JPH03268215A - Magnetoresistance effect type head - Google Patents

Abstract

PURPOSE:To obtain a shunt film having excellent heat resistance by constituting the shunt film which consists of two layers of a specified Ni-Fe alloy film and a W film contg. unavoidable impurities and the W film of which impresses a bias magnetic field to the Ni-Fe alloy film. CONSTITUTION:The Ni-Fe film contg. 15 to 23wt.% Fe is formed by an electron beam vapor deposition method on a glass substrate. The W film contg. the unavoidable impurities is formed by an electron beam vapor deposition method on this Ni-Fe film without breaking vacuum in succession to the above. The heat resistance of the shunt film, the W film of which impresses the bias magnetic field to the Ni-Fe film, is improved in this way and the magnetoresistance effect type head optimum for high-density magnetic recording is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetoresistive head, and particularly to a magnetoresistive head that is optimal for high-density magnetic recording.

[Conventional technology]

The shunt film of the conventional shunt bias type magnetoresistive head contains Ti and Ta as described in U.S. Pat.
Zr was used as described in the publication.

[Problem to be solved by the invention]

In the above conventional technology, in the shunt bias type magnetoresistive head using Ti, when the temperature exceeds 175°C (2), the Ni-Fe alloy (hereinafter referred to as permalloy) is used.
A reaction occurs between the film and Ti, resulting in deterioration of the characteristics of the permalloy film, which is a magnetoresistive film. In addition, in a head using Zr as a shunt film, the lower limit temperature for reaction with the permalloy film is 32
Although the temperature has been improved to 5°C, it is still low considering the temperature conditions of various processes for manufacturing the head. Ta has a high reaction initiation temperature with permalloy of 350°C, but compared to permalloy and Ti, Ta thin films have poor corrosion resistance and an electrical resistivity of 9.
It is extremely high, 0 to 2 CoμΩ■, and is inappropriate as a shunt membrane.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetoresistive head having a shunt film excellent in heat resistance and suitable for the shunt magnetoresistive head.

[Means to solve the problem]

The above object is achieved by using a W film which has a high reaction initiation temperature with the permalloy film and whose electrical resistance is suitable for a shunt structure.

[Function] What kind of metal film is suitable as a combination film (3) must be evaluated by actually fabricating elements using various thin films. From a reaction standpoint, since the reaction is dominated by thermal activation of atoms, metals with high melting points are desirable. At the same time, it is also necessary to have excellent corrosion resistance. W has excellent properties in the above points.

〔Example〕

Example 1 A permalloy thin film having a composition of Ni-19wt%Fe was formed on a glass substrate by electron beam evaporation. The thickness of permalloy is 4Co. On this permalloy thin film, a W thin film of approximately 7 Co was subsequently deposited by electron beam evaporation without breaking the vacuum.

This two-layer film is hereinafter referred to as a W/permalloy film.

In order to compare with this sample, a permalloy film having the same composition as above was formed on the same type of glass substrate, and then a Ti/permalloy film was produced by vapor-depositing a Ti film.

In order to compare these samples under the same conditions, 10 ””
They were placed together in a Torr vacuum furnace and heat treated (4).

FIG. 1 shows the change in the coercive force of the permalloy film with respect to the heat treatment temperature. As is clear from Fig. 1, T i
/The coercive force of the permalloy two-layer film begins to increase when the heat treatment temperature becomes 225° C. or higher. This indicates that the vapor properties of the permalloy film are degraded due to mutual diffusion between Ti and the permalloy film. On the other hand, the coercive force of permalloy in the W/permalloy film shows no change up to 4Co°C, and increases slightly at 425°C or higher, indicating that a reaction occurs between the films.

As is clear from the above examples, W has a reaction temperature about 2 Co° C. higher than that of Ti, and has a remarkable effect on improving the heat resistance of permalloy, a two-layer film made of permalloy and metal.

Example 2 2 of each of Ti/permalloy and W/permalloy
We compared the magnetic reproduction characteristics of shunt-type magnetoresistive heads fabricated using layered films. In the reproduced waveform (5) after heat-treating the fabricated head at 225° C., there was significant noise that was thought to be due to the Bakkuusen effect, whereas similar noise was not observed in the head using the W/permalloy film.

In a head using a Ti/permalloy film, if the heat treatment temperature exceeds 275° C., reproduction output cannot be obtained. On the other hand, in a head using W, the reproduction output is normal even after heat treatment at 4Co°C, but noise increases when the temperature exceeds 425°C.

The specific resistance of a Ti film obtained by ordinary electron beam evaporation is 5
5~60μΩ■, while W is 10~15μΩG
A value of about 1/2 to 1/3 is obtained. Therefore, the thickness of the shunt bias film can be reduced to about 172 to 1/3 that of Ti.

This also has the advantage that when manufacturing a shielded magnetoresistive head, the distance between the shields (usually called a gap) can be narrowed by the reduction in the thickness of the shunt film.

The W/Permalloy two-layer film can be similarly implemented using any driving method such as a two-terminal element or a three-terminal differential type element.

(6) Example 3 A magnetoresistive element consisting of a W/permalloy two-layer film was produced,
The influence of the magnetostriction constant of permalloy was investigated. The magnetostriction constant of permalloy changes depending on the composition, and Ni-18,5
It becomes zero near wt% Fe.

Generally, it is difficult to obtain a film with a magnetostriction constant of zero;
A permalloy film with a magnetostriction constant of the order of magnitude is used.

When a two-layer film is used, strain is applied to the permalloy film due to the thermal expansion coefficient and internal strain of the shunt bias film.
The magnetic properties of the permalloy film change. Therefore, the composition of the permalloy film used varies depending on the material, formation method, film thickness, etc. of the shunt film.

As a result of the above study on the W/permalloy film, we found that the effect of strain from the W film does not have a large effect on the magnetoresistive properties of the permalloy film when Fe is 15 to 23 wt%.
Containing permalloy.

Example 4 Ni: 77-85 wt%, Co: 1-10 wt%, (7
) A magnetoresistive element was manufactured in the same manner as in Example 1 using a Ni--Fe--Co alloy film consisting of the remaining Fe and a W film, and as a result, an element exhibiting practically usable electromagnetic characteristics was obtained. In a composition range other than the above, the electromagnetic properties deteriorate significantly due to the magnetostriction constant, etc., making it unsuitable for practical use.

Example 5 In order to increase the bias effect, a soft magnetic Co-Ta-Zr or Co-Mo-Zr amorphous film of about 30 nm was formed adjacent to the W of the W/permalloy two-layer film. The bias amount of the permalloy film increased by 10 to 2 Coe compared to the case of only the W shunt film. F
Similar effects can be obtained with the e-A Q-8i soft magnetic film.

〔Effect of the invention〕

According to the present invention, the heat resistance temperature of the shunt-biased permalloy magnetoresistive element can be increased by 2Co to 250°C compared to the conventional T i /permalloy system, so that the process for manufacturing a magnetic head using the material can be improved. 2Co to 250°C higher than before (8). For this reason, the adhesion between the permalloy film and the base.

Adhesion with oxide insulating film on W/permalloy film.

The characteristics of vapor-deposited permalloy thin films for shielding have been improved, and damage to devices due to electromigration has been significantly reduced. As a result, the yield of devices is improved, the defective rate is reduced,
It had a remarkable effect on reducing the occurrence of breakdowns during use.

[Brief explanation of drawings]

FIG. 1 is a measurement diagram showing the influence of heat treatment temperature on the coercive force of a permalloy film of a Ti/permalloy and W/permalloy two-layer film according to an embodiment of the present invention.

Claims (1)

[Claims] 1. Consisting of a two-layer film of a Ni-Fe alloy film containing 15 to 23 wt% Fe and a W film containing unavoidable impurities, the W film applies a bias magnetic field to the Ni-Fe alloy film. A magnetoresistive head comprising a shunt film. 2. Ni-Fe-Co consisting of 77-85 wt% Ni, 1-10% Co, and the rest Fe and unavoidable impurities
It consists of two layers: an alloy film and a W film, and the W film is Ni-Fe-C.
A magnetoresistive head comprising a shunt film that applies a bias magnetic field to an o-alloy film. 3. Magnetoresistive effect characterized by a soft magnetic film for bias being placed in contact with the W film of a two-layer film consisting of a Ni-Fe alloy film and a W film, and a Ni-Fe-Co alloy film and a W film. type head. 4. A magnetoresistive head characterized in that an alloying element dissolved in solid solution is added to the W film in order to reduce the internal stress of the W film. 5. A magnetoresistive head, characterized in that the lead portion for supplying current to the magnetically sensitive part of the magnetoresistive head is also made of the multilayer film described in claims 1 to 4.