JPH0888424A - Multi-layer film magnetoresistance effect element and its manufacture - Google Patents

Abstract

PURPOSE: To provide a multi-layer film magnetoresistance effect element wherein magnetic field sensitivity is sufficient and hysteresis is small. CONSTITUTION: Magnetic layers 45, 47, 49,... and non-magnetic layers 43, 43,... are alternately laminated by deposition and sputtering method, etc. When each of magnetic layers 45, 47, 49,... is film-formed, magnetization facilitating axis of magnetic layer is guided in the application direction of external magnetic field by applying external magnetic field. At this time, in the order of lamination of magnetic layers 45, 47, 49,..., magnetization facilitating axes are alternately guided in generally orthogonal direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in, for example, a magnetic sensor or a magnetic head utilizing the magnetoresistive effect.
The present invention relates to a magnetoresistive element including a multilayer film.

[0002]

2. Description of the Related Art Heretofore, magnetic materials, such as permalloy alloy thin films, which electrically detect changes in magnetic field utilizing the ferromagnetic magnetoresistance effect have been used as magnetic sensors and magnetic heads.

Nowadays, a material for detecting a magnetic field with higher output and higher sensitivity is required, and in 1988, a giant magnetoresistive effect was discovered in a Fe / Cr artificial lattice by Baibich et al. In France (Rhys. Rev. .Lett. 61 (1988) 247
Starting from 2.), material development for metal multi-layer artificial lattices, etc. is being actively conducted.

[0004]

However, the magnetoresistive effect element such as the metal multi-layered film artificial lattice obtained so far has insufficient magnetic field sensitivity and has hysteresis, which causes a problem as a material of the magnetoresistive effect element. was there.

The present invention has been made in view of the above points, and an object thereof is to provide a multilayer magnetoresistive element having sufficient magnetic field sensitivity and small hysteresis.

[0006]

In order to solve the above problems, the inventor of the present application has found that in a multilayer magnetoresistive effect element such as a metal multilayer artificial lattice having a giant magnetoresistive effect, the direction of the easy axis of magnetization of each magnetic layer. We focused on controlling.

That is, first, when forming a magnetic layer of a multilayer magnetoresistive effect element in which magnetic layers and nonmagnetic layers are alternately laminated, an external magnetic field is applied only in one direction in the in-plane direction of the magnetic layer. Thus, the easy axis of magnetization along the direction of the applied magnetic field is induced in the film of the magnetic layer.

At that time, when the odd-numbered magnetic layers are formed, which are defined as the first magnetic layer, the second magnetic layer, and so on, in order from the magnetic layer closer to the underlying substrate on which the multilayer film is formed, When the even-numbered magnetic layer is formed, the external magnetic field is applied in about 90
Deposition was changed. As a result, a multi-layer film in which so-called perpendicular easy axes of magnetization are alternately induced is obtained.

From this multilayer film, the characteristics of high magnetic field sensitivity and very small hysteresis were obtained. This characteristic is particularly remarkable in a multilayer film having a large magnetic layer thickness.

The magnetic layer at this time is not particularly limited to the kind of magnetic element, but a single film made of any one of Ni, Fe and Co or an alloy film made of two or more kinds of elements is preferable.

On the other hand, the non-magnetic layer is not particularly limited to the kind of non-magnetic element, but is preferably a single film made of any one of Cu, Ag and Au or an alloy film made of two or more kinds of elements.

The number of laminations when the magnetic layer and the non-magnetic layer are set as one is advantageous as large as possible in view of the magnetoresistive effect, but the number of laminations can be kept while maintaining the interface state and the film structure uniform. Since it is very difficult to increase the number of layers, it is actually preferable to set the number of laminations to a range of 2 to 70 times.

The method for forming the multilayer film of the present invention is not particularly limited, but an ion beam sputtering method, an RF magnetron sputtering method, an electron beam evaporation method, a molecular beam epitaxy method and the like are preferable.

The underlying substrate on which the multilayer film is formed may be either crystalline or amorphous.

The method of applying the external magnetic field applied during the formation of the multilayer film is not particularly limited, but it is preferable to use a permanent magnet having good thermal stability with respect to the output magnetic field, and regarding the magnitude of the applied magnetic field, It is necessary to change it appropriately depending on the magnetic characteristics of the magnetic layer employed, but 10 (Oe) or more is preferable.

[0016]

With the above-described structure, a multilayer magnetoresistive element having a sufficient magnetic field sensitivity and exhibiting a large rate of change in resistance of several percent to several tens of percent can be obtained by simply applying an external magnetic field as small as several tens Oe. Was obtained. Moreover, there was almost no difference in magnetic field sensitivity between the minor loop and the major loop on the magnetoresistance curve. Therefore, it is possible to provide an MR sensor or the like that detects an external magnetic field with high sensitivity and good reproducibility.

[0017]

Embodiments of the present invention will now be described in detail with reference to the drawings.

Example 1 An ion beam sputtering apparatus was used to form a multilayer magnetoresistive effect element.

Here, FIG. 1 is a schematic configuration diagram showing a state in the chamber of the ion beam sputtering apparatus. As shown in the figure, an ion source 10, a target 20, and a substrate holder 30 are installed in the chamber of the ion beam sputtering apparatus.

Here, as the target 20, a NiFeCo alloy for the magnetic layer is used.

The substrate holder 30 houses a stepping motor 33 in a case 31, a stage 35 is fixed to a rotation shaft of the stepping motor 33, and S _m C is provided on one end surface of the case 31 on both sides of the stage 35. _{The o-} system permanent magnets 37 and 39 are fixed. Therefore, the magnetic field is always applied in the direction from the permanent magnet 37 to the permanent magnet 39 through the stage 35. Then, on the stage 35, a glass substrate 41 serving as a base for forming a multilayer film is fixed.

The entire substrate holder 30 rotates in the direction of arrow A, and faces the other target (specifically Cu is used) for forming a nonmagnetic layer (not shown) and the ion source. It has a mechanism.

Then, from the ion source 10 to the target 2
Ions are emitted toward 0 to knock out particles from the target 20 to form a film on the glass substrate 41, thereby forming the first magnetic layer. During this film formation, the permanent magnet 37 is used. , 39, the magnetic field is applied,
An easy axis of magnetization is induced in the magnetic layer in the direction of the applied magnetic field.

Here, the easy axis of magnetization means an axis which is easily magnetized in the direction when a magnetic field is applied to the formed film.

Next, the entire substrate holder 30 is rotated in the direction of arrow A to form a non-magnetic layer consisting of a Cu layer on the first magnetic layer by an ion source and a target (Cu) not shown. To do.

Next, the substrate holder 30 is returned to the original position (the position shown in FIG. 1), and the stepping motor 33 is driven to rotate the stage 35 by 90 °. Then, in this state, the second magnetic layer is formed again on the non-magnetic layer by sputtering. At this time, the stage 35 is 90 °
Since it rotates, the easy axis of magnetization is induced in the second magnetic layer in a direction orthogonal to the first magnetic layer.

Similarly, the substrate holder 30 is similarly rotated in the direction of arrow A to form a non-magnetic layer on the second magnetic layer, and then the substrate holder 30 is returned to its original position and the stepping motor is used. 33 is driven to rotate the stage 35 back to the original position to form the third magnetic layer.

By repeating this operation, as shown in FIG. 2, the nonmagnetic layer 43 is sandwiched on the glass substrate 41, and the magnetic easy axis is alternately guided in the stacking order in the directions substantially orthogonal to each other. , 47, 49 are formed.

[0029] The on-current is 60 mA, and the alloy composition of the magnetic layer is Ni.
₆₃ Fe ₁₂ Co ₂₅ (at%), and the sputter rate is 1.1 Å / sec for NiFeCo alloy and 1.8 Å / sec for Cu.

The multilayer film formed under the above conditions is actually a Ni ₆₃ Fe buffer layer on the glass substrate.
After laminating 50 Co of ₁₂ Co ₂₅ , Ni ₆₃ Fe ₁₂ Co ₂₅ (t
₁ Å) and Cu (t ₂ Å) are alternately laminated in this order for 20 cycles,
Finally, Ni ₆₃ Fe ₁₂ Co ₂₅ (t ₁ Å) is laminated. Hereinafter, this multilayer film is described as follows.

Ni ₆₃ Fe ₁₂ Co ₂₅ (t ₁ Å) [Cu (t ₂
Å) / Ni ₆₃ Fe ₁₂ Co ₂₅ (t ₁ Å)] ₂₀ // Ni ₆₃ F
e ₁₂ Co ₂₅ (50 Å) However, 8 ≦ t ₁ ≦ 30 and 8 ≦ t ₂ ≦ 75.

In this embodiment, the magnetic field applied by the permanent magnets 37 and 39 (about 200
A multilayer magnetoresistive effect element was produced by controlling the (Oe)) direction, and the present inventor hereinafter refers to this multilayer magnetoresistive effect element as "orthogonal biaxial anisotropic film formation", while applying a magnetic field at all. Without the multilayer film magnetoresistive effect element
Hereinafter, they are called "normal film formation" for distinction, and various characteristics of both are compared.

First, X in the orthogonal biaxial anisotropic film formation and the normal film formation
The measurement was performed on the small-angle linear diffraction pattern, but there was no big difference between the two, and a primary peak corresponding to the stacking period was observed, and both were confirmed to have the same periodic structure.

Regarding the X-ray medium angle diffraction pattern,
As shown in FIG. 3, there was not much difference between the two, and a strong diffraction line corresponding to (111) of the artificial lattice and a weak and broad (200) diffraction line were seen.

Next, FIG. 4 shows an orthogonal biaxial anisotropic film formation in which the thickness of the magnetic layer is fixed at 10Å and the thickness of the nonmagnetic layer is changed within the range of 8 <t ₂ <75 (Å). It is a figure which shows and measures the electrical resistivity ρ at the time of saturation by a magnetic field, the variation Δρ due to the magnetic resistance, and the magnetoresistance change rate MR ratio of each normal film formation.

As shown in the figure, the electrical resistivity ρ was generally slightly higher in the orthogonal biaxial anisotropic film formation than in the normal film formation.

Regarding the variation Δρ due to the magnetoresistance and the magnetoresistance change rate MR ratio, the vibration phenomenon depending on the non-magnetic layer thickness, which is a feature of the metal multilayer magnetoresistive effect element having a giant magnetoresistive effect, is orthogonal. The same was confirmed for both the axial anisotropic film formation and the normal film formation.

FIG. 5 shows the first peak and the second peak of this vibration phenomenon.
FIG. 13 is a diagram showing the results of comparing the difference in characteristics between orthogonal biaxial anisotropic film formation and normal film formation with respect to magnetic field sensitivity (ΔMR / ΔH), paying particular attention to the peak.

As shown in the figure, it was confirmed that the orthogonal biaxial anisotropic film formation exceeded the normal film formation for both the first peak and the second peak.

Next, FIGS. 6 and 7 show the shape of the magnetoresistive curve when the thickness of Cu which is the non-magnetic layer is fixed at the value of the second peak and the magnetic layer thickness X is increased. It is a figure shown in comparison, FIG. 6 has shown the curve of normal film formation, and FIG. 7 has shown the curve of orthogonal biaxial anisotropic film formation.

In the figure, 0 to 30 for each magnetic layer thickness X
The rate of change in magnetoresistance with respect to a change in the magnetic field of 0 (Oe) is MR r
It is indicated by atio.

Generally, in a metal multilayer magnetoresistive element, when the nonmagnetic layer thickness is made constant and the magnetic layer is enlarged,
The effect of Zeeman energy increases while the interlayer coupling energy remains constant, resulting in a smaller saturation field. At this time, the effect of enlarging the magnetic layer simultaneously appears as a shunt effect, and the rate of change in magnetoresistance becomes small.

However, if the reduction of the saturation magnetic field and the reduction of the magnetoresistance change rate are balanced, the improvement of magnetic field sensitivity can be expected. 6 and 7 show the tendency due to the increase in the magnetic layer thickness, and the following table shows a comparison of the maximum magnetic field sensitivity at each magnetic layer thickness. Magnetic layer thickness Normal film formation Orthogonal biaxial anisotropic film formation 10Å 0.09 0.11 16Å 0.13 0.15 23Å 0.22 0.25 (unit:% / Oe)

From this table, it can be seen that the magnetic field sensitivity is improved as the thickness of the magnetic layer is increased.

Particularly, in the orthogonal biaxial anisotropic film formation according to the present invention, the magnetic field sensitivity is 0.11 (% / Oe) to 0.25.
(% / Oe). Moreover, the tendency that the coercive force increases as the thickness of the magnetic layer increases (which appears in the difference between the curves when the magnetic field increases and when the magnetic field decreases), which is seen in the normal film formation of FIG. It was not seen in anisotropic film formation.

In a film having a large coercive force, hysteresis occurs in the magnetic resistance curve, and the magnetic field sensitivity measured on the minor loop due to hysteresis is generally compared with the magnetic field sensitivity measured on the major loop of the magnetic resistance curve. Becomes smaller.

As described above, in the orthogonal biaxial anisotropic film formation according to the present invention, the hysteresis becomes small, and the hysteresis does not reduce the magnetic field sensitivity.

If a minor loop appears largely in the magnetic resistance curve, when the external magnetic field is increased or decreased in two different ranges, two minor loops corresponding to the respective external magnetic fields appear and the magnetic resistance value for one external magnetic field is increased. Will be more than one.

FIG. 8 shows that Ni ₆₃ Fe ₁₂ Co ₂₅ (5Å) [C
u (24Å) / Ni ₆₃ Fe ₁₂ Co ₂₅ (23Å)] ₂₀ //
Shows a comparison of the minor loops on the magnetoresistance curve using samples of _{Ni 63 Fe 12 Co 25 (50Å} ). The external magnetic field for the sample is lowered from 0 (Oe) to -20 (Oe), then the range of -10 (Oe) and -20 (Oe) is increased or decreased 4 times, and then lowered to -300 (Oe). The measurement was performed by the method.

As shown in FIG. 8, the minor loop is more prominent in the normal film formation, but in the orthogonal biaxial anisotropic film formation according to the present invention, the minor loop is almost on the major loop, and the external magnetic field and the magnetic field are large. It was confirmed that the resistance values corresponded almost one-to-one.

[Example 2] In Example 2, the method of applying an external magnetic field during film formation was changed and the same film forming conditions as in Example 1 were used, and Ni ₆₃ Fe ₁₂ Co ₁₈ (16Å) [Cu ( 22
Å) / Ni ₆₃ Fe ₁₂ Co ₂₅ ] ₂₀ sample was prepared and the difference in the characteristics was compared.

That is, there are three types of methods of applying an external magnetic field during film formation, one is the method of orthogonal biaxial anisotropic film formation as in Example 1, and the second is the method of laminating magnetic layers. By changing the direction of application of the external magnetic field by 45 ° in the same rotation direction in the film plane (hereinafter, the multilayer magnetoresistive effect element manufactured by this method is referred to as "45 degree composite anisotropic film formation"). The third method is to change the application direction of the external magnetic field by 180 ° each time the magnetic layers are laminated (hereinafter, the multi-layered magnetoresistive element manufactured by this method is referred to as "uniaxial anisotropic film formation").
Is called).

The results of the magnetic resistance curves of the 45-degree composite anisotropic film formation, the uniaxial anisotropic film formation, and the orthogonal biaxial anisotropic film formation are shown in the order of FIGS. 9, 10 and 11. In these figures, the solid line shows the case where the applied current and the external magnetic field are parallel, and the broken line shows the case where the applied current and the external magnetic field are vertical.

From these figures, 0 (Oe) to 300
Regarding the MR ratio MR ratio in the range of (Oe), there was almost no difference between the three, but 0
When the maximum magnetic field sensitivity in the range of (Oe) to 40 (Oe) was examined, the results were as follows. 45-degree composite anisotropic film formation 0.14 (% / Oe) uniaxial anisotropic film formation 0.20 (% / Oe) orthogonal biaxial anisotropic film formation 0.19 (% / Oe)

That is, the uniaxial anisotropic film formation and the orthogonal biaxial anisotropic film formation exhibited relatively high magnetic field sensitivity. However, as can be seen from FIG. 10, the uniaxial anisotropic film formation has a large hysteresis, and it has been confirmed that the shape of the magnetoresistance curve changes depending on the angle between the applied current and the application direction of the external magnetic field. On the other hand, in the case of the orthogonal biaxial anisotropic film formation according to the present invention,
Hysteresis was small, and there was no change in the magnetoresistance curve depending on the angle between the applied current and the applied direction of the external magnetic field. That is, the best result was obtained by making the easy magnetization axes orthogonal to each other as in the present invention.

[0056]

As described above in detail, according to the present invention, a multilayer magnetoresistive effect element having a sufficient magnetic field sensitivity and exhibiting a large resistance change rate can be obtained by applying a small external magnetic field, and the magnetic field The excellent effect that there is almost no difference in the magnetic field sensitivity between the minor loop and the major loop on the resistance curve.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing a state inside a chamber of an ion beam sputtering apparatus for manufacturing a multilayer magnetoresistive effect element according to the present invention.

FIG. 2 is a diagram showing a schematic structure of a multilayer magnetoresistive effect element according to the present invention.

FIG. 3 is a diagram showing X-ray mid-angle diffraction patterns of orthogonal biaxial anisotropic film formation and normal film formation, respectively.

FIG. 4 shows electrical resistivity ρ at the time of saturation due to a magnetic field and change Δ due to magnetic resistance in each of orthogonal biaxial anisotropic film formation and normal film formation.
It is a figure which shows (rho) and magnetoresistance change rate MR ratio.

FIG. 5 is a diagram showing magnetic field sensitivities of orthogonal biaxial anisotropic film formation and normal film formation.

FIG. 6 is a diagram showing a magnetoresistive curve for normal film formation.

FIG. 7 is a diagram showing a magnetoresistive curve of an orthogonal biaxial anisotropic film formation.

FIG. 8 is a diagram showing a comparison of a minor loop on a magnetoresistive curve between normal film formation and orthogonal biaxial anisotropic film formation.

FIG. 9 is a diagram showing a magnetoresistance curve of a 45-degree composite anisotropic film formation.

FIG. 10 is a diagram showing a magnetoresistance curve of uniaxial anisotropic film formation.

FIG. 11 is a diagram showing a magnetoresistive curve of an orthogonal biaxial anisotropic film formation.

[Explanation of symbols]

 43 non-magnetic layer 45, 47, 49 magnetic layer

Claims (2)

[Claims] 1. A multilayer magnetoresistive element comprising a magnetic layer and a non-magnetic layer alternately laminated, wherein each laminated magnetic layer is guided in a direction in which the easy axes of magnetization are alternately crossed in a direction substantially orthogonal to each other. A multi-layered magnetoresistive effect element. 2. A method for manufacturing a multilayer magnetoresistive effect element in which both steps of forming a magnetic layer and a nonmagnetic layer are alternately performed to stack both layers, wherein the magnetic layer is formed. In the film forming step, an external magnetic field is applied to induce the easy axis of magnetization of the magnetic layer in the application direction of the external magnetic field, and the application direction of the external magnetic field when forming the odd-numbered magnetic layer and the even direction A method of manufacturing a multilayer magnetoresistive effect element, characterized in that the directions of application of an external magnetic field at the time of forming the th magnetic layer are made substantially orthogonal to each other.