JP3347534B2 - Magnetoresistance effect multilayer film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetoresistive multilayer film for a magnetoresistive element used for a magnetic head, a position sensor, a rotation sensor and the like.

[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.

In recent years, a phenomenon called a giant magnetoresistance effect has been discovered in multilayer thin films such as an Fe / Cr alternating laminated film or a Co / Cu alternating laminated film. 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 layers are coupled so that their magnetizations 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. Thus, 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. 9 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. 9 is configured by laminating a first magnetic layer 2, a nonmagnetic spacer 3, a second magnetic layer 4, and an antiferromagnetic layer 5 on a nonmagnetic substrate 1. The direction B of magnetization of the second magnetic layer 4 is fixed by magnetic exchange coupling by the antiferromagnetic layer 5, and the direction C of magnetization of the first magnetic layer 2 is set to the second direction when there is no applied magnetic field. Are oriented at right angles to the direction B of magnetization of the magnetic layer 4. However, since the direction C of magnetization of the first magnetic layer 2 is not fixed, the first magnetic layer 2 can be rotated by an external magnetic field. When an applied magnetic field h is added to the structure shown in FIG. 9, the first magnetic layer 2 is changed in accordance with the direction of the applied magnetic field h.
Is rotated as shown by the dotted arrow, and an angle difference occurs in the magnetization between the first magnetic layer 2 and the second magnetic layer 4, so that a resistance change occurs. The magnetic field can be detected.

Next, as another example of a magnetoresistive sensor 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. NiO antiferromagnetic layer 7 and Ni—Fe magnetic layer 8
And a nonmagnetic metal layer 9 of Cu and a magnetic layer 10 of Ni—Fe
, A nonmagnetic metal layer 11 of Cu, and a magnetic layer 1 of Ni—Fe
2 and a magnetoresistive sensor B having a structure in which an antiferromagnetic layer 13 of FeMn is sequentially laminated.

In the structure of this example, the antiferromagnetic layer 7,
The magnetization of the ferromagnetic metal layers 8 and 12 adjacent to them is fixed by 13, and the ferromagnetic metal layers 10 and 12 sandwiched between the ferromagnetic metal layers 8 and 12 via the nonmagnetic metal layers 9 and 11.
Is configured to be rotatable according to an external magnetic field.
In the case of the magnetoresistive sensor having the structure shown in FIG. 9 or FIG. 10, the electric resistance of the magnetoresistive sensor A and the magnetoresistive sensor B changes linearly with high sensitivity to a small change in the applied magnetic field. When a soft magnetic material such as Ni—Fe is used for the first magnetic layer 2, the soft magnetic characteristics can be used, and there are advantages such as a small hysteresis.

[0010]

However, in the magnetoresistive sensor having the structure shown in FIG. 9 or FIG. 10, the magnetization of the adjacent second magnetic layer 4 is fixed by the antiferromagnetic layer 5 of FeMn, or the upper and lower FeMn layers are fixed. And the antiferromagnetic layers 7 and 13 of NiO fix the magnetization of the ferromagnetic metal layers 8 and 12 therebetween and free the magnetization of the magnetic layer 10 between them. Ni-Fe (magnetic layer) that contributes to the temperature
There is a limitation that the number of interfaces of / Cu (nonmagnetic metal layer) cannot be increased, and there is a problem that the magnitude of the MR ratio is limited.
Further, F used as a constituent material of the antiferromagnetic layers 5 and 7
eMn has a disadvantageous problem in terms of corrosion resistance and environmental resistance.

Next, as a modified example of the magnetoresistive sensor having the structure shown in FIGS. 9 and 10, as shown in FIG.
A structure is known in which a nonmagnetic layer 16 of Cu, a hard magnetic material layer 17 of Co, a nonmagnetic layer 18 of Cu, and a soft magnetic material film 19 of Ni—Fe are repeatedly laminated on a glass substrate 15 a plurality of times. The magnetoresistive sensor having the structure shown in FIG. 11 utilizes the difference in coercive force between the hard magnetic material film 17 and the soft magnetic material film 19 to adjust the thickness of the non-magnetic layer 18 to a predetermined thickness. The magnetization directions of the layers 17 and 19 can be made parallel or antiparallel, and thereby a giant magnetoresistance effect can be obtained. The magnetoresistive sensor having this structure is characterized in that the number of layers can be freely changed, so that a larger MR ratio can be obtained than the magnetoresistive sensors having the structures shown in FIGS.

On the other hand, as a magnetoresistive sensor having another structure,
As shown in FIG. 12, a structure in which a Cu nonmagnetic layer 21 and a Co ferromagnetic layer 22 are alternately and repeatedly laminated on a substrate 20 is also known. In this case, in order to satisfy the sensitivity, an attempt has been made to appropriately reduce the magnetic interaction acting between the ferromagnetic layers by adjusting the thickness of the nonmagnetic layer of Cu. Even in the structure of this example, the number of laminations can be freely changed, so that there is a feature that a larger MR ratio can be obtained than the magnetic sensor having the structure shown in FIGS. In addition,
In the structure shown in FIG. 12, instead of Co, a Co—Fe alloy or C
A structure using an o-Fe-Ni alloy is also known.

However, the magnetoresistive sensor having the structure shown in FIG. 12 has a drawback that heat resistance is inferior and cannot be used when a temperature of 350 ° C. or more is recorded. For this reason, when used as a magnetoresistive sensor, the characteristics deteriorate when subjected to a heating process (for example, a hardening process of a resin) required for manufacturing the sensor or the head, and heat is generated by a load such as an electric current. If the heat is generated for a long time, the characteristics may be deteriorated. This is because the ferromagnetic layer 22
Is not mixed even when heated to a high temperature because of the tendency of phase separation with Cu, but the crystal grains constituting each layer are partially coarsened by heating, and the layer structure changes. It is presumed that. For example, as shown in FIG. 13, even when a nonmagnetic layer 21 of Cu and a ferromagnetic layer 22 of Co are sequentially stacked and each layer has a layered structure in which crystal grains are aggregated, each crystal grain is disordered by heating. Fig. 1
4 has a laminated structure of a nonmagnetic layer 21 ′ and a ferromagnetic layer 22 ′, in which a part of the coarsened ferromagnetic layer 22 ′ is interposed between crystal grains of the nonmagnetic layer 21. It is considered that the stacked structure collapses and the magnetoresistance effect is deteriorated due to such factors.

Next, the magnetoresistive sensor having the structure shown in FIG. 11 operates even in a low magnetic field and has an advantage of high sensitivity.
Since Cu and Cu belong to a system in which solid solution is easy to form a solid solution (easy to mix), heat resistance has a disadvantage that it is worse than that of the structure of FIG. In addition, since completely different materials such as Co and Ni-Fe are used for the magnetic layer, potentials at which conduction electrons are received are different at each layer interface, which causes scattering of conduction electrons, that is, a giant magnetoresistance effect. Since the scattering other than the contributing spin-dependent scattering increases, the MR ratio is
2 tends to be smaller than the magnetoresistive sensor having the structure shown in FIG.

The present invention has been made in view of the above circumstances, and has a high MR ratio by forming a multilayer structure capable of realizing a multilayer structure of magnetic layers which cannot be achieved by the conventional structure shown in FIG. 9 or FIG. It is an object of the present invention to provide a magnetoresistive multilayer film having excellent heat resistance by having a layer structure in which crystal grains are not likely to be coarsened while being obtained.

[0016]

According to a first aspect of the present invention, there is provided a magnetoresistance effect multilayer film comprising a multilayer film in which ferromagnetic layers and nonmagnetic layers are alternately stacked. The ferromagnetic layer is a soft magnetic film having a composition of XMZ, and the soft magnetic film is formed of a crystal grain of the element X having an average crystal grain size of 20 nm or less and a crystal grain of the element X. Precipitated in the world
Separated into a carbide or nitride of elemental M, wherein
In the ferromagnetic layer, the boundary between the ferromagnetic layer and the adjacent nonmagnetic layer
A surface of the element M adjacent to the nonmagnetic layer,
Is the one in which a nitride is present . Here, the element X represents one or more of Fe, Co, and Ni, and the element M represents Ti, Zr, Hf, V, Nb, Ta,
One or more of Mo and W;
Represents one or two of C and N. According to a second aspect of the present invention, in order to solve the above-mentioned problem, a plurality of magnetic unit layers provided with a low coercive force magnetic layer and a high coercive force magnetic layer sandwiching a nonmagnetic layer are laminated. The layer has a composition of XMZ, and precipitates at a crystal grain of the element X having an average crystal grain size of 20 nm or less and a grain boundary of the crystal grain of the element X.
Separated into a carbide or nitride of elemental M, wherein
In the ferromagnetic layer, the boundary between the ferromagnetic layer and the adjacent nonmagnetic layer
A surface of the element M adjacent to the nonmagnetic layer,
Is a nitride in which the high coercivity magnetic layer is made of the element X. However, the element X is Fe,
One or more of Co and Ni, and the element M
Represents one or more of Ti, Zr, Hf, V, Nb, Ta, Mo, and W, and the element Z represents one or two of C and N.

According to a third aspect of the present invention, in order to solve the above problem, at least a ferromagnetic layer whose magnetization direction is pinned and a ferromagnetic layer whose magnetization direction is made free include a nonmagnetic layer. A magnetoresistive effect multilayer film sandwiched therebetween, wherein the ferromagnetic layer in which the direction of magnetization is made free is XM-
Z is a low coercive force magnetic film having a composition of Z. The low coercive force magnetic film is composed of a crystal grain of an element X having an average crystal grain size of 20 nm or less and an element M precipitated at a grain boundary of the crystal grain of the element X. At the interface between the ferromagnetic layer in which the magnetization direction is made free in the ferromagnetic layer and the adjacent nonmagnetic layer, and the element M
Of carbides or nitrides. Here, the element X represents one or more of Fe, Co, and Ni, and the element M represents Ti, Zr, Hf, V,
One or more of Nb, Ta, Mo and W are shown, and the element Z shows one or two of C and N.

According to a fourth aspect of the present invention, the constituent elements of the nonmagnetic layer are partially segregated at the grain boundaries of the crystal grains of the element X according to the second aspect. The invention according to claim 5 is a contract
According to the soft magnetic film or Claim 2 according to Motomeko 1 or 3
The low coercivity magnetic layer has the following composition. X _100-ab M _a Z _b where the composition ratios a and b are atomic%, and 0.5 ≦ a ≦ 8, 0.5 ≦ b
It is assumed that the relationship of ≦ 10 is satisfied. According to a sixth aspect of the present invention, the composition ratio a, b of the fifth aspect is 1 ≦ a ≦
6. The relationship of 0.5 ≦ b ≦ 7 is satisfied.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION

"Operation" The ferromagnetic layer is composed of a multilayer film in which ferromagnetic layers and non-magnetic layers are alternately stacked, and the ferromagnetic layer is formed of XMZ, that is, Co (C
a soft magnetic film having a composition of o, Fe, Ni) -M- (C, N), wherein the soft magnetic film is composed of (Co, Fe, Ni) crystal grains having an average crystal grain size of 20 nm or less; When the structure is separated from the carbide or nitride of M, the ferromagnetic layers of the respective layers have different magnetization directions in the absence of a magnetic field, whereas the magnetization of the adjacent ferromagnetic layers in the state of applying a magnetic field is different. Are aligned, and a change in magnetoresistance occurs. Also, XMZ, that is, (Co, Fe, Ni) -M- (C,
In the case of a ferromagnetic layer having a composition of N), carbides or nitrides of the element M precipitate at the grain boundaries of the (Co, Fe, Ni) crystal grains and suppress the coarsening of the crystal grains. In addition, the soft magnetic characteristics of the ferromagnetic layer are not lost, and high sensitivity characteristics are exhibited. In addition, since the layer interface is not disturbed by coarsening of the grains, an excellent magnetoresistance effect is obtained, and the heat resistance is also increased.

A low coercive force magnetic layer and a high coercive force magnetic layer are provided with the nonmagnetic layer interposed therebetween, and the low coercive force magnetic layer is made of (Co, Fe,
Ni) -M- (C, N) with an average crystal grain size of 2
When the high coercivity magnetic layer is separated into (Co, Fe, Ni) crystal grains of 0 nm or less and carbides or nitrides of the element M, and the high coercivity magnetic layer is made of (Co, Fe, Ni), the nonmagnetic layer is sandwiched. The low coercive force magnetic layer and the high coercive force magnetic layer
o, Fe, Ni) -M- (C, N) or (Co,
Fe, Ni), and in each case a layer containing Co as a main component, a structure in which a low coercive force magnetic layer and a high coercive force magnetic layer are provided with a nonmagnetic layer interposed therebetween. An MR ratio higher than that of the conventional structure shown in FIG. 11 in which the material is provided can be obtained. In addition, the carbide or nitride of the element M suppresses the coarsening of the crystal grains of (Co, Fe, Ni) to suppress the coarsening of the crystal grains of the low coercive force magnetic layer itself. Since the coarsening of the crystal grains of the layer is also suppressed, the coarsening of the crystal grains of the low-coercivity magnetic layer and the nonmagnetic layer adjacent thereto is suppressed, and further, the coarsening of the crystal grains of the nonmagnetic layer is suppressed. Therefore, coarsening of crystal grains of the high coercivity magnetic layer adjacent to the nonmagnetic layer is also suppressed.

Next, at least a ferromagnetic layer in which the direction of magnetization is pinned and a ferromagnetic layer in which the direction of magnetization is made free are laminated with a magnetoresistance effect multilayer film sandwiching a nonmagnetic layer. The ferromagnetic layer in which the direction of the magnetization is set free is
A soft magnetic film having a composition of (Co, Fe, Ni) -M- (C, N), wherein the soft magnetic film comprises (Co, Fe, Ni) crystal grains having an average crystal grain size of 20 nm or less, If the structure is separated from the carbide or nitride of M, the magnetization direction of the ferromagnetic layer whose magnetization direction is set free changes with an external magnetic field with high sensitivity, so that the magnetoresistance effect can be obtained. .

At the grain boundaries of the (Co, Fe, Ni) crystal grains, carbides or nitrides of the element M which suppress the coarsening of the crystal grains are precipitated, so that the crystal of another adjacent layer is formed. Grain coarsening is also suppressed. Further, (Co, Fe, Ni)
In a configuration in which some of the constituent elements of the nonmagnetic layer are segregated at the grain boundaries of the crystal grains, the constituent elements of the nonmagnetic layer precipitate at the grain boundaries of the crystal grains, and the coercive force increases. However, since the crystal grains of the ferromagnetic layers constituting the low coercive force layer and the high coercive force layer are essentially crystal phases of the same composition, the potentials at which conduction electrons receive in both layers are the same, contributing to the giant magnetoresistance effect. Scattering other than the spin-dependent scattering, and the MR ratio can be increased.

Next, among the layers having the composition X—M—Z, X
Preferably, the composition is _100-ab M _a Z _b , in which case the composition ratios a and b are atomic%, and 0.5 ≦ a ≦ 8 and 0.5 ≦ b.
Those satisfying the relationship of ≦ 10 are preferred, and in this case, particularly excellent magnetic properties are obtained. Further, the composition ratio a, b
Is atomic%, and it is particularly preferable that the relationship of 1 ≦ a ≦ 6 and 0.5 ≦ b ≦ 7 is satisfied.

Hereinafter, the present invention will be described in more detail with reference to the drawings. FIG. 1 shows a first embodiment of a magnetoresistive multilayer film according to the present invention. In this example, a magnetoresistive multilayer film E comprises a nonmagnetic substrate 31 and a nonmagnetic layer 31 on a nonmagnetic substrate 30. A required number of layers 32 are repeatedly laminated.

The substrate 30 is made of glass, Si, Al
₂ O ₃ , TiC, SiC, sintered body of Al ₂ O ₃ and TiC,
It is formed from a non-magnetic material typified by Zn ferrite and the like. Note that a coating layer or a buffer layer may be appropriately provided on the upper surface of the substrate 30 for the purpose of removing irregularities or undulations on the upper surface of the substrate or for the purpose of improving the crystal coherence of a layer laminated thereon. good. In the example shown in FIG.
Although the first layer in contact with 0 is the nonmagnetic layer 31, the ferromagnetic layer 32 may be the first layer. The non-magnetic layer 31 includes:
It is made of a nonmagnetic material typified by Cu, Au, Ag, Ru or the like, and is formed to a thickness of 10 to 50 °. Here, if the thickness of the nonmagnetic film 31 is less than 10 °, the ferromagnetic layers are directly connected magnetically through pinholes or the like of the nonmagnetic layer 31. Too many conduction electrons shunt
It is not preferable because the ratio of passing through the nonmagnetic layer 31 without spin-dependent scattering increases and the MR ratio decreases.

The ferromagnetic layer 32 is made of a soft magnetic film made of an XMZ based alloy, and is preferably X _100-ab M _a Z _b
A composition having the following composition is preferable. Here, the element X is F
e, Co, or Ni, one or more of them, and the element M is Ti, Zr, Hf, V, Nb, Ta, Mo, W
Among them, one or two or more, and the element Z is C, N
One or two of them, and the composition ratios a and b are atomic%
It is preferable to satisfy the relationship of 0.5 ≦ a ≦ 8 and 0.5 ≦ b ≦ 10. Still further, the composition ratio a,
Those in which b is atomic% and satisfies the relationship of 1 ≦ a ≦ 6 and 0.5 ≦ b ≦ 7 are particularly preferable. The composition ratios a and b determine the concentration of carbide or nitride particles, and the range of a and b is determined by an appropriate carbide concentration or nitride concentration. That is, if the carbide concentration or the nitride concentration is too high, the carbide or nitride is conductive, but becomes a scattering source of conduction electrons (scattering other than spin-dependent scattering which does not contribute to the giant magnetoresistance effect), so that the MR ratio is high. If the carbide concentration or the nitride concentration is too low, the above-described effect of suppressing the growth of crystal grains is not sufficiently exhibited, which is not preferable. Therefore, considering these, a and b are preferably within the above ranges.

As shown in FIG. 1, the ferromagnetic layer 32 is made of (Co, Fe, Ni) -based crystal grains 32a and carbides or nitrides of the element M precipitated at the grain boundaries of the crystal grains 32a. The crystal grains 32a have a fine particle size of about 20 nm or less. The ferromagnetic layer 32 has the specific composition described above, particularly, the element M (Ti, Zr, Hf, V, N
b, Ta, Mo, W), and the presence of the carbide of the element M can make the Co, Fe, and Ni-based crystal grains 32a finer. Note that the presence of carbides in actual materials is determined by a transmission electron microscope (TE
M) can be easily confirmed.

Also, when the elements M and C are added together, the elements M and C are chemically bonded to form carbides of the element M. These carbides have good conductivity, so that the carbides which contribute to the giant magnetoresistance effect can be obtained. Relatively little to hinder electrons.

In order to obtain the magnetoresistive multilayer film E having the structure shown in FIG. 1, a nonmagnetic layer 31 'made of a nonmagnetic material and an XMZ nonmagnetic layer 31 are formed on a substrate 30 as shown in FIG. A required number of crystalline layers 32 'are sequentially laminated to form a laminate E'. In addition,
When the concentrations of M, C, and N are low, the amorphous layer 32 'becomes a mixed layer of crystalline and amorphous or a crystalline layer. In order to form each of the above-mentioned layers on the substrate 30, a general-purpose technique, for example, a thin film forming apparatus such as sputtering or vapor deposition can be used to prepare and form an alloy thin film. For example, as a film forming apparatus, a high frequency bipolar sputtering apparatus, DC sputtering, magnetron sputtering, tripolar sputtering, ion beam sputtering,
Opposing target type sputtering or the like can be used.
Co or Ni-Fe-C is used as a sputtering target.
A composite target or the like in which chips of Zr, Hf, Ta, C, etc. are arranged on an o-alloy target can be used.

As a method of adding C to the film,
A method in which graphite pellets are arranged on a target plate to form a composite target and then sputtered, or in a gas atmosphere in which a hydrocarbon gas such as methane is mixed with an inert gas such as Ar using a target containing no C. A reactive sputtering method for sputtering or the like can be used. In this reactive sputtering method, the control of the C concentration in the film is easy, so that a film excellent in a desired C concentration can be obtained. Since the XMZ layer formed by the film forming method as described above often contains an amorphous phase as it is formed, the layer is heated to be crystallized to precipitate fine crystal grains. Heat treatment is performed. This heat treatment can be performed by heating to 300 to 500 ° C., whereby the amorphous layer 3 in the laminate shown in FIG.
By crystallizing 2 ′ to form the ferromagnetic layer 32, the magnetoresistive multilayer film E shown in FIG. 1 can be obtained.

At the time of the above heat treatment, the (Co, Fe, Ni) based fine crystal grains 32a are present in the amorphous layer 32 '.
Are crystallized, and carbides or nitrides of the element M precipitate at the grain boundaries to form the ferromagnetic layer 32. The precipitation of the carbides or nitrides suppresses the coarsening of the crystal grains 32a. The coarsening of the crystal grains of the nonmagnetic layer 31 adjacent to the layer 32 is also suppressed. Further, since the grain growth of the nonmagnetic layer 32 can be suppressed, the grain growth of the nonmagnetic layer 21 ′ and the ferromagnetic layer 22 ′ as described above with reference to FIGS. Thereby, it is possible to prevent the formation of large irregularities at the interface between the non-magnetic layer 21 'and the ferromagnetic layer 22', thereby preventing the stacked structure from being collapsed.

In the magnetoresistive multilayer film E having the structure shown in FIG. 1, when the external magnetic field is zero, the ferromagnetic layers 32 vertically adjacent to each other with the nonmagnetic layer 31 interposed therebetween as shown in FIG.
Are magnetically coupled to each other in the opposite direction. When a predetermined external magnetic field H acts on the magnetoresistive multilayer film E as shown in FIG. 4, the magnetic coupling is broken. The magnetization directions of the upper and lower ferromagnetic layers 32 are aligned in parallel. At this time, the resistance changes due to the influence of the presence or absence of the external magnetic field. Therefore, by detecting the change in the resistance, it is possible to detect whether the magnetic field has acted.

Then, the magnetoresistive effect multilayer film E having the above-described structure is formed.
The ferromagnetic layer 32 of Co is the same as that of the conventional structure shown in FIG.
The ferromagnetic layer 22 has a crystal structure having crystal grains in the order of nanometers smaller than the ferromagnetic layer 22. Therefore, even if the same layer is mainly composed of Co, it is easier to make the layer softer than a mere Co ferromagnetic layer. It is. Therefore, the sensitivity can be improved so as to be sensitive to a low external magnetic field. In addition, since the heat treatment is performed as described above, the heat resistance is excellent, and a high MR ratio can be obtained even at a high temperature. Further, since the ferromagnetic layers 32 provided above and below the nonmagnetic layer 31 are ferromagnetic films containing Co as a main component, a giant magnetic layer is formed at the interface between the ferromagnetic layer 32 and the nonmagnetic layer 31. Since the potentials of the conduction electrons, which are considered to contribute to the resistance effect, become equal, factors other than the spin-dependent scattering of the conduction electrons are reduced, and a high MR ratio can be obtained.

FIG. 5 shows a second embodiment of the magnetoresistive multilayer film according to the present invention. The magnetoresistive multilayer film F of this embodiment comprises a high coercivity magnetic layer 41 on a nonmagnetic substrate 40. A plurality of laminated units 44 each including a nonmagnetic layer 42 and a low coercive force magnetic layer 43 are laminated via a nonmagnetic layer 45.

The substrate 40 is made of the same material as the substrate 30 of the first embodiment described above. The nonmagnetic layers 42 and 45 are made of a nonmagnetic material typified by Cu, Au, Ag, Ru or the like, and are formed to a thickness of 10 to 50 °. If the thickness of the nonmagnetic layers 42 and 45 is less than 10 °, the ferromagnetic layers are magnetically directly connected to each other through pinholes or the like of the nonmagnetic layers 42 and 45. The conduction electrons shunting the nonmagnetic layers 42 and 45 become too large,
Since the ratio of passing through the nonmagnetic layers 42 and 45 without spin-dependent scattering increases and the MR ratio decreases, it is not preferable.

The high coercivity magnetic layer 41 is made of a ferromagnetic material obtained by removing the elements M, C and N from the constituent elements of the ferromagnetic layer 32 used in the first embodiment. That is, (C
(o, Fe, Ni) -based crystal grains 41a. The crystal grains 41a are the same as the crystal grains 32 of the ferromagnetic layer 32 of the first embodiment.
different from a, the average crystal grain size in the film plane is 20 nm
As described above, since the micro-crystal is not microcrystallized, the high coercive force magnetic layer 41 becomes a hard magnetic layer.

The low coercivity magnetic layer 43 is made of the same material as the ferromagnetic layer 32 used in the first embodiment. That is, the low coercive force magnetic layer 43 is made of an XMZ soft magnetic film, and preferably has a composition of X _100-ab M _a Z _b . Here, the element X is Fe, C
o, one or more of Ni, and the element M
Represents one or two or more of Ti, Zr, Hf, V, Nb, Ta, Mo, and W; the element Z represents one or two of C and N; , b is atomic%,
It is preferable to satisfy the relation of 0.5 ≦ a ≦ 8 and 0.5 ≦ b ≦ 10. Further, the above composition ratios a and b
Is atomic%, and particularly preferably satisfies the relationship of 1 ≦ a ≦ 6 and 0.5 ≦ b ≦ 7. The low coercivity magnetic layer 43 includes:
As shown in FIG. 5, there is provided a structure comprising X-based, ie, Co (Fe, Ni) -based, crystal grains 43a and precipitates 43b of carbides or nitrides of the element M precipitated at the grain boundaries of the crystal grains 43a. The crystal grains 43a are fine with a grain size of about 20 nm or less. In the Co (Fe, Ni) -based crystal, a crystal containing Co as a main component does not originally have soft magnetism, but exhibits a sensitivity to a magnetic field due to the effect of fine crystallization in the order of nm.

As described above, in the structure shown in FIG. 5, since the high coercivity magnetic layer 41, the nonmagnetic layer 42 and the low coercivity magnetic layer 43 are laminated, the magnetization direction of the high coercivity magnetic layer 41 is It does not fluctuate easily depending on the external magnetic field to be detected,
On the other hand, the direction of magnetization of the low coercivity magnetic layer 43 changes according to the external magnetic field. Therefore, the state of parallel or antiparallel magnetization changes according to the strength of the external magnetic field, and a resistance change occurs. Therefore, an external magnetic field can be detected from this resistance change. In the high coercive force magnetic layer 41 and the low coercive force magnetic layer 43 provided with the nonmagnetic layer 42 interposed therebetween, the high coercive force magnetic layer 41 is made of a (Co, Fe, Ni) -based alloy, 43 is an XMZ based alloy, that is, (Co, Fe, N
i) Non-magnetic layer 42 made of -M- (C, N) alloy
The crystal grains of the layers located on both sides of the non-magnetic layer are (Co, Fe, Ni) crystal grains having the same composition, and therefore, compared to the conventional structure shown in FIG. Thus, the MR ratio can be increased. Further, in the configuration of this embodiment, since a layer containing Ni as a main component can be eliminated, the phenomenon that Ni mixes with the non-magnetic layer at a high temperature does not occur. Further, even if the carbide of the element M precipitated at the layer interface exists only on one side of the nonmagnetic layers 42 and 45, the effect of suppressing the grain growth of the nonmagnetic layers 42 and 45 is sufficient. And is more excellent in heat resistance than the conventional structure described above.

In order to obtain the magnetoresistive multilayer film F having the structure shown in FIG. 5 or FIG. 7, on the substrate 40 as shown in FIG.
(Co, Fe, Ni) or (Co, Fe, Ni)-(Cu,
Au, Ag, Ru) and Cu, Au, A
g, Ru, and a nonmagnetic layer 42 made of any one of (Co, F
A plurality of laminated units 44 ′ composed of an e, Ni) -M- (C, N) layer 43 ′ are laminated via a non-magnetic layer 45. (Co, Fe, Ni) -M- (C,
Since the N) layer 43 ′ often contains an amorphous phase as it is formed, this layer is heated at 300 to 500 ° C. to be crystallized and subjected to a heat treatment for precipitating fine crystal grains. By such heat treatment, the (Co, Fe, Ni) -M- (C, N) layer is crystallized in the same manner as in the previous example, and the magnetoresistive multilayer film F shown in FIG. 5 can be obtained.

FIG. 7 shows a third embodiment of the magnetoresistive multilayer film according to the present invention. The magnetoresistive multilayer film G of this embodiment has a high coercivity magnetic layer on a nonmagnetic substrate 40. 4
A plurality of laminated units 44 each including 1 ″, a nonmagnetic layer 42 and a low coercive magnetic layer 43 are laminated via a nonmagnetic layer 45.

The structure of this example is similar to the structure of the second embodiment described above, except that the structure of the high coercivity magnetic layer 41 "is different. 41 "is (Co, Fe, Ni)-(Cu, Au, Ag, R
u), specifically, a crystal grain 41a of a (Co, Fe, Ni) -based alloy and a non-crystal of any of Cu, Au, Ag, and Ru formed at the grain boundaries of these crystal grains 41a. And a magnetic phase 41c. Since other structures are the same as those of the second embodiment, the same portions are denoted by the same reference numerals and description of those portions will be omitted. In the structure of this example, non-magnetic elements such as Cu, Ag, Au, and Ru
Since it is insoluble in Co and Fe, it segregates at grain boundaries during heat treatment after film formation, and has an effect of increasing coercive force. In the structure as in the second example, since the crystal grains of (Co, Fe, Ni) are also small, the coercive force (Hc) does not increase so much, and (C
Although the coercive force difference between the layer having the composition of o, Fe, Ni) -M- (C, N) is not so large, the coercive force difference of this layer can be set large by segregation of the nonmagnetic element. M
The R ratio can be improved. In addition, the segregation of the non-magnetic metal at the grain boundaries also slows down the grain growth rate of the high coercivity magnetic layer 42 "and suppresses the coarsening of crystal grains, thereby improving heat resistance.

FIG. 8 shows a fourth embodiment of the magnetoresistive multilayer film according to the present invention. The magnetoresistive multilayer film J of this embodiment is made of NiO or the like on a nonmagnetic substrate 50. Antiferromagnetic layer 51, low coercivity magnetic layer 52, nonmagnetic layer 53, low coercivity magnetic layer 54, nonmagnetic layer 55, and low coercivity magnetic layer 5.
6 and an antiferromagnetic layer 57 made of FeMn or the like are sequentially laminated. The structure of this example is a structure obtained by developing the conventional structure described above with reference to FIG. 10, and the magnetization of the low coercivity magnetic layer 56 is pinned by the antiferromagnetic layer 57.
The magnetization of the low coercivity magnetic layer 52 is pinned by the antiferromagnetic layer 51, and the magnetization of the low coercivity magnetic layer 52 is pinned.
The direction of magnetization of the low coercivity magnetic layer 54 provided between the magnetic layers 56 via the nonmagnetic layers 53 and 55 is made free.

In the structure of this example, all of the low coercive force magnetic layers 52, 54, 56 are (Co, Fe, Ni) -M-
Since the magnetic layer has a composition of (C, N), the magnetization direction of the low coercivity magnetic layer 52 is pinned by the magnetic exchange coupling force of the antiferromagnetic layer 51, and the magnetic exchange of the antiferromagnetic layer 57 is performed. The direction of magnetization of the low coercivity magnetic layer 56 is pinned by the coupling force, and the direction of magnetization of the low coercivity magnetic layer 54 sandwiched between them is made free. A magnetic field can be detected. That is, according to the structure of this example, the direction of the magnetization of the low coercive force magnetic layer 54 is rotated by the application of the external magnetic field, thereby causing a change in the magnetoresistance and obtaining an excellent MR ratio.

Note that, also in this example, the low coercive force magnetic layer 5
2, 54 and 56 are made of a (Co, Fe, Ni) -M- (C, N) soft magnetic film, and have a composition of X _100-ab M
_a (C, N) _b is preferred. Here, the element M is Ti, Zr, Hf, V, Nb, Ta, Mo, W
Represents one or more elements selected from the group consisting of: a, b in atomic%, 0.5 ≦ a ≦ 8, 0.5 ≦ b ≦ 10
It is preferable that the following relationship be satisfied. Also,
Further, the composition ratios a and b are atomic%, and 1 ≦ a ≦ 6, 0.5
Those satisfying the relationship of ≦ b ≦ 7 are particularly preferable.

[0045]

As described above, the first aspect of the present invention comprises a multilayer film in which ferromagnetic layers and non-magnetic layers are alternately stacked, and the ferromagnetic layer is composed of (Co, Fe, Ni)-. M- (C,
N) is a soft magnetic film having a composition of
The average grain size 20nm following elements (Co, Fe, Ni) and grain, is separated into a carbide or nitride of the element X of the crystal grains of the grain boundaries is precipitated the elements M, the ferromagnetic layer
At the interface between the ferromagnetic layer and the adjacent nonmagnetic layer.
The carbide or nitride of the element M is adjacent to the magnetic layer.
With the structure that exists, the ferromagnetic layers of each layer have different magnetization directions in the absence of a magnetic field, whereas the magnetization directions of the adjacent ferromagnetic layers are aligned in the state where a magnetic field is applied, At that time, a magnetoresistance change occurs. Therefore, the magnetic field can be detected by detecting the change in the magnetic resistance. Further, if the ferromagnetic layer has a composition of (Co, Fe, Ni) -M- (C, N), the film is heat-treated and crystallized, so that the heat resistance is higher than that of the conventional one.

Further, (Co, Fe, Ni) -M- (C, N)
In the case of a ferromagnetic layer having the following composition, carbide or nitride of the element M precipitates at the grain boundaries of the (Co, Fe, Ni) crystal grains and suppresses the coarsening of the crystal grains. Even in the case of a magnetic material, the resistance is easily changed in a magnetic field lower than that of a conventional magnetoresistive film of a Co / Cu laminated type because the magnetic property is more easily changed than that of Co alone. A magnetoresistive multilayer film can be provided. The element M
Carbides or nitrides are (Co, Fe, Ni) crystal grains
Grain size of adjacent non-magnetic layer
Also suppresses the coarsening of the crystal grains of the adjacent non-magnetic layer.
Coarsening can be suppressed.

Next, according to a second aspect of the present invention, a low coercive force magnetic layer and a high coercive force magnetic layer are provided with a nonmagnetic layer interposed therebetween, and the low coercive force magnetic layer is formed of (Co, Fe, Ni)- M- (C,
(C) having an average crystal grain size of 20 nm or less.
o, Fe, Ni) crystal grains and carbides or nitrides of the element M, and the high coercivity magnetic layer is made of (Co, F).
e, Ni), the ferromagnetic crystals constituting the magnetic layer provided with the nonmagnetic layer interposed therebetween are all (Co, F)
e, Ni). In the case where both are alloys containing Co as a main component, a higher MR ratio can be obtained than in the conventional structure shown in FIG. 11 in which different materials are provided with a nonmagnetic layer interposed therebetween. . Further, in the case of a low coercive force magnetic layer having a composition of (Co, Fe, Ni) -M- (C, N), a precipitate of carbide or nitride of the element M has a composition of (Co, Fe, Ni). Precipitates at the grain boundaries of the crystal grains and suppresses the coarsening of the crystal grains, and the precipitates precipitated at the grain boundaries reduce the coarsening of the crystal grains of the low-coercivity magnetic layer, the non-magnetic layer and the high-coercivity magnetic layer. Suppress. As a result, a magnetoresistive multilayer film having high heat resistance and good sensitivity can be obtained.

Next, there is provided a magnetoresistive multilayer film comprising at least a ferromagnetic layer having a pinned magnetization direction, a ferromagnetic layer having a free magnetization direction, and a nonmagnetic layer. The ferromagnetic layer whose magnetization direction is set free is (C
o, Fe, Ni) -M- (C, N). This soft magnetic film has an average crystal grain size of 20 nm or less (C
If the structure is separated into crystal grains having the composition of (o, Fe, Ni) and carbides or nitrides of the element M, the direction of magnetization of the ferromagnetic layer whose magnetization direction is made free is controlled by an external magnetic field. Since it changes with high sensitivity, a good magnetoresistance effect can be obtained. In addition, if the ferromagnetic layer has a composition of (Co, Fe, Ni) -M- (C, N), a carbide or nitride of the element M has a grain boundary of crystal grains having a composition of (Co, Fe, Ni). Deposited on
Since the coarsening of the crystal grains is suppressed, even the same Co-based magnetic material is easily softened more than single Co, so that the resistance changes with high sensitivity in a low magnetic field, and the magnetoresistance with high sensitivity is obtained. An effect multilayer film can be provided.

Next, at the grain boundaries of the crystal grains having the composition (Co, Fe, Ni), an element M for suppressing the coarsening of the crystal grains is provided.
By precipitation of carbides or nitrides, the coarsening of the crystal grains of another adjacent layer is suppressed. Further, (Co,
If the constituent elements of the nonmagnetic layer are segregated at the grain boundaries of the crystal grains having the composition of Fe, Ni), the constituent elements of the nonmagnetic layer precipitate at the grain boundaries of the crystal grains. Increased coercive force and low coercive force (Co, Fe, Ni) -M- (C, N)
A coercive force difference with a layer having the following composition occurs, and the magnetoresistive effect multilayer film according to claim 2 which exhibits an excellent effect due to the coercive force difference is reliably obtained.

Next, (Co, Fe, Ni) -M- (C, N)
Among the layers having the following composition, it is preferable that the composition be X _100-ab M _a C _b , in which case the composition ratios a and b are atomic%.
It is preferable to satisfy the relationship of 0.5 ≦ a ≦ 8 and 0.5 ≦ b ≦ 10. In this case, particularly excellent soft magnetic characteristics with a low coercive force can be obtained. The composition ratios a and b are atomic%.
It is particularly preferable that the relationship of 1 ≦ a ≦ 6 and 0.5 ≦ b ≦ 7 is satisfied.

[Brief description of the drawings]

FIG. 1 is a sectional view of a first embodiment of a magnetoresistive multilayer film according to the present invention.

FIG. 2 is a sectional view showing a state before heat treatment of the multilayer film shown in FIG.

FIG. 3 is a diagram showing a magnetization direction of each layer in a state where no magnetic field is applied to the multilayer film shown in FIG. 1;

FIG. 4 is a diagram showing the direction of magnetization of each layer when a magnetic field is applied to the multilayer film shown in FIG. 1;

FIG. 5 is a sectional view of a second embodiment of the magnetoresistive multilayer film according to the present invention.

6 is a cross-sectional view showing a state before heat treatment of the multilayer film shown in FIG.

FIG. 7 is a sectional view of a third embodiment of the magnetoresistive multilayer film according to the present invention.

FIG. 8 is a sectional view of a fourth embodiment of the magnetoresistive multilayer film according to the present invention.

FIG. 9 is an exploded view showing a first example of a conventional multilayer film for a magnetoresistive element.

FIG. 10 is a sectional view showing a second example of a conventional multilayer film for a magnetoresistive element.

FIG. 11 is a sectional view showing a third example of a conventional multilayer film for a magnetoresistive element.

FIG. 12 is a cross-sectional view showing a fourth example of a conventional multilayer film for a magnetoresistive element.

13 is a cross-sectional view showing crystal grains of the multilayer film shown in FIG.

FIG. 14 is a cross-sectional view showing crystal grains after heat treatment of the multilayer film shown in FIG.

[Explanation of symbols]

 E, F, G, J Magnetoresistance multilayer film, 30, 40, 50 substrate, 31 non-magnetic layer, 32 ferromagnetic layer, 32a, 43a fine crystal grain, 32b, 43b precipitate, 41, 41 "high coercive force magnetism Layers, 42, 45 non-magnetic layer, 43 low coercivity magnetic layer, 44 laminated unit, 51, 57 antiferromagnetic layer, 52, 54, 56 low coercivity magnetic layer, 52a, 54a, 56a fine crystal grains, 52b, 54b, 56b precipitates, 53, 55 nonmagnetic layer.

Continuation of the front page (56) References JP-A-6-101000 (JP, A) JP-A-7-6915 (JP, A) JP-A-6-111252 (JP, A) JP-A-8-161711 (JP) JP-A-8-225871 (JP, A) JP-A-9-8380 (JP, A) JP-A-3-248507 (JP, A) JP-A-3-219407 (JP, A) 3-267338 (JP, A) JP-A-3-20444 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01L 43/08 G01R 33/09 G11B 5/39 H01F 10 / 08 JICST file (JOIS)

Claims (6)

(57) [Claims] 1. A magnetoresistive effect multilayer film comprising a multilayer film in which ferromagnetic layers and nonmagnetic layers are alternately stacked, wherein the ferromagnetic layer has a composition of XMZ. The soft magnetic film is composed of a crystal grain of the element X having an average crystal grain size of 20 nm or less and an element M precipitated at the grain boundary of the crystal grain of the element X.
And the carbide or nitride of the element M is present at the interface between the ferromagnetic layer and the adjacent nonmagnetic layer in the ferromagnetic layer, adjacent to the nonmagnetic layer. A magneto-resistance effect multilayer film characterized by the above-mentioned. Here, the element X represents one or more of Fe, Co, and Ni, and the element M represents Ti, Zr, Hf, V,
One or more of Nb, Ta, Mo and W are shown, and the element Z shows one or two of C and N. 2. A magnetic unit layer comprising a low coercive force magnetic layer and a high coercive force magnetic layer provided with a nonmagnetic layer interposed therebetween, wherein the low coercive force magnetic layer has a composition of XMZ. Having a mean crystal grain size of 20 nm or less, and separated into carbides or nitrides of the element M precipitated at the grain boundaries of the crystal grains of the element X, in the low coercive force magnetic layer. wherein the interface between the non-magnetic layer adjacent to the low-coercivity magnetic layer adjacent to the nonmagnetic layer will be present carbides or nitrides of the element M in the high coercivity magnetic layer, in that it consists of element X Characteristic magnetoresistive multilayer film. However, the element X is F
e, Co, or Ni, one or more of them, and the element M is Ti, Zr, Hf, V, Nb, Ta, Mo, W
Among them, one or two or more, and the element Z is C, N
Among them, one or two types are shown. 3. A ferromagnetic layer having at least a pinned magnetization direction and a ferromagnetic layer having a magnetization direction set free.
A magneto-resistance effect multilayer film laminated with a non-magnetic layer interposed therebetween, wherein the ferromagnetic layer whose magnetization direction is made free is X
A soft magnetic film having a composition of -MZ, wherein the soft magnetic film is composed of a crystal grain of the element X having an average crystal grain size of 20 nm or less, and a carbide of the element M precipitated at a grain boundary of the crystal grain of the element X. Or, it is separated into nitride and the magnetization direction in the ferromagnetic layer.
A magnetoresistive multilayer film, wherein a carbide or a nitride of the element M is present adjacent to the nonmagnetic layer at the interface between the ferromagnetic layer whose magnetization has been released and the adjacent nonmagnetic layer. However, the element X is one of Fe, Co, and Ni.
Represents a species or two or more species, and the element M is Ti, Zr, H
One or more of f, V, Nb, Ta, Mo, and W are shown, and the element Z represents one or two of C and N. 4. The magnetoresistive multilayer film according to claim 2, wherein a part of the constituent elements of the nonmagnetic layer is segregated at the grain boundaries of the crystal grains of the element X. 5. The soft magnetic film according to claim 1, or the low coercive force magnetic layer according to claim 2 has the following composition: Magnetoresistive effect multilayer film. _{X 100-a-b M a} Z b where composition ratios a, b in atomic%, 0.5 ≦ a ≦ 8,0.5 ≦ b
It is assumed that the relationship of ≦ 10 is satisfied. 6. The composition ratio a, b is atomic% and 1 ≦ a ≦ 6, 0.
6. The magnetoresistive multilayer film according to claim 5, wherein a relationship of 5 ≦ b ≦ 7 is satisfied.