JPH0878758A - Magnetoresistance effect element - Google Patents

Abstract

PURPOSE: To obtain a gigantic magnetoresistance effect and to prevent the magnetoresistance effect from deteriorating on operation by setting the thermal conductivity of a substrate to a specific range. CONSTITUTION: A magneticresistance element is formed by forming a multilayer magnetoresistance film in artificial lattice film structure where a ferromagnetic film 3 and a non-magnetic film 2 are alternately laminated on a substrate 1 with a thermal conductivity of 2W/mK or larger. In this manner, by using a substrate with a high thermal conductivity, the deterioration of the magnetoresistance effect can be eliminated by operating the magnetoresistance element using a high-density current since heat escapes from the substrate and no heat build-up is generated even if a high-density current is fed to the multilayer magnetoresistance effect film, thus preventing a magnetization arrangement from being disturbed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetoresistive effect element having a multilayer magnetoresistive effect film having an artificial lattice film structure or a spin valve structure, and more particularly to a structure capable of improving the magnetoresistive effect during operation.

[0002]

2. Description of the Related Art A magnetoresistive film having a magnetoresistive effect is widely used as a magnetoresistive effect element for detecting a magnetic field in the fields of a magnetic sensor, a magnetic head, a rotation detecting element, a position detecting element and the like.

Conventionally, an Fe-Ni alloy film (so-called permalloy film) has been mainly used as the magnetoresistive film. However, the rate of change in magnetoresistance of the permalloy film is small, and it is considered that the sensitivity will be insufficient for further high density magnetic recording in the future.

On the other hand, in recent years, attention has been paid to a multi-layered magnetoresistive film having an artificial lattice film structure in which different kinds of metals are alternately laminated by several atomic layers. Among them, a ferromagnetic film made of Fe and Cr
It has been reported that an artificial lattice film composed of a laminated body of a conductor film (non-magnetic film) made of a magnetic material has a magnetoresistance change rate of several tens of percent (hereinafter referred to as “giant magnetoresistance effect”). It is expected to be applied to resistance effect elements. (Physical Review Letters, Vol. 61, page 2472, 1988) After that, in addition to the combination of the Fe layer and the Cr layer, the combination of the ferromagnetic film as the Co layer and the nonmagnetic film as the Cu layer has a giant magnetoresistive effect. It is reported that (Physical Review Letters, 66, 2152 pages, 1991) In addition, Fe, Ni, Co are added to the ferromagnetic film.
It has also been reported that by using an alloy in which the above three elements are combined, a large resistance change can be obtained even with a small magnetic field change, sensitivity to an external magnetic field is improved, and it is effective from a practical viewpoint.

Further, a giant magnetoresistive effect can be obtained even with a film (so-called spin valve film) whose main constituent element is a three-layer film in which a ferromagnetic film, a non-magnetic film and a ferromagnetic film are laminated in this order. It has been reported. (Journal of
(Magnetic and Magnetic Materials, Vol. 93, p. 101, 1991) In addition, the reason why the giant magnetoresistive effect is observed in the multi-layered magnetoresistive film of the artificial lattice film structure or the spin valve structure as described above As an example, the RKKY (Luddermann, Kittel, Kasuya, Yoshida) interaction works between the ferromagnetic films via the conduction electrons in the conductor, and the opposing ferromagnetic films are antiferromagnetically coupled to each other, resulting in antiparallel spin. It is believed that this is due to the occurrence of the above condition, resulting in spin-dependent scattering.

[0006]

However, the magnetoresistive effect element using the multilayer magnetoresistive effect film as described above has a problem that the magnetoresistive effect is deteriorated by the flow of a current having a high current density during operation. Have a It is considered that this is because, when heat is generated by the flow of a current having a high current density, the magnetization arrangement formed in the multilayer magnetoresistive effect film is disturbed.

Therefore, the present invention has been proposed in view of such circumstances, and a giant magnetoresistive effect can be obtained, and
It is an object of the present invention to provide a magnetoresistive effect element in which deterioration of the magnetoresistive effect during operation is prevented.

[0008]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies as to achieve the above-mentioned object, and as a result, by using a substrate having a high thermal conductivity as a substrate for forming a multilayer magnetoresistive film. , It was found that the deterioration of the magnetoresistive effect can be suppressed even when a current having a high current density is passed.

That is, the magnetoresistive effect element according to the present invention is
In a magnetoresistive effect element in which a multilayer magnetoresistive effect film including a ferromagnetic film and a nonmagnetic film is formed on a substrate, the substrate has a thermal conductivity of 2 W / mK or more.

When the magnetoresistive effect element is applied to, for example, a magnetic head, a current of 1 × 10 ^{6 to} 9 × 10 ⁶ A / cm ² is applied, but the thermal conductivity of the substrate is less than 2 W / mK. In this case, when a current having a current density of 1 × 10 ⁶ A / cm ² or more is applied, the magnetoresistive effect (rate of change in resistance) is rapidly deteriorated,
When a current having a current density of 9 × 10 ⁶ A / cm ² is passed, the resistance change rate is less than 20% when a current having a current density of 1 × 10 ⁵ A / cm ² is passed.

The substrate has a thermal conductivity of 2 W.
/ MK or more, but not particularly limited, a ceramic substrate such as NiO-MnO, Mn-Zn ferrite, Ni-Zn
A ferrite substrate such as ferrite, an Al ₂ O ₃ —TiC substrate, or a single crystal Ga in consideration of epitaxial growth.
It is possible to use a substrate made of As, Si, MgO or the like. However, when using the above ferrite substrate,
It is preferable that the surface is non-magnetized. In addition, the Young's modulus of the substrate is 1 × 1 in order to prevent distortion of the lattice of the artificial lattice film when an external force is applied to the magnetoresistive element.
It is preferably 0 ⁹ Nm ^-2 or more.

The multilayer magnetoresistive film formed on such a substrate is composed of an artificial lattice film in which ferromagnetic films and nonmagnetic films are alternately laminated, but even if it is composed of ferromagnetic films and nonmagnetic films. The ferromagnetic film may be composed of spin valve films stacked in this order.

Whether the multilayer magnetoresistive film has an artificial lattice film structure or a spin valve structure, the nonmagnetic film is made of Fe, Co, Ni, Cr, V, Mo,
Nb, Ta, W, Re, Ru, Cu, Rh, Pd, I
r, Pt, B, C, N, O, Si, Al, Ga, Ge,
It is possible to use a conductor made of at least one kind of element among Sn, Sb, and Ag, which is a nonmagnetic material at room temperature. Above all, when a material containing at least one selected from Cu, Ag, and Cr as a main component is used, a multilayer magnetoresistive effect film having a giant magnetoresistive effect can be formed.

Incidentally, at least one selected from Fe, Co and Ni may be contained in an amount of 0.05 to 5 atom%.

The thickness of the non-magnetic film is 1.8-2.
It is preferably 8 nm. This is because the magnetoresistive effect varies depending on the film thickness of the nonmagnetic film, and the magnetoresistive effect deteriorates if the thickness is too thin or too thick.

On the other hand, as the ferromagnetic film forming the multilayer magnetoresistive film, Fe, Co, Ni, Cr, V, Mo and N are used.
b, Ta, W, Re, Ru, Cu, Rh, Pd, Ir,
Pt, B, C, N, O, Si, Al, Ga, Ge, S
A magnetic substance composed of at least one or more of n and Sb elements, which is a ferromagnetic substance at room temperature, can be used.

Above all, it is preferable that the magnetic layer contains 1 to 50 atomic% of Cu and at least one selected from Fe, Co and Ni. At this time,
It is particularly preferable that the composition ratio of Fe, Co, and Ni contained in the magnetic layer is determined as follows in order to improve sensitivity to an external magnetic field.

Fe _x Co _y Ni _z (x, y, z are atomic%)
Then, 10 ≦ x ≦ 25, 40 ≦ y ≦ 80, 10 ≦ z
≦ 40, x + y + z = 100 In the artificial lattice film, the ferromagnetic film is a laminate of a Ni film and a Fe film, a laminate of a Ni alloy film and a Fe alloy film, a Ni—Fe alloy film, a composition. It may be composed of a laminated body of Ni—Fe alloy films different from each other, etc., and such an artificial lattice film is suitable because a soft magnetic film is provided in the upper and lower layers thereof. As the soft magnetic film, any conventionally known material can be used as long as it exhibits soft magnetism.
It is preferable that it is composed of an i-Fe alloy.

When the thicknesses of the ferromagnetic film and the nonmagnetic film forming the artificial lattice film are tA and tB, respectively, 0.5n
m ≦ tA, tB ≦ 50 nm, assuming that the number of pairs of alternately laminated ferromagnetic films and nonmagnetic films is n, 1 ≦ n ≦ 30, and if the total film thickness is T, 5 nm ≦ T ≦ 100 nm. It is suitable.

On the other hand, an antiferromagnetic material layer may be provided on at least one side surface of the spin valve film. The material forming the antiferromagnetic layer is not particularly limited as long as it exhibits antiferromagnetism, but Fe-Mn, Ni
Materials such as O, CoO, NiCoO, and Tb-Co can be used.

In any of the multi-layered magnetoresistive films, it is preferable that the amount of oxygen contained in the non-magnetic film and the ferromagnetic film be 7 atomic% or less in order to stably obtain the giant magnetoresistive effect.

By the way, as a film forming method of each material film constituting the above-mentioned multilayer magnetoresistive effect film, any conventionally known method can be used, for example, a vacuum vapor deposition method, a sputtering method, an ion method. Although a plating method and the like can be mentioned, when forming an alloy film, it is preferable to form the film by a sputtering method using a target having a composition ratio of the alloy. As this sputtering method, an RF magnetron method, a DC magnetron method, a facing target method, or the like is effective. However, since the magnetoresistive effect of the manufactured multi-layered magnetoresistive film varies depending on the conditions such as the gas pressure during film formation, it is necessary to appropriately optimize the film formation conditions.

The magnetoresistive effect of the magnetoresistive effect element as described above can be obtained by measuring the magnetoresistive property by the four-terminal method and calculating the rate of change.

[0024]

The present invention is applied to any of the multi-layered magnetoresistive film having the artificial lattice film structure and the spin valve structure, and a substrate having high thermal conductivity is used as a substrate for forming the multi-layered magnetoresistive film. Even if the magnetoresistive effect element is operated using a current having a high current density, the magnetoresistive effect does not deteriorate. This is because even if a current having a high current density is passed through the multilayer magnetoresistive effect film, heat escapes from the substrate and heat generation is prevented, so that the magnetization arrangement is not disturbed.

Further, even if a current having a high current density is continuously supplied for a long time or heat is applied from the outside, heat is not accumulated in the vicinity of the multilayer magnetoresistive effect film, so that the multilayer magnetic No thermal diffusion of metal occurs between the films of the resistance effect film.

Further, in the magnetoresistive effect element of the present invention, the non-magnetic film forming the multilayer magnetoresistive effect film is Cu,
Since at least one of Ag and Cr is the main component, the giant magnetoresistive effect is easily obtained.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Specific embodiments to which the present invention is applied will be described below with reference to the drawings.

Example 1 In this example, an example of a magnetoresistive effect element in which an artificial lattice film type multi-layered magnetoresistive effect film is formed on a substrate made of Si will be described.

The main part of this magnetoresistive element is shown in FIG.
As shown in, the thermal conductivity at 300K is 148 W /
on a substrate 1 made of a mK Si, Fe ₂₀ -Ni ₄₅ -
A multilayer magnetoresistive effect film having an artificial lattice film structure in which a ferromagnetic film 3 made of Co ₃₅ and a nonmagnetic film 2 made of Cu are alternately laminated for 30 periods is formed. In each material film, the nonmagnetic film 2 has a thickness of 2.1 to 2.3 nm and the ferromagnetic film 3 has a thickness of 1.0 nm.

When manufacturing the magnetoresistive effect element having the above structure, the RF magnetron sputtering apparatus 30 as shown in FIG. 3 was used. This RF magnetron sputtering apparatus 30 is provided in a chamber 21, a substrate holder 22 for holding the substrate 1, a rotating plate 23 for rotating the substrate 1, a target 24 made of Fe ₂₀ —Ni ₄₅ —Co ₃₅ , A target 25 also made of Cu, and shutters 26 and 27 for controlling the start / stop of film formation on the substrate 1. Further, although not shown, the chamber 21 is provided with a gas inlet for introducing a sputtering gas and an exhaust outlet for exhausting.

The RF magnetron sputtering apparatus 30 described above
In order to actually form the ferromagnetic film 3 and the non-magnetic film 2 by using, the inside of the chamber 21 is evacuated through the exhaust port, the sputter gas is introduced through the gas introduction port, and the rotary plate 23 is further introduced. With the non-magnetic substrate 1 rotated, the targets 24 and 25 are sputtered while the shutters 26 and 27 are closed. The shutter 26 on the target 24 is opened when the ferromagnetic film 3 is formed, and the shutter 26 is closed when the nonmagnetic film 2 is formed.
The shutter 27 on the target 25 is opened. In this way, by switching the shutters 26 and 27 to be opened, the ferromagnetic film 3 made of Fe ₂₀ —Ni ₄₅ —Co _{35 and the} nonmagnetic film 2 made of Cu are alternately deposited on the nonmagnetic substrate 1. . The conditions under which the ferromagnetic film 3 and the nonmagnetic film 2 were actually formed are shown below.

Film forming conditions Sputter gas: Argon Ultimate vacuum: 1 × 10 ⁻⁴ Pa or less Argon gas pressure: 0.3 Pa Applied power: 300 W Film forming rate: 0.1 to 0.5 nm / sec On the substrate 1, an artificial lattice film in which 30 layers each of the non-magnetic film 2 and the ferromagnetic film 3 were laminated was formed to complete the magnetoresistive effect element.

Embodiment 2 This embodiment shows an example of a magnetoresistive effect element in which a spin-valve type multi-layered magnetoresistive effect film is formed on a substrate 11 made of Si.

The main part of this magnetoresistive element is shown in FIG.
, A lower ferromagnetic film 12 made of a permalloy film and a non-magnetic film 1 made of a Cu film are formed on a substrate 11 made of Si.
3, upper ferromagnetic film 14 made of permalloy film, Fe ₅₀ −
The antiferromagnetic film 15 made of an Mn ₅₀ alloy film is formed in this order to form a multilayer magnetoresistive film having a spin valve structure. In each material film, the lower ferromagnetic film 12 is 6.
0 nm, the non-magnetic film 13 is 2.2 nm, the upper ferromagnetic film 14
Was 6.0 nm, and the antiferromagnetic film 15 was 8.0 nm.

In order to manufacture the magnetoresistive effect element having the above structure, the magnetron sputtering apparatus shown in FIG. 3 was used as in Example 1. The film forming conditions for the lower ferromagnetic film 12, the non-magnetic film 13, and the upper ferromagnetic film 14 are shown below.

Film-forming conditions for the lower ferromagnetic film 12, the non-magnetic film 13, and the upper ferromagnetic film 14 Sputtering gas: Argon Ultimate vacuum: 1 × 10 ⁻⁴ Pa or less Argon gas pressure: 0.5 Pa Applied power: 300 W Film velocity: 0.1 to 0.5 nm / sec Lamination method: Rotational sputtering experiment 1 using binary of Cu and permalloy Here, the change of magnetoresistance change rate (MR ratio) with respect to the current density flowing in the magnetoresistance effect element is investigated. It was to be.

Specifically, the substrate 1 has a thermal conductivity of 1.38 W.
A magnetoresistive effect element having the same structure as in Example 1 except that it is made of quartz glass (SiO ₂ ) of / mK,
The MR ratio was measured by passing currents of various current densities through the magnetoresistive effect element and the magnetoresistive effect element of Example 1. Then, the keep ratio with respect to the MR ratio when only a current having a current density of 1 × 10 ⁵ A / cm ² was flowing was calculated. The result is shown in FIG. 4 as the relationship between the current density and the MR ratio keeping rate.

From FIG. 4, when the substrate 1 made of SiO ₂ is used, the MR ratio is rapidly deteriorated when a current having a current density of 1 × 10 ⁶ A / cm ² or more is flown, and further the current density is 9 × 10.
^When a current of ⁶ A / cm ² is applied, the current density is 1 × 10 ⁵ A /
MR less than 20% compared to when a current of ² cm ² is applied
It turns out that only a ratio can be secured. On the other hand, when the substrate 1 made of Si is used, the current density is 1 × 10 ⁶ A / cm
Even if the current is ² or more, the MR ratio is not deteriorated.
It can be seen that even when a current having a current density of 9 × 10 ⁶ A / cm ² is passed, an MR ratio of 90% can be secured as compared with the case where a current having a current density of 1 × 10 ⁵ A / cm ² is passed.

From this, it was found that the higher the thermal conductivity of the material forming the substrate 1, the smaller the deterioration of the MR ratio due to the increase in the current density.

Experiment 2 Further , a magnetoresistive effect element having the same structure as in Example 2 was formed except that the substrate 11 was made of quartz glass (SiO ₂ ) having a thermal conductivity of 1.38 W / mK. Currents with various current densities were passed through the effect element and the magnetoresistive effect element of Example 2, and the MR ratio keeping ratio was examined as in Experiment 1. The result is shown in FIG.

As shown in FIG. 5, also in the spin valve type magnetoresistive effect element as shown in Example 2, the thermal conductivity of the material forming the substrate 11 is high as in the artificial lattice film type magnetoresistive effect element. It was found that the deterioration of the MR ratio due to the increase of the current density was smaller.

Experiment 3 Next, the relationship between the thermal conductivity of the material forming the substrate and the MR ratio was examined with the current density of the current flowing through the magnetoresistive element being constant.

Specifically, a magnetoresistive effect element was prepared in the same manner as in Example 1 except that SiO ₂ , NiO-MnO, and Al ₂ O ₃ -TiC were used as the substrate 1 instead of Si, and the current was applied. The MR ratio was measured when a current having a density of 9 × 10 ⁶ A / cm ² was passed. Then, the keep ratio with respect to the MR ratio when only a current having a current density of 1 × 10 ⁵ A / cm ² was flowing through each magnetoresistive effect element was calculated. The thermal conductivity of the material used for the substrate 1 at 300K and the above calculation results (MR
Table 1 shows the relative keep ratio. In addition, in Table 1, the substrate 1
The results obtained when Si is used as (Example 1) are also shown.

[0044]

[Table 1]

FIG. 6 is a graph showing the relationship between the thermal conductivity and the MR ratio keeping rate.

From these results, the MR ratio keeping rate is improved as the material having the higher thermal conductivity is used for the substrate 1.
That is, it was found that the deterioration of the MR ratio can be suppressed.

Regarding the spin-valve type magnetoresistive element shown in Example 2, the MR ratio keeping rate was examined by using materials having different thermal conductivities as the substrate 11.
The results are similar to the above.

[0048]

As is apparent from the above description, when the present invention is applied, a magnetoresistive effect element in which deterioration of the magnetoresistive effect due to heat generation during operation is prevented can be obtained.

Therefore, if the magnetoresistive effect element according to the present invention is applied to, for example, a magnetic head, it will have higher density recording and higher performance capable of meeting severe specification conditions.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of a magnetoresistive effect element having an artificial lattice film structure.

FIG. 2 is a schematic cross-sectional view showing an example of a spin valve type magnetoresistive effect element.

FIG. 3 is a schematic view showing an RF magnetron sputtering apparatus used for manufacturing the magnetoresistive effect element of the present invention.

FIG. 4 shows a magnetoresistive effect element having an artificial lattice film structure,
It is a characteristic view which shows the relationship between current density and MR ratio keeping rate.

FIG. 5 shows a spin valve type magnetoresistive effect element,
It is a characteristic view which shows the relationship between current density and MR ratio keeping rate.

FIG. 6 is a characteristic diagram showing the relationship between the thermal conductivity of the substrate and the MR ratio keeping ratio.

[Explanation of symbols]

 1 Substrate 2 Nonmagnetic Film 3 Ferromagnetic Film 11 Substrate 12 Lower Ferromagnetic Film 13 Nonmagnetic Film 14 Upper Ferromagnetic Film 15 Antiferromagnetic Film 21 Chamber 22 Substrate Holder 23 Rotating Plate 24, 25 Target 26, 27 Shutter 30 RF Magnetron Sputtering device

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical indication H01F 10/26

Claims (4)

[Claims] 1. A magnetoresistive effect element comprising a multi-layer magnetoresistive effect film comprising a ferromagnetic film and a non-magnetic film formed on a substrate, wherein the substrate has a thermal conductivity of 2 W / mK or more. And a magnetoresistive effect element. 2. The magnetoresistive effect element according to claim 1, wherein the multilayer magnetoresistive effect film is made of an artificial lattice film in which the ferromagnetic films and the nonmagnetic films are alternately laminated. 3. The magnetoresistive film according to claim 1, wherein the multi-layered magnetoresistive film comprises a spin valve film in which the ferromagnetic film, the nonmagnetic film, and the ferromagnetic film are stacked in this order. Effect element. 4. The non-magnetic film contains at least one selected from Cu, Ag, and Cr as a main component, and the non-magnetic film according to claim 1. Magnetoresistive element.