JP2000173021A - Magnetoresistance effect element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetoresistance effect element for easily controlling an inter-layer connecting magnetic field acting between ferromagnetic films. SOLUTION: An Mn system alloy film containing at least one kind of elements among Ru, Rh, Pd, Ag, Os, Ir, Pt, and Au as a base layer 11 is provided between a magnetoresistance effect film having at least two ferromagnetic films 12 isolated by non-magnetic films 13 and a substrate 10. Thus, ferromagnetic magnetostatic connection between the magnetic layers can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetoresistive element for detecting a magnetic signal.

[0002]

2. Description of the Related Art A magnetoresistive film (hereinafter referred to as A) using an anisotropic magnetoresistance (AMR) effect is used as a sensor for detecting a magnetic signal, including a reproducing head in a magnetic recording / reproducing apparatus.
MR film) is widely used.

[0003] For example, in order to realize a higher density of a magnetic recording / reproducing apparatus, a magnetic sensor is desired to have higher sensitivity reproducing characteristics.

In recent years, research and development of a magnetoresistive film (hereinafter, referred to as a GMR film) utilizing a giant magnetoresistance (GMR) effect has been promoted as a technique to meet such a demand. The GMR effect is a phenomenon in which the electric resistance changes according to the relative angle of the magnetization of the magnetic film separated by the non-magnetic film. The amount of change in electric resistance of the GMR film is extremely large as compared with that of the AMR film, and the performance as a magnetic sensor can be dramatically improved.

Japanese Patent Application Laid-Open No. 2-61572 describes a magnetic sensor using an antiferromagnetically coupled multilayer film in which ferromagnetic films and nonmagnetic films are alternately laminated. In the multilayer film disclosed in this disclosure, in the absence of an external magnetic field, the ferromagnetic films separated by the nonmagnetic film are antiferromagnetically coupled, and the magnetization is antiparallel arranged.

When an external magnetic field is applied to the multilayer, the magnetization changes from an antiparallel arrangement to a parallel arrangement, and in this process, the electric resistance of the multilayer changes. Therefore, if an electrode, a power supply, and an output signal detecting means are attached to this multilayer film, it operates as a magnetic sensor that outputs a magnetic signal as a change in voltage or current. Until now, various types of multilayer films have been studied for antiferromagnetic coupling acting between ferromagnetic films and the resulting resistance change.

[0007]

In the antiferromagnetically coupled multilayer film described above, in the absence of an external magnetic field, antiferromagnetic coupling is realized between ferromagnetic films separated by a nonmagnetic film. Need to be. In general, there is an interlayer coupling that occurs in two modes between ferromagnetic films of a multilayer film in which ferromagnetic films and nonmagnetic films are alternately stacked. One is an interlayer bond that acts via conduction electrons. This is antiferromagnetic or ferromagnetic depending on the material and thickness of the ferromagnetic film and the nonmagnetic film. The other is ferromagnetic magnetostatic coupling created by unevenness at the interface of the film.

In the case where the conditions for forming the multilayer film are inappropriate and the latter ferromagnetic magnetostatic coupling is dominant, even if the materials and film thicknesses of the ferromagnetic film and the non-magnetic film are optimized, it is not In some cases, ferromagnetic interlayer coupling cannot be obtained. It is extremely difficult to control the ferromagnetic magnetostatic coupling with good reproducibility, and a great deal of effort is often required.

SUMMARY OF THE INVENTION An object of the present invention is to suppress the ferromagnetic magnetostatic coupling between ferromagnetic films and easily and reproduce the antiferromagnetic coupling acting between ferromagnetic films via conduction electrons. An object of the present invention is to provide a magnetoresistive element that can be realized with good performance.

[0010]

The above object can be attained by providing an appropriate base film.

More specifically, Ru, Rh,
This problem can be solved by providing a Mn-based alloy film containing at least one element among Pd, Ag, Os, Ir, Pt, and Au to suppress ferromagnetic magnetostatic coupling between magnetic layers.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 schematically shows a cross section of a magnetoresistive element according to the present invention. It comprises a magnetoresistive film in which a base film 11 is provided on a substrate 10 and a ferromagnetic film 12 and a nonmagnetic film 13 are sequentially formed a plurality of times, an electrode 14, and a power supply and signal detecting means 15. Of course, the order of lamination may be the nonmagnetic film 13 / ferromagnetic film 12. The ferromagnetic film 12 / non-magnetic film 13 may be laminated as long as the ferromagnetic film 12 includes at least two layers, and a so-called sandwich film structure of the ferromagnetic film 12 / non-magnetic film 13 / ferromagnetic film 12 is formed. It is good.

Substrates / Ta (5) / MnPt (15) / CoFe
(2) / Cu (2.1) / CoFe (1) / NiFe
(3) / Ta (5). The numerical value in parentheses indicates the film thickness, and the unit is nm. The composition of each alloy film is Mn60-
Pt40, Co90-Fe10, Ni81-Fe19, and the composition unit is at%. The non-magnetic film Cu (2.
The structure of the ferromagnetic film separated by 1) is CoFe
Although different from (2) and CoFe (1) / NiFe (3), they do not cause any problem. Further, in order to prevent surface oxidation, a protective film such as Ta (3) may be formed on the uppermost layer.

The magnetoresistive film shown in FIG. 1 was formed in an Ar atmosphere using a DC magnetron sputtering apparatus. When forming a magnetoresistive film, a pair of permanent magnets installed at both ends of the substrate apply a DC magnetic field of about 100 Oe at the center of the substrate to induce uniaxial anisotropy in the ferromagnetic film. did. Each film thickness was controlled in advance by measuring a film formation rate and opening and closing a shutter provided between the target and the substrate.

FIG. 2 shows that (a) Ta (5),
(B) Magnetoresistive film CoFe (2) / Cu (2.1) / CoFe using Ta (5) / MnPt (15) respectively
3 shows a magnetoresistance effect curve of (1) / NiFe (3) / Ta (3). Conventionally, Ti, Zr, Hf, Nb, Ta, and the like are known to have an effect of controlling the orientation of NiFe, CoFe, Cu, and the like, and are often used as a base film, as shown in FIG. The magnetoresistance effect film using Ta (5) as a base film has a very small magnetoresistance change rate.

This is because the ferromagnetic magnetostatic coupling between the ferromagnetic films strongly acts, so that the antiparallel arrangement of magnetization due to the antiferromagnetic coupling via conduction electrons is not sufficiently realized. It is. It is presumed that one of the causes is that the unevenness of the interface of the laminated film generated at the crystal grain boundary or the like is affecting.

On the other hand, in a magnetoresistive effect film having Ta (5) / MnPt (15) as a base film, near zero magnetic field,
Antiferromagnetic coupling sufficient to cause the magnetizations of the ferromagnetic films via the nonmagnetic film to be antiparallel to each other acts between the ferromagnetic films, and a magnetoresistance ratio of about 7% is obtained. . That is, it is expected that by replacing the underlayer film, the unevenness of the interface of the laminated film was reduced, and the ferromagnetic magnetostatic coupling between the ferromagnetic films could be suppressed.

FIG. 3 shows the change in the resistance change rate ΔR / R with respect to the Mn content in MnPt as a result of changing the composition of the MnPt alloy of the underlayer. The film configuration is Ta (5) / MnPt (15) / C, as described above.
oFe (2) / Cu (2.1) / CoFe (1) / NiF
e (3) / Ta (3). Antiferromagnetic coupling is obtained stably over a wide composition range of the MnPt alloy.
As the content increases, the rate of change in resistance ΔR / R
Is getting bigger.

This is because as the Mn content is increased,
One of the causes is that the electrical resistivity of the MnPt alloy increases and the shunt loss due to the underlying film decreases. At the same time, when the Mn content is increased, the saturation magnetic field tends to increase, and the antiferromagnetic coupling seems to increase. The composition of the MnPt alloy can be arbitrarily selected depending on the specification of the reproduction sensitivity required for the magnetoresistive element.

Further, it has been confirmed that antiferromagnetic coupling can be stably obtained by setting the MnPt underlayer thickness to 2 nm or more. However, if the thickness of the MnPt underlayer is excessively large, the shunt loss increases and the output decreases, so the underlayer thickness is desirably 30 nm or less.

Here, only the results when the MnPt alloy is used for the underlayer are shown, but Ru, Rh, Pd,
The same effect can be obtained when a Mn-based alloy film containing at least one element of Ag, Os, Ir, Pt, and Au is used. Any Mn-based alloy film,
Because the electrical resistivity is as large as 100 to 250 μΩ-cm,
It is possible to minimize the output reduction due to the shunt loss of the base film. If it is necessary to further increase the reproduction sensitivity, a multilayer film structure in which a ferromagnetic film / non-magnetic film is stacked a plurality of times may be used instead of the sandwich film structure described above.

The magnetoresistive element of the present invention can convert a weak magnetic signal into an electric signal having a high S / N ratio and output it, and can be used as it is as a position sensor or a direction sensor. Further, the present invention can be applied as a reproducing head mounted on a magnetic recording / reproducing device such as a magnetic disk device or a magnetic tape device.

[0024]

As described above, according to the present invention, a base film is provided between a substrate and a magnetoresistive film having at least two or more ferromagnetic films separated by a nonmagnetic film.
By providing a Mn-based alloy film containing at least one of Ru, Rh, Pd, Ag, Os, Ir, Pt, and Au, ferromagnetic magnetostatic coupling between the ferromagnetic films is suppressed. Therefore, antiferromagnetic coupling acting between the magnetic films can be easily realized.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a configuration of a magnetoresistive element according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing a magnetoresistive effect curve when a base film is made of Ta and Ta / MnPt.

FIG. 3 is a characteristic diagram showing a change in a resistance change rate ΔR / R with respect to a Mn content in a base film MnPt.

[Explanation of symbols]

10: substrate, 11: base film, 12: ferromagnetic film, 13: non-magnetic film, 14: electrode, 15: power supply and signal detecting means.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Yoshihiro Hamakawa 1-280 Higashi Koigakubo, Kokubunji-shi, Tokyo F-term in Central Research Laboratory, Hitachi, Ltd. 5D034 BA04 BA21 CA08

Claims (3)

[Claims] A magnetoresistive film having at least two ferromagnetic films alternately laminated with a ferromagnetic film and a non-magnetic film; and a magnetoresistive film for detecting a resistance change in the magnetoresistive film. In a magnetoresistive element having a pair of electrodes,
Between the substrate and the magnetoresistive film, Ru,
A magnetoresistive element comprising a Mn-based alloy film containing at least one of Rh, Pd, Ag, Os, Ir, Pt, and Au. 2. The magnetoresistance effect element according to claim 1, wherein the Mn content of the Mn-based alloy film is 20 at% to 80 at%.
A magnetoresistance effect element characterized by at%. 3. The magnetoresistance effect element according to claim 1, wherein said Mn-based alloy film has a thickness of 2 nm to 30 nm.