JP2658868B2 - Magnetoresistive element and reproducing method thereof - Google Patents

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 reading a magnetic field intensity as a signal in a magnetic medium or the like, and more particularly to a means for improving a reproduction output in a yoke type artificial lattice magnetoresistive element. .

[0002]

2. Description of the Related Art In recent years, the sensitivity of magnetic sensors has been increased and the density of magnetic recording has been increased. With this, a magnetoresistive magnetic sensor (hereinafter referred to as MR sensor) and a magnetoresistive magnetic head (hereinafter referred to as MR sensor) have been developed. Hereinafter, an MR head is being actively developed. Both the MR sensor and the MR head read an external magnetic field signal due to a change in resistance of a read sensor made of a magnetic material. However, the MR sensor and the MR head do not depend on the reproduction output because the relative speed with the recording medium does not depend on the reproduction output. The MR sensor is characterized by high sensitivity and the MR head is capable of high output even in high-density magnetic recording.

Recently, an artificial lattice magnetoresistive film having a structure in which two or more types of magnetic thin films having different coercive forces adjacent to each other with a nonmagnetic thin film layer interposed therebetween and having a large magnetoresistance change with a small external magnetic field has been developed. Discovered (Japanese Unexamined Patent Publication No. 4-2189)
No. 82, title of invention: magnetoresistance effect element). This magnetoresistance effect element exhibits a large resistance change rate of several% to several tens% with a small external magnetic field of several Oe to several tens Oe.

In the magnetoresistive element of the prior application, as a practical MR head, a shield type artificial lattice magnetoresistive element having a structure in which soft magnetic layers are laminated on both sides of a magnetoresistive film via a nonmagnetic insulator. However, there has been a problem of corrosion because the reproduced waveform becomes extremely asymmetric and the magnetoresistive effect film is exposed on the head flying surface (ABS surface). On the other hand, in the case of a yoke type artificial lattice magnetoresistive element having a structure in which the magnetoresistive film is retracted from the ABS surface and an external magnetic field is guided to the magnetoresistive effect film via the soft magnetic yoke, the symmetry of the reproduced waveform is greatly improved. This has the advantage that the problem of corrosion of the magnetoresistive film is eliminated.

[0005]

However, in the case of a yoke type artificial lattice magneto-resistance effect element, the reproduction output is greatly reduced as compared with the shield type artificial lattice magneto-resistance effect element due to the loss of magnetic flux in the yoke portion. There was a problem.

An object of the present invention is to improve the reproduction output of a yoke type MR head using a magnetoresistive film of the prior application.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a yoke type MR head using the above-mentioned prior-art magnetoresistive film, in which the current flowing through the magnetoresistive film is adjusted so that the reproduction output can be improved. It is to specify. That is, the present invention relates to an artificial lattice magnetoresistive film in which two or more magnetic thin films having different coercive forces are laminated via a non-magnetic layer and the number of repeated laminations is two or more, and a yoke via a non-magnetic insulating layer. In the yoke type magnetoresistive element in which
The coercive force of each of the adjacent magnetic thin films is represented by H _C2 , H _C3 (0
<H _C2 <H _C3 ), the magnetization direction at zero magnetic field after saturating the magnetization in the magnetic thin film whose coercive force is H _C3 is Y.
And flowing a current through the magnetoresistive film in the negative direction of the X-axis defined when the Z-axis is a direction from the magnetoresistive film to the yoke perpendicular to the axis and the film surface of the magnetoresistive film. The present invention relates to a magnetoresistive effect element and a reproducing method thereof.

[0008]

In the magnetoresistive film of the prior application, the magnetization directions of the adjacent magnetic layers are changed from parallel to antiparallel by an external magnetic field due to the difference in coercive force between the adjacent magnetic thin films via the nonmagnetic layer. As a result, a resistance change occurs. That is, the coercive force of each of the adjacent magnetic thin films is represented by H _C2 , H
_{Assuming that C3} (0 <H _C2 <H _C3 ), when the external magnetic field is between the coercive forces H _C2 and H _C3 of the magnetic thin film (H _C2 <H <H _C3 ), the direction of magnetization of the adjacent magnetic thin films is Turn around each other,
The resistance increases. Therefore, in order to function as a magnetoresistive effect element, the magnetization of the magnetic thin film having the coercive force H _C3 is first saturated.

At this time, since the magnetostatic junction between the adjacent magnetic thin films via the non-magnetic thin film occurs at the film edge of the micro-machined artificial lattice magnetoresistive film, the state where the external magnetic field is zero is obtained. However, at the end of the film, the magnetization is in an antiparallel state between the adjacent magnetic layers. Therefore, the magnetization of the magnetic thin film having the coercive force H _C2 has a magnetization distribution that is gradually inverted from the center of the film to the end of the film. On the other hand, since a current magnetic field is generated by the current flowing through the magnetoresistive film, the magnetization of the magnetic thin film having the coercive force H _C2 is greatly affected by the current magnetic field. In the case of a yoke type MR head, since the yoke, which is a soft magnetic material, is disposed only on one side of the magnetoresistive film via the non-magnetic insulating layer, it is generated by a current flowing through the magnetoresistive film. The magnetic field has an asymmetric distribution under the influence of the yoke. At this time, the magnetization distribution of the magnetic thin film having the coercive force H _C2 is
A difference occurs depending on the current direction due to the effect of the asymmetric current magnetic field. That is, the distribution of the magnetization directions of the adjacent magnetic thin films differs depending on the current direction, and a difference occurs in the reproduction output.

Here, the positional relationship between the magnetoresistive film and the yoke, and the relationship between the residual magnetization direction and the current direction of the magnetic thin film having the coercive force H _C3 will be described. For simplicity, the magnetoresistive film is composed of two types of magnetic thin films 2 and 3 having different coercive forces.
Are alternately laminated three times with the non-magnetic thin film 4 interposed therebetween. The coercive forces H _C of the magnetic thin films 2 and 3 are H _C2 and H _C3 (0 <H _C2 <H _C3 ), respectively. At this time, as shown in FIG. 1, the direction is determined when the direction of the residual magnetization of the magnetic thin film 3 is the Y axis, and the direction from the magnetoresistive film to the yoke 5 perpendicular to the film surface of the magnetoresistive film is the Z axis. On the X axis, it is assumed that a current flows in the positive or negative direction on the X axis. That is, it is assumed that the magnetization of the magnetic thin film 3 is oriented in the direction of arrow 7. Here, the fine processing pattern width of the magnetoresistive element corresponds to the MR height shown in FIG. In the state of zero current, the magnetization directions of the magnetic thin film 2 and the magnetic thin film 3 are antiparallel at the end portions of the film, that is, the magnetization of the magnetic thin film 2 goes in the negative direction.
Has a magnetization distribution gradually directed in the negative direction on the Y axis from the film center to the film edge. The following description focuses on the magnetization direction of the central layer (hereinafter referred to as the magnetic thin film 6) of the magnetic thin film 2.

When a current is applied in a positive direction on the X axis,
A current magnetic field generated by a current flowing through the nonmagnetic thin film 4 closer to the yoke 5 side than the magnetic thin film 6 is concentrated near the yoke by the yoke 5 made of a high-permeability magnetic material. However, since the current magnetic field from the magnetic thin film 6 to the non-magnetic thin film 4 in the direction opposite to the yoke 5 is not much affected by the yoke 5, the magnetization is more strongly directed in the negative Y-axis direction near the center of the magnetic thin film 6. Such a magnetic field distribution is obtained. As a result, the change in the magnetization direction of the magnetic thin film 6 with respect to the change in the external magnetic field is
In the vicinity of the center of the magnetoresistive film having the highest magnetic field sensitivity, the resistance is suppressed in the negative direction of the Y axis, and the reproduction output is reduced.

On the other hand, when a current is applied in the negative direction on the X-axis, on the contrary, the magnetization near the center of the magnetoresistive film is distributed so as to weaken the magnetostatic coupling. The change in magnetization of the magnetic thin film 6 with respect to the external magnetic field is not suppressed, and the reproduction output is higher than in the case of flowing in the direction of. Further, since the change in the magnetization of the magnetic thin film 6 is not suppressed, the symmetry of the reproduced waveform is also improved.

The above-described dependence of the reproduction output on the current direction caused by the asymmetry of the current magnetic field due to the presence of the yoke occurs only when the non-magnetic thin film 4 is present on both sides of the magnetic thin film 2 according to the above description. It is necessary that the number of repetitive laminations of the magnetoresistive film is two or more.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings. 2A and 2B are a sectional view and a front view, respectively, of the yoke type head. The ferromagnetic substrate 8 (for example,
NiZn ferrite) has a groove (for example, width: ３０30 μm)
, Depth: ３０30 μm), and this groove is filled with a nonmagnetic insulator 9 (for example, SiO ₂ ). The magnetoresistive film 1 (for example, MR height:
-10 μm) and an electrode 10 (for example, Au:
0.24 μm) and the nonmagnetic insulating layer 11 (for example, Si
O ₂ : .about.0.2 μm) and the yoke 5 (for example, Ni
Fe: １1 μm) is formed so as to overlap (for example, １1 μm) with the magnetoresistive film 1. However, in the (b) front view, the nonmagnetic insulating layer 11 is omitted.
The magnetoresistive film 1 has a structure as shown in FIG. The step of sequentially forming a 5 nm thick Cu thin film, a 1.5 nm thick Co thin film, and a 3.5 nm thick Cu thin film is repeated three times. Note that the last Cu thin film was not formed. The rate of change in magnetoresistance is 9%. The medium is a perpendicular two-layer film medium, and the thickness of the perpendicular medium 12 is 0.1 μm,
The bit length is 1 μm, and the thickness of the medium underlayer 13 is 0.0
It was 5 μm. The spacing between the MR head and the medium is 0.02 μm.

FIG. 3 shows the current direction dependence of the symmetry of the reproduction output and the reproduction waveform with respect to the MR height. From this figure, it can be seen that when the current flows in the negative direction on the X-axis, the reproduction output and the symmetry of the reproduction waveform are greatly improved as compared with the case where the current direction is positive.

The result will be described from the distribution of the internal magnetization of the magnetoresistive film. Here, the results of the magnetization analysis of the yoke type MR head using the magnetoresistive effect element according to the present invention with respect to the change in the signal magnetic field due to the perpendicular two-layer film medium will be described. In the magnetization calculation, current flows only through the Cu thin film 4 (current density: 1 × 10 ⁷ A /
cm ² ), it is assumed that the magnetoresistance effect occurs due to a change in the angle θ between the magnetizations of the magnetic thin films 2 and 3 on both sides of the Cu thin film 4. At this time, the specific resistance ρ of the Cu thin film 4 was calculated by the following equation, where ρ _{0 is} the specific resistance when the magnetic field is zero, and Δρ is the change in the specific resistance.

Ρ = ρ ₀ −0.5 · Δρ · cos θ FIG. 4 shows the current direction dependence of the internal magnetization of the magnetic thin film 6 when the magnetic field from the medium is zero. At this time, the MR height is 3 μm, and the overlap length between the magnetoresistive film 1 and the yoke 5 is 1 μm. Due to magnetostatic coupling with the Co thin film 3 at the end of the NiFe thin film 6, the distribution is such that the magnetization is oriented in the opposite direction to the magnetization of the Co thin film 3.

When a current flows in the positive direction on the X axis, N
Since the current magnetic field due to the current flowing from the iFe thin film 6 to the Cu thin film 4 on the side close to the yoke 5 is concentrated on the yoke, the magnetization distribution of the NiFe thin film 6 in the portion where the magnetoresistive effect film 1 and the yoke 5 overlap. Shift in the positive direction. On the other hand, since the current magnetic field from the NiFe thin film 6 to the Cu thin film 4 in the direction opposite to the yoke 5 is not so affected by the yoke 5, the current magnetic field distribution on both sides of the NiFe thin film 6 becomes asymmetric, and The magnetization distribution is shifted in the negative direction. When the current flows in the negative direction, the same explanation causes undulation in the magnetization distribution in the direction opposite to the positive case. As a result, as shown in FIGS. 5 and 6, when the current is caused to flow in the positive direction, N has the highest magnetic field sensitivity.
In the vicinity of the center of the iFe thin film 6, when the magnetic field from the medium is minimum, the magnetization is saturated and the reproduction output is suppressed (FIG. 5), but when the current flows in the negative direction, the change in the magnetization is sufficiently sensed. It can be seen that it is completed (FIG. 6).

[0019]

As described above, according to the present invention, in the yoke type artificial lattice magnetoresistance effect element, the direction of the current flowing through the artificial lattice magnetoresistance effect film is defined.
The reproduction output can be improved.

Further, the symmetry of the reproduced waveform can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a magnetoresistive element for explaining the operation principle of the present invention.

FIGS. 2A and 2B are a cross-sectional view and a front view, respectively, of a yoke-type magnetoresistive head according to an embodiment.

FIG. 3 is a diagram showing the current direction dependence of the symmetry of the reproduction output and the reproduction waveform in the example.

FIG. 4 is a diagram showing the current direction dependence of the internal magnetization of the NiFe thin film 6 in the example.

FIG. 5 is a diagram showing the dependence of the internal magnetization of the NiFe thin film 6 on the medium magnetic field (in the case where the current direction is positive) in the example.

FIG. 6 is a diagram showing the dependence of the internal magnetization of the NiFe thin film 6 on the medium magnetic field (in the case where the current direction is negative) in the example.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 magnetoresistive film 2 magnetic thin film 3 magnetic thin film 4 nonmagnetic thin film 5 yoke 6 thin film at center of magnetic thin film 2 7 magnetization direction of magnetic thin film 3 8 ferromagnetic material 9 nonmagnetic insulator 10 electrode 11 nonmagnetic insulating layer 12 vertical Medium 13 Medium underlayer

Claims (2)

(57) [Claims] An artificial lattice magnetoresistive film having two or more magnetic thin films having different coercive forces laminated through a nonmagnetic layer and having a repeated number of laminations of two or more is provided with a yoke via a nonmagnetic insulating layer. , The coercive force of each of the adjacent magnetic thin films is H _C2 , H _C3.
When (0 <H _C2 <H _C3 ), the magnetization direction at zero magnetic field after saturating the magnetization in the magnetic thin film having a coercive force of H _C3 is perpendicular to the Y axis, and perpendicular to the film surface of the magnetoresistive film. A current flowing through the magnetoresistive film in a negative direction of the X axis defined when the direction from the magnetoresistive film toward the yoke is the Z axis. 2. An artificial lattice magnetoresistive film having two or more magnetic thin films having different coercive forces laminated via a non-magnetic layer and having a repetitive lamination number of 2 or more. Wherein the coercive force of each of the adjacent magnetic thin films is set to H.
_{When C2} and H _C3 (0 <H _C2 <H _C3 ), the coercive force is H _C3
The magnetization direction at zero magnetic field after the magnetization of the magnetic thin film is saturated is defined as the Y axis, and the direction from the magnetoresistive film to the yoke perpendicular to the film surface of the magnetoresistive film is defined as the Z axis. A current is passed through the magnetoresistive film in the negative direction of the X-axis to detect an external magnetic field.