JPH11195824A - Magnetoresistance effect element and magnetoresistance effect type head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetoresistance element which is high in sensitivity, responds with excellent inearity to an external signal magnetic field. SOLUTION: A magnetoresistance effect element is constituted of a first ferromagnetic layer 1 and a second layer 3 adjoining each other through a first nonmagnetic layer 2, and a third ferromagnetic layer adjoining to the second ferromagnetic layer 3 through a second nonmagnetic layer 4, and this prevents a magnetic flux from reaching the first ferromagnetic layer, by closing the leaked magnetic flux generated from the end face of the second ferromagnetic layer 3, between itself and the third ferromagnetic layer 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-sensitivity magnetic sensor and a magnetoresistive element used for a magnetic head compatible with ultra-high density recording.

[0002]

2. Description of the Related Art In recent years, with the increase in density of magnetic recording, demand for magnetic heads and magnetic sensors with high sensitivity and high output has increased, and the development of magnetoresistive elements has been actively pursued. A magnetoresistive element is an element whose resistance changes in accordance with an external signal magnetic field. For example, a magnetic sensor and a magnetic head using an anisotropic magnetoresistance effect of a NiFe thin film have been put to practical use.

[0003] To obtain a sensor and head with higher sensitivity and higher output, a magnetoresistive element having a larger change in resistivity is required. Recently, a phenomenon called giant magnetoresistance effect has been discovered. The first thing that was discovered was an artificial lattice type magnetoresistive element in which a magnetic thin film was laminated via a metal nonmagnetic thin film, compared with a conventional magnetoresistive element having a resistance change rate of 2-3%. The resistance change rate was several tens%. However, although the artificial lattice type magnetoresistive element has a large resistance change rate, it requires a large external magnetic field of several kOe, and thus has not been practically used as a magnetic sensor or a magnetic head.

[0004] Subsequently, a magnetoresistive element called a spin valve type exhibiting a large resistance change rate even with a small external magnetic field was developed. FIG. 2 is a sectional view showing the structure of this spin valve type magnetoresistive element disclosed in Japanese Patent Application Laid-Open No. 6-60336, in which a first ferromagnetic thin film layer 21 and a non-magnetic metal material A thin film layer 22, a second ferromagnetic thin film layer 23, and a thin film layer 24 of an exchange bias material are stacked. The magnetization 25 of the first ferromagnetic thin film layer 21 is freely rotated according to the external signal magnetic field h. Second ferromagnetic thin film 2
3 is in a state where the magnetization 26 is fixed by exchange coupling with the adjacent antiferromagnetic film 24. Upon receiving an external signal magnetic field, the magnetization 25 of the first ferromagnetic thin film layer 21 rotates, and the magnetization 26 of the pinned second ferromagnetic thin film layer 23
And the angle changes. The cosine cos θ of the angle difference θ of this magnetization
The magnetic resistance changes in proportion to. Usually, the external signal magnetic field h
Makes a small change in the vicinity of 0, and the first ferromagnetic thin film layer 21 and the second ferromagnetic The magnetization of the thin film layer 23 is magnetized so as to be orthogonal.

However, according to the technique disclosed in Japanese Patent Application Laid-Open No. 6-60336, a part of the leakage magnetic flux generated from the magnetic pole formed on the end face of the pinned second ferromagnetic thin film layer 23 is reduced to the first ferromagnetic thin film layer. 21, the magnetic flux affects the first ferromagnetic thin-film layer 21, and there is a problem that the linearity of a change in magnetoresistance with respect to an external signal magnetic field is impaired or the measurement sensitivity is reduced. The problem of the leakage magnetic flux is not so large as the length of the magnetization direction (element height) of the second ferromagnetic thin film layer 23 is longer, but becomes more problematic as the length is shorter and the magnetic poles are closer. Therefore, the problem of the leakage magnetic flux becomes more serious as the magnetoresistance effect element becomes smaller.

[0006] The technology that has developed this is disclosed in Japanese Patent Publication No. 7-509.
No. 811. Fig. 3 is a table of Japanese Patent Translation
It is sectional drawing which shows the structure of the magnetoresistive effect element disclosed by JP-A-9811. The measurement layer 32 magnetized on the layer surface is adjacent to the bias layer 36 with the intermediate layer 34 interposed therebetween. As the magnetization M _B of the bias layer 36 is parallel to the anti-magnetization M _AF magnet layer 30, bias layer 36 bonding layer 38
And anti-ferromagnetic exchange coupling with the magnet layer 30 via Therefore, the magnetic flux generated from the bias layer 36
It is said that it is possible to close between the magnetic layer and the magnet layer 30 to prevent the measurement layer 32 from being affected. Tokiohei 5-5
No. 09811, the specific materials of the coupling layer 38 and the magnet layer 30 are not specified, but it is described that these layers are all made of a conductive material.

[0007]

However, in such a configuration, the interlayer coupling between the bias layer 36 and the magnet layer 30 becomes antiferromagnetic exchange coupling with respect to a change in the thickness of the coupling layer 38 of less than nm. It is known to exhibit a so-called RKKY oscillation that repeats the ferromagnetic exchange coupling.
Therefore, in order to perform antiferromagnetic exchange coupling between the bias layer 36 and the magnet layer 30, it is necessary to control the thickness of the coupling layer 38 very strictly. Also, the phenomenon that the two ferromagnetic layers are antiferromagnetically exchange-coupled (or ferromagnetically exchange-coupled) via the nonmagnetic layer is caused by the fact that the material of the nonmagnetic layer is Cu, Au, A
It was confirmed only in some cases such as g and Cr, but not for all metals.

Further, a current also flows through the coupling layer and the magnet layer. The change in magnetoresistance is caused by the way electrons are scattered at the interface between the measurement layer and the intermediate layer and at the interface between the bias layer and the intermediate layer depending on the direction of electron spin. Therefore, the current flowing through the coupling layer and the magnet layer is a so-called shunt current that does not contribute to the magnetoresistance effect, and has a problem that the effective resistance change rate is reduced and the sensitivity and SN ratio of the magnetoresistance effect element are reduced. The present invention has been made in view of the above problems, and has as its object to provide a highly sensitive magnetoresistive element that responds with good linearity to an external signal magnetic field.

[0009]

Means for Solving the Problems A first invention for solving the above-mentioned problems is a first invention in which a first nonmagnetic layer is disposed adjacent to a first nonmagnetic layer.
A second ferromagnetic layer, a second ferromagnetic layer, and a third ferromagnetic layer adjacent to the second ferromagnetic layer via a second non-magnetic layer. The axis and the easy axis of magnetization of the second ferromagnetic layer are substantially orthogonal to each other, and the second ferromagnetic layer and the third ferromagnetic layer are magnetostatically coupled to each other, so that the magnetization of the second ferromagnetic layer is Are fixed.

According to a second aspect of the present invention, there is provided a magnetoresistive element having an antiferromagnetic layer adjacent to the third ferromagnetic layer of the magnetoresistive element of the first aspect.

A feature of the second invention is that the magnetization of the third ferromagnetic layer is fixed by exchange coupling with the antiferromagnetic layer.
Is to fix the magnetization of the second ferromagnetic layer by magnetostatic coupling between the second ferromagnetic layer and the second ferromagnetic layer.

In the first and second aspects of the present invention, the second nonmagnetic layer preferably has a specific resistance of at least 20 μΩ · cm, and more preferably is an insulator. Here, the insulator refers to a substance having a very large specific resistance, such as a metal oxide or a metal nitride. As the insulator, silicon oxide, alumina, silicon nitride, or the like is preferable because a favorable thin film can be obtained. If the layer thickness is too thin, pinholes are likely to occur, and if it is too thick, the second ferromagnetic layer is more likely to be magnetostatically coupled to the first ferromagnetic layer than the third ferromagnetic layer. Preferably, there is.

Preferably, the second ferromagnetic layer and the third ferromagnetic layer have the same material and the same layer thickness.

Next, a third invention relates to a first ferromagnetic layer and a second ferromagnetic layer adjacent via a first nonmagnetic layer, and an antiferromagnetic layer adjacent to the second ferromagnetic layer. And the second in the antiferromagnetic layer
A third ferromagnetic layer adjacent via a non-magnetic layer of
The easy axis of magnetization of the first ferromagnetic layer and the easy axis of magnetization of the second ferromagnetic layer are substantially orthogonal to each other, and the magnetization of the second ferromagnetic layer is fixed by the antiferromagnetic layer. The magnetoresistance effect element is characterized in that the magnetization of the ferromagnetic layer is substantially antiparallel to the magnetization of the second ferromagnetic layer.

Preferably, the specific resistance of the second nonmagnetic layer is at least 20 μΩ · cm or more, and more preferably, it is an insulator. Here, the insulator refers to a substance having a very large specific resistance, such as a metal oxide or a metal nitride. As the insulator, silicon oxide, alumina, silicon nitride, or the like is preferable because a favorable thin film can be obtained. If the layer thickness is too thin, pinholes are likely to occur, and if it is too thick, the second ferromagnetic layer is more likely to be magnetostatically coupled to the first ferromagnetic layer than the third ferromagnetic layer. Preferably, there is.

Compared with the first and second inventions, there is an antiferromagnetic layer between them, and the distance between the second and third ferromagnetic layers is farther apart. A feature of the third invention is that exchange coupling with the antiferromagnetic layer is used for fixing the magnetization of the second ferromagnetic layer.

The first to third inventions are effective when the length of the second ferromagnetic layer in the direction of magnetization is 1 μm or less, particularly 0.5 μm or less. This is because the smaller the length of the magnetization direction, the closer the magnetic pole generated to the end face of the second ferromagnetic layer.

Next, the magnetoresistive head of the present invention has a structure in which the magnetoresistive element having the above structure is sandwiched between shields made of a soft magnetic material.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetoresistive element and a magnetoresistive head according to the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing the structure of a magnetoresistive element according to a first embodiment of the present invention. A structure in which a third ferromagnetic layer 5, a second nonmagnetic layer 4, a second ferromagnetic layer 3, a first nonmagnetic layer 2, and a first ferromagnetic layer 1 are stacked on a substrate 6 is formed. ing.

The substrate 6 is made of a non-magnetic material such as glass, silicon, a sintered body of Al ₂ O ₃ and TiC, and has good surface flatness. The first ferromagnetic layer 1 has a sufficiently small coercive force so that the magnetization can be rotated with respect to a small external signal magnetic field.
So-called soft magnetic materials are suitable. For example, a nickel-iron alloy or a nickel-iron-cobalt alloy can be used. The thickness of the first ferromagnetic layer 1 is 1 nm or more and 10 nm
The following is good. When the film thickness is large, the MR ratio is reduced due to the shunt effect, but when it is too small, the soft magnetic characteristics deteriorate.

The first non-magnetic layer 2 has a role of minimizing exchange coupling between the first ferromagnetic layer 1 and the second ferromagnetic layer 3 to minimize Cu, Ag, Au, Ru and the like. Although Cu can be used, Cu is most suitable. The thickness of the nonmagnetic layer is at least 1.5 nm or more, preferably 1.8 nm or more in order to reduce exchange coupling. However, if the thickness is too large, the shunt effect lowers the MR ratio, so the thickness is set to 10 nm or less, preferably 3 nm or less.

The first ferromagnetic layer 1, the second ferromagnetic layer 3, and the third ferromagnetic layer 5 are each magnetized in the layer plane. The magnetization directions of the first ferromagnetic layer 1 and the second ferromagnetic layer 3 are substantially orthogonal to each other in the absence of an external magnetic field, and the magnetization directions of the second ferromagnetic layer 3 and the third ferromagnetic layer 5 Are almost anti-parallel. This can be achieved, for example, by forming a magnetic layer while applying an external magnetic field in a direction in which the magnetic layer is to be magnetized. If the magnetizations of the second ferromagnetic layer 3 and the third ferromagnetic layer 5 are substantially antiparallel, the second ferromagnetic layer 3
Leakage magnetic flux from the first ferromagnetic layer 5 is closed through the third ferromagnetic layer 5, and leakage magnetic flux can be prevented from closing through the first ferromagnetic layer 1. The magnetization of the second ferromagnetic layer 3 must be pinned to an external magnetic field,
This is achieved by magnetostatic coupling between the second ferromagnetic layer 3 and the third ferromagnetic layer 5. Fe is used as the second ferromagnetic layer 3
Ni, Co, FeNiCo and the like are preferable. 1 nm or more in thickness1
0 nm or less is preferable. The third ferromagnetic layer 5 preferably has a higher coercive force than the first ferromagnetic layer so that the magnetization is not rotated by an external magnetic field. For example, a Co, CoFe alloy, CoPt alloy, or the like is preferable.

For controlling the magnetization direction, annealing may be performed in a magnetic field after forming the film in a non-magnetic field.

If the third ferromagnetic layer 5 or the second ferromagnetic layer 3 is saturated with magnetic flux, there is a possibility that a part of the leakage magnetic flux reaches the first ferromagnetic layer 1. come. Therefore, the saturation magnetic flux density and the film thickness of the second ferromagnetic layer 3 and the third ferromagnetic layer 5 must be set to appropriate values. More preferred are the materials of the third ferromagnetic layer 5 and the second ferromagnetic layer 3,
That is, the film thicknesses are matched. In such a case, the magnetic flux generated from each magnetic layer is considered to be substantially the same, so that the design becomes easy.

The second nonmagnetic layer 4 has a role of preventing the second ferromagnetic layer 3 and the third ferromagnetic layer 5 from being exchange-coupled and their magnetization directions becoming parallel. Second conductive non-magnetic layer
When the ferromagnetic layer 3 and the third ferromagnetic layer 5 are subjected to antiferromagnetic exchange coupling to make the magnetization directions antiparallel, it is necessary to strictly control the thickness of the nonmagnetic layer. Since the purpose of the second nonmagnetic layer 4 is to reduce the exchange coupling between the second ferromagnetic layer 3 and the third ferromagnetic layer 5, the film thickness control does not have to be performed so strictly. The second non-magnetic layer preferably has a higher specific resistance from the viewpoint of reducing the shunt current. For example, it is preferably 20 μΩ · cm or more, and more preferably an insulator. An insulator is also preferable from the viewpoint of cutting off exchange coupling. As the insulator, silicon oxide, alumina, silicon nitride, or the like is preferable because a favorable thin film can be obtained.
If the film thickness is too small, a pinhole is formed, so that the thickness is preferably 1 nm or more. However, if the film thickness is too large, the second ferromagnetic layer 3 is more static than the third ferromagnetic layer 5. 20 nm or less is preferable because magnetic coupling occurs. More preferably, the thickness is equal to or less than the thickness of the first nonmagnetic layer 2.

In order to reduce the shunt current, the specific resistance of the third ferromagnetic layer 5 is preferably as high as possible.

The respective magnetic layers and non-magnetic layers can be formed by a sputtering method or the like. Although not shown in FIG. 1, a lead layer for passing a current to the magnetoresistance effect element may be provided. As the lead layer, a metal having a low specific resistance such as Au or Cu is used.

In FIG. 1, the third ferromagnetic layer 5, the second nonmagnetic layer 4, the second ferromagnetic layer 3, the first nonmagnetic layer 2, the first ferromagnetic layer It was laminated with layer 1, but on the contrary
, A first nonmagnetic layer 2, a second ferromagnetic layer 3,
The second nonmagnetic layer 4 and the third ferromagnetic layer 5 may be stacked in this order.

FIG. 7 is a sectional view showing the structure of a magnetoresistive element according to a second embodiment of the present invention. An antiferromagnetic layer 76, a third ferromagnetic layer 75, a second nonmagnetic layer 74, a second ferromagnetic layer 73, a first nonmagnetic layer 72, and a first ferromagnetic layer 71 are formed on a substrate 77. It has a laminated structure.

Glass, silicon, Al ₂ O ₃
And a non-magnetic material such as a sintered body of TiC with good surface flatness is used. The first ferromagnetic layer 71 is preferably made of a so-called soft magnetic material having a sufficiently small coercive force so that the magnetization can be rotated by a small external signal magnetic field. For example, NiFe or Ni
FeCo or the like can be used. The thickness of the first ferromagnetic layer 71 is preferably 1 nm or more and 10 nm or less. When the film thickness is large, the MR ratio is reduced due to the shunt effect, but when it is too small, the soft magnetic characteristics deteriorate.

The first nonmagnetic layer 72 is a first ferromagnetic layer 71
It serves to minimize the exchange coupling between the second ferromagnetic layer 73 and Cu, Ag, Au, Ru, etc., but Cu is most suitable. The thickness of the non-magnetic layer should be at least 1.5 n in order to reduce exchange coupling.
m or more, preferably 1.8 nm or more. However, if the thickness is too large, the shunt effect lowers the MR ratio, so the thickness is set to 10 nm or less, preferably 3 nm or less.

First ferromagnetic layer 71, second ferromagnetic layer 7
The third and third ferromagnetic layers 75 are each magnetized in the layer plane. The magnetization directions of the first ferromagnetic layer 71 and the second ferromagnetic layer 73 are orthogonal to each other without application of an external magnetic field,
The magnetization directions of the ferromagnetic layer 73 and the third ferromagnetic layer 75 are set to be approximately antiparallel. This can be achieved, for example, by forming a magnetic layer while applying an external magnetic field in a direction in which the magnetic layer is to be magnetized. If the magnetizations of the second ferromagnetic layer 73 and the third ferromagnetic layer 75 are substantially anti-parallel, the leakage magnetic flux from the second ferromagnetic layer 73 closes via the third ferromagnetic layer 75. , The leakage magnetic flux is reduced to the first ferromagnetic layer 71.
Closing can be prevented. The magnetization direction may be controlled by performing annealing in a magnetic field after forming the film in a non-magnetic field.

The second ferromagnetic layer 73 is preferably made of iron / nickel alloy, cobalt, iron / nickel / cobalt alloy, or the like. The thickness is preferably 1 nm or more and 10 nm or less. Further, since the magnetization of the third ferromagnetic layer 75 is pinned by the antiferromagnetic layer 76, the coercive force of the third ferromagnetic layer 75 may be small, and the material selection range is wider than that of the first embodiment. For example, iron-nickel alloy, cobalt, iron-nickel-cobalt alloy, cobalt-platinum alloy, and the like are preferable. The thickness is preferably 1 nm or more and 10 nm or less.

The antiferromagnetic layer 76 is the third ferromagnetic layer 75
And the magnetization of the third ferromagnetic layer 75 is pinned to an external magnetic field. Further, the third ferromagnetic layer 75 and the second ferromagnetic layer 73 are magnetostatically coupled, so that the second ferromagnetic layer is pinned against an external magnetic field. The feature of this embodiment is that the magnetization of the third ferromagnetic layer 75 is
Is to pin. Examples of the material of the antiferromagnetic layer 76 include an iridium-manganese alloy, an iron-manganese alloy, a nickel-manganese alloy, and platinum-palladium.
Manganese alloys, nickel oxide, cobalt oxide, α-Fe ₂ O _{3 and the} like are preferred. From the viewpoint of reducing the shunt current, an oxide antiferromagnetic material such as nickel oxide, cobalt oxide, and α-Fe ₂ O ₃ is preferable. The layer thickness is preferably from 10 nm to 50 nm.

If the third ferromagnetic layer 75 or the second ferromagnetic layer 73 is saturated with magnetic flux, there is a possibility that a part of the leakage magnetic flux reaches the first ferromagnetic layer 71. come.
Therefore, the second ferromagnetic layer 73 and the third ferromagnetic layer 7
The saturation magnetic flux density and film thickness of No. 5 must be set to appropriate values. More preferably, the materials and thicknesses of the third ferromagnetic layer 75 and the second ferromagnetic layer 73 are made equal. In such a case, the magnetic flux generated from each magnetic layer is considered to be substantially the same, so that the design becomes easy.

The second non-magnetic layer 74 is the second ferromagnetic layer 73
And the third ferromagnetic layer 75 exchange-couples to prevent the magnetization directions from becoming parallel. When the second ferromagnetic layer 73 and the third ferromagnetic layer 75 are anti-ferromagnetic exchange-coupled by a conductive non-magnetic layer to make their magnetization directions anti-parallel, the thickness of the non-magnetic layer is strictly controlled. The second aspect of the present invention
Since the purpose of the non-magnetic layer 74 is to reduce the exchange coupling between the second ferromagnetic layer 73 and the third ferromagnetic layer 75, the film thickness control does not have to be performed so strictly. Second non-magnetic layer 7
As for 4, it is desirable that the specific resistance is higher from the viewpoint of reducing the shunt current. For example, it is preferably 20 μΩ · cm or more, and more preferably an insulator. An insulator is also preferable from the viewpoint of cutting off exchange coupling. As the insulator, silicon oxide, alumina, silicon nitride, or the like is preferable because a favorable thin film can be obtained. When the film thickness is too small, a pinhole is formed, so that the thickness is preferably 1 nm or more. However, when the film thickness is too large, the second ferromagnetic layer 73 is more static than the third ferromagnetic layer 75. 20 nm or less is preferable because magnetic coupling occurs. More preferably, the thickness is equal to or less than the thickness of the first nonmagnetic layer 72.

In order to reduce the shunt current, the specific resistance of the third ferromagnetic layer 75 is preferably as high as possible.

Each of the magnetic layer and the non-magnetic layer can be formed by a sputtering method or the like. Although not shown in FIG. 7, a lead layer for flowing a current to the magnetoresistance effect element may be provided. As the lead layer, a metal having a low specific resistance such as Au or Cu is used.

FIG. 8 is a sectional view showing the structure of a magnetoresistive element according to a third embodiment of the present invention. On a substrate 87, a third ferromagnetic layer 86, a second nonmagnetic layer 85, an antiferromagnetic layer 84, a second ferromagnetic layer 83, a first nonmagnetic layer 82, and a first ferromagnetic layer 81 are provided. It has a laminated structure.

The substrate 87 is made of glass, silicon, Al ₂ O ₃
And a non-magnetic material such as a sintered body of TiC with good surface flatness is used. For the first ferromagnetic layer 81, a so-called soft magnetic material having a sufficiently small coercive force is suitable so that the magnetization can be rotated by a small external signal magnetic field. For example, NiFe or Ni
FeCo or the like can be used. The thickness of the first ferromagnetic layer 81 is preferably 1 nm or more and 10 nm or less. When the film thickness is large, the MR ratio is reduced due to the shunt effect, but when it is too small, the soft magnetic characteristics deteriorate.

The first non-magnetic layer 82 is the first ferromagnetic layer 81
It serves to minimize the exchange coupling between the second ferromagnetic layer 83 and Cu, Ag, Au, Ru, etc., but Cu is most suitable. The thickness of the non-magnetic layer should be at least 1.5 n in order to reduce exchange coupling.
m or more, preferably 1.8 nm or more. However, if the thickness is too large, the shunt effect lowers the MR ratio, so the thickness is set to 10 nm or less, preferably 3 nm or less.

The first ferromagnetic layer 81 and the second ferromagnetic layer 8
The third and third ferromagnetic layers 86 are each magnetized in the layer plane. The magnetization directions of the first ferromagnetic layer 81 and the second ferromagnetic layer 83 are substantially orthogonal to each other in the absence of an external magnetic field,
The magnetization directions of the second ferromagnetic layer 83 and the third ferromagnetic layer 86 are substantially antiparallel. This can be achieved, for example, by forming a magnetic layer while applying an external magnetic field in a direction in which the magnetic layer is to be magnetized. Second ferromagnetic layer 8
If the magnetizations of the third ferromagnetic layer 86 and the third ferromagnetic layer 86 are substantially antiparallel, the leakage magnetic flux from the second ferromagnetic layer 83
, And the leakage magnetic flux can be prevented from closing through the first ferromagnetic layer 81.

However, since the antiferromagnetic layer 84 is interposed therebetween, the third ferromagnetic layer 86 is farther from the second ferromagnetic layer than the first ferromagnetic layer 81, The effect of preventing the leakage magnetic flux generated from the second ferromagnetic layer from reaching the first ferromagnetic layer 81 is smaller than that of the embodiment. However, if the thickness of the antiferromagnetic layer 84 is appropriately reduced, a part of the leakage magnetic flux is closed through the third ferromagnetic layer, so that there is an effect of reducing the leakage magnetic flux reaching the first ferromagnetic layer 81. The feature of this embodiment resides in that the magnetization of the second ferromagnetic layer is effectively pinned by exchange coupling with the antiferromagnetic layer.

The magnetization direction may be controlled by forming a film in a non-magnetic field and then performing annealing in a magnetic field.

The magnetization of the second ferromagnetic layer 83 must be pinned to an external magnetic field.
By the exchange coupling between the ferromagnetic layer 83 and the antiferromagnetic layer 84. Since the magnetization of the second ferromagnetic layer 83 is pinned by the antiferromagnetic layer, the coercive force of the second ferromagnetic layer 83 may be small, and the material selection range is wider than in the first embodiment. For example, iron-nickel alloy, cobalt, iron-nickel-cobalt alloy, cobalt-platinum alloy, and the like are preferable. The thickness is preferably 1 nm or more and 10 nm or less. The third ferromagnetic layer 86 is preferably made of iron / nickel alloy, cobalt, iron / nickel / cobalt alloy, cobalt / platinum alloy, or the like. The thickness is preferably 1 nm or more and 10 nm or less.

The antiferromagnetic layer 84 is exchange-coupled with the second ferromagnetic layer 83, and pins the magnetization of the second ferromagnetic layer 83 to an external magnetic field. As a material of the antiferromagnetic layer 84, for example, an iridium-manganese alloy, an iron-manganese alloy, a nickel-manganese alloy, a platinum-palladium-manganese alloy, nickel oxide, cobalt oxide, α-Fe ₂ O _{3 and the} like are preferable. From the viewpoint of reducing the shunt current, an oxide antiferromagnetic material such as nickel oxide, cobalt oxide, and α-Fe ₂ O ₃ is preferable.
The layer thickness is preferably from 10 nm to 50 nm.

The second nonmagnetic layer 85 is a third ferromagnetic layer 86
Are provided for preventing exchange coupling with the antiferromagnetic layer 84 and preventing the magnetization direction thereof from becoming parallel to the second ferromagnetic layer 83.
The second non-magnetic layer preferably has a higher specific resistance from the viewpoint of reducing the shunt current. For example, 20μΩcm
The above is desirable, and more preferably an insulator. An insulator is also desirable from the viewpoint of breaking exchange coupling. As the insulator, silicon oxide, alumina, silicon nitride, or the like is preferable because a favorable thin film can be obtained. When the film thickness is too small, pinholes are formed, so that the thickness is preferably 1 nm or more.

In order to reduce the shunt current, the specific resistance of the third ferromagnetic layer 86 is preferably as high as possible.

Each of the magnetic layer and the non-magnetic layer can be formed by a sputtering method or the like. Although not shown in FIG. 8, a lead layer for flowing a current to the magnetoresistive element may be provided. As the lead layer, a metal having a low specific resistance such as Au or Cu is used.

In FIG. 8, the third ferromagnetic layer 86, the second nonmagnetic layer 85, the antiferromagnetic layer 84, the second ferromagnetic layer 83, and the first nonmagnetic layer 82 , The first ferromagnetic layer 81, the first nonmagnetic layer 82, the second ferromagnetic layer 83, the antiferromagnetic layer 84,
The second nonmagnetic layer 85 and the third ferromagnetic layer 86 may be stacked in this order.

FIG. 4 is a sectional view showing the structure of a thin-film magnetic head according to a fourth embodiment of the present invention. The magnetoresistive element 41 is connected to the shield gap layers 44 and 45 and the shield 4.
The structure is sandwiched between 2, 43. 47 is an electrode layer for passing a sense current to the magnetoresistive element;
Reference numeral 6 denotes a hard bias layer for converting the first ferromagnetic layer of the magnetoresistance effect element into a single magnetic domain. As a material for the shields 42 and 43, a magnetic material having soft magnetic properties such as NiFe is suitable, and for the shield gap layers 44 and 45, a material such as alumina is suitable. As the electrode layer 47, Au or
A metal having a low specific resistance such as Cu is suitable, and a permanent magnet film such as CoPt is suitable for the hard bias layer 46.

[0053]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetoresistive element and a magnetoresistive head according to the present invention will be described below using specific examples.

Example 1 Two types of magnetoresistive elements A and B as shown in Table 1 were prepared using a high-frequency magnetron sputtering apparatus.

[0055]

[Table 1]

A magnetoresistive element A as a comparative example was prepared as follows. The Si (100) substrate was set in a high-frequency magnetron sputtering apparatus, and a Co film was formed to a thickness of 5 nm while applying a magnetic field with a SmCo permanent magnet. Next, Cu
Was formed into a 2 nm film. Further, a Ni-Fe film was formed to a thickness of 3 nm while applying a magnetic field substantially orthogonal to that at the time of forming the Co film. Here, Ni-Fe is a film obtained by sputtering a target of Ni _0.8 Fe _0.2 . The element thus obtained was subjected to miniaturization and patterning of a lead layer made of Au as shown in FIG. 5 by using a known photolithography technique. A current lead layer 52 for flowing a current is connected to both ends of the magnetoresistive element 51, and a voltage lead layer 53 for measuring a voltage is connected to an intermediate portion. L is 1 μm and h is 0.5 μm. External magnetic field H
54 was applied and the MR curve was measured by the four-terminal method. FIG. 6 shows the results. MR [%] in the figure is (R-Rmin) / Rmin × 100
[%]. R is the resistance of the element in the magnetic field, and Rmin is the resistance of the element in a magnetic field of 50 Oe.
The applied magnetic field was set to be orthogonal to the magnetization direction of Ni-Fe in the in-plane direction of the magnetoresistive element. Further, the sense current is made to be orthogonal to the sense current flowing through the magnetoresistive element.

The magnetoresistance effect element B according to the embodiment of the present invention
Was created as follows. The Si (100) substrate was set in a high-frequency magnetron sputtering apparatus, and a Co film was formed to a thickness of 5 nm while applying a magnetic field with a SmCo permanent magnet. Next, 2 nm of SiO ₂ was formed in the same apparatus. Thereafter, Co was deposited to a thickness of 5 nm while the applied magnetic field by the permanent magnet was changed by 180 degrees as before. Further, Cu was deposited to a thickness of 2 nm. Finally, NiFe was deposited to a thickness of 3 nm while applying a magnetic field by a permanent magnet in a direction substantially perpendicular to the time when the Co was deposited. Element B thus obtained
Was subjected to miniaturization and patterning of the lead layer in the same manner as in the device A, and the MR curve was measured. FIG. 6 shows the results. FIG.
As is clear from the above, in element A, the MR curve has the horizontal axis (magnetic field).
In the element B, there is almost no shift and a linear resistance change is obtained before and after the zero magnetic field. Comparative Example A had no antiferromagnetic layer. However, IrMn was formed as an antiferromagnetic layer on a Si substrate to a thickness of 8 nm, and Si / IrMn (8 nm) / Co was used.
In the case of (5 nm) / Cu (2 nm) / Ni-Fe (3 nm), the pinning effect of the Co layer was good, but the nonlinear change of the MR curve before and after the zero magnetic field was almost the same as that of the element A. Was.

Although the high-frequency magnetron sputtering method is used in this embodiment, the film may be formed by using a direct current magnetron sputtering method or an ion beam sputtering method.

[0059] (Example 2) magnetoresistive element A of Example 1, to constitute a thin-film magnetic heads H _A and H _B having a structure as shown in FIG. 4 using a magnetoresistance effect element having the same structure as B The properties were evaluated. However, the magnetoresistive element was formed directly on the shield gap layer, not on the Si substrate. Al ₂ O ₃ was used for the shield gap layers 43 and 44, a Co—Pt alloy was used for the hard bias layer 45, and Au was used for the lead layer 44. When a sinusoidal signal magnetic field of about 20 Oep-p was applied to these heads, only a non-linearly distorted output was obtained for H _A with respect to the signal magnetic field, but a sinusoidal output was obtained for H _B with the signal magnetic field applied. The response was linear.

Example 3 Two types of magnetoresistive elements C and D as shown in Table 2 were prepared using a high-frequency magnetron sputtering apparatus.

[0061]

[Table 2]

A magnetoresistive element C as a comparative example was prepared as follows. The Si (100) substrate was placed in a high-frequency magnetron sputtering apparatus, and IrMn was deposited to a thickness of 20 nm while applying a magnetic field with a SmCo permanent magnet. Subsequently, a Co film was formed to a thickness of 5 nm while applying a magnetic field. Next, Cu was deposited to a thickness of 2 nm in the same apparatus. Further, a Ni-Fe film was formed to a thickness of 3 nm while applying a magnetic field substantially orthogonal to that at the time of forming the Co film. Where Ni-Fe
And I wrote in What is a film obtained by sputtering the target of Ni _{0 .8} Fe _0.2.

The magnetoresistance effect element D according to the embodiment of the present invention
Was created as follows. The Si (100) substrate was placed in a high-frequency magnetron sputtering apparatus, and IrMn was deposited to a thickness of 20 nm while applying a magnetic field with a SmCo permanent magnet. Subsequently, a Co film was formed to a thickness of 5 nm while applying a magnetic field. Further, SiO ₂ was deposited to a thickness of 1 nm. Thereafter, Co was deposited to a thickness of 5 nm while the applied magnetic field by the permanent magnet was changed by 180 degrees as before. Further, Cu was deposited to a thickness of 2 nm.
Finally, NiFe was deposited to a thickness of 3 nm while applying a magnetic field by a permanent magnet in a direction substantially perpendicular to the time when the Co was deposited.
The devices C and D were patterned in the same manner as in Example 1, and the MR curve was measured by a four-terminal method. FIG. 9 shows the results. As is clear from FIG. 9, in the element C, the MR curve is largely shifted in the horizontal axis (magnetic field) direction, and the resistance changes nonlinearly before and after the zero magnetic field. A linear resistance change before and after the magnetic field is obtained. Further, when a larger magnetic field is applied, the magnetization of the second ferromagnetic layer is reversed. However, in the present embodiment, the magnetization is not reversed unless a larger magnetic field is applied than in the first embodiment.

Although the high-frequency magnetron sputtering method is used in this embodiment, the film may be formed by using a direct current magnetron sputtering method or an ion beam sputtering method.

(Embodiment 4) Embodiment 2 using a magnetoresistive element having the same configuration as the magnetoresistive elements C and D of Embodiment 3
The thin film magnetic heads H _C and H _D were constructed in the same manner as described above, and the characteristics were evaluated. When a sinusoidal signal magnetic field of about 20 Oep-p was applied, H _C provided only a non-linearly distorted output with respect to the signal magnetic field, but H _D provided a sinusoidal output and was linear with respect to the signal magnetic field. Response.

Example 5 Two types of magnetoresistance effect elements E and F as shown in Table 1 were prepared using a high-frequency magnetron sputtering apparatus.

[0067]

[Table 3]

A magnetoresistive element E as a comparative example was prepared as follows. The Si (100) substrate was placed in a high-frequency magnetron sputtering apparatus, and IrMn was deposited to a thickness of 20 nm while applying a magnetic field with a SmCo permanent magnet. Subsequently, a Co film was formed to a thickness of 5 nm while applying a magnetic field. Next, Cu was deposited to a thickness of 2 nm in the same apparatus. Further, a Ni-Fe film was formed to a thickness of 3 nm while applying a magnetic field substantially orthogonal to that at the time of forming the Co film. Where Ni-Fe
And I wrote in What is a film obtained by sputtering the target of Ni _{0 .8} Fe _0.2.

The magnetoresistance effect element F according to the embodiment of the present invention
Was created as follows. The Si (100) substrate was set in a high-frequency magnetron sputtering apparatus, and a Co film was formed to a thickness of 5 nm while applying a magnetic field with a SmCo permanent magnet. Continue with 1 nm of SiO ₂
After forming the film, the applied magnetic field by the permanent magnet was
IrMn was deposited to a thickness of 20 nm while being changed by 0 degrees. Subsequently, a Co film was formed to a thickness of 5 nm while applying a magnetic field. Further, Cu was deposited to a thickness of 2 nm. Finally, NiFe was deposited to a thickness of 3 nm while applying a magnetic field by a permanent magnet in a direction orthogonal to the time when the Co was deposited.

The devices E and F were patterned in the same manner as in Example 1, and the MR curve was measured by the four-terminal method. The results are shown in FIG. As is clear from FIG. 10, in the element E, the MR curve is largely shifted in the horizontal axis (magnetic field) direction, and the resistance changes nonlinearly around the zero magnetic field. However, a linear resistance change before and after the zero magnetic field is obtained. Further, when a larger magnetic field is applied, the magnetization of the second ferromagnetic layer is reversed. However, in the present embodiment, the magnetization is not reversed unless a larger magnetic field is applied than in the first embodiment.

Although the high-frequency magnetron sputtering method is used in this embodiment, the film may be formed by using a direct current magnetron sputtering method or an ion beam sputtering method.

(Embodiment 6) Embodiment 2 using a magnetoresistive element having the same configuration as the magnetoresistive elements E and F of Embodiment 5
Just as to constitute a thin-film magnetic heads H _E and H _F and their characteristics were evaluated. About 10Oep-p H _E was applied sine wave signal magnetic field is was only non-linear distorted output to the signal magnetic field, linearly with respect to H _F is the signal magnetic field sine wave output is obtained Response.

[0073]

As described above, the magnetoresistive element of the present invention has a linear resistance change with respect to an applied magnetic field of around zero magnetic field as compared with the conventional magnetoresistive element. The effect type head has a linear output characteristic with respect to an applied magnetic field around zero magnetic field.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a first embodiment of a magnetoresistive element of the present invention.

FIG. 2 is an exploded view of a first example of a conventional magnetoresistance effect element.

FIG. 3 is a schematic cross-sectional view of a second example of a conventional magnetoresistive element.

FIG. 4 is a schematic cross-sectional view of a magnetoresistive head according to an embodiment of the present invention.

FIG. 5 is a schematic view of a lead layer for measuring the resistance of a magnetoresistive element by a four-terminal measurement method.

FIG. 6 is a diagram showing MR curves of one example and a comparative example of the magnetoresistive element of the present invention.

FIG. 7 is a schematic sectional view of a second embodiment of the magnetoresistive element of the present invention.

FIG. 8 is a schematic sectional view of a third embodiment of the magnetoresistive element of the present invention.

FIG. 9 is a diagram showing MR curves of a second example and a comparative example of the magnetoresistance effect element of the present invention.

FIG. 10 is a diagram showing MR curves of a third example and a comparative example of the magnetoresistance effect element of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st ferromagnetic layer 2 1st nonmagnetic layer 3 2nd ferromagnetic layer 4 2nd nonmagnetic layer 5 3rd ferromagnetic layer 6 Substrate 41 Magnetoresistive element 42, 43 Shield 44, 45 Shield Gap layer 46 Hard bias layer 47 Electrode layer 51 Magnetoresistive element 52 Current lead layer 53 Voltage lead layer 54 External magnetic field 61 MR curve of element B 62 MR curve of element A 71 First ferromagnetic layer 72 First nonmagnetic Layer 73 Second ferromagnetic layer 74 Second nonmagnetic layer 75 Third ferromagnetic layer 76 Antiferromagnetic layer 77 Substrate 81 First ferromagnetic layer 82 First nonmagnetic layer 83 Second ferromagnetic layer 84 antiferromagnetic layer 85 second nonmagnetic layer 86 third ferromagnetic layer 87 substrate

Claims (14)

[Claims] A first ferromagnetic layer and a second ferromagnetic layer adjacent to each other via a first nonmagnetic layer; and an adjacent to the second ferromagnetic layer via a second nonmagnetic layer. And the easy axis of magnetization of the first ferromagnetic layer and the easy axis of magnetization of the second ferromagnetic layer are substantially orthogonal to each other. A magnetoresistive element wherein the magnetization of the second ferromagnetic layer is fixed by magnetostatic coupling of the third ferromagnetic layer. 2. The magnetoresistive element according to claim 1, wherein an antiferromagnetic layer is adjacent to the third ferromagnetic layer. 3. The specific resistance of the second nonmagnetic layer is at least 20.
3. The method according to claim 1, wherein the resistance is not less than μΩ · cm.
3. The magnetoresistive effect element according to item 1. 4. The magnetoresistive element according to claim 3, wherein the second nonmagnetic layer is made of an insulator. 5. The magnetoresistive element according to claim 4, wherein the insulator is any one of silicon oxide, alumina, and silicon nitride. 6. The magnetoresistance effect element according to claim 1, wherein the thickness of the second nonmagnetic layer is 1 nm or more and 20 nm or less. 7. The method according to claim 1, wherein the second ferromagnetic layer and the third ferromagnetic layer have the same material and the same thickness.
7. The magnetoresistive element according to any one of items 1 to 6. 8. A first ferromagnetic layer and a second ferromagnetic layer adjacent via a first nonmagnetic layer, an antiferromagnetic layer adjacent to the second magnetic layer, and the antiferromagnetic layer. A third ferromagnetic layer adjacent to the layer with a second nonmagnetic layer interposed therebetween, wherein the easy axis of magnetization of the first ferromagnetic layer and the easy axis of magnetization of the second ferromagnetic layer are substantially orthogonal to each other. The magnetization of the second ferromagnetic layer is fixed by the antiferromagnetic layer, and the magnetization of the third ferromagnetic layer is substantially antiparallel to the magnetization of the second ferromagnetic layer. A magnetoresistive effect element. 9. The second nonmagnetic layer having a specific resistance of at least 20
9. The magnetoresistive element according to claim 8, wherein the resistance is at least μΩ · cm. 10. The magnetoresistive element according to claim 9, wherein the second nonmagnetic layer is made of an insulator. 11. The semiconductor device according to claim 1, wherein the insulator is any one of silicon oxide, alumina, and silicon nitride.
0. The magnetoresistive element according to item 0. 12. The thickness of the second nonmagnetic layer is 1 nm or more and 20 nm.
The magnetoresistive element according to claim 8, wherein: 13. The length of the second ferromagnetic layer in the magnetization direction is 1
The magnetoresistive element according to any one of claims 1 to 12, which has a thickness of not more than μm. 14. A magnetoresistive head in which the magnetoresistive element according to claim 1 is sandwiched between a pair of shields made of a soft magnetic material.