JPH09245322A - Magnetic sensor and magnetic head - Google Patents

Abstract

(57) [Abstract] [Problem] Even if the size is reduced for higher resolution,
Prevents sensitivity deterioration. SOLUTION: A variable magnetic film 1 whose magnetization direction changes according to a change in the magnetization direction of an applied magnetic field, a non-magnetic film 2, and a fixed magnetic film 3 are laminated so as to exhibit a giant magnetoresistive effect. The fixed magnetic film 3 includes a first magnetic film 4 facing the non-magnetic film 2 and a second magnetic film 6 facing the first magnetic film 4.
They are antiferromagnetically coupled to each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spin valve type magnetic sensor and a magnetic head having a giant magnetoresistive effect for detecting a change in applied magnetic field strength by converting it into a large change in resistance value.

[0002]

2. Description of the Related Art In recent years, as a magnetic sensor, a spin-valve type four-layer film structure having a giant magnetoresistive effect showing a larger magnetoresistive change rate than a normal magnetoresistive effect is known (Japanese Patent Laid-Open No. Hei 4). -See 358310).

Such a magnetic sensor is formed in a substantially rectangular plate shape as shown in FIGS. 11 and 12, for example, a metal magnetic thin film 11, a non-magnetic thin film 12, a metal magnetic thin film 13,
The antiferromagnetic thin film 14 and the pair of electrodes 15 are laminated in the above order.

The metal magnetic thin film 13 is in direct contact with the antiferromagnetic thin film 14, and the direction of magnetization of the metal magnetic thin film 13 is magnetic due to exchange interaction which is a magnetic coupling between the both films 13 and 14. It is fixed by the antiferromagnetic thin film 14 so as to be perpendicular to the longitudinal direction of the sensor. On the other hand, the magnetic direction of the metal magnetic thin film 11 separated by the non-magnetic thin film 12 changes according to the change of the magnetic field direction of the signal magnetic field H ₁ as the applied magnetic field.

That is, the metal magnetic thin film 13 has a signal magnetic field H.
It has a larger coercive force than that of _1, and is set so that the once set magnetization direction is maintained with respect to the change of the signal magnetic field H ₁ , while the metal magnetic thin film 11 is smaller than the signal magnetic field H _1. It has a coercive force and is set so that the magnetization direction of the metal magnetic thin film 11 changes according to the change of the signal magnetic field H ₁ .

The direction of the magnetization M ₅ of the metal magnetic thin film 11 is in the longitudinal direction of the magnetic sensor due to the magnetic anisotropy of the metal magnetic thin film 11 when the signal magnetic field H ₁ applied to the magnetic sensor is zero. It is set to be parallel, in other words, orthogonal to the direction of the magnetization M ₆ of the metal magnetic thin film 13.

In such a magnetic sensor, the signal magnetic field H ₁
Changes the direction of the magnetization of the metal magnetic thin film 11, and changes in the magnetic resistance corresponding to the magnetization M ₅ of the metal magnetic thin film 11 and the relative angle between the metal magnetic thin film 13 and the magnetization M ₆ are detected. To be done.

In order to sufficiently bring out the performance of the magnetic sensor of this structure, when the signal magnetic field H ₁ is zero, the magnetization directions of both metal magnetic thin films 11 and 13 are actually orthogonal to each other as set above. It is necessary to be.

This is based on the following reasons. When the magnetization directions of the metal magnetic thin film 11 and the metal magnetic thin film 13 are opposite to each other by 180 degrees, that is, they are antiparallel to each other, the electric resistance value of the magnetic sensor becomes maximum. This is because, among the metal magnetic thin film 11 and the metal magnetic thin film 13, electrons that move from one film to the other film are non-parallel to each other due to the antiparallel state. This is because they are scattered at each interface of.

On the other hand, the metal magnetic thin film 11 and the metal magnetic thin film 1
When the magnetization directions with respect to 3 are the same, that is, parallel to each other, the scattering of moving electrons at each interface of the non-magnetic thin film 12 / the magnetic thin films 11 and 13 is reduced most, so that the electric resistance of the magnetic sensor is reduced. It is the smallest.

A graph showing the change in the electric resistance with respect to the change in the magnetization direction of the metal magnetic thin film 11 is as follows.
The above graph has a substantially S-shape, and the above change rate is the largest, that is, the slope showing the change in the change rate in the above graph is the largest because the relative angle between the metal magnetic thin film 11 and the metal magnetic thin film 13 is large. This is when it is set to 90 degrees, that is, orthogonal.

Therefore, in the spin-valve four-layer structure, when the signal magnetic field is zero, the relative angle between the metal magnetic thin film 11 and the metal magnetic thin film 13 is 90 degrees, that is, they are orthogonal to each other. The magnetization directions of the metal magnetic thin film 11 and the metal magnetic thin film 13 are set respectively.

[0013]

However, in the above-described conventional magnetic sensor using the spin-valve type multilayer film, there are the following two points regarding the change in the magnetization of the metal magnetic thin film 11 when the signal magnetic field is zero: There is a problem that the sensitivity is lowered and the degree of freedom in design is lowered.

First, the first problem that leads to a decrease in sensitivity is
In response to the demand for higher resolution of the magnetic sensor, the element width W of the magnetic sensor tends to be narrowed, and one having a width of 1 μm or less has been produced. With such a narrowing of the width W, the demagnetizing field of the metal magnetic thin film 13 fixed by the antiferromagnetic thin film 14 increases and may reach several hundred Oersted depending on the film thickness of the antiferromagnetic thin film 14. There is.

In this case, since the demagnetizing field becomes larger than the magnetic coupling between the antiferromagnetic thin film 14 and the metal magnetic thin film 13, the magnetization M ₆ of the metal magnetic thin film 13 when the signal magnetic field is zero. The direction of is parallel to the longitudinal direction of the magnetic sensor, and thus is parallel to the magnetization direction of the metal magnetic thin film 11, so that the sensitivity of the magnetic sensor is extremely lowered.

Even if the entire magnetization direction of the metal magnetic thin film 13 is not parallel to the magnetization direction of the metal magnetic thin film 11, as shown in FIG. 13, the width direction end 13a of the magnetic sensor in which the demagnetizing field appears strongly. In the above, even if the signal magnetic field is zero, the phenomenon that the magnetization direction of the metal magnetic thin film 13 changes along the direction M ₈ parallel to the longitudinal direction of the magnetic sensor occurs.

When such a magnetic sensor is used for a magnetic head, the above-mentioned phenomenon occurs because the widthwise end portion of the magnetic sensor has the highest sensitivity to changes in the signal magnetic field, which is the signal magnetic field. It significantly deteriorates the sensitivity of the magnetic head. Conventionally, in order to deal with such deterioration, it is necessary to fix the magnetization direction of the metal magnetic thin film 13, that is, to set a high energy for pinning, but it is difficult to realize with an actual magnetic material.

The second problem of reduction in the degree of design freedom is that the direction of the magnetization M ₆ of the metal magnetic thin film 13 is set in the width direction of the magnetic sensor as shown in FIGS. A bias magnetic field is applied by the metal magnetic thin film 13 to the metal magnetic thin film 11 whose direction changes freely.

Therefore, the center of change in the magnetization direction of the metal magnetic thin film 11 is displaced from the position orthogonal to the magnetization direction of the metal magnetic thin film 13, and the magnetization direction of the metal magnetic thin film 11 is zero when the signal magnetic field is zero. And the magnetic metal thin film 13
Due to the above-mentioned reason that the magnetization directions of are orthogonal to each other,
This causes a problem that sensitivity of the magnetic sensor is lowered.

Therefore, conventionally, in order to avoid the above-mentioned problem, a means for canceling the bias magnetic field with the current magnetic field generated by the sense current supplied to the magnetic sensor has been considered.

However, when the above-mentioned means is used, the sense current value is set to a predetermined fixed value or the size of the metal magnetic thin film 13 is set to a predetermined value in order to generate a predetermined current magnetic field. There is a great constraint on the degree of freedom in designing the magnetic sensor.

An object of the present invention is to solve the problems of the conventional spin valve type magnetoresistive sensor, and to provide a magnetic sensor having high sensitivity and a high degree of design freedom, and a magnetic head using the same.

[0023]

In order to solve the above problems, a magnetic sensor according to claim 1 of the present invention includes a variable magnetic film whose magnetization direction changes in accordance with a change in the magnetic field direction of an applied magnetic field. In a magnetic sensor in which a non-magnetic film and a fixed magnetization film are laminated on each other so as to exhibit a giant magnetoresistive effect,
The pinned magnetic film is characterized by having a first magnetic film facing the non-magnetic film and a second magnetic film, which are antiferromagnetically coupled to each other.

According to the above-mentioned structure, the magnetization direction of the variable magnetic film which changes according to the change of the magnetic field direction of the applied magnetic field and the magnetization direction fixed with respect to the change of the applied magnetic field. The electric resistance of the variable magnetic film, the non-magnetic film, and the fixed magnetic film as a whole is changed by the giant magnetoresistive effect according to the change in the relative angle between the fixed magnetic film holding the magnetic field and the magnetization direction of the first magnetic film. It is possible to detect the change in the applied magnetic field by making a large change and more reliably by the change in the electric resistance.

In addition, in the above-mentioned structure, since the first magnetic film and the second magnetic film are antiferromagnetically coupled in the fixed magnetization film,
The magnetic field generated by the first magnetic film and the magnetic field generated by the second magnetic film can be canceled out from each other, and the value of the synthetic saturation magnetization, which is the overall saturation magnetization of the fixed magnetization film, is smaller than the value of the saturation magnetization of the first magnetic film. it can.

From the above, in the above structure, since the strength of the demagnetizing field of the fixed magnetic film is proportional to the value of the synthetic saturation magnetization of the fixed magnetic film, the value of the demagnetizing field of the fixed magnetic film can be greatly reduced. . Thus, in the above-described configuration, destabilization of the magnetization direction in the first magnetic film due to the demagnetizing field can be suppressed, so that the setting of the magnetization direction of the variable magnetic film and the magnetization direction of the first magnetic film is optimal. Therefore, it is possible to avoid a decrease in sensitivity for detecting a change in the applied magnetic field due to the above setting deviating from the optimum value.

Further, in the above structure, since the value of the synthetic saturation magnetization in the fixed magnetic film can be reduced, the bias magnetic field applied from the fixed magnetic film to the variable magnetic film can also be greatly reduced. It is possible to suppress the deviation of the magnetization direction that occurs in the variable magnetization film.

Therefore, in the above configuration, the setting with the magnetization direction of the first magnetic film can be maintained in the optimum state, and the sensitivity decrease for detecting the change of the applied magnetic field due to the deviation from the optimum value can be avoided. it can.

Moreover, in the above-mentioned structure, the sense current value is set to a predetermined fixed value by using the means for canceling the bias magnetic field with the current magnetic field generated by the sense current applied to the magnetic sensor as in the conventional case. Since the generation of the bias magnetic field can be significantly reduced as compared with the case where there is a large constraint on the degree of freedom in the design of the magnetic sensor, which is necessary, it is possible to reduce the constraint on the degree of freedom.

A magnetic sensor according to a second aspect of the present invention is the magnetic sensor according to the first aspect, wherein the pinning film made of a magnetic material has a magnetization direction of the pinned magnetization film based on the magnetization direction of the pinning film. It is characterized in that it is laminated on the fixed magnetic film so as to be fixed.

According to the second aspect of the invention, since the magnetization direction of the fixed magnetization film is fixed more stably by the fixing film with respect to the change of the applied magnetic field, the magnetization of the fixed magnetization film is increased. It is possible to suppress a decrease in detection sensitivity for detecting a change in applied magnetic field due to a change in direction.

A magnetic sensor according to a third aspect of the present invention is the magnetic sensor according to the first or second aspect, wherein the coupling film made of a metal non-magnetic material is provided between the first magnetic film and the second magnetic film. It is characterized in that it is provided so as to be laminated between the first magnetic film and the second magnetic film so as to increase antiferromagnetic coupling.

According to the third aspect of the invention, even if the strength of the magnetization of the second magnetic film is set low by the coupling film, the strength of the magnetization of the first magnetic film that can be set by the second magnetic film. Can be improved.

Therefore, in the above structure, the film thickness of the first magnetic film and the second magnetic film can be made thin, or the selection range of the magnetic material of the first magnetic film and the second magnetic film can be widened. Therefore, the first magnetic film and the second magnetic film
The film thickness of the magnetic film can be made thin, or an inexpensive material can be used as the magnetic material of the first magnetic film and the second magnetic film, so that the cost can be reduced.

A magnetic sensor according to a fourth aspect of the present invention is the magnetic sensor according to the third aspect, wherein the coupling film is within a range in which the first magnetic film and the second magnetic film are antiferromagnetically coupled. The feature is that it is set to be thin.

According to the configuration of the above-mentioned claim 4, since the bonding film can be set thin, it is possible to suppress the time and material for forming the bonding film, and to reduce the cost when manufacturing the structure. be able to.

A magnetic sensor according to claim 5 of the present invention is the magnetic sensor according to claim 1, 2, 3 or 4, wherein
In the fixed magnetic film, the value of the synthetic saturation magnetization in the fixed magnetic film is reduced by the saturation magnetization of the first magnetic film and the second magnetic film and the film thickness of the first magnetic film and the second magnetic film. It is characterized by being.

According to a sixth aspect of the present invention, in the magnetic sensor according to the second, third or fourth aspect, the value of the synthetic saturation magnetization in the fixing film and the fixed magnetic film is reduced. Each saturation magnetization of the pinning film, the first magnetic film and the second magnetic film, and the pinning film, the first magnetic film and the second magnetic film
It is characterized in that each film thickness of the magnetic film is set.

A magnetic sensor according to a seventh aspect of the present invention is the magnetic sensor according to the fifth or sixth aspect, wherein the apparent saturation magnetization of the fixed magnetization film is set to be substantially zero. It is characterized by that.

According to the fifth, sixth, and seventh aspects of the invention, the intensity of the demagnetizing field of the fixed magnetic film becomes equal to the value of the synthetic saturated magnetization due to the reduction of the value of the synthetic saturated magnetization in the fixed magnetic film. Since they are proportional to each other, the value of the demagnetizing field due to the fixed magnetic film can be significantly reduced.

As a result, in the above structure, it is possible to suppress the destabilization of the magnetization direction in the first magnetized film due to the demagnetizing field, so that the magnetization direction of the variable magnetized film and the magnetization direction of the first magnetized film are set. The optimum state can be maintained, and it is possible to avoid a decrease in sensitivity for detecting a change in the applied magnetic field due to the above setting deviating from the optimum value.

Further, in the above structure, since the value of the synthetic saturation magnetization in the fixed magnetic film can be reduced, the bias magnetic field applied from the fixed magnetic film to the variable magnetic film can also be greatly reduced, which is caused by the bias magnetic field. It is possible to suppress the deviation of the magnetization direction that occurs in the variable magnetization film.

Therefore, in the above structure, the setting of the magnetization direction of the first magnetic film can be maintained in an optimum state by suppressing the bias, and a change in the applied magnetic field due to the setting being deviated from the optimum value. It is possible to avoid a decrease in detection sensitivity.

Moreover, in the above-mentioned configuration, the sense current value is set to a predetermined fixed value by using the means for canceling the bias magnetic field with the current magnetic field generated by the sense current applied to the magnetic sensor as in the conventional case. Since the generation of the bias magnetic field can be significantly reduced as compared with the case where there is a large constraint on the degree of freedom in the design of the magnetic sensor, which is necessary, it is possible to reduce the constraint on the degree of freedom.

A magnetic head according to claim 8 of the present invention is a magnetic sensor according to any one of claims 1 to 7, a power supply for energizing the magnetic sensor, and a recording medium on which information is recorded by a change in the magnetization direction. A detecting means for detecting a change in the electric resistance of the magnetic sensor due to a change in the magnetic field applied to the magnetic sensor based on a change in the magnetization direction due to the relative movement with respect to the magnetic sensor when the power source is energized. It is characterized by having.

According to the above structure, the magnitude of the change in the electric resistance in the magnetic sensor due to the change in the applied magnetic field due to the relative movement of the recording medium with respect to the magnetic sensor is as described above. In addition, since it can be made larger than in the conventional case, the region of magnetization in the recording medium that can be detected by the detecting means can be set smaller.

[0047]

FIG. 1 shows an embodiment of the present invention.
The following is a description based on FIG.
The magnetic sensor of the present invention, as shown in FIG. 1 and FIG.
It has a giant magnetoresistive effect that shows a large change in electric resistance with respect to a change in the magnetic field direction of the signal magnetic field H ₁ as an applied magnetic field, and has a variable magnetization on a substantially rectangular plate-shaped substrate (not shown). A film 1, a non-magnetic film 2 made of a metal non-magnetic thin film, a fixed magnetization film 3, a magnetization fixing film (fixing film) 7 made of a hard magnetic material, and a sense current for detecting a change in the electric resistance are provided. The electrode conductor thin film 8 for energizing is sequentially
It has a spin-valve type multilayer thin film formed by patterning.

The giant magnetoresistive effect means that the electric resistance between the variable magnetic film 1 and the fixed magnetic film 3 with the nonmagnetic film 2 sandwiched therebetween changes the magnetization direction according to the change of the signal magnetic field H _1. The variable magnetic film 1 and the fixed magnetic film 3 whose magnetization direction is fixed with respect to the change of the signal magnetic field change in proportion to the cosine of the relative angle between the directions of the respective magnetizations, and the conventional abnormality. compared with the magneto-resistance effect, reaching change in electrical resistance value with respect to the change of the signal magnetic field H ₁ is several times, in which detection sensitivity of the change of the signal magnetic field H ₁ is improved. Moreover, the giant magnetoresistive effect is independent of the direction of current applied to detect the electrical resistance value.

The variable magnetic film 1 is made of a soft magnetic material having a high magnetic permeability so that the magnetization direction can be easily changed according to the change of the signal magnetic field H ₁ . The non-magnetic film 2 suppresses or prevents strong coupling between the variable magnetic film 1 and the fixed magnetic film 3 via the non-magnetic film 2 antiferromagnetically and also magnetically strongly. Is set to. Thereby, the change of the magnetization direction of the fixed magnetization film 3 with respect to the change of the magnetization direction of the variable magnetization film 1 is avoided, and the magnetization direction of the fixed magnetization film 3 is maintained with respect to the change of the signal magnetic field H ₁ .

The fixed magnetization film 3 is the non-magnetic film 2
A first magnetic film 4 which is a metal magnetic thin film facing the front surface, a coupling film 5 which is a metal non-magnetic thin film, and a second magnetic film 6 which is a metal magnetic thin film facing the magnetization fixing film 7 in this order. Are stacked on each other. The first magnetic film 4 is the variable magnetic film 1
Of the signal magnetic field H and the magnetization direction of the first magnetic film 4 are
_{When 1} is zero, they are set to be almost orthogonal to each other.

Moreover, the thickness of the coupling film 5 is such that the first magnetic film 4 and the second magnetic film 6 are magnetically coupled to each other via the coupling film 5 in the strongest antiferromagnetic manner. It is set so that it is the thinnest.

According to the configuration of the above embodiment, the magnetization M ₂ of the first magnetic film 4 and the magnetization M ₃ of the second magnetic film 6 are antiferromagnetically coupled by the coupling film 5, It becomes antiparallel to each other.

The magnetic coupling energy between the two magnetic thin films 4 and 6 is determined by the materials constituting the multilayer film.
When converted to the value of the magnetic field by selecting the film thickness, the maximum is several
Since it reaches 0 (kilo-Oersted), even if a signal magnetic field H ₁ is applied as usual, both magnetic thin films 4
The magnetizations M ₂ and M ₃ of 6 are fixed in the antiparallel state, and the change of the magnetization direction with respect to the change of the magnetic field direction of the signal magnetic field H ₁ is prevented.

On the other hand, the magnetization fixing film 7 made of a hard magnetic material.
The direction of the magnetization M ₃ of the second magnetic film 6 in contact with is pinned, that is, fixed by the magnetization fixing film 7 by the exchange interaction between the magnetization fixing film 7 and the second magnetic film 6. It Therefore, the magnetization direction of the first magnetic film 4 is fixed based on the magnetization direction of the magnetization fixing film 7.

On the other hand, the direction of the magnetization M ₁ of the variable magnetic film 1 made of a soft magnetic material is orthogonal to the magnetization M _{2 in accordance} with the change of the magnetic field direction of the applied signal magnetic field H ₁ . (in the figure, the magnetization M ₁ in the initial state shown by the two-dot chain line) magnetization M ₁ in the initial state from the changes so as to rotate along the thickness direction end face of the variable magnetization film 1.

[0056] Thus, the variable magnetic film 1 in each direction of the relative angle of each magnetization M ₁ · M ₂ of the first magnetic layer 4, in response to the change of the signal magnetic field H ₁ from the outside, the signal magnetic field H ₁ Centering on the orthogonal state when is zero, the magnetizations M ₁ and M ₂ change within a range where they are parallel and antiparallel.

From the above, in the above-mentioned structure, with respect to the change of the signal magnetic field H ₁ , the state in which the relative angles of the respective magnetizations M ₁ and M ₂ are orthogonal to each other is the center, that is, with respect to the change of the relative angle. , The signal magnetic field H changes because it changes centering on the orthogonal state where the change in electrical resistance is the largest.
_With respect to the change of _1, a giant magnetoresistive effect in which the change in electric resistance is several times larger than that in the normal magnetoresistive effect can be exhibited.

Moreover, in the above structure, the fixed magnetization film 3 is formed.
However, since it has the first magnetic film 4 and the second magnetic film 6 that are strongly antiferromagnetically coupled to each other via the coupling film 5, the value of the saturation magnetization of the fixed magnetization film 3 is Apparently, the magnetic thin films 4 and 6 behave so as to have a difference with respect to the signal magnetic field H ₁ . Therefore, by setting the respective products of the saturation magnetization and the film thickness of both the magnetic thin films 4 and 6 so as to be substantially equal to each other, the value of the synthetic saturation magnetization of the fixed magnetic film 3 is reduced, for example, almost zero. Can be

From the above, in the above structure, since the strength of the demagnetizing field of the magnetic thin film is proportional to the saturation magnetization of the magnetic thin film, the value of the demagnetizing field of the fixed magnetic film 3 is greatly reduced, for example, to zero. You can do it.

By the way, conventionally, in the above structure, in order to detect the change in the signal magnetic field H ₁ with high resolution, the width of each film such as the variable magnetic film and the fixed magnetic film is narrow, for example, 1 μm or less. When set, the demagnetizing field generated in the fixed magnetic film is increased, so that the sensitivity for detecting the change in the signal magnetic field H ₁ is lowered by the demagnetizing field.

However, in the above configuration, the value of the demagnetizing field can be greatly reduced, for example, to zero, so that destabilization of the magnetization direction in the first magnetic film 4 due to the demagnetizing field can be suppressed. As a result, the setting of the relative angle between the magnetization direction of the variable magnetization film 1 and the magnetization direction of the first metal magnetization thin film 4 can be maintained in an optimum state, and the signal magnetic field caused by the deviation from the optimum value can be maintained. It is possible to avoid a decrease in sensitivity for detecting a change in H ₁ .

Further, in the above structure, similarly, the bias magnetic field applied from the fixed magnetic film 3 to the variable magnetic film 1 can be significantly reduced, for example, set to zero, so that the variable magnetic film 1 caused by the bias magnetic field is generated. It is possible to prevent the deviation of the magnetization direction that occurs and the deviation from the initial state.

Therefore, in the above configuration, the variable magnetic film 1
The relative angle between the magnetization direction of the first magnetic film 4 and the magnetization direction of the first magnetic film 4 can be maintained in an optimum state, and the sensitivity for detecting the change in the signal magnetic field H ₁ due to the deviation from the above-mentioned setting can be reduced. It can be avoided.

By the way, in the conventional spin-valve type magnetic sensor, the structure of the magnetic sensor is set so as to cancel the bias magnetic field from the fixed magnetization film by the magnetic field generated by the sense current. It is known that when the signal magnetic field is zero, the direction of magnetization of the variable magnetic film is set in the element longitudinal direction, that is, it is set by the magnetic field by the sense current so as to be orthogonal to the fixed magnetic film. (For example, IEEE Trans.
Magn. Vol.30, pp. 3801 (1994) "Design, Fabrication
& Testing of Spin-Valve Read Heads for High Densi
ty Recording ").

However, in the above-mentioned configuration of the present application, the apparent saturation magnetization value of the fixed magnetization film 3 can be freely set optimally, so that the structure of the magnetic sensor and the sense current are canceled with the bias magnetic field as in the conventional case. Since it is possible to avoid the restriction on the degree of freedom in design in the conventional magnetic sensor, it is possible to greatly improve the degree of freedom in designing the magnetic sensor while realizing excellent characteristics that suppress the adverse effect of the bias magnetic field. It will be possible.

[0066] Incidentally, in order to the highest sensitivity to changes in the signal magnetic field H _1, the signal magnetic field H ₁ is a variable magnetization film 1 at zero and the first magnetic layer 4, the orthogonal their respective magnetization directions to each other When set so that the variable magnetic film 1 is likely to be adversely affected by the bias magnetic field from the fixed magnetic film 3.

However, in the above configuration, since the bias magnetic field can be set to substantially zero as in the above configuration, the above adverse effect can be avoided while maintaining high sensitivity, and the effect of the present invention can be most remarkably exhibited.

Moreover, in the above configuration, the apparent synthetic saturation magnetization of the fixed magnetization film 3 is reduced, so that the change in the magnetization direction of the first magnetic film 4 with respect to the change in the signal magnetic field H ₁ can be suppressed. Even if the coupling magnetic field between the fixed film 7 and the fixed magnetic film 3 is set small, it is possible to stabilize the magnetization direction of the first magnetic film 4 in a fixed state.

From the above, it can be said that the above-mentioned configuration can increase the degree of freedom in designing the material and film thickness of the magnetization fixing film 7 and the fixed magnetization film 3 while more stably exhibiting the giant magnetoresistive effect. Has become.

Next, a magnetic head of the present invention using the above magnetic sensor will be described below with reference to FIGS. 3 to 5. The magnetic head of the present invention has the structure shown in FIG.
As shown in FIG. 5, the magnetic sensor 50 and the respective shields 54, 54 sandwiching the magnetic sensor 50 from both sides in the thickness direction, use only the signal magnetic field H ₁ from the hard disk 52 as a recording medium. It is provided in order to cut off the influence of the external magnetic field which is introduced into the signal generator 50 and becomes noise different from the signal magnetic field H ₁ .

The magnetic head has a magnetic sensor 50.
Power supply 51 for supplying a sense current to the sensor, and a detector (detection means) 5 for detecting a change in electric resistance of the magnetic sensor 50 due to a change in the signal magnetic field H ₁ by the power supply of the power supply 51.
3 and 3 are provided.

Such a magnetic head is used as follows. First, as shown in FIG.
Of the magnetization 52 along the recording track 52a having a predetermined width.
Information is recorded by the change in each direction of b. Therefore, in the magnetic head, the longitudinal direction of the magnetic sensor 50 is along the width direction of the recording track 52a, and the thickness direction of the magnetic sensor 50 is the longitudinal direction of the recording track 52a in the moving direction of the recording track 52a. In addition, the width direction of the magnetic sensor 50 is set to be perpendicular to the recording surface of the recording track 52a.

With respect to such a magnetic head, the change in the magnetic field direction which becomes the signal magnetic field H _{1 due} to the movement of the hard disk 52 varies among the following three states.

First, as shown in FIG. 5A, the first point is that the signal magnetic field H ₁ is changed as the hard disk 52 moves.
When the signal magnetic field 52c is formed along the width direction of the magnetic sensor 50 and toward the recording track 52a which is the recording surface of the hard disk 52.

Next, as shown in FIG. 5B, the second point is that the signal magnetic field 52 is moved as the hard disk 52 moves.
This is when c is along the thickness direction of the magnetic sensor 50 and the magnetic field direction is formed substantially parallel to the recording track 52a.

Finally, as shown in FIG. 5C, the third point is that the signal magnetic field 52 is moved as the hard disk 52 moves.
This is when c is along the width direction of the magnetic sensor 50 and the magnetic field direction is formed vertically outward from the recording track 52a.

According to the above configuration, when the magnetic sensor 50 is moved relative to the hard disk 52 by rotating the hard disk 52, each signal magnetic field 52c generated by each magnetization 52b is used as the signal magnetic field H _1. It will pass through 50. At this time, the component of the signal magnetic field H ₁ in the width direction of the magnetic sensor 50 affects the magnetization direction M ₁ of the variable magnetic film ₁ to change the magnetization direction M ₁ .

With the above structure, the adverse effects of the above-mentioned demagnetizing field and bias magnetic field in the magnetic sensor 50 can be prevented.
The magnitude of the change in electric resistance in the magnetic sensor 50 due to the change in the signal magnetic field H ₁ caused by the relative movement of the hard disk 52 with respect to the magnetic sensor 50 can be made larger and more stable than before as described above. Therefore, the area of the magnetization 52b which is the recording area in the hard disk 52 that can be detected by the detector 53 can be set smaller.

From the above, with the above configuration, the above-mentioned information can be detected more reliably from the hard disk 52 in which the recording density of the information depending on the direction of the magnetization 52b is further increased, and the information recorded on the hard disk 52 can be detected. This makes it possible to deal with higher density and ensure the detection of the above information.

[0080]

[First Embodiment] The following will describe one embodiment of the present invention as a first embodiment with reference to FIGS. 1, 2 and 6. In the magnetic sensor of the first embodiment of the present invention, as shown in FIG.
And as shown in FIG. 2, the variable magnetization film 1 is made of Co, NiFe,
It is desirable that a thin film made of a magnetic material such as NiCo or NiFeCo is formed by means such as sputtering or vapor deposition and has a thickness of 1 to 10 nm. Since the variable magnetic film 1 must have high magnetic permeability and high magnetoresistance change, it may be a composite film of the above magnetic materials. As the variable magnetization film 1, specifically, a NiFe sputtered film with a thickness of 5 nm was used. The variable magnetic film 1 had a coercive force of 1.5 oersted and a saturation magnetization value of 10,000 gauss.

The non-magnetic film 2 is preferably made of a material such as Cu, Au, Ag formed by sputtering, vapor deposition or the like. The film thickness of the non-magnetic film 2 is within a range in which the magnetic coupling between the variable magnetization film 1 and the first magnetic film 4 does not increase, and the change in magnetic resistance due to the shunt (shunt effect) of the current path is reduced. Is selected to be a minimum, specifically, 1
It is desirable to set it to be ~ 10 nm. As the non-magnetic film 2, specifically, a Cu sputtered film having a thickness of 2 nm
Used in.

The combination of the first magnetic film 4, the coupling film 5 and the second magnetic film 6 forming the fixed magnetization film 3 and the film thicknesses thereof are between those of the first magnetic film 4 and the second magnetic film 6. They are selected so that the antiferromagnetic coupling is strong.

The combinations forming the fixed magnetization film 3 are Co / Cu / Co, Co / Re / Co, Co / Mo / Co, Co / Rh / Co, Co / V / Co.
It is desirable to form them by means such as a combination of sputtering, vapor deposition and the like. First magnetic film 4 and second magnetic film 6
The film thickness of is preferably set to a thickness of 1 to 10 nm.

The magnetic coupling between the first magnetic film 4 and the second magnetic film 6 is a ferromagnetic coupling and an antiferromagnetic coupling as shown in FIG. 6, as the thickness of the coupling film 5 increases. While alternately vibrating between the first magnetic film 4 and the second magnetic film 6, the first magnetic film 4 and the second magnetic film 6 are gradually separated from each other.

The thickness of the coupling film 5 is usually called the first peak (1st peak) which is the thinnest film thickness among the film thicknesses at which the extreme value of the antiferromagnetic coupling energy is produced. It is preferable to set the film thickness, usually 0.3 to 2n
A film having a thickness of about m is formed by sputtering, vapor deposition or the like.

As the first magnetic film 4, a Co sputtered film having a film thickness of 3 nm (coercive force 50 Oersted, saturation magnetization 170
0 Gauss), a Co sputtered film as the second magnetic film 6 with a film thickness of 3 nm (coercive force 50 Oersted, saturation magnetization 1700 Gauss), and a Cu sputtered film as the coupling film 5, The thickness of the coupling film 5 was 1 nm when it showed the first peak.

The magnetization fixing film 7 for fixing the magnetization direction of the second magnetic film 6 is an antiferromagnetic thin film and is made of FeMn, NiO, NiMn.
The sputtered film or vapor-deposited film of 10 to 100 nm of
It is formed under the condition that the pinning effect on the magnetic film 6 is high. Specifically, a FeMn sputtered film with a thickness of 15 nm was used. Each of the thin films 1 to 8 is processed into the shape shown in FIG. 1 by photoetching.

[Second Embodiment] Another embodiment of the present invention will be described as a second embodiment.
As an example, referring to FIGS. 7 and 8,
It is as follows. In the second embodiment, members having the same functions as those in the first embodiment are designated by the same member numbers, and the description thereof is omitted.

The magnetic sensor of the second embodiment of the present invention is the first
As shown in FIGS. 7 and 8, CoPt, CoP, NiCo is used instead of the magnetization fixing film 7 which is the antiferromagnetic thin film in the embodiment.
The magnetization fixing film 27 which is a high coercive force magnetic thin film such as the above is used. Specifically, the CoPt sputtered film has a thickness of 15 n.
m (coercive force 1800 oersted, saturation magnetization 400 gauss).

[0090] Then, the magnetization M ₂ of the first magnetic layer 4 magnetization M ₃ and is anti-parallel to each other in the second magnetic layer 6, and the magnetization M ₁₂ of the magnetization M ₃ and the magnetization fixing layer 27 of the second magnetic film 6 Are parallel to each other, the saturation magnetization and film thickness of each of the magnetic thin films 4 and 6 and the magnetization fixing film 27 are set so that M ₂ = M ₃ + M ₁₂ is satisfied, Magnetized film 3
Further, it becomes possible to make the synthetic saturation magnetization, which shows an apparent magnetic influence on the outside as a whole of the magnetization fixing film 27, substantially zero. Therefore, the second embodiment also has the same effect as that of the first embodiment.

Further, in the above configuration, the apparent synthetic saturation magnetization of the fixed magnetization film 3 and the magnetization fixing film 27 as a whole is lowered, so that the magnetization direction of the first magnetic film 4 with respect to the change of the signal magnetic field H _1. Since it can suppress the change of
Even if the coupling magnetic field between the magnetization fixing film 27 and the fixed magnetization film 3 is set small, that is, the coercive force of the magnetization fixing film 27 is set small, the magnetization direction of the first magnetic film 4 is fixed. Can be stabilized.

From the above, with the above configuration, it is possible to increase the degree of freedom in setting the material and film thickness of the magnetization fixing film 27 while exhibiting the giant magnetoresistive effect more stably.

[Third Embodiment] The following description will explain still another embodiment of the present invention as a third embodiment with reference to FIGS. 9 and 10. In the third embodiment, members having the same functions as those in the first and second embodiments are given the same member numbers and their explanations are omitted.

The magnetic sensor of the third embodiment of the present invention is the first
In place of the magnetization fixing film 7 and the second magnetic film 6 which are antiferromagnetic thin films in the embodiment, a high coercive force magnetic film 35 is used as shown in FIGS. 9 and 10. The high coercive force magnetic film 35 may be made of CoPt, NiCo, CoP, etc.
A material having a sufficient coercive force even with a film thickness of nm is selected. Specifically, the CoPt sputtered film has a thickness of 5 nm (coercive force 1800 Oersted, saturation magnetization 400 gauss).
Used in.

Regarding the first magnetic film 4 and the coupling film 5,
Similar to the first embodiment, the first magnetic film 4 and the high coercive force magnetic film 3 are formed.
The thicknesses and materials of the thin films 4, 5, and 35 are selected so that the antiferromagnetic coupling between the thin films 4 and 5 is maximized.

That is, as the first magnetic film 4, 1-10
nm sputtered film made of Co, NiCo, FeNiCo, NiFe, etc.,
Alternatively, a vapor deposition film is preferable. Specifically, a Co sputtered film was used with a thickness of 1.5 nm (coercive force 50 Oersted, saturation magnetization 1700 gauss). As the coupling film 5, 0.2
A film of Cu, Re, Mo, Rh of about 2 nm is desirable. Specifically, a Cu sputtered film having a thickness of 1 nm was used.

As in the first and second embodiments, the magnetization M ₁₅ of the high coercive force magnetic film 35 is set such that the magnetization of the fixed magnetization film 3 as a whole is apparently zero with respect to the outside. And the magnetization M ₂ of the first magnetic film 4 are set to be approximately equal to each other and antiparallel to each other. Therefore, the third embodiment also has the same effect as that of the first embodiment.

Further, in the above-mentioned structure, since the apparent synthetic saturation magnetization of the fixed magnetization film 3 is lowered, the change of the magnetization direction of the first magnetic film 4 with respect to the change of the signal magnetic field H ₁ can be suppressed, so that the high coercive force is high. Even if the coercive force of the magnetic film 35 is set small, the magnetization direction of the first magnetic film 4 is changed to the signal magnetic field H.
_It can be stabilized in a fixed state against a change of ₁ . Therefore, in the above configuration, the degree of freedom in setting the material and the film thickness of the high coercive force magnetic film 35 can be increased while exhibiting the giant magnetoresistive effect more stably.

[0099]

As described above, the magnetic sensor of the present invention has the following features.
A variable magnetic film whose magnetization direction changes according to a change in the magnetization direction of an applied magnetic field, a non-magnetic film, and a fixed magnetic film are laminated so as to exhibit a giant magnetoresistive effect, and the fixed magnetic film is non-magnetic. A first magnetic film facing the film and a second magnetic film,
This is a structure in which they are antiferromagnetically coupled to each other.

Therefore, in the above structure, the change in the relative angle of the magnetization direction between the first magnetic film and the variable magnetic film causes
The giant magnetoresistive effect that the electric resistances of the variable magnetic film, the nonmagnetic film, and the fixed magnetic film change greatly can be exhibited.

Moreover, in the above structure, since the first magnetic film and the second magnetic film in the fixed magnetization film are antiferromagnetically coupled to each other, the magnetizations of the first magnetic film and the second magnetic film are different from each other. Can be anti-parallel to each other.

From the above, in the above structure, it is possible to suppress the apparent saturation magnetization of the pinned magnetic film with respect to the outside from the antiparallel state, so that the demagnetizing field generated in the pinned magnetic film is suppressed. Especially, since the resolution of the applied magnetic field is increased, the size can be suppressed even when the size is reduced.

Therefore, in the above configuration, when the applied magnetic field is zero, the relative angle between the magnetization direction of the magnetization film of the first magnetic film and the magnetization direction of the variable magnetization film is optimally set, for example, the above relative angle. When they are set so as to be orthogonal to each other, it is possible to reduce fluctuations in the setting due to the demagnetizing field, that is, adverse effects such as non-uniformity of the magnetization direction of the fixed magnetization film and deviation from the predetermined direction. It is possible to improve the sensitivity of detecting changes in the applied magnetic field while achieving higher resolution.

In addition, in the above-mentioned structure, since the bias magnetic field applied to the variable magnetic film by the fixed magnetic film can be reduced, the change due to the bias magnetic field with respect to the setting, that is, the non-uniformity of the magnetization direction of the variable magnetic film, a predetermined value. Since it is possible to reduce adverse effects such as deviation from the direction, it is possible to improve the sensitivity of detecting a change in the applied magnetic field while achieving high resolution in detecting the applied magnetic field.

In the magnetic head of the present invention, the magnetic sensor, the power supply for energizing the magnetic sensor, and the recording medium on which information is recorded by the change in the magnetic direction are moved relative to the magnetic sensor. And a detection unit that detects a change in the electrical resistance of the magnetic sensor due to a change in the magnetic field applied to the magnetic sensor based on the change in (1) by the energization of the power source.

According to the above arrangement, the magnitude of the change in the electric resistance in the magnetic sensor caused by the change in the applied magnetic field due to the relative movement of the recording medium with respect to the magnetic sensor is larger than that in the conventional case. Therefore, it is possible to set a smaller magnetization area, which is a recording area of information on the recording medium, which can be detected by the detecting means.

From the above, the above-mentioned structure can more reliably detect the above-mentioned information from the recording medium in which the recording density of the information depending on the magnetization direction is further increased, and the high-density of the information recorded in the recording medium is obtained. It is possible to cope with the increase in the number of times, and it is possible to ensure the detection of high-density information.

[Brief description of drawings]

FIG. 1 is a fragmentary perspective view of a magnetic sensor of the present invention.

FIG. 2 is a front view of the magnetic sensor.

FIG. 3 is a fragmentary perspective view showing a magnetic head of the present invention.

FIG. 4 is a front view of the magnetic head.

FIG. 5 is a main part perspective view showing an operating state of the magnetic head.

FIG. 6 is a graph showing changes in magnetic coupling between the first metal magnetic thin film and the second metal magnetic thin film with respect to changes in the thickness of the coupling film in the magnetic sensor.

FIG. 7 is a fragmentary perspective view showing another magnetic sensor of the present invention.

FIG. 8 is a front view of the magnetic sensor.

FIG. 9 is a fragmentary perspective view showing still another magnetic sensor of the present invention.

FIG. 10 is a front view of the magnetic sensor.

FIG. 11 is a fragmentary perspective view of a conventional magnetic sensor.

FIG. 12 is a front view of the magnetic sensor.

FIG. 13 is an explanatory diagram showing formation of a demagnetizing field in the magnetic sensor.

[Explanation of symbols]

 1 Variable Magnetic Film 2 Non-Magnetic Film 3 Fixed Magnetic Film 4 First Magnetic Film 5 Coupling Film 6 Second Magnetic Film

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Keiya Nakabayashi 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka

Claims (8)

[Claims] 1. A magnetic sensor in which a variable magnetic film whose magnetization direction changes according to a change in the magnetic field direction of an applied magnetic field, a non-magnetic film, and a fixed magnetic film are laminated so as to exhibit a giant magnetoresistive effect. In the magnetic sensor, the fixed magnetic film includes a first magnetic film facing the non-magnetic film and a second magnetic film, which are antiferromagnetically coupled to each other. 2. A pinning film made of a magnetic material is laminated on the pinned magnetic film so as to pin the magnetizing direction of the pinned magnetic film based on the magnetizing direction of the pinned film. The magnetic sensor according to claim 1. 3. A coupling film made of a metal non-magnetic material is formed between the first magnetic film and the second magnetic film so as to increase antiferromagnetic coupling between the first magnetic film and the second magnetic film. The magnetic sensor according to claim 1 or 2, wherein the magnetic sensor is laminated on the magnetic sensor. 4. The magnetic film according to claim 3, wherein the coupling film is set to be thin within a range in which the first magnetic film and the second magnetic film are antiferromagnetically coupled. Sensor. 5. The saturation magnetizations of the first magnetic film and the second magnetic film and the film thicknesses of the first magnetic film and the second magnetic film so that the value of the synthetic saturation magnetization in the fixed magnetization film is reduced. The magnetic sensor according to claim 1, 2, 3, or 4, wherein: is set. 6. The saturation magnetization of the pinning film, the first magnetic film and the second magnetic film, the pinning film, the first magnetic film and the first magnetic film so that the value of the synthetic saturation magnetization in the pinned magnetic film is reduced. The magnetic sensor according to claim 2, 3 or 4, wherein respective film thicknesses of the two magnetic films are set. 7. The magnetic sensor according to claim 5, wherein the value of the synthetic saturation magnetization, which is the apparent saturation magnetization of the fixed magnetization film, is set to be substantially zero. 8. The magnetic sensor according to claim 1, a power supply for energizing the magnetic sensor, and a recording medium on which information is recorded due to a change in the magnetization direction, moves relative to the magnetic sensor. A magnetic head comprising: a change in the electrical resistance of the magnetic sensor caused by a change in the magnetic field applied to the magnetic sensor based on the change in the magnetization direction.