JP3346787B2 - Magnetic laminate and magnetoresistive element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic laminate and a magnetoresistive element (MR element) using the same.

[0002]

2. Description of the Related Art MR elements, such as various magnetic sensors (MR sensors) and magnetic heads (MR heads), detect a change in electric resistance of a magnetic film due to a magnetic field and measure the magnetic field strength and its change. It is required that the magnetoresistance ratio at room temperature is large and the operating magnetic field strength is small.

Conventionally, as a magnetic film of an MR element, an Fe—Ni alloy (permalloy) utilizing an anisotropic magnetoresistance effect has been used.
And Ni-Co alloys are typically used. But,
In the case of the Fe-Ni alloy or the Ni-Co alloy, the operating magnetic field strength is small, but the difference between the change in the longitudinal magnetoresistance and the change in the horizontal magnetoresistance, that is, the anisotropic magnetoresistance effect is as small as 2%.

[0004]

SUMMARY OF THE INVENTION The main object of the present invention is to provide a magnetic laminated body having a large magnetoresistance change rate, a small operating magnetic field strength, and a variable operating magnetic field strength. And a magnetoresistive element using the same.

[0005]

This and other objects are achieved by the present invention which is defined below as (1) to (4). (1) a magnetic thin film having a composition of Ni _x M _1-x (M represents Fe and / or Co, and x satisfies the relationship of 0 <x <1) having a thickness of 4 to 20 °; The magnetic thin film and the Ag thin film are laminated with the number of repetitions being two or more, having an in-plane axis of easy magnetization, and a squareness ratio Br in the direction of the axis of easy magnetization. / Bs
Is 0.5 or less. (2) The magnetic laminate of (1) above, which exhibits antiferromagnetism. (3) The magnetic laminate according to the above (1) or (2), wherein the magnetic thin film and the Ag thin film are laminated by a molecular beam epitaxy method. (4) A magnetoresistance effect element comprising the magnetic laminate according to any one of (1) to (3).

[0006]

[0007]

[0008]

[0009]

[0010]

In recent years, artificial lattices using the molecular beam epitaxy (MBE) method have appeared with the progress of thin film technology. This artificial lattice uses molecular beam epitaxy (MB
It has a structure in which a thin film having a thickness on the order of atoms of a metal is periodically laminated by using the method E), and exhibits characteristics different from those of a bulk metal.

As one of such artificial lattices, a giant magnetoresistance change material of an Fe / Cr-based magnetic laminate in which Fe and Cr are alternately laminated has been developed. In this case, Cr
An Fe thin film sandwiching the thin film is magnetically coupled in antiparallel. Then, due to the external magnetic field, the spins of Fe are aligned in one direction, and the resistance decreases accordingly. The results show a giant magnetoresistance change of 46% at 4.2K and 16% at room temperature (Physical Review Letters 61, 247).
2 pages, 1988).

However, the Fe / Cr-based magnetic laminate has a large magnetoresistance change rate (MR change rate) but an extremely large operating magnetic field strength of about 20 kOe, and has practical limitations as an MR element.

[0014] Active research and development of such an artificial lattice magnetic laminate exhibiting such antiferromagnetism has been started worldwide thereafter. Until now, Co / Cr-based and Co / Ru-based magnetic laminates have been developed. , Antiferromagnetic spin interlayer coupling has been discovered (Physical Review Letters 64, 2304)
Page, 1990). However, the MR change rate is Co /
6.5% (4.5K) for Cr system, 6.5 for Co / Ru system
% (4.5K), which is an extremely small value.

Further, Co / Cu in which Co and Cu are alternately laminated
A giant magnetoresistance change material of a Cu-based magnetic laminate has been disclosed [DHMosca, et al., J. Magnetism and Magnetic
Material, vol.94 (1991), L1]. It is considered that Co has antiferromagnetic coupling between the layers, and a mechanism similar to that of the above-described Fe / Cr-based magnetic laminated body has 78% at 4.2K and 48% at room temperature. It is also described to exhibit a giant magnetoresistance.

Furthermore, a giant magnetoresistance material of a Co—Fe / Cu-based magnetic laminate in which Co and Fe and Cu are alternately laminated has been disclosed [Saito, et al., JJAP,
vol.30 (1991), L1733]. This is also considered to show a change in magnetoresistance based on antiferromagnetic coupling, and the change is shown to be as large as about 40% at room temperature.

However, Co / Cu-based or Co-Fe / Cu
As described above, all of the magnetic laminated bodies of the system are manufactured by the ion beam sputtering method, although the magnetoresistance ratio is large. In the ion beam sputtering method, since the kinetic energy of the particles to be deposited is as high as several tens to several hundreds eV, each element causes mutual diffusion at the interface, resulting in a composition distribution. As a result, it becomes difficult to obtain the unique characteristic of the artificial lattice, which is considered to be caused by the direct contact of the different elements.

Further, a magnetic laminate in which Ni and Ag are alternately laminated is disclosed [B. Rodmacq, et al., First Ky.
oto-Duisburg Workshop on Ultrathin Magnetic Films
andMultilayers (1991): CA dos Santos, et al., Ap
plied Physics Letters, Vol. 59 (1991): P126], and describes that it shows a change in magnetoresistance based on antiferromagnetic coupling. The change in magnetoresistance at this time is 4.2
K is about 25%.

However, this is produced by a sputtering method, and has the same drawbacks as those described above.

However, antiferromagnetic coupling of a magnetic laminate using an Fe—Ni permalloy alloy has not been known.

[0021]

[Specific Configuration] Hereinafter, a specific configuration of the present invention will be described in detail.

The magnetic laminate of the present invention comprises Ni _x
M _1-x (M represents Fe and / or Co, x is 0 <
The relationship x <1 is satisfied. ), And each magnetic thin film is alternately laminated with an Ag thin film as a non-magnetic intermediate layer. As described above, the magnetic thin film according to the present invention has a Ni—Fe alloy (permalloy alloy) composition or N
It has an i-Co alloy composition and further has Ni-
Fe-Co alloy composition may be used, and Ni
And at least one of Fe and Co.

When M is Fe, x is preferably 0.4
It is preferable to satisfy the relationship of <x <1, especially 0.7 ≦ x ≦ 0.9. By setting x in such a range, the magnetocrystalline anisotropy becomes small and becomes isotropic, and the antiferromagnetic coupling between the layers in the magnetic laminate becomes relatively smaller than the magnetocrystalline anisotropy. The magnetoresistance change (MR change) based on such antiferromagnetism tends to increase.
That is, the effect of increasing the sensitivity when the MR element is used can be obtained. On the other hand, when x becomes small and the proportion of Fe becomes large, the crystal magnetic anisotropy becomes large, and it becomes difficult to sufficiently obtain antiferromagnetism, so that a sufficient magnetoresistance change (MR change) is not exhibited. When x = 0, this is a simple example.
Also, when x becomes large, when the artificial lattice structure is adopted, Ni does not show sufficient magnetization due to a decrease in the Curie temperature, and the MR change is extremely reduced. A simple example is when x = 1.

When M is Co, 0 <x ≦ 0.9
Is preferably satisfied. By setting x in such a range, it becomes easy to show ferromagnetism at room temperature,
A sufficient MR change can be obtained. On the other hand, when x becomes large and approaches Ni alone, the thickness of the magnetic film in the present invention does not show ferromagnetism at room temperature. For this reason, MR
Substantial use for sensors and MR heads becomes impossible.
A simple example is when x = 1.

Further, when M is Fe and Co, if the composition is represented by Ni _x Fe _y Co _1-xy , x is 0 <x ≦
It is preferable to satisfy the relation of 0.5. By setting x in such a range, the MR change becomes large. When x increases, the proportion of Ni relatively increases,
It does not show sufficient magnetization at room temperature. As a result, the change in MR at room temperature is reduced, and the function as an MR sensor or MR head cannot be achieved. A simple example is when x = 1. In addition, y is 0.1 ≦ y ≦ 0.6, particularly, 0.1.
It is preferable that the relationship of 1 ≦ y ≦ 0.4 is satisfied. By setting y in such a range, the degree of electron scattering between when the spin direction of the magnetic film is antiparallel and when the spin direction is parallel is increased, thereby increasing the MR change. If y is too small or too large, the degree of scattering of electrons becomes small, so that a large MR change is not exhibited.

In the present invention, the thickness of the magnetic thin film is 4 to 20.
{, Preferably 6 to 16}. If the thickness is too large, the distance between the magnetic elements between the layers becomes relatively long, the antiferromagnetic coupling is lost, and no giant magnetoresistance change is exhibited. On the other hand, if the thickness of the magnetic thin film is too small, the magnetic elements will not be continuously arranged in the formation surface, and will not exhibit ferromagnetism.

The Ag thin film is preferably formed only of Ag, and has a thickness of 60 ° or less, particularly 50 ° or less.
More preferably, the angle is set to 45 ° or less. As the film thickness increases, the distance between the magnetic thin films increases, and antiferromagnetic coupling is lost. The thickness of the Ag thin film is
It is preferable that the thickness be 2 mm or more. When the film thickness decreases,
As a result, the function of the non-magnetic intermediate layer is lost.

In such a case, in the magnetic laminate of the present invention, the magnetic exchange coupling energy changes while periodically oscillating due to the repetition period of the magnetic layer, in particular, the change in the thickness of the Ag thin film. More specifically, the thickness of the Ag thin film is set to 2 to 6 by vibrating magnetic coupling mainly based on the thickness of the Ag thin film.
When it is changed within the range of 0 °, the saturation applied magnetic field Hsat changes periodically. Hsat changes periodically in the range of 1 kOe to 10 kOe, and the maximum value and the minimum value of Hsat also change. At this time, the magnetoresistance change rate also periodically changes and vibrates, but there is an Ag thin film thickness region where a magnetoresistance change rate exceeding 8% can be obtained at room temperature.

As a result, by selecting the thickness of the Ag thin film in the range of 2 to 60 °, the operating magnetic field strength is set to 0.01 to
At 20 kOe, a magnetic laminate having a magnetoresistance ratio of 1 to 15% at room temperature can be freely designed.

The thickness of the magnetic thin film and the Ag thin film can be measured by a transmission electron microscope, a scanning electron microscope, an Auger electron spectroscopic analysis, and the like. It can be confirmed by electron beam diffraction (RHEED) or the like.

The analysis of the film composition can be performed by X-ray microanalysis (EPMA), X-ray fluorescence analysis (ICP), or the like.

In the magnetic laminate of the present invention, the number of layers of the magnetic thin film and the number of repetitions of the magnetic thin film / Ag thin film unit are not particularly limited, and may be appropriately selected according to the intended rate of change in magnetoresistance. In order to obtain a sufficient magnetoresistance change rate, the number of repetitions is set to 2 or more, particularly 8 or more. The higher the number of repetitions, the higher the ratio of scattering of free electrons, which is preferable. Further, if the number of repetitions is too large, the quality of the film deteriorates greatly, and the improvement of the characteristics cannot be expected. The long-period structure can be confirmed by the appearance of a first-order secondary peak or the like corresponding to the repetition period in a small-angle X-ray diffraction pattern.

Such a laminate exhibits antiferromagnetism as a result of antiferromagnetic coupling between the layers of the magnetic thin film. Antiferromagnetism can be easily confirmed by, for example, polarized neutron diffraction. In addition, as a result of showing antiferromagnetism, the applied magnetic field in the plane of the laminate was measured using a vibrating magnetometer or BH tracer.
When the magnetization curve or BH loop is measured, the squareness ratio Br
/ Bs is 0.5 or less, especially 0.3 or less, and in some cases, Br / Bs is almost 0. At this time, the applied magnetic field-magnetization curve and the demagnetization curve and the demagnetization curve of the BH loop are extremely close to each other. And a vibrating magnetometer or BH
When the easiness of magnetization or the anisotropy energy of the in-plane and in-plane normal directions is measured with a tracer or a torque meter, the easy axis exists in the plane. In addition, Br /
When Bs exceeds 0.5, the ratio of exhibiting antiferromagnetism in the inside of the stacked body rapidly decreases, and as a result, the MR ratio decreases.

There are no particular restrictions on the material of the substrate forming the laminate, and various substrates that are commonly used, such as magnesia, sapphire, silicon, gallium-arsenic, strontium titanate, as well as amorphous glass substrates and crystallized glass substrates. Single crystal substrates such as various oxides such as barium titanate and lithium niobate, and polycrystalline substrates such as alumina-titanium carbide and calcium titanate can be used.

In the case of the Fe / Cr system, when a glass substrate is used, the characteristics deteriorate. However, in the present invention, sufficiently good characteristics can be obtained even when a glass substrate is used. In such a case, generally, according to X-ray diffraction in the mid-angle region, the Ag thin film is (111) -oriented on the glass substrate, and Ni _x Fe
_1-x , Ni _x Co _1-x , and Ni _x Fe _y Co _1-xy all have fcc (111) orientation and are considered to be polycrystalline. On the MgO substrate, Ag
(200) peak, Ni _x Fe _1-x , Ni _x Co
_{1- x} , Ni _x Fe _y Co _1-xy , (20
0) peak was confirmed, and it is considered that epitaxial growth of (100) was mainly performed.

The dimensions of the substrate are not particularly limited, and may be appropriately selected according to the element to be applied. Various base films may be formed on the surface of the base on the side where the magnetic laminate is formed, if necessary.

Further, an oxidation preventing film such as silicon nitride, silicon oxide and various metal layers may be provided on the uppermost layer surface, and a metal conductive layer for leading out electrodes may be provided.

For producing the magnetic laminate of the present invention, it is preferable to use a molecular beam epitaxy (MBE) method.
In the case of the present invention, the thickness of the magnetic thin film and the Ag thin film to be formed are extremely thin, so that it is necessary to apply them slowly. In order to avoid impurity contamination during film formation, film formation in an ultra-high vacuum region is required. The lower the energy of the adhered particles, the better, so as not to cause interdiffusion when forming each layer and to lose the antiferromagnetism. Most suitable for this purpose is the MBE method.

On the other hand, in the case of a magnetic laminate by ion beam sputtering, the energy of the adhered particles is high,
There are difficulties in film quality, such as the composition distribution of each element between the layers, and this leads to a decrease in the MR change rate and the like.

The MBE method is a type of ultra-high vacuum deposition method in which molecules or substances evaporated from a deposition source are attached to the surface of a substrate in an ultra-high vacuum to grow a thin film. Specifically, a deposition source is selected by opening and closing a shutter, and a magnetic thin film and a non-magnetic thin film are alternately deposited while measuring with a film thickness meter.

At this time, the ultimate pressure is usually about 10 ^-11 to 10 ^-9 Torr, and the pressure during the deposition is 10 ^-11 to 10 ^-7 Torr.
In particular, at about 10 ⁻¹⁰ to 10 ⁻⁷ Torr, a film forming rate of 0.01
It is preferable to form the film at a rate of about 10 to 10 ° / sec, particularly about 0.1 to 1.0 ° / sec. The adhered particles are 0.01 to 5
It has a kinetic energy of eV, preferably 0.01-1 eV. The central energy is 0.05 to 0.5 eV.

Further, it is an evaporation source used for producing a magnetic thin film having a composition of Ni _x M _1-x (M represents Fe or / and Co, and x satisfies the relationship of 0 <x <1). As the mother alloy, it is preferable to use an alloy having a composition of Ni _x M _1-x (M represents Fe or Fe and / or Co, and x satisfies the relationship of 0 <x <1).

In order to adjust the crystal structure of the thin film, the substrate may be heated at the time of film formation, if necessary. The heating temperature is preferably set to 800 ° C. or less to prevent diffusion between the thin films. Note that a magnetic thin film may be formed in a magnetic field to enhance in-plane magnetic anisotropy.

The magnetic laminate of the present invention can be used for an MR sensor or an MR sensor.
It is preferably applied to various MR elements such as a head, and when used, a bias magnetic field is applied as necessary. Further, the magnetic laminate of the present invention may be arranged in the gap of the thin film type magnetic head or in the same track, and the reading may be performed by the MR element.

[0045]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to specific examples.

Example 1 Ni _x Fe _1-x (x = 0.8) was formed on a magnesia single crystal substrate.
The magnetic thin film having the composition of 1) and the Ag thin film are alternately deposited,
With 8% of Ni _x Fe _1-x and 24% of Ag as one unit,
This was laminated 30 times to produce a magnetic laminate sample No. 1. Hereinafter, such a case is indicated as [NiFe (8) -Ag (24)] ₃₀ . The thickness of each thin film was measured with a transmission electron microscope.

The composition of the thin film was measured by ICP.

The vapor deposition was carried out by a MBE method in a vacuum chamber at an ultimate pressure of 7 × 10 ⁻¹¹ Torr. Operating pressure is 9
The deposition was performed while rotating the substrate at 30 rpm, at × 10 ⁻¹⁰ Torr and at a deposition rate of about 0.5 ° / sec. The substrate temperature during vapor deposition was 30 ° C. The central kinetic energy of the deposited particles is about 0.1 eV.

The mother alloy used for the deposition source for producing the Ni _x Fe _1-x magnetic thin film had a composition of Ni _0.8 Fe _0.2 .

The applied magnetic field-magnetization curve was measured using a vibrating magnetometer.

FIG. 1 shows an applied magnetic field-magnetization curve in the in-plane direction of the sample. Squareness ratio in this case (in-plane Br / Bs)
Was 0.1.

This product has an easy axis of magnetization in the plane, and as described above, the squareness ratio was as small as 0.1, and it was estimated that it exhibited antiferromagnetism. In fact, in the result of polarized neutron diffraction, diffraction lines were observed at Bragg angles corresponding to twice the period of the stacking unit thickness, and antiferromagnetic coupling between layers was confirmed.

Sample No. 1 was made into a rectangular shape of 0.5 mm × 1.0 mm, and the resistance when the external magnetic field was changed from −20 to +20 kOe at the maximum was measured by a four-terminal method.

For sample No. 1, the magnetoresistance change rate Δρ / ρ _S at room temperature RT when an external magnetic field was applied in the plane of the sample and in a direction perpendicular to the current (Trans) was determined. Here, ρ _S is the saturation resistivity (when the applied magnetic field is increased, ρ _S
Is the value when is saturated). Also, Δρ = ρ−ρ _S
Where ρ is the resistivity at each applied magnetic field, and Δρ in the case of MR change due to antiferromagnetism of the present invention is Δρ = ρ (H = O) −ρ (H = 20 kOe, where H is the applied magnetic field. ).

As a result, Δρ / ρ _S was 7.9%. Ρ _S was 11.4 μΩcm and Δρ was 0.9 μΩcm.

Example 2 [NiFe (8)-] was prepared in the same manner as in Sample 1 of Example 1 except that the substrate was changed to amorphous glass.
Ag (24)] to form a magnetic laminate of ₃₀
2 was produced. This also has an in-plane Br / Bs of 0.2,
It was presumed that it had an easy axis of magnetization in the plane and exhibited antiferromagnetism.

For sample No. 2, Δρ / ρ _S was determined in the same manner as in Example 1, and was found to be 7.1%.
Further, ρ _S was 12.0 μΩcm and Δρ was 0.85 μΩcm.

Example 3 In the same manner as in the sample No. 1 of Example 1, except that the thickness per unit of Ag was set to 12 °, [NiFe
(8) -Ag (12)] Sample No. 3 displayed by ₃₀
Was prepared by MBE method. However, the operating pressure is 8 × 1
0 ^-10 Torr.

FIG. 2 shows an applied magnetic field-magnetization curve in the in-plane direction of the sample. In this case, in-plane Br / Bs was 0.4, and it was presumed to have an easy axis of magnetization in the plane and exhibit antiferromagnetism.

For sample No. 3, Δρ / ρ _S was determined in the same manner as in Example 1, and found to be 7.1%.
Ρ _S was 18.4 μΩcm and Δρ was 1.3 μΩcm.

Example 4 [NiFe (8)-] was prepared in the same manner as in Example 3 except that the substrate was changed to amorphous glass.
Ag (12)] A magnetic laminate of ₃₀ was formed.
4 was produced. This also has an in-plane Br / Bs of 0.4,
It was presumed that it had an easy axis of magnetization in the plane and exhibited antiferromagnetism.

For sample No. 4, Δρ / ρ _S was determined in the same manner as in Example 1, and it was 6.3%.
Further, ρ _S was 19.0 μΩcm and Δρ was 1.2 μΩcm.

Example 5 Room temperature RT when the thickness t of the Ag thin film was variously changed in [NiFe (8) -Ag (t)] ₃₀ according to the sample No. 1 of Example 1 (substrate: magnesia) FIG. 3 shows the relationship between the thickness of the Ag thin film and Δρ / ρ _{S in} FIG. Here, Δρ is an absolute resistance value when the resistivity at an applied magnetic field of 0 is ρ _O, and is given by Δρ = ρ _O −ρ _S.

As is clear from FIG. 3, Δρ / ρ _S is A
The thickness g depends on the thickness of the thin film, and changes by vibrating periodically. The maximum value of Δρ / ρ _S was 7.9% at a thickness of 24 °.

Example 6 Room temperature RT when [NiFe (8) -Ag (t)] ₃₀ according to the sample No. 2 (substrate: glass) of Example 2 and the thickness t of the Ag thin film was variously changed The relationship between the thickness of the Ag thin film and Δρ / ρ _S in FIG.
Are also shown.

As is apparent from FIG. 3, similar to the fifth embodiment,
Δρ / ρ _S depends on the film thickness of the Ag thin film, and changes by vibrating periodically. The maximum value of Δρ / ρ _S was 7.1% at a film thickness of 24 °.

Example 7 Sample No. 1 of Example 1 was repeated except that the thickness per unit of Ni _x Fe _1-x was 12 mm.
Sample No. 7 represented by [NiFe (12) -Ag (24)] ₃₀ was prepared by MBE. However, the operating pressure was 9 × 10 ⁻¹⁰ Torr.

Sample No. 7 had an in-plane Br / Bs of 0.4.
It was presumed that the film had an easy axis of magnetization in the plane and exhibited antiferromagnetism.

For sample No. 7, Δρ / ρ _S was determined in the same manner as in Example 1, and found to be 5.7%.

A magnetic laminate was prepared in the same manner as in Example 7 except that the substrate was a glass substrate, and its characteristics were examined. As a result, almost the same results were obtained.

In the above description, the composition of the magnetic thin film is set to N
A magnetic laminate was prepared in the same manner as above except that i _x Fe _1-x (x = 0.9) was used, and the characteristics were examined. As a result, substantially the same results as described above were obtained.

Example 8 Ni _x Co _{1 -x} (x = 0.7) was formed on a magnesia single crystal substrate.
A magnetic thin film having the composition of 9) and an Ag thin film are alternately deposited,
With 8% Ni _x Co _1-x and 10% Ag as one unit,
This was laminated 30 times [NiCo (8) -Ag (1
0)] A magnetic laminate sample No. 11 indicated by ₃₀ was produced. The thickness of each thin film was measured with a transmission electron microscope.

The composition of the thin film was measured by ICP.

The vapor deposition was performed by MBE in a vacuum chamber having a ultimate pressure of 9 × 10 ⁻¹¹ Torr. Operating pressure is 1
The deposition was performed at a rotation speed of 30 rpm at × 10 ⁻⁹ Torr and a deposition rate of about 0.3 ° / sec. The substrate temperature at the time of vapor deposition was 28 ° C. The central kinetic energy of the deposited particles is about 0.1 eV.

The mother alloy used for the deposition source for producing the Ni _x Co _{1 -x} magnetic thin film had a composition of Ni _0.8 Co _0.2 .

The applied magnetic field-magnetization curve was measured with a vibrating magnetometer.

FIG. 4 shows an applied magnetic field-magnetization curve in the in-plane direction of the sample. Squareness ratio in this case (in-plane Br / Bs)
Was 0.1.

It was presumed to have an easy axis of magnetization in the plane, a small squareness ratio of 0.1 as described above, and exhibit antiferromagnetism. In fact, in the result of polarized neutron diffraction, diffraction lines were observed at Bragg angles corresponding to twice the period of the stacking unit thickness, and antiferromagnetic coupling between layers was confirmed.

Sample No. 11 was formed into a rectangular shape of 0.5 mm × 1.0 mm, and the resistance when the external magnetic field was varied from −20 to +20 kOe at the maximum was measured by a four-terminal method.

For sample No. 11, when an external magnetic field was applied in the plane of the sample and perpendicular to the current (Trans),
It was determined by a magnetoresistance ratio [Delta] [rho] / [rho _S at room temperature RT in the same manner as in Example 1, was 7.5%. Ρ _S was 14.9 μΩcm and Δρ was 1.1 μΩcm.

Further, Δρ / ρ _S at 77K is 15.8.
%, Ρ _{S at} this time was 12.8 μΩcm, and Δρ was 2.0 μΩcm.

Example 9 Sample No. 11 of Example 8 was repeated except that the thickness per unit of Ag was 15 °.
o (8) -Ag (15)] Sample No. indicated by ₃₀
No. 12 was produced by the MBE method. However, the operating pressure is 9
× 10 ⁻¹⁰ Torr.

FIG. 5 shows an applied magnetic field-magnetization curve in the in-plane direction of the sample. In this case, in-plane Br / Bs was 0.02, and it was presumed to have an easy axis of magnetization in the plane and exhibit antiferromagnetism.

For sample No. 12, Δρ / ρ _S at room temperature RT was determined in the same manner as in Example 1.
4%. Further, ρ _S is 13.9 μΩcm, and Δρ is 0.1.
It was 9 μΩcm.

Further, Δρ / ρ _S at 77K is 17.7.
%, Ρ _{S at} this time was 10.1 μΩcm, and Δρ was 1.8 μΩcm.

Example 10 [NiCo (8) -Ag (t)] ₃₀ according to Sample No. 11 of Example 8 (base: magnesia)
Room temperature RT and 77K when the thickness t of the thin film is variously changed
6 shows the relationship between the thickness of the Ag thin film and Δρ / ρ _S in FIG. Here, Δρ is an absolute resistance value when the resistivity at an applied magnetic field of 0 is ρ _O, and Δρ = ρ _O −
given by ρ _S.

As is clear from FIG. 6, Δρ / ρ _S is A
It changes depending on the thickness of the g thin film and vibrates periodically. At room temperature RT, the maximum value of Δρ / ρ _S is 7.5% at a thickness of 10 °. At 77K, the maximum value of Δρ / ρ _S was 17.7% at a film thickness of 15 °.

At this time, the relationship between the thickness of the Ag thin film at room temperature RT and 77 K and ρ _s and Δρ is as shown in FIG.

Example 11 In the sample No. 11 of the example 8, Ni _x Co _{1 -x}
Sample No. 13 represented by [NiCo (11) -Ag (10)] ₃₀ was similarly prepared except that the thickness per unit was set to 11 ° by MBE. However, the operating pressure was 2 × 10 ⁻⁹ Torr.

Sample No. 13 has an in-plane Br / Bs of 0.
In No. 2, it was presumed to have an easy axis of magnetization in the plane and exhibit antiferromagnetism.

For sample No. 13, Δρ / ρ _S at room temperature was determined in the same manner as in Example 1. As a result, 5.8%
Met. Ρ _S is 15.4 μΩcm, Δρ is 0.9 μΩ
Ωcm.

Example 12 In the sample No. 11 of the example 8, the Ni _x Co _1-x
The sample No. 14 represented by [NiCo (14) -Ag (10)] ₃₀ was similarly prepared by MBE except that the thickness per unit was 14 °. However, the operating pressure was 9 × 10 ⁻¹⁰ Torr.

Sample No. 14 had an in-plane Br / Bs of 0.
In No. 5, it was presumed to have an easy axis of magnetization in the plane and exhibit antiferromagnetism.

For sample No. 14, Δρ / ρ _S at room temperature was determined in the same manner as in Example 1. As a result, 3.9%
Met.

In Examples 8 to 12, a magnetic laminate was prepared in the same manner as above except that the substrate was a glass substrate, and its characteristics were examined. As a result, substantially the same results as described above were obtained.

[0096] Further, in Examples 8 to 12, by changing the composition of the magnetic thin film _{Ni x Co 1-x (x} = 0.7), other likewise to produce a magnetic multilayer structure, was characterized However, almost the same results as above were obtained.

Example 13 Ni _x Fe _y Co _1-xy (x
= 0.1, y = 0.1), and a magnetic thin film and an Ag thin film are alternately vapor-deposited, and Ni _x Fe _y Co _{1-xy of} 8 ° and 1
This was laminated 50 times using 2% Ag as one unit [N
iFeCo (8) -Ag (12)] ₅₀ was prepared as a magnetic laminate sample No. 21.

The thickness of each thin film was measured with a transmission electron microscope.

The composition of the thin film was measured by ICP.

The vapor deposition was performed by MBE in a vacuum chamber at a ultimate pressure of 7 × 10 ⁻¹¹ Torr. Operating pressure is 9
The deposition was performed at a rate of × 10 ⁻¹⁰ Torr and a deposition rate of about 0.3 ° / sec, while rotating the substrate at 30 rpm. The substrate temperature during vapor deposition was 25 ° C. The central kinetic energy of the deposited particles is about 0.1 eV.

The mother alloy used for the deposition source for producing the Ni _x Fe _y Co _1-xy magnetic thin film was Ni _0.12 Fe _0.12 Co
The composition was _0.76 .

It was estimated that the in-plane Br / Bs was 0.1, the surface had an easy axis of magnetization, and exhibited antiferromagnetism.

For Sample No. 21, the Δρ / ρ _S at room temperature was determined in the same manner as in Example 1, and found to be 12%. Ρ _S was 14 μΩcm and Δρ was 1.7 μΩcm.

[0104]

According to the magnetic laminate of the present invention, a larger magnetoresistance change can be obtained at a lower magnetic field, as compared with a conventional magnetoresistance change laminate by antiferromagnetic coupling. Then, using the oscillation cycle change of the magnetic coupling energy,
At any operating magnetic field of 20 kOe, any magnetic change of 1 to 15% can be obtained. Further, there is no restriction on the material of the substrate, such as lamination on a glass substrate, and there is no restriction on the substrate temperature during film formation, which is advantageous in mass production. Further, it has a feature that different MR change characteristics can be obtained depending on the direction of the external magnetic field.

[Brief description of the drawings]

FIG. 1 is a graph showing an applied magnetic field-magnetization curve of a magnetic laminate of the present invention.

FIG. 2 is a graph showing an applied magnetic field-magnetization curve of the magnetic laminate of the present invention.

FIG. 3 is a graph showing the relationship between the thickness of the Ag thin film of the magnetic laminate of the present invention and the rate of change in magnetoresistance.

FIG. 4 is a graph showing an applied magnetic field-magnetization curve of the magnetic laminate of the present invention.

FIG. 5 is a graph showing an applied magnetic field-magnetization curve of the magnetic laminate of the present invention.

FIG. 6 is a graph showing the relationship between the thickness of the Ag thin film of the magnetic laminate of the present invention and the rate of change in magnetoresistance.

FIG. 7 shows the thickness of the Ag thin film of the magnetic laminate of the present invention and ρ.
₆ is a graph showing the relationship between _S and Δρ.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-2-23681 (JP, A) JP-A-63-64374 (JP, A) JP-A-3-52111 (JP, A) Patent 3320079 (JP, A) B2) (58) Field surveyed (Int.Cl. ⁷ , DB name) H01F 10/16 H01F 1/147 H01L 43/08 H01L 43/10

Claims (4)

(57) [Claims] 1. A magnetic thin film having a composition of Ni _x M _1-x (M represents Fe and / or Co and x satisfies a relation of 0 <x <1) having a thickness of 4 to 20 °; An Ag thin film having a thickness of about 60 ° is laminated, and the unit of the magnetic thin film and the Ag thin film is laminated two or more times, and laminated.
Has an easy axis of magnetization in the plane and has a squareness ratio Br in the easy axis direction.
/ Bs is 0.5 or less. 2. The magnetic laminate according to claim 1, which exhibits antiferromagnetism. 3. The magnetic laminate according to claim 1, wherein the magnetic thin film and the Ag thin film are laminated by a molecular beam epitaxy method. 4. A magnetoresistive element comprising the magnetic laminate according to claim 1.