JPH08241501A - Nonmagnetic substrate for magnetic head - Google Patents

Abstract

PURPOSE: To remarkably suppress the peeling of a magnetic film from the substrate and the cracking of the substrate at the time of mechanical working and to obtain a substrate ensuring high economics such as an enhanced yield. CONSTITUTION: This nonmagnetic substrate is based on NiO, contains >=5mol% MgO and >=0.2mol% Al2 O3 and has >=130×10<-7> / deg.C coefft. of thermal expansion. The coefft. of thermal expansion matches that of a magnetic film for high recording density and this substrate has high mechanical strength.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-magnetic magnetic head substrate composition for depositing a metallic magnetic film.

[0002]

2. Description of the Related Art Conventionally, BaTiO ₃ ,
Although CaTiO _{3 and the} like have been used, in recent years, as a substrate for high recording density magnetic film, MnO-NiO system, MgO-NiO system, CoO-NiO system having a thermal expansion coefficient of 130 ~ 145 × 10 ^-7 / ℃. Non-magnetic substrates of the system have come to be used.

[0003]

[Problems to be Solved by the Invention] However, the above MnO-NiO
System, MgO-NiO system, CoO-NiO system non-magnetic substrate shows good thermal expansion coefficient match with high recording density magnetic film, but it is difficult to obtain a dense sintered body with a hardly sinterable material. However, the mechanical strength thereof is inferior to those of BaTiO ₃ , CaTiO _{3 and the} like which have been conventionally used, and therefore, various conditions as a magnetic head substrate were not sufficiently satisfied.

As a material for a magnetic head substrate having a thermal expansion coefficient of 130 to 145 × 10 ⁻⁷ / ° C., Mg _x Ni _1-x O (0 <
A material whose main component is x <1 is known (Japanese Patent Publication No. 5-8004).
Four). However, this Mg _x Ni _1-x O (0 <x <1) has a problem that the sintered body density is not improved.

[0005]

Means and Actions for Solving the Problems In order to solve the above-mentioned problems, the present inventors set (Ni _1-X , Mg _X ) O, x ≧ 0.05 as a basic composition, and add Al ₂ O ₃ thereto. By adding 0.2 to 7 mol%, Vickers hardness of 700 or more, Young's modulus of 170 GPa or more, relative density of sintered body of 98% or more, and magnetic expansion coefficient of 130 to 150 × 10 ⁻⁷ / ° C. at 100 to 400 ° C. It has been found that a non-magnetic substrate for head can be obtained.

That is, the present invention has solved the above-mentioned problems and has NiO as a basic composition and MgO in an amount of 5 mol% or more 2
A non-magnetic substrate for a magnetic head containing 6 mol% or less and Al ₂ O _{3 in the range} of 0.2 mol% or more and 9.5 mol% or less, characterized by having a thermal expansion coefficient of 130 × 10 ^-7 / ° C or more. A non-magnetic substrate for magnetic heads, with NiO as the basic composition and MgO
5 mol% or more, the Al ₂ O ₃ contains more than 0.2 mol%, and x (mol%) of MgO content, when the content of Al ₂ O ₃ was y (mol%), content of Al ₂ O ₃ y is y ≦ -1.8 × 10 ⁻³ x ³ + 0.053x ² −
It is a non-magnetic substrate for a magnetic head characterized by having a size of 0.59x + 11.4.

[0007]

DETAILED DESCRIPTION OF THE INVENTION In order to facilitate understanding of the present invention,
A specific and detailed description will be given. NiO is a material having a very high coefficient of thermal expansion among metal oxides, and by containing MgO which forms a solid solution throughout this, 130-150 × which is required as a substrate material for a magnetic film for high recording density. It becomes possible to arbitrarily select the thermal expansion coefficient between 10 ^-7 / ° C, and at the same time, the mechanical strength increases.

Further, the added Al ₂ O ₃ partly forms a solid solution with the matrix during the temperature rising process of sintering to form cation vacancies,
Since it accelerates the diffusion rate of cations, it exhibits a sintering aid effect. In addition, Al ₂ O ₃ above the solid solubility limit reacts with the matrix to form (Ni, Mg) Al ₂ O ₄ spinel on the grain boundaries and suppresses grain growth, so And the mechanical strength is improved, and at the same time, the wear resistance and the Young's modulus are improved by the wear resistance and the high Young's modulus characteristics of the compound having the spinel structure.

When the amount of Al ₂ O ₃ added is less than 0.2 mol%, Al
The effect of ₂ O _{3 as} a sintering aid disappears, and the relative density is 98%.
The above dense sintered body cannot be obtained. Also, MgO
If the content is less than 5 mol%, Vickers hardness less than 700,
Young's modulus is less than 170 GPa and mechanical strength is low. MgO
When the content is 5 mol% or more and the amount of Al ₂ O ₃ added is 0.2 mol% or more, the upper limit of the thermal expansion coefficient is 150 × 10 ^-7 / ° C. On the other hand, the lower limit of the thermal expansion coefficient of 130 × 10 ^-7 / ° C is controlled by adjusting the contents of Al ₂ O ₃ and MgO. Al with a lower thermal expansion coefficient of 130 × 10 ^-7 / ° C
The contents of ₂ O ₃ and MgO are shown by the curve a in FIG.

In the range below the curve a in FIG. 1, the coefficient of thermal expansion is 130 × 10 ⁻⁷ / ° C. or more. Therefore, in the composition range shown by the diagonal lines in FIG. 1, Vickers hardness of 700 or more, Young's modulus of 170 GPa or more, relative density of the sintered body of 98% or more, 100 to
A non-magnetic substrate for a magnetic head having a thermal expansion coefficient at 400 ℃ of 130 to 150 × 10 ^-7 / ℃ can be obtained. Curve a is MgO
When the content is x (mol%) and the Al ₂ O ₃ content is y (mol%), y = −1.8 × 10 ⁻³ x ³ + 0.053x ² −0.59x + 11.4. Examples of the present invention will be described below.

[0011]

Example: To the basic composition NiO powder, MgO powder was added 0 mol% (no addition), Al ₂ O ₃ powder was added 0, 0.1, 0.2, ₃ , 7 mol%, and M
5, 15, 20, 25 mol% gO powder, and Al ₂ O ₃ powder respectively
0, 0.1, 0.2, 0.5, 1, 3, 7, 10 mol% was added and mixed for 20 hours by a wet ball mill using ethanol as a medium. After the mixed slurry was dried, it was calcined at 1000 ° C. for 10 hours and then pulverized again by a wet ball mill using ethanol as a medium. After granulating this pulverized powder, preforming was performed by uniaxial pressing, and then main forming was performed by CIP. After firing at 1320 ° C for 10 hours in air, 1280
HIP treatment was carried out at 1000 ° C. for 1 hour at 1000 kg / cm ² . The obtained sintered body was evaluated for density, Vickers hardness, Young's modulus, and coefficient of thermal expansion between 100 and 400 ° C. The results obtained by this example are shown in Table 1.

[0012]

[Table 1]

As shown in Table 1, the relative densities of the sintered bodies to which Al ₂ O ₃ powder was added (contained) by 0.2 mol% or more were all densified to 98% or more. In addition, MgO powder 5 mol% or more, Al ₂ O
The Young's modulus and Vickers hardness of the sintered body in which 0.2 mol% or more of the _three powders were added (inclusion) increased to 170 GPa or more and 700 or more, respectively, as the MgO content and the Al ₂ O ₃ content increased. The coefficient of thermal expansion of the sintered body was 150 × 10 ^-7 / ℃ or less. In particular, one containing (containing) 0.5 mol% or more of Al ₂ O ₃ powder is preferable because the relative density of the sintered body is 99% or more.

The coefficient of thermal expansion of 130 × 10 ⁻⁷ / ° C. is due to Al
It can be determined from the relationship between the ₂ O ₃ content and the coefficient of thermal expansion (Fig. 2).

□ is MgO content of 5 mol%, ○ is Mg
When the O content is 15 mol%, ■ indicates the MgO content is 20 mol%, and ● indicates the MgO content is 25 mol%.
The content of M ₂ and the Al ₂ O ₃ content that gives a thermal expansion coefficient of 130 × 10 ^-7 / ° C.
Rewriting the relationship with the gO content gives the curve a in FIG. Therefore, (MgO content, Al ₂ O ₃ content) in FIG.
Mol%, 0.2 mol%) (5 mol%, 0.2 mol%) (5 mol%, 9.
5 mol%) and a region surrounded by a curve a, the Vickers hardness is 700 or more, the Young's modulus is 170 GPa or more, the relative density of the sintered body is 98% or more, and the thermal expansion coefficient at 100 to 400 ° C. is 13
It is possible to obtain a non-magnetic substrate for a magnetic head of 0 to 150 × 10 ^-7 / ° C.

[0016]

As described above, according to the present invention, Mg _x N
By adding Al ₂ O ₃ to i _1-x O (0 <x <1), the relative density of the sintered body is dramatically improved, and at the same time, the mechanical strength of the magnetic film for high recording density is excellent. A non-magnetic substrate for a magnetic head having a good thermal expansion coefficient can be obtained.

[Brief description of drawings]

FIG. 1 is a Vickers hardness of 700 or more and a Young's modulus of 170.
Al ₂ O ₃ content which can obtain a non-magnetic substrate for a magnetic head having a GPa or more, a relative density of a sintered body of 98% or more, and a thermal expansion coefficient at 100 to 400 ° C. of 130 to 150 × 10 ⁻⁷ / ° C. It is the figure which showed the composition range of MgO content.

FIG. 2 is a diagram showing the relationship between the Al ₂ O ₃ content and the coefficient of thermal expansion, and □ indicates that the MgO content was 5 mol%.
Indicates that the MgO content is 15 mol%, ■ indicates that the MgO content is 20 mol%, and ● indicates that the MgO content is 25 mol%.

Claims (2)

[Claims] 1. A basic composition of NiO, to which MgO is contained in an amount of 5 mol% to 26 mol% and Al ₂ O ₃ is contained in an amount of 0.2 mol% to 9.5 mol%.
A non-magnetic substrate for a magnetic head containing the following, which has a thermal expansion coefficient of 130 × 10 ⁻⁷ / ° C. or more. 2. A basic composition of NiO, containing 5 mol% or more of MgO and 0.2 mol% or more of Al ₂ O ₃ , and having a MgO content of x (mol%) and an Al ₂ O ₃ content of When y (mol%), Al ₂
A non-magnetic substrate for a magnetic head, wherein the O ₃ content y is y ≦ −1.8 × 10 ⁻³ x ³ + 0.053x ² −0.59x + 11.4.