JPH05314431A - Thin-film magnetic head - Google Patents

Abstract

PURPOSE:To improve the corrosion resistance of a yoke, and to allow the yoke to have uniaxial anisotropy by containing a fixed quantity of Nb in permalloy. CONSTITUTION:A lower yoke 3 composed of a ferromagnetic thin-film such as permalloy is formed onto a substrate 1 consisting of a ferromagnetic material such as permalloy, and upper yokes 5a, 5b made up of the same material are formed onto the lower yoke 3. A bias wire 9 and an MR element 7 are shaped among the yoke 3 and the yokes 5a, 5b, the MR element 7 is brought to the state of a single-magnetic domain, and the direction of magnetization is changed into uniaxial anisotropy. An inter-layer insulating film 15c is formed between the lower yoke 3 and the bias wire 9, an inter-layer insulating film 15b between the bias wire 9 and the MR element 7 and an interlayer insulating film 15a among the MR element 7 and the upper yokes 5a, 5b. Nb is contained in permalloy at 1at.% to 5at.%. Uniaxial anisotropy is dissipated when Nb in permalloy is too increased, and corrosion resistance is deteriorated when Nb is too reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses a magnetoresistive effect element (hereinafter referred to as an MR element) which applies the magnetoresistive effect of a ferromagnetic thin film to a signal recorded on a magnetic recording medium such as a magnetic disk device or a magnetic tape device. The present invention relates to a magnetoresistive thin-film magnetic head for reproducing information.

[0002]

2. Description of the Related Art Conventionally, since a thin film magnetic head is a magnetic induction type winding type head for recording and reproducing is also performed by a head having the same structure, it is necessary to increase the number of conductor coils passing through a magnetic core. However, it has been very difficult to realize this with a thin film forming technique.

On the other hand, it is known that a thin film magnetic head utilizing the magnetoresistive effect of a ferromagnetic thin film has many advantages as compared with the winding type head. That is,
Even if the transfer speed of the magnetic recording medium is low, an output that is directly proportional to the magnetic flux can be obtained, so that the signal can be reproduced without depending on the transfer speed. There is an advantage that an output reproduction signal can be obtained.

In practical application, the MR element portion is separated from the head end of the thin film magnetic head, and the magnetic flux generated in the magnetic recording medium is MR-converted rather than forming the thin film magnetic head with the MR element alone.
A thin-film magnetic head called a yoke type MR head (hereinafter referred to as YMR head) in which a magnetic flux introduction path (hereinafter referred to as yoke) leading to the element portion is arranged is more effective in improving signal resolution and MR element durability. It is known that there is (for example, the Japan Applied Magnetics Society 39th Research Group Material P61
-See P72 "Thin film MR head").

FIG. 1 is a perspective view of a conventional thin film YMR head. A lower yoke 3 made of a ferromagnetic thin film such as permalloy is formed on a substrate 1 made of a ferromagnetic material such as permalloy. On the lower yoke 3, upper yokes 5a and 5b made of the same material as the lower yoke are formed.

A bias line 9 and an MR element 7 are formed between the lower yoke 3 and the upper yokes 5a and 5b.
Lead wires 13 a and 13 b are formed at both ends of the MR element 7. The MR element 7 is in a single domain state, and the magnetization direction is uniaxially anisotropic.

FIG. 2 is a sectional view of the thin film YMR head shown in FIG. The same parts as those shown in FIG. 1 are designated by the same reference numerals. An interlayer insulating film 15c is formed between the lower yoke 3 and the bias line 9. An interlayer insulating film 15b is formed between the bias line 9 and the MR element 7. An interlayer insulating film 15a is formed between the MR element 7 and the upper yokes 5a and 5b. Upper yoke 5a
A gap 17 is formed between the upper yoke 5b and the upper yoke 5b. A front gap 11 is formed between the upper yoke 5a and the lower yoke 3.

The operation of the conventional thin film YMR head will be briefly described with reference to FIG. The magnetic field of the magnetic tape is the upper yoke 5.
The direction of magnetization of the MR element 7 is affected via a. That is, the magnetization direction of the MR element 7 rotates in the direction of the magnetic field of the upper yoke 5a. The lead wires 13a and 13b pick up this as a signal.

[0009]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention As shown in FIG.
In order to keep the R element in the single domain state, the upper yoke 5a,
5b must be in the state of the return magnetic domain. That is,
As shown in FIG. 4, when the upper yokes 5a and 5b are not in the free magnetic domain state, the magnetic field 19 leaks from the upper yokes 5a and 5b. In this magnetic field 19, the MR element 7 has a magnetic domain 2
1 occurs. As a result, the lead wire 13 shown in FIG.
Noise occurs in the signal passing through a and 13b. The upper yokes 5a and 5b must have uniaxial anisotropy in order for the magnetic domains to be in the return magnetic domain state.

Further, referring to FIG. 2, the magnetic tape comes into contact with the portions of upper yoke 5a and lower yoke 3 which form front gap 11. If this portion is corroded by moisture in the atmosphere, the magnetic tape and the upper yoke 5a
The distance to the (lower yoke 3) increases and the output decreases.

The present invention has been made to solve the above conventional problems. An object of the present invention is to provide a thin film magnetic head provided with a yoke having corrosion resistance and uniaxial anisotropy.

[0012]

In a thin film magnetic head formed by forming a magnetic circuit by a lower magnetic core made of a magnetic substrate or a substrate coated with a permalloy film and an upper magnetic core made of a permalloy film, The permalloy contains Nb in an amount of 1 at% or more and 5 at% or less.

[0013]

When the amount of Nb in permalloy is too large, the uniaxial anisotropy is lost, and when it is too small, the corrosion resistance decreases. It is described in Examples that the amount of Nb in permalloy is preferably 1 at% or more and 5 at% or less.

[0014]

[First Embodiment] First, binary permalloy
Corrosion resistance when niobium is added)
Will be improved. Permalloy is a DC 3-pole spa
It was formed by the Tatta method. The conditions are Ar pressure of 5 mTorr and Ta
Target voltage is 200V, target current is 0.6A,
Bias voltage applied to the substrate on which the permalloy film is formed
Was set to -175V. The following 5 types of targets are available
It was Ni₈₃Wt% Fe ₁₇Weight percent target. Ni₈₃Heavy
Amount% Fe₁₇Place Cr pellets on the target of weight%
What Ni₈₃Wt% Fe₁₇M on wt% target
o Pellet on top. Ni₈₃Wt% Fe₁₇Wt%
Nb pellets placed on the target. Ni₈₃weight
% Fe₁₇Put V pellets on the target of weight%
of. The thickness of the permalloy film was set to about 1 μm.

On the permalloy film thus prepared,
A corrosion resistance test (JIS G 0578) using a ferric chloride aqueous solution (6%, liquid temperature 50 ° C.) was performed. Then, the surface of the permalloy film was observed using an optical microscope. The result is shown in Fig. 5.
Shown in. ○ indicates almost no corrosion, ×
Indicates that it was considerably corroded, and Δ indicates the middle between ○ and ×. As can be seen from FIG. 5, it can be seen that the corrosion resistance is improved by adding Nb to permalloy.

Next, the addition amount of Nb in permalloy is 1 at
% To 5 at% is preferable. A Nb-added permalloy film was formed using the same method as above. The amount of Nb in the permalloy film was adjusted by the amount of Nb pellets placed on the target. Regarding the corrosion resistance, the test of JIS G 0578 described above was used. Whether it was uniaxial anisotropy was evaluated by a BH loop tracer. Results are shown in FIG. In the case of −axis anisotropy, it is indicated by ◯, otherwise it is indicated by x.

As can be seen from FIG. 6, if the amount of Nb in permalloy is 1 at% or more, it has corrosion resistance. Further, when the amount of Nb added in permalloy was 3 at%, it had uniaxial anisotropy, and when it was 5.9 at%, it did not have uniaxial anisotropy. From this, the inventor presumed that when the added amount of Nb in permalloy exceeds 5 at%, it does not have uniaxial anisotropy. The present invention can be applied to both the upper yoke and the lower yoke.

Further, although the magnetic core of the magnetoresistive thin film magnetic head has been described in the present embodiment, the permalloy film according to the present invention is not limited to the magnetic core of the magnetoresistive thin film magnetic head, and may be wound. Linear thin film magnetic head, etc.
It can also be used for the magnetic core of other types of magnetic heads.

[0019]

According to the present invention, Nb is contained in permalloy, which is a material of the yoke, in an amount of 1 at% or more and 5 at% or less, so that the corrosion resistance of the yoke can be improved and the yoke becomes uniaxially anisotropic. can do.

[Brief description of drawings]

FIG. 1 is a perspective view of a conventional thin film YMR head.

FIG. 2 is a cross-sectional view of FIG.

FIG. 3 is a partial plan view of an upper yoke in a return magnetic domain state.

FIG. 4 is a partial plan view of an upper yoke that is not in a return magnetic domain state.

FIG. 5 is a diagram showing a graph showing a relationship between additives in permalloy and corrosion resistance.

FIG. 6 is a graph showing the relationship between the amount of Nb added in permalloy, corrosion resistance, and uniaxial anisotropy.

[Explanation of symbols]

 3 Lower yoke 5a, 5b Upper yoke 7 MR element 11 Head gap

Claims (1)

[Claims] 1. A thin film magnetic head formed by forming a magnetic circuit with a lower magnetic core made of a magnetic substrate or a substrate coated with a permalloy film, and an upper magnetic core made of a permalloy film. A thin film magnetic head comprising Nb in an amount of 1 at% or more and 5 at% or less.