JPH0567508A - Nonmagnetic substrate for magnetic head - Google Patents

Abstract

PURPOSE:To provide a nonmagnetic substrate for magnetic heads on which a metallic magnetic film is vapor-deposited and which is composed basically of CoO and NiO or NiO containing ZrO2 (0.5-7wt.%) and improved in sinterability. CONSTITUTION:This nonmagnetic substrate for magnetic heads is composed basically of CoO and NiO or NiO containing ZrO2 (0.5-7wt.%) and a sintering assistant, namely, Al2O3 by 0.1-2wt.%. When such composition is used, a sintered body which is compact and has a stable transverse strength and fine and uniform crystal grain size can be obtained. Therefore, the economy of this nonmagnetic substrate can be improved when the substrate is manufactured from such sintered body, because the occurrence of chipping can be reduced and, accordingly, the yield, etc., can be improved at the time of manufacturing the substrate from the sintered body.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a non-magnetic substrate for a magnetic head for depositing a magnetic film.

[0002]

2. Description of the Related Art Conventionally, barium titanate, calcium titanate, alumina and the like have been used for non-magnetic base applications for this type of magnetic head. However, since the coefficient of thermal expansion was largely different from that of the metallic magnetic film structure, the vapor-deposited magnetic film structure was easily separated from the substrate, and stress caused by the difference in coefficient of thermal expansion sometimes caused cracks. It was

Further, conventional non-magnetic substrate materials have low hardness, and particularly when a high coercive force tape (so-called metal tape) is used as a magnetic recording medium, a magnetic film structure (hardness Hv = 600 to 800). ) And sliding and friction with a magnetic tape having different hardness and wear resistance cause uneven wear on the non-magnetic substrate, resulting in a change in the magnetic characteristics of the magnetic film structure. In particular, when the hardness of the non-magnetic substrate is low, the uneven wear of the magnetic film structure is remarkable, the life of the magnetic head is shortened, and the defects such as deformation, cracking and peeling of the non-magnetic substrate are remarkable. It was

The present inventors have advanced research on oxide-based ceramics in order to solve the above-mentioned drawbacks, and have conducted research on CoO and Ni.
Oxide having a basic composition of O or NiO is already effective, and its composition has already been disclosed in Japanese Patent Laid-Open No. 1-287811.
JP-A-2-168602 and JP-A-1-21420
No. 6 discloses the composition of the non-magnetic substrate. In addition, we examined additives to improve hardness and density, and
O, NiO as a basic composition, MnO, TiO ₂ , Al
Composition containing 0.1 to 5 wt% of one or more of ₂ O ₃ and CaO, and 1 to 5 wt% of Y ₂ O ₃ , 0.1 to 1%
Of TiN and 0.3 to ₂ wt% of B ₂ O ₃ added at least one kind or 1 to 5 wt% of SiO ₂ is effective as a magnetic head substrate and the additive is expected. It has been confirmed that the above effects are provided and these have been disclosed (Japanese Patent Application Laid-Open No. 02-94408, Japanese Patent Application Laid-Open No. 01-159622, Japanese Patent Application Laid-Open No. 01-214208).
).

[0005]

[Patent Document 1] Japanese Patent Application Laid-Open No. 2-15
No. 4307 discloses NiO and CoO or N.
When iO is used as the basic composition, CoO is 2
5-80 mol%, MO 0-50 mol%, XO ₂ 5-
Non-magnetic substrate material for a magnetic head characterized by containing 20 mol% (where M is at least one of Ni and Mn,
As X, at least one of Yi, Zr, and Hf) is disclosed. However, since the amount of ZrO ₂ added in this composition exceeds 5 mol% (8 wt%), the coefficient of thermal expansion of the non-magnetic material is 10.0 to 12.5 μm / m ° C., and the coefficient of thermal expansion of the metallic magnetic film. Since it becomes much smaller and problems such as deformation and cracking due to the difference in thermal expansion occur, a material corresponding to the magnetic film structure having a coefficient of thermal expansion higher than that has been required. Therefore, it is an object of the present invention to specifically provide a non-magnetic substrate material having a coefficient of thermal expansion of 12.5 to 15.0 μm / m ° C. and a high Vickers hardness.

[0006]

That is, the present invention is based on CoO
As a result of further studying the additive of NiO or NiO or NiO to the basic composition, ZrO was added to the basic composition.
It has been found that the desired characteristics are satisfied by adding 0.1 to 7 wt% of at least one of ₂ and HfO ₂ . In addition, ZrO ₂ satisfies the desired properties with both unstabilized zirconia and partially stabilized zirconia.
It has been found that the latter fulfills even better properties.

That is, in the present invention, the basic composition is CoO and NiO or NiO, and 0.1% of at least one of ZrO ₂ and HfO ₂ is added to 100 wt% of the composition.
Provided is a non-magnetic substrate for a magnetic head, which is characterized by adding ˜7 wt%. The present invention also provides a magnetic substrate for a magnetic head, wherein the ZrO ₂ is partially stabilized zirconia.

In order to facilitate understanding of the present invention, the structure of the present invention will be described specifically and in detail below. The basic composition is Ni
O means a single oxide or a composite oxide of NiO and CoO, and the composition of the composite is, for example, CoO / NiO (molar ratio).
= 1/99 to 80/20, and more preferably CoO /
NiO (molar ratio) = 3 / 97-60 / 40. The composition is 100 wt%, and 0.1 to 7 wt% of at least one of ZrO ₂ and HfO ₂ is added thereto. ZrO ₂ and HfO ₂ are substances having an effect of suppressing grain growth, and prevent coarsening of crystal grains of the sintered material. Addition of 0.1 wt% or more of this substance suppresses the particle size and improves the hardness. However, since the coefficient of thermal expansion is lower than that of NiO and CoO, it is desirable to control the addition amount within 7 wt%. The addition amount is preferably 1 wt% to less than 3 wt%.

The ZrO ₂ used is preferably partially stabilized. This is because the change in physical properties due to the phase transformation of ZrO ₂ is not preferable for its wear resistance. That is, ZrO ₂ undergoes a martensitic transformation from monoclinic to tetragonal at around 1170 ° C. when the temperature rises,
When the temperature is lowered, the reverse transformation occurs at 900 to 1000 ° C. During this transformation from tetragonal to monoclinic, a large change in volume occurs, which affects the sintering characteristics. The substance added to suppress this phase transformation is a stabilizer. The partially stabilized one is more preferable because the amount of the stabilizer is smaller than that of the stabilized one. This is because the addition of an excessive amount of stabilizer may deteriorate the substrate characteristics. As the stabilizer, it is preferable to add 1 to 17 mol% of at least one or more of yttrium oxide, calcium oxide, magnesium oxide, and cerium oxide with respect to the total amount of ZrO ₂ and the stabilizer.

Next, a method of manufacturing the substrate will be described. Each commercially available oxide is used as a raw material, weighed to have a desired composition, and mixed by a ball mill. The mixing is carried out, for example, in a wet ball mill in ethanol for 10 to 30 hours. After drying, the mixed powder is subjected to CIP molding, and the green compact is molded in Ar gas, for example
It is calcined at 50 to 1100 ° C., then the calcined body is crushed using a coarse crusher, and sieved with a 100 to 200 μm sieve.

The calcined powder is further treated with a wet ball mill in ethanol for 20 to 72 hours, and finely pulverized to 1 μm or less. The finely pulverized powder is granulated and then subjected to CIP molding, for example, sintered at 1230 to 1400 ° C. in an O ₂ atmosphere, and then subjected to HIP molding. The HIP processing condition is that the pressure is 80 to 120M.
Pa, temperature is 1200 to 1350 ° C., treatment time is 1 to 2
Time is desirable. The sintered body obtained in this manner has a dense and rock-salt type structure, is less likely to cause friction due to the sliding of the tape, and is not damaged at the edge portion, and is superior to conventional materials. Examples of the present invention will be described below.

[0012]

【Example】

Example 1 Using CoO and NiO as raw materials, a CoNiO ₂ composition (Co
The blending amounts were adjusted and mixed so that O / NiO (molar ratio) = 50/50). The obtained mixture was calcined in Ar gas at 1000 ° C., and then pulverized with a wet ball mill using ethanol for 22 hours. Yttria-stabilized ZrO ₂ (3 mol% yttria) was added to this pulverized powder in the ratio shown in Table 1, mixed, and CIP-molded, and then in an O ₂ atmosphere.
Sintered at 50 ° C. The obtained sintered body was heated at 1250 ° C. for 10
HIP treatment was performed under the conditions of 0 MPa and 1 hour. HI
The relative density of the P-treated sintered body was a value exceeding 99%. The Vickers hardness (Hv) and the coefficient of thermal expansion (α: μm / m ° C .- (measured in a temperature range of 100 to 400 ° C.)) of the sintered body are shown in Table 1. In the table, barium titanate of Comparative Example is used. properties were also shown. Further, it was confirmed that .ZrO ₂ to ZrO ₂ is also shown together in the case of more than 8 wt%, the thermal expansion ratio is too small for more than 8 wt%. the ZrO
₂ Without addition, the hardness (Hv) is as low as 650, which is not preferable. It was also confirmed that barium titanate has a too small coefficient of thermal expansion.

[0012]

[Table 1]

Example 2 CoO and NiO were used as raw materials and adjusted so that CoO / NiO (molar ratio) = 35/65 composition, and yttria-stabilized ZrO ₂ (3 mol% yttria) was added to this composition (100 wt%). 2 wt% was added and mixed. Mixing
It was carried out for 20 hours with a wet ball mill using ethanol. The mixed powder was calcined in Ar gas at 1000 ° C. and then pulverized with a wet ball mill using ethanol for 40 hours. After crushing the crushed powder into CIP, 135 in an oxygen atmosphere
Sintered at 0 ° C. This is 1250 ℃, 100MPa, 1
HIP processing was performed under the conditions of time. The relative density of the HIP-treated sintered body was a value exceeding 99%.

As a comparative example, the same basic composition (1
Yttria-stabilized ZrO ₂ was not added to (00 wt%), but alumina 2 wt% and yttria 2 wt% were added instead, and sintering was performed under the same conditions as in the example to produce a HIP-treated sintered body. The relative density of the sintered body is 99
It was a value exceeding%. The coefficient of thermal expansion of these sintered bodies was measured. As a result, 13.8 was obtained for each composition containing alumina, yttria, and yttria-stabilized zirconia.
Values of 14.2 and 14.4 (μm / m ° C.) were obtained.

Next, these sintered bodies were processed into a head shape without mounting the magnetic film structure, and the commercial VTR deck was mounted on a test VTR deck modified for a commercially available VTR tape and air-conditioned at 23 ° C. A wear test with an actual machine was performed by a method of reproducing the VTR tape for a long time indoors. When the amount of wear after the test time of 300 hours was measured,
It was confirmed that the wear resistance was excellent in the order of yttria addition, alumina addition, and yttria-stabilized zirconia addition. Further, after 1000 hours, the amount of wear of the zirconia-added material was half that of the alumina-added material. That is, it was confirmed that the material to which yttria-stabilized zirconia was added was superior in wear resistance and the coefficient of thermal expansion was also higher than those to which yttria and alumina were added.

Example 3 CoO and NiO were used as raw materials and adjusted so as to have a composition of CoO / NiO (molar ratio) = 35/65, and this composition (100 wt%) contained ₂ parts of unstabilized ZrO ₂ .
wt% was added and mixed. After calcination at 1000 ° C., it was crushed for 40 hours by a wet ball mill using ethanol. The crushed powder was CIP molded and then sintered in oxygen at 1350 ° C. This was subjected to HIP treatment under the conditions of 1250 ° C., 100 MPa, and 1 hour. The relative density of the sintered body was 98%, which was lower than that of Example 2 using yttria-stabilized ZrO ₂ . The hardness and the average particle size of the HIP-treated sintered body were Hv660 and 6.5 μm, respectively, and Example 2 (Hv7) using Yttria-stabilized ZrO ₂ was used.
00, 5.7 μm), and it was confirmed that the use of yttria-stabilized ZrO ₂ was a preferable value.

[0017]

As described above, the non-magnetic substrate having the composition of the present invention can obtain substantially the same thermal expansion coefficient and hardness as the magnetic film structure. Therefore, by using the non-magnetic substrate of the present invention with a magnetic head, peeling or cracking of the magnetic film structure can be significantly prevented. Further, by increasing the hardness, it is possible to shorten the life of the magnetic head and suppress the deformation and cracking of the non-magnetic substrate, and there is an advantage that the wear resistance and durability of the head are particularly excellent.

Claims (2)

[Claims] 1. A basic composition of CoO and NiO or NiO is used, and ZrO _{2 is} added to 100 wt% of the composition.
And at least one of HfO _{2 in} an amount of 0.1 to 7 wt% is added to the non-magnetic substrate for a magnetic head. 2. The non-magnetic substrate for a magnetic head according to claim 1, wherein the ZrO ₂ is partially stabilized zirconia.