JPH08279115A - Multilayered film for magneto-resistance effect element and adjustment of magnetization of magnetic layer - Google Patents

Abstract

PURPOSE: To obtain multilayered films having a high resistance change rate by laminating diamagnetic bonding units laminated with ferromagnetic metallic layers and nonmagnetic metallic layers and weakly ferromagnetic units laminated with the ferromagnetic metallic layers and nonmagnetic metallic layers on a substrate. CONSTITUTION: The antiferromagnetic bonding unit (a) having a two-layered structure is formed by laminating the ferromagnetic metallic layers 1, 3 across the nonmagnetic metallic layer 2. The weakly ferromagnetic bonding unit (b) is formed by laminating the nonmagnetic metallic layers 4, 6 across the ferromagnetic metallic layer 5. The double antiferromagnetic bonding unit (d) having a three-layered structure is formed by laminating the ferromagnetic metallic layer 7, the nonmagnetic metallic layer 8, the ferromagnetic metallic layer 9, the nonmagnetic metallic layer 10 and the ferromagnetic metallic layer 11. Further, the double weakly ferromagnetic bonding unit (e) is formed by laminating the nonmagnetic metallic layer 12, the ferromagnetic metallic layer 13 and the nonmagnetic metallic layer 6. The films having the high resistance change rate are obtd. by forming the antiferromagnetic bonding. The resistance change rate is increased by repeating the antiferromagnetic bonding units and the weakly ferromagnetic bonding units.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer film for a magnetoresistive element used in a magnetic head, a position sensor, a rotation sensor, etc., and a method for adjusting the magnetization of a magnetic layer.

[0002]

2. Description of the Related Art Conventionally, a Ni--Fe alloy thin film (permalloy thin film) has been known as a magnetoresistive (MR) effect material used for this kind of application, and the resistance change rate of the permalloy thin film is 2 to 2. 3% is typical. Therefore, in the future, a magnetoresistive effect material having a larger resistance change ratio (MR ratio) is desired in order to cope with the improvement of the linear recording density and the track density in the magnetic recording or the higher resolution of the magnetic sensor.

By the way, in recent years, a phenomenon called a giant magnetoresistive effect is caused by an alternating laminated film of Fe / Cr or Co / C.
It has been found in multilayer thin films such as u alternating laminated films. In these multilayer thin films, the magnetization of each ferromagnetic metal layer made of Fe, Co, etc. causes a magnetic interaction through the nonmagnetic metal layer made of Cr, Cu, etc. The magnetizations of the layers are coupled so that they remain antiparallel in the absence of an external magnetic field. That is, in these structures, the ferromagnetic metal layers that are alternately stacked with the non-magnetic metal layer in between are layered so that the magnetization directions are opposite to each other. Then, in these structures, when an appropriate external magnetic field is applied, the magnetization directions of the ferromagnetic metal layers change so as to be aligned in the same direction.

In the above structure, when the magnetizations of the respective ferromagnetic metal layers are in the antiparallel state and the parallel state, the interface between the Fe ferromagnetic metal layer and the Cr nonmagnetic metal layer or the Co ferromagnetic metal layer is used. It is said that the scattering of conduction electrons at the interface of the Cu nonmagnetic metal layer differs depending on the spin of the conduction electrons. Therefore, based on this mechanism, the electric resistance is high when the magnetization directions of the ferromagnetic metal layers are in the antiparallel state, and the electric resistance is low when the magnetization directions are in the parallel state, and the resistance change rate exceeds that of the conventional permalloy thin film. The so-called giant magnetoresistive effect is generated. Thus, these multi-layer thin films are fundamentally different from conventional Ni-Fe single-layer thin films by M
It has an R generation mechanism.

However, in these multilayer films, the magnetic interaction between the ferromagnetic metal layers that act so as to make the magnetization directions of the ferromagnetic metal layers antiparallel to each other is too strong. There is a problem in that a very large external magnetic field must be applied in order to make the magnetization directions of the two parallel. Therefore, a large change in resistance does not occur unless a strong magnetic field is applied, and satisfactory high sensitivity cannot be obtained when applied to a device that detects a minute magnetic field from a magnetic recording medium such as a magnetic head. There was a problem.

In order to solve this problem, the thickness of the non-magnetic metal layer made of Cr, Cu or the like is adjusted so that the magnetic interaction acting between the ferromagnetic metal layers is not excessively strengthened. It seems effective to control the relative direction of the magnetization of the magnetic metal layer by a method other than the magnetic interaction. Conventionally, as a technique for controlling the relative direction of such magnetization, by providing an antiferromagnetic layer such as FeMn, the direction of magnetization of one ferromagnetic metal layer is fixed, and the direction of magnetization of this ferromagnetic metal layer is fixed. A technique has been proposed which enables operation by a minute magnetic field by making the magnetic field hard to move with respect to an external magnetic field and by freely moving the magnetization direction of the other ferromagnetic metal layer.

FIG. 12 shows an example of a magnetoresistive sensor having a structure to which this type of technology disclosed in Japanese Patent Laid-Open No. 6-60336 is applied. The magnetoresistive sensor A shown in FIG. 12 includes a nonmagnetic substrate 30, a first magnetic layer 31, a nonmagnetic spacer 32, a second magnetic layer 33, and an antiferromagnetic layer 3.
And a second magnetic layer 33.
Direction B is fixed by magnetic exchange coupling by the antiferromagnetic layer 34, and the direction C of magnetization of the first magnetic layer 31 is fixed to the direction of magnetization of the second magnetic layer 33 when there is no applied magnetic field. It is oriented at a right angle to B. However, since the magnetization direction C of the first magnetic layer 31 is not fixed, it can be rotated by an external magnetic field.

When an applied magnetic field h is applied to the structure shown in FIG. 12, the first magnetic layer 31 changes depending on the direction of the applied magnetic field h.
Since the direction C of magnetization of the first magnetic layer 31 rotates as indicated by a dotted arrow, a difference in direction of magnetization occurs between the first magnetic layer 31 and the second magnetic layer 33, resulting in a resistance change. This enables magnetic field detection.

Next, as another example of the magnetoresistive sensor B in which the magnetization direction of one magnetic layer is fixed and the magnetization direction of the other magnetic layer is free, as shown in FIG. 35, a NiO antiferromagnetic layer 36, a Ni—Fe magnetic layer 37, a Cu nonmagnetic metal layer 38, and a Ni—Fe layer 35.
Magnetic layer 39 of Cu, non-magnetic metal layer 40 of Cu, and Ni-F
A structure in which a magnetic layer 41 of e and an antiferromagnetic layer 42 of FeMn are sequentially stacked is known. In the structure of this example, the magnetizations of the ferromagnetic metal layers 37 and 41 adjacent to the antiferromagnetic layers 36 and 42 are fixed, and the nonmagnetic metal layers 38 and 40 are interposed between the ferromagnetic metal layers 37 and 41. The magnetization of the ferromagnetic metal layer 39 sandwiched by the magnets is configured to be rotatable according to an external magnetic field.

In the magnetoresistive sensor having the structure shown in FIG. 12 or FIG. 13, the electric resistance of the magnetoresistive sensor A or the magnetoresistive sensor B changes with high sensitivity to a minute change in the applied magnetic field. In addition, as the first magnetic layer 2, Ni-F is used.
When a soft magnetic material such as e is used, the soft magnetism can be utilized, and there are advantages such as less hysteresis.

[0011]

However, as shown in FIG.
2, or the magnetoresistive sensor having the structure shown in FIG.
The antiferromagnetic layer 34 of eMn fixes the magnetization of the adjacent second magnetic layer 33, or the antiferromagnetic layers 36 and 42 of FeMn and NiO above and below magnetize the ferromagnetic metal layers 37 and 41 between them. Is fixed and the magnetization of the magnetic layer 39 between them is made free, so that Ni- which contributes to the giant magnetoresistive effect
There is a restriction that the number of Fe (magnetic layer) / Cu (non-magnetic metal layer) interfaces cannot be increased, and there is a problem that the MR ratio is restricted. Therefore, in the structure shown in FIG. 12 or FIG. 13, there is a problem that a large MR ratio exceeding 10% cannot be realized due to the structure. In addition, the antiferromagnetic layer 3
FeMn used as a constituent material for Nos. 4 and 36 has disadvantages in terms of corrosion resistance and environment resistance.

The present invention has been made in view of the above circumstances, and is obtained in a conventional structure by forming a laminated structure capable of realizing a multilayer film structure of a magnetic layer, which was not possible in the conventional structure shown in FIG. 12 or FIG. It is possible to obtain a high MR ratio that was not achieved, and at the same time, in some cases, corrosion resistance,
An object of the present invention is to provide a multilayer film for a magnetoresistive effect element and a method for adjusting the magnetization of a magnetic layer, which does not require the use of an antiferromagnetic material having a problem in terms of environment resistance.

[0013]

In order to solve the above-mentioned problems, the invention according to claim 1 is antiferromagnetically coupled by laminating a non-magnetic metal layer between a plurality of ferromagnetic metal layers. An antiferromagnetic coupling unit and a weak ferromagnetic coupling unit, which is weakly ferromagnetically coupled with the antiferromagnetic coupling unit by sandwiching the ferromagnetic metal layer between a plurality of nonmagnetic metal layers, are laminated on the substrate. It will be. Also, in this structure,
On the weak ferromagnetic coupling unit, a plurality of nonmagnetic metal layers are sandwiched between a plurality of ferromagnetic metal layers to form an antiferromagnetically coupled antiferromagnetic unit, and a plurality of nonmagnetic metal layers. It is also possible to form a structure in which one or more layers of the antiferromagnetically coupled unit and the weakly ferromagnetically coupled unit that are weakly ferromagnetically coupled are laminated by sandwiching the ferromagnetic metal layer between them.

Next, in the above structure, the ferromagnetic metal layer is composed of at least one selected from Co, NiFe alloy, and CoFeNi alloy, and the nonmagnetic metal layer is Au, Ag, Cu.
You may comprise from 1 or more types selected from. Also,
In the multilayer film for a magnetoresistive element having the above structure, an antiferromagnetic layer may be added to at least one of the uppermost layer and the lowermost layer of the laminated film. Furthermore, in the above-described multilayer film for a magnetoresistive effect element, the antiferromagnetic layer may be composed of at least one selected from FeMn, NiO, and NiMn.

Next, in the multilayer film for a magnetoresistive effect element having the above structure, a high coercive force magnetic layer made of a hard magnetic material may be additionally provided on at least one of the uppermost layer and the lowermost layer of the laminated film. The high coercive force magnetic layer described above is Co
It may be one or more selected from a Cr alloy, a CoCrTa alloy, and a CoPt alloy. Furthermore, in the multilayer film for a magnetoresistive effect element described above, the thickness of the ferromagnetic metal layer is in the range of 10 to 30 Å, and the thickness of the nonmagnetic metal layer in the antiferromagnetic coupling unit is 7 to 11 Å. Range, other than the thickness of the non-magnetic metal layer is 20 ~
It may be formed in the range of 50 Å.

Next, in the multilayer film for a magnetoresistive effect element described above, two ferromagnetic metal layers are provided in the bottom antiferromagnetic coupling unit, and three ferromagnetic metal layers are provided in the reverse antiferromagnetic coupling unit. A layer may be provided, and a plurality of reverse antiferromagnetic coupling units and weak weak ferromagnetic coupling units may be alternately laminated. Further, it is preferable that the multilayer film for a magnetoresistive effect element described above exhibits a characteristic that the electric resistance sharply increases when the external magnetic field is low, and the electric resistance gradually decreases when the external magnetic field is higher.

Next, according to the method of the present invention, an antiferromagnetic coupling unit in which a nonmagnetic metal layer is sandwiched between a plurality of ferromagnetic metal layers and antiferromagnetically coupled is formed, and a ferromagnetic material is provided between the plurality of nonmagnetic metal layers. A weak ferromagnetic coupling unit is formed by weakly ferromagnetically coupling with the above antiferromagnetic coupling unit with a metal layer sandwiched between them, and both units are stacked, and the direction of magnetization of the ferromagnetic metal layer in the weak ferromagnetic coupling unit. Can be changed according to the external magnetic field. In the above method, at least one of an uppermost layer and a lowermost layer of a laminated body including an antiferromagnetic coupling unit, a weak ferromagnetic coupling unit, a deferred antiferromagnetic coupling unit, and a deweak ferromagnetic coupling unit is an antiferromagnetic layer. It is also possible to additionally provide either one of the magnetic layer and the high coercive force magnetic layer to make the ferromagnetic metal layer in contact with the antiferromagnetic layer or the high coercive force magnetic layer into a single magnetic domain.

[0018]

In the present invention, since the antiferromagnetic coupling unit and the weak ferromagnetic coupling unit are laminated on the substrate, the direction of magnetization of the ferromagnetic metal layer in the antiferromagnetic coupling unit is fixed and weak The magnetization direction of the ferromagnetic metal layer in the magnetic coupling unit can be rotated according to an external magnetic field. Further, since the structure of the present invention can be freely laminated in large numbers, it is possible to form a large number of interfaces between the ferromagnetic metal layer and the non-magnetic metal layer exhibiting the giant magnetoresistive effect in the laminate. Therefore, a large MR ratio can be obtained.

The present invention will be described in more detail below. FIG. 1 shows an example of the structure of the multilayer film for a magnetoresistive element according to the present invention. In the multilayer film for a magnetoresistive element of this example, a buffer layer H is formed on a non-magnetic substrate K,
A large number of magnetic layers and non-magnetic metal layers are laminated on top of this. Since the buffer layer J is a base layer for adjusting the crystal orientation of the layer laminated thereon, it may be omitted in some cases.

The ferromagnetic metal layer 1 is formed on the buffer layer J.
A non-magnetic metal layer 2, a ferromagnetic metal layer 3, a non-magnetic metal layer 4, a ferromagnetic metal layer 5, a non-magnetic metal layer 6, a ferromagnetic metal layer 7, a non-magnetic metal layer 8 and a non-ferromagnetic metal layer 9. Magnetic metal layer 10, ferromagnetic metal layer 11, non-magnetic metal layer 12, and ferromagnetic metal layer 13
Are sequentially laminated, and again on the ferromagnetic metal layer 13, the non-magnetic metal layer 6, the ferromagnetic metal layer 7, the non-magnetic metal layer 8, the ferromagnetic metal layer 9, the non-magnetic metal layer 10, and the ferromagnetic metal layer. 11, a non-magnetic metal layer 12, and a ferromagnetic metal layer 13 are sequentially stacked.

The substrate K is made of glass, Si, Al ₂ O ₃ ,
It is composed of a non-magnetic material typified by a sintered body of TiC, SiC, Al ₂ O ₃ and TiC, and non-magnetic ferrite. The ferromagnetic metal layers 1, 3, 5, 7, 9, 11, 13
Is composed of a ferromagnetic metal material having a large rate of change in magnetoresistance such as Co, NiFe alloy, and CoNiFe alloy.
Among these, Co having a large rate of change in magnetic resistance is more preferable. The non-magnetic metal layers 2, 4, 6, 8,
Although 10 and 12 are composed of a non-magnetic metal material such as Au, Ag and Cu, it is most preferred to be composed of Cu among these. In addition, each of the ferromagnetic metal layers 1, 3, 5, 7,
The thickness of 9, 11, and 13 is about 10 to 30 angstroms, the thickness of the nonmagnetic metal layers 2, 8 and 10 in the antiferromagnetic unit is about 7 to 11 angstroms, and the other nonmagnetic metal layers 4 and 6 are , 12 has a thickness of about 20 to 50 angstroms.

In the laminated structure shown in FIG. 1, by stacking the ferromagnetic metal layers 1 and 3 with the non-magnetic metal layer 2 sandwiched therebetween, 2
The antiferromagnetic coupling unit a having a layered structure is formed, and the nonmagnetic metal layers 4 and 6 are laminated with the ferromagnetic metal layer 5 sandwiched therebetween to form the weak ferromagnetic coupling unit b. Here, the weak ferromagnetic coupling unit b is formed because the non-magnetic metal layers 4 and 6 located above and below the ferromagnetic metal layer 5 are formed sufficiently thick. This is because the ferromagnetic metal layers 7 and 3 located above and below the metal layer 5 have a weak magnetic coupling force with the ferromagnetic metal layer 5.

The ferromagnetic metal layer 7, the nonmagnetic metal layer 8, the ferromagnetic metal layer 9, the nonmagnetic metal layer 10 and the ferromagnetic metal layer 11 are also included.
And the anti-ferromagnetic coupling unit d having a three-layer structure is formed by laminating and the non-magnetic metal layer 12, the ferromagnetic metal layer 13, and the non-magnetic metal layer 6 are laminated. Is formed, and the ferromagnetic metal layer 7, the non-magnetic metal layer 8, the ferromagnetic metal layer 9, the non-magnetic metal layer 10 and the ferromagnetic metal layer 11 are further laminated thereon to restore the three-layer structure. A ferromagnetic coupling unit d is constructed.

In the structure shown in FIG. 1, since the ferromagnetic metal layers 1 and 3 are laminated with the non-magnetic metal layer 2 in between, antiferromagnetic coupling (AF coupling) is established, and the two-layered structure is used. 1 antiferromagnetic coupling unit a is configured, and the ferromagnetic metal layers 1, 3
The direction of magnetization is hard to move. Stacked on the first antiferromagnetic coupling unit a is the first weak ferromagnetic coupling unit b having weak ferromagnetic coupling, so that the ferromagnetic metal layer 5 in this unit is It becomes a layer (so-called free layer: indicated by symbol F in FIG. 1) that can be easily reversed by a weak external magnetic field. This allows
There is a difference in the magnetization reversal behavior between the ferromagnetic metal layers 1 and 3 and the ferromagnetic metal layer 5, and thus the Fe of the conventional structure shown in FIGS.
Even if the antiferromagnetic layer made of Mn is not used, a film having high sensitivity and a large resistance change rate can be formed. Therefore, it is also advantageous in terms of corrosion resistance and environment resistance.

Next, the first weak ferromagnetic coupling unit b
Since the antiferromagnetic coupling unit d having a three-layer structure of the ferromagnetic metal layer provided on the top has three ferromagnetic metal layers, the uppermost ferromagnetic metal layer 11 of the antiferromagnetic coupling unit d is The magnetization and the magnetization of the lowermost ferromagnetic metal layer 7 are oriented in the same direction as shown by the arrow in FIG. Therefore, the magnetizations of the upper and lower ferromagnetic metal layers 7 and 11 and the magnetization of the weak ferromagnetic coupling unit e thereon are aligned in the same direction regardless of how many layers are stacked (the number n of stacked layers is increased). .

Therefore, the resistance change rate can be increased by repeating the antiferromagnetic coupling unit d and the weak ferromagnetic coupling unit e. When the number of stacks of the anti-ferromagnetic coupling unit d and the weakly ferromagnetic coupling unit e is increased, it is considered that the arrangement of the spontaneous magnetization when the external magnetic field is 0 gradually collapses. The problem can be easily adjusted and solved by appropriately performing film formation processing in a magnetic field or heat treatment in a magnetic field.

In the structure shown in FIG. 1, the ferromagnetic metal layer 1, the nonmagnetic metal layer 2, the ferromagnetic metal layer 3 and the nonmagnetic metal layer 4 are used.
And the ferromagnetic metal layer 5 are laminated to form a basic unit E, and further, the nonmagnetic metal layer 6, the ferromagnetic metal layer 7, the nonmagnetic metal layer 8, the ferromagnetic metal layer 9, the nonmagnetic metal layer 10 and the strong magnetic layer 10. The magnetic metal layer 11, the non-magnetic metal layer 12, and the ferromagnetic metal layer 13 are laminated to form a laminated unit G.
However, although two are stacked on the basic unit E, the number of stacked layers of the stacked unit G may be any number. If the number of stacked layers is increased to some extent, a large MR ratio can be easily obtained.

FIG. 2 shows a state in which an external magnetic field in the rightward direction (→ direction in the figure) of FIG. 1 is applied to the multilayer film for a magnetoresistive element having the structure shown in FIG. As is clear from this figure, the ferromagnetic metal layers 5 and 1 whose magnetization can be easily reversed
The magnetizations of 3 and 13 (so-called free layer) are all reversed from the state of FIG. Then, in this state, the electric resistance ρ of the entire laminated body becomes larger than that in the case of FIG.
Exhibits a giant magnetoresistive effect.

Next, a multi-layered film for a magnetoresistive effect element having the structure shown in FIG. 1 can be easily formed by using a film forming apparatus such as a sputtering apparatus. Among them, the laminated structure shown in FIG. If so, it is possible to sufficiently form a film with a simple film forming apparatus having three kinds of targets.

Next, in FIG. 3, an antiferromagnetic layer 15 made of an antiferromagnetic material such as NiO is additionally provided on the uppermost layer and the lowermost layer of the multilayer film for a magnetoresistive effect element having the structure shown in FIG. The structure is shown. Although the effect is weakened, either one of the antiferromagnetic layers may be used. In this structure, the ferromagnetic metal layer 9 below the uppermost antiferromagnetic layer 15 is made into a single magnetic domain. In addition, the bottom antiferromagnetic layer H
The ferromagnetic metal layer 1 thereabove is also made into a single magnetic domain. As shown in FIG. 4, the structure in which the antiferromagnetic layer is in contact with the antiferromagnetic coupling unit is not limited to the antiferromagnetic coupling unit, and only one layer of the ferromagnetic films 1 and 9 may be used.

The structure of this example is intended to increase the resistance change rate. Usually, in a structure in which magnetic layers are laminated, the film forming each magnetic layer forms a plurality of magnetic domains within the film plane, and the magnetic domains may have different magnetization directions and be stable in terms of energy. To do. Therefore, even if the structure of FIG. 1 is applied, each magnetic layer is not divided into a single magnetic domain but is divided into a plurality of magnetic domains, and as a result, only about half the area in the film surface contributes to the giant magnetoresistance change. There are cases. In order to improve this, the structure of FIG. 3 or 4 is effective. That is, when the adjacent ferromagnetic metal layers 9 and 1 are forcibly made into a single magnetic domain by the exchange coupling force at the interface with the uppermost antiferromagnetic layer 15 and the lowermost antiferromagnetic layer H, this single magnetic domain is formed. Ferromagnetic metal layers 9 and 1
On the other hand, the other ferromagnetic metal layers are magnetically weakly and ferromagnetically coupled, so that the other ferromagnetic metal layers are sequentially made into a single magnetic domain in the same manner.

If this single domain effect is utilized, the uppermost layer or the lowermost layer is not limited to the antiferromagnetic layer, but a hard magnetic material layer may be provided, for example. The hard magnetic material layer is specifically a CoCr alloy, CoCrT
a alloy, CoCrNi alloy, CoCrMo alloy, CoP
A t alloy or the like can be used.

More specifically, as shown in FIG. 5, when one ferromagnetic metal layer 13 is viewed from above, the ferromagnetic metal layer 13 is divided into two magnetic domains, an arrow O and an arrow Q.
As shown in FIG. 5, magnetizations in different directions are formed and magnetic energy is stabilized, and accordingly, the antiferromagnetic coupling unit d
The magnetization directions of the upper and lower ferromagnetic metal layers are as shown by arrows P and R for each magnetic domain. When a magnetic field indicated by the arrow X pointing to the right is applied to the ferromagnetic metal layer 13 in this state as shown in FIG. 6, the relative direction of magnetization of the upper half magnetic domain of the ferromagnetic metal layer 13 does not change, but the lower half Only the relative direction of the magnetization of the magnetic domain of is changed, and this portion comes to contribute to the giant magnetoresistive effect. Therefore, only the half area of the ferromagnetic metal layer 13 contributes to the giant magnetoresistive effect, and the MR ratio does not increase. Therefore, in order to solve this problem, the antiferromagnetic layer 15 is provided as in the above structure to make the ferromagnetic metal layer 9 into a single magnetic domain. Similarly, the lowermost antiferromagnetic layer H may be provided to make the ferromagnetic layers 1 and 9 into a single magnetic domain.

Next, the reason why the thickness of each layer is limited to the above range in the above structure will be described. In the multilayer film for a magnetoresistive effect element, which has a combination of a ferromagnetic metal layer and a non-magnetic metal layer as in the above structure, the magnetic moment between the magnetic layers exhibits an indirect exchange coupling state through conduction electrons. In this indirect exchange coupling, the exchange coupling coefficient J oscillates between positive and negative depending on the layer thickness of the non-magnetic metal layer, and when it is positive, it is ferromagnetic coupling, and when it is negative, it is antiferromagnetic coupling.

FIG. 7 shows M when the Cu layer thickness of a Co / Cu multilayer film having a structure in which a Co layer and a Cu layer are repeatedly laminated is changed.
It is the experimental data which showed the change of R ratio. It is clear that when the Cu layer thickness is 9 angstroms and 20 angstroms, the Co layer is in an antiferromagnetically coupled state and the MR change is large. In the structure of the present invention, the Co—Co layers in the antiferromagnetic coupling units a and d need to have strong antiferromagnetic coupling, so that the nonmagnetic metal layers 2, 8 and 10 of the structure shown in FIG. The thickness utilizes the maximum peak of 9 angstroms in FIG. 3, and is preferably in the range of 7 to 11 angstroms.

In the weak ferromagnetic coupling units b and e having the structure shown in FIG. 1, it is necessary to form the nonmagnetic metal layers 4, 6 and 12 having such a thickness as to achieve weak ferromagnetic coupling. When these nonmagnetic metal layers 4, 6, 12 are too thick and the ferromagnetic metal layers 5, 13 of the weak ferromagnetic coupling units b, e are in a free magnetization state, the ferromagnetic metal layers 5, 13 are in-plane. Since it has a plurality of magnetic domains, it becomes stable in a state having a plurality of magnetic domains. In this case, as in the case described above with reference to FIGS. 4 and 5, the area of the ferromagnetic metal layer for exhibiting the giant magnetoresistive effect when an external magnetic field is applied is halved. Further, when the ferromagnetic metal layer is divided into a plurality of magnetic domains, it has a magnetic domain wall. However, the magnetic domain layer causes Barkhausen noise when the ferromagnetic metal layer is inverted by a weak external magnetic field.

From the above, the non-magnetic metal layers 4, 6, 1
2 must be not too thick, and strong exchange coupling hinders easy magnetization reversal. Therefore, the thickness of the non-magnetic metal layers 4, 6, 12 is
20-50 angstroms are preferred, and 25-30 angstroms thickness is more preferred.

Next, regarding the thicknesses of the ferromagnetic metal layers 1, 3, 5, and 7, in the case of a laminated film having a multilayer structure as in the present invention, it is required that the interfaces between the layers be sharp. It is desirable that the layer has good orientation and coherent crystal bonding between layers. For this reason, if it is too thin, the film will be in an island state with poor continuity, and if it is too thick, the unevenness of the interface will increase toward the upper layer of the laminate, which is not preferable. Therefore, the range of 10 to 50 angstroms is preferable, and the range of 15 to 30 angstroms is more preferable.

The thickness of each layer described above is Co /
According to the experimental data of the Cu multilayer film, the non-magnetic metal layer is Cu, the ferromagnetic metal layer is Co, NiFe alloy,
In the case of CoNiFe alloy, it has been confirmed that the peak of 1 is around 9 angstrom when the MR ratio vibrates. However, in the case of materials of other combinations, the thickness of the first peak of the MR ratio is different. In the case of the material of the combination of, the thickness may be set to give the first peak value.
Therefore, it is preferable to set the thickness of the non-magnetic metal layer in the range of 7 to 11 angstroms.

[0040]

Embodiments of the present invention will be described below with reference to the drawings. Using a high frequency magnetron sputtering apparatus equipped with each target of Fe, Co and Cu, on a substrate 20 shown in FIG. 8 made of silicon single crystal or glass,
The Fe buffer layer 21, the Co layer 22, the Cu layer 23, the Co layer 24, the Cu layer 25 and the Co layer 26 were laminated as shown in FIG. 8 to obtain a multilayer film for a magnetoresistive effect element. The sputtering conditions during film formation are RF power of 20 for Fe and Co.
0 W, Cu 100 W, Ar gas pressure 1 mTorr
And The thickness of each layer is 50 Å for the Fe buffer layer 21, 15 Å for the Co layers 22, 24 and 26, 9 Å for the Cu layer 23 in the ferromagnetic coupling unit, and 3 for the Cu layer 25 of the weak ferromagnetic coupling unit.
It was set to 0 angstrom.

FIG. 9 shows the magnetization curve of the multilayer film for a magnetoresistive effect element having the structure shown in FIG. A characteristic MH curve due to the soft magnetization reversal region of the Co layer 26 and the Co layers 22 and 24 having a large reversal magnetic field was obtained. In addition, FIG.
3 shows a resistance change curve of the multilayer film for a magnetoresistive effect element having the structure shown in FIG. In this figure, the region showing the practical magnetic field change sensitivity is the region shown by the thick line in FIG. 10, and the resistance change rate by ΔR / R ₀ showed a value of 5.7%. In this structure, it is clear that the electric resistance rapidly increases when the external magnetic field is low, and the electric resistance gradually decreases when the external magnetic field is higher. It became clear that it is effective as a resistance effect element.

Further, with respect to this structure, the Fe buffer layer 2
Instead of 1, a NiO layer having a thickness of 300 angstroms was provided as an antiferromagnetic layer, and the film was formed in a magnetic field.
The rate of resistance change represented by ΔR / R was 6.8%. Furthermore, the sample in which a CoPt layer having a thickness of 50 angstrom was formed instead of the antiferromagnetic layer of NiO was magnetized and evaluated, and the resistance change rate indicated by ΔR / R was 6.2%. showed that.

Next, on the structure shown in FIG. 8, one or a plurality of laminated units indicated by reference symbol G in FIG. 1 were laminated to prepare samples, and tests were conducted to evaluate the characteristics of each sample. This laminated unit G is made of Cu (30) / Co (15) / C
u (9) / Co (15) / Cu (9) / Co (15) /
The structure was Cu (30) / Co (15). Therefore, the entire structure is represented by the formula shown below. In the formula, the unit of thickness indicated by the numerical value in () is angstrom. Glass substrate / Fe (50) / Co (15) / Cu (9)
/ Co (15) / Cu (30) / Co (15) / [Cu
(30) / Co (15) / Cu (9) / Co (15) /
Cu (9) / Co (15) / Cu (30) / Co (1
5)] n However, in this equation, n = 0, 1, 2, 3, 4.

In the structure represented by the above formula, n = 0
The total thickness is 134 Å, n = 1
, The total thickness is 272 Å, n = 2
For 410 Å, for n = 3 54
8 angstroms, 686 angstroms when n = 4. FIG. 11 shows the results of obtaining the resistance change rate ΔR / R ₀ (where ΔR is the value defined in FIG. 10) of the multilayer film for a magnetoresistive effect element of each thickness described above. As is clear from FIG. 11, the value of ΔR / R ₀ tends to increase up to the number of repetitions n = 2, but the value of the resistance change rate obtained tends to be saturated even if the number of stacked layers is more than that. It became clear.

Next, Table 1 below shows the results of measuring the characteristics of the multilayer film for a magnetoresistive effect element having the above-described structure, prepared by appropriately changing the constituent materials of the respective layers. In Table 1, the value of ΔH indicates the amount of change in the magnetic field when reading ΔR, as shown in FIG. 10, and the smaller the value, the better the rate of change in resistance.

[0046]

[Table 1]

As shown in Table 1, in the structure of the present invention, an excellent rate of resistance change was obtained. Further, the ferromagnetic metal layer of the weak ferromagnetic coupling unit is not limited to Co, but may be a NiFe alloy or NiFe.
It has become clear that a Co alloy is also acceptable. Further, it has been clarified that the nonmagnetic metal layer is not limited to Cu, and Au or Ag may be used.

[0048]

As described above, according to the present invention, an antiferromagnetic coupling unit in which a ferromagnetic metal layer and a nonmagnetic metal layer are laminated, and a weak ferromagnetic layer in which a ferromagnetic metal layer and a nonmagnetic metal layer are laminated. Since the coupling unit is laminated on the substrate, the direction of magnetization of the ferromagnetic metal layer in the antiferromagnetic unit is fixed, and the direction of magnetization of the ferromagnetic metal layer in the weak ferromagnetic unit is adjusted according to the external magnetic field. It has a rotatable structure. Therefore, it is possible to cause a resistance change in a state where the magnetization of the weak ferromagnetic unit is not rotated and a state after the magnetization is rotated.
Since a giant magnetoresistance change occurs due to the behavior of conduction electrons at the interface between the ferromagnetic metal layer and the nonmagnetic metal layer, a large MR ratio can be obtained. Therefore, it is possible to provide an excellent multilayer film for a magnetoresistive effect element which exhibits a large MR ratio. In addition, in the above structure, the anti-ferromagnetic coupling unit and the weakly-weak ferromagnetic coupling unit can be stacked freely in the required number of layers. Therefore, by stacking a plurality of layers, a ferromagnetic layer caused by a giant magnetoresistance change can be formed. The number of interfaces of the non-magnetic layer can be increased, and as a result, a multilayer film for a magnetoresistive element having a larger MR ratio than that of the conventional structure can be obtained.

Concretely, as the ferromagnetic metal layer, C
o, selected from NiFe alloy, CoFeNi alloy 1
One or more kinds can be used, and specifically, one or more kinds selected from Au, Ag, and Cu can be used as the nonmagnetic metal layer.

Next, an antiferromagnetic layer is provided on at least one of the uppermost layer and the lowermost layer of the laminated structure composed of the antiferromagnetically coupled unit and the weakly ferromagnetically coupled unit, so that the ferromagnetic material contacting the antiferromagnetic layer is provided. The metal layer can be made to have a single magnetic domain, which can prevent a plurality of magnetic domains from being formed in the ferromagnetic layer. In this way, if the uppermost or lowermost ferromagnetic layer can be made into a single magnetic domain, the other ferromagnetic layers magnetically coupled to that layer can also be made into a single magnetic domain, so that the entire area of each ferromagnetic layer is The giant magnetoresistive effect can be surely exhibited, and a large MR ratio can be generated. Specifically, FeMn, NiO, NiMn, or the like can be used as the antiferromagnetic layer for making the ferromagnetic layer into a single magnetic domain.

Further, as a structure for converting the abutting ferromagnetic metal layer into a single magnetic domain, a high coercive force magnetic layer can be used instead of the above antiferromagnetic layer. In this case as well, the abutting ferromagnetic metal layer can be made to have a single magnetic domain, and in this case, a CoCr alloy, a CoCrTa alloy, a CoCrNi alloy, a CoCrM is specifically used.
An o alloy, a CoPt alloy, or the like can be used.

Next, in the above structure, when the ferromagnetic metal layer and the non-magnetic metal layer are laminated, in order to surely weakly couple the ferromagnetic metal layers in the weak ferromagnetic coupling unit, there is an interposition therebetween. The thickness of the non-magnetic layer is 20 to 5
It is preferably in the range of 0 angstrom. Further, in order to ensure the antiferromagnetic coupling between the ferromagnetic metal layers in the antiferromagnetic coupling unit, it is preferable that the thickness of the nonmagnetic layer be in the range of 7 to 11 angstroms. Further, in any case, the thickness of the ferromagnetic metal layer is set in the range of 10 to 30 angstroms in order to stabilize the state of the interface of the laminated portion and the film formation state and to arrange the crystal structure of each layer. It is preferable.

Next, by forming the multilayer film for a magnetoresistive effect element having the above-described structure, the electric resistance sharply increases when the external magnetic field is low, and gradually decreases when the external magnetic field is higher. It is possible to obtain a multilayer film for a magnetoresistive effect element that exhibits a decreasing characteristic, and by using a multilayer film for a magnetoresistive effect element having this characteristic, it is possible to provide a magnetoresistive material that reacts sensitively even in a low external magnetic field.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing one structural example of a multilayer film for a magnetoresistive effect element according to the present invention.

2 is a cross-sectional view showing a state in which an external magnetic field is applied to the structure shown in FIG.

FIG. 3 is a second multilayer film for a magnetoresistive effect element according to the present invention.
3 is a cross-sectional view showing a structural example of FIG.

FIG. 4 is a third multilayer film for a magnetoresistive effect element according to the present invention.
3 is a cross-sectional view showing a structural example of FIG.

FIG. 5 is a schematic diagram showing the direction of magnetization that occurs when the ferromagnetic metal film is divided into two magnetic domains and no external magnetic field is applied.

FIG. 6 is a schematic diagram showing the direction of magnetization that occurs when an external magnetic field is applied when the ferromagnetic metal film is divided into two magnetic domains.

FIG. 7 is a diagram showing the relationship between the MR ratio and the thickness of a nonmagnetic metal layer in a Co / Cu multilayer film.

FIG. 8 is a cross-sectional view showing one structural example of a multilayer film for a magnetoresistive effect element manufactured in an example.

FIG. 9 is a diagram showing a magnetization curve of a multilayer film for a magnetoresistive effect element obtained in an example.

FIG. 10 is a diagram showing a resistance change curve of a multilayer film for a magnetoresistive effect element obtained in an example.

FIG. 11 is a diagram showing a resistance change rate of the multilayer film for a magnetoresistive effect element obtained in the example.

FIG. 12 is an exploded view showing a first example of a conventional multilayer film for a magnetoresistive effect element.

FIG. 13 is a cross-sectional view showing a second example of a conventional multilayer film for a magnetoresistive effect element.

[Explanation of symbols]

 K substrate, J buffer layer, E basic unit, G laminated unit, H antiferromagnetic layer, 1, 3, 5, 7, 9, 11, 13 Ferromagnetic metal layer, 2, 4, 6, 8, 10, 12 Non-magnetic metal layer, a antiferromagnetically coupled unit, b weakly ferromagnetically coupled unit, d backward antiferromagnetically coupled unit, e backwardly weakly ferromagnetically coupled unit,

Front page continuation (72) Inventor Naoya Hasegawa 1-7 Yukiya Otsuka-cho, Ota-ku, Tokyo Alps Electric Co., Ltd.

Claims (12)

[Claims] 1. An antiferromagnetic coupling unit, which is antiferromagnetically coupled by laminating a nonmagnetic metal layer between a plurality of ferromagnetic metal layers, and a ferromagnetic metal between the plurality of nonmagnetic metal layers. A multilayer film for a magnetoresistive element, characterized in that the antiferromagnetic coupling unit and the weak ferromagnetic coupling unit weakly ferromagnetically coupled by laminating the layers are laminated on a substrate. 2. An antiferromagnetic coupling unit antiferromagnetically coupled by stacking a plurality of nonmagnetic metal layers between a plurality of ferromagnetic metal layers on the weak ferromagnetic coupling unit, A ferromagnetic metal layer is sandwiched between a plurality of nonmagnetic metal layers to form a weakly ferromagnetically coupled unit that is weakly ferromagnetically coupled to the antiferromagnetically coupled unit. The multilayer film for a magnetoresistive effect element according to claim 1. 3. The ferromagnetic metal layer comprises Co, NiFe alloy,
3. The magnetoresistive effect element according to claim 1 or 2, wherein the non-magnetic metal layer is made of at least one selected from a CoFeNi alloy, and the non-magnetic metal layer is made of at least one selected from Au, Ag, and Cu. Multilayer film. 4. The multilayer film for a magnetoresistive effect element according to claim 1, wherein an antiferromagnetic layer is added to at least one of the uppermost layer and the lowermost layer of the laminated film. A characteristic multilayer film for a magnetoresistive effect element. 5. The multilayer film for a magnetoresistive effect element according to claim 4, wherein the antiferromagnetic layer is FeMn, NiO or NiM.
A multi-layer film for a magnetoresistive effect element, comprising at least one selected from n. 6. The multilayer film for a magnetoresistive effect element according to claim 1, wherein a high coercive force magnetic layer made of a hard magnetic material is provided on at least one of an uppermost layer and a lowermost layer of the laminated film. A multilayer film for a magnetoresistive effect element, which is characterized by being added. 7. The high coercive force magnetic layer according to claim 6,
Cr alloy, CoCrTa alloy, CoCrNi alloy, Co
A multilayer film for a magnetoresistive effect element, comprising at least one selected from a CrMo alloy and a CoPt alloy. 8. The multilayer film for a magnetoresistive effect element according to claim 1, wherein the ferromagnetic metal layer has a thickness of 1 or less.
The thickness of the non-magnetic metal layer in the antiferromagnetic coupling unit is in the range of 7 to 11 angstroms, and the thickness of the other non-magnetic metal layer is in the range of 20 to 50 angstroms. A multilayer film for a magnetoresistive effect element, characterized in that 9. The multi-layer film for a magnetoresistive effect element according to claim 2, wherein the bottommost antiferromagnetic coupling unit is provided with two ferromagnetic metal layers. 3. A multilayer film for a magnetoresistive effect element, comprising: three ferromagnetic metal layers, and a plurality of alternating anti-ferromagnetic coupling units and weak-weak ferromagnetic coupling units are alternately laminated. 10. The multilayer film for a magnetoresistive effect element according to claim 1, wherein the electric resistance rapidly increases when the external magnetic field is low, and the electric resistance is gentle when the external magnetic field is higher. A multilayer film for a magnetoresistive effect element, which is characterized by exhibiting a characteristic of decreasing in 11. An antiferromagnetic coupling unit in which a nonmagnetic metal layer is sandwiched between a plurality of ferromagnetic metal layers to form an antiferromagnetic coupling unit, and a ferromagnetic metal layer is sandwiched between a plurality of nonmagnetic metal layers. A weak ferromagnetic coupling unit is formed by weakly ferromagnetically coupling with the antiferromagnetic coupling unit, both units are laminated, and the magnetization direction of the ferromagnetic metal layer in the weak ferromagnetic coupling unit is adjusted to an external magnetic field. A method for adjusting the magnetization of a magnetic layer, which is changeable. 12. The method of adjusting the magnetization of a magnetic layer according to claim 11, wherein a laminated body including an antiferromagnetic coupling unit, a weak ferromagnetic coupling unit, a reversion antiferromagnetic coupling unit, and a reweak ferromagnetic coupling unit is provided. An antiferromagnetic layer or a high coercive force magnetic layer is additionally provided on at least one of the uppermost layer and the lowermost layer, and the ferromagnetic metal layer in contact with the antiferromagnetic layer or the high coercive force magnetic layer is formed into a single magnetic domain. A method of adjusting the magnetization of a magnetic layer, characterized in that.