JP2867416B2 - Magnetoresistive head - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to magnetic information written on a magnetic storage medium.
The present invention relates to a magnetoresistive head (hereinafter, abbreviated as an MR head) including a ferromagnetic magnetoresistive element (hereinafter, abbreviated as an MR element) that reads out using the ferromagnetic magnetoresistance effect.

[Prior Art] As is well known, when an MR element is used as a high-efficiency reproducing head exhibiting linear response to magnetic information written in a magnetic storage medium, a sense current I flowing through the MR element is used. And a bias means for setting an angle θ (hereinafter, referred to as a bias angle) between the magnetic field M and the magnetization M of the MR element to a predetermined value (preferably 45 degrees).

Various methods have been disclosed as the bias means described above. For example, US Pat. No. 3,864,751 discloses a structure in which a soft magnetic bias auxiliary layer and an MR element are stacked with an insulating layer interposed therebetween. In the reference, while supplying a sense current to the MR element to magnetize the soft magnetic bias auxiliary layer,
A method of applying a bias magnetic field to an MR element with a magnetic field generated by a soft magnetic bias auxiliary layer is shown.

As another bias means, Japanese Utility Model Laid-Open No. 60-159518 discloses a structure in which an amorphous soft magnetic bias auxiliary layer and an MR element are laminated with a nonmagnetic conductor layer interposed therebetween. In this configuration, the specific resistance of the amorphous soft magnetic bias auxiliary layer is MR
Since the specific resistance is significantly higher than the specific resistance of the element, most of the sense current flows through the MR element, and a bias effect equivalent to the configuration in which the amorphous soft magnetic bias auxiliary layer and the MR element are effectively isolated is obtained. Can be Further, in this bias method, it is not necessary to maintain the insulation between the amorphous soft magnetic bias auxiliary layer and the MR element, so that a compact magnetoresistive head with a thin nonmagnetic conductor layer is formed.

[Problems to be Solved by the Invention] By the way, in the MR head having the above-mentioned structure, that is, the structure in which the NR element, the nonmagnetic conductor layer and the bias auxiliary layer are stacked, the characteristic of the bias auxiliary layer is larger than that of the MR element. It is required that the rate of change in magnetoresistance, the specific resistance, and the soft magnetic properties be excellent (The Journal of Applied Physics)
Applied Physics), 1988, Vol. 63, p. 4023). For this reason, CoZr, CoZrNb, CoZ
Amorphous soft magnetic materials such as ZrMo, CoZrTa, and CoTa have been used.

However, in this case, the magnetic properties deteriorated due to the thermal instability of the amorphous material. That is, during operation as a magnetic head, a sense current always flows through the MR head, so that the temperature of the MR head increases due to electric resistance. If the amorphous soft magnetic material is used for a long time in such a state, the magnetic properties of the amorphous soft magnetic material gradually deteriorate, the anisotropic magnetic field increases, and the magnetization of the amorphous soft magnetic material layer does not rotate sufficiently. , A good bias level could not be realized. For this reason, there is a problem that the linear response of the MR head is impaired and the reproduction efficiency is reduced.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetoresistive head which eliminates the above-mentioned disadvantages of the prior art, has excellent long-term reliability, and has a high reproduction efficiency.

Means for Solving the Problems According to the present invention, a ferromagnetic magnetoresistive element and a soft magnetic bias auxiliary layer are laminated via a non-magnetic conductor layer, and the soft magnetic bias auxiliary layer contains FeSi as a main component. This is a magnetoresistive effect head characterized by being made of an alloy having a characteristic as follows.

In the present invention, the content of Si in FeSi is 5 to 15% by weight.
Then, particularly excellent characteristics can be obtained.

[Operation] The thermal instability can be improved by using a crystalline alloy material instead of an amorphous material as the soft magnetic bias auxiliary layer, but the specific resistance of the normal alloy material is used in the MR element part. Since the current is about the same as that of a NiFe alloy, a NiCo alloy, or the like, the sense current is also diverted to the bias auxiliary layer, and the read efficiency of the head is reduced. In addition, materials containing elements such as Co and Ni show a relatively large change in magnetoresistance, which causes noise.

In the present invention, an alloy mainly composed of FeSi having a large specific resistance and a small magnetoresistance change rate is used as the soft magnetic bias auxiliary layer.

It is well known that the addition of Si to Fe improves the soft magnetic properties and increases the specific resistance. (Toshinobu Chikaku, Physics of Ferromagnetics, Shokabo, published in 1984, lower volume p. 369) ), Since the mechanical strength decreases with an increase in Si, only a soft magnetic material having a composition having a Si content of 1 to 5% by weight is used. However, when used as a bias auxiliary layer of the magnetoresistive head of the present invention,
Since it is formed as a thin film and has a structure laminated with another thin film, a decrease in mechanical strength is not a problem, and a wide composition range can be used.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a perspective view of an example of the magnetoresistive head according to the present invention. As shown in FIG. 1, an MR element 2 made of a ferromagnetic material such as NiFe or NiCo is formed on a non-magnetic substrate 1 having a smooth surface made of glass, ferrite, or the like by sputtering or vapor deposition. I do. Next, T
A nonmagnetic conductor layer 3 of i, Mo, Cr, Ta, etc. is formed in the same manner as described above, and a soft magnetic bias auxiliary layer 4 made of an alloy containing FeSi as a main component is formed on the nonmagnetic conductor layer 3 as described above. It is formed by a similar method. In the figure, reference numeral 5 denotes a terminal for supplying a current to the MR element 2, the nonmagnetic conductor layer 3, and the soft magnetic bias auxiliary layer 4.

Fig. 2 shows the results of a trial production of MR heads using FeSi thin films of various compositions as bias assist layers, and comparing the magnetoresistance ratio with the case where CoZrTa, an amorphous soft magnetic thin film, was used as the bias assist layer. It is. In the figure, a shows the case where FeSi is used as a bias auxiliary layer, and b shows the case where CoZrTa is used as a bias auxiliary layer. The MR head used in this experiment was manufactured as follows.

Using a vapor deposition method on a glass substrate, a film thickness of 40
A 0 ° permalloy (Ni 82 wt% -Fe 18 wt%) film was formed. During the vapor deposition, a magnetic field of 100 Oe was applied by a permanent magnet to impart uniaxial anisotropy on the permalloy film. Then
Similarly, using a vapor deposition method, a T
An i film was formed on the permalloy film. Further film thickness 300 mm
Was formed on the above-mentioned Ti layer by a sputtering method. At this time, for the FeSi, a Si piece was placed on the Fe target, and the Si composition was changed by the number of the Si pieces. Thereafter, a predetermined photoresist pattern is formed on this laminate, and Ar
Ion etching was performed in a gas atmosphere to form a rectangular pattern having a length of 50 μm and a width of 5 μm. Next, terminals for supplying a sense current to the above-described laminate were formed using a laminate film of Ti and Au. A sense current of 10
mA was applied to apply an external magnetic field, and the magnetoresistance ratio was measured.

As is clear from FIG. 2, in the range of 5 to 15% by weight of the Si composition, the MR head using the FeSi film has a magnetoresistance change equivalent to or higher than that using the amorphous film. . This is based on the fact that the specific resistance of FeSi is larger than that of CoZnMo. On the other hand, the decrease in the magnetoresistance ratio in the head in which the Si content exceeds 15% by weight is due to the decrease in the soft magnetic characteristics of the FeSi film.

Next, a decrease in sensitivity with time was measured as follows using an MR head using the FeSi film manufactured by the above method and having a composition of 8% by weight of Si and an MR head using a CoZrMo film.

A sense current of 10 mA was passed through the two MR heads to measure the normalized sensitivity to an external magnetic field. The sensitivity immediately after the start of the measurement was almost the same as 0.03 / Oe for both heads, but the sense current was kept flowing as it was, and the decrease in sensitivity with time was measured. FIG. 3 shows the results. In the figure, A is a case where an FeSi film is used as a bias auxiliary layer, and B is CoZrMo.
The case where a film is used is shown.

As is clear from FIG. 3, the MR head of the present invention has stable performance without any decrease in sensitivity even after long-term use.

[Effects of the Invention] As described above, according to the present invention, there is an effect that a magnetoresistive head having excellent long-term reliability and high reproduction efficiency is provided.

[Brief description of the drawings]

FIG. 1 is a perspective view of an example of a magnetoresistive head according to the present invention,
FIG. 2 is a diagram showing the Si composition dependence of the magnetoresistance ratio of an MR head using a FeSi thin film as a bias auxiliary layer, and FIG.
FIG. 6 is a diagram showing a change over time in the reproduction sensitivity of the MR head. DESCRIPTION OF SYMBOLS 1 ... Nonmagnetic substrate 2 ... Magnetoresistance effect element 3 ... Nonmagnetic conductor layer 4 ... Soft magnetic bias auxiliary layer 5 ... Terminal

Claims (1)

(57) [Claims] 1. A ferromagnetic magnetoresistive element and a soft magnetic bias auxiliary layer are laminated via a non-magnetic conductor layer, and the soft magnetic bias auxiliary layer is made of FeSi. A magnetoresistive head characterized by 15% by weight.