JPH11307840A - Magnetic field measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the size of connection strength between magnetic layers by using magnetic/non-magnetic multilayer films having irregularities in the boundaries of magnetic layers and non-magnetic layers. SOLUTION: Irregularities are given to an interface 41 between a magnetic layer 13 and a non-magnetic layer 11 and an interface 42 between the non- magnetic layer 11 and a magnetic layer 12 and a magnetic/non-magnetic multilayer film is formed in a spin bubble film for magnetic head. The size of the irregularities in the magnetic/non-magnetic multilayer film is varied in accordance with the material and the crystal orientation of the non-magnetic layer 11 and the degree of the reduction of connection strength. Namely, the thickness of the non-magnetic layer 11 is set to be the distribution of a (t-1) atom layer, t-atom layer and a (t+1) atom layer. The rate of the distribution is set to 0.25, 0.5 and 0.25 against the whole area of the interface 41 and the interface 42. Thus, the magnetic/non-magnetic multilayer film of high ability can be manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic field measuring apparatus using a giant magnetoresistance effect element.

[0002]

2. Description of the Related Art A giant magnetoresistive element, which is being considered for application to a magnetic field measuring device (for example, a magnetic head) for high density magnetic recording / reproducing, has a nonmagnetic layer between two magnetic layers. A sandwich-structured element called a sandwiched spin valve film is known, and is reported, for example, in Surface Technology, Vol. 48, No. 11, (1997), pp. 1059 to 1064.

In a typical spin valve film, as shown in FIG. 1, a nonmagnetic layer 11 is sandwiched between a magnetic layer 12 and a magnetic layer 13, and one of the magnetic layers 13 has an antiferromagnetic layer 14. Installed. In this spin valve film, one magnetic layer 13 is called a fixed layer because its magnetization 15 is fixed by an antiferromagnetic layer 14, and the other magnetic layer 12 has its magnetization 16 in the direction of an external magnetic field 17. It is called a free layer because it can be rotated to any angle. At this time, the electrical resistance in the plane of the spin valve film is
Depending on the relative directions of the magnetizations 15 and 16, the electric resistance in the film plane is minimum when they are parallel to each other and maximum when they are antiparallel. Therefore, the electrical resistance value in the film plane is a function of the angle between the magnetization 16 of the free layer and the magnetization 15 of the fixed layer, but the direction of the magnetization 16 of the free layer is determined by the external magnetic field 17.
The external magnetic field 17 can be detected by measuring the resistance of the spin valve film.

On the other hand, the magnetic layer 1 is formed on the spin valve film.
Since a magnetic interaction acts between the magnetic layer 2 and the magnetic layer 13 via the nonmagnetic layer 11, the magnetization 16 of the free layer is magnetically coupled to the magnetization 15 of the fixed layer. Therefore, the response sensitivity of the magnetization 16 of the free layer to changes in the external magnetic field 17 decreases as the coupling strength between the magnetic layers increases.

FIG. 2 shows the dependence of the magnetic coupling strength on the thickness of the nonmagnetic layer. This is data when Au (111) single crystal is used for the nonmagnetic layer. From FIG. 2, the magnetic coupling strength attenuates while vibrating as a function of the Au film thickness. As can be seen, the magnetic coupling strength is a certain A
It becomes zero at the u film thickness or the sufficiently thick Au film thickness.
Therefore, when producing a spin valve film, in order to reduce the bonding strength, a film is formed by selecting a specific nonmagnetic layer thickness at which the bonding strength becomes zero, or the thickness is reduced to a thickness at which the bonding strength becomes sufficiently weak. It is conceivable to adopt a method of forming a film with a thick magnetic layer.

[0006]

However, in the above method, when a film is formed by selecting the thickness of the nonmagnetic layer at which the magnetic coupling strength becomes just zero, a very accurate film thickness control technique is required. Becomes Therefore, a high-performance film forming apparatus is required, and as a result, the apparatus for producing a spin valve film becomes large and complicated, and it is disadvantageous in that it is expensive, and it is difficult to handle as the whole apparatus becomes large in size. was there.

Further, in the above method, when the thickness of the nonmagnetic layer whose magnetic coupling strength is attenuated and becomes zero is selected and formed, the thickness of the nonmagnetic layer of the spin valve film is increased. Accompanying this, there is a disadvantage that the magnetoresistance effect exhibited by the film becomes smaller and the magnetic field detection sensitivity decreases.

The problem to be solved by the present invention is to provide a method for reducing the strength of the coupling strength between magnetic layers without forming a film with a specific film thickness with high accuracy, thereby achieving a small, simple, and easy-to-use device. An object of the present invention is to provide a high-performance magnetic / non-magnetic multilayer film that can be manufactured by an easy film forming apparatus.

Another object of the present invention is to provide a method for reducing the strength of the coupling between magnetic layers without increasing the thickness of the non-magnetic layer, thereby providing a high-performance magnetic / non-magnetic layer. An object of the present invention is to provide a magnetic multilayer film.

[0010]

The above problems can be solved by changing the shape of the interface between the magnetic layer and the non-magnetic layer from a conventional flat one to an uneven one.

Here, the phenomena underlying the present invention will be described. As shown in FIG. 3, the magnetic layer 12, the non-magnetic layer 11,
A spin valve film composed of four layers, a magnetic layer 13 and an antiferromagnetic layer 14, is considered. As described above, the antiferromagnetic layer 14 fixes the direction of the magnetization 15 of the magnetic layer 13 in contact with the magnetic layer 13 in one direction. At this time, the magnetization 16 of the magnetic layer 12 not in contact with the antiferromagnetic layer 14 and the magnetization 15 of the magnetic layer 13
And a magnetic interaction between them through the nonmagnetic layer 11. The magnetization 15 and the magnetization 16 due to this magnetic interaction
The bond strength between the magnetic layer 13 and the nonmagnetic layer 11 is
It is known that the strength varies depending on the shape of the interface 32 between the nonmagnetic layer 11 and the magnetic layer 12, and the bonding strength is lower when the interface is uneven than when the interface is flat. This phenomenon can be seen, for example, in the Physical Review Letters (Physica
l Review Letters, Vol. 67 (1991), pages 1602 to 1605.

[0012]

FIG. 4 is a diagram showing a basic configuration of an embodiment of a spin valve film for a magnetic head according to the present invention. This structure includes a magnetic layer 12, a nonmagnetic layer 11, a magnetic layer 13, and an antiferromagnetic layer 14. Here, the magnetic layer 12 not in contact with the antiferromagnetic layer 14 is a free layer, and the magnetic layer 13 in contact with the
Is a fixed layer. In this spin valve film, the interface 41 between the magnetic layer 13 and the non-magnetic layer 11 and the interface 42 between the non-magnetic layer 11 and the magnetic layer 12 are made uneven. Here, the size d of the irregularities required to reduce the coupling strength between the magnetic layers
Depends on the material and crystal orientation of the nonmagnetic layer 11 and the degree of reduction of the coupling strength. For example, consider Cu (001) having an average thickness of t atomic layers as the nonmagnetic layer 11. At this time, the thickness of the nonmagnetic layer 11 has a distribution of (t-1) atomic layers, t atomic layers, and (t + 1) atomic layers, and the distribution ratios to the total area of the interface are 0.25 and 0.5, respectively. , 0.25, the magnetic coupling strength between the magnetic layers is about 1
Physical Review Letters Becoming 1/10
(Physical Review Letters) Vol. 67 No. 12 (1991)
(Year) pages 1602 to 1605. Therefore, when actually manufacturing a spin valve film, the nonmagnetic layer 11
The appropriate size and degree of the unevenness may be selected depending on the material and crystal orientation of the material and the degree of the required reduction in the bonding strength. At this time, the unevenness distribution in the interface may be random, and need not be particularly regular.

In this configuration, the magnetic coupling acting between the magnetic layer 12 and the magnetic layer 13 via the non-magnetic layer 11 is small or zero, so that the magnetization 16 of the free layer can be easily formed by an external magnetic field. Can rotate. Therefore, a spin valve film having high detection sensitivity for an external magnetic field can be obtained.

Further, according to the present invention, the thickness of the nonmagnetic layer 11 can be reduced as compared with the conventional spin valve film, so that the magnetoresistive effect exhibited by the film becomes larger.
When applied to a magnetic head, higher output can be obtained.

Further, in the present invention, since the absolute accuracy with respect to the average thickness t of the nonmagnetic layer 11 may be lower than that of the conventional spin valve film, when manufacturing the spin valve film,
It is possible to reduce the required precision for controlling the film thickness.

FIG. 5 shows a case where the magnetic coupling between the magnetic layers is sufficiently reduced by one of the two interfaces 41 and 42 on both sides of the nonmagnetic layer 11 in the present invention. As described above, the interface 51 may be made uneven, and the interface 52 may be kept flat like the conventional spin valve film. At this time, the interface to be made uneven is the interface 51 in FIG. 5, but may be the interface 52, or at least one of them.

Further, the present invention can be applied to the dual spin valve film shown in FIG. The configuration of the dual spin valve film includes an antiferromagnetic layer 61, a magnetic layer 62, a nonmagnetic layer 63, a magnetic layer 64, a nonmagnetic layer 65, a magnetic layer 66, and an antiferromagnetic layer 67. Here, the magnetic layer 64 not in contact with the antiferromagnetic layer 61 and the antiferromagnetic layer 67 is a free layer,
The magnetic layer 62 in contact with the antiferromagnetic layer 61 and the magnetic layer 66 in contact with the antiferromagnetic layer 67 are both fixed layers.
At this time, the direction of the magnetization 68 of the magnetic layer 62 and the direction of the magnetic layer 66
Antiferromagnetic layer 6 so that the direction of magnetization 69 of
1 and the antiferromagnetic layer 67. in this case,
The magnetization 70 of the magnetic layer 64 at the center of the dual spin valve film is rotated by the external magnetic field 17. At this time, the electric resistance in the film plane becomes minimum when the magnetization 68 of the magnetic layer 62 and the magnetization 69 of the magnetic layer 66 are parallel to each other, and becomes maximum when the magnetization is antiparallel.

In this dual spin valve film, as shown in FIG. 7, an interface 7 between the magnetic layer 62 and the non-magnetic layer 63 is formed.
1, interface 72 between nonmagnetic layer 63 and magnetic layer 64, magnetic layer 6
An interface 73 between the nonmagnetic layer 4 and the nonmagnetic layer 65 and an interface 74 between the nonmagnetic layer 65 and the magnetic layer 66 are made uneven. Here, as in the case of the spin valve film, the size of the concavities and convexities necessary for reducing the coupling strength between the magnetic layers depends on the material and crystal orientation of the nonmagnetic layer 63 and the nonmagnetic layer 65, and the coupling between the magnetic layers. It depends on the degree of strength reduction. Therefore, when actually fabricating this dual spin valve film, an appropriate degree of unevenness may be selected according to the material and crystal orientation of the nonmagnetic layer and the degree of required reduction of the coupling strength. The distribution of the irregularities in the interface may be random, and need not be particularly regular.

In this configuration, since the magnetic coupling acting between the magnetic layers via the nonmagnetic layer 63 and the nonmagnetic layer 65 is small or zero, the magnetization 75 of the free layer is easily rotated by an external magnetic field. Therefore, a dual spin valve film having high detection sensitivity for an external magnetic field can be obtained.

Further, according to the present invention, the non-magnetic layer 63 and the non-magnetic layer 65 are compared with the conventional dual spin valve film.
Can be reduced in thickness, so that the magnetoresistance effect of this film is further increased. Therefore, when this film is applied to a magnetic head, a higher output can be obtained.

Further, similarly to the above spin valve film, in the present invention, the absolute accuracy with respect to the average thickness of the nonmagnetic layer may be lower than that of the conventional dual spin valve film.
When fabricating a dual spin valve film, it is possible to reduce the required precision for controlling the film thickness.

Further, in the present invention, the magnetic coupling between the magnetic layers is caused by one of the interface 71 and the interface 72 on both sides of the nonmagnetic layer 63 and the interface 73 and the interface 74 on both sides of the nonmagnetic layer 65. Is sufficiently reduced, the interface 81 and the interface 84 as shown in FIG.
May be uneven, and the interface 82 and the interface 83 may be flat as in the conventional dual spin valve film. At this time, the interface to be uneven is selected from the interface 81 and the interface 84 in FIG. 8, but may be any combination of the interface 81 and the interface 83, or the interface 82 and the interface 83, or the interface 82 and the interface 84. Any combination of at least one of them may be used.

Further, in this embodiment, the case where a spin valve film and a dual spin valve film are used has been described. However, even in a general magnetic / non-magnetic multilayer film, a magnetic layer which is not in contact with the non-magnetic layer and the anti-ferromagnetic layer is used. By making the shape of the interface with the layer uneven, the magnetic coupling strength between the magnetic layers can be reduced.

Further, in this embodiment, it is necessary to make the interface between the magnetic layer and the non-magnetic layer uneven, but the unevenness may be made by the following method.

The magnetic / non-magnetic multilayer film is generally formed by vacuum deposition called a sputter deposition method. In this sputter deposition method, a material (target) to be formed into a film is placed on a cathode (cathode) in a vacuum in which an inert gas such as Ar is introduced, and positive ions (Ar ions) generated by discharge between the electrodes are generated. In this method, the knocked-out (sputtered) particles adhere to a facing substrate to form a thin film by hitting a cathode target. In this sputter deposition method, when the distance between the target and the substrate is reduced, the substrate surface is exposed to plasma due to discharge, and the substrate surface becomes uneven due to damage by the plasma. Therefore, for example, after evaporating a magnetic material to an appropriate thickness, the distance between the target and the substrate is reduced to form irregularities, and if a non-magnetic material is formed thereon, irregularities are formed at the interface between the magnetic material and the non-magnetic material. Will be done.

Further, the magnetic properties obtained by the sputter deposition method
In addition to the method of forming irregularities on the non-magnetic interface, the following method may be used.

In the above-mentioned vacuum, after depositing a magnetic or non-magnetic material having an appropriate thickness, Ar ionized by an ion gun is accelerated and bumped against the substrate surface, whereby irregularities are formed on the substrate surface. By forming a non-magnetic material or a magnetic material on the uneven surface, unevenness is formed at the interface between the magnetic material and the non-magnetic material. The method of hitting the sample surface with ions shown here is a general method of surface cleaning called an ion sputtering method.

Further, in addition to the method of forming irregularities on the magnetic / non-magnetic interface by the above-mentioned sputter deposition method or ion sputtering method, the following method may be used.

During film formation by an ion deposition method or the like,
The growth mode of the sample on the substrate may vary depending on the substrate temperature. For example, in the case of depositing Ag, when the substrate temperature is lowered to about the temperature of liquid nitrogen, the sample surface after film formation becomes flat, but when film formation is performed near room temperature, the sample surface after film formation becomes uneven. By forming a non-magnetic material or a magnetic material on the uneven surface, unevenness is formed at the interface between the magnetic material and the non-magnetic material. Therefore, by controlling the substrate at an appropriate temperature during film formation, irregularities can be formed at the interface between the magnetic layer and the nonmagnetic layer. At this time, since the size of the unevenness differs depending on the sample and the substrate temperature, the experimental conditions may be appropriately selected according to the required size of the unevenness.

[0030]

According to the present invention, it is possible to reduce the strength of the coupling between magnetic layers without forming a film with a specific film thickness with high precision. There is an effect that a high-performance magnetic / non-magnetic multilayer film can be manufactured by the apparatus. Furthermore, the magnetic / magnetic layer having the same non-magnetic layer
Even in the case of a non-magnetic multilayer film, the magnetic coupling strength acting between the magnetic layers can be reduced, so that the external magnetic field sensitivity of the free layer can be increased. There is an effect that the magnetic field detection sensitivity can be increased.

Further, since the magnitude of the magnetoresistance effect of the magnetic / nonmagnetic multilayer film increases as the thickness of the nonmagnetic layer decreases, it is possible to reduce the thickness of the nonmagnetic layer according to the present invention. If possible, it is possible to increase the magnetoresistance effect exhibited by the magnetic / non-magnetic multilayer film, thereby increasing the output of a magnetic field detection device such as a magnetic head, that is, increasing the sensitivity of the magnetic field detection device. is there.
The application of these effects to academic fields, and their industrial value, is very high.

[Brief description of the drawings]

FIG. 1 is a perspective view illustrating a configuration of a spin valve film.

FIG. 2 is a measurement diagram of magnetic interlayer coupling strength for explaining a phenomenon that is a principle of the present invention.

FIG. 3 is a cross-sectional view illustrating a configuration of a spin valve film.

FIG. 4 is a sectional view illustrating a basic configuration of a spin valve film according to one embodiment of the present invention.

FIG. 5 is a cross-sectional view illustrating a basic configuration of a spin valve film according to another embodiment of the present invention.

FIG. 6 is a perspective view illustrating a configuration of a dual spin valve film.

FIG. 7 is a sectional view illustrating a basic configuration of a dual spin valve film according to one embodiment of the present invention.

FIG. 8 is a cross-sectional view illustrating a basic configuration of a dual spin valve film according to another embodiment of the present invention.

[Explanation of symbols]

11: non-magnetic layer, 12: magnetic layer, 13: magnetic layer, 14 ...
Antiferromagnetic layer, 15: magnetization, 16: magnetization, 17: external magnetic field, 31: interface, 32: interface, 41: interface, 42: interface, 51: interface, 52: interface, 61: antiferromagnetic layer, 62
... magnetic layer, 63 ... non-magnetic layer, 64 ... magnetic layer, 65 ... non-magnetic layer, 66 ... magnetic layer, 67 ... antiferromagnetic layer, 68 ... magnetization,
69 ... magnetization, 70 ... magnetization, 71 ... interface, 72 ... interface, 7
3 interface, 74 interface, 75 magnetization, 81 interface, 82
... Interface, 83 ... Interface, 84 ... Interface.

Claims (5)

[Claims] 1. A magnetic / magnetic device comprising a magnetic layer and a non-magnetic layer alternately laminated.
In a magnetic field measurement method using a phenomenon in which the electrical resistance of a magnetic layer changes greatly depending on whether the magnetization arrangement of the magnetic layer in a nonmagnetic multilayer film is ferromagnetic or antiferromagnetic, an uneven shape is formed at the interface between the magnetic layer and the nonmagnetic layer. A magnetic field measuring apparatus using a magnetic / non-magnetic multilayer film having the following. 2. A magnetic field measuring apparatus according to claim 1, wherein said magnetic / non-magnetic multilayer film is a multilayer film composed of four layers of a magnetic layer / non-magnetic layer / magnetic layer / antiferromagnetic layer. 3. The magnetic field measuring apparatus according to claim 2, wherein one or both of the two interfaces of the magnetic layer and the nonmagnetic layer have an uneven shape. 4. The multi-layered film according to claim 1, wherein said multi-layered film comprises seven layers: antiferromagnetic layer / magnetic layer / nonmagnetic layer / magnetic layer / nonmagnetic layer / magnetic layer / antiferromagnetic layer. A magnetic field measuring apparatus, characterized in that: 5. A magnetic field measuring apparatus according to claim 4, wherein at least one of the four interfaces between the magnetic layer and the nonmagnetic layer has an uneven shape.