JPH05258244A - Magnetoresistance effect head - Google Patents

Abstract

PURPOSE:To enhance utilization efficiency of a sense current concerned in a bias of a magnetoresistance effect element and to permit power consumption saving, in a magnetoresistance effect head used in a magnetic disk device, etc. CONSTITUTION:The film quality of a soft magnetic body layer for the bias of the magnetoresistance element 10 is changed gradually or continuously in the thickness direction such that a saturation magnetic flux density at the far side from the magnetoresistance effect element 10 is smaller than it at the near side. For example, the soft magnetic body layer 31 is constituted of having a multiple structure consisting of layers 31A, 31B being mutually different from the saturation magnetic flux density.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetoresistive effect head used in a magnetic disk device or the like, and is characterized by the structure of a soft magnetic layer for biasing.

In a magnetic disk device, the diameter of a magnetic disk, which is a recording medium, is being reduced. Along with this, attention has been paid to a magnetoresistive head capable of obtaining a large reproduction output even when the relative moving speed with respect to the magnetic disk is small.

[0003]

2. Description of the Related Art FIG. 4 shows a basic magnetoresistive head 10.
It is a perspective view which shows the schematic structure of 0. The magnetoresistive effect head 100 has a magnetization direction Mm in which the resistance value of the MR element (magnetoresistive effect element) 10 changes according to the magnetic field of the recording medium 60 and a direction Mi of the sense current Is flowing in the MR element 10. It is a magnetic head that utilizes the dependence on the relative angle θ, and is manufactured using thin film technology.

The MR element 10 is composed of a ferromagnetic layer having a thickness of about several hundred liters, and the lead conductor 50 for passing the sense current Is is composed of a thin film of gold (Au) or the like. The size of the MR element 10 is appropriately selected according to the recording density.
For example, the length in the recording track width w direction is about 100 μm including the connecting portion of the lead conductor 50, and the length (height) in the direction orthogonal to the medium surface is about 2 to 5 μm. That is, the actual shape of the MR element 10 is an extremely thin strip shape.

Magnetic shield layers 40 are arranged on both sides of the MR element 10 in the thickness direction with a predetermined gap, whereby the S / N ratio of the reproduced signal is increased and high density recording is possible. Become.

In the MR element 10, since the input / output characteristic (relationship between the magnetic field direction and its detection signal) is a square characteristic, when it is used, it should be operated in the linear response range. A so-called bias having the above-mentioned relative angle θ as a predetermined value is applied in advance.

Although various methods are known for biasing, in the magnetoresistive head 100 illustrated here, as a bias means, a soft magnetic material layer is formed so as to overlap with the MR element 10 via a nonmagnetic material layer 20. 30 are provided.

That is, in the magnetoresistive head 100, the magnetic field generated by the sense current Is flowing through the MR element 10 causes the directions of magnetization in the soft magnetic layer 30 to be aligned in a fixed direction, and the magnetic field (bias magnetic field) generated thereby causes MR. The element 10 is biased.

Conventionally, as the soft magnetic material layer 30 for bias (hereinafter referred to as "bias magnetic layer") 30, a uniform magnetic layer made of a single soft magnetic material (high magnetic permeability material) is provided. The material and the three-dimensional shape are selected so that an appropriate bias magnetic field is generated by a sense current Is of about 10 to 20 mA and an optimum bias state is obtained.

In some cases, one of the two magnetic shield layers 40 sandwiching the MR element 10 may be arranged closer to the MR element 10 than the other, and this may be used as a bias magnetic layer.

[0011]

Microscopically, when the bias magnetic field is generated, the magnetic field (that is, the magnetizing force applied to the bias magnetic layer 30) due to the sense current Is has a distance of two.
Since it weakens in proportion to the power of the MR element 10, it is weakened in the thickness direction (that is, the stacking direction) of the bias magnetic layer 30.
The farther away the magnetic force becomes weaker. That is, MR
The side closer to the element 10 is in a state where the magnetization rotation is relatively likely to occur, while the far side is in a state where the magnetization rotation is relatively less likely to occur.

Here, the rotation of the magnetization is a physical phenomenon in which the magnetization (magnetic moment) of each magnetic domain whose direction is irregular in the magnetization process of the magnetic body changes its direction to the direction of the magnetizing force. The stronger the magnetizing force, the greater the degree of rotation (rotation angle), and the bias magnetic field becomes stronger accordingly. Further, if the strength of the magnetizing force is equal to or higher than a predetermined value, almost all the magnetization directions are aligned with the direction of the magnetizing force, and the magnetic material is entirely in a magnetically saturated state.

On the other hand, in a homogeneous magnetic layer such as the conventional bias magnetic layer 30, the rotation of the magnetization of each magnetic domain is equalized due to the action of stabilizing the magnetic energy state of the layer. .. That is, the rotation of the magnetization of the entire layer is an average of the easiness of rotation of the magnetization in each part, and as a result, the rotation of the magnetization of the entire layer is suppressed by the influence of the portion where the rotation of the magnetization is hard to occur. Become.

Therefore, the conventional magnetoresistive head is
In order to generate a predetermined bias magnetic field, the MR element 10
There is a problem in that it is disadvantageous in terms of power consumption because it is necessary to flow an extra sense current Is by the amount that the rotation of the magnetization of the entire bias magnetic layer 30 can be suppressed on the side far from the.

In view of the above problems, it is an object of the present invention to improve the utilization efficiency of the sense current related to the bias of the magnetoresistive effect element and save power.

[0016]

In order to solve the above-mentioned problems, the head according to the invention of claim 1 is, as shown in FIG. 1 and FIG. In the magnetoresistive effect heads 1 and 2 having a laminated structure in which the body layers 31 and 32 overlap each other with the non-magnetic body layer 20 interposed therebetween, the soft magnetic body layer 31 is far from the magnetoresistive effect element 10. A plurality of layers having a smaller saturation magnetic flux density than the side closer to the side, that is, the layers 31A and 32A, and the layer 31.
It consists of B and 32B.

As shown in FIG. 3, the head according to the second aspect of the present invention has a laminated structure in which the magnetoresistive effect element 10 and the soft magnetic layer 33 for biasing the magnetoresistive element 10 overlap with each other via the nonmagnetic layer 20. In the magnetoresistive effect head 3 having the composition, the composition is continuously changed in the stacking direction such that the soft magnetic layer 33 has a saturation magnetic flux density smaller as the soft magnetic layer 33 is farther from the magnetoresistive element 10. Consists of layers.

[0018]

The soft magnetic layers 31, 32 and the soft magnetic layer 33
Is a layer in which the saturation magnetic flux density related to the magnetic characteristics is changed stepwise or continuously from the side closer to the magnetoresistive element 10 to the side farther in the layer stacking direction.

For example, the easiness of rotation of the magnetization in each part of the soft magnetic layer 31 depends on the strength of the applied magnetic field, and depends on the magnitude of the saturation magnetic flux density Bs which is the physical property constant of the part. Also depends.

That is, as shown in FIG. 1, a magnetic field H generated by the sense current Is flowing through the magnetoresistive effect element 10.
When 1 is added and the magnetization starts to rotate in the soft magnetic material layer 31, magnetic charges (so-called N pole and S pole) appear on both end surfaces of the soft magnetic material layer 31, whereby the sense current I is generated inside the layer.
A demagnetizing field (also referred to as a demagnetizing field) RH in the direction opposite to the magnetic field H1 due to s is generated.

Therefore, the magnetic field H1 generated by the sense current Is
However, since the strength of the demagnetizing field RH is proportional to the square of the saturation magnetic flux density Bs at this time, the saturation magnetic flux density B
Area where s is small (area far from the magnetoresistive effect element 10)
Then, the degree to which the magnetic field H1 is weakened is smaller than that in the portion where the saturation magnetic flux density Bs is large (the portion near the magnetoresistive effect element 10).

By the way, the magnetic field H1 generated by the sense current Is
Is stronger as it is closer to the magnetoresistive effect element 10. Therefore, in the soft magnetic layer 31, the demagnetizing field RH is strong in the portion where the magnetic field H1 is strong due to the sense current Is, and the demagnetizing field RH is weak in the portion where the magnetic field H1 is weak due to the sense current Is, so that the magnetization rotation occurs in the stacking direction. The strength of the magnetic field that effectively acts on the magnetic field (effective magnetic field) is equalized, and the susceptibility to rotation of magnetization is uniform over the entire layer.

As a result, compared to the case where there is a difference in the susceptibility of the rotation of the magnetization, the magnetic loss is small and the predetermined bias magnetic field can be generated with a smaller sense current Is.

[0024]

1 to 3 are perspective views schematically showing the construction of essential parts of magnetoresistive heads 1, 2 and 3 according to first to third embodiments of the present invention. In these figures,
Components having the same functions as those in FIG. 4 are designated by the same reference numerals, and the description thereof will be omitted or simplified.

In FIG. 1, a magnetoresistive head 1 has an MR element 1 made of a permalloy (Ni-Fe) layer.
0, for example, a nonmagnetic layer 20 made of titanium (Ti), and a soft magnetic layer 31 for biasing are sequentially stacked. The thickness d1 of the MR element 10 is 400Å, and the thickness d2 of the nonmagnetic layer 20 is 300Å.

The soft magnetic layer 31 of this embodiment is composed of two layers 31A and 31B made of the same kind of magnetic material having different composition ratios.
(These thicknesses are both 200Å). The layer 31A on the side close to the MR element 10 is made of chromium (C
It is made of a Ni-Fe-Cr magnetic alloy in which the amount of r) added is 5%, and its saturation magnetic flux density (Bs) is 7200 gauss. Further, the layer 31B on the side far from the MR element 10 is made of a Ni—Fe—Cr magnetic alloy in which the amount of chromium added is 10%, and its saturation magnetic flux density is 4800 gauss.

The layers 31A and 31B can be formed by the RF sputtering method using argon gas as the sputtering gas, for example. At that time, the sputtering gas pressure is set to about 5 [mTorr], and the high frequency power (sputtering power) is set to about 600 watts.

In the magnetoresistive head 1 configured as described above, the sense current Is is set as described in the section of the operation.
Due to the relationship between the magnetic field H1 and the demagnetizing field RH (the strength of each magnetic field is indicated by the length of the arrow in the figure), the magnetization force in the thickness direction is equalized, and the rotation of the magnetization occurs in the entire soft magnetic layer 31. It is easy and magnetic loss due to the generation of the bias magnetic field H2 is relatively small.

In order to confirm this, the so-called ρ-H characteristic of the magnetoresistive effect head 1 of the present embodiment and the conventional magnetoresistive effect head having a homogeneous soft magnetic layer were measured and the rotation of magnetization was confirmed. The value of the sense current Is required for saturation and the amount of magnetic charge (magnetization strength) appearing on both end faces of the soft magnetic layer in the saturated state were calculated and compared.

As a result, in the magnetoresistive head 1, the above-mentioned ratio (magnetic charge amount / current value) is 20% as compared with the conventional one.
It was a large value. This indicates that in the magnetoresistive effect head 1, the magnetization of the soft magnetic layer 31 is likely to rotate, and the utilization efficiency of the sense current Is is high.

As the material of the soft magnetic layer 31, zirconium (Zr) or niobium (Nb) is used instead of chromium.
Added Ni-Fe alloy (Ni-Fe-Zr, Ni-
Fe-Nb) and Co with molybdenum (Mo) added
Similar results were obtained when the saturation magnetic flux density was adjusted by the amount of the additive using -Zr alloy (Co-Zr-Mo).

In the magnetoresistive head 2 shown in FIG. 2, a soft magnetic layer 32 for biasing the MR element 10 is provided.
Is composed of two layers 32A and 32B made of different materials.

That is, the layer 32 on the side closer to the MR element 10.
A is made of iron nitride (FeN), and its thickness d4A is 1
It is set as 00Å. Further, the layer 32B on the side far from the MR element 10 is made of Ni-Fe in which the amount of chromium added is 10%.
It is made of a -Cr magnetic alloy and has a thickness d4B of 200Å. The saturation magnetic flux density of the layer 32B is smaller than that of the layer 32A.

Each of these layers 32A and 32B can also be formed by using the RF sputtering method under the same sputtering conditions as in the above example. However, when forming the layer 31A, iron as a target is sputtered in a nitrogen atmosphere of 0.2 [mTorr].

As a result of evaluation and measurement of the magnetoresistive head 2 having the above-mentioned structure, a value larger than the conventional one by about 25% was obtained as the above-mentioned ratio (magnetic charge amount / current value).

The material of the layer 32B is Ni-Fe-.
When Co-Zr-Mo is used instead of Cr, the layer 32A
As a material for Fe, instead of FeN, Fe-Si, Fe-Si-
Similar results were obtained when using Al and materials containing B, N, and C added thereto.

In the magnetoresistive head 3 shown in FIG. 3, the soft magnetic layer 33 for biasing the MR element 10 is used.
As a result, a Ni—Fe—Cr layer in which the amount of chromium added is continuously changed in the thickness direction is provided so that the saturation magnetic flux density becomes smaller as the distance from the MR element 10 increases. The thickness d5 of the soft magnetic layer 33 is 500Å.

Such a soft magnetic layer 33 can be formed by simultaneously sputtering two targets (permalloy and chromium) and changing the high frequency power (sputtering power) for each target.
At that time, for example, the amount of chromium added is 5% on the side closer to the MR element 10 and 10% on the side farther from the MR element 10, so that the high frequency power is continuously changed during film formation. Let

As a result of evaluation and measurement of the magnetoresistive head 3 having the above-mentioned structure, a value 20% larger than the conventional one was obtained as the above-mentioned ratio (magnetic charge amount / current value).

As the material of the soft magnetic layer 33, C
Permalloy with Zr and Nb added in place of r, and Mo
Similar results were obtained when Co-Zr added with was used.

In the above embodiment, the soft magnetic layer 3
The materials 1, 32 and 33 can be selected appropriately.
However, as the saturation magnetic flux density is smaller, it is necessary to increase the thickness of the layer in order to obtain a predetermined bias magnetic field. Therefore, the resistance value of the layer is reduced and the sense current Is spills around, resulting in a disadvantage in power saving. Therefore, it is preferable to use a material having a higher saturation magnetic flux density.

Although the soft magnetic layers 31 and 32 having a two-layer structure are illustrated in the embodiments of FIGS. 1 and 2, the soft magnetic layers 31 and 32 may have a multi-layer structure of three or more layers.

[0043]

According to the present invention, the utilization efficiency of the sense current related to the bias of the magnetoresistive effect element can be improved, and the power consumption can be saved.

[Brief description of drawings]

FIG. 1 is a perspective view schematically showing a configuration of a main part of a magnetoresistive effect head according to a first embodiment of the invention.

FIG. 2 is a perspective view schematically showing a configuration of a main part of a magnetoresistive effect head according to a second embodiment of the invention.

FIG. 3 is a perspective view schematically showing a configuration of a main part of a magnetoresistive effect head according to a third embodiment of the invention.

FIG. 4 is a perspective view showing a schematic configuration of a basic magnetoresistive effect head.

[Explanation of symbols]

 1, 2 and 3 magnetoresistive effect head 10 MR element (magnetoresistive effect element) 20 non-magnetic layer 31, 32, 33 soft magnetic layer 31A, 32A layer (layer with high saturation magnetic flux density) 31B, 32B layer (saturated) Layer with low magnetic flux density)

Claims (2)

[Claims] 1. A magnetoresistive head having a laminated structure in which a magnetoresistive effect element (10) and a soft magnetic material layer (31, 32) for biasing the magnetoresistive effect element overlap each other with a nonmagnetic material layer (20) interposed therebetween. 1, 2), wherein the soft magnetic layer (31) has a plurality of layers (31A, 32A) (31A, 32A) having a smaller saturation magnetic flux density than the side closer to the magnetoresistive effect element (10) farther away. 31B, 32
A magnetoresistive effect head comprising B). 2. A non-magnetic layer (20) comprising a magnetoresistive effect element (10) and a soft magnetic layer (33) for biasing the magnetoresistive element.
A magnetoresistive effect head (3) having a laminated structure in which the saturation magnetic flux density is smaller as the soft magnetic layer (33) is farther from the magnetoresistive element (10). In addition, a magnetoresistive effect head comprising a layer whose composition is continuously changed in the stacking direction.