JPH0682448B2 - Oxide substrate and magnetic head using the same - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxide substrate used for a magnetic head and the like, and a magnetic head configured using the oxide substrate.

Conventional technology Conventionally, magnetic head materials are composed of soft magnetic materials such as permalloy, sendust, amorphous alloy, Mn-Zn-
Ferrite or the like is used, and this is bonded or adhered to the substrate, and it is known that it is formed as a thin film on the substrate by a method such as vapor deposition, sputtering, CVD or plating.

In the magnetic head having such a structure, unless the thermal expansion coefficient of the soft magnetic material and the substrate material are equal to each other or the difference between them is extremely small, stress is generated at the interface between the two materials due to temperature change,
This may cause cracking or deteriorate the magnetic characteristics of the soft magnetic material due to the magnetostrictive effect. For this reason, a substrate material that can freely change the coefficient of thermal expansion is required in accordance with the coefficient of thermal expansion depending on the type and composition of the soft magnetic material used, and crystallized glass, CaO-SrO-TiO ₂ -based ceramic substrate (JP No. 52-57218), a NiMnO ₂ -based ceramic substrate (JP-A-53-16399), an MgO-TiO ₂ -based ceramic substrate (JP-A-58-139322), and the like have been proposed.
By adjusting the composition of these substrate materials, the thermal expansion coefficient can be selected in a wide range.

Problems to be Solved by the Invention However, crystallized glass and CaO-SrO-TiO ₂ -based ceramic substrates are chemically unstable because they contain an alkali metal or Ca as a component. When the head is configured, when a magnetic tape or the like is actually run, a phenomenon in which magnetic powder adheres to the substrate surface occurs, and the magnetic head characteristics deteriorate. With NiMnO ₂ ceramic substrates, such adhesion phenomenon from the magnetic tape does not occur, but when MnO is heated in air, it easily oxidizes to Mn ₂ O ₃ , so the atmosphere during firing is non-oxidized. However, there are drawbacks such as high manufacturing cost, poor grindability when working into a used shape, and low working efficiency.

On the other hand, with the MgO-TiO ₂ -based ceramic substrate, the above problems do not occur, but the coefficient of thermal expansion is 95 × 10 ^-7 / ℃ (25 ~ 4
With a composition exceeding 00 ° C), the molar ratio of MgO and TiO ₂ exceeds 2: 1, so free MgO is contained in the sintered body, which causes deliquescent phenomenon under high humidity conditions. There was a flaw.

Means for solving the problem MgO is 2 to 96 mol%, NiO is ₂ to 96 mol%, the balance is TiO ₂ , and the total amount of MgO and NiO is 50 to 98 mol%. A substrate is formed by using a bonded body as a main component.

Action The inventors have found that MgO-NiO-TiO ₂ ceramics has a thermal expansion coefficient of 85 to 130 × 10 ^-7 / ° C (25 ° C to 400 ° C) depending on the composition ratio.
It has been found that the temperature can be adjusted within the range of (° C.), that magnetic powder does not adhere even when a magnetic tape is run on the substrate surface, that grinding is easy, and that deliquescent does not occur.

If the total amount of MgO and NiO is 50 to 98 mol%, that is, if the amount of TiO ₂ is 2 mol% or more, good grindability can be obtained, and vapor deposition / sputtering / CVD on the substrate surface is possible.・ The coefficient of thermal expansion of metal magnetic thin film formed by plating 95
A coefficient of thermal expansion equivalent to ~ 125 × 10 ^-7 / ℃ (25 ~ 400 ℃) can be obtained. The reason for limiting the amount of MgO to 2 to 96 mol% is that if the amount of MgO is too small, the grindability deteriorates, and if the amount of MgO exceeds 96 mol%, deliquescent occurs. Conversely, Ni
The reason for limiting the O amount to 2 to 96 mol% is that if the NiO amount is too small, deliquescent occurs, and if the NiO amount exceeds 96 mol%, the grindability deteriorates.

The MgO-NiO-TiO ₂ based ceramic substrate is adjustable thermal expansion coefficient, easy to manufacture, and has excellent weather resistance and grinding processability.

Examples Examples are shown below.

Special grades of MgO, NiO, and TiO ₂ were weighed and mixed for 16 hours in a ball mill using alcohol as a dispersion medium.
It was dried at ℃, to obtain a mixed powder of various compositions. After calcining these mixed powders in air at 900 ° C, 1 again with a ball mill.
It was crushed for 6 hours and dried at 150 ° C. 5wt% to this calcinated powder
10 wt% of the polyvinyl alcohol aqueous solution was added for granulation, and pressure molding was performed at a pressure of 1000 kg / cm ² . The molded body is pressed at a temperature between 1200 and 1350 ° C (300 kg / 300 kg /
cm ² ) Sintered. The density of the obtained sintered body was measured by the Archimedes method. As a result, the density of the sintered body was 99.5% or more of the true density in any composition. Therefore, a sample was cut out from this sintered body and the temperature was measured at 25 ° C using a thermal expansion coefficient meter.
The coefficient of thermal expansion between ~ 400 ° C was measured. Also, with a normal grinding and cutting machine and artificial diamond No. 150, diameter 100 mm, thickness 0.5 m
Grinding wheel rotation speed 3000 rpm, feed speed 10 using m grinding wheel
Wet grinding and cutting was performed under the conditions of mm / min and grinding depth of 3 mm, and the specific grinding energy was calculated from the change in power consumption of the spindle motor and the weight reduction of the specific cutting material. Further, the sample was mirror-polished to have a surface roughness Rmax <100 Å, then put into water, and after 24 hours, the surface roughness was measured again to evaluate its water resistance. For comparison, crystallized glass, and
The same measurement was performed on the NiMnO ₂ ceramic substrate. The results are shown in Table 1.

It can be seen from Table 1 that the coefficient of thermal expansion increases as the total amount of MgO and NiO increases. Coefficient of thermal expansion 95 × 10 ^-7 / ℃
To achieve the above, the total amount of MgO and NiO must be 50 mol% or more. On the other hand, the specific grinding energy also shows the same tendency, but it is sufficiently smaller than the crystallized glass or NiMnO ₂ -based ceramic substrate in the composition range where the NiO content is 96 mol% or less and the MgO content is 2 mol% or more. It was about half that. Regarding the water resistance, when the NiO content was less than 2 mol%, surface roughness of Rmax ≈ 2000Å occurred, but the NiO content was 2
The Rmax <300Å was obtained for the substances with mol% or more. As described above, it is sufficient for the water resistance that the NiO content is 2 mol% or more. Therefore, as a composition range that simultaneously satisfies high thermal expansion coefficient, low specific grinding energy, and high water resistance, MgO
Is 2 to 96 mol%, NiO is 2 to 96 mol%, the total amount of MgO and NiO is 50 to 98 mol%, and TiO ₂ is 2 to 50 mol%.

Therefore, next, MgO = 75, which has a coefficient of thermal expansion of 114 × 10 ^-7 / ° C.
A magnetic head was prepared by selecting a substrate of mol%, NiO = 13 mol% and TiO ₂ 12 mol% and forming a Co—Zr system amorphous magnetic metal thin film on the surface by sputtering. For comparison, magnetic heads were made in the same manner using crystallized glass, NiMnO ₂ system ceramics, and MgO—TiO ₂ system ceramics. Metal magnetic tapes were actually run on these magnetic heads under various environments, and the head output change, abrasion resistance, and environmental resistance were tested. As a result, in the case of several hours after the start of measurement, there was no particular difference in the characteristics depending on the type of substrate when the environmental conditions were temperature 20 ° C and humidity 50%.
At a humidity of 10%, in a magnetic head using crystallized glass as a substrate, the metal powder of the magnetic tape adhered to the substrate surface, and the head output dropped by a few dB. Also, at a temperature of 40 ° C and a humidity of 80%, Mg
In the magnetic head using the O-TiO ₂ ceramic substrate, the free MgO was dissolved, and a step corresponding to the grain size was generated on the substrate, and the head output was reduced by 2-3 dB. In the case of about 100 hours after the start of measurement, the magnetic head using the MgO-TiO ₂ -based ceramic substrate had the above-mentioned free emission even at a temperature of 20 ° C and a humidity of 80%.
Dissolution of MgO occurred and the head output decreased by several dB. Also, N
Even in the magnetic head using the iMnO ₂ ceramic substrate, there was a difference in abradability between the substrate and the amorphous soft magnetic material after 100 hours, so that a step was generated on the head surface and the head output was reduced. However, in the magnetic head using the MgO-NiO-TiO ₂ substrate of the present invention, adhesion and dissolution do not occur even under all environmental conditions, and the abrasion resistance with the amorphous soft magnetic material is also good, and it can be used for a long time. Even when used, the change in head output was within 1 dB.

In the above examples, the coefficient of thermal expansion is 114 × 10 ^-7 / ° C.
Although the case of using a Co-Zr type amorphous soft magnetic thin film is shown, the soft magnetic material is not limited to this, an amorphous material of other composition, an alloy material such as Permalloy-Sendust,
Or, for any magnetic core material such as Mn-Zn ferrite, depending on its thermal expansion coefficient, MgO, NiO, Ti
The optimum substrate can be provided by changing the O ₂ content.

Further, the substrate material used in the present invention is MgO, NiO, TiO ₂ as a main component, to improve the machinability and sinterability, to add a small amount of ZrO ₂ , SiO _2, etc. Even if it is contained in the glass and contains a small amount of impurities, it does not cause any problem.

The oxide substrate of the present invention contains MgO in an amount of 2 to 96 mol% and NiO in an amount of 2 to 96 mol%.
A substrate mainly composed of an oxide composite sintered body, which comprises 96 mol% and a balance of TiO ₂ and has a total content of MgO and NiO of 50 to 98 mol%, and is used as a substrate for a magnetic head. When used, it is stable against contact running with a magnetic recording medium because it does not contain calcium or alkali metal, and has good wear resistance matching with a soft magnetic material. Moreover, it is easy to manufacture and process.

Claims (2)

[Claims] 1. MgO of 2 to 96 mol%, NiO of 2 to 96 mol%,
An oxide substrate mainly composed of an oxide composite sintered body composed of the balance TiO ₂ and having a total content of MgO and NiO of 50 to 98 mol%. 2. MgO of 2 to 96 mol%, NiO of 2 to 96 mol%,
An oxide substrate mainly composed of an oxide composite sintered body, which is composed of the balance TiO ₂ and has a total amount of MgO and NiO of 50 to 98 mol%,
A magnetic head characterized in that a soft magnetic material is formed as a magnetic core on this substrate.