JPH09283816A - Magnetoresistive sensor for sensing magnetic field - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a differential magnetoresistive sensor by providing a first spin valve, having means for detecting a change of electric resistance caused by the difference of rotation of a ferromagnetic material in an external magnetic field, a second spin valve by which magnetized direction of a third ferromagnetic layer and a magnetized direction of a fourth ferromagnetic layer are orthogonal to each other when an applied magnetic field is zero, and detection means. SOLUTION: When a vertical signal magnetic field enters from a magnetic recording medium 10, the magnetized directions of magnetic films 4 and 4' rotate within the surfaces of the magnetic films 4 and 4' in accordance with the direction of the signal magnetic field. If the magnetic field is upward, within the surface of the magnetic film 4', the magnetized direction rotates so as to be closer to a direction opposite to a direction M4, and the resistance of a spin valve 2 becomes lower, while the resistance of a spin valve 3 becomes higher. If the magnetic field is downward, in the surface of the magnetic film 4', the magnetized direction rotates so as to be closer to the direction M4, and the resistance of the spin valve 2 becomes higher, while the resistance of the spin valve 3 becomes lower. Thus, in the magnetic resistive sensor, the changes of electric resistance with respect to the same signal magnetic field are symmetrical, and output signals are detected from the spin valves 2 and 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetoresistive (MR) sensor that utilizes the spin valve effect and senses a magnetic field, and more particularly, it has a set of electrically isolated spin valve elements. Such a magnetic sensor.

[0002]

2. Description of the Related Art As a read head of a magnetic recording device represented by a hard disk drive, a giant magnetic resistance (G) is used.
A magnetic sensor utilizing the MR effect is disclosed in "A magnetoresistive sensor utilizing the spin valve effect" (Japanese Patent Laid-Open No. 4-358310).
Japanese patent publication). This magnetic sensor has a sandwich structure in which two uncoupled ferromagnetic layers separated by a nonmagnetic metal layer are provided, and the magnetization of one ferromagnetic layer is fixed. The fixed magnetization is iron-
An antiferromagnetic metal layer represented by a manganese alloy is attached to one of the ferromagnetic layers. In this structure, when an external magnetic field is applied, the magnetization direction of the non-fixed ferromagnetic layer coincides with the direction of the external magnetic field and rotates freely. Therefore, the magnetization direction of the fixed ferromagnetic layer is fixed. And an angle difference occurs.
Depending on this angle difference, the scattering of conduction electrons depending on the spin changes, and the electric resistance value changes. The state of the external magnetic field, that is, the signal magnetic field from the magnetic recording medium is acquired by detecting the change in the electric resistance value.

The resistance change of the spin valve magnetoresistive sensor is about 5%, but a magnetoresistive sensor having a larger change in magnetic resistance is required to prevent a read error due to an increase in magnetic recording density. ing. Further, in the magnetic head, the magnetic head may come into direct or indirect contact with the medium due to protrusions or dust of the magnetic recording medium, and at the contact point, frictional heat causes a rapid temperature rise. It is known that this temperature change causes a change in the resistance of the MR element and causes an output fluctuation. This output fluctuation is called thermal asperity or thermal noise, and as a conventional technique excluding this thermal asperity, there is one described in Japanese Patent Application Laid-Open No. 2-154310. This is a method in which two MR elements are provided, the two MR elements are made to be of a differential type, and differential detection is performed to cancel the thermal aspirity.

[0004]

By making the spin valve magnetoresistive sensor a differential type, it is possible to improve the output about twice and cancel the thermal aspirity. However, in the method described in the prior art, Since the track width for two MR elements is required, it is not possible to deal with the narrowing of tracks accompanying the increase in recording density. It is an object of the present invention to provide a magnetoresistive head having a large reproduction output and capable of removing thermal aspirity by using a spin valve magnetoresistive sensor as a laminated detection mechanism.

[0005]

In order to solve the above problems, the present invention provides a magnetoresistive sensor having a laminated structure in which a pair of spin valve structures are separated by an insulating layer. That is, the present invention comprises first and second ferromagnetic thin films separated from each other by a non-magnetic spacer layer, and when the applied magnetic field is zero, the magnetization direction of the first ferromagnetic layer and the The magnetization direction of the second ferromagnetic layer fixed by the first antiferromagnetic thin film layer (exchange bias layer) adjacent to the second ferromagnetic layer is a direction orthogonal to each other, and A first spin valve structure having means for detecting a change in electrical resistance caused by a difference in rotation of magnetization of each layer of the ferromagnetic material, and a first spin valve structure separated from each other by a non-magnetic spacer layer. In addition, the third and fourth ferromagnetic thin films are provided, and when the applied magnetic field is zero, the magnetization direction of the third ferromagnetic layer and the second antiferromagnetic layer adjacent to the fourth ferromagnetic layer. The fourth fixed by a thin film layer (exchange bias layer) of the body Of the second spin magnetic field having a direction perpendicular to the magnetization direction of the ferromagnetic layer, and having means for detecting an electric resistance change caused by a difference in rotation of magnetization of each layer of the ferromagnetic body by an external magnetic field. Valve (Spin V
alv) structure, an insulating layer electrically insulating between the first and second spin valve structures, and spin layers for each of them.
And a means for detecting the output from the valve structure.

Although it is possible to increase the reproduction output by obtaining addition information from a pair of spin valve structures, by obtaining the difference information, it is possible to eliminate the thermal aspirity while increasing the reproduction output. In order to configure the differential output mechanism, the magnetization direction of the fixed ferromagnetic layer must be 180 degrees in each spin valve configuration. This is achieved by the two methods described below.

As the first method, the exchange bias direction is independently set by using materials having different blocking temperatures in the respective spin valve configurations for the exchange bias layer for fixing the magnetization direction of the ferromagnetic layer. You can For example, in the case of iron-manganese and nickel-manganese, the iron-manganese blocking temperature is about 220 ° C and the nickel-manganese blocking temperature is 300 ° C.
That is all. Therefore, first, after setting the exchange bias direction of the nickel-manganese layer at a high temperature, set the exchange bias direction of the iron-manganese in a DC magnetic field at a temperature slightly higher than the blocking temperature of iron-manganese, for example, 230 ° C. Thus, the exchange bias directions can be set independently (with a phase difference of 180 degrees).

As a second method, an antiferromagnetic coupling film made of a nonmagnetic metal thin film is interposed between a ferromagnetic layer whose magnetization direction is fixed by the exchange bias layer and the exchange bias layer. Add a ferromagnetic layer. A laminated structure composed of a ferromagnetic material / a non-magnetic metal / a ferromagnetic material has a non-magnetic metal layer (antiferromagnetic coupling film) with an appropriate thickness, as seen in the multilayer GMR material. It is known that the magnetization directions of two adjacent ferromagnetic layers are antiparallel. This preferred embodiment includes Fe2 nm / Cr1.
A large antiferromagnetic coupling is obtained with a structure such as 3 nm / Fe2 nm, Co2 nm / Cu0.7 nm / Co2 nm. For this reason, the fixed ferromagnetic layer adjacent to the exchange bias layer made of an antiferromagnetic material has the above-mentioned antiferromagnetic layered structure, so that it is antiparallel to the original magnetization fixed direction (phase difference of 180 degrees).
It is possible to obtain a ferromagnetic layer having a fixed magnetization direction. Therefore, by making one of the fixed ferromagnetic layers of the spin valve structure an antiferromagnetic layered structure, a pair of spin layers having a phase difference of 180 degrees by one exchange biasing process (heat treatment in a DC magnetic field). A valve magnetoresistive sensor is obtained.

[0012] The stacked spin
In a valve magnetoresistive sensor, the output signal from each spin valve structure separated by an insulating layer is an output signal that is in anti-phase with the external magnetic field. That is,
In the first spin-valve structure, when the exchange bias direction is set to be a vertically upward direction with respect to the magnetic recording medium surface,
The exchange bias direction of the second spin valve structure is vertically downward with respect to the magnetic recording medium surface. Therefore, when the applied magnetic field is zero, the magnetization directions of both fixed ferromagnetic layers are 90 degrees, and the free ferromagnetic layers magnetized in the same direction are vertically upward with respect to the magnetic recording medium surface. In the first spin-valve structure, the magnetization direction of the free ferromagnetic layer is oriented vertically upward with respect to the magnetic recording medium surface, that is, in the direction aligned with the magnetization direction of the fixed ferromagnetic layer. As it rotates, the electric resistance changes in the direction of decreasing. In the second spin valve structure,
On the contrary, since the pinned ferromagnetic layer rotates in a direction aligned antiparallel to the magnetization direction of the pinned ferromagnetic layer, the electric resistance changes to increase. A differential spin valve magnetoresistive sensor can be constructed by detecting these outputs independently and reproducing them using a differential amplifier circuit.

By using the magnetoresistive head of the present invention, the reproduction output is large and the thermal aspirity can be eliminated.

[0011]

【Example】

 Example 1 FIG. 1 shows the configuration of this example. 1 is Al_TwoO_ThreeInsulating film
And this Al_TwoO _ThreeA pair of spins sandwiching an insulating film
The valve structures 2 and 3 are laminated. Spin valve structure
In both structures 2 and 3, both are Ni₈₁Fe₁₉Magnetic film 4, 5
It has a laminated structure in which the Cu spacer layer 6 is interposed,
Ni in the spin valve structure 2₅₀Mn₅₀Exchange bias membrane
7, Fe in spin valve structure 3₅₀Mn₅₀Exchange via
The film 8 is laminated. The magnetic films 4 and 5 are made of Ni, Fe,
One or more magnetic metal films composed of Co and these alloys
It is also possible to use. The spacer layer 6 is made of Au, A
g, Cu and non-magnetic metal group consisting of these alloys
It is also possible to use a metal film that is exposed. Also spin
・ Valve structures 2 and 3 have different magnetic films and spaces.
The same effect can be obtained by using the support layer.

A pair of electrodes 9 are formed via an insulating film 19.
Ni on the substrate 20₅₀Mn₅₀Antiferromagnetic film 7 is 10 nm, N
i₈₁Fe₁₉The magnetic film 5 is 4 nm, the Cu spacer layer 6 is 2 nm,
Ni ₈₁Fe₁₉Magnetic film 4 is 10 nm, Al_TwoO_ThreeInsulating film 1
20nm, Ni₈₁Fe₁₉Magnetic film 4'with 10nm, Cu spacing
The layer 6'is 2 nm, Ni₈₁Fe₁₉Magnetic film 5'with 4 nm, Fe
₅₀Mn₅₀The antiferromagnetic film 8 is laminated to a thickness of 10 nm, and again on top of it.
A pair of electrodes 9 was formed. As a method of forming this laminated film
Is a sputtering method, ion beam sputtering method, vapor deposition method, etc.
Either method can be used. In addition, elementization
At that time, ordinary photolithography technology was used.
A process such as ion milling can be used.

As shown in FIG. 2, the sense current I _S flows in the track width direction, and the signal magnetic field H from the magnetic recording medium 10 is generated.
_SIG enters from the direction parallel to the laminated film interface and perpendicular to the sense current I _S. In FIG. 2, V is a medium moving direction 30 and a lead. Ni ₅₀ Mn ₅₀ exchange bias film 7, Fe ₅₀ Mn ₅₀
The exchange bias film 8 has antiparallel magnetic anisotropies M1 and M2.
Are provided, and as a result, the exchange bias films 7 and 8 are provided.
The magnetization directions of the magnetic films 5 and 5'adjacent to each other are fixed in directions M3 and M4 which are antiparallel to each other. With respect to the magnetization directions of the magnetic films 4 and 4 ′ laminated with the Cu spacer layers 6 and 6 ′ sandwiched therebetween, the easy axis M 5 is set in the sense current I _S direction when the external magnetic field is zero.

When a signal magnetic field H _{SIG in the} vertical direction from the magnetic recording medium 10 enters the magnetoresistive sensor, the magnetic film 5,
The magnetization directions M3 and M4 of 5'are the exchange bias films 7 and 8, respectively.
It does not change because it is fixed by the magnetic film 4, 4 '
The magnetization direction of the magnetic field rotates in the plane of the magnetic films 4 and 4'depending on the direction of the signal magnetic field H _{SI G.} In the case of the upward signal magnetic field H _SIG , it is close to the M3 direction within the surface of the magnetic film 4 and the magnetic film 4 '
In the plane, it rotates so as to be closer to the opposite direction with respect to the M4 direction. M3 and the M ₅ ² the spin-valve 2 so close in the same direction
The resistance value r ₂ becomes low. Since M4 and M ₅ ³ close to the opposite direction, the resistance value r ₃ of the spin valve 3 increases. In the case of the downward signal magnetic field H _SIG , the magnetic film 4 rotates in the plane of the magnetic film 4 so as to be closer to the opposite direction to the M3 direction, and in the plane of the magnetic film 4 ′ to the direction of M4. M3 and M ₅ ² is the resistance value r ₂ of the spin valve 2 is close to the opposite direction increases. Since M4 and M ₅ ³ is close to the same direction, the resistance value r ₃ of the spin valve 3
Becomes smaller. FIG. 3 shows the dependence of the resistance values r ₂ and r ₃ of the spin valve structures ₂ and _{3 on} the signal magnetic field H _SIG at this time. Since the electric resistance changes symmetrically with respect to the same signal magnetic field H _SIG , the output signals of the spin valve structures 2 and 3 are independently detected to operate as a differential magnetoresistive sensor.

Embodiment 2 FIG. 4 shows the configuration of another embodiment. Reference numeral 1 is an Al ₂ O ₃ insulating film, and a pair of spin valve structures 2 and 3 are laminated with the Al ₂ O ₃ insulating film interposed therebetween. In the spin valve structures 2 and 3, both are Ni ₈₁ Fe ₁₉ magnetic film 4,
5 is a laminated structure in which a Cu spacer layer 6 is interposed between
Ni ₅₀ Mn ₅₀ exchange bias films 7 and 8 are laminated. In the spin valve structure 3, the magnetic layer 5 includes the Cu antiferromagnetic coupling film 12 and the exchange bias layer 8 via the magnetic film 11.
It is stacked with. At this time, the exchange bias films 7 and 8 can use the same antiferromagnetic material. The other configurations of the magnetic layers 4 and 5 and the non-magnetic layer 6 are in accordance with the first embodiment.

A pair of electrodes 9 are formed via an insulating film 19.
Ni on the substrate 20₅₀Mn₅₀Antiferromagnetic film 7 is 10 nm, N
i₈₁Fe₁₉The magnetic film 5 is 4 nm, the Cu spacer layer 6 is 2 nm,
Ni ₈₁Fe₁₉Magnetic film 4 is 10 nm, Al_TwoO_ThreeInsulating film 1
20nm, Ni₈₁Fe₁₉Magnetic film 4'with 10nm, Cu spacing
The layer 6'is 2 nm, Ni₈₁Fe₁₉Magnetic film 5'is 4 nm, Cu
Antiferromagnetic coupling film 12 is 1 nm, Ni₈₁Fe₁₉Magnetic film 11
To 2 nm, Ni₅₀Mn₅₀10 nm of antiferromagnetic film 8 is laminated,
A pair of electrodes 9 was again formed on it.

As shown in FIG. 5, the sense current I _S flows in the track width direction, and the signal magnetic field H from the magnetic recording medium 10 is generated.
_SIG enters from the direction parallel to the laminated film interface and perpendicular to the sense current I _S. The exchange bias layers 7 and 8 are provided with magnetic anisotropy M1 and M2 in the same direction.
The magnetization directions of the magnetic films 5 and 11 adjacent to the exchange bias layers 7 and 8 are fixed in the same directions M3 and M6. At this time, in the spin valve structure 3, strong antiferromagnetic coupling is generated in the magnetic films 5 ′ and 11 via the Cu antiferromagnetic coupling film 12, so that the magnetization direction of the magnetic film 5 ′ is the same as that of the magnetic film 11. The magnetization is fixed in the magnetization direction M6, that is, in the M4 direction antiparallel to the magnetization direction M2 of the exchange bias layer 8. Cu spacer layer 6,
With respect to the magnetization directions of the magnetic films 4 and 4 ′ laminated with the 6 ′ sandwiched therebetween, when the external magnetic field is zero, the easy axis M 5 is set in the sense current I _S direction.

When a signal magnetic field H _{SIG in the} vertical direction from the magnetic recording medium 10 enters the magnetoresistive sensor, the magnetic film 5,
The magnetization direction of 5 ′ does not change because it is fixed by the exchange bias layers 7 and 8, but the magnetization directions of the magnetic films 4 and 4 ′ are
Depending on the direction of the signal magnetic field H _SIG , the magnetization direction M5 and the signal magnetic field H _SIG rotate in the planes of the magnetic films 4 and 4 '. At this time, each of the signal magnetic field H _SIG dependence of the resistance value r _2, r ₃ of the spin-valve structure 2 and 3 for the same signal magnetic field H _SIG as in FIG. 3 described above, symmetrical electrical resistance Since it shows a change, it operates as a differential magnetoresistive sensor by independently detecting the output signals of the spin valve structures 2 and 3.

Embodiment 3 FIG. 6 shows the configuration of another embodiment. 61 is NiO insulation
This is an exchange bias film, and this NiO insulating exchange bias
A set of spin valve structures 2 and 3 are laminated with the film 61 sandwiched therebetween.
Have been. Which of spin valve structures 2 and 3
Ramo Ni₈₁Fe ₁₉A Cu spacer layer 6 is formed between the magnetic films 4 and 5.
It is a laminated structure that is interposed. In Example 3, Example 1,
NiMn or FeMn exchange bias film used in No. 2
Use an insulating exchange bias film 61 in place of 7, 8
However, it is a feature. In addition, in spin valve structure 3
The magnetic layer 5'is the Cu antiferromagnetic coupling film 12, the magnetic film 1
1 is laminated with the NiO insulating exchange bias film 61 via
ing. The other magnetic and non-magnetic layer configurations are the same as in Example 1.
Conform.

A Ni ₈₁ Fe ₁₉ magnetic film 4 having a thickness of 10 nm, a Cu spacer layer 6 having a thickness of 2 nm, and a Ni ₈₁ Fe ₁₉ magnetic film 5 having a thickness of 4 nm and Ni are formed on a substrate 20 on which a pair of electrodes 9 are formed via an insulating film 19.
The O insulating exchange bias film 61 is 20 nm, the Ni ₈₁ Fe ₁₉ magnetic film 11 is 2 nm, the Cu antiferromagnetic coupling film 12 is 1 nm, and N is N.
i ₈₁ Fe ₁₉ magnetic film 5'is 4 nm, Cu spacer layer 6'is 2 nm
nm, Ni ₈₁ Fe ₁₉ magnetic film 4 ′ was laminated in a thickness of 10 nm, and a pair of electrodes 9 ′ was formed again thereon.

As shown in FIG. 7, the sense current I _S flows in the track width direction, and the signal magnetic field H from the magnetic recording medium 10 is generated.
_SIG enters from the direction parallel to the laminated film interface and perpendicular to the sense current I _S. In the NiO insulating exchange bias layer 61,
Since the magnetic anisotropy M1 is given, the magnetization directions of the magnetic films 5 and 11 adjacent to the insulating exchange bias layer 61 are fixed in the same directions M3 and M6. At this time, in the spin valve structure 3, strong antiferromagnetic coupling is generated in the magnetic films 5 ′ and 11 via the Cu antiferromagnetic coupling film 12, so that the magnetization direction of the magnetic film 5 is the magnetization direction of the magnetic film 11. It is fixed in the direction M6, that is, in the direction M4 which is antiparallel to the magnetization direction M1 of the NiO insulating exchange bias layer 61. The magnetization directions of the magnetic films 4 and 4'laminated with the Cu spacer layers 6 and 6'in between are set to the easy axis M5 in the sense current I _S direction when the external magnetic field is zero.

The magnetic recording medium 10 is attached to the magnetoresistive sensor.
Perpendicular signal magnetic field H_SIGIn case of, the magnetic film 5,
The magnetization direction of 11 is due to the NiO insulating exchange bias layer 61.
It does not change because it is fixed to the magnetic film of the magnetic films 4 and 4 '.
Direction is the signal magnetic field H_SIGDepending on the orientation of the magnetic film 4,
It rotates in the 4'plane. Spin valve structure at this time
Resistance value r of 2 and 3_Two, R_ThreeSignal magnetic field H_SIGDependency is mentioned above
Same signal magnetic field H as shown in FIG._SIGSymmetric to
Spin valve structure2
By detecting the output signals of 3 independently,
Operates as a resistance sensor. Incidentally, Table 1, Table 2 and Table 3
In addition, the resistance value r in each of Examples 1, 2, and 3 _Two, R_Threeof
The supplementary explanation of the change is shown.

[0023]

[Table 1]

[0024]

[Table 2]

[0025]

[Table 3]

[0026]

As described above, by using the magnetoresistive sensor of the present invention, it is possible to provide a magnetoresistive head having a large reproduction output and excluding thermal aspirity.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a sensor according to a first embodiment.

FIG. 2 is a development view of the sensor according to the first embodiment.

FIG. 3 shows the output of the sensor of the first embodiment.

FIG. 4 is a schematic sectional view of a sensor according to a second embodiment.

FIG. 5 is a development view of the sensor according to the second embodiment.

FIG. 6 is a schematic cross-sectional view of a sensor of Example 3.

FIG. 7 is a development view of the sensor according to the third embodiment.

[Explanation of symbols]

 1 ... Insulating film 2, 3 ... Spin valve structure 4, 5, 4 ', 5' ... Magnetic film 6, 6 '... Spacer layer 7, 8 ... Exchange bias film 9, 9' ... Electrode 11 ... Magnetic film 12 ... Antiferromagnetic coupling film 19 ... Insulating film 20 ... Substrate 61 ... Insulating exchange bias film

Claims (9)

[Claims] 1. A first and a second ferromagnetic thin films, which are separated from each other by a non-magnetic spacer layer, are provided, and when the applied magnetic field is zero, the magnetization direction of the first ferromagnetic layer and the first ferromagnetic layer are different from each other. Two
Of the second antiferromagnetic material layer (exchange bias layer) adjacent to the first antiferromagnetic material layer is perpendicular to the magnetization direction of the second antiferromagnetic material layer, A first spin, having means for sensing a change in electrical resistance caused by a difference in the rotation of the magnetization of each layer of the ferromagnet;
A valve (Spin Valve) structure and third and fourth ferromagnetic thin films separated from each other by a non-magnetic spacer layer are provided, and when the applied magnetic field is zero, the magnetization direction of the third ferromagnetic layer. And a second antiferromagnetic thin film layer (exchange bias layer) adjacent to the fourth ferromagnetic layer
A means for detecting a change in electric resistance caused by a difference in rotation of magnetization of each layer of the ferromagnetic body by an external magnetic field is a direction in which the magnetization directions of the fourth ferromagnetic body layer fixed by are orthogonal to each other. Having a second spin valve (Spi
n Valve) structure, an insulating layer electrically insulating between the first and second spin valve structures, and means for detecting an output from each spin valve structure. Magnetoresistive sensor. 2. The magnetoresistive sensor according to claim 1, wherein differential information of outputs from the first spin valve structure and the second spin valve structure is detected. 3. In the first and second spin valve structures, the second pinned by an exchange bias layer.
3. The magnetoresistive sensor according to claim 1, wherein the magnetization directions of the fourth ferromagnetic layer are antiparallel. 4. The magnetoresistive sensor of claim 3, wherein the first and second exchange bias layers have different blocking temperatures. 5. The first and second exchange bias layers include:
5. The magnetoresistive sensor according to claim 4, wherein the magnetoresistive sensor comprises two different materials selected from an antiferromagnetic ordered alloy group consisting of iron-manganese, nickel-manganese and palladium-manganese and nickel monoxide. 6. The one of the second and fourth ferromagnetic layers whose magnetization directions are fixed by the first and second exchange bias layers, between one of the ferromagnetic layers and the exchange bias layer. The magnetoresistive sensor according to claim 3, further comprising: a fifth ferromagnetic layer having an antiferromagnetic coupling film formed of a nonmagnetic metal thin film interposed therebetween. 7. In the first and second spin valve structures, from an antiferromagnetic material that also serves as first and second exchange bias layers that fix the magnetization directions of the second and fourth ferromagnetic films. The magnetoresistive sensor according to claim 1 or 2, further comprising the insulating layer (insulating exchange bias layer). 8. The magnetoresistive sensor according to claim 7, wherein the insulating exchange bias layer is made of a nickel monoxide antiferromagnetic material. 9. The insulating exchange bias layer has a magnetization direction fixed between one of the second and fourth ferromagnetic layers and the insulating exchange bias layer. 8. The magnetoresistive sensor according to claim 7, further comprising a fifth ferromagnetic layer having an antiferromagnetic coupling film formed of a nonmagnetic metal thin film.