JPH06282810A - Nonmagnetic base material for magnetic head - Google Patents

Abstract

PURPOSE:To enlarge a thermal expansion coefficient, to make machinability excellent and also to make the cost low by adding the proper quantity of SiO2 to a base material alphaFe2O3. CONSTITUTION:Powder of alphaFe2O3 and powder of SiO2 are mixed in a prescribed ratio and subjected to pressure molding. Then, the molded material is baked for a prescribed time at a temperature of about 1100 deg.C in air to be sintered. Moreover, the material is subjected to hot isotropic pressurization in an inactive atmosphere. An available range of the quantity of SiO2 to be added is 1.0 to 30wt.%.

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 for a magnetic head used in VTRs, FDDs (floppy disk drives), HDDs (hard disk drives) and the like.

[0002]

2. Description of the Related Art Conventionally, magnetic heads such as VTRs, FDDs, and HDDs are magnetic oxides of Mn-Zn ferrite and Ni-.
It was mainly composed of Zn ferrite. However, due to strong demands for high-density recording in recent years, the slider body is made of a non-magnetic material, and a ferrite magnetic core is embedded in the groove provided at the rear end of the slider to reduce the inductance of the magnetic head and increase the operating frequency. Attention has been paid to so-called composite type heads, which have been made compatible, and, more recently, stacked type magnetic heads in which a magnetic circuit is composed only of a metal magnetic thin film formed on a non-magnetic substrate for the purpose of higher density recording. There is. The αFe ₂ O ₃ containing SiO ₂ of the present invention is used as a nonmagnetic substrate for such a magnetic head.

[0003]

In the above magnetic head, it is necessary to sufficiently exhibit the magnetic characteristics of the magnetic material forming the magnetic circuit in order to efficiently perform the recording and reading. For this purpose, it is necessary to minimize the deterioration of the characteristics of the magnetic core due to the stress generated by glass welding or the like, as well as the structural design of the magnetic head. In the composite type head, the slider main body is made of non-magnetic ceramics, and the magnetic core is fixed to the groove provided at the rear end of the slider with the filling glass. Since Mn-Zn ferrite or the like is generally used as the magnetic core material, the thermal expansion coefficient α of the filled glass and the non-magnetic ceramic used therein is made close to that of the magnetic core material such as Mn-Zn ferrite, and the heat generated in each manufacturing process is used. It is necessary to reduce the stress and the stress applied to the Mn-Zn ferrite. If this is not appropriate, the magnetic characteristics will deteriorate, and not only the recording / reading ability will become insufficient, but also cracks will easily occur in the filling glass and its joint, leading to a reduction in yield.

Further, in a laminated magnetic head, a metallic magnetic thin film such as sendust is deposited on a non-magnetic substrate in a range of several μm to several tens of μm.
It is formed with a thickness of m by means such as sputtering or vapor deposition. At this time, in order to perform recording and reading efficiently, similarly to the composite type head, the stress applied to the metal magnetic thin film which is a magnetic circuit component must be suppressed as small as possible. For this purpose, it is the most important point to bring the thermal expansion coefficients of the metal magnetic thin film and the non-magnetic substrate close to each other. By the way, the material used as the magnetic material of the conventional magnetic head is Mn-Zn ferrite (α = 120
~ 140 × 10 ^-7 / ° C), sendust (α = 150 × 1)
0 ^-7 / ° C), permalloy (135 x 10 ^-7 / ° C)) and metallic iron film (130 x 10 ^-7 / ° C)
In each case, the coefficient of thermal expansion α is (120 to 150) × 10
^It was in the range of ^-7 / ° C, and the difference in α from the substrate was large, causing problems such as characteristic changes during heat treatment and use.

Further, the magnetic head is manufactured by mechanical processing such as grinding and cutting, and records and reads a signal by a sliding or contact start / stop method with a magnetic recording medium such as a magnetic tape, a flexible disk and a hard disk. Therefore, in addition to the fact that the non-magnetic substrate used for the magnetic head does not deteriorate the magnetic characteristics of the magnetic core,
Good machinability and excellent sliding characteristics with respect to the magnetic recording medium are also important characteristics.

[0006] Currently, as a general non-magnetic substrate, BaT
iO ₃ (for example, Japanese Examined Patent Publication No. 62-24387), CaT
iO ₃ (for example, Japanese Patent Publication No. 60-21940), αFe
₂ O ₃ (for example, Japanese Patent Laid-Open No. 4-78009) is used in FDDs, HDDs and the like which are general-purpose magnetic recording devices. However, BaTiO ₃ has a coefficient of thermal expansion of (95
100) the thermal expansion coefficient of a magnetic material such as × 10 ^-7 / ° C. and Mn-Zn ferrite (120 to 150) × smaller than the 10 ^-7 / ° C.. Also, CaTiO ₃ has a thermal expansion coefficient of (110
~ 120) × 10 ^-7 / ° C, which is larger than BaTiO ₃ and M
Although close to the coefficient of thermal expansion of n-Zn ferrite, it is preferable, but since the resistance during grinding is large, the load during processing is large, and excess CaO, which is easily soluble in water, exists as a heterogeneous phase.
There is a problem of poor moisture resistance. On the other hand, αFe ₂ O ₃
Has a low grinding resistance and good machinability but has a small coefficient of thermal expansion of 115 × 10 ⁻⁷ / ° C., so that there is no material having sufficient characteristics as a non-magnetic substrate material. But α
Fe ₂ O ₃ is highly desirable from the viewpoint of cost because it can be obtained at low cost.

[0007]

The inventors of the present invention searched for materials suitable for these non-magnetic substrates, and found that αFe ₂ O ₃
M used for magnetic core by adding SiO ₂ to
It has been discovered that the coefficient of thermal expansion can be made large enough to be compatible with n-Zn ferrite and metal magnetic thin films. Also, S
It was also confirmed that the addition of iO ₂ does not impair the good machinability, which is an advantage of αFe ₂ O ₃ .

[0008]

As described in detail below, by adding SiO ₂ to αFe ₂ O ₃ , the coefficient of thermal expansion tends to be large, and a fairly wide range (115-135) ×
It can be adjusted at 10 ^-7 / ° C. The thermal expansion coefficient of most conventional magnetic materials for magnetic heads is 120 to 150 × 10 ⁻⁷ / ° C.
And the thermal expansion coefficient of αFe ₂ O ₃ is much larger than that of S
If the iO ₂ is adjusted and added, the thermal expansion coefficient can be made close to that of the magnetic material without causing any trouble. On the other hand, the density decreases with the addition of SiO ₂ having a smaller specific gravity than αFe ₂ O ₃ , but if added in a large amount, the sinterability of αFe ₂ O ₃ is impaired. The addition of SiO ₂ does not substantially increase the grinding resistance. Further, it has been found that since the coefficient of thermal expansion approaches that of the magnetic material, the occurrence of defects (peeling) due to thermal stress during processing can be prevented. In total, the usable amount of SiO ₂ added is 1.0 to 30 wt% for the magnetic head substrate.

The non-magnetic substrate material for a magnetic head of the present invention is
αFe ₂ O ₃ powder and SiO ₂ powder are mixed at a predetermined ratio, pressure-molded, sintered in air at a temperature of about 1100 ° C. for a predetermined time and sintered, and further hot isostatically in an inert atmosphere. It can be manufactured by applying pressure. Examples will be described below.

[0010]

EXAMPLE 1 0.1 wt% of SiO ₂ powder (reagent) was added to 500 g of αFe ₂ O ₃ powder, 1 liter of pure powder was added, and then mixed and pulverized for 24 hours in a ball mill. After the pulverization is completed, dehydration and drying are performed, and then a block formed by a hydraulic press is subjected to CIP (cold isotropic pressurization) at a pressurizing force of 3 ton and then fired in air at 1100 ° C. for 5 hours. After that, HIP in 1100 ° C, 1000 atm, Ar
(Hot isostatic pressing) was performed. This is sample # 1.

Example 2 The addition amount of SiO ₂ powder was set to 1 wt% and the firing temperature and H
Example 1 was repeated except that the IP temperature was 1200 ° C. This is sample # 2.

Example 3 The amount of SiO ₂ powder added was set to 5 wt%, and the firing temperature and H
Example 1 was repeated except that the IP temperature was 1200 ° C. This is sample # 3.

Example 4 The amount of SiO ₂ powder added was 30 wt%, and the amount of pure water was 2 liters in order to reduce the viscosity of the slurry.
Example 1 was repeated except that the IP temperature was 1200 ° C. This is sample # 4.

Example 5 The amount of SiO ₂ powder added was 50 wt%, and the amount of pure water was 2%.
The same procedure as in Example 1 was carried out except that the calcination temperature and the HIP temperature were 1200 ° C. This is sample # 5
And

Comparative Example As a comparative example, αFe ₂ O ₃ containing no added SiO ₂ was prepared. That is, pure 1 liter was added to 500 g of αFe ₂ O ₃ powder, and the mixture was pulverized and pulverized for 24 hours in a ball mill. The steps after pulverization were the same as in Example 1. This is sample # 6.

Table 1 shows samples # 1 to 6 after HIP treatment.
Is the coefficient of thermal expansion measured by a push rod type thermal expansion measuring instrument and the value of density measured by the Archimedes method. 100-600 degreeC of a table shows having measured at both ends.

[0017]

[Table 1]

As is clear from Table 1, αFe ₂ O ₃ has a SiO content.
By adding ₂ , the coefficient of thermal expansion tends to increase. Thermal expansion coefficients of Sendust, Permalloy, and iron metal films, which are typical metal magnetic thin films, are 150 × 10 ^-7.
/ ° C, 135 × 10 ^-7 / ° C, 130 × 10 ^-7 / ° C and αF
It is much larger than the coefficient of thermal expansion of e ₂ O ₃ . Here, by adding SiO ₂ to αFe ₂ O ₃ , the coefficient of thermal expansion can be brought close to that of various metal magnetic thin films. On the other hand, the density decreases with the addition of SiO ₂ having a smaller specific gravity than αFe ₂ O ₃ , but if added in a large amount, the sinterability of αFe ₂ O ₃ is impaired. # 5 is SiO ₂
Although 0 wt% was added, the sinterability was low, and it was confirmed that pores and large foreign phases were present in the sintered body.

Next, for samples # 1 to 6 and for comparison, a general non-magnetic substrate of CaTiO ₃ (coefficient of thermal expansion 117 × 10 ⁻⁷ / ° C.) was used, on which a sendust thin film of 4 μm and for bonding were used. A laminated magnetic head was formed by forming glass by sputtering and then joining the non-magnetic substrates. These are samples A-1 to 6 and B.
And Table 2 shows the peeling failure rate and grinding resistance of the metal magnetic thin film during grinding of these magnetic heads with a grindstone. Here, the peeling failure is visually determined, and the comprehensive evaluation is good,
× means unsuitable, Δ means slightly dissatisfied. The grinding resistance was obtained by measuring the resistance value of the grindstone attached to the cutting machine in the Z-axis direction with a strain gauge. The conditions at that time were as follows. Sample size 45 x 10 x 2.7 mm, grindstone: φ102 x 0.6 mm, 400 diamond,
Rotation speed 15,000 rpm, table feed 75 mm / m
in, depth of cut 3.5 mm (from top of sample)

[0020]

[Table 2]

When the residual stress in the metal magnetic thin film becomes large, the adhesive force with the non-magnetic substrate decreases, and peeling defects increase. The largest cause of residual stress is considered to be the thermal stress due to the difference in thermal expansion coefficient between the non-magnetic substrate and the metal magnetic thin film. In Table 2, sample A-6 (αFe ₂ O
₃ ) The peeling failure of ₃ ) was 3/10, while A-1 to 5 was 2 /
The improvement of 10 to 0/10 is a result of the fact that the thermal expansion coefficient of αFe ₂ O ₃ which is the substrate approaches the thermal expansion coefficient of Sendust due to the addition of SiO ₂ and the residual stress in the Sendust thin film becomes small. It is believed that there is. The rate of peeling failure of αFe ₂ O ₃ (A-2 to 5) containing 1% or more of SiO ₂ is equal to or better than that of CaTiO ₃ , which is a practically acceptable level. On the other hand, regarding the grinding resistance value, the samples A-1 to 6 of αFe ₂ O ₃ system have C
It is 1/2 or less of that of the aTiO ₃ substrate B, which means that it is much easier to process than B. One disadvantage is that CaTiO ₃ has poor machinability, but SiO ₂ -added αFe ₂ O ₃ is a non-magnetic substrate with a coefficient of thermal expansion equal to or higher than that of CaTiO ₃ and with much better machinability. It shows a thing. Further, this not only improves the yield, but also has the effect of extending the life of the grindstone used during grinding, leading to cost reduction. Further, A-5 had the lowest grinding resistance in the sample, which is considered to be due to the decrease in strength due to the holes existing in the sintered body.
It is desirable to have as few holes as possible for use as a magnetic head substrate. In this case, A
Too many holes are not suitable for use with -5. Furthermore, considering the peeling failure rate, the addition amount of SiO ₂ is 0.1 w.
It can be said that t% is not sufficient, and an addition amount of 1 wt% or more is necessary. Therefore, as the magnetic head substrate, from the samples A-2 to A4, the added amount of SiO ₂ is 0.1 to 30 w.
t% is a desirable range of use.

[0022]

As described above, by adding an appropriate amount of SiO ₂ to αFe ₂ O ₃ , a nonmagnetic substrate material for a magnetic head having a large thermal expansion coefficient and excellent machinability can be obtained. Further, a non-magnetic substrate material obtained by adding SiO ₂ to αFe ₂ O ₃ has an advantage that it can be manufactured at low cost.

Claims (2)

[Claims] 1. A magnetic head comprising a magnetic core, a non-magnetic material supporting the magnetic core, glass, etc., the surface of which is in sliding contact with or faces the magnetic recording medium, wherein the non-magnetic material contains SiO ₂ αFe ₂ O. _A non-magnetic substrate material for a magnetic head consisting of a sintered body of ₃ . _2. The amount of SiO ₂ contained is 1.0 to 30 w.
The non-magnetic substrate material for a magnetic head according to claim 1, which is t%.