JP2000124522A - Magnetoresistive effect element and magnetic-field sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve operability between an element and external magnetic field by making a resistance changing rate represented by a specific formula to be negative when a specified external magnetic field is applied, and constituting the element in a manner that the absolute value of the resistance changing rate has a value of specific percentage or more. SOLUTION: A magnetoresistive effect element 1 has a laminated film structure in which a first magnetic layer 10 and a second magnetic layer 20 are joined with each other like a cross with a non-magnetic layer 30 interposed, and a resistance at the time when a current is applied vertically to the surface of the laminated film is made to change according to the application of external magnetic field. Assuming that the resistance value at the time when the external magnetic field Hs is applied is Rs and the resistance value at the time when the external magnetic field H (|Hs|>|H|) is applied is R, a resistance changing rate represented by a formula, (R-Rs)/Rs, is made negative, and its absolute value is made to be 5% or more. Thus, the operability between the element and external magnetic field can be improved.

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 laminated structure of a magnetic metal layer / non-magnetic layer / magnetic metal layer and a magnetic field sensor using the same, and more particularly to a magnetic field sensor using the same. The present invention relates to a magnetoresistive effect element using a phenomenon in which electric resistance changes depending on an external magnetic field strength, and a magnetic field sensor using the same.

[0002]

2. Description of the Related Art With the realization of a higher recording density in the field of magnetic recording, a magnetic head has been changed from a conventional inductive head based on electromagnetic induction to an AMR head based on anisotropic magnetoresistance effect (AMR). In addition, GMR heads utilizing the giant magnetoresistance effect (GMR) are rapidly shifting. Further, a magnetoresistive element having a high output is required not only in the field of magnetic recording but also in the field of sensors used for position control and speed control of movable parts of various electronic devices and optical devices.

In principle, AMR utilizes the fact that the electric resistance depends on the current and the direction of magnetization. On the other hand, GMR depends on the relative direction of magnetization of the magnetic layer.
In terms of materials, GMR uses a spin valve or antiferromagnetic coupling, uses the difference in coercivity of the magnetic layer,
And it is roughly divided into granular and the like. These GMR materials have a minimum when the magnetization directions of two adjacent magnetic layers are parallel, and have a maximum when the magnetization directions are antiparallel. In other words, the observed resistance change is a positive magnetic resistance change that is increased with respect to the magnetic field change with a minimum when a magnetic field that magnetically saturates the magnetic layer is applied.

When the AMR film and the GMR film are compared with attention to the MR change rate, the resistance change rate of the AMR film is 2%.
For example, a spin valve has a considerably large thickness of 5 to 8%, whereas the GMR film is as small as approximately 3%. However, when the change rate is as high as 8%, there is a problem in heat resistance and the like, and in reality, it is actually 5% or less.

In the device using the AMR film or the GMR film shown here, the change in the electric resistance with respect to the current (CIP) flowing in the film surface occurs when a magnetic field parallel to the film surface is applied. On the other hand, it has been reported that a perpendicular GMR film (CPP) in which a current flows perpendicularly to the film surface exhibits a larger resistance change (Phys. Rev. Lett. 70, 3343 (199).
3)). However, the Fe / Cr reported here
It can be said that the vertical GMR of the system has a practical problem because it has a small specific resistance and it is difficult to measure the electric resistance.

On the other hand, a tunnel junction magnetoresistive element (TMR) composed of a ferromagnetic metal layer / a non-magnetic insulating layer / a ferromagnetic metal layer, for example, a Fe / Al ₂ O ₃ / Fe junction film which has recently % TMR showing an MR change rate of as much as 1% has been reported (J. Magn. Magn. Mater. 139L231-L234, (1995)) and attracted attention.

In addition, similarly to the spin valve GMR, a spin valve type TMR in which one magnetic layer is pinned with an antiferromagnetic layer to control the direction of magnetization of the magnetic layer has been reported (Journal of the Japan Society of Applied Magnetics, 21 489-492). , (1997)).

In the TMR, the resistance changes depending on the relative directions of the magnetizations of the upper and lower magnetic layers with respect to the tunnel current flowing perpendicularly to the laminated film. Phenomenologically, also in TMR, the junction resistance depends on the relative angle of the magnetic layers, and becomes minimum when the magnetization directions of the two magnetic layers are parallel and becomes maximum when the magnetization directions are antiparallel. In the above-mentioned report example, a positive resistance change is observed based on this principle. That is, in any of the examples, the junction resistance observed for a magnetic field in which the magnetic layer is magnetically saturated is minimum, and the junction resistance increases with a change in the magnetic field. As described above, the TMR is similar to the GMR in that the resistance changes according to the relative angle of the magnetization and the resistance changes with respect to the magnetic field, but differs in many points such as the structure and the principle. For example,
In view of the structure of TMR, since current flows perpendicularly to the film surface, it is common that two strip-shaped magnetic layers are crossed to form a cross shape and joined via a non-magnetic insulating layer. .

The above-described magnetoresistive elements in the prior art are all magnetoresistive elements exhibiting a positive change in resistance to an external magnetic field, and generally exhibit such a positive change in resistance. Was thought to be. However, denying this general idea, and as a rare case, J. Appl. Phys. Vol. 76, 6104-6106 (1994)
Examples of devices exhibiting a negative magnetoresistance effect on a magnetic field have been reported. According to this report, the device has a shape that seems to be common in a TMR in which two first and second magnetic layers are arranged and joined so as to be orthogonal to a cross via a nonmagnetic oxide. However, it is reported that a negative resistance change rate of about -1% is exhibited only when the external magnetic field has an angle of 45 degrees with respect to the first and second magnetic layers. The magnetoresistance effect exhibiting a negative rate of change in resistance is an extremely peculiar phenomenon, and it is thought that the application range of the magnetoresistance effect element in the future will be greatly expanded.

However, since the magnetoresistance effect element exhibiting the above-described negative resistance change rate uses the AMR as its operating principle, its resistance change rate is as small as -1%, and is not practical. Further, the negative resistance change is limited to the case where the external magnetic field has an angle of 45 degrees with respect to the first and second magnetic layers. It can not be said.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of such a situation, and its object is to provide a device.
It is an object of the present invention to provide a magnetoresistive element having excellent operability between external magnetic fields and exhibiting a negative resistance change rate which is excellent in practical use. Another object of the present invention is to provide a high-output magnetic field sensor using this element.

[0012]

In order to solve such problems, the present invention has a laminated film structure in which a first magnetic layer and a second magnetic layer are joined via a non-magnetic layer. A magnetoresistive element whose electric resistance changes when an electric current is applied perpendicularly to the surface of the laminated film, by applying an external magnetic field, wherein the magnetoresistive element has a resistance when an external magnetic field Hs is applied. The value is Rs and the external magnetic field H (| Hs |>
When | H |) is applied and the resistance value is R, (R
−R s) / R s indicates a negative value of the rate of change of resistance and has an absolute value of 5% or more.

In a preferred embodiment of the present invention, the first magnetic layer and the second magnetic layer have a strip shape, and are joined in a cross shape via the nonmagnetic layer. Among the first magnetic layer and the second magnetic layer,
When at least one of the strip-shaped element portions has a line width of W and a length of L, the line width W is in the range of 80 to 200 μm and their aspect ratio (L / W) is 15 to 40. It is configured to be.

According to the magnetic field sensor of the present invention, an element exhibiting a negative resistance change and an element exhibiting a positive resistance change are combined,
It is configured to be used by performing a differential operation.

In a preferred embodiment of the present invention, the elements exhibiting a change in resistance used in the magnetic field sensor are each configured as a magnetoresistive element.

Further, as a preferred embodiment of the present invention, a device used in a magnetic field sensor, which exhibits a negative resistance change, is a laminated film in which a first magnetic layer and a second magnetic layer are joined via a non-magnetic layer. A magnetoresistive element having a structure, the electric resistance of which changes when an electric current flows perpendicularly to the surface of the laminated film by application of an external magnetic field.
Assuming that the resistance value when the external magnetic field Hs is applied is Rs and the resistance value when the external magnetic field H (| Hs |> | H |) is R, it is expressed as (R-Rs) / Rs. The resistance change rate shows a negative value, and its absolute value has a value of 5% or more.

In a preferred embodiment of the present invention, the first magnetic layer and the second magnetic layer of the element exhibiting a negative resistance change used in the magnetic field sensor have a strip shape, and The first magnetic layer and the second magnetic layer are joined in a cross shape through a magnetic layer, and at least one of the first magnetic layer and the second magnetic layer has a line width of a strip-shaped element portion of W,
When the length is L, the line width W is in the range of 80 to 200 μm, and their aspect ratio (L / W) is 15 to 4
It is configured to be zero.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an example of a preferred embodiment of a magnetoresistive element according to the present invention will be described with reference to FIG.

FIG. 1 is a schematic plan view of a magnetoresistive element 1 according to the present invention. As shown in FIG. 1, the magnetoresistive element 1 according to the present invention includes a first magnetic layer 10 and a second magnetic layer 10. It has a laminated film structure in which the magnetic layer 20 is joined in a cross shape through the non-magnetic layer 30.

First magnetic layer 10 and second magnetic layer 20
Are substantially strip-shaped substantial element portions 11 and 2 respectively.
1 which are joined at a substantially central portion via a non-magnetic layer 30. At both ends of the element portions 11 and 21, the connection wide ends 15, 15, and 25, 2 for mainly connecting the DC power supply 40 and the voltmeter 50, respectively.
5 are formed.

Then, such a magnetoresistive element 1
Acts so that the resistance when a current flows perpendicularly to the surface of the laminated film (perpendicular to the plane of the paper) is changed by the application of an external magnetic field. Rs and the external magnetic field H
(Where | Hs |> | H |) is R, the resistance change rate represented by (R−Rs) / Rs is a negative value and the absolute value is 5 %. Here, | Hs | and | H | indicate the absolute values of the external magnetic fields Hs and H, respectively.

As a particularly preferred form of the magnetic layers 10 and 20 for supporting such a configuration, as shown in FIG. 1, the line width of the strip-shaped element portion 11 of the first magnetic layer 10 is set to W. ₁ , when the length is L ₁ , the aspect ratio (L ₁ / W ₁ ) is 15 to 40, and the line width W ₁
Is desirably in the range of 80 to 200 μm.

This relationship is the same for the second magnetic layer 20, and as shown in FIG.
Assuming that the line width of the strip-like element portion 21 of 0 is W ₂ and the length is L ₂ , their aspect ratio (L ₂ / W ₂ ) is 15
And the line width W ₂ is desirably in the range of 80 to 200 μm.

The positional relationship between the external magnetic field H to be measured and the cross-shaped magnetoresistive element 1 of the present invention is not particularly limited, but as shown in FIG. It is desirable that one of the magnetic layers is arranged in parallel to the direction. With such a parallel arrangement, a larger negative resistance change rate can be obtained.

The device of the present invention may be manufactured by using a vacuum film forming method such as a sputtering method or a vapor deposition method, and performing patterning with a metal mask when forming the film.

FIG. 1 shows the resistance change rate of the device according to the present invention.
The two magnetic layers 10 and 20 are driven by a DC power supply 40 shown in FIG.
The resistance may be measured by applying a voltage between them and flowing a current flowing perpendicularly to the film surface. The resistance measured in the present invention changes by the application of an external magnetic field as described above,
The maximum rate of change has a value of -5% or more.

It is not clear whether such a large negative resistance change is caused by TMR using a nonmagnetic insulating layer as a tunnel barrier or by vertical GMR in which a current flows through an imperfect insulating layer. The principle that the negative magnetoresistance effect is observed is presumed to be due to the effect of magnetic anisotropy due to shape, the effect of magnetization pinning due to magnetic domains, and the like.

For example, as shown in FIG. 1, the first magnetic layer 10 and the second magnetic layer 20 are orthogonal to each other in a cross shape, and the axis of easy magnetization of the first magnetic layer 10 has a shape magnetic anisotropy. , The case where an external magnetic field H is applied in the longitudinal direction of the magnetic layer and in a direction perpendicular to the first magnetic layer 10. When the shape of the magnetic layer has an extreme ratio of the length and width of the strip (for example, in the case of the above aspect ratio of 15 to 40), the axis of easy magnetization becomes the longitudinal direction, and the magnetization is pinned in the longitudinal direction due to the shape magnetic anisotropy. Is done.

Therefore, even when a magnetic field in the orthogonal direction is applied to the first magnetic layer 10, the first magnetic layer 1 orthogonal to the magnetic field
0 does not saturate, and the magnetization of the first magnetic layer 10 and the magnetization of the second magnetic layer 20 parallel to the magnetic field do not become parallel. However,
Immediately after the sign of the magnetic field reverses from positive to negative or from negative to positive, the two magnetic layers 10 and 20 are arranged in an area where the magnetization of the magnetic layer 20 parallel to the magnetic field reverses with the reversal of the external magnetic field.
Are considered to be parallel and the resistance is minimized. That is, it is considered that the magnetoresistance effect element of the present invention exhibits a negative resistance change in which the resistance value becomes minimum when the magnetization of the magnetic layer 20 parallel to the magnetic field is reversed.

When the second magnetic layer 20 has an easy axis of magnetization in the longitudinal direction due to the shape magnetic anisotropy, a similar change in magnetoresistance occurs in a magnetic field in a direction perpendicular to the second magnetic layer. it is conceivable that.

As described above, the direction of the external magnetic field need not necessarily be applied in a direction perpendicular to the magnetic layer controlled by the shape magnetic anisotropy. Also, at least one of the first and second magnetic layers only needs to have the easy axis of magnetization oriented in the longitudinal direction due to shape magnetic anisotropy. It may be.

Incidentally, the magnetoresistance effect element of the present invention is generally formed on a substrate. The substrate is not particularly limited, and a glass single substrate, a silicon single crystal substrate, a thermally oxidized silicon substrate having an oxide layer on its surface, or a ceramic substrate such as alumina is used.

The magnetoresistive element of the present invention exhibiting a negative magnetoresistance change may be used alone, but in particular, it is used in combination with an element exhibiting a positive magnetoresistance change to provide a high-output magnetic field sensor. It is possible. That is, a high output can be obtained by performing a differential operation by combining an element exhibiting a positive magnetoresistance change and an element exhibiting a negative magnetoresistance change.
For example, as shown in FIG. 2, an element S1 exhibiting a negative magnetoresistance change and an element S2 exhibiting a positive magnetoresistance change are connected in series, driven at a constant voltage, and a differential operating magnetic field for detecting the midpoint potential is used. The sensor 60 is used. That is, as the element S1 exhibiting a negative magnetoresistance change, for example, the above-described magnetoresistance effect element 1 (FIG. 1) is used. As the element S2 exhibiting a positive magnetoresistance change, a so-called AMR film, GMR
A variety of known positive magnetoresistance changes, such as films, are used (these are already described by way of example in the section of the prior art). In addition, in FIG.
Reference numeral 1 denotes a voltmeter, and reference numeral 65 denotes a power supply.

When a magnetic field is applied to such a magnetic field sensor 60 (FIG. 2), the resistance of the element S1 decreases and the resistance of the element S2 increases, so that the midpoint potential greatly changes. Of course, the same effect can be obtained by a differential operation in which four elements are bridge-connected.

[0035]

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

(Example 1) A 7059 glass substrate (manufactured by Corning Incorporated) was used, and a first magnetic layer made of an iron (Fe) film was formed on this substrate with a metal mask (a 50 μm-thick phosphor bronze metal mask). The film was formed to a thickness of 200 ° while being patterned by using The length L ₁ of the first magnetic layer is 300
0 μm, and the line width W ₁ was 80 μm (aspect ratio L ₁
/ W ₁ is 37.5). In addition, the film formation of the element is performed using IBS (ion b
eam sputter) method.

Next, an aluminum film is formed in a circular shape (having a diameter of 2 m) on the portion where the first and second magnetic layers are expected to intersect vertically.
(circle of mφ). The thickness of the aluminum film was 50 °. After the formation of the aluminum film, the aluminum film was spontaneously oxidized at room temperature for 184 hours. Next, as shown in FIG. 1, a second magnetic layer made of a cobalt film is formed to a thickness of 200 ° while being patterned with a metal mask so as to be orthogonal to the first magnetic layer,
Example 1 A magnetoresistive element of Example 1 was manufactured.

The length L ₂ of the second magnetic layer is 3000
μm and a line width W ₂ of 80 μm (aspect ratio L ₂ /
W ₂ is 37.5). Note that the junction area of the first and second magnetic layers is given by the product of the stripe widths in order to be the intersection of the magnetic layers.

Example 2 In Example 1, the natural oxidation time of the aluminum film was changed from 184 hours to 84 hours. Otherwise, the procedure of Example 1 was followed to fabricate a magnetoresistive element of Example 2.

Example 3 In Example 2, the line widths W ₁ and W ₂ of the first and second upper and lower magnetic layers were changed from 80 μm to 200 μm, respectively. Otherwise, the procedure of Example 2 was followed to fabricate a magnetoresistance effect element of Example 3.

The resistance change in each of the magnetoresistive elements of Examples 1 to 3 manufactured as described above was determined by a DC four-terminal method. More specifically, measurement was performed in an in-plane DC magnetic field in a direction parallel to the first magnetic layer made of an iron film, and in an in-plane DC magnetic field in a direction parallel to the second magnetic layer made of a cobalt film. And the MR change rate (%) were determined.

The results are shown in Table 1 below. In addition, each MR curve was shown in FIGS.

[0043]

[Table 1] (Example 4) A differential operation magnetic field sensor as shown in FIG. 2 was manufactured. That is, the magnetoresistive element of the first embodiment is an element S1 exhibiting a negative change in resistance, and is provided with a spin-valve GMR multilayer film (film structure is Ta / NiFe / Cu / NiFe / FeM).
n / Ta) were connected in series as a positive resistance effect element S2 to obtain a differential operation magnetic field sensor. When a DC constant current power supply was connected to this sensor and the midpoint potential was measured, a high output was obtained with respect to changes in the external magnetic field.

[0044]

The effects of the present invention are clear from the above results. That is, the magnetoresistance effect element of the present invention has a laminated film structure in which the first magnetic layer and the second magnetic layer are joined via the non-magnetic layer, and applies a current perpendicular to the laminated film surface. An electric resistance when flowing is a magnetoresistive element that changes by application of an external magnetic field, and the magnetoresistive element is:
When the resistance value when an external magnetic field Hs is applied is Rs, and when the external magnetic field H (| Hs |> | H |) is R, the resistance value is expressed as (R-Rs) / Rs. Since the resistance change rate shows a negative value and the absolute value has a value of 5% or more, the operability between the element and the external magnetic field is excellent, and the practicability is also excellent. Further, by combining the element exhibiting the negative resistance change with the element exhibiting the positive resistance change, a high-output magnetic field sensor can be provided.

[Brief description of the drawings]

FIG. 1 is a plan view schematically showing the structure of a magnetoresistance effect element according to the present invention.

FIG. 2 is a plan view schematically showing a configuration of a magnetic field sensor of the present invention.

FIG. 3 is a diagram showing a rate of change in resistance with respect to a magnetic field of the magnetoresistive element of the present invention.

FIG. 4 is a diagram showing a resistance change rate with respect to a magnetic field of the magnetoresistive element of the present invention.

FIG. 5 is a diagram showing a resistance change rate with respect to a magnetic field of the magnetoresistive element of the present invention.

FIG. 6 is a diagram showing a resistance change rate with respect to a magnetic field of the magnetoresistance effect element of the present invention.

FIG. 7 is a diagram showing a resistance change rate with respect to a magnetic field of the magnetoresistive element of the present invention.

FIG. 8 is a diagram showing a rate of change in resistance with respect to a magnetic field of the magnetoresistive element of the present invention.

[Explanation of symbols]

 Reference Signs List 10 first magnetic layer 11 linear element part 20 second magnetic layer 21 linear element part 30 non-magnetic insulating layer 60 magnetic field sensor S1 element exhibiting a negative resistance change S2 positive Element showing resistance change of

Continuation of the front page (72) Inventor Daisuke Miyauchi 1-13-1, Nihonbashi, Chuo-ku, Tokyo TDC Corporation F term (reference) 2G017 AC08 AD54 AD63 AD65 BA05 BA09 5D034 BA02 BB02

Claims (6)

[Claims] 1. A laminated film structure in which a first magnetic layer and a second magnetic layer are joined via a non-magnetic layer, and an electric resistance when a current flows perpendicularly to the laminated film surface. Is a magnetoresistive element that changes when an external magnetic field is applied. The magnetoresistive element has a resistance value when an external magnetic field Hs is applied, Rs, and an external magnetic field H (| Hs |> | H
|) Is applied, the resistance value is R, and (R−R
s) / Rs has a negative resistance change rate,
And a magnetoresistive element having an absolute value of 5% or more. 2. The first magnetic layer and the second magnetic layer have a strip shape, and are joined in a cross shape via the non-magnetic layer. And when at least one of the second magnetic layers has a line width W and a length L of the strip-shaped element portion, the line width W is in the range of 80 to 200 μm,
The magnetoresistive element according to claim 1, wherein the aspect ratio (L / W) is 15 to 40. 3. A magnetic field sensor wherein an element exhibiting a negative resistance change and an element exhibiting a positive resistance change are combined and used in differential operation. 4. The magnetic field sensor according to claim 3, wherein the elements exhibiting a change in resistance are magnetoresistive elements. 5. An element exhibiting a negative resistance change has a laminated film structure in which a first magnetic layer and a second magnetic layer are joined via a non-magnetic layer. A magnetoresistive element whose electric resistance changes when an external magnetic field is applied when a current flows vertically. The magnetoresistive element has a resistance value Rs when an external magnetic field Hs is applied, an external magnetic field H ( Where | Hs |> | H
|) Is applied, the resistance value is R, and (R−R
s) / Rs has a negative resistance change rate,
The magnetic field sensor according to claim 3, wherein the absolute value has a value of 5% or more. 6. The first magnetic layer and the second magnetic layer have a strip shape, and are joined in a cross shape via the non-magnetic layer. And when at least one of the second magnetic layers has a line width W and a length L of the strip-shaped element portion, the line width W is in the range of 80 to 200 μm,
The magnetic field sensor according to claim 5, wherein the aspect ratio (L / W) is 15 to 40.