JP2832863B2 - Non-magnetic ceramics for magnetic heads - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a non-magnetic ceramic for a magnetic head,
More specifically, the present invention relates to a non-magnetic ceramic used for a magnetic head such as a floppy disk device or a hard disk device, which is a peripheral device of a computer, and a video tape recorder.

2. Description of the Related Art Generally, a magnetic head used in a floppy disk device, an audio-visual device, or the like is configured by glass bonding of ferrite, which is a magnetic material, and ceramic, which is a nonmagnetic material. In the case of a thin-film magnetic head, a magnetic thin film is formed on a magnetic or non-magnetic ceramic substrate by vapor deposition or sputtering. Furthermore, the development of a multilayer head in which a metal magnetic film is narrowed by a non-magnetic ceramic substrate has been steadily developed.

2. Description of the Related Art In recent years, digital magnetic heads have been required to be smaller, have higher recording density, and have higher quality in accordance with technological changes to higher density recording of recording media.

Therefore, ferrite should be applied to the characteristics of recording media.
It is required to have a large saturation magnetic flux density. That is, in order for ferrite to have high saturation magnetic flux density magnetic properties, it must be manufactured in a composition region where the coefficient of thermal expansion is necessarily large. In the case of a thin film head,
High saturation magnetic flux density, high thermal expansion coefficient (130-140 × 10 ^-7 /
° C) and a metal magnetic thin film such as Permalloy or Sendust is formed on a ceramic substrate.

By the way, in the case where these dissimilar materials are manufactured by bonding, vapor deposition, or sputtering, the necessary conditions are to make the thermal expansion coefficients of the constituent materials close to each other and to minimize the distortion generated during joining. Become.

Conventionally, nonmagnetic ceramics that are integrally formed with such a magnetic material are CaTiO ₃ , BaTiO ₃ , Zn ferrite, Al ₂ O ₃
-TiL ceramics were used. However, the thermal expansion coefficient of these ceramics is 75-120 × 10 ^-7
It is very difficult to produce ceramics with a coefficient of thermal expansion of more than 130 × 10 ^-7 / ° C.

 In general, magnetic ceramics for magnetic heads are: 1) High density and few pores.

2) Excellent wear resistance.

3) Excellent workability.

4) The coefficient of thermal expansion is close to that of a magnetic material.

5) Large low efficiency.

6) Be physically and chemically stable.

Etc. are required.

[Means for Solving the Problems] In view of the above problems, the present invention has a large thermal expansion coefficient, a good wear characteristic, and good workability in order to adapt to a magnetic material having a large thermal expansion coefficient (α). It is intended to provide a good non-magnetic ceramic for a magnetic head.

The present invention focuses on the fact that the oxides MgO and NiO, which have a large thermal expansion coefficient, form a solid solution and form a stable uniform component. The thermal expansion coefficient is controlled by the composition ratio, and the mechanical strength and workability are excellent. High-density non-magnetic ceramics can be easily manufactured.

The present inventor first examined the composition ratio of MgO and NiO, which are the main components of the nonmagnetic ceramic material for a magnetic head of the present invention, and found that the coefficient of thermal expansion α ≧ 130 × 10 ^-7 / ° C Was obtained at 80 mol% or less. However, the MgO component
It was also found that when the content was less than 20 mol% (that is, the content of NiO exceeded 80 mol%), the magnetic permeability exceeded 1 and was unsuitable as a nonmagnetic ceramic. Α ≧ 130 × 10 ^-7 at 20 to 80 mol% MgO
Although sintering temperatures of 1400 ° C are possible, densification is insufficient at 1400 ° C, resulting in high porosity and low hardness, making it unsuitable as a ceramic material for magnetic heads.

The present inventors have found that these problems can be improved by adding TiO ₂ and adding one or more of Pr ₆ O ₁₁ , Tm ₂ O ₃ , Yb ₂ O ₃ and Lu ₂ O _3. I found That is, TiO
_The addition of ₂ increases the hardness and increases the sintering promotion effect and the crystal refinement effect of Pr ₆ O ₁₁ , Tm ₂ O ₃ , Yb ₂ O ₃ , Lu ₂
The porosity is improved by adding O ₃ .

In the above range, when TiO ₂ is less than 0.1 part by weight, the hardness is low, and when it exceeds 5 parts by weight, the thermal expansion coefficient is small. One or more of Pr ₆ O ₁₁ , Tm ₂ O ₃ , Yb ₂ O ₃ , Lu ₂ O ₃ is 0.
When the amount is less than 1 part by weight and when it exceeds 10 parts by weight, the porosity increases.

[Example] Hereinafter, an example of the present invention will be described.

First, a commercially available raw material _{MzO, TiO 2, Pr 6 O} 11, Tm 2 O 3, Yb 2 O
₃ , Lu ₂ O ₃ was weighed so as to have a composition ratio shown in Table 1, and mixed with a ball mill using alcohol as a dispersion medium. After drying, it is calcined in air at 1200 ° C for 2 hours.
It was pulverized again by a ball mill. The average particle size of the pulverized powder was about 1.2 μm. Further, 1% of a binder was added, granulation was carried out, molding was performed under a pressure of ² ton / cm ² , and sintering was performed at 1400 ° C. for 3 hours in the air. Next, a sintered body having a relative density of 97% or more is placed in an alumina crucible,
Hot isostatic pressing (HIP) was performed in an Ar gas atmosphere at a temperature of 1300 ° C., a pressure of 1000 kg / cm ² , and a holding time of 2 hours.

The coefficient of thermal expansion (100
(° C to 400 ° C), Vickers hardness (500g load), average particle size of resistance strength, porosity, and magnetic permeability. The permeability is φ10
A toroidal core of × φ6 × 2 mm was measured at a frequency of 1 kHz.

As is evident from the inventive examples of Samples Nos. 1 to 7 and the comparative examples of Samples Nos. 8 to 13, when MgO exceeds 80 mol% (No. 13), the coefficient of thermal expansion decreases and MgO becomes less than 20 mol%. % (No. 12), the magnetic permeability increases. When the TiO ₂ content is less than 0.1 part by weight (No. 11), when the decrease in hardness exceeds 5.0 parts by weight (No. 9), the thermal expansion coefficient decreases. Furthermore, Pr ₆ O ₁₁ ,
When one or more of Tm ₂ O ₃ , Yb ₂ O ₃ , and Lu ₂ O ₃ are less than 0.1 part by weight (Nos. 8 and 10), the porosity is large, the average particle size is large, and the hardness is accordingly increased. , The resistance strength is also reduced.
When it exceeded 10.0 parts by weight (No. 13), it was found that the porosity was large.

As described above, according to the present invention, 0.1 to 0.5 parts by weight of TiO _{2 was} added to 100 parts by weight of the main component composed of 20 to 80 mol% of MgO and the balance of NiO.
And one or more of Pr ₆ O ₁₁ , Tm ₂ O ₃ , Yb ₂ O ₃ , Lu ₂ O ₃ .
By adding 1 to 10 parts by weight, thermal expansion coefficient α> 130 ×
A high-density non-magnetic ceramic with a microstructure of 10 ^-7 / ° C and excellent mechanical properties was obtained.

[Effects of the Invention] As is clear from the above results, according to the present invention, high-density non-magnetic ceramics having a thermal expansion coefficient α> 130 × 10 ⁻⁷ / ° C., which has been difficult to manufacture conventionally, can be easily manufactured. It becomes possible.

In other words, it became an optimal material for joining MnZn ferrite having a high saturation magnetic flux density, and a metal magnetic thin film such as permalloy or sendust, and a highly reliable magnetic head could be manufactured.

Claims (1)

(57) [Claims] (1) containing 0.1 to 5 parts by weight of TiO ₂ with respect to 100 parts by weight of a main component composed of NiO, containing 20 to 80 mol% of MgO;
And at least one of Pr ₆ O ₁₁ , Tm ₂ O ₃ , Yb ₂ O ₃ and Lu ₂ O ₃
Non-magnetic ceramics for magnetic heads, characterized by containing 0.1 to 10 parts by weight.