JP2721320B2 - Non-magnetic substrate material and magnetic head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-magnetic substrate material having a high coefficient of thermal expansion, and more particularly to a non-magnetic substrate material suitable for a substrate such as a thin-film or thin-film laminated magnetic head. .

[0002]

2. Description of the Related Art As a magnetic head incorporated in a magnetic disk drive, a VTR, etc., a magnetic thin film such as a magnetic alloy represented by sendust (Fe-Al-Si) or an amorphous magnetic alloy is formed on the surface of a non-magnetic substrate material. Thin-film or thin-film stacked magnetic heads having formed magnetic circuits are widely used. In such a magnetic head, it is necessary that the thermal expansion coefficient of the substrate material, which is a non-magnetic material, is close to the thermal expansion coefficient of the magnetic thin film. This is because when the difference in thermal expansion coefficient between the substrate material and the magnetic thin film is large, a change in ambient temperature causes stress at the joint interface between the two materials, causing cracks or film peeling or degrading soft magnetic properties. It is because it causes.

As a magnetic thin film material, a cobalt (Co) -based amorphous alloy having excellent soft magnetic properties is recommended.
This alloy has a relatively low coefficient of thermal expansion of 100 to 120 × 10 ⁻⁷ / ° C. However, the thermal expansion coefficient of Sendust is about 150 × 10 ⁻⁷ / ° C. or more (depending on the temperature, this value is an average from room temperature to 400 ° C.
It is known that when the temperature is higher than 00 ° C., the average value is larger than the average value. ), Which is at least 20% higher than a cobalt (Co) amorphous alloy, but has excellent soft magnetic properties and is thermally stable even when heated to several hundred degrees, so the magnetic circuit configuration of the magnetic head Widely used as a material.

[0004] Generally, the processing temperature during the manufacturing process of the magnetic head is relatively high, and for example, it may be heated to about 400 to 600 ° C during the glass bonding (glass bonding) process. In such a high temperature region, the thermal expansion coefficient of the sendust 150 × 10 ^{- 7} / thus far exceed ° C..
Therefore, as can be seen from this example, development of a material having a high coefficient of thermal expansion is required for the magnetic head substrate material so that it can be used for applications having a high processing temperature of several hundred degrees or more.

[0005] Oxides having a high coefficient of thermal expansion include Ni.
A sintered oxide having a rock salt structure such as O, CoO, and MgO may be mentioned. The thermal expansion coefficient of such a sintered body is at most about 130 × 10 ⁻⁷ / ° C. About 147 × 10 ^-7 / ° C, 150 × 10 ^-7 /
No material exceeding ℃ is found. Since it is difficult to manufacture a sintered body having a rock salt type structure and there are many restrictions on processes, there are drawbacks such as difficulty in obtaining a sintered body having stable characteristics. When the thermal expansion coefficient is controlled over a wide range, the thermal expansion coefficient cannot be significantly controlled only by changing the composition of the same component system. NiO-Ti
Taking the case of an O ₂ -based substrate material as an example, the thermal expansion coefficient is Ni.
Japanese Patent Application Laid-Open No. Sho 62-95810 discloses that the thermal expansion coefficient can be adjusted in the range of 85 to 130 × 10 ⁻⁷ / ° C. by adding a lower amount of TiO ₂ than O. However, a substrate material having a 100~140 × 10 ^-7 / ℃ is, it is possible to obtain a rock-salt phase the method of the main phase, the thermal expansion coefficient of 140 × 10 ^-7 / ℃ higher than the range,
More specifically, the development example of the substrate material having a temperature of 150 × 10 ⁻⁷ / ° C. or more is only one example. JP-A-62-13770
No. 9 discloses a case of NiO-MgO-MnO system, but the sintered body has a thermal expansion coefficient of 130 to 154 ×.
The 10- ⁷ / ° C. are obtained are shown. But,
It is only slightly over 150 × 10 ^-7 / ° C.

[0006]

With the increase in density and speed of magnetic recording, the structure of the magnetic head has become monolithic,
The bulk type is shifting to the composite type, thin film type, and thin film lamination type. In particular, a thin-film or thin-film laminated magnetic head has a more complex structure than a monolithic or composite type, since it has a structure in which a magnetic circuit is formed by a magnetic thin film on a non-magnetic substrate and bonded with a fusion glass or the like. is there. Therefore, it is an essential condition for obtaining good magnetic head characteristics to match the thermal expansion coefficient of each component. The magnetic thin film of the thin-film laminated magnetic head needs to be able to maintain a high value without decreasing the magnetic permeability up to a high frequency range in response to the increase in recording density. Taking Sendust as an example, in order to have such properties, the heat treatment temperature of Sendust shifts to a higher temperature than before, and as a result, the coefficient of thermal expansion is 150 to 180 × 10 ⁻⁷ / ° C.
And enter the high area.

As a non-magnetic substrate material having a high thermal expansion coefficient, there is one disclosed in Japanese Patent Application Laid-Open No. Hei 6-329463. This material is a La ₂ O ₃ —CoO-based ceramic sintered body composed of a La ₂ O ₃ phase having a perovskite structure and a CoO phase having a rock salt structure. It is shown that by appropriately selecting the composition, the coefficient of thermal expansion α can be controlled in the range of 140 to 200 × 10 ⁻⁷ / ° C., and can be adapted to a high thermal expansion material such as sendust.

However, since the hardness of the material is low, the VTR
When used in magnetic heads such as those described above, abrasion is remarkable due to sliding with a magnetic tape, causing uneven wear. In addition, when used as a slider material for a flying magnetic head, CSS (C
Onstant Start and Stop) characteristics were not good, and it was not a material that could be used.

[0009] Since La ₂ O ₃ alone is hygroscopic and has a problem in environmental resistance when it is present in the sintered body in a free state, the range of use or the environment in which it is used is limited, making the material considerably difficult to use. It is. Further, since the crystal grain size is relatively large, workability is not good, cracks are easily generated, and there is a problem in reliability. Due to the large number of cracks during processing, it has not been possible to meet the needs that require fine processing polishing on the order of several microns. An object of the present invention is to provide a non-magnetic substrate material for a magnetic head which solves the above-mentioned problems.

[0010]

As a composition system of an oxide ceramic having a high coefficient of thermal expansion, L having a perovskite structure is used.
There is an aCoO ₃ composition. Α = 150-23 in this composition system
The characteristic of 0 × 10 ⁻⁷ / ° C. can be obtained as described in JP-A-6-3.
This is described in detail in Japanese Patent No. 29463. The gist of the present invention is to solve the conventional problems by adding an additive to the La ₂ O ₃ —CoO—NiO-based composition or replacing a part of La ₂ O ₃ or CoO with another oxide. It is. (1) La ₂ O ₃ —CoO—NiO based composition has Al ₂ O ₃ , Y
A sintered body containing 0.1 to 20 mol% of at least one of ₂ O ₃ , SiO ₂ , ZrO _{2 and} TiO ₂ . (2) In the La ₂ O ₃ —CoO—NiO system composition, Ni
Part of O is CaO, SrO, BaO, MnO or M
A sintered body substituted by at least one of gO. (3) In the La ₂ O ₃ —CoO—NiO-based composition, La
₂ O ₃ of some or all of Gd ₂ O _3, Nd ₂ O _3, or S
A sintered body substituted by at least one of m ₂ O ₃ . At this time, the La ₂ O ₃ —CoO—NiO-based composition is L
In terms of aO _3/2 , La ₂ O ₃ is 15 to 35 mol% and CoO is 40
６０60 mol% and NiO is 15-35 mol%.

[0011]

The sinterability of CoO alone is poor and many pores are generated. When LaO _3/2 is about 2 mol% or less, the coefficient of thermal expansion is 140 to 150 × 10 ⁻⁷ / ° C., which is about the conventional level. However, by increasing the mixing ratio of LaO _3/2 , a thermal expansion coefficient of 140 to 200 × 10 ⁻⁷ / ° C. can be obtained. La
When O _3/2 is around 50 mol%, the coefficient of thermal expansion becomes maximum, and it becomes a perovskite-type single phase systematically.

When LaO _3/2 exceeds 50 mol%, LaO
_3/2 becomes excessive and cracks easily occur. Also,
Environmental resistance is also deteriorated, and a two-phase structure of LaO _3/2 and CoO is formed. At this time, the environmental resistance is close to the practical level, but the thermal expansion coefficient cannot be sufficiently increased. In addition, NiO,
It has been found that a high thermal expansion coefficient can be achieved by including a divalent oxide such as CaO and SrO.

A study was made on the addition of NiO, which is said to have a high thermal expansion coefficient in the oxide alone, and the following conclusions were obtained. That is, since the ionic valence of NiO is divalent, it is not easily replaced with LaO _3/2 . Rather, it was found that the solid solution with CoO took a rock salt type structure of Co (1-x) NixO. In addition, the bevelskite phase of LaO _3/2 is LaC
This is a structure of o (1-y) NiyO ₃ . In this case, CoO, N
x = y cannot always be satisfied depending on the mixing ratio of iO. N
When the mixing ratio of iO is 60 mol% or more, the frequency of occurrence of cracks in the sintered body increases. The compounding ratio at this time is La
O _2/3 in terms of, CoO = 2O, a NiO = 60mol%, CoO is not the sintered body is not obtained without cracks at least 20 mol%.

Next, the case where a part of NiO is replaced by another divalent oxide will be described. In the case of MnO and ZnO, it is easily dissolved in the phase of the rock salt type structure of (CoNi) O in the crystal structure of La (CoNi) O ₃ and (CoNi) O. In the case of CaO, SrO and BaO, it is La. (CoN
i) It is easily dissolved in the O ₃ phase. La ₂ O ₃ , CoO, NiO
The system ceramic has a structure of two or more phases, and it is effective to replace NiO with these components when controlling the coefficient of thermal expansion or adjusting the area ratio of each phase. At this time, if the mixing ratio is 25 mol%, that is, if the entire amount is replaced, a structure close to a single phase of elements such as CaO and ZnO is easily generated inside the substrate, and the environmental resistance deteriorates in the single phase portion.

Further, Al ₂ O ₃ , Y ₂ O ₃ , SiO ₂ , Ti
The addition of O ₂ and ZrO ₂ was studied. Even when these additives are added, the control of the coefficient of thermal expansion becomes easy. In addition, products to be subjected to fine processing such as a magnetic head are required to have workability, so-called grinding property, and chipping resistance. By adding these additives, it is possible to control the conventional average grain size of about 1 to 4 μm to about 0.5 to 2 μm to about half or less, and the Vickers hardness is also 500 to 1200 kgf / mm ^2. It is considered that the resulting material has good grindability. In addition, uneven wear with metal magnetic films formed under various conditions is also 500 to 1000.
It can be improved by selecting an appropriate value from the range of kgf / mm ² . Here, these additives are
If it is added in an amount of at least mol%, the range of the coefficient of thermal expansion deviates from a preferable range.

Next, since La ₂ O ₃ is a single phase, the environmental resistance is remarkably deteriorated. Therefore, a substitute for La ₂ O ₃ was examined. La ₂ O ₃ and Gd ₂ O ₃ also as having a high thermal expansion coefficient, Nd ₂ O ₃ or Sm ₂ O _3,
Was mentioned. Their ionic radius and crystal structure are La ₂
Similar effects can be obtained because it is similar to O ₃ . However, also when these amounts are large, the environmental resistance decreases.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments. (Example 1) As raw materials, commercially available La ₂ O ₃ and Co oxides are CoO, Co ₃ O ₄ , or CoO + Co ₃ O ₄ ,
And a commercially available NiO raw material were added to the additive Al ₂ O ₃ , ZrO
Commercially available products were used for ₂ , SiO ₂ , TiO ₂ , and Y ₂ O ₂ . La ₂ O ₃ as wherein a molar basis it is easy to weigh them as LaO _3/2, after mixing in a wet ball mill at a dry atmosphere 700-100
A calcination treatment was performed at 0 ° C. After the calcined powder is pulverized by a wet ball mill, about 1% of a PVA-based organic binder is added to perform granulation, and a molding pressure of 1 to ² ton / cm ² and 30 × 40.
A molded body having a size of about × 10 mm was produced. These compacts are sintered at 1200 to 1400 ° C. in the air, nitrogen or a mixed atmosphere thereof, and further sintered at 1250 ° C.
A hot isostatic press (HIP) treatment was performed under a condition of 1000 to 1500 atm. Here, if LaO _3/2 mixing ratio is less than 15 mol% even if the granulation in the calcination process without a mixed powder direct spray dryer or the like is equivalent obtained. The prepared sample was cut out to an appropriate size and subjected to analytical measurement by thermal expansion coefficient, Vickers hardness, average crystal grain size, and X-ray diffraction. The coefficient of thermal expansion is an average value from room temperature (30 ° C.) to 600 ° C. measured by a coefficient of thermal expansion meter, and the Vickers hardness is 300 g with a micro Vickers hardness meter.
It was measured by load. The average crystal grain size was calculated by a diagonal cross method after etching with a hydrofluoric acid solution. X-ray diffraction was measured in the range of Cu-Kα ray diffraction angle 2θ = 20 to 100 degrees, and the generated phase was identified. Table 1 shows examples and comparative examples. When the LaO _3/2 compounding ratio was more than 50 mol%, cracks occurred in the sample in the sintering step. Also,
When the content was 2 mol% or less, the effect of increasing the coefficient of thermal expansion was small. It was confirmed that when the amount of the additive was 30 mol%, the intended coefficient of thermal expansion was not obtained, and the sinterability was also deteriorated. FIGS. 1 and 2 show the thermal expansion coefficient and Vickers hardness characteristics when Al ₂ O ₃ or ZrO ₂ is added. As the addition amount of Al ₂ O ₃ or ZrO ₂ increases, the coefficient of thermal expansion decreases, but the Vickers hardness increases. It was also confirmed that the same tendency was observed when SiO ₂ , TiO ₂ , Y ₂ O _{3 and the} like were added. Further, the Vickers hardness is increased by adding these additives.

[0019]

[Table 1]

(Example 2) MnO, Ca was used to replace a part of NiO in a La ₂ O ₃ —CoO—NiO-based substrate.
Bivalent metal oxides of O, SrO, BaO, MgO, and ZnO are mentioned. When preparing samples, commercially available MgO and ZnO were used for MgO and ZnO, and Mn
Carbonates such as CO ₃ and CaCO ₃ were used and calcined to decompose the CO ₂ component and replace it with NiO as a divalent oxide in the ceramics to form a solid solution. Thereafter, molding, sintering, and HIP treatment were performed in the same manner as in Example 1. Table 2 shows these examples and comparative examples. The thermal expansion coefficient tends to decrease as the NiO substitution amount increases. When the substitution amount exceeds half of the NiO amount, Ca
A single phase structure such as O and ZnO is easily generated, and environmental resistance is deteriorated. When the additive is added in combination with the additive of Example 1, changes in physical properties such as thermal expansion coefficient and hardness tend to be similar to those of Example 1.

[0021]

[Table 2]

[0022] (Example _{3) La} 2 O 3 in part or commercial Gd ₂ O ₃ in the case of replacing the whole, Nd ₂ O _3,
Alternatively, a sample was prepared in the same process as in Example 1 using Sm ₂ O ₃ . Table 3 shows these examples and comparative examples. These have the same crystal structure as La ₂ O ₃ and show the same tendency in physical property values. The same applies to the environmental resistance. When the content of these elements increases, they deteriorate.

[0023]

[Table 3]

[0024]

According to the present invention, a non-magnetic substrate material for a magnetic head having a thermal expansion coefficient of 140 to 200 × 10 ^−7, which has not been developed, can be provided. -When an Al-Si soft magnetic metal thin film is formed, film peeling or cracking due to a difference in thermal expansion occurs.
The property deterioration of the film under stress can be reduced,
It is possible to increase the recording density of the magnetic head.

[Brief description of the drawings]

FIG. 1 shows the thermal expansion characteristics according to the present invention.

FIG. 2 shows Vickers hardness characteristics according to the present invention.

FIG. 3 shows thermal expansion characteristics according to another embodiment.

Claims (7)

(57) [Claims] (1) La ₂ O ₃ is 15 to 35 in terms of LaO _3/2.
mol%, CoO is 40-60 mol%, NiO is 15
Al ₂ O ₃ , Y ₂ O ₃ , SiO ₂ , Zr
0.1 or more of O ₂ or TiO ₂
A non-magnetic substrate material characterized by being a sintered body added with 〜20 mol% and fired. 2. La ₂ O ₃ is 15 to 35 in terms of LaO _3/2.
mol%, CoO is 40-60 mol%, NiO is 15
To 35 mol%, a part of the NiO is replaced with CaO, Sr.
A non-magnetic substrate material characterized by being a sintered body that has been substituted with at least one of O, BaO, MnO and MgO and fired. 3. The non-magnetic substrate material according to claim 1, wherein a part or all of La ₂ O ₃ is Gd ₂ O ₃ , Nd.
A non-magnetic substrate material characterized by being a sintered body substituted by at least one of ₂ O ₃ and Sm ₂ O ₃ . 4. The non-magnetic substrate material according to claim 1, which has a thermal expansion coefficient of 140 to 200 × 10.
^A nonmagnetic substrate material having a temperature of ^-7 / ° C. 5. The nonmagnetic substrate according to claim 1, wherein the Vickers hardness is 500 to 1200 kg.
f / mm ² , a non-magnetic substrate material. 6. The non-magnetic substrate material according to claim 1, wherein the crystal grain size is at most 5 μm. 7. A magnetic head using the non-magnetic substrate material according to claim 1.