rapidly cooled from a molten state to solidify.
Advances in technology for obtaining amorphous ribbons have made it possible to produce amorphous magnetic materials having a constant ribbon shape, and research into its application has become active.

Since the amorphous magnetic material obtained by the ultra-quenching method has no crystal magnetic anisotropy, it is expected to exhibit excellent soft magnetism. However, the magnetic properties of an amorphous magnetic material immediately after being rapidly solidified are not so good, and heat treatment is essential to significantly improve the properties. When performing this heat treatment, a material with extremely high magnetic permeability is required, and if the crystallization temperature Tx is higher than the Curie point Tc, T
It is known that the desired magnetic properties cannot be obtained unless heat treatment is performed at a temperature TA of x or lower, followed by rapid cooling below Tc and the temperature is returned to room temperature. On the other hand, since the amorphous material itself is in a supercooled metastable state, it has instability in that its magnetic properties change over time. This instability is T
By heat-treating the amorphous magnetic material at a heat treatment temperature TA as high as possible that satisfies the condition A<Tx, and cooling it to room temperature as slowly as possible without crystallization,
It became clear that improvements could be made (Patent Application 1986-777)
No. 82). Therefore, in the heat treatment process, if a high magnetic permeability material is to be obtained, the material below Tc must be rapidly cooled, while if stability is to be improved, the material below TA must be slowly cooled. In other words, To(TA
TA can be set so that <Tx (1). This was only true for amorphous magnetic materials having To and Tx. However, (1
) There are few amorphous magnetic materials that satisfy the conditions shown in the formula, and in general, many have Tc and Tx close to each other. In particular, in an amorphous alloy system mainly composed of Co, which has extremely high magnetic permeability and has extremely low magnetostriction and is currently being considered for application to magnetic heads, the saturation magnetic flux density Bs is approximately proportional to its Curie point Tc. It is known that the crystallization temperature Tx tends to be almost inversely proportional to the crystallization temperature Tx. Therefore, Bs
The higher the composition, the closer Tc and Tx become, and when Bs is about 9500 Gauss, Tc and Tx match. If it exceeds this value, the reverse occurs and Tc>Tx, and the heat treatment conditions as shown in equation (1) are no longer satisfied. Therefore, it has been impossible to obtain an amorphous alloy with Bs higher than 10,000, which has good stability and high magnetic permeability, by conventional heat treatment. This situation is shown in a typical zero-magnetostrictive amorphous alloy (Fe4.
6cO7O. 4)X/75 (Sil2.5Bl2.5)
(100-X)/25 is shown in FIGS. 1 and 2.

Among the compositions with a magnetic permeability μ of 10,000 or more at 1 kHz that can be applied to audio magnetic heads etc. in consideration of practicality, the highest B8 has a BsZ9OOO Gauss, as is clear from Figure 2. It was hot. Moreover, with this composition, as can be seen from Figure 1, Tc. l! :． Tx
are extremely close to each other, and in order to obtain high magnetic permeability, rapid cooling treatment such as rapid cooling in water is required after heat treatment. Therefore, it has been impossible to improve the stability of magnetic properties by slow cooling after the heat treatment as described above. The present invention solves these problems and provides a heat treatment method that makes it possible to obtain an amorphous magnetic material with high magnetic flux density, high magnetic permeability, and good stability in magnetic properties. In particular, Tc>T, which conventionally could not improve magnetic permeability by heat treatment.
This is extremely effective for the amorphous magnetic material x.

Conventionally, when a magnetic field is applied in one direction within the plane of the ribbon, the static magnetic properties are improved and the residual magnetic flux density Br, called the squareness ratio, is improved.
It is known that the ratio between Bs and the saturation magnetic flux density Bs is close to 1. However, this method is not effective in improving the magnetic permeability in alternating current, and on the contrary, only materials with low initial magnetic permeability and poor level characteristics, in which the magnetic permeability μ is highly dependent on the measured magnetic field, are obtained. This is shown in FIG. On the other hand, heat treatment in a rotating magnetic field is effective in improving magnetic permeability (Japanese Patent Application No. 54-19
No. 209).

However, this method prevents the characteristic deterioration that occurs when a processing step is unavoidably carried out at a temperature below TO after improving the properties of an amorphous material where Tc<Tx by ordinary heat treatment at a temperature TA above Tc and below Tx. However, a large increase in magnetic permeability cannot be obtained by heat treatment in a rotating magnetic field alone. Specifically, as shown in Figure 3, this heat treatment method increases magnetic permeability while maintaining the level characteristics immediately after solidification, so when the measurement magnetic field is large, extremely high magnetic permeability can be obtained. A very high initial permeability cannot be obtained. Furthermore, heat treatment in a perpendicular magnetic field is similar to heat treatment in a rotating magnetic field described above, after the characteristics are improved by normal heat treatment under the condition of Tc < TA < Tx, the characteristics are improved in the subsequent processing step below Tc. Although this heat treatment method is extremely effective in preventing deterioration or restoring properties once deteriorated, it is difficult to obtain high magnetic permeability by using this heat treatment method alone for alloys where Tc>Tx. However, the advantageous feature of this heat treatment method is that the level area becomes very flat as shown in FIG. Heat treatment in a rotating magnetic field alone cannot significantly improve properties, and only when combined with normal heat treatment, which is performed on an amorphous magnetic material that satisfies the condition Tc<Tx, at a treatment temperature TA where Tc<TA<Tx. It is extremely effective. Therefore, in an amorphous magnetic material where Tc≧Tx, the magnetic properties cannot be improved by normal heat treatment. Even if such a material is subjected to a combination of ordinary heat treatment and heat treatment in a rotating magnetic field or heat treatment in a perpendicular magnetic field, the characteristics will not be improved. On the other hand, if these processes are performed separately at T
Even if it is applied to a material where c>Tx, the characteristics will not be improved much. Figure 4 shows an amorphous alloy (Fe2.5cO7l.5Mn3)8 with extremely low magnetostriction where Tc>Tx (=420°C).
'77When Si4Bl6 is heat-treated in a rotating magnetic field and a perpendicular magnetic field, 1kHz, 3×10
The dependence of magnetic permeability on heat treatment temperature at -3 oersted is shown. As can be seen from the experimental data, both were at 200℃.
The characteristics improve slightly at temperatures near that temperature, but there is not much improvement at higher temperatures, and as a matter of course, the TA above Tx
The characteristics deteriorate rapidly. However, experiments have revealed that by combining heat treatment in a perpendicular magnetic field and heat treatment in a rotating magnetic field, the AC effective magnetic permeability of an amorphous magnetic material is significantly improved.

Using the same sample used in the experiment shown in Figure 4,
An experiment was conducted in which heat treatment in a perpendicular magnetic field and heat treatment in a rotating magnetic field were combined, and the resulting changes in the level characteristics of magnetic permeability at 1 kHz are shown in FIGS. 5 and 6. As shown in these figures, it was found that by combining the heat treatment methods in both magnetic fields, a significant improvement in magnetic properties could be achieved that could not be obtained by heat treatment in only one magnetic field. FIG. 7 shows the dependence of magnetic permeability on processing temperature. The table below shows a comparison between various amorphous alloys with different Tc and Tx subjected to the conventionally known heat treatment method and the case where the heat treatment method of the present invention is applied. The results of an accelerated test of holding the sample at 70° C. for 1000 hours to examine the thermal stability of magnetic permeability are also shown. From the results shown in the table above, Tc<(T・
For the sample x, the temperature TA such that Tc<<TA<Tx
If the material is heat-treated and then cooled in air, the magnetic permeability and stability will be improved at the same time, so that preferable magnetic properties can be obtained without using the heat treatment method of the present invention.

On the other hand, for the sample where TO≦Tx, Tc≦TA<Tx
If the material is heat treated at a temperature TA and then quenched in water, the magnetic permeability can be improved, but the stability is not good. Furthermore, those that are air-cooled after treatment have good stability, but have the disadvantage of low magnetic permeability. It can be seen that for samples having such Tc and Tx, the heat treatment method of the present invention is superior to the conventional method in terms of magnetic permeability stability. Next, for a sample where Tc>Tx, it is impossible to improve the magnetic permeability by ordinary heat treatment in a non-magnetic field, no matter how TA is selected. In addition, in heat treatment in a rotating magnetic field or heat treatment alone in a perpendicular magnetic field, as shown in Figure 4,
Although the magnetic properties are slightly improved by heat treatment in the vicinity, the degree of improvement is small, and the subsequent thermal stability is also poor due to the low heat treatment temperature.
It can be seen that by subjecting such a sample to the magnetic field heat treatment of the present invention, the magnetic properties are greatly improved and the subsequent stability is also favorable. From the above, the heat treatment method in a magnetic field of the present invention improves the magnetic properties of amorphous magnetic materials, including their stability, and is particularly effective for amorphous magnetic materials where TO≧Tx. .

[Brief explanation of the drawing]

Figure 1 shows the proportion of transition metals in an amorphous alloy and one point T.
Figure 2 shows an example of the relationship between the Cl crystallization temperature Tx and the saturation magnetization δ (Emu/g). A diagram showing an example of the relationship between the highest effective magnetic permeability μe1 and the saturation magnetic flux density Bs, Figure 3 is Tc=5500C1Tx=420℃
The magnetic permeability at 1 kHz of an amorphous alloy subjected to heat treatment in a unidirectional magnetic field in the plane of the ribbon, heat treatment in a magnetic field perpendicular to the plane of the ribbon, and heat treatment in a rotating magnetic field in the plane of the ribbon A diagram showing the level characteristics, Figure 4 is Tc = 550°C, T
Figure 5 shows the dependence of magnetic permeability on treatment temperature when an amorphous alloy with x = 420°C is heat treated in a rotating magnetic field and in a perpendicular magnetic field. Figure 6 shows how permeability is improved when
The figure shows the improvement in magnetic permeability when heat treatment is performed in a vertical magnetic field and then heat treatment in a rotating magnetic field. Figure 7 shows the improvement in magnetic permeability when heat treatment in a vertical magnetic field and heat treatment in a rotating magnetic field are combined. It is a figure which shows the processing temperature dependence of the magnetic permeability of -3 Oersted.

Claims (1)

[Scope of Claims] 1. A step of heat treating an amorphous magnetic material having a ribbon shape at a temperature below its crystallization temperature while applying a magnetic field perpendicular to the surface of the ribbon; Amorphous magnetic material,
1. A method for heat treatment of an amorphous magnetic material, comprising the step of heat treatment while applying a rotating magnetic field within the plane of the ribbon at a temperature lower than its crystallization temperature. 2. The method for heat treatment of an amorphous magnetic material according to claim 1, wherein the Curie point of the amorphous magnetic material is higher than its crystallization temperature.