KR100905737B1 - Spin-valve magnetoresistive element with perpendicular magnetic anisotropy - Google Patents

Abstract

The present invention relates to a spin valve magnetoresistive element having perpendicular magnetic anisotropy, wherein two or more "Pd layers / ferromagnetic layers" or "ferromagnetic layers" which form a thin Pd layer and repeatedly form a ferromagnetic layer vertically magnetized on the plane thereof. / Pd layer "by forming a free layer and a fixed layer, the overall thickness is not only thin, but also has a high magnetoresistance ratio and low coercive force on the free layer, it is possible to detect a small change in the external magnetic field various biosensors When used as a nonvolatile memory device, it is possible to significantly reduce power consumption during writing.

Vertical magnetic anisotropy, spin valve, magnetoresistive element

Description

Spin valve magnetoresistive element with perpendicular magnetic anisotropy {SPIN-VALVE MAGNETORESISTIVE ELEMENT WITH PERPENDICULAR MAGNETIC ANISOTROPY}

The present invention relates to a spin valve magnetoresistive element having a free layer / nonmagnetic layer / fixed layer / antiferromagnetic layer structure having vertical magnetization, and having a perpendicular magnetic anisotropy having a high MR ratio and a small coercive force of the free layer. It relates to a spin valve magnetoresistive element.

The spin valve magnetoresistive element is formed of a free layer (ferromagnetic layer) / nonmagnetic layer / fixed layer (ferromagnetic layer) / antiferromagnetic layer structure, and if the nonmagnetic layer is a conductive material (for example, Cu, etc.) If the nonmagnetic layer is a non-conductive material (eg Al ₂ O _3, etc.), it is classified as TMR (Tunneling Magneto-Resistance).

Such a spin valve magnetoresistive element has conductive electrons (for GMR spin valves) or tunneling electrons (TMR) depending on the difference in the spin direction (magnetization direction) of the free layer (ferromagnetic layer) and the fixed layer (ferromagnetic layer) with a nonmagnetic layer interposed therebetween. Additional scattering of the spin valve) results in a change in resistance. That is, the ferromagnetic spin directions of the free layer and the pinned layer are the same, and thus the resistance is small, and the difference is relatively large when the ferromagnetic spin directions are the same.

Spin valve magnetoresistive elements used as memory devices are superior to EEPROM, FRAM, and flash memory in terms of data access time, data retention (year), and read / write endurance (cycles). It combines the advantages of conventional RAM and ROM memory devices, such as nonvolatile characteristics that free and turn off the stored data.

However, in order to apply the spin valve magnetoresistive element as a memory element or a magnetic head, it is necessary to form strong uniaxial magnetic anisotropy in the material. Until now, the direction of magnetization is uniaxial in the in-plane direction parallel to the specimen plane It has been mainly used to induce magnetic anisotropy (hereinafter, referred to as 'cotton box anisotropy').

As in the related art, in order to induce surface paramagnetic anisotropy, an external magnetic field must be applied during material deposition or a post-heat treatment must be performed in an external magnetic field after deposition, so that the deposition parameters increase during the deposition of the material and additional deposition of an external magnetic field source. It is disadvantageous in that the apparatus becomes complicated and the number of processes increases.

In addition, when the multilayer thin film is laminated on the substrate in the conventional manner, as the lamination proceeds, the entire structure of the thin film becomes hard to form uniaxial magnetic anisotropy. In order to solve this problem, there is an example of using a tilted substrate (Korean Patent No. 253743). However, when the tilted substrate is used, the price is high and it is difficult to apply industrially.

Furthermore, when the spin valve magnetoresistive element having a surface paramagnetic anisotropy is patterned to a size of less than a micron, the magnetization deformation and the fine magnetic domain are caused by the vortex magnetization at the edge of the pattern element. Due to this, a flower structure is generated, which increases coercivity (Hc) of the thin film and causes distortion of magnetization, and has a certain limit in shrinking the device.

To overcome these problems, spin valve magnetoresistive elements having uniaxial magnetic anisotropy (hereinafter referred to as 'vertical magnetic anisotropy') in which the direction of magnetization is perpendicular to the specimen surface have been studied.

However, according to the recent research results of F. Garica et al., In order to have perpendicular magnetic anisotropy in Pt / Co multilayer thin film, Pt should have a thickness of about 1 nm ~ 2 nm. When the conductive electrons or tunneling electrons to flow to the nonmagnetic layer have a low Pt layer due to the leakage current flowing into the Pt layer instead of the nonmagnetic layer (shunting effect) has a low magnetoresistance ratio.

In addition, the generation of a large switching field of the free layer due to strong perpendicular magnetic anisotropy increases the coercive force of the free layer, which is a disadvantage in application to the device.

In particular, in order to use the spin valve magnetoresistive element in a biosensor such as a living body pulse sensor, the magnetization direction of the free layer should be able to be changed even with a slight external magnetic field change. At the same time, it is important to keep the size small, and there is no research and development on it.

The present invention has a strong perpendicular magnetic anisotropy, high coercive force, large exchange bias using a "Pd layer / ferromagnetic layer" or "ferromagnetic layer / Pd layer" multilayer thin film to solve the problems of the prior art By constructing the spin valve with a fixed layer and a free layer with low coercivity, the overall thickness is not only thin, but also has a high magnetoresistance ratio and has a low coercive force in the free layer, so that it is possible to detect or record a small external magnetic field change. It is an object of the present invention to provide a spin valve magnetoresistive element having perpendicular magnetic anisotropy.

In order to achieve the above object, the spin valve magnetoresistive element having a perpendicular magnetic anisotropy of the present invention comprises a free layer / nonmagnetic layer / fixed layer / antiferromagnetic layer, wherein the free layer and the fixed layer Is a “Pd layer / first ferromagnetic layer” or “first ferromagnetic layer / Pd layer” repeatedly deposited two or more times N times, wherein the first ferromagnetic layer is magnetized perpendicularly to the surface of the Pd layer, and The free layer is formed between a buffer layer formed on a predetermined substrate and the nonmagnetic layer, and N "Pd layers / first ferromagnetic layers" forming the free layer are formed on the buffer layer, and the first ferromagnetic layer and the A Pd layer and a vertically magnetized second ferromagnetic layer are sequentially deposited between the nonmagnetic layers, and the nonmagnetic layer is deposited on the second ferromagnetic layer, and the pinned layer forms the nonmagnetic layer and the pinned layer. A "Pd layer / a first ferromagnetic layer" is the perpendicular second ferromagnetic layer is magnetized in the further deposited between characterized in that formed or,
In a spin valve magnetoresistive element including a free layer, a nonmagnetic layer, a fixed layer, and an antiferromagnetic layer, the free layer and the fixed layer may each be a "Pd layer / first ferromagnetic layer" or a "first ferromagnetic layer / Pd layer". The first ferromagnetic layer is magnetized perpendicularly to the surface of the Pd layer, and the antiferromagnetic layer is formed between a buffer layer formed on a predetermined substrate and the pinned layer. N is formed on the anti-ferromagnetic layer to form the N "first ferromagnetic layer / Pd layer" to form the pinned layer, a second ferromagnetic layer magnetized perpendicularly to the Pd layer is further formed, the nonmagnetic layer is The ferromagnetic layer is deposited on the second ferromagnetic layer, and the free layer includes a second ferromagnetic layer and a Pd layer vertically magnetized between the nonmagnetic layer and the N “first ferromagnetic layers / Pd layers” constituting the free layer. Characterized in that formed by further deposition The.

In the spin valve magnetoresistive element structure, the free layer and the two or more "Pd layer / ferromagnetic layer" or "ferromagnetic layer / Pd layer" forming a thin Pd layer and repeatedly formed a magnetized ferromagnetic layer on its plane By forming the pinned layer, the overall thickness is not only thin, but also has a high magnetoresistance ratio, and at the same time, the low coercive force is provided to the free layer.

As a result, when the spin valve magnetoresistive element according to the present invention is used in a biosensor, a change in a minute external magnetic field can be sensed, and when used as a nonvolatile memory element, power consumption during writing can be reduced.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention.

[First Example ]

In the spin valve magnetoresistive element including a free layer, a nonmagnetic layer, a fixed layer, and an antiferromagnetic layer, as shown in FIG. 1, the free layer and the fixed layer each have a "Pd" with a nonmagnetic layer interposed therebetween. Layer / first ferromagnetic layer " is repeatedly deposited two or more times N times, and the first ferromagnetic layer is magnetized perpendicularly to the surface of the Pd layer.

Here, the free layer is formed between a buffer layer formed on a predetermined substrate and the nonmagnetic layer, and N "Pd layers / first ferromagnetic layers" forming the free layer are formed on the buffer layer, and the first ferromagnetic A Pd layer and a vertically magnetized second ferromagnetic layer are sequentially deposited between the layer and the nonmagnetic layer, the nonmagnetic layer is deposited over the second ferromagnetic layer of the free layer, and the pinned layer is the nonmagnetic layer. And a second ferromagnetic layer magnetized perpendicularly between N "Pd layers / first ferromagnetic layers" forming the pinned layer may be further formed.

In addition, the Pd layer is preferably deposited to a thickness of 0.5 ~ 0.7 nm. However, since the Pd layer is deposited in order to induce vertical magnetization of the first ferromagnetic layer or the second ferromagnetic layer, the Pd layer is not limited thereto as long as it can vertically magnetize the first ferromagnetic layer or the second ferromagnetic layer. . However, when the thickness of the Pd layer becomes too thick (about 4 times or more) than the thickness of the first ferromagnetic layer or the second ferromagnetic layer, the coercivity increases due to strong vertical magnetization, making it difficult to drop the coercive force of the free layer. In addition, most of the conduction electrons or tunneling electrons that need to enter the nonmagnetic layer flow to the surface of the thick Pd layer, which causes a large leakage current.

In addition, it is preferable that the first ferromagnetic layer is a Co layer, and the second ferromagnetic layer is a Co layer or a CoFe alloy layer.

In this case, when the second ferromagnetic layer is a CoFe alloy layer, the weight ratio of Co and Fe is preferably 5: 5 to 9: 1, but more preferably 9: 1.

In addition, the substrate may be any one selected from Si, SiO ₂ and glass, and the buffer layer may be a Pd layer or a Ta layer, but the latter is more preferable in consideration of a squareness in which magnetic field sensitivity is known. Do.

On the other hand, the nonmagnetic layer may be a GMR spin valve magnetoresistive element structure as the Cu layer as the conductive layer, or may be a TMR spin valve magnetoresistive element structure as the Al ₂ O ₃ layer as the nonconductive layer.

More specifically, the free layer is [Pd (0.6) / Co (0.16)] ₂ /Pd(0.6)/second ferromagnetic, the nonmagnetic layer is Cu (2.25), and the pinned layer is a second ferromagnetic layer / [ Pd (0.6) / Co (0.23)] ₂ .

Here, the second ferromagnetic layer is any one selected from Co (0.3 ~ 0.7), Co ₅ Fe ₅ (0.5 ~ 0.8) and Co ₉ Fe ₁ (0.3 ~ 0.7), the buffer layer is Ta (1.8 ~ 20) The antiferromagnetic layer is preferably made of FeMn (10-11).

At this time, the numerical value in said () shows the thickness of each layer in nm unit (it is the same below).

In particular, the thickness of the second ferromagnetic layer is preferably made larger in the fixed layer than in the free layer in order to reduce the coercive force in the free layer and the exchange force in the fixed layer. For example, when the second ferromagnetic layer is 0.3 to 0.5 nm of Co in the free layer, the Co thickness of the fixed layer is preferably 0.5 to 0.7 nm, and the second ferromagnetic layer is 0.5 to Co ₅ Fe ₅ in the free layer. In the case of 0.65 nm, the thickness of Co ₅ Fe ₅ of the fixed layer is preferably 0.65 to 0.8 nm, and in the free layer, when the second ferromagnetic layer is 0.3 to 0.7 nm of Co ₉ Fe ₁ in the free layer, Co ₅ Fe ₅ is fixed. _{5 The} thickness is preferably 0.7 nm.

[Second Example ]

In the first embodiment, the free layer and the pinned layer are linearly symmetrical with respect to the nonmagnetic layer. As shown in FIG. 2, the free layer and the pinned layer are each formed of a "first ferromagnetic layer." / Pd layer "is repeatedly deposited two or more times N times, wherein the first ferromagnetic layer is a magnetized structure perpendicular to the surface of the Pd layer.

More specifically, the antiferromagnetic layer is formed between a buffer layer formed on a predetermined substrate and the pinned layer, and the pinned layer is formed of N “first ferromagnetic layers / Pd layers” forming the pinned layer on the antiferromagnetic layer. And a second ferromagnetic layer magnetized perpendicularly over the Pd layer, the nonmagnetic layer is deposited over the second ferromagnetic layer, and the free layer forms the free layer with the nonmagnetic layer. A second ferromagnetic layer and a Pd layer magnetized perpendicularly between the " first ferromagnetic layer / Pd layer " may be sequentially formed by further deposition.

In addition, since description of each layer is the same as that of the said 1st Example, repeated description is abbreviate | omitted. However, the free layer and the layer structure for each of the second ferromagnetic layer for the fixing layer _{/Pd(0.6)/[Co(0.16)/Pd(0.6)] 2, [Co (} 0.23) / Pd (0.6)] 2 It must be a second ferromagnetic layer.

Next, a more specific embodiment for catching the structural conditions of the spin valve magnetoresistive element having perpendicular magnetic anisotropy according to the first and second embodiments will be described in detail.

<Specification of repetitive layer>

In the first embodiment, the repeating layer repeatedly deposited N times on the free layer and the pinned layer is formed by stacking two layers of “Co (0.16) / Pd (0.6)” and “Co (0.23) / Pd (0.6)”, respectively. (In the second embodiment, the deposition order is reversed), which specifies the Pd layer to be 0.6 nm so that the total thickness is small while allowing the Co layer to be perpendicularly magnetized in contact with the Pd layer. In consideration of the further deposition of the Pd layer, the thickness of the Co layer in contact with the Pd layer in the free layer was slightly smaller than that of the fixed layer.

In addition, the repetitive layer is provided in two layers, respectively, on the free layer and the fixed layer, based on the following reason.

When the repetitive layer was formed as a single layer on the free layer, the free layer was affected by the minute leakage magnetization of the fixed layer, and thus the magneto-resistance ratio was reduced. There was this growing problem.

In addition, when the repeating layer was made of two layers in the fixed layer, the antiferromagnetic material, the exchange bias and the magnetoresistance ratio were the largest.

<Determination of the buffer layer>

Next, to determine the buffer layer used in the above embodiment, as shown in FIG. 3, the buffer layer considering the thickness of the repetitive layer of the free layer and the pinned layer on the glass substrate / [Pd (0.6) / Co (0.39)] ₅ / Ta ( 1.9) The Extraordinary Hall Effect was measured in the structure (right Ta (1.9) was selected as a protective layer) using Ta (2) and Pd (2), respectively.

As can be seen in Figure 4 it can be seen that Ta (2) is better in angular ratio than Pd (2). Therefore, in the above embodiment, the buffer layer is determined to be a Ta layer, and in order to determine the thickness of the Ta layer, the exchange force and the coercive force must be large in the fixed layer. Thus, in the structure as shown in FIG. As a variable, the exchange force (Hex) and the coercive force (Hc) of the structure Ta (t) / [Pd (0.6) / Co (0.39)] ₅ /Ta(1.9) were measured. Got it.

Therefore, the thickness of the Ta layer, which is the buffer layer, was determined to be 1.9 nm in which both the exchange force and the coercive force were large in the fixed layer.

Determination of Antiferromagnetic Layer

In the above embodiment, the antiferromagnetic layer is a layer for holding the fixed layer to maintain a constant magnetization direction, and thus, the exchange layer and the coercive force in the fixed layer should be determined under a large condition. Therefore, in the structure as shown in FIG. 5, Ta (1.9) / [Pd (0.6) / Co (0.39)] ₅ /FeMn(t)/Ta(1.9) with the thickness t of the FeMn layer as the antiferromagnetic layer as a variable. As a result of measuring the exchange force (Hex) and the coercive force (Hc) for the structure), a result as shown in FIG. 7 was obtained.

Based on this, the thickness of the FeMn layer, which is an antiferromagnetic layer, was determined to be 10 nm or 10.5 nm in which both the exchange and coercive forces are large in the fixed layer.

<Determination of nonmagnetic layer>

In the above embodiment, the nonmagnetic layer should have an appropriate thickness of the nonmagnetic material because it should prevent the leakage magnetization by the pinned layer from affecting the free layer as much as possible.

Accordingly, the nonmagnetic layer was made of Cu and the thickness thereof was determined to be 2.25 nm under the condition that the exchange force of the fixed layer was increased and the magnetoresistance ratio was increased.

<Determination of Second Ferromagnetic Layer>

In the above embodiment, the material and thickness of the second ferromagnetic layer should be determined such that the coercive force becomes small in the free layer and the exchange force becomes large in the fixed layer. For this purpose, in the magnetic vertical anisotropic spin valve structure as shown in FIG. The ferromagnetic layer is any one of Co (0.7), Co ₉ Fe ₁ (0.7), Co ₅ Fe ₅ (0.76), and NiFe (1.1), and the thickness of the second ferromagnetic layer (t) of the free layer is defined as Ta ( 1.9) / [Pd (0.6) / Co (0.16)] ₂ /Pd(0.6)/second ferromagnetic layer (t) of free layer / Cu (2.25) / second ferromagnetic layer of fixed layer / [Pd (0.6) / Co (0.23)] ₂ /FeMn(10.5)/Ta(1.9) structure measured the coercive force and the magnetoresistance ratio in the free layer.

Therefore, the material of the second ferromagnetic layer is Co, Co ₉ Fe ₁ And Co ₅ Fe ₅ The thickness of the fixed layer should be larger than that of the free layer so that the coercivity becomes smaller in the free layer and the exchange force is increased in the fixed layer. 9 and 10, which are results of measuring magnetoresistance ratios obtained in the same structure, were used.

As a result, when the second ferromagnetic layer is 0.3 to 0.5 nm of Co in the free layer, the Co thickness of the fixed layer is preferably 0.5 to 0.7 nm, and the second ferromagnetic layer is 0.5 to Co ₅ Fe ₅ in the free layer. to 0.65 If in nm, Co ₅ Fe ₅ thickness of the fixed bed is preferred that a 0.65 - 0.8 nm, and, when the second ferromagnetic layers in the free layer in the 0.3 - 0.7 nm as Co ₉ Fe ₁ has a fixed-bed Co ₅ It was found that the Fe ₅ thickness is preferably 0.7 nm.

As described above, preferred embodiments of the present invention have been described in detail, but the present invention is not limited thereto, and various modifications can be made by those skilled in the art. Accordingly, descriptions of various embodiments that can be modified under the technical spirit of the present invention will be omitted herein.

1 is a structural diagram showing an embodiment of a structure of a spin valve magnetoresistive element having perpendicular magnetic anisotropy according to the present invention.

2 is a structural diagram showing another embodiment of the structure of a spin valve magnetoresistive element having perpendicular magnetic anisotropy according to the present invention.

3 is a structural diagram of a free layer center for determining a buffer layer in the structure of FIG. 1.

FIG. 4 illustrates the Extraordinary Hall Effect for the buffer layer / [Pd (0.6) / Co (0.39)] ₅ /Ta(1.9) structure using the buffer layers Ta (2) and Pd (2) in FIG. The result is also.

5 is a structural diagram of a fixed layer center for determining the thickness of the buffer layer and the antiferromagnetic layer in the structure of FIG.

FIG. 6 shows the exchange force for the structure Ta (t) / [Pd (0.6) / Co (0.39)] ₅ /Ta(1.9) with the thickness t of the buffer layer Ta in the structure of FIG. Hex) and coercive force (Hc) are measured.

FIG. 7 shows Ta (1.9) / [Pd (0.6) / Co (0.39)] ₅ /FeMn(t)/Ta(1.9) with the thickness t of the FeMn layer as the antiferromagnetic layer in the structure of FIG. This is a result of measuring exchange force (Hex) and coercive force (Hc) for the structure.

FIG. 8 shows the second ferromagnetic layer of the pinned layer as one of Co (0.7), Co ₉ Fe ₁ (0.7), Co ₅ Fe ₅ (0.76), and NiFe (1.1) in the structure of FIG. 1. The second ferromagnetic layer (t) / Cu (2.25) / fixed layer of Ta (1.9) / [Pd (0.6) / Co (0.16)] ₂ /Pd(0.6)/free layer with the layer thickness t as a variable Fig. ₂ shows the results of measuring the coercive force and magnetoresistance ratio in the free layer with respect to the second ferromagnetic layer / [Pd (0.6) / Co (0.23)] ₂ /FeMn(10.5)/Ta(1.9) structure.

9 and 10 are the result of measuring the magnetoresistance ratio in the structure as shown in FIG.

Claims (10)

delete In the spin valve magnetoresistive element including a free layer, a nonmagnetic layer, a fixed layer, and an antiferromagnetic layer, The free layer and the pinned layer are each deposited "Pd layer / first ferromagnetic layer" or "first ferromagnetic layer / Pd layer" two or more times N times, the first ferromagnetic layer is perpendicular to the surface of the Pd layer Magnetized to The free layer is formed between a buffer layer formed on a predetermined substrate and the nonmagnetic layer, and N “Pd layers / first ferromagnetic layers” forming the free layer are formed on the buffer layer, and the first ferromagnetic layer and A Pd layer and a vertically magnetized second ferromagnetic layer are sequentially deposited between the nonmagnetic layers, The nonmagnetic layer is deposited on the second ferromagnetic layer, The pinned layer is a spin valve magnetoresistance having perpendicular magnetic anisotropy, wherein a second ferromagnetic layer magnetized perpendicularly between the nonmagnetic layer and the N "Pd layer / first ferromagnetic layer" forming the pinned layer is further deposited. device. In the spin valve magnetoresistive element including a free layer, a nonmagnetic layer, a fixed layer, and an antiferromagnetic layer, The free layer and the pinned layer are each deposited "Pd layer / first ferromagnetic layer" or "first ferromagnetic layer / Pd layer" two or more times N times, the first ferromagnetic layer is perpendicular to the surface of the Pd layer Magnetized to The antiferromagnetic layer is formed between the buffer layer and the pinned layer formed on a predetermined substrate, The pinned layer is formed by forming N “first ferromagnetic layers / Pd layers” forming the pinned layer on the antiferromagnetic layer, and further depositing a second ferromagnetic layer magnetized vertically on the Pd layer. The nonmagnetic layer is deposited on the second ferromagnetic layer, The free layer is a vertical magnetic layer formed by sequentially depositing a second ferromagnetic layer and a Pd layer magnetized vertically between the nonmagnetic layer and the N "first ferromagnetic layer / Pd layer" constituting the free layer Spin valve magnetoresistive element having anisotropy. The method of claim 2 or 3, The Pd layer is a spin valve magnetoresistance device having perpendicular magnetic anisotropy, characterized in that the thickness of 0.5 ~ 0.7 nm. The method of claim 4, wherein The first ferromagnetic layer is a Co layer, the second ferromagnetic layer is a spin valve magnetoresistance device having perpendicular magnetic anisotropy, characterized in that the Co layer or CoFe alloy layer. The method of claim 5, wherein The CoFe alloy layer of the second ferromagnetic layer is a spin valve magnetoresistance device having perpendicular magnetic anisotropy, characterized in that the weight ratio of Co and Fe is 5: 5 to 9: 1. The method of claim 6, The substrate is any one selected from Si, SiO ₂ and glass, The buffer layer is a spin valve magnetoresistive element having perpendicular magnetic anisotropy, characterized in that the Ta layer. The method of claim 7, wherein The nonmagnetic layer is a spin valve magnetoresistance device having perpendicular magnetic anisotropy, characterized in that the Cu layer or Al ₂ O ₃ layer. The method of claim 8, The free layer is [Pd (0.6) / Co (0.16)] ₂ /Pd(0.6)/second ferromagnetic layer or second ferromagnetic layer / Pd (0.6) / [Co (0.16) / Pd (0.6)] ₂ , The nonmagnetic layer is Cu (2.25), The pinned layer is a second ferromagnetic layer / [Pd (0.6) / Co (0.23)] ₂ or [Co (0.23) / Pd (0.6)] ₂ / second ferromagnetic layer, The numerical value in () is a spin valve magnetoresistive element having perpendicular magnetic anisotropy, characterized in that the thickness of each layer is expressed in nm units. The method of claim 9, The second ferromagnetic layer is any one selected from Co (0.3 ~ 0.7), Co ₅ Fe ₅ (0.5 ~ 0.8) and Co ₉ Fe ₁ (0.3 ~ 0.7), the thickness of the fixed layer is the free layer Larger than the thickness that they make up, The buffer layer is Ta (1.8 ~ 20), The antiferromagnetic layer is FeMn (10-11), The numerical value in () is a spin valve magnetoresistive element having perpendicular magnetic anisotropy, characterized in that the thickness of each layer is expressed in nm units.

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