JPH1032357A - Magnetoresistance effect film and magnetoresistance effect element using the film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetoresistance effect film having high magnetic field sensitivity and a magnetoresistance effect element using the film by a method in which they are composed of the alloy layer, a non-magnetic layer and a soft magnetic layer consisting of a magnetic element and a non-magnetic element, on which spinodal decomposition is generated on a substrate. SOLUTION: An alloy layer 2, consisting of a spinodal-decomposed magnetic element and a non-magnetic element, is formed on a substrate 1, and a soft magnetic layer 4 is formed thereon through a non-magnetic layer 3. The alloy layer 2 has magnetic particles which are depositedly grown in uniaxial direction in parallel with the substrate 1, and also has a uniaxial magnetic anisotropy having the growing direction of easy magnetization axis. The magnetic particles, which are once deposited and grown, are not extinguished as long as the alloy alloy layer 2 is not fused, and the magnetic anisotropy once generated on the alloy layer 2 is very stable. When the magnetic particles become single magnetic domain particles by their progress and growth and their uniaxial magnetic anisotropic control becomes larger equal to the square of spontaneous magnetization, the coercive force when magnetic field is applied to the axis of easy magnetization becomes equal to the spontaneous magnetization. As a result, an artificial lattice film, having high magnetic field sensitivity, can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magneto-resistance effect film used for a magnetic sensor, a thin-film magnetic head, and the like, and a magneto-resistance effect element using the same.

[0002]

2. Description of the Related Art A magnetoresistive element utilizing a magnetoresistive effect in which the resistance changes according to an applied magnetic field is used for a magnetic field detecting sensor, a magnetic head and the like. Conventionally, a magnetic alloy thin film mainly made of permalloy has been used as a magnetoresistive element. This magnetoresistive effect element utilizes a difference in resistance generated depending on the relative angle between the current direction and the magnetization direction, but has a small magnetoresistance change of about 3 to 4%. Therefore, a material having a large magnetoresistance change is desired. On the other hand, in recent years, the following two types of new magnetoresistive films have attracted attention.

One is to separate a soft magnetic layer such as permalloy by a non-magnetic layer such as copper (Cu) and provide a magnetic layer (exchange bias layer) for applying an exchange bias magnetic field to one soft magnetic layer. This is a spin valve film having a structure in which the magnetization of a soft magnetic layer adjacent to it (called a pinned layer, whereas the other soft magnetic layer is called a free layer) is fixed in a fixed direction. The magnetoresistance effect of the spin-valve film is caused by the magnetization direction of the free layer and the magnetization direction of the fixed pinned layer changing from an antiparallel arrangement to a parallel arrangement by applying a magnetic field. It shows a near magnetoresistance change. An iron-manganese alloy, which is an antiferromagnetic material, has been used for the exchange bias layer from the beginning, but has a practical problem due to its low corrosion resistance and low blocking temperature. As a means for solving this problem, a method using nickel oxide which is an oxide antiferromagnetic material for the exchange bias layer (Japanese Patent Application Laid-Open No. Hei 7-220246), a method using no exchange bias layer and providing a pin layer with a hard magnetic material A method using cobalt (Co), which is the 88th meeting of the Japan Society of Applied Magnetics, 88-2, January 1995, is known.
The latter method has a disadvantage that the magnetization direction of the pinned layer is changed by the influence of an external magnetic field of several tens of Oersteds to several hundreds of Oersteds because the coercive force of cobalt is small.

The other is cobalt (Co), iron (F)
This is an artificial lattice (multilayer) film in which a ferromagnetic material such as e) and a non-magnetic material such as copper (Cu) and chromium (Cr) are alternately laminated at a period of several nanometers. The magnetoresistance effect of the artificial lattice film is caused by the magnetization of the ferromagnetic layer adjacent via the nonmagnetic layer changing from the antiferromagnetic arrangement to the ferromagnetic arrangement by application of a magnetic field, and exceeds 10% at room temperature. 3 shows a change in magnetoresistance. As the artificial lattice film, (Co / Cu),
(Fe / Cr), (Permalloy / Cu / Co / Cu) and the like are known. However, in the artificial lattice film, the saturation magnetic field H _{S at} which the magnetoresistance is saturated is several kOe to 10 kOe, which is larger than several Oersted (Oe) of Permalloy.
It has been difficult to apply artificial lattice films to magnetic sensors and magnetic heads that require magnetic field sensitivity. Therefore, it has been proposed to introduce uniaxial magnetic anisotropy in the film plane as a means for reducing the saturation magnetic field while maintaining a large magnetoresistance effect change amount of the artificial lattice film. For example, F
A method in which a magnetic field of about 100 Oe is applied to the film surface by a permanent magnet during the formation of the e / Cr artificial lattice film to introduce uniaxial magnetic anisotropy in the film surface (Japanese Patent Laid-Open No. 4-212402).
And a method of introducing uniaxial magnetic anisotropy in a film surface by a shape magnetic anisotropy caused by a fine structure generated in a (110) oriented Fe / Cr artificial lattice film (Journal Applied Physics (J. Appl. Phys. 73, 3922, 1933
Year) is known. The latter method has a disadvantage that it can be applied only to the Fe / Cr artificial lattice film.

[0005]

As described above, a spin valve film using an iron-manganese alloy which is an antiferromagnetic material as an exchange bias layer, or a spin valve film using a hard magnetic material for a pin layer without an exchange bias layer. However, they have a drawback that they have low corrosion resistance and low blocking temperature, or change the magnetization direction of the pinned layer fixed by the influence of an external magnetic field, and are not suitable for commercialization. In addition, (110) -oriented Fe /
Although the Cr artificial lattice film can reduce the saturation magnetic field while maintaining a large magnetoresistance change, it has a problem that it cannot be applied to other artificial lattice films.

[0006]

An object of the present invention is to provide a magnetoresistive film having high magnetic field sensitivity and a magnetoresistive element using the same. Another object of the present invention is to provide a magnetoresistive effect film which is excellent in corrosion resistance and is not affected by an external magnetic field, and a magnetoresistive effect element using the same.

[0007]

As shown in FIG. 1, a first magnetoresistive film of the present invention comprises, on a substrate, an alloy layer composed of a magnetic element and a nonmagnetic element that have undergone spinodal decomposition,
It is composed of a non-magnetic layer and a soft magnetic layer. As shown in FIG. 2, the alloy composed of a magnetic element and a nonmagnetic element has magnetic particles that have been deposited and grown in the direction in which the magnetic field was applied by spinodal decomposition in a magnetic field parallel to the substrate surface. It has uniaxial magnetic anisotropy whose direction is the axis of easy magnetization and strong coercive force.

As shown in FIG. 3, the second magnetoresistive film of the present invention comprises a substrate, an alloy layer composed of a magnetic element and a nonmagnetic element that have undergone spinodal decomposition, and a magnetic layer and a nonmagnetic layer. It is composed of artificial lattice films that are alternately integrated.
As shown in FIG. 2, the alloy layer composed of a magnetic element and a non-magnetic element has magnetic particles that have been deposited and grown in the direction in which the magnetic field was applied by spinodal decomposition in a magnetic field parallel to the substrate surface. It has uniaxial magnetic anisotropy whose growth direction is the axis of easy magnetization.

As shown in FIG. 4, the third magnetoresistive film of the present invention is composed of a substrate and an artificial lattice film in which magnetic elements and nonmagnetic elements that cause spinodal decomposition are alternately laminated. The interface region between the magnetic layer and the non-magnetic layer is shown in FIG.
As shown in the figure, by spinodal decomposition in a magnetic field parallel to the substrate surface, it has magnetic particles that have been deposited and grown in the direction to which the magnetic field is applied, and has uniaxial magnetic anisotropy with this deposited growth direction as the axis of easy magnetization. .

Next, the operation of the present invention will be described.

When two immiscible elements such as cobalt (Co) and copper (Cu) are cooled from a mixed liquid state at a high temperature, they are separated into two phases and composition fluctuation starts to occur. This composition fluctuation has a minimum wavelength determined by the initial mixing ratio of the two elements and the temperature, and only the composition fluctuation having a wavelength larger than the minimum wavelength grows. Such a decomposition mechanism is particularly called spinodal decomposition. Spinodal decomposition also occurs in a solid-state reaction below the melting point, so if an alloy consisting of a magnetic element and a non-magnetic element that cause spinodal decomposition is annealed for a long time in a magnetic field, the magnetic element deposited due to composition fluctuations will be applied in the direction in which the magnetic field is applied. To form very long and thin axial magnetic particles. As the growth progresses, the shaft diameter becomes several nanometers (n
m), and the axial length becomes several microns (μm). Therefore, these magnetic fine particles have a very strong uniaxial magnetic anisotropy whose easy axis of magnetization is the growth direction, that is, the direction in which a magnetic field is applied during annealing. It becomes magnetic domain particles. The uniaxial anisotropy constant K (erg / cc) of a sufficiently elongated single domain magnetic particle is represented by K = πM _S ² where the spontaneous magnetization of the magnetic particle is M _S (emu / cc).
The maximum coercive force H expected in the easy axis direction
_c (Oe) is expressed as H _c =
The 2K / M _S = 2πM _S. The iron (Fe) or cobalt, since M _S to 10 ³ at room temperature (emu / cc), becomes sufficiently elongated single domain ^{particles, K~10 6 (erg / cc)} , H c ~1
0 ³ (Oe). Therefore, an alloy having magnetic fine particles deposited and grown uniaxially by spinodal decomposition has a strong coercive force and a large magnetic anisotropy. Alloy uniaxial anisotropy constant K _A (erg / cc) is, K _A ~ the average volume of the single domain magnetic particles v, the average density of ρ
It can be estimated as Kvρ.

Utilizing the above, the present invention has the following three functions.

First, when a soft magnetic layer is formed on a spinodal-decomposed alloy layer via a non-magnetic layer, the magnetization of the alloy layer is changed by a coercive force to a spin valve film fixed in the easy axis direction. it can. Since the coercive force of the spinodal-decomposed alloy layer can be very high, a stable spin valve film not affected by an external magnetic field can be obtained.

Secondly, when an artificial lattice film in which magnetic layers and non-magnetic layers are alternately laminated on the spinodal-decomposed alloy layer is formed, an induction in which the easy axis is the same as the easy axis direction of the alloy layer is obtained. Magnetic anisotropy also occurs in the artificial lattice film, and when a magnetic field is applied in the direction of the easy axis of magnetization, the saturation magnetic field of the magnetoresistance of the artificial lattice film is minimized. Thereby, an artificial lattice film having high magnetic field sensitivity can be obtained.

Third, an artificial lattice film in which magnetic elements and non-magnetic elements that cause spinodal decomposition are alternately laminated is formed and annealed in a magnetic field parallel to the interface between the magnetic layer and the non-magnetic layer. Then, the magnetic particles distributed mixed with the non-magnetic particles precipitate and grow in the direction of the magnetic field, and induced magnetic anisotropy having the direction of the magnetic field as the easy axis of magnetization is generated in the artificial lattice film. When a magnetic field is applied in the easy axis direction, the saturation magnetic field of the magnetoresistance of the artificial lattice film becomes the smallest. This utilizes the fact that the magnetic element and the non-magnetic element cannot be completely separated technically at the interface, and an alloy layer of the magnetic element and the non-magnetic element is interposed between the magnetic layer and the non-magnetic layer. The same effect can be obtained even if is formed thin.

[0016]

Next, a first embodiment of the present invention will be described in detail with reference to the drawings. 1 and 2
FIG. 2 is a schematic view of a magnetoresistive film according to the first embodiment of the present invention. In FIG. 1, an alloy layer 2 composed of a magnetic element and a non-magnetic element that have undergone spinodal decomposition is formed on a substrate 1, and a soft magnetic layer 4 is formed on the alloy layer 2 via a non-magnetic layer 3. As shown in FIG. 2, the alloy layer 2 has magnetic particles 5 precipitated and grown in a uniaxial direction parallel to the substrate 1 and has uniaxial magnetic anisotropy with the growth direction being the axis of easy magnetization. The magnetic particles 5 once deposited and grown do not disappear unless the alloy layer 2 is melted, so that the magnetic anisotropy once generated in the alloy layer 2 is very stable. When the precipitation growth proceeds and the magnetic particles 5 become single magnetic domain particles, and the uniaxial anisotropy constant becomes large enough to be equal to the square of the spontaneous magnetization, the coercive force when a magnetic field is applied in the direction of the easy axis of magnetization becomes smaller than the spontaneous magnetization. It becomes the size of. The element constituting the alloy layer 2 can be selected from a combination of a magnetic element and a non-magnetic element which cause spinodal decomposition and which has excellent corrosion resistance and large spontaneous magnetization of the precipitated magnetic particles 5. For example, Alnico 5 (14Ni-24C
o-8Al-3Cu-51Fe (wt%) alloy), 60Cu-20Ni-20Fe (wt%)
%) Alloy, a copper-cobalt alloy (Cu _1-X Co _X ), or the like. More specifically, a copper-cobalt alloy is preferred. This is because, because there are few constituent elements, in addition to easy film formation, the film itself has a magnetoresistive effect.

The spinodal decomposition of the alloy layer 2 is performed by forming the alloy layer 2 on the substrate 1 and then performing vacuum annealing at 200 ° C. to 800 ° C. in a magnetic field parallel to the substrate surface. It is better that the magnitude of the applied magnetic field is as large as possible, but 2 kOe is sufficient. The magnetic anisotropy generated in the alloy layer 2 by the spinodal decomposition increases as the annealing temperature is higher and the annealing time is longer, but the coercive force is maximized at a certain optimum annealing temperature and annealing time. This is considered to be because when the spinodal decomposition proceeds and the magnetic particles 5 become very small, the magnetization reversal of the magnetic particles 5 becomes easy (superparamagnetism) due to thermal disturbance. A soft magnetic layer 4 having a small coercive force is formed on the spinodal-decomposed alloy layer 2 via a non-magnetic layer 3, and a magnetic field is applied in the direction of the easy axis of magnetization of the alloy layer 2 to reduce the coercive force of the alloy layer 2. When the magnetic field is swept by the magnitude of, the magnetization direction of the soft magnetic layer 4 changes only while the magnetization of the alloy layer 2 is fixed in the easy axis direction. When the magnetization direction of the soft magnetic layer 4 in the magnetization direction of the alloy layer 2 changes from the antiparallel arrangement to the parallel arrangement by sweeping the magnetic field, the magnetic resistance decreases from the maximum to the minimum. The change in the magnetoresistance decreases as the annealing temperature of the alloy layer 2 is higher and the annealing time is longer. It is considered that this is because the unevenness of the surface of the alloy layer 2 becomes intense with the annealing, so that the flatness of the nonmagnetic layer 3 and the soft magnetic layer 4 formed on the alloy layer 2 is reduced.

Next, an example of the first embodiment of the present invention will be described in detail with reference to the drawings.

In the embodiment described below, an ion beam sputtering apparatus capable of annealing in a magnetic field as shown in FIG. 6 was used. In FIG. 6, a rotating target table 9 on which a copper target 8a is mounted is placed in a vacuum chamber of a sputtering apparatus.
a, cobalt target 8b and permalloy target 8
c, a rotating target table 9b, an ion gun 10
a, 10b, a partition plate 11, a substrate holder 12 on which a substrate is mounted, a heater 13 for heating a substrate, crystal oscillator film thickness meters 14a, 14b for monitoring a sputtering speed, and opening and closing of a sputtered particle beam from a sputter target. 15a and 15b, a vacuum gauge 16, an electron gun 17 for reflection high-speed electron beam diffraction (RHEED) for evaluating the surface structure of a film grown on the substrate, and a fluorescent screen 18; It is evacuated by the cryopump 20. Ultimate vacuum is 1 × 10 ^-7
The degree of vacuum at the time of torr and sputtering is 1 × 10 ⁻⁴ torr. A Helmholtz coil 21 for applying a magnetic field parallel to the substrate holder 12 is provided outside the vacuum chamber. Its maximum applicable magnetic field is 2 kilooersted (kOe). The degree of vacuum during annealing is 1 × 10 ⁻⁷ Torr, film formation other than annealing is performed at room temperature, and the film growth rate is 0.
1 nm / s. The magnetoresistance was measured by a direct current four-terminal method using a pattern produced by lithography and applying a magnetic field at room temperature in parallel to the film surface. The magnetization was measured at room temperature using a vibrating sample magnetometer.

[Embodiment 1] In this embodiment, a copper-cobalt alloy (Cu _1-x Co _x ) was used. The film formation of _Cu1-1XCo was performed by placing a cobalt chip on a copper target and performing sputtering, and the cobalt composition x was adjusted by changing the amount of the cobalt chip. After forming a 10 nm thick copper-cobalt alloy on a thermally oxidized silicon substrate,
Vacuum annealing was performed at 0 ° C. to 600 ° C. for 1 hour to 50 hours in a magnetic field (2 kOe) parallel to the substrate surface, and the induced magnetic anisotropy generated in the alloy layer was examined. The result was obtained. The magnitude of the induced magnetic anisotropy (uniaxial anisotropy constant) was measured by rotating a copper-cobalt alloy layer saturated and magnetized by a magnetic field of 20 kOe in the deposition direction of the cobalt particles in a magnetic field parallel to the substrate. It was determined from the amplitude of the torque curve. In FIG. 7, the anisotropy constants of Sample Nos. 6, 10, 12, 16, and 18 are obtained by setting the annealing time to 50 hours (3000 hours).
Min), it is considered that they are the maximum saturation values at each composition ratio. Composition ratio x of cobalt
Increases, the density of the precipitated magnetic fine particles also increases,
When x = 0.5, the anisotropy constant should be the largest, but it is actually the same value as when x = 0.3. This is considered to be because the axis diameter of the magnetic fine particles becomes larger when x = 0.5, and the shape magnetic anisotropy becomes smaller than that when x = 0.3. As can be seen by comparing sample numbers 3, 5, 9, 11, 15 and 17, the same annealing time (100
In (2), the higher the annealing temperature, the larger the anisotropy constant. This indicates that the higher the annealing temperature, the higher the deposition growth rate of the cobalt particles. When the annealing temperature is 400 ° C., even if the annealing time is extended to 50 hours, the anisotropy constant is not saturated, indicating that the deposition growth of cobalt particles is extremely slow.

EXAMPLE 2 The coercive force of the copper-cobalt alloy layer (Sample Nos. 1 to 18) shown in Example 1 when a magnetic field was applied in the direction of the axis of easy magnetization was examined. Such a result was obtained. According to the theory of the single domain magnetic fine particles, the coercive force is proportional to the anisotropy constant. As can be seen from FIG.
When the annealing temperature is 500 ° C. and the annealing time is 1000 minutes, the coercive force is the strongest, and the annealing temperature is 600 ° C. and the annealing time is 1
At 000 minutes, the coercive force decreased while the anisotropy constant was constant or increased. This is probably because the spinodal decomposition progressed and the magnetic particles became very small, so that the magnetic particles became in a state (superparamagnetism) where the magnetization reversal of the magnetic particles was likely to occur due to thermal disturbance. Sample No. 10
(Cobalt composition ratio x: 0.3, annealing temperature: 500 ° C., annealing time: 1000 minutes) Easy magnetization direction and in-plane direction perpendicular thereto (hard magnetization direction), easy magnetization direction and hard magnetization direction FIG. 9 shows a magnetization curve when a magnetic field is applied in the direction (45 ° direction). As can be seen from FIG.
The coercive force is the strongest in the easy axis direction.

Example 3 Copper was formed to a thickness of 2.5 nm on a copper-cobalt alloy layer that had undergone spinodal decomposition under the conditions of FIG.
Further, permalloy was formed to a thickness of 10 nm, and the sample dependence of the amount of change in magnetoresistance was examined. Magnetoresistance is measured by applying a magnetic field in the direction of the easy axis of magnetization of the copper-cobalt alloy layer and sweeping the magnetic field with a magnitude smaller than the coercive force of the alloy layer. Then, the change rate of the magnetoresistance when the magnetization direction of the permalloy film (free layer) changes from the parallel arrangement to the antiparallel arrangement was examined. The result is shown in FIG. 10 (sample number is 1 ′ corresponding to FIG. 7).
１８18 ′. ). Here, magnetoresistance change rate (%)
The ratio between the value and the R _S obtained by subtracting the resistance value R _S when the magnetic resistance is saturated from the resistance value R _O when the field 0 (R _O -
R _S ) × 100 / R _S. If R _O <R _S , take its absolute value. As can be seen from FIG. 10, the magnetoresistance change rate decreases as the annealing temperature increases and the annealing time increases. This is presumably because the surface irregularities of the copper-cobalt alloy layer become more intense with annealing, and the flatness of the non-magnetic layer and the soft magnetic layer formed on the alloy layer is reduced. However, the magnetoresistance ratio (3.5%) of Sample No. 10 ′ having the strongest coercive force is the value (4) obtained when a permalloy film is formed on a cobalt film as a hard magnetic material via a copper film.
%). Therefore, it is understood that a stable magnetoresistive (spin-valve) element which is not affected by an external magnetic field can be obtained from the magnetoresistive film.

Embodiment 4 In this embodiment, Alnico 5 (14Ni-24Co-8Al-3Cu-51F) was added to the alloy layer.
e (wt%) alloy). The Alnico 5 film was formed by sputtering an Alnico 5 target. Alnico 5 alloy 10nm on thermally oxidized silicon substrate
After the film is formed, 80 in a magnetic field (2 kOe) parallel to the substrate surface.
After performing vacuum annealing at 0 ° C. for 30 minutes,
Vacuum annealing was performed at 600 ° C. for 1 hour to 50 hours. At this time, when the induced magnetic anisotropy and the coercive force generated in the alloy layer were examined, the results shown in FIG. 11 were obtained. The magnitude of the induced magnetic anisotropy (uniaxial anisotropy constant) is determined by saturating an Alnico 5 alloy layer, which is saturated with a magnetic field of 20 kOe in the magnetic particle (iron-cobalt alloy) deposition direction, in a magnetic field parallel to the substrate. It was determined from the amplitude of the torque curve measured by rotating at. The coercive force was measured from a magnetization curve when a magnetic field was applied in the easy axis direction. As can be seen from FIG. 11, the higher the annealing temperature and the longer the annealing time, the larger the anisotropy constant and the coercive force, but the maximum value is only half or less as compared with that of the cobalt alloy layer. Alnico 5
Magnetization of precipitated particles of iron (cobalt alloy) (about 1700
Gauss) is larger than that of the cobalt alloy (1400 Gauss), so the anisotropy constant and coercive force should originally be large, but this is not the case because the precipitation density of the magnetic particles in the Alnico 5 alloy layer is almost the same. It is considered that the value is close to 1 so that the magnetic poles of adjacent magnetic particles are canceled out. As described above, in Alnico 5, since the content of the magnetic element in the alloy is determined, it is difficult to control the density of precipitated particles.

Example 5 Copper was formed to a thickness of 2.5 nm and permalloy was formed to a thickness of 10 nm on the Alnico 5 alloy layer spinodally decomposed under the conditions shown in FIG. Examined. In the magnetoresistance measurement, a magnetic field is applied in the direction of the easy axis of magnetization of the Alnico 5 alloy layer, and the magnetic field is swept by a magnitude equal to or smaller than the coercive force of the alloy layer.
Then, the change rate of the magnetoresistance when the magnetization direction of the Alnico 5 (pin layer) and the magnetization direction of the permalloy film (free layer) change from a parallel arrangement to an antiparallel arrangement was examined. The result is shown in FIG. 12 (sample number is 19 ′ corresponding to FIG. 11).
To 27 ′). Since the annealing temperature is higher than in Example 3, the rate of change in magnetoresistance at the maximum saturation magnetic field is smaller.

[Embodiment 6] In this embodiment, the alloy layer is
A Cu-20Ni-20Fe (wt%) alloy was used. 6
The film formation of 0Cu-20Ni-20Fe (wt%) alloy is as follows.
This was performed by sputtering a target of a 60Cu-20Ni-20Fe (wt%) alloy. After forming a 60 nm Cu-20Ni-20Fe (wt%) alloy on a thermally oxidized silicon substrate to a thickness of 10 nm, vacuum annealing is performed at 400 ° C. to 600 ° C. for 1 hour to 50 hours in a magnetic field (2 kOe) parallel to the substrate surface. Was. At this time, when the induced magnetic anisotropy and the coercive force generated in the alloy layer were examined, the results shown in FIG. 13 were obtained. The magnitude of the induced magnetic anisotropy (uniaxial anisotropy constant) is 2 in the precipitation direction of the magnetic particles (iron-nickel alloy).
60Cu- which is saturated by a magnetic field of 0 kOe
The 20Ni-20Fe (wt%) alloy layer was determined from the amplitude of the torque curve measured by rotation in a magnetic field parallel to the substrate. The coercive force was measured from a magnetization curve when a magnetic field was applied in the easy axis direction. In FIG. 13, the anisotropy constant of Sample No. 33 did not change even when the annealing time was extended to 50 hours (3000 minutes), and is considered to be the maximum saturation value. The maximum values of the anisotropy constant and the coercive force are much smaller than those of the first and fourth embodiments. This is because the deposited magnetic particles (iron nickel alloy) are originally soft magnetic materials,
It is considered that the magnetic particles are unlikely to have a single magnetic domain structure.

Next, a second embodiment of the present invention will be described in detail with reference to the drawings. FIG. 3 is a schematic diagram of a magnetoresistive film according to the second embodiment of the present invention. An alloy layer 2 composed of a magnetic element and a non-magnetic element that have undergone spinodal decomposition is formed on a substrate 1, and an artificial lattice film in which magnetic layers 6 and non-magnetic layers 7 are alternately stacked is formed thereon. . As shown in FIG. 2, the alloy layer 2 has magnetic particles 5 deposited and grown in a uniaxial direction parallel to the substrate 1, and has uniaxial magnetic anisotropy with the growth direction being an easy axis of magnetization. The magnetic layer 6 of the artificial lattice film formed on the alloy layer 2 has an induced magnetic anisotropy having an easy axis of magnetization in the same direction as that of the alloy layer 2, and when a magnetic field is applied in the easy axis direction, The magnetic field at which the magnetoresistance of the artificial lattice film saturates is minimized. The saturation magnetic field depends on the alloy layer 2
The larger the magnetic anisotropy of the alloy layer 2 becomes, the smaller the magnetic anisotropy becomes. This is considered to be because the higher the annealing temperature and the longer the annealing time, the more uneven the surface of the alloy layer 2 becomes, and the lower the flatness of the artificial lattice film formed on the alloy layer 2 becomes. . Although the amount of change in the magnetic resistance does not depend on the direction of the applied magnetic field, the saturation magnetic field is reduced by up to two orders of magnitude when the magnetic field is applied in the easy axis direction, compared to when the magnetic field is applied in the hard axis direction.

Next, an example of the second embodiment of the present invention will be described in detail. Example 7 A copper-cobalt alloy (Cu _1-x Co _x ) film was used as an alloy layer made of a magnetic element and a non-magnetic element that cause spinodal decomposition, as in the first embodiment. After forming a 10 nm-thick copper-cobalt alloy on a thermally oxidized silicon substrate, a sample was annealed in a magnetic field under the same conditions as in FIG. 7 (sample numbers are 1 ″ to 18 ″ corresponding to FIG. 7). On top of 2n
m of cobalt (Co) and 1 nm of copper (Cu) alternately 3
An artificial lattice (hereinafter referred to as [Co (2 nm) / Cu
(1nm)] referred to as _30. ) Formed. After performing saturation magnetization in the precipitation direction of cobalt particles with a magnetic field of 20 kOe, a magnetic field is applied in the direction of the easy axis of the induced magnetic anisotropy generated, and the magnetoresistance change rate and the sample dependence of the saturation magnetic field are examined. Was. The result is shown in FIG. As can be seen from FIG. 14, when the anisotropy constant is maximum (sample No. 10 ″, 1
2 ", 16" and 18 ") and the saturation field is minimized (5
0 Oe), the magnetoresistance change rate is larger when the annealing temperature is lower and the annealing time is shorter. This is because the higher the annealing temperature and the longer the annealing time, the more irregularities that occur on the surface of the copper-cobalt alloy layer during annealing become more severe, so the flatness of the artificial lattice film formed on the alloy layer is increased. It is considered that this is because the magnetic coupling between the Co layers of [Co (2 nm) / Cu (1 nm)] ₃₀ is weakened.
A magnetic field was applied in the easy axis direction of sample number 10 ″ (cobalt composition ratio x: 0.3, annealing temperature: 500 ° C., annealing time: 1000 minutes) and an in-plane direction perpendicular thereto (hard axis direction). FIG. 15 and FIG.
6 respectively. As can be seen from FIG. 16, the rate of change in magnetoresistance does not depend on the direction of the applied magnetic field, but the magnetic field at which the magnetoresistance saturates reflects the difference in magnetic anisotropy in FIG. In this case, the value is reduced by almost two orders of magnitude when applied in the direction of the hard magnetization axis.

Next, a third embodiment of the present invention will be described in detail with reference to the drawings. FIG. 4 is a schematic diagram of a magnetoresistive film according to the third embodiment of the present invention. An artificial lattice film in which magnetic layers 8 and nonmagnetic layers 9 are alternately stacked on a substrate 1 is formed by a combination of a magnetic element and a nonmagnetic element that cause spinodal decomposition. The interface 10 region between the magnetic layer 8 and the non-magnetic layer 9 in which spinodal decomposition has occurred is shown in FIG.
As shown in (1), the magnetic particles 5 have the uniaxial magnetic anisotropy in which the magnetic particles 5 are deposited and grown in a uniaxial direction parallel to the interface 10, and the growth direction is the easy axis of magnetization. As the magnetic element and the non-magnetic element that cause spinodal decomposition, those that exhibit a magnetoresistance effect when alternately stacked must be selected. For example, permalloy (Ni
-Fe) and copper (Cu), and cobalt (Co) and copper. More specifically, a combination of cobalt and copper that gives the largest amount of change in magnetoresistance when an artificial lattice is formed is preferable.

When the composition analysis of the layer cross section of the artificial lattice film is performed by using a transmission electron microscope for analysis, the region where the magnetic element and the non-magnetic element are mixed can be obtained no matter how ideal the film is formed. Is present in the vicinity of several angstroms at the interface 10 between the magnetic layer 8 and the non-magnetic layer 9. Therefore, when this artificial lattice film is vacuum-annealed at 400 ° C. to 600 ° C. in a magnetic field parallel to the substrate surface, the magnetic particles 5 are deposited and grown uniaxially in the region near the interface 10. It is better that the magnitude of the applied magnetic field is as large as possible, but 2 kOe is sufficient. Magnetic layer 8 of artificial lattice film
Generates an uniaxial magnetic anisotropy having an easy axis of magnetization in the same direction as the region near the interface 10, and when a magnetic field is applied in this easy axis direction, the magnetic field at which the magnetic resistance of the artificial lattice film saturates is minimized. . The saturation magnetic field decreases as the magnetic anisotropy increases, but the change in the magnetoresistance increases as the annealing temperature of the artificial lattice film is lower and the annealing time is shorter. This is presumably because the higher the annealing temperature and the longer the annealing time, the lower the flatness of the interface of the artificial lattice film. Although the amount of change in the magnetic resistance does not depend on the direction of the applied magnetic field, the saturation magnetic field is reduced by up to two orders of magnitude when the magnetic field is applied in the easy axis direction, compared to when the magnetic field is applied in the hard axis direction. When a thin alloy layer of a magnetic element and a non-magnetic element is formed between the magnetic layer 8 and the non-magnetic layer 9 of the superlattice film and subjected to spinodal decomposition, a larger uniaxial magnetic anisotropy is obtained than without the alloy layer. However, the amount of change in the magnetoresistance is small. This is presumably because the formation of the alloy layer weakens the magnetic coupling between the magnetic layers.

Next, an example of the third embodiment of the present invention will be described in detail. Example 8 As a combination of a magnetic element and a nonmagnetic element that cause spinodal decomposition, cobalt and copper having the maximum magnetoresistance effect when an artificial lattice was formed were employed.
2 nm of cobalt (Co) and 1 nm on a thermally oxidized silicon substrate
After forming an artificial lattice (hereinafter referred to as [Co (2 nm) / Cu (1 nm)] ₃₀ ) in which copper (Cu) having a thickness of 30 nm is alternately laminated 30 times, it is heated at 400 ° C. to 600 ° C. for 1 hour to 5 hours.
Vacuum annealing was performed for 0 hour in a magnetic field (2 kOe) parallel to the substrate surface, and the induced magnetic anisotropy generated in the artificial lattice film was examined. The result shown in FIG. 17 was obtained. The magnitude of the induced magnetic anisotropy (uniaxial anisotropy constant) is the torque measured by rotating an artificial lattice film, which is saturated and magnetized by a magnetic field of 20 kOe in the direction of deposition of cobalt particles, in a magnetic field parallel to the substrate. It was determined from the amplitude of the curve. As can be seen from FIG. 17, the magnetic anisotropy generated in the alloy layer by spinodal decomposition increases as the annealing temperature increases and the annealing time increases, and the maximum saturation value also increases with the spinodal decomposition of the copper-cobalt alloy layer. Same as 1 This is considered to be due to the fact that the precipitation region of the cobalt particles is limited to the region near the interface and that the interface is adjacent to the magnetic layer. Next, a magnetic field was applied in the direction of the easy axis of the uniaxial magnetic anisotropy, and the sample dependence of the magnetoresistance change rate and the saturation magnetic field was examined. FIG. 18 shows the result. As can be seen from FIG. 18, the saturation magnetic field becomes smaller as the annealing temperature is higher and the annealing time is longer, but the rate of change in magnetoresistance is reduced in proportion thereto. This is because the flatness of the interface decreases during annealing, and [Co (2 nm) / Cu (1
nm)] It is considered that this is because the magnetic coupling between the layers of Co of ₃₀ is weakened.

[0031]

The first effect is that an artificial lattice film (magnetoresistive film) having high magnetic field sensitivity and a magnetoresistive element using the same can be obtained. The reason is,
This is because magnetic particles anisotropically deposited and grown by spinodal decomposition have strong uniaxial magnetic anisotropy.

A second effect is that a spin valve film (magnetoresistive film) which is not affected by an external magnetic field and a magnetoresistive element using the same can be obtained.
The reason is that the magnetic single magnetic domain fine particles anisotropically deposited and grown by spinodal decomposition have a strong coercive force when a magnetic field is applied in the direction of the easy axis of magnetization.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a magnetoresistive effect film according to a first embodiment.

FIG. 2 is a schematic view showing a part of a magnetoresistive film according to the first embodiment.

FIG. 3 is a schematic diagram illustrating a magnetoresistive effect film according to a second embodiment.

FIG. 4 is a schematic diagram illustrating a magnetoresistive effect film according to a third embodiment.

FIG. 5 is a schematic view showing a part of a magnetoresistive film according to a third embodiment.

FIG. 6 is a schematic view of a sputtering apparatus used in an example.

FIG. 7 is a table showing characteristics of the magnetoresistive film in Example 1.

FIG. 8 is a table showing characteristics of a magnetoresistive film in Example 2.

FIG. 9 is a graph showing a magnetization curve of a magnetoresistive film in Example 2.

FIG. 10 is a table showing characteristics of a magnetoresistive film in Example 3.

FIG. 11 is a table showing characteristics of a magnetoresistive film in Example 4.

FIG. 12 is a table showing characteristics of a magnetoresistive film in Example 5.

FIG. 13 is a table showing characteristics of a magnetoresistive film in Example 6.

FIG. 14 is a table showing characteristics of a magnetoresistive film in Example 7.

FIG. 15 is a graph showing a magnetization curve of a magnetoresistive film in Example 7.

FIG. 16 is a graph showing a magnetoresistance curve of a magnetoresistance effect film in Example 7.

FIG. 17 is a table showing characteristics of the magnetoresistive film in Example 8.

FIG. 18 is a chart showing characteristics of a magnetoresistive film in Example 8.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate 2 Alloy layer 3 Nonmagnetic layer 4 Soft magnetic layer 5 Magnetic particle 6,8 Magnetic layer 7,9 Nonmagnetic layer 10 Interface between magnetic layer and nonmagnetic layer

Claims (4)

[Claims] An alloy layer having unidirectionally arranged needle-like magnetic particles deposited by spinodal decomposition is provided on a substrate, and a soft magnetic layer is laminated on the alloy layer via a non-magnetic layer. Characteristic magnetoresistive film. 2. An artificial layer comprising: an alloy layer having unidirectionally aligned needle-like magnetic particles deposited by spinodal decomposition provided on a substrate; and a magnetic layer and a nonmagnetic layer alternately laminated on the alloy layer. A magnetoresistive film comprising a lattice film. 3. An artificial lattice film in which a magnetic element and a nonmagnetic element that cause spinodal decomposition are alternately laminated on a substrate, and an interface region between the magnetic element and the nonmagnetic element is formed by spinodal decomposition. A magnetoresistive film, comprising needle-like magnetic particles that are deposited in one direction. 4. A means for applying a magnetic field in parallel with a direction of an easy axis of uniaxial magnetic anisotropy generated by the spinodal decomposition, using the magnetoresistive effect film according to claim 1, 2, or 3. Magneto-resistance effect element.