JP3264600B2 - Multilayer film for magnetoresistive element and method for adjusting magnetization of magnetic layer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetic head, the position sensor, relates to a multilayer film for a magnetic resistance effect element used in the rotation sensor.

[0002]

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

[0003] In recent years, a phenomenon called giant magnetoresistive effect is caused by the Fe / Cr alternately laminated film or the Co / C
It has been found in multilayer thin films such as u-alternate stacked films. In these multilayer thin films, the magnetization of each ferromagnetic metal layer made of Fe or Co causes a magnetic interaction via a non-magnetic metal layer made of Cr, Cu, or the like, and the upper and lower ferromagnetic metal layers are stacked. The magnetizations of the layers are coupled to remain antiparallel in the absence of an external magnetic field. That is, in these structures, the ferromagnetic metal layers alternately stacked via the non-magnetic metal layer are stacked with the direction of magnetization directed in the opposite direction for each layer. In these structures, when an appropriate external magnetic field is applied, the direction of magnetization of each ferromagnetic metal layer changes so as to be aligned in the same direction.

In the above structure, when the magnetization of each ferromagnetic metal layer is in the antiparallel state and in the parallel state, the interface between the Fe ferromagnetic metal layer and the Cr nonmagnetic metal layer or the Co ferromagnetic metal layer It is said that the way in which conduction electrons are scattered at the interface of the Cu non-magnetic metal layer differs depending on the spin of conduction electrons. Therefore, based on this mechanism, when the direction of magnetization of each ferromagnetic metal layer is in an anti-parallel state, the electric resistance is high, and when it is in a parallel state, the electric resistance is low, and the resistance change rate exceeds the conventional permalloy thin film, A so-called giant magnetoresistance effect occurs. As described above, these multilayer thin films are fundamentally different from the conventional single-layer thin film of Ni—Fe.
It has an R generation mechanism.

However, in these multilayer films, since the magnetic interaction between the ferromagnetic metal layers that acts to make the magnetization directions of the ferromagnetic metal layers antiparallel is too strong, There is a problem that an extremely large external magnetic field must be applied to make the magnetization directions parallel to each other. 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 an apparatus for detecting 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 nonmagnetic 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 increased. It seems effective to control the relative direction of the magnetization of the magnetic metal layer by a method different from the magnetic interaction. Conventionally, an antiferromagnetic layer such as FeMn is provided as such a relative magnetization direction control technique to fix the magnetization direction of one ferromagnetic metal layer and to set the magnetization direction of this ferromagnetic metal layer. There has been proposed a technology in which the device is configured to be hard to move with respect to an external magnetic field, and configured to be able to freely move the direction of magnetization of the other ferromagnetic metal layer, thereby enabling operation with a minute magnetic field.

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

When an applied magnetic field h is added to the structure shown in FIG. 12, the first magnetic layer 31 is changed according to the direction of the applied magnetic field h.
Is rotated as indicated by the dotted arrow, and a difference in direction occurs in the magnetization between the first magnetic layer 31 and the second magnetic layer 33, so that a resistance change occurs. Thereby, the magnetic field can be detected.

Next, as another example of a magnetoresistive sensor B having a configuration 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. An antiferromagnetic layer 36 of NiO, a magnetic layer 37 of Ni—Fe, a nonmagnetic metal layer 38 of Cu,
Magnetic layer 39, Cu non-magnetic metal layer 40, Ni-F
A structure is known in which a magnetic layer 41 of e and an antiferromagnetic layer 42 of FeMn are sequentially stacked. In the structure of this example, the magnetizations of the ferromagnetic metal layers 37 and 41 adjacent thereto are fixed by the antiferromagnetic layers 36 and 42, 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 therebetween is rotatable in accordance with an external magnetic field.

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

[0011]

However, FIG.
2 or the magnetoresistive sensor having the structure shown in FIG.
The magnetization of the adjacent second magnetic layer 33 is fixed by the antiferromagnetic layer 34 of eMn, or the magnetization of the ferromagnetic metal layers 37, 41 between them by the upper and lower FeMn and NiO antiferromagnetic layers 36, 42. Is fixed and the magnetization of the magnetic layer 39 between them is free, so that Ni-
There is a restriction that the number of interfaces of Fe (magnetic layer) / Cu (non-magnetic metal layer) cannot be increased, and there is a problem that the magnitude of 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 at all. The antiferromagnetic layer 3
FeMn used as a constituent material of Nos. 4 and 36 has disadvantageous problems in terms of corrosion resistance and environmental resistance.

The present invention has been made in view of the above-described circumstances, and has a multilayer structure capable of realizing a multilayer structure of magnetic layers which cannot be achieved by the conventional structure shown in FIG. 12 or FIG. High MR ratios can be obtained, while at the same time, in some cases, corrosion resistance,
It is an object of the present invention to provide a multilayer film for a magnetoresistive effect element and a method for adjusting the magnetization of a magnetic layer, in which it is not necessary to use an antiferromagnetic material having a problem in terms of environmental resistance.

[0013]

According to the first aspect of the present invention, in order to achieve the above object, antiferromagnetic coupling is achieved by stacking a nonmagnetic 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 an antiferromagnetic coupling unit by laminating a ferromagnetic metal layer between a plurality of nonmagnetic metal layers, are stacked on a substrate. And the uppermost layer and the lowermost layer of the laminated film.
An antiferromagnetic layer is added to at least one of the layers . In addition, the present invention provides a method in which non-magnetic
Antiferromagnetically coupled by stacking conductive metal layers
Ferromagnetic coupling between the ferromagnetic coupling unit and multiple non-magnetic metal layers
Antiferromagnetic coupling unit
Weak ferromagnetic coupling unit with weak ferromagnetic coupling on substrate
In the laminated structure, a deferred antiferromagnetic unit antiferromagnetically coupled by laminating a plurality of nonmagnetic metal layers between a plurality of ferromagnetic metal layers on the weak ferromagnetic coupling unit. By stacking a ferromagnetic metal layer between a plurality of non-magnetic metal layers, the antiferromagnetic coupling unit and the weak ferromagnetic coupling unit weakly ferromagnetically coupled are each laminated one or more times. It can also be structured.

Next, in the above structure, the ferromagnetic metal layer is made of at least one selected from the group consisting of Co, NiFe alloy and CoFeNi alloy, and the nonmagnetic metal layer is made of Au, Ag and Cu.
Alternatively, it may be composed of one 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. Further, in the above-mentioned multilayer film for a magnetoresistive element, the antiferromagnetic layer may be made of one or more selected from FeMn, NiO, and NiMn.

Next, in the multilayer film for a magnetoresistive 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. Further, the high coercive force magnetic layer described above is made of Co
It may be composed of at least one selected from a Cr alloy, a CoCrTa alloy, and a CoPt alloy. Further, in the multilayer film for a magnetoresistive 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 in the range of 7 to 11 Å. Range, the thickness of the other nonmagnetic metal layer is 20 to
It may be formed in the range of 50 angstroms.

Next, in the multilayer film for a magnetoresistive element described above, the lowermost antiferromagnetic coupling unit is provided with two ferromagnetic metal layers, and the reverse antiferromagnetic coupling unit is provided with three ferromagnetic metal layers. A layer may be provided, and a plurality of antiferromagnetic coupling units and weak ferromagnetic coupling units may be alternately stacked .

Next, the present invention relates to the method of
Antiferromagnetic coupling by stacking nonmagnetic metal layers
Between the antiferromagnetic coupling unit and multiple non-magnetic metal layers
The antiferromagnetic coupling is achieved by stacking ferromagnetic metal layers
Weak ferromagnetic coupling unit with weak ferromagnetic coupling
Laminated on the substrate, in the weak ferromagnetic coupling unit.
Ferromagnetic metal layer is magnetized according to the external magnetic field
Reversible, and the antiferromagnetic coupling unit
Coupling unit and antiferromagnetic coupling unit and reversible ferromagnetism
The top and bottom layers of the laminate with the coupling unit
At least one of the antiferromagnetic layer and the high coercivity magnetic layer
One is additionally provided with an antiferromagnetic layer or high coercivity
That the ferromagnetic metal layer in contact with the conductive layer is
Features.

[0018]

In the present invention, since the antiferromagnetic coupling unit and the weak ferromagnetic coupling unit are stacked on the substrate, the direction of magnetization of the ferromagnetic metal layer in the antiferromagnetic coupling unit is fixed, The direction of magnetization of the ferromagnetic metal layer in the magnetic coupling unit can be rotated according to an external magnetic field. In the structure of the present invention, a large number of layers can be freely stacked repeatedly, so that a large number of interfaces between a ferromagnetic metal layer exhibiting a giant magnetoresistance effect and a nonmagnetic metal layer can be formed in the multilayer body. Therefore, a large MR ratio can be obtained.

Hereinafter, the present invention will be described in more detail. FIG. 1 shows a structural example of a 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 J is formed on a non-magnetic substrate K,
A large number of magnetic layers and non-magnetic metal layers are laminated thereon. The buffer layer J is an underlayer for adjusting the crystal orientation of the layer laminated thereon, and may be omitted in some cases.

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

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

In the laminated structure shown in FIG. 1, the ferromagnetic metal layers 1 and 3 are
An antiferromagnetic coupling unit a having a layer structure is formed, and the nonmagnetic metal layers 4 and 6 are stacked with the ferromagnetic metal layer 5 interposed therebetween to form a weak ferromagnetic coupling unit b. Here, the weak ferromagnetic coupling unit b is formed because the nonmagnetic metal layers 4 and 6 located above and below the ferromagnetic metal layer 5 are formed sufficiently thick. This is because the magnetic coupling force of the ferromagnetic metal layers 7 and 3 located above and below the metal layer 5 to the ferromagnetic metal layer 5 becomes weak.

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
And a non-magnetic metal layer 12, a ferromagnetic metal layer 13 and a non-magnetic metal layer 6 to form a weak ferromagnetic coupling unit e. Is formed thereon, and a ferromagnetic metal layer 7, a non-magnetic metal layer 8, a ferromagnetic metal layer 9, a non-magnetic metal layer 10, and a ferromagnetic metal layer 11 are stacked thereon to form a three-layer structure. A ferromagnetic coupling unit d is configured.

In the structure shown in FIG. 1, since the ferromagnetic metal layers 1 and 3 are laminated via the non-magnetic metal layer 2, antiferromagnetic coupling (AF coupling) is established, and the two-layer structure 1 antiferromagnetic coupling unit a, and the ferromagnetic metal layers 1 and 3
Is hard to move. Since the first weak ferromagnetic coupling unit b having weak ferromagnetic coupling is stacked on the first antiferromagnetic coupling unit a, the ferromagnetic metal layer 5 in this unit is It becomes a layer capable of reversing magnetization (a so-called free layer: indicated by a symbol F in FIG. 1) that is easily reversed by an external weak magnetic field. This allows
A difference occurs in the magnetization reversal behavior between the ferromagnetic metal layers 1 and 3 and the ferromagnetic metal layer 5, so that the conventional structure shown in FIGS.
Even without using an antiferromagnetic layer made of Mn, a film having good sensitivity and a large resistance change rate can be formed. Therefore, it is advantageous in terms of corrosion resistance and environmental resistance.

Next, the first weak ferromagnetic coupling unit b
Since the antiferromagnetic coupling unit d having a three-layer structure of ferromagnetic metal layers provided above has three ferromagnetic metal layers, the uppermost ferromagnetic metal layer 11 of the antiferromagnetic coupling unit d The magnetization and the magnetization of the lowermost ferromagnetic metal layer 7 are directed in the same direction as shown by the arrow in FIG. Therefore, the magnetization 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 no matter how many layers are stacked (even if the number n of stacked layers is increased). .

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

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
And a ferromagnetic metal layer 5 are laminated to form a basic unit E. 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 The magnetic metal layer 11, the nonmagnetic metal layer 12, and the ferromagnetic metal layer 13 are laminated to form a laminated unit G.
Has a structure in which two units are stacked on the basic unit E, but the number of stacked units G may be any number. If the number of 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 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 in which the magnetization is easily inverted.
The magnetizations of the layers 3 and 13 (so-called free layers) are both reversed from the state shown in FIG. Then, in this state, the electric resistance ρ of the entire laminate becomes larger than that of FIG.
Exhibits a giant magnetoresistance effect.

Next, a multilayer film for a magnetoresistive element having the structure shown in FIG. 1 can be easily formed by using a film forming apparatus such as a sputtering apparatus. If it is, a simple film forming apparatus having three types of targets can sufficiently form a film.

Next, FIG. 3 shows that 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 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. This structure has a structure in which the ferromagnetic metal layer 9 thereunder is made into a single magnetic domain by the uppermost antiferromagnetic layer 15. Further, the lowermost antiferromagnetic layer H
Thereby, the ferromagnetic metal layer 1 thereon is also made into a single magnetic domain. As shown in FIG. 4, the structure in which only the one ferromagnetic films 1 and 9 are in contact with the antiferromagnetic layer may be used instead of the antiferromagnetic coupling unit.

The structure of this example aims at increasing the rate of change in resistance. Usually, in a structure in which magnetic layers are stacked, a film constituting each magnetic layer constitutes a plurality of magnetic domains in the film plane, and the magnetic domains are energetically stable while having different magnetization directions among the magnetic domains. I do. Therefore, even when the structure of FIG. 1 is applied, the entire magnetic layer is not divided into a single magnetic domain but divided into a plurality of magnetic domains. As a result, only about half the area within the film surface contributes to the giant magnetoresistance change. The case is conceivable. In order to improve this, the structure shown in FIG. 3 or FIG. 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, the single magnetic domain is formed. Ferromagnetic metal layers 9 and 1
On the other hand, the other ferromagnetic metal layers are also weakly magnetically and ferromagnetically coupled, so that the other ferromagnetic metal layers are also sequentially converted into single magnetic domains.

If this single domain action is utilized, the uppermost layer or the lowermost layer is not limited to the antiferromagnetic layer, but may be a hard magnetic material layer, for example. As the hard magnetic material layer, 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 divided into two magnetic domains when one ferromagnetic metal layer 13 is viewed from above, arrows O and Q
As shown in (1), magnetizations in different directions are formed and become stable in terms of magnetic energy, and accordingly, the antiferromagnetic coupling unit d
The magnetization directions of the upper and lower ferromagnetic metal layers are as indicated by arrows P and R for each magnetic domain. When a magnetic field indicated by a rightward arrow X is applied to the ferromagnetic metal layer 13 in this state as shown in FIG. 6, the relative direction of the magnetization of the upper half magnetic domain of the ferromagnetic metal layer 13 does not change, and the lower half does not change. Only the relative direction of magnetization of the magnetic domain changes, and this portion contributes to the giant magnetoresistance effect. Therefore, only a half area of the ferromagnetic metal layer 13 contributes to the giant magnetoresistance effect, so that the MR ratio does not increase. Therefore, in order to solve this problem, the ferromagnetic metal layer 9 may be formed into a single magnetic domain by providing the antiferromagnetic layer 15 as in the above structure. Similarly, the lowermost antiferromagnetic layer H may be provided to form the ferromagnetic layers 1 and 9 into a single magnetic domain.

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

FIG. 7 is a graph showing the M / M ratio 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 experimental data which showed the change of R ratio. When the thickness of the Cu layer is 9 angstroms and 20 angstroms, the Co layer is in an antiferromagnetic coupling state, and the state where the MR change is large is apparent. In the structure of the present invention, since strong antiferromagnetic coupling is required between the Co—Co layers in the antiferromagnetic coupling units a and d, the nonmagnetic metal layers 2, 8, and 10 of the structure shown in FIG. The thickness is preferably in the range of 7 to 11 angstroms, utilizing the maximum peak of 9 angstroms in FIG.

Further, 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 a thickness such that weak ferromagnetic coupling is achieved. When the nonmagnetic metal layers 4, 6, and 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 become in-plane. Therefore, the magnetic field has a plurality of magnetic domains, and the state is stabilized with the plurality of magnetic domains. In this case, the area of the ferromagnetic metal layer for exhibiting the giant magnetoresistance effect when an external magnetic field is applied is reduced by half, as in the case described above with reference to FIGS. Furthermore, when the ferromagnetic metal layer is divided into a plurality of magnetic domains, it has a domain wall. When the ferromagnetic metal layer has a domain wall, it causes Barkhausen noise when the ferromagnetic metal layer is inverted by a weak external magnetic field.

From the above, the nonmagnetic metal layers 4, 6, 1
2 must not be too thick, and strong exchange coupling hinders easy magnetization reversal. Therefore, the thickness of the nonmagnetic metal layers 4, 6, 12 is
Preferably, the thickness is between 20 and 50 angstroms, more preferably between 25 and 30 angstroms.

Next, regarding the thicknesses of the ferromagnetic metal layers 1, 3, 5, and 7, a multilayer film having a multilayer structure as in the present invention is required to have a sharp interface between each layer. It is desirable that the layers have good orientation and have coherent crystal bonding between the layers. For this reason, if the thickness is too small, an island state with poor continuity of the film is obtained, and if the thickness is too large, the unevenness of the interface increases toward the upper layer of the laminate, which is not preferable. Therefore, a range of 10 to 50 angstroms is preferable, and a range of 15 to 30 angstroms is more preferable.

The thickness of each layer described above is Co /
According to experimental data of a Cu multilayer film, the nonmagnetic metal layer is Cu, the ferromagnetic metal layer is Co, a NiFe alloy,
In the case of the CoNiFe alloy, it was confirmed that the peak of 1 at the time of oscillation of the MR ratio was around 9 angstroms. However, in the case of materials of other combinations, the thickness of the first peak of the MR ratio was different. In the case of the material of the combination of the above, the thickness may be set to give the first peak value.
Therefore, it is preferable that the thickness of the nonmagnetic metal layer be in the range of 7 to 11 Å.

[0040]

Embodiments of the present invention will be described below with reference to the drawings. Using a high-frequency magnetron sputtering apparatus provided with each target of Fe, Co, and Cu, a substrate 20 shown in FIG.
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 stacked as shown in FIG. 8 to obtain a multilayer film for a magnetoresistive element. Sputtering conditions at the time of film formation are as follows.
0 W, Cu is 100 W, and Ar gas pressure is 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 Å for the Cu layer 25 in the weak ferromagnetic coupling unit.
0 angstrom.

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

Further, in contrast to this structure, the Fe buffer layer 2
In place of 1, a NiO layer having a thickness of 300 Å as an antiferromagnetic layer was provided and formed in a magnetic field.
The resistance change rate indicated by ΔR / R was 6.8%. Further, in a sample in which a 50 angstrom thick CoPt layer was formed instead of the NiO antiferromagnetic layer, the sample was magnetized and evaluated. As a result, the resistance change rate indicated by ΔR / R was 6.2%. showed that.

Next, on the structure shown in FIG. 8, one or more lamination units indicated by reference symbol G in FIG. 1 were laminated to prepare samples, and a test was conducted to evaluate the characteristics of each sample. This laminated unit G is composed 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 following formula. Note that all units of thickness indicated by numerical values in parentheses in the formula are Angstroms. 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, and 4.

In the structure represented by the above formula, n = 0
Is 134 Angstroms, n = 1
Is 272 Å, n = 2
Is 410 angstroms for n, 54 for n = 3
8 angstrom and 686 angstrom when n = 4. FIG. 11 shows the result of calculating the resistance change rate ΔR / R ₀ (where ΔR is a value defined in FIG. 10) of the multilayer film for the magnetoresistive element of each thickness described above. As is clear from FIG. 11, the value of ΔR / R ₀ tends to increase up to the repetition number n = 2, but the value of the rate of change in resistance obtained even with a laminated structure having a larger number tends to be saturated. It turned out that there was.

Next, Table 1 shows the results of measuring the characteristics of the multilayer film for a magnetoresistive element having the above-mentioned structure, which was prepared by appropriately changing the constituent materials of each layer. In Table 1, the value of ΔH indicates the amount of change in the magnetic field when ΔR is read, as shown in FIG. 10, and a smaller value is preferable because the rate of change in resistance becomes larger.

[0046]

[Table 1]

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

[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 coupling unit in which a ferromagnetic metal layer and a nonmagnetic metal layer are laminated. Since the coupling unit is stacked on the substrate, the magnetization direction of the ferromagnetic metal layer in the antiferromagnetic unit is fixed, and the magnetization direction of the ferromagnetic metal layer in the weak ferromagnetic unit is adjusted according to the external magnetic field. It becomes a structure that can be rotated. Therefore, a resistance change can be caused in a state in which the magnetization of the weak ferromagnetic unit is not rotated and in a state after the magnetization is rotated.
Since a giant magnetoresistance change is caused by 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 element exhibiting a large MR ratio. In addition, since the antiferromagnetic coupling unit and the weak ferromagnetic coupling unit can be stacked in a required number of layers, respectively, with respect to the above structure, by stacking a plurality of layers, a ferromagnetic layer caused by a giant magnetoresistance change can be obtained. The number of interfaces of the nonmagnetic layer can be increased, whereby a multilayer film for a magnetoresistive element having a higher MR ratio than that of the conventional structure can be obtained. In addition, antiferromagnetic coupling
The top of the laminated structure consisting of a knit and a weak ferromagnetic coupling unit
Providing an antiferromagnetic layer on at least one of the layer and the bottom layer
Makes the ferromagnetic metal layer in contact with the antiferromagnetic layer
Partitioning, which allows the ferromagnetic layer to have multiple domains.
Can be prevented from being formed. This is the top layer
If the lowermost ferromagnetic layer can be made into a single magnetic domain,
Other ferromagnetic layers that are magnetically coupled to the
To ensure a giant magnetoresistance effect over the entire area of each ferromagnetic layer.
Results in a large MR ratio
be able to.

As the ferromagnetic metal layer, specifically, C
o, one selected from NiFe alloy and CoFeNi alloy
More than one kind can be used, and specifically, one or more kinds selected from Au, Ag, and Cu can be used as the nonmagnetic metal layer.

As described above , specifically, FeMn, NiO, N
iMn or the like can be used.

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

Next, in the above structure, when a ferromagnetic metal layer and a non-magnetic metal layer are laminated, in order to surely weakly couple the ferromagnetic metal layers in the weak ferromagnetic coupling unit, an intervening layer is provided between them. The thickness of the nonmagnetic layer to be
It is preferable that the thickness be in the range of 0 Å. Further, in order to ensure antiferromagnetic coupling between the ferromagnetic metal layers in the antiferromagnetic coupling unit, the thickness of the nonmagnetic layer is preferably in the range of 7 to 11 angstroms. Further, in any case, the thickness of the ferromagnetic metal layer is in the range of 10 to 30 Å in order to stabilize the state of the interface and the film formation state of the laminated portion and adjust the crystal structure of each layer. Is preferred.

Next, by forming a 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. A multilayer film for a magnetoresistive element having a decreasing characteristic can be obtained, and by using the multilayer film for a magnetoresistive element having such characteristics, a magnetoresistive material which is sensitive to a low external magnetic field can be provided.

[Brief description of the 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.

FIG. 2 is a sectional view showing a state where an external magnetic field is applied to the structure shown in FIG. 1;

FIG. 3 shows a second example of the multilayer film for a magnetoresistive element according to the present invention.
It is sectional drawing which shows the structural example of.

FIG. 4 shows a third example of the multilayer film for a magnetoresistive effect element according to the present invention.
It is sectional drawing which shows the structural example of.

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 generated when a ferromagnetic metal film is divided into two magnetic domains and an external magnetic field is applied.

FIG. 7 is a diagram showing the relationship between the thickness of a nonmagnetic metal layer and the MR ratio 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 sectional view showing a second example of a conventional multilayer film for a magnetoresistive element.

[Explanation of symbols]

 K substrate, J buffer layer, E basic unit, G stacked unit, H antiferromagnetic layer, 1, 3, 5, 7, 9, 11, 13 ferromagnetic metal layer, 2, 4, 6, 8, 10, 12 Nonmagnetic metal layer, a antiferromagnetic coupling unit, b weak ferromagnetic coupling unit, d antiferromagnetic coupling unit, e reversible ferromagnetic coupling unit,

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naoya Hasegawa 1-7 Yukitani Otsuka-cho, Ota-ku, Tokyo Alps Electric Co., Ltd. (56) References JP-A-7-114710 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) G11B 5/39 G11B 5/127 H01F 10/28

Claims (10)

(57) [Claims] An anti-ferromagnetic coupling unit that is anti-ferromagnetically coupled by stacking a non-magnetic metal layer between a plurality of ferromagnetic metal layers, and a ferromagnetic metal between the plurality of non-magnetic metal layers By laminating the layers, a weak ferromagnetic coupling unit weakly ferromagnetically coupled with the antiferromagnetic coupling unit is laminated on a substrate to form a laminated film, and a small number of uppermost and lowermost layers of the laminated film are formed.
A multilayer film for a magnetoresistive element, wherein an antiferromagnetic layer is added to at least one of the layers. 2. A non-magnetic metal layer between a plurality of ferromagnetic metal layers.
Antiferromagnetic coupling with antiferromagnetic coupling by stacking
Metal unit and a ferromagnetic metal layer between the non-magnetic metal layers
The antiferromagnetic coupling unit is weakened by stacking
Ferromagnetically coupled weak ferromagnetic coupling unit stacked on substrate
A deferral antiferromagnetic coupling unit that is antiferromagnetically coupled by stacking a plurality of nonmagnetic metal layers between a plurality of ferromagnetic metal layers on the weak ferromagnetic coupling unit; The ferromagnetic coupling unit and the weak ferromagnetic coupling unit weakly ferromagnetically coupled by laminating a ferromagnetic metal layer between the magnetic metal layers are characterized by being laminated one or more times. magnetic resistance effect element for the multi-layer film you. 3. The ferromagnetic metal layer comprises Co, a NiFe alloy,
3. The magnetoresistive element according to claim 1, wherein the nonmagnetic metal layer is made of one or more selected from a CoFeNi alloy, and the nonmagnetic metal layer is made of one or more selected from Au, Ag, and Cu. Multilayer film. 4. The multilayer film for a magnetoresistive element according to claim 2 , wherein an antiferromagnetic layer is added to at least one of an uppermost layer and a lowermost layer of the laminated film. Multilayer film for a magnetoresistive element. 5. A method according to claim 1 or multilayer film for a magnetic resistance effect element according to 4, the antiferromagnetic layer, FeMn, Ni
A multilayer film for a magneto-resistance effect element, comprising at least one selected from O and NiMn. 6. The multilayer film for a magnetoresistive 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 multilayer film. A multilayer film for a magnetoresistive element, which is added. 7. The high coercive force magnetic layer according to claim 6, wherein
Cr alloy, CoCrTa alloy, CoCrNi alloy, Co
A multilayer film for a magnetoresistive element, comprising at least one selected from a CrMo alloy and a CoPt alloy. 8. The multilayer film for a magnetoresistive element according to claim 1, wherein the thickness of the ferromagnetic metal layer is 1
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 layers is in the range of 20 to 50 angstroms. A multilayer film for a magnetoresistive element, comprising: 9. The multilayer film for a magnetoresistive effect element according to claim 2, wherein the lowermost antiferromagnetic coupling unit includes two ferromagnetic metal layers, and the reverse antiferromagnetic coupling unit includes three ferromagnetic metal layers. A multilayer film for a magnetoresistive element, comprising: a ferromagnetic metal layer; and a plurality of alternating antiferromagnetic coupling units and weak ferromagnetic coupling units stacked alternately. 10. A non-magnetic metal between a plurality of ferromagnetic metal layers.
Antiferromagnetic coupled antiferromagnetically by stacking layers
Ferromagnetic metal between the coupling unit and multiple non-magnetic metal layers
By stacking layers, the antiferromagnetic coupling unit and
Weak ferromagnetic coupling unit with weak ferromagnetic coupling
The ferromagnetic gold in the weakly ferromagnetic coupling unit
The magnetization reversal of the metal layer is possible by adjusting the magnetization direction to the external magnetic field
And the antiferromagnetic coupling unit and the weak ferromagnetic coupling unit
Unit, antiferromagnetic coupling unit, and weak ferromagnetic coupling unit.
At least one of the uppermost layer and the lowermost layer of the laminate having the
Either antiferromagnetic layer or high coercivity magnetic layer added
In contact with the antiferromagnetic layer or the high coercivity magnetic layer
Characterized in that the ferromagnetic metal layer has a single magnetic domain.
Multilayer film for magnetoresistive element.