JPH0697533A - Magnetoresistance effect element - Google Patents

Abstract

PURPOSE:To obtain a magnetoresistance effect element wherein magnetoresistance change ratio is large, and saturation magnetic field and hysteresis are small, by alternately laminating magnetic layers of Co group or Ni group having magnetic anisolropy of cubic symmetry in a film surface and nonmagnetic layers. CONSTITUTION:A laminate 4 wherein magnetic layers 3 of Co group or Ni group having magnetic anisotropy of cubic symmetry in film surface and nonmagnetic layer 2 are alternately laminated is provided. When the magnetic layer 3 has magnetic anisotropy of cubic aymmetry in a film surface, two axes of easy magnetization exist in the film surface. By applying magnetic field to either axis direction, antiferromagnetic coupling is obtained via the nonmagnetic layer 2. Hence saturation magnetic field H2 becomes small as compared with the case of uniaxial magnetic anisotropy, and hysterisis also becomes small. That is, by providing the laminate 4 constituted of the magnetic films 3 and the nonmagnetic films 2, a magnetoresistance effect element wherein magnetoresistance change ratio is large and saturation magnetic field and hysteresis are small can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetoresistive element using an ultrathin film laminate, a so-called artificial lattice film.

[0002]

2. Description of the Related Art The magnetoresistive effect is an effect in which the resistance changes depending on the strength of an applied magnetic field. A magnetoresistive effect element utilizing such a magnetoresistive effect is widely used as a magnetic field sensor or a magnetic head because it has high sensitivity and can obtain a relatively large output.

Conventionally, permalloy alloy thin films have been widely used as magnetoresistive elements. However, the rate of change in magnetoresistance of the permalloy alloy thin film (ΔR / R: R is the electric resistance without a magnetic field, ΔR is R and the electric resistance R _S when a saturation magnetic field is applied.
Is about 2 to 3%, and there is a problem that the sensitivity to an applied magnetic field is not sufficient.

On the other hand, recently, as a new magnetoresistive effect element, a so-called artificial lattice film in which a magnetic layer and a non-magnetic layer having a thickness of several angstroms to several tens of angstroms are alternately laminated has attracted attention. Has been done. As such an artificial lattice film, (Fe / Cr) _n (Phys.Re
v.Lett.vol 61 (21) (1988) 2472), (Permalloy / C
u / Co / Cu) _n (J.Phys.SOC.Jap.vol 59 (9) (1990)
3061), (Co / Cu) _n (J.Mag.Mag.Mat.
94 (1991) L1, Phys. Rev. Lett. 66 (1991) 2152) are known.

Such an artificial lattice film has a large magnetoresistance change rate of several tens%, and from this point, it can be said that it is suitable as a magnetoresistance effect element. However, since the saturation magnetic field H _S is as large as several kOe to several tens of kOe with respect to the number Oe of permalloy, and there is hysteresis, it is sufficient when it is used for detecting a small magnetic field such as a magnetic sensor or a magnetic head. I can't get the sensitivity.

That is, in consideration of applications such as magnetic sensors and magnetic heads, it is required to reduce the saturation magnetic field to obtain a large magnetic resistance change with a small magnetic field and to have a small hysteresis.

[0007]

The present invention has been made in consideration of such a situation, and an object thereof is to provide a magnetoresistive effect element having a large rate of change in magnetoresistance, a small saturation magnetic field and a small hysteresis. To do.

[0008]

In order to solve the above problems, the present invention provides a Co-based or Ni-based magnetic layer having a magnetic anisotropy of cubic symmetry in the film plane, and a non-magnetic layer. There is provided a magnetoresistive effect element comprising a laminated body in which the layers are alternately laminated.

As described above, when the magnetic layer has cubic magnetic anisotropy in the film plane, there are two easy axes of magnetization in the film plane. If a magnetic field is applied in either direction, Since antiferromagnetic coupling is obtained through the non-magnetic layer, the saturation magnetic field H _S becomes smaller and hysteresis also becomes smaller than when uniaxial magnetic anisotropy is provided. That is, by providing such a laminated body of a magnetic film and a non-magnetic film, a magnetoresistive effect element having a large rate of change in magnetoresistance, a small saturation magnetic field and a small hysteresis can be obtained. When such an element is used as a magnetic head, a magnetic field sensor, or the like, an electrode may be formed on the laminated body so that the electrical resistance of the laminated body can be measured.

The magnetoresistive effect element according to the present invention comprises a laminated body in which magnetic layers and nonmagnetic layers are alternately laminated. For example, as shown in FIG. Laminate 4 formed by laminating a pair of the layer 2 and the magnetic layer 3 n times
To form.

The magnetic layer 3 has a magnetic anisotropy of cubic symmetry in the film plane, and is based on Co or Ni. These may be simple substances or alloys based on them, and in the case of alloys, other elements may be contained. For example, Co alone,
Co _1-x Fe _x, those mainly composed of Co, such as _{Co 1-xy Fe x Ni y} , Ni 1-x Fe x, Ni 1-xy Fe x C
which was mainly composed of Ni, such as o _y is preferable. In this case, Co _1-x Fe x and Ni _1-x Fe x In x <0.
5 is preferable, and x ≦ 0.3 is more preferable. Also, Co
Preferably _1-xy Fe _x Ni _y and Ni _1-xy Fe _x Co _y in x + y <0.5, x + y ≦ 0.3 is more preferred. A small amount of Fe in the magnetic layer based on Co or Ni contributes to the improvement of the magnetoresistance change rate, the reduction of the saturation magnetic field, etc., and exerts its effect from a small amount of about 1 atomic%. Note that such magnetic anisotropy is obtained by a desired crystal orientation, but this orientation does not have to be perfect and may be preferentially oriented.

The non-magnetic layer 2 is not particularly limited as long as it is made of a non-magnetic material capable of exhibiting a magnetoresistive effect when the laminated body 4 is formed together with the magnetic layer 3. Examples of the non-magnetic layer include Cu, Au, Ag and the like, which may be a simple substance thereof or an alloy containing them. The optimum non-magnetic layer 2 may be selected according to the type of the magnetic layer 3. When the magnetic layer 3 is mainly composed of Co, it is preferable to select one mainly composed of Cu, Ag, and Au, and Cu is most preferable.

The thickness of the magnetic layer 3 may be set appropriately,
Approximately 2 to 100 Å (hereinafter referred to as A) is preferable, and 20 to 40 A is further preferable. Since the MR value of the non-magnetic layer 2 oscillates depending on its thickness, it may be appropriately set near its peak, preferably near the second and third peaks, but it is preferably about 2 to 100 A, and more preferably 10 to 30 A. Is preferred.

The number n of laminated layers of the magnetic layer 3 and the non-magnetic layer 2 is 2 or more, generally about 5 to several tens, and it is better to consider the magnetoresistive effect. Is saturated, so it is preferable to appropriately set a value within the saturated range.

The substrate 1 supports the laminated body 4,
The material is not particularly limited. However, from the viewpoint of facilitating the introduction of cubic symmetric magnetic anisotropy, at least the surface portion preferably has a cubic crystal structure, and a single crystal body or one having a single crystal film on the surface is used. it can. As for the plane orientation, the film plane is preferably the (100) plane. In this case, it is possible to use a crystal whose surface is highly oriented with respect to the (100) plane, even if it is not a perfect single crystal. As the material of the substrate 1, for example, Mg
O, GaAs, Si, Co, Ni, LiF, CaF ₂ can be mentioned.

The layer directly formed on the substrate 1 may be either the magnetic layer 3 or the non-magnetic layer 2, but as shown in FIG.
Is preferably formed directly on the substrate 1. In this case, the magnetoresistive effect is larger than that in the case where the nonmagnetic layer 2 is directly formed on the substrate, and cubic anisotropy tends to be induced.

As shown in FIG. 2, a buffer layer 5 having an fcc structure such as permalloy may be interposed between the substrate 1 and the laminated body 4. The saturation magnetic field can be reduced by forming the buffer layer 5 from the magnetic layer after the buffer layer 5 is formed. Also, when forming the buffer layer 5 from the non-magnetic layer after forming the buffer layer 5, the buffer layer is not formed. The rate of change in magnetoresistance tends to be higher than in the case of forming a film from a nonmagnetic layer. The buffer layer 5 is effective from a thickness of about 3A. The upper limit of the thickness is not particularly limited due to the characteristics, but the upper limit is usually about several hundred A.

As a method for forming each layer, various methods such as an ultra-high vacuum sputtering method, a molecular beam epitaxy method, an RF mabnetron sputtering method, an ion beam sputtering method and a vapor deposition method, which have been conventionally used, can be adopted. You can

The magnetic layer and the nonmagnetic layer to be laminated do not have to be the same, and the composition and film thickness may be modulated along the laminating direction.

[0020]

Embodiments of the present invention will be described below.

(Embodiment 1) In this embodiment, a magnetic layer is made of Co _0.9 Fe _0.1 , a nonmagnetic layer is made of Cu, a buffer layer is made of permalloy, and an ion beam sputtering method is used to form a laminate. About.

First, a MgO (100) single crystal substrate was set in the chamber, the chamber was evacuated to 5 × 10 ^-7 Torr, and then Ar gas was introduced to 1 × 10 ^-4 Torr. Sputtering was performed under an acceleration condition of 700 V-30 mA. Co _0.9 Fe _0.1 alloy, Cu and permalloy (Ni ₈₀ Fe ₂₀ ) are prepared as targets.
On a MgO (100) single crystal substrate, 50 A of permalloy was first formed as a buffer layer, and then Co _0.9 Fe was formed.
_0.1 layer (film thickness 10A), then Cu layer (film thickness 10A) are alternately laminated in this order, and a pair of Co _0.9 Fe _0.1 layer and Cu layer is laminated 16 times (lamination number n = 16), It has a structure shown in FIG. 2 and has (Cu10A / Co _0.9 Fe _0.1 10
A) A magnetoresistive effect element having a structure of ₁₆ / permalloy 50A / MgO (100) was produced. In this embodiment, the magnetic layer is directly formed on the buffer layer.

FIG. 3 shows the torque curve of the element manufactured in this way. As is clear from FIG. 3, the torque curve of this element has 4-fold symmetry, which confirms that cubic magnetic anisotropy occurs. The result of measuring the magnetoresistive effect of this element is shown in FIG. Figure 4
Shows the magnetoresistive effect in the direction of easy axis,
From this figure, when applying a magnetic field in the direction of easy axis of magnetization,
It was confirmed that the magnetic resistance changed linearly, there was almost no hysteresis, and the saturation magnetic field was as small as 200 Oe. The rate of change in magnetic resistance was 38%. The saturation magnetic field was 7 kOe when the laminated body was formed on a SiO ₂ substrate or the like, and it was confirmed that the saturation magnetic field was significantly reduced by using the MgO (100) single crystal substrate.

Further, it can be seen from FIG. 4 that the resistance change is linear and there is almost no hysteresis, and the slope is very steep. Therefore, use of this region enables extremely sensitive magnetic field measurement.

For reference, FIG. 5 shows the magnetoresistive effect when the stacking order is reversed and the nonmagnetic layer is formed first without using the buffer layer. As is clear from this figure, the rate of change in magnetoresistance was 15.5%, which was small compared to 38% in the example. The saturation magnetic field was 2.3 kOe, which was a large value compared to 200 Oe of the example.

(Embodiment 2) In this embodiment, a magnetic layer is made of Co, a non-magnetic layer is made of Cu, a buffer layer is not used, and an ion beam sputtering method is used in the same manner as in Embodiment 1 to form a laminated body. An example of film formation will be shown.

Under the same film forming conditions as in Example 1, MgO (1
00) First, a Co layer (film thickness 10A) on a single crystal substrate,
Next, Cu layers (film thickness 10 A) are alternately laminated in this order,
A pair of a Co layer and a Cu layer is laminated 16 times (the number of laminated layers n = 1)
6) and has the structure shown in FIG.
10A) A magnetoresistive element having a structure of ₁₆ / MgO (100) was produced.

FIG. 6 shows a torque curve of the element manufactured in this way. From this figure, it can be seen that the magnetic layer has cubic symmetric magnetic anisotropy. Moreover, the result of having measured the magnetoresistive effect of this element is shown in FIG. FIG. 7 shows the magnetoresistive effect in the direction of the easy axis of magnetization. From this figure, it was confirmed that the saturation magnetic field H _S was extremely small at 180 Oe and that there was almost no hysteresis. The saturation magnetic field was 6.5 kOe when the laminated body was formed on a SiO ₂ substrate or the like, and it was confirmed that the saturation magnetic field was significantly reduced by using the MgO (100) single crystal substrate. The rate of change in magnetic resistance was 31%.

For reference, FIG. 8 shows the magnetoresistive effect when the stacking order is reversed and the nonmagnetic layer is formed first. As is clear from this figure, the rate of change in magnetoresistance was 12%, which was smaller than 31% of the example. The saturation magnetic field was a large value of 2.0 kOe.

Example 3 In this example, a laminated body was formed in the same manner as in Example 2 except that the magnetic layer was Co _0.75 Fe _0.25 . That is, MgO (10
0) First, a Co _0.75 Fe _0.25 layer (film thickness 10 A) and then a Cu layer (film thickness 10 A) are alternately laminated on a single crystal substrate, and a pair of Co layer and Cu layer is laminated 16 times. (The number of stacked layers n = 16), and the structure shown in FIG.
A magnetoresistive element having a structure of A / Co _0.75 Fe _0.25 10A) ₁₆ / MgO (100) was produced.

FIG. 9 shows a torque curve of the element manufactured in this way. From this figure, it can be seen that the magnetic layer has cubic symmetric magnetic anisotropy. The results of measuring the magnetoresistive effect of this element are shown in FIG. FIG. 10 shows the magnetoresistive effect in the direction of easy axis of magnetization. From this figure, it was confirmed that the saturation magnetic field H _S was as small as 150 Oe and that there was almost no hysteresis. The rate of change in magnetic resistance was 23.1%. When the above laminated body is formed on a SiO ₂ substrate or the like, the saturation magnetic field is 7 k.
It was Oe, and it was confirmed that the saturation magnetic field was significantly reduced by using the MgO (100) single crystal substrate.

For reference, FIG. 11 shows the magnetoresistive effect when the stacking order is reversed and the nonmagnetic layer is formed first. As is clear from this figure, the magnetoresistance change rate was as small as 11% and the saturation magnetic field was as large as 2.0 kOe.

(Embodiment 4) In this embodiment, an example in which a magnetic layer is made of Co _0.8 Fe _0.1 Ni _0.1 and a non-magnetic layer is made of Cu and a laminated body is formed in the same manner as in the embodiment 2 will be described.

Under the same film forming conditions as in Example 2, MgO (1
00) On a single crystal substrate, first Co _0.8 Fe _0.1 Ni
_0.1 layer (film thickness 15A) and then Cu layer (film thickness 10A) are alternately laminated in this order, and a pair of Co _0.8 Fe _0.1 Ni _0.1 layer and Cu layer is laminated 16 times (the number of laminated layers n = 16). hand,
It has the structure shown in FIG. 1 and has (Cu10A / Co _0.8 Fe
A magnetoresistive effect element having a structure of _0.1 Ni _0.1 15 A) ₁₆ / MgO (100) was produced.

FIG. 12 shows the torque curve of the element manufactured in this way. From this figure, it can be seen that the magnetic layer has cubic symmetric magnetic anisotropy. The result of measuring the magnetoresistive effect of this element is shown in FIG. FIG. 13 shows the magnetoresistive effect in the direction of the easy axis of magnetization. From this figure, the saturation magnetic field H _S is as small as 170 Oe,
It was confirmed that there was almost no hysteresis. Also,
The rate of change in magnetic resistance was 18%. When the above laminated body is formed on a SiO ₂ substrate or the like, the saturation magnetic field is 4 kOe.
It was confirmed that the saturation magnetic field was significantly reduced by using the MgO (100) single crystal substrate.

For reference, FIG. 14 shows the magnetoresistive effect when the stacking order is reversed and the nonmagnetic layer is formed first. As is clear from this figure, the magnetoresistance change rate was as small as 9.5% and the saturation magnetic field was as large as 1.8 kOe.

(Embodiment 5) In this embodiment, a Si (100) single crystal is used as a substrate and Co _0.9 is used as a magnetic layer.
Fe _0.1 , non-magnetic layer Cu, buffer layer Cu
And as Permalloy, an example of forming a laminated body by using an ion beam sputtering method is shown.

On a Si (100) single crystal substrate, first C
50 u of u and then 50 A of permalloy were formed to form a buffer layer having a two-layer structure. Then, a Cu layer (film thickness 10A) and then a Co _0.9 Fe _0.1 layer (film thickness 10A) are alternately laminated on the buffer layer in this order.
After stacking five times (stacking number n = 15), (Cu10A / Co
_0.9 Fe _0.1 10A) ₁₅ / Permalloy 50A / Cu50
A magnetoresistive effect element having a structure of A / Si (100) was produced.

FIG. 15 shows the torque curve of the element manufactured in this way. From this figure, it can be seen that the magnetic layer has cubic symmetric magnetic anisotropy. 16 shows the result of measuring the magnetoresistive effect of this element. FIG. 16 shows the magnetoresistive effect in the easy magnetization axis direction. From this figure, when a magnetic field is applied in the easy magnetization axis direction, the magnetic resistance changes linearly and the magnetoresistive effect is 36%. Large, almost no hysteresis, saturated magnetic field of 200
It was confirmed to be remarkably small as Oe.

[0040]

According to the present invention, there is provided a magnetoresistive element having a large magnetoresistance change rate, a small saturation magnetic field and a small hysteresis. The magnetoresistive effect element is extremely effective for a high-sensitivity magnetic head for high density recording, a magnetic field sensor, and the like.

[Brief description of drawings]

FIG. 1 is a sectional view showing a magnetoresistive effect element according to one embodiment of the present invention.

FIG. 2 is a sectional view showing a magnetoresistive effect element according to another embodiment of the present invention.

FIG. 3 is a diagram showing a torque curve of the device of Example 1.

FIG. 4 is a diagram showing a magnetoresistive curve of the element of Example 1;

FIG. 5 is a diagram showing a magnetoresistive curve of an element in which the stacking order is reversed from that in Example 1.

FIG. 6 is a diagram showing a torque curve of the element of Example 2;

FIG. 7 is a diagram showing a magnetoresistive curve of the element of Example 2;

FIG. 8 is a diagram showing a magnetoresistive curve of an element in which the stacking order is reversed from that of the second embodiment.

FIG. 9 is a diagram showing a torque curve of the element of Example 3;

FIG. 10 is a diagram showing a magnetoresistance curve of the element of Example 3;

FIG. 11 is a diagram showing a magnetoresistive curve of an element in which the stacking order is reversed from that in Example 3;

FIG. 12 is a diagram showing a torque curve of the element of Example 4;

FIG. 13 is a diagram showing a magnetoresistance curve of the element of Example 4;

FIG. 14 is a diagram showing a magnetoresistive curve of an element in which the stacking order is reversed from that in Example 4.

FIG. 15 is a diagram showing a torque curve of the element of Example 5;

16 is a diagram showing a magnetoresistance curve of the element of Example 5. FIG.

[Explanation of symbols]

1 ... Substrate, 2 ... Non-magnetic layer, 3 ... Magnetic layer, 4 ... Laminated body, 5 ... Buffer layer.

Claims (1)

[Claims] 1. A magnetoresistive device comprising a laminated body in which a Co-based or Ni-based magnetic layer having a cubic magnetic anisotropy in the film plane and a non-magnetic layer are alternately laminated. Effect element.