JPH10173252A - Magneto-resistance effect element and magneto-resistance sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a large rate of magneto-resistance change from the magnetic field variation of a small external signal having a small hysteresis by laminating a magnetic layer having a high electric resistance on a magnetic layer which is not formed on an insulating antiferromagnetic layer. SOLUTION: A magneto-resistance effect element is constituted by successively forming an insulating antiferromagnetic layer 13, a magnetic layer 15, a nonmagnetic conductor layer 17, and a magnetic layer on a nonmagnetic insulating surface 11 in this order by sputtering and a magnetic layer 20 having a high electric resistance on the magnetic layer 19. It is preferable to form the magnetic layer 20 by using a cobalt-aluminum oxide (Cox Al1-x-w Ow ) and setting the (x) and (w) to meet such conditions that 50<=x<=85at.% and 10<w<50at.%. It is also preferable to use a nickel oxide for forming the insulating antiferromagnetic layer and a nickel-iron-cobalt alloy, nickel-iron alloy, cobalt, or cobalt-iron alloy for forming the magnetic layers, and then, copper for forming the nonmagnetic layer 17.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetoresistive element having a small hysteresis and excellent characteristics and a magnetoresistive sensor using the same.

[0002]

2. Description of the Related Art Conventionally, a magnetoresistance effect element has been used as an element for detecting a change in a magnetic field. As this type of magnetoresistive element, a spin valve type magnetoresistive element has been proposed.

As shown in FIG. 8, this spin valve type magnetoresistive element has an insulating antiferromagnetic layer 13, a magnetic layer 15, a nonmagnetic conductor layer 17, and a magnetic layer on a nonmagnetic insulating substrate 11. 19 are laminated in this order.

When the direction of the magnetic field is changed in a plane parallel to the magnetoresistive element, an MR characteristic curve (ΔR / RH characteristic curve) as shown in FIG. 9 is obtained.
In the conventional example according to this experiment, a 50 nm-thick nickel oxide is used as the insulating antiferromagnetic layer 13, a 10 nm-thick nickel-iron-cobalt alloy is used as the magnetic layer 15, and the nonmagnetic conductor layer 17 is used as the nonmagnetic conductor layer 17. Copper having a thickness of 2.5 nm was used, and a nickel-iron-cobalt alloy having a thickness of 5 nm was used as the magnetic layer 19.

That is, when the magnetic field H is not applied to the magnetoresistive element in the surface direction at all or is applied in the minus direction, the resistance value R is substantially constant and does not change. Next, when the magnetic field H is applied in the plus direction, the resistance value R increases in a steep curve at a magnetic field H of about +50 (Oe) and reaches a predetermined value. The resistance value R is constant and does not change even if the strength of R is increased. However, when the magnetic field H exceeds +250 (Oe), the resistance value R sharply decreases and returns to the original value.

Conversely, when the intensity of the magnetic field H is reduced from around +400 (Oe), the resistance value R gradually increases, and when the magnetic field H decreases to about -20 (Oe), the resistance value R sharply increases. And almost return to the original value.

[0007] The above phenomenon is explained as follows. That is, as shown in FIG. 10A, when no external magnetic field H is applied in the plane direction of the magnetoresistive element at all, it is assumed that the magnetization directions in the upper and lower magnetic layers 15 and 19 are in the same direction. The resistance value between both ends of the magnetoresistive element is a predetermined resistance value R.

Next, a magnetic layer 15,
When an external magnetic field H1 (a magnetic field directed in the negative direction) in the same direction as the direction of the magnetization in 19 is applied, the magnetic layers 15 and 1
Since the direction of the magnetization in 9 does not change, the resistance value R between both ends of the magnetoresistive effect element hardly changes.

On the other hand, as shown in FIG. 10B, when an inverted external magnetic field H2 (magnetic field directed in the plus direction) is applied to this magnetoresistive effect element, even if the external magnetic field H2 is small [+50 in this conventional example]. (Oe) degree] The direction of the magnetization in the magnetic layer 19 reacts immediately and changes the direction of the magnetization to the same direction as the direction of the external magnetic field H2.

However, as described above, the lower magnetic layer 1
The magnetization direction of No. 5 does not reverse under the influence of the exchange bias of the insulating antiferromagnetic layer 13.

For this reason, the two stacked magnetic layers 15 and 19
Since the directions of the internal magnetization are opposite, the conductive magnetic layers 15 and 19 and the non-magnetic conductor layer 1 of the magnetoresistive element are formed.
7, it becomes difficult for electrons to pass through, and the resistance value R increases.

If the intensity of the external magnetic field H2 is further increased, the direction of the magnetization of the magnetic layer 15 is eventually reversed, so that the directions of the magnetization in the two magnetic layers 15 and 19 become the same, and the resistance R Suddenly returns to its original value, but the strength of the external magnetic field H2 for this is considerably large, and is +250 (Oe) or more in this conventional example. The same applies to the case where the strength of the external magnetic field is reduced. From the above, the MR characteristics of this magnetoresistive effect element are as shown in FIG.

[0013]

However, if the thickness of the magnetic layer 19 whose magnetization direction can be freely changed is small, the intensity of magnetization is small, and the lower magnetic layer 1
5 and the influence of the magnetic field of the insulating antiferromagnetic layer 13 and the influence of the surface interface, and cannot respond sensitively to changes in the external magnetic field.
As shown in FIG. 9, the hysteresis increases.

The remarkable magnetoresistance effect occurs in the vicinity of the interface between the magnetic layer 19 and the nonmagnetic conductor layer 17, so that
Even if the thickness of the magnetic layer 19 is increased to increase the strength of the magnetization, it is not effective because the portion that does not contribute to the magnetoresistance effect increases and the current that does not contribute to the magnetoresistance effect increases.

As shown in FIG. 9, the conventional spin-valve magnetoresistive element has a large hysteresis and a width of about 100 (Oe). Therefore, the change width of the external signal magnetic field is also 100 (Oe). Unless a material having a magnetoresistance of about 4% or more is used, a magnetoresistance change rate (ΔR / R) of about 4% cannot be obtained.

However, a practical change width of the external signal magnetic field is 50 (Oe) or less. In the above-mentioned conventional example, a change rate of the external signal magnetic field of this level results in a small rate of change in magnetoresistance, which is practically applicable. Did not.

The present invention has been made in view of the above points, and an object of the present invention is to provide a magnetoresistive element and a magnetoresistive sensor which have a small hysteresis and can obtain a large magnetoresistance change rate from a small change in an external signal magnetic field. Is to do.

[0018]

In order to solve the above problems, a magnetoresistive element according to the present invention comprises an insulating antiferromagnetic layer, a magnetic layer, a nonmagnetic conductor layer and a magnetic layer laminated in this order. The magnetoresistive effect element is formed by laminating a high electric resistance magnetic layer on a magnetic layer not adjacent to the insulating antiferromagnetic layer. This improves the response to changes in the external signal magnetic field, and reduces the hysteresis. As the high electric resistance magnetic layer, cobalt aluminum oxide {Co _(x) Al _(1-xw) O _(w) } is used, and x and w are set as follows: 50 ≦ x ≦ 85 at% 10 <w <50 at % Is preferably satisfied. The insulating antiferromagnetic layer is formed of nickel oxide, the magnetic layer is formed of nickel-iron-cobalt alloy or nickel-iron alloy or cobalt or cobalt-iron alloy, and the nonmagnetic conductor layer is formed of copper. Is preferred. Further, the magnetoresistive sensor according to the present invention is configured by using the magnetoresistive effect element in at least a part thereof.

[0019]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is an enlarged schematic cross-sectional view of a spin-valve magnetoresistive element according to one embodiment of the present invention. As shown in the figure, this magnetoresistive effect element comprises an insulating antiferromagnetic layer 13, a magnetic layer 15, and a nonmagnetic conductor layer 1 formed on a nonmagnetic insulating substrate 11 by sputtering.
7 and the magnetic layer 19 are laminated in this order.
9, a high electric resistance magnetic layer 20 is laminated.

Here, the non-magnetic insulating substrate 11 is made of a glass plate.

Next, the insulating antiferromagnetic layer 13 has a thickness of 50.
(Nm) of nickel oxide (NiO), and the magnetic layer 15 has a thickness of 10 (nm) of nickel / iron / nickel.
The nonmagnetic conductor layer 17 is formed of a cobalt alloy (Ni-Fe-Co), and the nonmagnetic conductor layer 17 is made of copper (C) having a thickness of 2.5 (nm).
u), and the magnetic layer 19 has a thickness of 2.5
(Nm) nickel-iron-cobalt alloy (Ni-Fe-
Co) and the high electric resistance magnetic layer 20.
Is a 10-nm-thick cobalt aluminum oxide (C
o-Al-O).

By configuring the magnetoresistive element as described above, when the direction of the magnetic field is changed in a plane parallel to the plane of the magnetoresistive element, the MR characteristic curve (ΔR / RH characteristic curve).
The resistance value R is a resistance value between both ends of the magnetoresistive element.

As shown in the figure, according to this magnetoresistance effect element, the magnetoresistance change rate (ΔR / R) is as high as 4.2%, and the width of hysteresis is as small as about 20 (Oe). It is stable until an externally applied magnetic field of about +100 (Oe) is applied.

This phenomenon can be explained as follows. That is, since the thickness of the magnetic layer 19 itself is small, the intensity of magnetization is small. However, the high electric resistance magnetic layer 20 formed thereon is easily magnetized similarly to the magnetic layer 19, and changes its magnetization direction together with the magnetic layer 19 in response to a change in an externally applied magnetic field. It can be applied to the magnetic layer 19, which can reinforce the small magnetization strength of the magnetic layer 19.

For this reason, the magnetic layer 19 is not dragged by the influence of the magnetic field of the lower magnetic layer 15 or the insulating antiferromagnetic layer 13 and can respond to a change in an externally applied magnetic field. .

On the other hand, since the high electric resistance magnetic layer 20 has a high resistance value, almost no current flows through the inside thereof. That is, the current does not increase in portions other than the portion near the interface between the magnetic layer 19 and the nonmagnetic conductor layer 17 that contributes to the magnetoresistance effect.

As described above, the rate of change in magnetoresistance can be increased, and the hysteresis can be reduced in response to changes in the external magnetic field.

FIG. 3 is an enlarged perspective view of the magnetoresistive sensor 10 using the magnetoresistive element according to one embodiment of the present invention. As shown in FIG. 1, the magnetoresistive sensor 10 has a magnetoresistive pattern 21 formed by linearly forming a magnetoresistive element having the structure shown in FIG. Non-magnetic insulating substrate 1
A dummy resistance pattern 31 is formed on another side of one surface,
Further, three electrode patterns 41, 43, and 45 are formed on another side, the electrode pattern 41 is connected to one end of the dummy resistance pattern 31, and the electrode pattern 43 is moved closer to the magnetoresistive pattern 21 and the dummy resistance pattern 31, respectively. The electrode pattern 45 and the magnetoresistive pattern 2
1 is connected to the other end. The dummy resistance pattern 31 has exactly the same structure and dimensions as the magnetoresistive pattern 21.

Then, as shown in FIG. 4, the magnetoresistive sensor 10 is installed near the outer peripheral side surface of the rotating body 40. Note that N and S magnetic poles are alternately provided at equal intervals on the outer peripheral side surface of the rotating body 40 in the rotating direction. At this time, the magnetoresistive pattern 21 of the magnetoresistive sensor 10 is made to approach the outer peripheral side surface of the rotating body 40, and the dummy resistance pattern 31 is located at a position away from the outer peripheral side surface. That is, the magnetic field of the rotator 40 is applied only to the magnetoresistive pattern 21 and is hardly applied to the dummy resistance pattern 31.

An electric circuit as shown in FIG. 5 is connected to the magnetoresistive sensor 10. That is, the electrode pattern 41 shown in FIG. 3 is connected to the power supply voltage Vcc, the electrode pattern 45 is grounded, the electrode pattern 43 which becomes the midpoint potential Vb of the magnetoresistive pattern 21 and the dummy resistance pattern 31 is taken out, and the comparator 50 (Schmitt. Trigger circuit)
To enter. The dummy resistance pattern 31 is provided so that the midpoint potential Vb does not change with temperature by matching the temperature coefficient with the magnetic resistance pattern 21.

When the rotating body 40 shown in FIG. 4 is rotated, the direction of the magnetic field incident on the magnetoresistive pattern 21 of the magnetoresistive sensor 10 changes periodically into a substantially sin wave shape, as shown in FIG. Then, the resistance value of the magnetoresistive pattern 21 changes to a substantially square wave shape.

Therefore, the midpoint potential Vb shown in FIG. 5 also has a square wave shape, and the output voltage is shaped into a regular square wave by the comparator 50. Thereby, the rotation state of the rotating body 40 can be detected.

Meanwhile, the entire waveform of the midpoint potential Vb of the square wave shape fluctuates upward (or downward), and the comparator 50
Is larger (or smaller) than the reference voltage Va, since the waveform of the midpoint potential Vb is substantially a square wave,
The inversion position of the potential by the comparator 50 is the midpoint potential Vb.
, And the ON-OFF ratio of the output waveform of the comparator 50 hardly changes.

On the other hand, the distance G between the magnetoresistive pattern 21 of the magnetoresistive sensor 10 shown in FIG.
When an external magnetic field with a larger amplitude than the standard is applied to
Or, conversely, the separation distance G increases and the magnetoresistive pattern 2
Even when an external magnetic field having a small amplitude is applied to the external signal, the amplitude of the external magnetic field is approximately 20 (Oe) as shown in FIG.
The output signal in any case within the range of １００100 (Oe) is almost the same as the standard output signal and does not change.

That is, according to the present embodiment, the midpoint potential Vb
The body itself fluctuates, and the rotating body 40 and the magnetoresistive sensor 1
Even if the separation distance of 0 fluctuates, an accurate output waveform from the comparator 50 is always obtained.

The present invention is not limited to the above embodiment, and various modifications as described below are possible. As shown in FIG. 7, the magnetoresistive element includes a high electric resistance magnetic layer 20, a magnetic layer 19, a nonmagnetic conductor layer 17, a magnetic layer 15, and an insulating antiferromagnetic layer 13 on a nonmagnetic insulating substrate 11. You may comprise by laminating in this order. In the case of such a configuration, the upper magnetic layer 15 is in contact with the insulating antiferromagnetic layer 13 so that the upper magnetic layer 15 is less susceptible to a change in the external magnetic field than the lower magnetic layer 19. Can be obtained.

As the material of each layer constituting the magnetoresistive element, other materials may be used. For example, as the magnetic layer, for example, a nickel-iron alloy or cobalt or cobalt-cobalt alloy besides nickel-iron-cobalt alloy An iron alloy may be used.

Further, as the high electric resistance magnetic layer, cobalt rare earth oxide, iron rare earth oxide, iron hafnium oxide, iron silicon oxide, cobalt iron boron oxide, cobalt iron boron fluoride, or the like may be used.

In the above embodiment, the rotating body 40 is used as the object to be detected. However, it is needless to say that the rotating body 40 may move linearly.

[0040]

As described in detail above, according to the present invention, a large rate of change in magnetoresistance can be obtained with a small external signal magnetic field, and the hysteresis can be reduced.

Further, according to the magnetoresistive sensor according to the present invention, since an external magnetic field having a sin waveform can be directly converted into a square wave signal, an excellent effect that a square wave output signal can be obtained easily and accurately can be obtained.

[Brief description of the drawings]

FIG. 1 is an enlarged schematic cross-sectional view of a spin-valve magnetoresistive element according to an embodiment of the present invention.

FIG. 2 is an MR characteristic curve diagram of the magnetoresistance effect element according to the present invention.

FIG. 3 is an enlarged perspective view of a magnetoresistive sensor 10 using the magnetoresistive element according to the present invention.

FIG. 4 is a diagram showing one usage example of the magnetoresistive sensor 10.

FIG. 5 is an electric circuit diagram connected to the magnetoresistive sensor 10.

FIG. 6 is a diagram showing a relationship between an external magnetic field and an output waveform.

FIG. 7 is an enlarged schematic cross-sectional view of a magnetoresistive element according to another embodiment of the present invention.

FIG. 8 is an enlarged schematic cross-sectional view of a conventional spin-valve magnetoresistive element.

9 is an MR characteristic curve diagram of the magnetoresistive element shown in FIG.

FIG. 10 is a diagram illustrating the operation principle of a magnetoresistive element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Magnetoresistive sensor 11 Nonmagnetic insulating substrate 13 Insulating antiferromagnetic layer 15 Magnetic layer 17 Nonmagnetic conductor layer 19 Magnetic layer 20 High electric resistance magnetic layer

Continuing from the front page (72) Inventor Haruo Ito 335 Karisuku, Nakahara-ku, Kawasaki-shi, Kanagawa Prefecture Inside Teikoku Telecommunications Industry Co., Ltd.

Claims (4)

[Claims] 1. A magnetoresistive element in which an insulating antiferromagnetic layer, a magnetic layer, a nonmagnetic conductor layer, and a magnetic layer are laminated in this order, wherein a magnetic layer not adjacent to the insulating antiferromagnetic layer is provided. A magnetoresistive element, wherein a high electric resistance magnetic layer is laminated on the layer. 2. The high electric resistance magnetic layer is a cobalt aluminum oxide {Co _(x) Al _(1-xw) O _(w) },
2. The magnetoresistive element according to claim 1, wherein x and w satisfy a condition of 50 ≦ x ≦ 85 at% and 10 <w <50 at%. 3. The insulating antiferromagnetic layer is nickel oxide, the magnetic layer is nickel-iron-cobalt alloy or nickel-iron alloy or cobalt or cobalt-iron alloy, and the nonmagnetic conductor layer is copper. The magnetoresistive element according to claim 1, wherein: 4. A magnetoresistive sensor, wherein the magnetoresistive element according to claim 1, 2 or 3 is used for at least a part thereof.