JPH06231933A - Manufacture of junction ferrite - Google Patents

Abstract

PURPOSE:To acquire junction ferrite with satisfactory junction strength wherein single crystallization of polycrystalline ferrite whose core is single-crystal ferrite is restrained and the turbulence of an interface between a sing-crystal part and a polycrystalline part is reduced. CONSTITUTION:In a manufacturing method of junction ferrite comprised of single-crystal manganese-zinc ferrite and polycrystalline ferrite, a manganese-zinc ferrite thin film having film thickness of 10nm or more and 100nm or less is intervened in a junction surface between the single-crystal ferrite and the polycrystalline ferrite and is formed integral at a temperature of 1200 deg.C or higher and 1250 deg.C or lower.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bonded ferrite used, for example, in a composite magnetic head or the like.

[0002]

2. Description of the Related Art Conventionally, in a magnetic head, for example, a video head, manganese-based material having high output and excellent wear resistance is used.
Zinc single crystal ferrite has been used for magnetic cores. However, as the image quality of VRT has been improved in recent years, the recording frequency band has been increased in frequency, resulting in a decrease in reproduction output. Further, since the sliding noise level is high in the head having the single-crystal ferrite in the magnetic core, the reproduction output is decreased by the S / N ratio.
This has led to a drop in the ratio.

In recent years, in order to improve the S / N ratio, a magnetic head having a bonded ferrite material in which a single crystal ferrite and a polycrystalline ferrite are bonded and integrated in a magnetic core is used. A magnetic head that has this bonded ferrite material in the magnetic core is a single crystal ferrite on the front gap side,
It has a structure in which polycrystalline ferrite is arranged on the back gap side, and while the output and wear resistance are the same as those of a magnetic head having a single crystal ferrite simple substance in the magnetic core, the sliding noise level is low and the high S / N ratio is high. There is a feature that it can be obtained.

[0004]

A magnetic head having a bonded ferrite material in the magnetic core has a characteristic that the sliding noise level is lower than that of a magnetic head having a single crystal ferrite simple substance in the magnetic core. The effect depends on the position of the interface between the single crystal and the polycrystal in the magnetic head, and the larger the volume occupied by the single crystal, that is,
The sliding noise reduction effect becomes smaller as the interface position becomes closer to the back gap side.

Conventionally, the bonded ferrite has been obtained by subjecting a single crystal ferrite and a polycrystalline ferrite block to mirror finishing,
The mirror surface portions are brought into contact with each other and heat-treated while applying a pressure of several hundred kPa to the bonding interface, so that they are integrated by bonding. A single-crystallized layer of polycrystalline ferrite having a size of several tens of μm is formed. Since this single crystallization often progresses nonuniformly, the interface between the single crystal part and the polycrystal part is disturbed. Due to this interface disorder, it is difficult to control the interface position between the single crystal part and the polycrystalline part in the magnetic head. It is difficult to bring out the sliding noise reduction effect.

As a method for suppressing the single crystallization of the polycrystalline ferrite, the present applicant has proposed that the single crystal ferrite and the polycrystalline ferrite are bonded and integrated via an oxide magnetic thin film (Japanese Patent Laid-Open No. 63-63). 14311). However, this effect of suppressing single crystallization becomes smaller as the film thickness becomes thinner, and as the film thickness becomes thicker, vacancies are generated in the film portion at the bonding interface, resulting in a decrease in bonding strength. Due to this decrease in the bonding strength, peeling occurs from the interface between the single crystal portion and the polycrystalline portion in the head chip processing step, which lowers the yield and also lowers the reliability of the magnetic head.

[0007] Therefore, the present applicant further stipulates that the sliding noise reduction effect and sufficient bonding strength can be obtained by defining the thickness of the single-crystallized layer of polycrystalline ferrite to be 10 μm or more and 30 μm or less in order to solve the above problems. Was proposed (Japanese Patent Laid-Open No. Hei 2
-61808). However, due to recent advances in head processing technology, it is possible to more precisely control the interface position between the single crystal portion and the polycrystalline portion in the head, and to further reduce sliding noise, the single crystal portion and the polycrystalline portion can be reduced. It is necessary to make the interface of the part flatter.

Therefore, the present invention has been proposed in view of such an actual situation, and suppresses single crystallization of polycrystalline ferrite, reduces disturbance of the interface between the single crystal portion and the polycrystalline portion, and An object is to provide a bonded ferrite having a sufficient bonding strength.

[0009]

Means for Solving the Problems As a result of earnest studies, the inventors of the present invention have not achieved the above-mentioned goals, and as a result, in a bonding ferrite composed of a manganese-zinc single crystal ferrite and a polycrystalline ferrite, an oxide is present at the bonding interface. Manganese-zinc ferrite thin film as a magnetic thin film 10 nm or more 100 nm
By interposing with the following film thickness and joining and unifying at a temperature of 1200 ° C. or more and 1250 ° C. or less, single crystallization of polycrystalline ferrite that occurs at the time of joining and unifying by hot pressure treatment is suppressed, It was found that the disorder of the interface between the crystal part and the polycrystal part was reduced, and sufficient bonding strength was obtained.
The present invention has been completed.

That is, according to the present invention, in a bonded ferrite composed of manganese-zinc single crystal ferrite and polycrystalline ferrite, a manganese-zinc ferrite thin film having a film thickness of 10 nm or more and 100 nm or less is formed at the bonding interface between the single crystal ferrite and the polycrystalline ferrite. It is characterized in that it is made to intervene and is joined and integrated at a temperature of 1200 ° C. or more and 1250 ° C. or less.

[0011]

[Function] In the bonding ferrite composed of manganese-zinc single crystal ferrite and polycrystalline ferrite, manganese is bonded to the bonding interface between the single crystal ferrite and the polycrystalline ferrite.
By interposing a zinc ferrite thin film with a film thickness of 10 nm or more and 100 nm or less and joining and unifying it at a temperature of 1,200 ° C. or more and 1,250 ° C. or less, single crystal ferrite generated at the time of joining and unifying by hot pressure treatment Single crystal crystallization of polycrystalline ferrite due to solid-state reaction as nuclei is suppressed,
Disturbance at the interface between the single crystal part and the polycrystalline part is reduced,
Sufficient bonding strength can be obtained.

[0012]

EXAMPLES The present invention will be described below with reference to specific examples, but it goes without saying that the present invention is not limited to these examples. Fe ₂ O ₃ 52.5 mol%, Zn
A single crystal ferrite having a composition of O 19.5 mol% and MnO 28.0 mol% was prepared by the Bridgman method. In addition, polycrystalline ferrite having the above composition is usually wet mixed,
After drying, calcination, pulverization, granulation, and molding, sintering was performed under conditions of a temperature of 1250 ° C. and a holding time of 5 hours in consideration of equilibrium oxygen pressure.

This single crystal and polycrystalline ferrite is
Processed to m x 10 mm x 3 mm dimensions, 30 mm each
One side of the surface of × 10 mm was mirror-finished. Fe ₂ O is added to the mirror-polished surface of the single-crystal ferrite that has been mirror-polished.
₃ 50.0 mol%, ZnO 25.0 mol%, MnO 2
10, 50, 10 by high frequency magnetron sputtering method using a target composed of 5.0 mol% composition
A manganese-zinc ferrite thin film having a thickness of 0, 200 or 300 nm was formed.

After that, the manganese-zinc ferrite thin film surface of the single crystal ferrite and the mirror surface portion of the polycrystalline ferrite are brought into contact with each other, and a pressure of 0.5 MPa is applied from the normal line direction of the contact surface under N ₂ atmosphere at 1150 ° C., 1200. ℃, 12
The temperature was maintained at 50 ° C. and 1300 ° C. for 2 hours to produce a bonded ferrite composed of single crystal ferrite and polycrystalline ferrite.

Further, the single-crystal ferrite and the mirror-polished surface of the polycrystalline ferrite were brought into direct contact with each other without interposing the manganese-zinc ferrite thin film, and a bonded ferrite was produced under the same conditions as the above hot press treatment conditions and made a comparative example. . As shown in FIG. 3, these bonded ferrites were cut at the central portion in the width direction of 10 mm, the cut surface was mirror-finished, and then the porosity of the bonded interface portion was measured with a microscope.

The porosity referred to here is the ratio of voids to the length of the bonding interface. Further, the sample after the porosity measurement was etched with concentrated hydrochloric acid, and the average value and distribution range of the single crystallized layer thickness of the polycrystalline ferrite were measured with a polarization microscope.

From the above measurement results, the average value of the film thickness of the manganese-zinc ferrite thin film and the thickness of the single crystallized layer (hereinafter, referred to as the average single crystallized layer thickness) at each hot pressure treatment temperature, the single crystallized layer Table 1 shows the relationship between the maximum value of thickness (hereinafter referred to as the maximum single crystallized layer thickness) and the porosity of the bonded interface portion. From Table 1,
Looking at the single crystallized layer thickness, the maximum single crystallized layer thickness is 20 μm or more and the average single crystallized layer thickness is 5 at the processing temperature of 1300 ° C.
This value is larger than μm, which is a large value as compared with other processing temperatures, and it is understood that the effect of interposing the manganese-zinc ferrite thin film at the bonding interface is not sufficiently exhibited at the processing temperature of 1300 ° C.

Further, looking at the porosity of the bonding interface, the value at the processing temperature of 1150 ° C. is higher than the other processing temperatures. This is because, in addition to the point-like voids at the bonding interface, which are observed at 1200 ° C. or higher at a processing temperature of 1150 ° C., the processing temperature is low, resulting in defective bonding and linear peeling. . From the above, the hot pressing treatment temperature at which the effect of suppressing single crystallization of the manganese-zinc ferrite thin film is sufficiently obtained and the bonding failure does not occur is 1200.
This means that the temperature is not lower than 0 ° C and not higher than 1250 ° C.

Next, the hot pressure treatment temperature is 1200 ° C. and 1
The joint strength of the 250 ° C. sample was measured by a four-point bending test. The four-point bending test, as shown in FIG.
A 0.50 mm × 0.33 mm × 4 mm test piece was installed so that the bonding interface was at the center of the upper support roll and the lower support roll of the jig, and the crosshead speed was 0.1 mm / mi.
n. Here, the test number is 2 for each sample.
It was set to 0 pieces. The surface of the test piece was mirror-finished.

The measurement results are shown in FIGS. 1 and 2 as a diagram showing the relationship between the thickness of the manganese-zinc ferrite thin film and the measured value of the single crystallized layer thickness.

From FIGS. 1 and 2, it is possible to obtain a bonding strength almost equal to the bonding strength of the bonding ferrite in which the thickness of the manganese-zinc ferrite thin film is 100 nm or less and the manganese-zinc ferrite thin film does not intervene. It can be seen that single crystallization of polycrystalline ferrite is significantly suppressed when the thickness is 10 nm or more. Regarding the bonding strength, it decreases corresponding to the increase in the porosity shown in Table 1, and it is clear that the increase in the porosity at the bonding interface leads to the decrease in the bonding strength.

From the above results, the thickness of the manganese-zinc ferrite thin film interposed at the bonding interface is 10 nm or more, 1
00 nm or less and the hot pressurizing temperature is 1200 ° C
It can be seen that by setting the temperature to 1250 ° C. or lower, it is possible to sufficiently suppress the single crystallization of the polycrystalline ferrite and obtain a bonding strength almost equal to the bonding strength of the bonded ferrite in which the manganese-zinc ferrite thin film is not interposed.

[0023]

[Table 1]

[0024]

As is apparent from the above description, in the present invention, when the manganese-zinc single crystal ferrite and the polycrystalline ferrite are joined and integrated by the hot press treatment through the manganese-zinc ferrite thin film, The film thickness of the thin film is 1
0 nm or more and 100 nm or less, and the processing temperature is 120
By setting the temperature to 0 ° C. or higher and 1250 ° C. or lower, single crystallization of the polycrystalline ferrite centered on the single crystal ferrite is suppressed,
Disturbance at the interface between the single crystal part and the polycrystalline part is reduced,
It is possible to obtain a bonded ferrite having a bonding strength almost the same as the bonding strength of the bonded ferrite without interposing the manganese-zinc ferrite thin film. Therefore, by using the bonded ferrite according to the present invention, it is possible to obtain a magnetic head which is stable with a small variation and has a larger sliding noise reduction effect and which is highly reliable in bonding strength. Further, in the head chip processing step, peeling from the interface between the single crystal portion and the polycrystalline portion is eliminated, and the yield is improved.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the film thickness of a manganese-zinc ferrite thin film, the thickness of a single crystallized layer of a bonded ferrite material, and the bonding strength at a hot pressing temperature of 1250 ° C.

FIG. 2 is a diagram showing the relationship between the film thickness of a manganese-zinc ferrite thin film, the thickness of a single crystallized layer of a bonded ferrite material, and the bonding strength at a hot pressurizing temperature of 1200 ° C.

FIG. 3 is a perspective view showing an example of a bonded ferrite composed of a single crystal ferrite and a polycrystalline ferrite according to the present invention, and a cut portion for measuring the porosity of the bonded interface and the thickness of the single crystallized layer.

FIG. 4 is a schematic diagram showing a jig and a sample installation position for a four-point bending test.

[Explanation of symbols]

 3-1 Single crystal ferrite 3-2 Polycrystalline ferrite 3-3 Manganese-zinc ferrite thin film 3-4 Cut portion for measuring single crystallized layer thickness 4-1 Single crystal ferrite 4-2 Polycrystalline ferrite 4-3 Bonding Interface 4-4 Test piece 4-5 Sphere (Sφ2mm) 4-6 Guide 4-7 Load platform 4-8 Upper support roll (φ0.66mm) 4-9 Lower support roll (φ0.66mm) 4-10 Support platform

Claims (1)

[Claims] 1. A method for producing a bonded ferrite comprising a manganese-zinc single crystal ferrite and a polycrystalline ferrite, wherein a manganese-zinc ferrite thin film having a thickness of 10 nm or more is formed at a bonding interface between the single crystal ferrite and the polycrystalline ferrite.
Intercalated with a film thickness of 00 nm or less, 1200 ° C. or more and 1250
A method for producing a bonded ferrite, which comprises integrally bonding at a temperature of ℃ or less.