JPH04279011A - Nonmagnetic substrate for magnetic head - Google Patents

Abstract

PURPOSE:To obtain a nonmagnetic substrate for magnetic heads for vapor- depositing metallic magnetic films. CONSTITUTION:This nonmagnetic substrate for magnetic head is composed basically of CoO and NiO or NiO with at least one of the oxides of Sr, Ba, and Ra by 0.1-10wt.% of the said component. When such composition is used, the coefficient of thermal expansion and hardness of the substrate become nearly equivalent to those of a magnetic film structure in which the substrate is incorporated. Therefore, the occurrence of delamination and cracking in the magnetic film structure can be prevented. When the hardness is further improved, in addition, the shortening of the service life of magnetic heads and deformation, cracking, etc., of the nonmagnetic substrate can be suppressed and the wear resistance and durability of the heads can be improved.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nonmagnetic substrate for a magnetic head on which a metallic magnetic film is deposited.

0002

BACKGROUND OF THE INVENTION Conventionally, barium titanate, calcium titanate, alumina, etc. have been used for this type of application. However, since its coefficient of thermal expansion was significantly different from that of the magnetic film structure, the deposited magnetic film structure was likely to peel off, and the difference in coefficient of thermal expansion caused stress and cracks.

Furthermore, conventional materials have low hardness, and especially when a high coercive force tape (so-called metal tape) is used, the hardness and wear resistance of the nonmagnetic substrate are different from those of the magnetic film structure. There was a problem in that the friction generated by sliding with the magnetic tape caused uneven wear and the like, resulting in changes in magnetic properties. In particular, when the hardness is low, the disadvantages are that the life of the magnetic head is shortened or that the nonmagnetic substrate is deformed, cracked, or peeled off.

The present inventors have conducted research on oxide ceramics in order to solve the above-mentioned drawbacks, and have
It has already been disclosed that oxides having a basic composition of O or NiO are effective. (JP 01-287811, JP 02-168602, JP 01-214206) Furthermore, we investigated additives to improve hardness and density.
The basic composition is oO, NiO, and one or more of manganese oxide, titanium dioxide, alumina, and calcia at 0.1~
When adding 5 wt%, and when adding one or more of 1 to 5 wt% yttria, 0.1 to 1% titanium nitride, 0.3 to 2 wt% boron oxide, or 1 to 5 wt%
The effectiveness of adding wt% silicon dioxide was confirmed and these were disclosed. (JP 02-94408, JP 01-159622, JP 01-214208)

0
005]

[Means for Solving the Problems] In order to solve the above problems, the present inventors have developed a method using CoO and NiO or Ni.
As a result of further studies on additives whose basic composition is O, it was found that when 0.1 to 10 wt% of at least one of the oxides of Sr, Ba, and Ra was added to the composition, the above characteristics could be achieved. I have found something that satisfies me. Therefore, specifically, the object of the present invention is to have a thermal expansion coefficient close to that of a deposited magnetic film structure, a high Vickers hardness, and a structure that does not cause excessive chemical erosion reactions between other head constituent materials. There is no material to offer.

[0006]

[Structure of the Invention] That is, the present invention uses CoO and NiO or NiO as the basic composition, and adds Sr,
0.1 to 1 at least one of Ba and Ra oxides
Provided is a non-magnetic substrate for a magnetic head, characterized in that 0 wt % is added.

[0007]

DETAILED DESCRIPTION OF THE INVENTION In order to facilitate understanding of the present invention, the present invention will be explained specifically and in detail. The basic composition means an oxide of NiO alone or a composite oxide of NiO and CoO, for example, CoO/NiO (molar ratio) = 0/100 to 80/
20, more preferably CoO/NiO (molar ratio)=
3/97 to 60/40.

[0008] For the above composition, the present invention provides Sr, B
a, 0.1 to 10 at least one of the oxides of Ra
Add wt%. Oxides of Sr, Ba, and Ra are substances that improve sinterability, and addition of 0.1 wt% or more increases density and improves hardness and strength. In addition, the coefficient of thermal expansion is Ni
It is almost equivalent to O and CoO, and the coefficient of thermal expansion can be easily adjusted. However, if the amount added exceeds 10 wt%, precipitation occurs at grain boundaries, resulting in a decrease in hardness and strength. It is effective to add it alone or in combination with previously disclosed additives. It is desirable to adopt a combination that corresponds to the desired hardness and coefficient of thermal expansion.

Next, a method for manufacturing the substrate will be described. Weigh commercially available oxides as raw materials to obtain the desired composition,
Mix by ball mill. Mixing is carried out, for example, in a wet ball mill in ethanol for 10 to 30 hours. After drying, CI
P-molded and calcined at 850 to 1100°C in Ar, for example,
Next, it is crushed using a coarse crusher and sieved through a 100 to 200 μm sieve. The calcined powder is further treated, for example, in a wet ball mill in ethanol for 20 to 72 hours, and pulverized to 1 μm or less. After granulation, this is subjected to CIP molding, sintered at 1230 to 1400° C. in oxygen, for example, and then subjected to HIP treatment. HIP processing conditions are 80 to 120 MPa, 1
Preferably, the temperature is 200-1350°C for 1-2 hours.

[0010] It has been confirmed that the sintered body thus obtained has a dense, rock-salt-type structure, and is superior to conventional materials in that there is less friction caused by sliding of the tape and less chipping of edges. did it.

Examples of the present invention will be described below.

[Example 1] CoO/NiO (
The composition was adjusted to have a molar ratio of 35/65, and strontium oxide was mixed therein as an additive as shown in Table 1. Mixing was carried out in a wet ball mill in ethanol for 20 hours. This mixed powder was calcined at 1000° C. in Ar, and then ground in an ethanol wet ball mill for 40 hours. This pulverized powder was sintered at 1350° C. in oxygen after CIP molding. This was subjected to HIP treatment at 1250° C., 100 MPa, and 1 hour. The relative density of the sintered body was over 99%.

Table 1 shows the physical properties of the sintered body of this example. As physical property values, thermal expansion coefficient (α: μm/m° C.) and Vickers hardness (Hv) were selected.

[0013] As a comparative example, the physical property values are also shown when the basic composition is the same as that of barium titanate, which is a conventional material, but the amount of additives is changed.

[Table 1] * indicates a comparative example. The coefficient of thermal expansion is approximately determined by the basic composition, and is 13.8±0.2 μm/m° C. in the range of this example. This value is approximately equivalent to that of the magnetic film structure. Table 1 shows that the decrease in hardness is significant, so the amount added needs to be within 10 wt%.

[0014]

[Example 2] CoO/NiO (
The composition was adjusted to have a molar ratio of 35/65, and barium oxide was mixed therein as an additive as shown in Table 2. Mixing was carried out in a wet ball mill in ethanol for 20 hours. After calcining this mixed powder at 1000℃ in Ar,
The mixture was ground in a wet ball mill for 40 hours. This pulverized powder was sintered at 1350° C. in oxygen after CIP molding. This is 12
HIP treatment was performed at 50° C., 100 MPa, and 1 hour. The relative density of the sintered body was over 99%.

Table 2 shows the physical properties of the sintered body of this example. As the physical property values, the coefficient of thermal expansion and Vickers hardness were selected as in Table 1.

[0016] As a comparative example, the physical property values are also shown when the basic composition is the same as that of barium titanate, which is a conventional material, but the amount of additives is changed.

[Table 2] * indicates a comparative example. The coefficient of thermal expansion is approximately determined by the basic composition, and is 13.8±0.2 μm/m° C. in the range of this example. This value is approximately equivalent to that of the magnetic film structure. Therefore, from Table 2, it is necessary that the amount added be within 10 wt%.

[0017]

As explained above, (1) the non-magnetic substrate of the present composition can obtain properties almost equivalent to those of the magnetic film structure in terms of coefficient of thermal expansion and hardness. Therefore, peeling and cracking of the magnetic film structure can be significantly prevented.

(2) Furthermore, by increasing the hardness, it is possible to shorten the life of the magnetic head and suppress deformation and cracking of the non-magnetic substrate, which has the advantage that the head has particularly excellent wear resistance and durability. .

Claims (1)

[Claims] 1. For a magnetic head, characterized in that the basic composition is CoO and NiO or NiO, and 0.1 to 10 wt% of at least one of oxides of Sr, Ba, and Ra is added to the composition. Non-magnetic substrate.