JPH0785419A - Thin film head - Google Patents

Abstract

PURPOSE:To achieve recording/reproducing characteristics with a higher density than in the prior art by improving the initial permeability mu which is a magnetostatic characteristic of a thin film head used in a hard disk drive capable of performing high-density recording. CONSTITUTION:Magnetostriction lambda of an upper core of this thin film head is set to be -2.0X10<-6> to -1.0X10<-6>. Compression stress due to the shrinkage of an insulating resist film is made to be applied to the upper core, so that the initial permeability mu becomes 3700-4000. As compared with a conventional thin film head, this thin film head has a larger initial permeability mu and therefore a larger inductance L. Since the frequency characteristics of recording/ reproducing are improved, the thin film head enables recording/reproduction of data with a higher density than in the prior art. Accordingly, a hard disk drive with a higher recording density than that of a conventional one is provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film head used in a hard disk drive device capable of ultra high density recording.

[0002]

2. Description of the Related Art In recent years, with the increase in recording density of hard disk drive devices, which are magnetic storage devices, thin film heads (inductive heads) have come into practical use as magnetic heads used for recording and reproduction.

The structure of the thin film head will be described below. The structure of the thin film head is the surface (A
As shown in FIG. 1, when viewed from the BS surface), an insulating film (alumina film) 2 is formed on the AlTiC substrate 1 that serves as a slider.
Is formed, and the lower core (FeNi film, permalloy plating film) 3, READ / WRITE gap insulating film (alumina film) 4, upper core (FeNi film, permalloy plating film) 5, protective insulating film (alumina film) ) 6 is formed.

A cross section of the thin film head as viewed in a direction perpendicular to the ABS surface shows a READ / WRITE coil 7 between the lower core 3 and the upper core 5 as shown in FIG. Intervened through.

Lower core 3 and upper core 5 of the thin film head
Generally indicates that the magnetic properties change due to external stress.
In order to avoid, magnetostriction λ is near zero (for example, −0.6 ×
10 ^-6~ + 0.6 × 10^-6) FeNi composition ratio
It is said that it is desirable to select and form a film by plating.
However, the magnetostriction is positive (for example, 0.0 × 10^-6~ +0.6
× 10^-6Fig. 6 (a), that is, the magnetism of the lower core
As shown in the figure showing the magnetic domain structure when the strain λ is positive,
A vertical crack domain wall (a) occurs in the turn, and the recording / reproducing characteristics
In practice, FeNi has a slightly negative magnetostriction.
Since it is desirable to set the composition ratio, magnetostriction λ = 0.0
× 10^-6~ -0.6 x 10^-6At the FeNi composition ratio
It is common to perform plating film formation. Note that FIG.
(B) shows the magnetic domain structure when the magnetostriction λ of the lower core is made negative.
Shows.

[0006]

[Problems to be Solved by the Invention] Here, first,
FIG. 8 shows changes in the initial magnetic permeability μ with respect to the magnetostriction λ of the permalloy plated film. However, the data was measured with no external stress applied to the permalloy plating film,
Data without annealing and annealing (250
Data for 2 hours). The annealing treatment is an unavoidable step in the manufacturing process of the thin film head. As can be seen from FIG. 8, when the annealing treatment is not performed, the initial magnetic permeability has a substantially constant value (about 30%).
Although it is about 00 μ), an annealing treatment (250
It can be understood that the initial magnetic permeability μ becomes about 2800 only in the vicinity of zero of the magnetostriction λ, and gradually decreases with increasing distance from the vicinity of zero when the magnetostriction λ is close to zero. The magnetostriction λ of the film is 0.0 × 10 ^-6
The condition of -0.6 × 10 ^-6 is considered to be the optimum condition.

However, in order to further improve the recording / reproducing sensitivity, it is necessary to further increase the initial permeability μ which is the magnetic characteristic of the permalloy plated film. The present invention has been made in consideration of the above problems, and an object of the present invention is to provide a thin film head that improves the initial magnetic permeability μ, which is a magnetostatic characteristic, and enables a recording / reproducing characteristic with a higher density than ever before.

[0008]

In order to achieve this object, the present invention sets the magnetostriction λ of the upper core to -2.0 × 10 ^-6 ~.
It is a thin film head characterized by being set to -1.0 × 10 ^-6 .

[0009]

By the above means, when a compressive stress is applied as an external stress to the upper core, the initial permeability μ is 3700 to 400.
Since it becomes about 0 and the recording / reproducing sensitivity is improved, it is possible to provide a thin film head capable of extremely high density recording / reproducing as compared with the conventional one.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the thin film head of the present invention is the same as that shown in FIGS.

Here, in the structure shown in FIG. 1, it has been found that the insulating resist 8 is made of a polymer resin, so that the volume is slightly reduced throughout the manufacturing process of the subsequent steps. Therefore, the upper core 3 is affected by the volume reduction of the insulating resist 8 and is in a state where compressive stress is applied from the outside.

Therefore, FIG. 3 shows the results of examining the change in the initial permeability μ with respect to the magnetostriction λ when a compressive stress is applied as the external stress and the change in the initial permeability μ with respect to the magnetostriction λ when the tensile stress is applied. Show. As shown in FIG. 3, when compressive stress is applied, the magnetostriction λ is −2.0 × 10 ⁻⁶
When −1.0 × 10 ⁻⁶ , the initial permeability μ is 3700 to
The maximum value is 4000, and conversely, when tensile stress is applied, the magnetostriction λ is + 1.0 × 10 ⁻⁶ to + 2.0 × 10.
It was found that the initial magnetic permeability was 3700 to 4000, which was the largest when it was ^-6 .

From the above, for the upper core 5,
Since a compressive stress is applied, the magnetostriction λ is -2.0 × 10.
It was estimated that ^-6 to -1.0 × 10 ^-6 was better. Therefore, the magnetostriction λ of the lower core 3 is close to zero (0.0
The inductance L was measured when the magnetostriction λ of the upper core 5 was changed by fixing it to × 10 ^-6 ± 0.5 × 10 ^-6 ). The result at that time is shown in FIG. Since the inductance L and the initial permeability μ are in a proportional relationship, it is well known that the inductance L increases as the initial permeability μ increases. As shown in FIG.
It was found that increases the inductance L is best when magnetostriction λ is ^{-2.0 × 10 -6 ~-1.0 ×} 10 -6. Therefore, the upper core 5 has a magnetostriction λ of −2.0 ×.
It has been found that it is better to set 10 ⁻⁶ to −1.0 × 10 ⁻⁶ .

Next, the lower core 3 was similarly examined. FIG. 5 shows the result of measuring the inductance L by changing the magnetostriction λ of the lower core 3 while keeping the magnetostriction λ of the upper core 5 constant at −1.5 × 10 ⁻⁶ . As shown in FIG.
In the case of the lower core 3, the magnetostriction λ is 0.0 × 10 ⁻⁶ to +1.
It turned out that it became the largest when it was set to 0 × 10 ^-6 .
In the case of the lower core 3, it is considered that tensile stress is applied because the rigidity of the AlTiC substrate 1 and the insulating film (alumina film) 2 is strong, so that the magnetostriction λ is + 1.0 × 10 ⁻⁶ +
I expected it to be 2.0 x 10 ^-6 ,
Actually, when the shape of the core pattern of the thin film head is set as shown in FIG.
As shown in (a) and (b), when the magnetostriction λ is set to be positive, a vertically cracked magnetic domain wall is generated, so it has been found that it is not preferable to set the magnetostriction λ to be positive. Therefore, it was found that the magnetostriction λ of the lower core should be -1.0 × 10 ^{-6 to} 0.0 × 10 ^-6 .

Next, the magnetostriction λ of the upper core is -0.6 × 10.
^{-6 to} 0.0x10 ^-6 thin film head (conventional example),-
A recording frequency characteristic was compared with a thin film head having a ^thickness of 2.0 × 10 ⁻⁶ to −1.0 × 10 ⁻⁶ (Example). FIG. 7 is a diagram showing the recording frequency characteristics when the recording frequency is on the horizontal axis and the reproduction output is on the vertical axis. As shown in FIG. 7, it is clear that the thin film head of the present invention (example) has a clearly higher density and a higher reproduction output than the conventional thin film head (conventional example).

As described above, the thin film head of the present invention can obviously perform recording and reproducing at a higher density than the conventional one.

[0017]

As is clear from the description of the above embodiment, in the thin film head of the present invention, the magnetostriction λ of the upper core is −2.0 × 1.
By setting 0 ^-6 to -1.0 x 10 ^-6 , the initial permeability μ
Since 3700 to 4000 can be obtained, it is possible to record and reproduce at a higher density than in the past. As a result, it has become possible to provide a hard disk drive device having a higher density than ever before.

[Brief description of drawings]

FIG. 1 is a diagram showing a structure of a thin film head when viewed from an ABS surface.

FIG. 2 is a sectional view of the thin film head cut perpendicularly to the ABS surface.

FIG. 3 is a diagram showing changes in initial permeability μ with respect to magnetostriction λ when an external stress is applied.

FIG. 4 is a diagram showing a change in the inductance L when the magnetostriction λ of the upper core is changed.

FIG. 5 is a diagram showing changes in the inductance L when the magnetostriction λ of the lower core is changed.

6A is a diagram showing a magnetic domain structure when the magnetostriction λ of the lower core is positive, and FIG. 6B is a diagram showing a magnetic domain structure when the magnetostriction λ of the lower core is negative.

FIG. 7 is a diagram showing recording frequency characteristics of a conventional example and an example.

FIG. 8 is a diagram showing changes in initial permeability μ with respect to magnetostriction λ when no external stress is applied.

[Explanation of symbols]

1 Altic substrate that serves as a slider 2 Insulating film (alumina film) 3 Lower core 4 READ / WRITE gap insulating film (alumina film) 5 Upper core 6 Protective insulating film (alumina film) 7 READ / WRITE coil 8 Insulating resist film

Claims (2)

[Claims] 1. An insulating film is formed on an AlTiC substrate, and a lower core, a READ / WRITE gap insulating film, an upper core, and a protective insulating film are formed on the insulating film, and a READ / write layer is formed between the lower core and the upper core. The coil for WRITE is provided via an insulating resist film, and the magnetostriction λ of the upper core is −2.0 × 10 ⁻⁶ to −1.0 × 10 ^16.
Is a thin film head. 2. An insulating film is formed on an AlTiC substrate, and a lower core, a READ / WRITE gap insulating film, an upper core, and a protective insulating film are formed on the insulating film, and a READ / write layer is formed between the lower core and the upper core. A coil for WRITE is provided via an insulating resist film, and the magnetostriction λ of the lower core is −1.0 × 10 ^{−6 to} 0.0 × 10 ⁻⁶ and the upper core has a magnetostriction λ of −1.0 × 10 ^{−6 to} 0.0 × 10 ⁻⁶ . Magnetostriction λ is -2.0 × 10 ^-6 ~
A thin film head characterized in that the ^thickness is −1.0 × 10 ⁻⁶ .