Patent ID: 12217775

DETAILED DESCRIPTION OF THE INVENTION

The disclosure will be appropriately described below in detail with reference to the drawings. In the drawings used in the following description, in order to facilitate understanding features of the disclosure, feature parts are enlarged for convenience of illustration in some cases, and size ratios and the like between components may be different from those of actual components. Materials, sizes, and the like exemplified in the following description are examples not limiting the disclosure, and they can be appropriately changed and implemented within a range not changing the scope and spirit of the invention.

First Embodiment

FIG.1is a cross-sectional view of a magnetoresistance effect element according to a first embodiment of the disclosure.FIG.1is a cross-sectional view of a magnetoresistance effect element101cut in a lamination direction of respective layers of the magnetoresistance effect element101. The magnetoresistance effect element101is a laminate in which an underlayer20, a first ferromagnetic layer30, a first NiAl layer40, a non-magnetic layer50, a second NiAl layer60, a second ferromagnetic layer70, and a cap layer80are laminated in this order on a substrate10. The non-magnetic layer50is positioned between the first ferromagnetic layer30and the second ferromagnetic layer70. The first NiAl layer40is positioned between the first ferromagnetic layer30and the non-magnetic layer50, and the second NiAl layer60is positioned between the non-magnetic layer50and the second ferromagnetic layer70.

(Substrate)

The substrate10is a part serving as a base of the magnetoresistance effect element101. A material having excellent flatness is preferably used for the substrate10. The substrate10includes, for example, a metal oxide single crystal, a silicon single crystal, a silicon single crystal with a thermal oxide film, a sapphire single crystal, a ceramic, quartz, and glass. The material contained in the substrate10is not particularly limited as long as it has appropriate mechanical strength and is suitable for a heat treatment and microfabrication process. Examples of metal oxide single crystals include a MgO single crystal. For example, an epitaxial growth film can be easily formed on a substrate containing a MgO single crystal using a sputtering method. A magnetoresistance effect element using this epitaxial growth film exhibits high magnetic resistance characteristics. The type of the substrate10differs depending on a desired product. When the product is an MRAM, the substrate10is, for example, a Si substrate having a circuit structure. When the product is a magnetic head, the substrate10is, for example, an AlTiC substrate that is easy to process.

(Underlayer)

The underlayer20is positioned between the substrate10and the first ferromagnetic layer30. The underlayer20is a 3-layer structure laminate in which a first underlayer21, a second underlayer22, and a third underlayer23are laminated in this order on the substrate10.

The first underlayer21functions as a buffer layer that reduces a difference between a lattice constant of the substrate10and a lattice constant of the second underlayer22. The material of the first underlayer21may be either a conductive material or an insulating material. The material of the first underlayer21differs depending on the material of the substrate10and the material of the second underlayer22, but is, for example, a compound having a (001)-oriented NaCl structure. The compound having a NaCl structure is, for example, a nitride containing at least one element selected from the group consisting of Ti, Zr, Nb, V, Hf, Ta, Mo, W, B, Al, and Ce or an oxide containing at least one element selected from the group consisting of Mg, Al, and Ce.

In addition, regarding the material of the first underlayer21, for example, a (002)-oriented perovskite conductive oxide represented by a composition formula of ABO3can be used. The perovskite conductive oxide is, for example, an oxide that contains at least one element selected from the group consisting of Sr, Ce, Dy, La, K, Ca, Na, Pb, and Ba at a site A and at least one element selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Ga, Nb, Mo, Ru, Ir, Ta, Ce, and Pb at a site B.

The second underlayer22functions as a seed layer that improves the crystallinity of an upper layer laminated on the second underlayer22. The second underlayer22contains, for example, at least one type of MgO, TiN and NiTa alloys. In addition, for example, an alloy containing Co and Fe can be used. An alloy containing Co and Fe is, for example, Co—Fe, Co—Fe—B.

The third underlayer23functions as a buffer layer that reduces a difference between the lattice constant of the second underlayer22and the lattice constant of the first ferromagnetic layer30. The third underlayer23may be a layer containing a metal element, for example, at least one metal element of Ag, Au, Cu, Cr, V, Al, W, and Pt so that it can be used as an electrode for allowing a detection current to flow. In addition, it may be a layer containing any of a metal having a function of generating a spin current due to a spin Hall effect when a current flows, an alloy, an intermetallic compound, a metal boride, a metal carbide, a metal silicide, and a metal phosphide. In addition, for example, it may be a layer having a (001)-oriented tetragonal structure or cubic structure and containing at least one element selected from the group consisting of Al, Cr, Fe, Co, Rh, Pd, Ag, Ir, Pt, Au, Mo, W, and Pt. The third underlayer23may be a laminate made of a material containing an alloy of these metal elements or two or more types of these metal elements. Examples of alloys of these metal elements include a cubic AgZn alloy, an AgMg alloy, a CoAl alloy, an FeAl alloy and a NiAl alloy.

Here, the underlayer20is used to improve the crystallinity of the upper layer formed on the underlayer20because it functions as a buffer layer that reduces a difference in lattice constant between the substrate10and the first ferromagnetic layer30. As necessary, any of the first underlayer21, the second underlayer22, and the third underlayer23can be omitted. In addition, as necessary, any of the first underlayer21, the second underlayer22, and the third underlayer23can be formed of the same materials. In addition, as necessary, a plurality of respective underlayers can be laminated by increasing the number thereof.

(First Ferromagnetic Layer and Second Ferromagnetic Layer)

The first ferromagnetic layer30and the second ferromagnetic layer70are magnetic components. The first ferromagnetic layer30and the second ferromagnetic layer70each have a magnetization. The magnetoresistance effect element101outputs a change in relative angle between the magnetization of the first ferromagnetic layer30and the magnetization of the second ferromagnetic layer70as a change in resistance value.

For example, the magnetization of the second ferromagnetic layer70changes more easily than the magnetization of the first ferromagnetic layer30. When a predetermined external force is applied, the magnetization direction of the first ferromagnetic layer30does not change (is fixed), and the magnetization direction of the second ferromagnetic layer70changes. When the magnetization direction of the second ferromagnetic layer70changes with respect to the magnetization direction of the first ferromagnetic layer30, the resistance value of the magnetoresistance effect element101changes. In this case, the first ferromagnetic layer30may be called a magnetization fixed layer, and the second ferromagnetic layer70may be called a magnetization free layer. Hereinafter, a case in which the first ferromagnetic layer30is a magnetization fixed layer and the second ferromagnetic layer70is a magnetization free layer will be exemplified, but this relationship may be reversed.

A difference in ease of change between the magnetization of the first ferromagnetic layer30and the magnetization of the second ferromagnetic layer70when a predetermined external force is applied is caused by a difference in coercive force between the first ferromagnetic layer30and the second ferromagnetic layer70. For example, when the thickness of the second ferromagnetic layer70is thinner than the thickness of the first ferromagnetic layer30, a coercive force of the second ferromagnetic layer70is smaller than a coercive force of the first ferromagnetic layer30. In addition, for example, an antiferromagnetic layer is provided on the surface of the first ferromagnetic layer30opposite to the non-magnetic layer50with a spacer layer therebetween. The first ferromagnetic layer30, the spacer layer, and the antiferromagnetic layer form a synthetic antiferromagnetic structure (SAF structure). The synthetic antiferromagnetic structure includes two magnetic layers with a spacer layer therebetween. When the first ferromagnetic layer30and the antiferromagnetic layer are antiferromagnetically coupled, a coercive force of the first ferromagnetic layer30becomes larger than when there is no antiferromagnetic layer. The antiferromagnetic layer is formed of, for example, IrMn or PtMn. For example, the spacer layer contains at least one selected from the group consisting of Ru, Ir, and Rh. In a method of generating a coercive force difference according to the thickness, an additional layer such as an antiferromagnetic layer that may cause parasitic resistance is not necessary. On the other hand, in a method of generating a coercive force difference according to the SAF structure, it is possible to improve the orientation of the magnetization of the first ferromagnetic layer30.

The first ferromagnetic layer30and the second ferromagnetic layer70each include a Heusler alloy represented by the following General Formula (1). Each of the first ferromagnetic layer30and the second ferromagnetic layer70is preferably made of a Heusler alloy represented by the following General Formula (1). However, the first ferromagnetic layer30and the second ferromagnetic layer70may contain inevitable impurities. The inevitable impurities are impurities that are inevitably mixed into production materials or mixed in a production process. The inevitable impurities include elements that constitute layers other than the first ferromagnetic layer30and the second ferromagnetic layer70.
Co2FeαXβ(1)
(in Formula (1), X represents one or more elements selected from the group consisting of Mn, Cr, Si, Al, Ga and Ge, and α and β represent numbers that satisfy 2.3≤α+β, α<β, and 0.5<α<1.9).

The Heusler alloy is a half metal in which electrons carrying a current that flows through an alloy have only upward or downward spins, and ideally have a spin polarizability of 100%. The Heusler alloy generally has a composition of Co2FeαXβ(α=β=1) and has a lattice structure called an L21 structure. On the other hand, in the Heusler alloy of General Formula (1), α and β are set to 2.3≤α+β, which deviate from a stoichiometric composition. It is thought that, when a Heusler alloy which deviates from a stoichiometric composition is used as the material of the first ferromagnetic layer30and the second ferromagnetic layer70, the magnetoresistance effect element101having a large MR ratio and RA can be obtained. However, when the composition of the Heusler alloy excessively deviates from the stoichiometric composition, there is a risk of defects occurring in the L21 structure and the effect of increasing the MR ratio and RA of the magnetoresistance effect element101being weakened. Therefore, α+β preferably satisfies 2.3≤α+β<2.66, and particularly preferably satisfies 2.45<α+β<2.66. Here, α is the number of Fe atoms when the number of Co atoms is 2, and β is the number of atoms of a component X when the number of Co atoms is 2.

In addition, in the Heusler alloy of General Formula (1), α and β satisfy α<β. Accordingly, antisites in which Fe atoms are substituted into Co atom sites are inhibited. Thereby, the variation in the Fermi level due to antisites in which Fe atoms are substituted into Co atom sites is minimized, and characteristics of the Heusler alloy as a half metal can be stably exhibited. Therefore, the MR ratio of the magnetoresistance effect element101is improved. However, when β is too large, that is, when the amount of the component X is much larger than that of Fe, there is a risk of defects occurring in the L21 structure and the effect of improving the MR ratio of the magnetoresistance effect element101being weakened. α and β preferably satisfy α<0<2×α and particularly preferably satisfy α<β<1.5×α.

In addition, in the Heusler alloy of General Formula (1), a satisfies 0.5<α<1.9. Accordingly, it is possible to secure high spin polarizability of the Heusler alloy. Accordingly, the MR ratio of the magnetoresistance effect element101becomes larger. In order to inhibit antisites in which Fe atoms are substituted into Co atom sites while maintaining the effect of improving the MR ratio of the magnetoresistance effect element101, α preferably satisfies 0.8<α<1.33 and particularly preferably satisfies 0.9<α<1.2.

The component X is one or more elements selected from the group consisting of Mn, Cr, Si, Al, Ga and Ge. Among these elements, Mn, Ga and Ge are preferable.

The Heusler alloy of General Formula (1) is preferably, for example, an alloy represented by the following General Formula (2).
Co2FeαGaγYβ-γ(2)
(in Formula (2), Y represents one or more elements selected from the group consisting of Mn, Cr, Si, Al and Ge, and α, β and γ represent numbers that satisfy 2.3≤α+β, α<β, and 0.5<α<1.9, 0.1≤γ).

Since the Heusler alloy of General Formula (2) includes 0.1 or more Ga atoms when the number of Co atoms is 2, it can be regularized at a low temperature. Therefore, in the magnetoresistance effect element101using the Heusler alloy of General Formula (2), atomic interdiffusion is reduced in all elements, and the MR ratio is improved.

In the Heusler alloy of General Formula (2), preferably, β and γ represent numbers that satisfy 2×γ<β, that is, the number of Ga atoms is smaller than the number of atoms of a component Y. Accordingly, it is possible to prevent Ga from diffusing into other layers due to an excessively large number of Ga atoms.

In addition, the Heusler alloy of General Formula (1) is preferably, for example, an alloy represented by the following General Formula (3).
Co2FeαGeδZβ-δ(3)
(in Formula (3), Z represents one or more elements selected from the group consisting of Mn, Cr, Si, Al and Ga, and α, β and δ represent numbers that satisfy 2.3≤α+β, α<β, and 0.5<α<1.9, 0.1≤δ).

The Heusler alloy of General Formula (3) includes 0.1 or more Ge atoms when the number of Co atoms is 2. Ge is a semiconductor element and has a function of increasing the resistivity of the Heusler alloy. Therefore, the magnetoresistance effect element101using the Heusler alloy of General Formula (3) has a larger RA.

In the Heusler alloy of General Formula (3), preferably, β and δ represent numbers that satisfy 2×δ>β, that is, the number of Ge atoms is larger than the number of atoms of a component Z. Accordingly, the effect of Ge atoms can be obtained more reliably. However, when the Ge content is too large, since the resistivity of the Heusler alloy is too large, there is a risk of Ge becoming a parasitic resistance component of the magnetoresistance effect element101and the magnetoresistance effect being weakened. Therefore, δ more preferably satisfies 0.63<δ<1.26 and particularly preferably satisfies 0.84<δ<1.26.

In addition, the Heusler alloy of General Formula (1) is preferably, for example, an alloy represented by the following General Formula (4).
Co2FeαGaγGeδ(4)
(in Formula (4), α, γ and δ represent numbers that satisfy 2.3≤α+γ+γ, α<γ+δ, and 0.5<α<1.9, 0.1γ, 0.1≤δ).

The Heusler alloy of General Formula (4) is an alloy containing Ga and Ge as the component X in the Heusler alloy of General Formula (1). Therefore, γ+β in General Formula (4) corresponds to β in General Formula (1). The Heusler alloy of General Formula (4) has improved characteristics as a half metal due to a synergistic effect of Ga and Ge, and an improved spin polarizability. Therefore, the magnetoresistance effect element101using the Heusler alloy of General Formula (4) has a larger MR ratio and RA due to the synergistic effect of Ga and Ge.

In General Formula (4), preferably, γ and δ represent numbers that satisfy γ<δ, that is, the number of Ge atoms is larger than the number of Ga atoms. In addition, δ more preferably satisfies 0.63<δ<1.26 and particularly preferably satisfies 0.84<δ<1.26. When γ and δ satisfy this relationship, the effects of Ga and Ge are strongly exhibited and the MR ratio and RA of the magnetoresistance effect element101become larger.

In addition, in General Formula (4), α, γ and δ preferably satisfy 2.3≤α+γ+δ<2.66 and particularly preferably satisfy 2.45<α+γ+δ<2.66. When α, γ and δ satisfy this relationship, the MR ratio and RA of the magnetoresistance effect element101become larger.

In addition, the Heusler alloy of General Formula (1) is preferably, for example, an alloy represented by the following General Formula (5)
Co2FeαGaγGeδMnε(5)
(in Formula (5), α, γ, δ and ε represent numbers that satisfy 2.3≤α+γ+δ+ε, α<γ+δ+ε, and 0.5<α<1.9, 0.1γ, 0.1≤δ, 0.1≤ε).

The Heusler alloy of General Formula (5) is an alloy containing Ga, Ge, and Mn as the component X in the Heusler alloy of General Formula (1). Therefore, γ+δ+ε in General Formula (5) corresponds to β in General Formula (1).

Mn has an effect of increasing the MR ratio and RA of the magnetoresistance effect element101when it coexists with Ga and Ge. In addition, in this case antisites in which Mn atoms are substituted into Co atom sites do not inhibit half metal characteristics. In General Formula (5), preferably, δ and ε represent numbers that satisfy δ<ε, that is, the number of Mn atoms is larger than the number of Ge atoms. In addition, preferably, γ and δ represent numbers that satisfy δ<γ, that is, the number of Ga atoms is larger than the number of Ge atoms. Specifically, preferably, γ satisfies 0.4<γ<0.6, δ satisfies 0.2<δ<0.4, and E satisfies 0.38<ε<0.76. When γ, δ and ε satisfy this relationship, the effects of Ga, Ge, and Mn are strongly exhibited, and the MR ratio and RA of the magnetoresistance effect element101become larger.

In addition, in General Formula (5), α, γ, δ and ε preferably satisfy 2.3≤α+γ+δ+ε<2.66 and particularly preferably satisfy 2.45<α+γ+δ+ε<2.66. When α, γ, δ and ε satisfy this relationship, the MR ratio and RA of the magnetoresistance effect element101become larger.

Each of the first ferromagnetic layer30and the second ferromagnetic layer70may be a single layer or may be a laminate including two or more layers. When the first ferromagnetic layer30and the second ferromagnetic layer70are a laminate, respective ferromagnetic layers may have different compositions and regularities. When the first ferromagnetic layer30and/or the second ferromagnetic layer70are a laminate, a ferromagnetic layer in contact with the non-magnetic layer50among two or more ferromagnetic layers preferably has an Fe concentration that is equal to or higher than that of the ferromagnetic layer opposite to the non-magnetic layer50. However, the Fe concentration of the ferromagnetic layer in contact with the non-magnetic layer50is preferably 3 times or less the Fe concentration of the ferromagnetic layer opposite to the non-magnetic layer50. In addition, when two or more ferromagnetic layers each contains Ge, the ferromagnetic layer in contact with the non-magnetic layer50among the two or more ferromagnetic layers preferably has a Ge concentration that is equal to or smaller than that of the ferromagnetic layer opposite to the non-magnetic layer50.

However, the Ge concentration of the ferromagnetic layer in contact with the non-magnetic layer50is preferably ⅓ or more of the Ge concentration of the ferromagnetic layer opposite to the non-magnetic layer50. In addition, when two or more ferromagnetic layers each contains Ga, the ferromagnetic layer in contact with the non-magnetic layer50among the two or more ferromagnetic layers preferably has a Ga concentration that is equal to or larger than that of the ferromagnetic layer opposite to the non-magnetic layer50. However, the Ga concentration of the ferromagnetic layer in contact with the non-magnetic layer50is preferably 3 times or less the Ga concentration of the ferromagnetic layer opposite to the non-magnetic layer50. In addition, the ferromagnetic layer in contact with the non-magnetic layer50among the two or more ferromagnetic layers preferably has a higher regularity than the ferromagnetic layer opposite to the non-magnetic layer50.

When the first ferromagnetic layer30and/or the second ferromagnetic layer70are a single layer, the surface in contact with the non-magnetic layer50preferably has an Fe concentration that is equal to or higher than that of the surface on the side opposite to the non-magnetic layer50. However, the Fe concentration of the layer in contact with the non-magnetic layer50is preferably 3 times or less the Fe concentration of the surface on the side opposite to the non-magnetic layer50. In addition, when the first ferromagnetic layer30and/or the second ferromagnetic layer70contain Ge, the surface in contact with the non-magnetic layer50preferably has a Ge concentration that is equal to or smaller than that of the surface on the side opposite to the non-magnetic layer50. However, the Ge concentration of the surface in contact with the non-magnetic layer50is preferably ⅓ or more of the Ge concentration of the surface on the side opposite to the non-magnetic layer50. In addition, when the first ferromagnetic layer30and/or the second ferromagnetic layer70contain Ga, the surface in contact with the non-magnetic layer50preferably has a Ga concentration that is equal to or larger than that of the surface on the side opposite to the non-magnetic layer50. However, the Ga concentration of the surface in contact with the non-magnetic layer50is preferably 3 times or less the Ga concentration of the surface on the side opposite to the non-magnetic layer50. In addition, the surface in contact with the non-magnetic layer50of the first ferromagnetic layer30and the second ferromagnetic layer70preferably has a higher regularity than the surface on the side opposite to the non-magnetic layer50.

Here, the regularity of the ferromagnetic layer will be described.FIGS.2A,2B,2C,2D,2E, and2Fshow schematic views of an example of a crystal structure of a Heusler alloy,FIGS.2A,2B and2Cshow an example of a crystal structure of a full Heusler alloy, andFIGS.2D,2E and2Fshow an example of a crystal structure of a half Heusler alloy.

The crystal structure shown inFIG.2Ais called an L21 structure. In the L21 structure, the elements that enter the P sites, the elements that enter the Q sites, and the elements that enter the R sites are fixed. The crystal structure shown inFIG.2Bis called a B2 structure derived from the L21 structure. In the B2 structure, the elements that enter the Q sites and the elements that enter the R sites are mixed, and the elements that enter the P sites are fixed. The crystal structure shown inFIG.2Cis called an A2 structure derived from the L21 structure. In the A2 structure, the elements that enter the P sites, the elements that enter the Q sites, and the elements that enter the R sites are mixed.

The crystal structure shown inFIG.22Dis called a C1bstructure. In the C1bstructure, the elements that enter the P sites, the elements that enter the Q sites, and the elements that enter the R sites are fixed. The crystal structure shown inFIG.2Eis called a B2 structure derived from the C1bstructure. In the B2 structure, the elements that enter the Q sites and the elements that enter the R sites are mixed, and the elements that enter the P sites are fixed. The crystal structure shown inFIG.2Fis called an A2 structure derived from the C1bstructure. In the A2 structure, the elements that enter the P sites, the elements that enter the Q sites, and the elements that enter the R sites are mixed.

Full Heusler alloys have decreasing regularity in the order of L21 structure>B2 structure>A2 structure, and half Heusler alloys have a decreasing regularity in the order of C1bstructure>B2 structure>A2 structure. While these crystal structures have different regularities, they are all crystals.

When the first ferromagnetic layer30and/or the second ferromagnetic layer70are a single layer, the surface in contact with the non-magnetic layer50preferably has a higher Fe concentration than the surface on the side opposite to the non-magnetic layer50. In addition, when the first ferromagnetic layer30and/or the second ferromagnetic layer70contain Ge, the surface in contact with the non-magnetic layer50preferably has a smaller Ge concentration than the surface on the side opposite to the non-magnetic layer50In addition, when the first ferromagnetic layer30and/or the second ferromagnetic layer70contain Ga, the surface in contact with the non-magnetic layer50preferably has a higher Ga concentration than the surface on the side opposite to the non-magnetic layer50. In addition, the surface in contact with the non-magnetic layer50preferably has a higher regularity than the surface on the side opposite to the non-magnetic layer50.

The Heusler alloy constituting the first ferromagnetic layer30and the second ferromagnetic layer70crystallizes. Whether the Heusler alloy has crystallized can be determined using a transmission electron microscope (TEM) image (for example, high-angle annular dark-field scanning transmission electron microscope image: HAADF-STEM image) or an electron beam diffraction image using a transmission electron beam. When the Heusler alloy has crystallized, a status in which atoms are regularly arranged can be confirmed, for example, in the HAADF-STEM image captured using the TEM. More specifically, in the Fourier transform image of the HAADF-STEM image, spots derived from the crystal structure of the Heusler alloy appear. In addition, when the Heusler alloy has crystallized, diffraction spots can be confirmed from at least one plane among the (001) plane, the (002) plane, the (110) plane, and the (111) plane in the electron beam diffraction image. When crystallization is confirmed by at least one of the methods, it can be said that at least a part of the Heusler alloy has crystallized.

In addition, the crystal structure of the Heusler alloy can be measured by X-ray diffraction (XRD), reflection high-energy electron diffraction (RHEED), or the like. For example, in the case of XRD, when the Heusler alloy has an L21 structure, (200) and (111) peaks are exhibited, and when the Heusler alloy has a B2 structure, the (200) peak is exhibited but the (111) peak is not exhibited. For example, in the case of RHEED, when the Heusler alloy has an L21 structure, the (200) streak and the (111) streak are exhibited, and when the Heusler alloy has a B2 structure, the (200) streak is exhibited but the (111) streak is not exhibited.

The composition analysis of respective layers constituting the magnetoresistance effect element can be performed using energy dispersive X-ray analysis (EDS). In addition, when EDS line analysis is performed, for example, the composition distribution of respective materials in the film thickness direction can be confirmed.

In addition, the composition of the Heusler alloy can be measured using an X-ray fluorescence method (XRF), inductively coupled plasma (ICP) atomic emission spectroscopy, secondary ion mass spectrometry (SIMS), auger electron spectroscopy (AES), or the like.

(First NiAl layer and second NiAl layer)

The first NiAl layer40and the second NiAl layer60are layers containing a NiAl alloy. The first NiAl layer40functions as a buffer layer that reduces a lattice mismatch between the first ferromagnetic layer30and the non-magnetic layer50, and the second NiAl layer60functions as a buffer layer that reduces a lattice mismatch between the non-magnetic layer50and the second ferromagnetic layer70. According to the function of the first NiAl layer40and the second NiAl layer60, the MR ratio of the magnetoresistance effect element101is further improved.

The thickness t of each of the first NiAl layer40and the second NiAl layer60preferably satisfies 0<t≤0.63 nm. When the thickness t is too thick, there is a risk of electrons moving from the first ferromagnetic layer30(the second ferromagnetic layer70) to the second ferromagnetic layer70(the first ferromagnetic layer30) being spin-scattered. When the thickness t is within this range, spin scattering in the electrons that move is minimized, a lattice mismatch between the first ferromagnetic layer30and the non-magnetic layer50is reduced, and a lattice mismatch between the non-magnetic layer50and the second ferromagnetic layer70is reduced. As a result, the magnetoresistance effect is particularly improved.

Each of the first NiAl layer40and the second NiAl layer60is preferably a layer made of a NiAl alloy. The first NiAl layer40and the second NiAl layer60may contain inevitable impurities. The inevitable impurities include elements that constitute layers other than the first NiAl layer40and the second NiAl layer60. In addition, proportions of Ni and Al contained in the NiAl alloy may be the same as or different from each other. The proportions of Ni and Al are preferably in a range of 1:3 to 3:1 in terms of molar ratio. In addition, the first NiAl layer40and the second NiAl layer60may have different proportions of Ni and Al. For example, the first NiAl layer40may contain a larger amount of Al than of Ni, and the second NiAl layer60may contain a larger amount of Ni than of Al.

(Non-Magnetic Layer)

The non-magnetic layer50contains a non-magnetic metal. The non-magnetic layer50is preferably made of a non-magnetic metal. However, the non-magnetic layer may contain inevitable impurities. The inevitable impurities include elements that constitute layers other than the non-magnetic layer50. Examples of materials of the non-magnetic layer50include Cu, Au, Ag, Al, and Cr. The non-magnetic layer50preferably contains one or more elements selected from the group consisting of Ag, Cu, Au, Ag, Al, and Cr as a main constituent element. The main constituent element means that a proportion of Cu, Au, Ag, Al, or Cr in the composition formula is 50% or more. The non-magnetic layer50preferably contains Ag, and preferably contains Ag as a main constituent element. Since Ag has a long spin diffusion length, the magnetoresistance effect element101using Ag has a larger MR ratio.

For example, the non-magnetic layer50has a thickness in a range of 1 nm or more and 10 nm or less. The non-magnetic layer50inhibits magnetic coupling between the first ferromagnetic layer30and the second ferromagnetic layer70.

(Cap Layer)

The cap layer80is positioned on the side of the magnetoresistance effect element101opposite to the substrate10. The cap layer80is provided to protect the second ferromagnetic layer70. The cap layer80minimizes diffusion of atoms from the second ferromagnetic layer70. In addition, the cap layer80contributes to crystal orientation of respective layers of the magnetoresistance effect element101. When the cap layer80is provided, the magnetization of the first ferromagnetic layer30and the second ferromagnetic layer70can be stabilized and the MR ratio of the magnetoresistance effect element101can be improved.

The cap layer80preferably contains a material having high conductivity so that it can be used as an electrode for allowing a detection current to flow. For example, the cap layer80may contain one or more metal elements of Ru, Ag, Al, Cu, Au, Cr, Mo, Pt, W, Ta, Pd, and Ir, an alloy of these metal elements, or a laminate made of a material containing two or more types of these metal elements.

In the magnetoresistance effect element101of the present embodiment, on at least one of the first ferromagnetic layer30and the second ferromagnetic layer70, a layer containing Ni may be provided on the side opposite to the non-magnetic layer50. That is, an insertion layer containing Ni may be inserted between the first ferromagnetic layer30and the substrate10(the underlayer20when the underlayer20is provided) and/or between the second ferromagnetic layer70and the cap layer80. The insertion layer (first insertion layer) between the first ferromagnetic layer30and the substrate10(or the underlayer20) and the insertion layer (second insertion layer) between the second ferromagnetic layer70and the cap layer80are preferably made of Ni. However, the first insertion layer and the second insertion layer may contain inevitable impurities. The inevitable impurities include elements that constitute layers other than the first insertion layer and the second insertion layer.

Next, a method of producing the magnetoresistance effect element101according to the present embodiment will be described. For example, the magnetoresistance effect element101can be obtained by laminating the underlayer20(the first underlayer21, the second underlayer22, and the third underlayer23), the first ferromagnetic layer30, the first NiAl layer40, the non-magnetic layer50, the second NiAl layer60, the second ferromagnetic layer70, and the cap layer80in this order on the substrate10. Regarding a method of forming each layer, for example, a sputtering method, a vapor deposition method, a laser ablation method, or a molecular beam epitaxy (MBE) method can be used. Regarding a method of forming a first insertion layer and a second insertion layer, for example, a sputtering method, a vapor deposition method, a laser ablation method or a molecular beam epitaxy (MBE) method can be used.

In addition, after the underlayer20is formed or after the second ferromagnetic layer70is laminated, the substrate10may be annealed. According to annealing, the crystallinity of respective layers is improved.

The ratio of Ni and Al in the first NiAl layer40and the second NiAl layer60can be adjusted by a co-sputtering method. For example, a NiAl layer containing a large amount of Ni can be formed by a co-sputtering method using a NiAl alloy target and a Ni target. Similarly, a NiAl layer containing a large amount of Al can be formed by a co-sputtering method using a NiAl alloy target and an Al target.

When the first ferromagnetic layer30and/or the second ferromagnetic layer70is a laminate, the composition of the ferromagnetic layer can be adjusted by a co-sputtering method. Two ferromagnetic layers having different iron concentrations can be obtained, for example, one layer is formed by a sputtering method using a CoFeGaGe alloy target and the other layer is formed by a co-sputtering method using a CoFeGaGe alloy target and an Fe target.

When the first ferromagnetic layer30and/or the second ferromagnetic layer70are a single layer, the composition of the ferromagnetic layer can be adjusted by a co-sputtering method using a CoFeGaGe alloy target and an Fe target. For example, regarding the ferromagnetic layer in which the iron concentration differs between the surface in contact with the non-magnetic layer50and the surface on the side opposite to the non-magnetic layer50, the ferromagnetic layer having an iron concentration gradient in the first ferromagnetic layer30and/or the second ferromagnetic layer70can be obtained by setting a film-forming power of a CoFeGaGe alloy target to be constant and by performing deposition while continuously changing a film-forming power of the Fe target.

When the first ferromagnetic layer30and/or the second ferromagnetic layer70are a laminate, the regularity of the ferromagnetic layer can be adjusted by a heat treatment for film formation. When the ferromagnetic layer after film formation is heated at a relatively high temperature, a ferromagnetic layer having high regularity is obtained, and when the ferromagnetic layer after film formation is heated at a relatively low temperature, a ferromagnetic layer having a low regularity is obtained. Since the relationship between the regularity and the heat treatment temperature varies depending on the material and thickness of the ferromagnetic layer, the heat treatment temperature cannot be determined uniformly. However, in order to obtain a ferromagnetic layer having high regularity, the heat treatment temperature is preferably in a range of 400° C. or higher and 700° C. or lower.

t

The magnetoresistance effect element101according to the present embodiment can be used as, for example, a current-perpendicular-to-plane-giant magnetic resistance element (CPP-GMR element) that exhibits a magnetoresistance effect by causing a current to flow through the magnetoresistance effect element101in the direction perpendicular to the film surface.

In the magnetoresistance effect element101of the present embodiment configured as described above, since the first ferromagnetic layer30and the second ferromagnetic layer70are formed using a specific Heusler alloy represented by any one of the above General Formulae (1) to (5), high spin polarizability can be secured in the first ferromagnetic layer30and the second ferromagnetic layer70, and a relatively high resistivity is obtained. Therefore, the MR ratio (Magnetoresistance ratio) and RA (Resistance Area product) of the magnetoresistance effect element101become larger. Therefore, when the magnetoresistance effect element101is used as the current-perpendicular-to-plane-giant magnetic resistance element (CPP-GMR element), it is possible to reduce a current density during operation.

In addition, in the magnetoresistance effect element101of the present embodiment, the following actions and effects can be obtained. Here, the following actions and effects can be obtained in the magnetoresistance effect element in which the material of the first ferromagnetic layer30and/or the second ferromagnetic layer70is a Heusler alloy having a stoichiometric composition.

In addition, when the first ferromagnetic layer30and/or the second ferromagnetic layer70are a laminate, the Fe concentration of the ferromagnetic layer in contact with the non-magnetic layer50among two or more ferromagnetic layers is set to be higher than that of the ferromagnetic layer on the side opposite to the non-magnetic layer50, and thus the magnetization near the interface with the non-magnetic layer50is stable. As a result, the MR ratio of the magnetoresistance effect element101is improved. In particular, when the Fe concentration of the ferromagnetic layer in contact with the non-magnetic layer50within the first ferromagnetic layer30is set to be higher than that of the ferromagnetic layer on the side of the substrate10, this effect can be more easily obtained.

In addition, if the first ferromagnetic layer30and/or the second ferromagnetic layer70are a laminate, when two or more ferromagnetic layers each contains Ge, the Ge concentration of the ferromagnetic layer in contact with the non-magnetic layer50among two or more ferromagnetic layers is set to be lower than that of the ferromagnetic layer on the side opposite to the non-magnetic layer50, and thus the magnetization near the interface with the non-magnetic layer50is stable. As a result, the MR ratio of the magnetoresistance effect element101is improved. In particular, when the Ge concentration of the ferromagnetic layer in contact with the non-magnetic layer50within the first ferromagnetic layer30is set to be smaller than that of the ferromagnetic layer on the side of the substrate10, this effect can be more easily obtained.

In addition, if the first ferromagnetic layer30and/or the second ferromagnetic layer70are a laminate, when two or more ferromagnetic layers each contains Ga, the Ga concentration of the ferromagnetic layer in contact with the non-magnetic layer50among two or more ferromagnetic layers is set to be higher than that of the ferromagnetic layer on the side opposite to the non-magnetic layer50, and thus the interface resistance with the non-magnetic layer50can increase. As a result, the RA increases and the MR ratio of the magnetoresistance effect element101is improved. In particular, when the Ga concentration of the ferromagnetic layer in contact with the non-magnetic layer50of both the first ferromagnetic layer30and the second ferromagnetic layer70increases, this effect can be more easily obtained.

In addition, when the first ferromagnetic layer30and/or the second ferromagnetic layer70are a laminate, the regularity of the ferromagnetic layer in contact with the non-magnetic layer50among two or more ferromagnetic layers is set to be higher than that of the ferromagnetic layer on the side opposite to the non-magnetic layer50, and thus the spin polarizability near the interface with the non-magnetic layer50can increase. As a result, the MR ratio of the magnetoresistance effect element101is improved. In particular, when the regularity of the ferromagnetic layer in contact with the non-magnetic layer50within the second ferromagnetic layer70is set to be higher than that of the ferromagnetic layer on the side of the cap layer80, this effect can be more easily obtained.

In addition, when the first NiAl layer40or the second NiAl layer60contains a larger amount of Ni than that of Al, it is possible to increase the interface resistance with the non-magnetic layer50. On the other hand, when the first NiAl layer40or the second NiAl layer60contains a larger amount of Al than that of Ni, it is possible to lower the resistivity of the first NiAl layer40or the second NiAl layer60and the parasitic resistance of the magnetoresistance effect element101having a GMR structure.

In addition, when one of the first NiAl layer40and the second NiAl layer60contains a larger amount of Ni than that of Al, and the other contains a larger amount of Al than that of Ni, it is possible to increase the interface resistance with the non-magnetic layer50, lower the resistivity of the first NiAl layer40or the second NiAl layer60, and more reliably lower the parasitic resistance of the magnetoresistance effect element101having a GMR structure. In particular, when the first NiAl layer40contains a larger amount of Al than that of Ni and the second NiAl layer60contains a larger amount of Ni than that of Al, this effect can be more easily obtained.

In addition, on at least one of the first ferromagnetic layer30and the second ferromagnetic layer70, a layer (insertion layer) containing Ni is provided on the side opposite to the non-magnetic layer50, and thus it is possible to reduce atomic interdiffusion between the underlayer20and the first ferromagnetic layer30or between the second ferromagnetic layer70and the cap layer80.

Second Embodiment

FIG.3is a cross-sectional view of a magnetoresistance effect element according to a second embodiment of the disclosure. A magnetoresistance effect element102is different from the magnetoresistance effect element101shown inFIG.1that it does not include the first NiAl layer40and the second NiAl layer60. Therefore, inFIG.3, components the same as those inFIG.1are denoted with the same reference numerals and descriptions thereof are omitted.

In the magnetoresistance effect element102of the present embodiment, since the first ferromagnetic layer30and the second ferromagnetic layer70are formed using a specific Heusler alloy, the same effects as those in the first embodiment can be obtained. In addition, the first ferromagnetic layer30, the non-magnetic layer50, and the second ferromagnetic layer70are in direct contact with each other without the first NiAl layer and the second NiAl layer. Accordingly, there are three layers that exhibit the magnetoresistance effect: the first ferromagnetic layer30, the second ferromagnetic layer70, and the non-magnetic layer50, and it is possible to decrease the thickness of the magnetoresistance effect element. Accordingly, a thin magnetoresistance effect element having a thickness suitable for high recording density can be obtained. In addition, since a process of forming the first NiAl layer40and the second NiAl layer60is not necessary, the production process can be simplified.

Third Embodiment

FIG.4is a cross-sectional view of a magnetoresistance effect element according to a third embodiment of the disclosure. A magnetoresistance effect element103is different from the magnetoresistance effect element101shown inFIG.1in that the underlayer20includes a fourth underlayer24. Therefore, inFIG.4, components the same as those inFIG.1are denoted with the same reference numerals and descriptions thereof are omitted.

The fourth underlayer24is disposed between the third underlayer23and the first ferromagnetic layer30. The fourth underlayer24functions as a seed layer that improves the crystallinity of the first ferromagnetic layer30laminated on the underlayer20. Regarding the material of the fourth underlayer24, for example, an alloy containing Co and Fe can be used. It has been reported that the Heusler alloy constituting the first ferromagnetic layer30has low magnetization stability near the laminate interface. On the other hand, the alloy containing Co and Fe has high magnetization stability and has high lattice matching with the Heusler alloy constituting the first ferromagnetic layer30. In the magnetoresistance effect element103using an alloy containing Co and Fe for the fourth underlayer24, since the magnetization of the Heusler alloy constituting the first ferromagnetic layer30is more stable, the MR ratio is improved at room temperature. The alloy containing Co and Fe is, for example, Co—Fe or Co—Fe—B.

While embodiments of the disclosure have been described above in detail with reference to the drawings, components in the embodiments, combinations thereof, and the like are examples, and additions, omissions, substitutions, and other modifications of components can be made without departing from the spirit and scope of the disclosure.

For example, in the magnetoresistance effect elements101,102, and103according to the embodiments, both the first ferromagnetic layer30and the second ferromagnetic layer70are formed using a specific Heusler alloy, but the disclosure is not limited thereto. At least one of the first ferromagnetic layer30and the second ferromagnetic layer70may be formed using a specific Heusler alloy. In this case, the ferromagnetic material forming the other first ferromagnetic layer30or second ferromagnetic layer70is, for example, a metal selected from the group consisting of Cr, Mn, Co, Fe and Ni, an alloy containing one or more of these metals, or an alloy containing these metals and at least one element of B, C and N. Among these ferromagnetic materials, Co—Fe or Co—Fe—B is preferable.

In addition, in the magnetoresistance effect elements101,102, and103according to the embodiments, the non-magnetic layer50is a layer made of a non-magnetic metal, but the disclosure is not limited thereto. Regarding the material of the non-magnetic layer50, an insulator or a semiconductor may be used.

In addition, the usage form of the magnetoresistance effect elements101,102, and103according to the embodiments is not limited to a current-perpendicular-to-plane-giant magnetic resistance element (CPP-GMR element). The magnetoresistance effect elements101,102, and103can be used as, for example, a current-in-plane-giant magnetic resistance element (CIP-GMR element) that exhibits a magnetoresistance effect by causing a current to flow through the magnetoresistance effect element101in the lamination surface direction. The magnetoresistance effect elements101,102, and103according to the embodiments can be applied to, for example, a magnetic head, a magnetic sensor, a magnetic memory, a high-frequency filter, or the like.

Next, application examples of the magnetoresistance effect element according to the present embodiment will be described. Here, in the following application examples, the magnetoresistance effect element101of the first embodiment is used as the magnetoresistance effect element, but the magnetoresistance effect element is not limited thereto, and for example, the same effects can be obtained using the magnetoresistance effect element102of the second embodiment and the magnetoresistance effect element103of the third embodiment.

FIG.5is a cross-sectional view of a magnetic recording device according to Application Example 1.FIG.5is a cross-sectional view of the magnetoresistance effect element101cut in the lamination direction of respective layers of the magnetoresistance effect element.

As shown inFIG.5, a magnetic recording device201includes a magnetic head210and a magnetic recording medium W. Here, inFIG.5, one direction in which the magnetic recording medium W extends is defined as an X direction, a direction perpendicular to the X direction is defined as a Y direction, and the XY plane is parallel to the main surface of the magnetic recording medium W. In addition, a direction in which the magnetic recording medium W is connected to the magnetic head210and is perpendicular to the XY plane is defined as a Z direction.

An air-bearing surface (medium facing surface) S faces the surface of the magnetic recording medium W, and at a position a certain distance away from the magnetic recording medium W, along the surface of the magnetic recording medium W, the magnetic head210can travel in directions of an arrow +X and arrow −X. The magnetic head210includes the magnetoresistance effect element101that functions as a magnetic sensor and a magnetic recording unit (not shown). A resistance-measuring device220is connected to the first ferromagnetic layer30and the second ferromagnetic layer70of the magnetoresistance effect element101.

The magnetic recording unit applies a magnetic field to a recording layer W1 of the magnetic recording medium W and determines the magnetization direction of the recording layer W1. That is, the magnetic recording unit performs magnetic recording of the magnetic recording medium W. The magnetoresistance effect element101reads information on the magnetization of the recording layer W1 written by the magnetic recording unit.

The magnetic recording medium W includes the recording layer W1 and a backing layer W2. The recording layer W1 is a part in which magnetic recording is performed and the backing layer W2 is magnetic path (magnetic flux path) in which a magnetic flux for writing is returned again to the magnetic head210. In the recording layer W1, the magnetic information is recorded as the magnetization direction.

The second ferromagnetic layer70of the magnetoresistance effect element101is a magnetization free layer. Therefore, the second ferromagnetic layer70exposed on the air-bearing surface S is influenced by the magnetization recorded in the facing recording layer W1 of the magnetic recording medium W. For example, inFIG.5, the magnetization direction of the second ferromagnetic layer70is oriented in the +z direction under the influence of the magnetization oriented in the +z direction of the recording layer W1. In this case, the magnetization directions of the first ferromagnetic layer30and the second ferromagnetic layer70, which are magnetization fixed layers, are parallel to each other.

Here, the resistance when the magnetization directions of the first ferromagnetic layer30and the second ferromagnetic layer70are parallel to each other is different from the resistance when the magnetization directions of the first ferromagnetic layer30and the second ferromagnetic layer70are antiparallel. Therefore, when the resistances of the first ferromagnetic layer30and the second ferromagnetic layer70are measured by the resistance-measuring device220, the information on the magnetization of the recording layer W1 can be read as a resistance value change.

Here, the shape of the magnetoresistance effect element101of the magnetic head210is not particularly limited. For example, in order to avoid the influence of a leakage magnetic field of the magnetic recording medium W with respect to the first ferromagnetic layer30of the magnetoresistance effect element101, the first ferromagnetic layer30may be provided at a position away from the magnetic recording medium W.

FIG.6is a cross-sectional view of a magnetic recording element according to Application Example 2.FIG.6is a cross-sectional view of the magnetoresistance effect element101cut in the lamination direction of respective layers of the magnetoresistance effect element.

As shown inFIG.6, a magnetic recording element202includes the magnetoresistance effect element101, and a power supply230and a measurement unit240connected to the first ferromagnetic layer30and the second ferromagnetic layer70of the magnetoresistance effect element101. When the third underlayer23of the underlayer20has conductivity, the power supply230and the measurement unit240may be connected to the third underlayer23instead of the first ferromagnetic layer30. In addition, when the cap layer80has conductivity, the power supply230and the measurement unit240may be connected to the cap layer80instead of the second ferromagnetic layer70. The power supply230provides a potential difference in the lamination direction of the magnetoresistance effect element101. The measurement unit240measures the resistance value of the magnetoresistance effect element101in the lamination direction.

When a potential difference is generated between the first ferromagnetic layer30and the second ferromagnetic layer70by the power supply230, a current flows in the lamination direction of the magnetoresistance effect element101. When the current is spin-polarized while passing through the first ferromagnetic layer30, it becomes a spin-polarized current. The spin-polarized current reaches the second ferromagnetic layer70with the non-magnetic layer50therebetween. The magnetization of the second ferromagnetic layer70receives a spin-transfer torque (STT) due to the spin-polarized current and the magnetization is reversed. When a relative angle between the magnetization direction of the first ferromagnetic layer30and the magnetization direction of the second ferromagnetic layer70is changed, the resistance value of the magnetoresistance effect element101in the lamination direction changes. The resistance value of the magnetoresistance effect element101in the lamination direction is read by the measurement unit240. That is, the magnetic recording element202shown inFIG.6is a spin-transfer torque (STT) type magnetic recording element.

FIG.7is a cross-sectional view of a magnetic recording element according to Application Example 3.FIG.7is a cross-sectional view of the magnetoresistance effect element101cut in the lamination direction of respective layers of the magnetoresistance effect element.

As shown inFIG.7, a magnetic recording element203includes the magnetoresistance effect element101, the power supply230connected to both ends of the third underlayer23of the magnetoresistance effect element101, and the measurement unit240connected to the third underlayer23and the second ferromagnetic layer70. The third underlayer23is a layer containing any of a metal having a function of generating a spin current due to a spin Hall effect when a current flows, an alloy, an intermetallic compound, a metal boride, a metal carbide, a metal silicide, and a metal phosphide. For example, the third underlayer23is a layer containing a non-magnetic metal including d electrons or f electrons in the outmost shell and having an atomic number of 39 or more. In addition, when the cap layer80has conductivity, the measurement unit240may be connected to the cap layer80instead of the second ferromagnetic layer70. The power supply230is connected to a first end and a second end of the third underlayer23. The power supply230provides a potential difference in the in-plane direction between one end (first end) of the third underlayer23and the end (second end) opposite to the first end. The measurement unit240measures the resistance value of the magnetoresistance effect element101in the lamination direction. In the magnetoresistance effect element101shown inFIG.7, the first ferromagnetic layer30is a magnetization free layer, and the second ferromagnetic layer70is a magnetization fixed layer.

When a potential difference is generated between the first end and the second end of the third underlayer23by the power supply230, a current flows through the third underlayer23. When a current flows through the third underlayer23, the spin Hall effect occurs due to the spin-orbit interaction. The spin Hall effect is a phenomenon in which moving spins are bent in the direction perpendicular to the direction in which a current flows. According to the spin Hall effect, an uneven distribution of spins in the third underlayer23is produced and a spin current is induced in the thickness direction of the third underlayer23. Spins are injected from the third underlayer23to the first ferromagnetic layer30by the spin current.

Spins injected into the first ferromagnetic layer30provide a spin orbit torque (SOT) to the magnetization of the first ferromagnetic layer30. The first ferromagnetic layer30receives the spin orbit torque (SOT) and reverses the magnetization. When the magnetization direction of the first ferromagnetic layer30and the magnetization direction of the second ferromagnetic layer70change, the resistance value of the magnetoresistance effect element101in the lamination direction changes. The resistance value of the magnetoresistance effect element101in the lamination direction is read by the measurement unit240. That is, the magnetic recording element203shown inFIG.7is a spin orbit torque (SOT) type magnetic recording element.

While the magnetoresistance effect element of the present embodiment has been described above, the application of the Heusler alloy according to the present embodiment represented by the above General Formula (1) is not limited to the magnetoresistance effect element. The Heusler alloy of the present embodiment can be applied as a material for, for example, a ferromagnetic layer of a spin current magnetization rotating element or a magnetic layer having a magnetic domain wall of a magnetic domain wall-moving element.

[Spin Current Magnetization Rotating Element]

FIG.8is a cross-sectional view of a spin current magnetization rotating element according to Application Example 4.

A spin current magnetization rotating element300is obtained by removing the first NiAl layer40, the non-magnetic layer50, the second NiAl layer60, the second ferromagnetic layer70and the cap layer80from the magnetic recording element203shown inFIG.7. In the spin current magnetization rotating element300, the first ferromagnetic layer30is made of the Heusler alloy represented by the above General Formula (1).

When a potential difference is generated between the first end and the second end of the third underlayer23by the power supply230, a current flows through the third underlayer23. When a current flows through the third underlayer23, the spin Hall effect occurs due to the spin-orbit interaction. Spins injected from the third underlayer23provide a spin orbit torque (SOT) to the magnetization of the first ferromagnetic layer30. The magnetization direction of the magnetization of the first ferromagnetic layer30changes due to the spin orbit torque (SOT).

When the magnetization direction of the first ferromagnetic layer30changes, polarization of reflected light changes due to the magnetic Kerr effect. In addition, when the magnetization direction of the first ferromagnetic layer30changes, polarization of transmitted light changes due to the magnetic Faraday effect. The spin current magnetization rotating element300can be used as an optical element using the magnetic Kerr effect or the magnetic Faraday effect.

[Magnetic Domain Wall-Moving Element (Magnetic Domain Wall-Moving Type Magnetic Recording Element)]

FIG.9is a cross-sectional view of a magnetic domain wall-moving element (magnetic domain wall-moving type magnetic recording element) according to Application Example 5. A magnetic domain wall-moving type magnetic recording element400includes a first ferromagnetic layer401, a second ferromagnetic layer402, a non-magnetic layer403, a first magnetization fixed layer404, and a second magnetization fixed layer405. Here, inFIG.9, a direction in which the first ferromagnetic layer401extends is defined as an X direction, a direction perpendicular to the X direction is defined as a Y direction, and a direction perpendicular to the XY plane is defined as a Z direction.

The non-magnetic layer403is inserted between the first ferromagnetic layer401and the second ferromagnetic layer402in the Z direction. The first magnetization fixed layer404and the second magnetization fixed layer405are connected to the first ferromagnetic layer401at a position between the second ferromagnetic layer402and the non-magnetic layer403in the X direction.

The first ferromagnetic layer401is a layer in which information can be magnetically recorded according to the change in the internal magnetic state. The first ferromagnetic layer401includes a first magnetic domain401A and a second magnetic domain401B therein. The magnetization of the first ferromagnetic layer401at a position overlapping the first magnetization fixed layer404or the second magnetization fixed layer405in the Z direction is fixed in one direction. The magnetization at a position overlapping the first magnetization fixed layer404in the Z direction is, for example, fixed in the +Z direction, and the magnetization at a position overlapping the second magnetization fixed layer405in the Z direction is, for example, fixed in the −Z direction. As a result, a magnetic domain wall DW is formed at the boundary between the first magnetic domain401A and the second magnetic domain401B. The first ferromagnetic layer401can have the magnetic domain wall DW therein. In the first ferromagnetic layer401shown inFIG.9, the magnetization M401Aof the first magnetic domain401A is oriented in the +Z direction, and the magnetization M401Bof the second magnetic domain401B is oriented in the −Z direction.

The magnetic domain wall-moving type magnetic recording element400can record data in multiple values or continuously depending on the position of the magnetic domain wall DW of the first ferromagnetic layer401. The data recorded in the first ferromagnetic layer401is read as a resistance value change of the magnetic domain wall-moving type magnetic recording element400when a read current is applied.

The ratio between the first magnetic domain401A and the second magnetic domain401B in the first ferromagnetic layer401changes when the magnetic domain wall DW moves. For example, the magnetization M402of the second ferromagnetic layer402has the same direction (parallel) as the magnetization M401Aof the first magnetic domain401A and has a direction (antiparallel) opposite to that of the magnetization M401Bof the second magnetic domain401B. When the magnetic domain wall DW moves in the +X direction and an area of the first magnetic domain401A in the part overlapping the second ferromagnetic layer402in a plan view in the z direction increases, the resistance value of the magnetic domain wall-moving type magnetic recording element400decreases. On the other hand, when the magnetic domain wall DW moves in the −X direction and an area of the second magnetic domain401B in the part overlapping the second ferromagnetic layer402in a plan view in the Z direction increases, the resistance value of the magnetic domain wall-moving type magnetic recording element400increases.

The magnetic domain wall DW moves when a write current flows in the X direction of the first ferromagnetic layer401or an external magnetic field is applied. For example, when a write current (for example, current pulse) is applied to the first ferromagnetic layer401in the +X direction, since electrons flow in the −X direction opposite to the direction of the current, the magnetic domain wall DW moves in the −X direction. When a current flows from the first magnetic domain401A toward the second magnetic domain401B, electrons spin-polarized in the second magnetic domain401B reverse the magnetization M401Aof the first magnetic domain401A. When the magnetization M401Aof the first magnetic domain401A is reversed, the magnetic domain wall DW moves in the −X direction.

The magnetic domain wall-moving type magnetic recording element400preferably has a large MR ratio and a large RA. When the MR ratio of the magnetic domain wall-moving type magnetic recording element400is large, a difference between the maximum value and the minimum value of the resistance value of the magnetic domain wall-moving type magnetic recording element400increases and the reliability of data increases. In addition, when the RA of the magnetic domain wall-moving type magnetic recording element400increases, the moving speed of the magnetic domain wall DW becomes slower and data can be recorded in an analog manner.

Regarding the material of the first ferromagnetic layer401, for example, the Heusler alloy represented by the above General Formula (1) is used. As described above, the magnetoresistance effect element using the Heusler alloy represented by the above General Formula (1) has a large MR ratio and a large RA. Regarding the material of the first ferromagnetic layer401, when the Heusler alloy represented by the above General Formula (1) is used, it is possible to increase the MR ratio and RA of the magnetic domain wall-moving type magnetic recording element400.

For the second ferromagnetic layer402, for example, a metal selected from the group consisting of Cr, Mn, Co, Fe and Ni, an alloy containing one or more of these metals, an alloy containing these metals and at least one element of B, C, and N, or the like can be used. Specifically, Co—Fe, Co—Fe—B, and Ni—Fe may be exemplified. Regarding the material of the second ferromagnetic layer402, the Heusler alloy represented by the above General Formula (1) may be used.

For the non-magnetic layer403, the same material as that of the non-magnetic layer50can be used. For the first magnetization fixed layer404and the second magnetization fixed layer405, the same material as that of the second ferromagnetic layer402can be used. The first magnetization fixed layer404and the second magnetization fixed layer405may have an SAF structure.

[Magnetic Domain Wall-Moving Element (Magnetic Thin Wire Device)]

FIG.10is a cross-sectional view of a magnetic domain wall-moving element (magnetic thin wire device) according to Application Example 6.

As shown inFIG.10, a magnetic thin wire device500includes a magnetic recording medium510, a magnetic recording head520, and a pulse power supply530. The magnetic recording head520is provided at a predetermined position on the magnetic recording medium510. The pulse power supply530is connected to the magnetic recording medium510so that a pulse current can be applied to the magnetic recording medium510in the in-plane direction. Here, inFIG.10, one direction in which the magnetic recording medium510extends is defined as an X direction, a direction perpendicular to the X direction is defined as a Y direction, and a direction perpendicular to the XY plane is defined as a Z direction.

The magnetic recording medium510includes a magnetic thin wire511, an underlayer512and a substrate513. The underlayer512is laminated on the substrate513and the magnetic thin wire511is laminated on the underlayer512. The magnetic thin wire511is a thin wire whose length in the X direction is longer than the width in the Y direction.

The magnetic thin wire511is formed of a magnetic material that can form a magnetic domain having a magnetization direction different from that of the other part in a part in the longitudinal direction. The magnetic thin wire511includes, for example, a first magnetic domain511A and a second magnetic domain511B. The magnetization M511Bof the second magnetic domain511B is oriented in a direction different from the magnetization M511Aof the first magnetic domain511A. The magnetic domain wall DW is formed between the first magnetic domain511A and the second magnetic domain511B. The second magnetic domain511B is generated by the magnetic recording head520.

The magnetic thin wire device500writes data by changing the position of the second magnetic domain511B of the magnetic thin wire511using a magnetic field generated from the magnetic recording head520or spin injection magnetization reversal while intermittently shifting and moving the magnetic domain wall DW of the magnetic thin wire511by a pulse current supplied from the pulse power supply530. The data written in the magnetic thin wire device500can be read using the magnetic resistance change or magneto-optical change. When the magnetic resistance change is used, a ferromagnetic layer is provided at a position facing the magnetic thin wire511with a non-magnetic layer therebetween. The magnetic resistance change occurs due to a difference in relative angle between the magnetization of the ferromagnetic layer and the magnetization of the magnetic thin wire511.

Regarding the material of the magnetic thin wire511, the Heusler alloy represented by the above General Formula (1) is used. Therefore, it is possible to increase the RA of the magnetic thin wire device500.

Regarding the material of the underlayer512, it is preferable to use a ferrite, which is an oxide insulator, in at least a part, and more specifically, a soft ferrite. Regarding the soft ferrite, Mn—Zn ferrite, Ni—Zn ferrite, Mn—Ni ferrite, or Ni—Zn—Co ferrite can be used. Since the soft ferrite has high magnetic permeability, a magnetic flux of a magnetic field generated by the magnetic recording head520is concentrated, and thus the second magnetic domain511B can be formed efficiently. For the substrate513, the same material as that of the above substrate10can be used.

[Magnetic Domain Wall-Moving Element (Magnetic Domain Wall-Moving Type Spatial Optical Modulator)]

FIG.11is a perspective view of a magnetic domain wall-moving element (magnetic domain wall-moving type spatial optical modulator) according to Application Example 7.

As shown inFIG.11, a magnetic domain wall-moving type spatial optical modulator600includes a first magnetization fixed layer610, a second magnetization fixed layer620, and a light-modulation layer630. Here, inFIG.11, one direction in which the light-modulation layer630extends is defined as an X direction, a direction perpendicular to the X direction is defined as a Y direction, and a direction perpendicular to the XY plane is defined as a Z direction.

The magnetization M610of the first magnetization fixed layer610and the magnetization M620of the second magnetization fixed layer620are oriented in different directions. For example, the magnetization M610of the first magnetization fixed layer610is oriented in the +Z direction, and the magnetization M620of the second magnetization fixed layer620is oriented in the −Z direction.

The light-modulation layer630can be divided into overlapping areas631and636, initial magnetic domain areas632and635, and magnetic domain change areas633and634.

The overlapping area631is an area overlapping the first magnetization fixed layer610in the Z direction, and the overlapping area636is an area overlapping the second magnetization fixed layer620in the Z direction. The magnetization M631of the overlapping area631is influenced by the leakage magnetic field from the first magnetization fixed layer610and is fixed, for example, in the +Z direction. The magnetization M636of the overlapping area636is influenced by the leakage magnetic field from the second magnetization fixed layer620and is fixed, for example, in the −Z direction.

The initial magnetic domain areas632and635are areas in which the magnetization is fixed in a direction different from that of the overlapping areas631and636under the influence of the leakage magnetic field from the first magnetization fixed layer610or the second magnetization fixed layer620. The magnetization M632of the initial magnetic domain area632is influenced by the leakage magnetic field from the first magnetization fixed layer610and is fixed, for example, in the −Z direction. The magnetization M635of the initial magnetic domain area635is influenced by the leakage magnetic field from the second magnetization fixed layer620and is fixed, for example, in the +Z direction.

The magnetic domain change areas633and634are areas in which the magnetic domain wall DW can move. The magnetization M633of the magnetic domain change area633and the magnetization M634of the magnetic domain change area634are oriented in opposite directions with the magnetic domain wall DW therebetween. The magnetization M633of the magnetic domain change area633is influenced by the initial magnetic domain area632and oriented, for example, in the −Z direction. The magnetization M634of the magnetic domain change area634is influenced by the leakage magnetic field from the initial magnetic domain area635and is fixed, for example, in the +Z direction. The boundary between the magnetic domain change area633and the magnetic domain change area634becomes the magnetic domain wall DW. The magnetic domain wall DW moves when a write current flows through the light-modulation layer630in the X direction or an external magnetic field is applied.

The magnetic domain wall-moving type spatial optical modulator600changes the position of the magnetic domain wall DW while moving the magnetic domain wall DW intermittently. Then, light L1 is caused to be incident on the light-modulation layer630and light L2 reflected by the light-modulation layer630is evaluated. The polarization state of the light L2 reflected by parts having different magnetization orientation directions differs. The magnetic domain wall-moving type spatial optical modulator600can be used as a video display device that uses a difference in polarization state of the light L2.

Regarding the material of the light-modulation layer630, the Heusler alloy represented by the above General Formula (1) is used. Accordingly, it is possible to increase the RA of the magnetic domain wall-moving type spatial optical modulator600, and the moving speed of the magnetic domain wall DW can be reduced. As a result, the position of the magnetic domain wall DW can be controlled more precisely and higher-definition video display is possible.

For the first magnetization fixed layer610and the second magnetization fixed layer620, the same material as that of the above first magnetization fixed layer404and second magnetization fixed layer405can be used.

EXAMPLES

Example 1

The magnetoresistance effect element101shown inFIG.1was produced as follows. The configurations of respective layers were as follows.

Substrate10: MgO single crystal substrate, thickness of 0.5 mm

Underlayer20:

First underlayer21: MgO layer, thickness of 10 nm

Second underlayer22: CoFe layer, thickness of 10 nm

Third underlayer23: Ag layer, thickness of 100 nm

First ferromagnetic layer30: Co2Fe1.03Ga0.41Ge0.86layer, thickness of 10 nm

First NiAl layer40: thickness of 0.21 nm

Non-magnetic layer50: Ag layer, thickness of 5 nm

Second NiAl layer60: thickness of 0.21 nm

Second ferromagnetic layer70: Co2Fe1.03Ga0.41Ge0.86layer, thickness of 8 nm

Cap layer80: Ru layer, thickness of 5 nm

The first underlayer21(MgO layer) was formed by heating the substrate10at 600° C. using an electron beam vapor deposition method. The substrate on which the first underlayer21was formed was left at 600° C. for 15 minutes and then cooled to room temperature. Next, the second underlayer22(CoFe layer) was formed on the first underlayer21by a sputtering method. Next, the third underlayer23(Ag layer) was formed on the second underlayer22by a sputtering method to form the underlayer20. The substrate10on which the underlayer20was formed was heated at 300° C. for 15 minutes, and then cooled to room temperature.

After cooling, the first ferromagnetic layer30(Co2Fe1.03Ga0.41Ge0.86layer) was formed on the underlayer20formed on the substrate10. The first ferromagnetic layer30was formed by a co-sputtering method using a Co2Fe1Ga0.5Ge0.5alloy target and a Ge target as targets.

The first NiAl layer40was formed on the first ferromagnetic layer30by a sputtering method. Next, the non-magnetic layer50(Ag layer) was formed on the first NiAl layer40by a sputtering method. Next, the second NiAl layer60was formed on the non-magnetic layer50in the same manner as that in the first NiAl layer40. Then, the second ferromagnetic layer70(Co2Fe1.03Ga0.41Ge0.86layer) was formed on the second NiAl layer60in the same manner as that in the first ferromagnetic layer30. The substrate10on which the second ferromagnetic layer70was formed was heated at 550° C. for 15 minutes, and then cooled to room temperature.

After cooling, the cap layer80(Ru layer) was formed on the second ferromagnetic layer70formed on the substrate10by an electron beam vapor deposition method. Thus, the magnetoresistance effect element101shown inFIG.1was produced.

Examples 2 and 3 and Comparative Example 1

The magnetoresistance effect element101was produced in the same manner as that in Example 1 except that the compositions of the first ferromagnetic layer30and the second ferromagnetic layer70were changed to the composition shown in the following Table 1. Here, the compositions of the first ferromagnetic layer30and the second ferromagnetic layer70were adjusted by a co-sputtering method using a Ge target.

Evaluation

The MR ratio (Magnetoresistance ratio) and RA (Resistance Area product) of the magnetoresistance effect elements produced in Examples 1 to 3 and Comparative Example 1 were measured. The results are shown in the following Table 1.

The MR ratio was evaluated using a microfabrication process technique such as EB lithography and ion milling, and a junction suitable for measurement was formed. When a constant current was applied to the junction of the magnetoresistance effect element101in the lamination direction, a voltage applied to the magnetoresistance effect element101was monitored using a voltmeter while sweeping the magnetic field to the magnetoresistance effect element101from the outside, and thus the change in the resistance value of the magnetoresistance effect element101was measured. A resistance value when the magnetization directions of the first ferromagnetic layer30and the second ferromagnetic layer70were parallel and a resistance value when the magnetization directions of the first ferromagnetic layer30and the second ferromagnetic layer70were antiparallel were measured, and the MR ratio was calculated from the obtained resistance values according to the following formula. The MR ratio was measured at 300 K (room temperature).
MRratio (%)=(RA−RP)/RP×100

RPwas a resistance value when the magnetization directions of the first ferromagnetic layer30and the second ferromagnetic layer70were parallel, and RAPwas a resistance value when the magnetization directions of the first ferromagnetic layer30and the second ferromagnetic layer70were antiparallel.

RA was obtained by multiplying the resistance Re when the magnetization directions of the first ferromagnetic layer30and the second ferromagnetic layer70were parallel and the area A of the junction formed by microfabrication process.

TABLE 1Composition of first ferromagnetic layer andsecond ferromagnetic layer (molar ratio)Totalcontent ofEvaluationX componentFe and XRACoFeGaGecomponent(Ω · μm2)MR(%)Example 121.030.410.862.300.04525.0Example 221.030.410.872.310.05029.8Example 321.030.411.062.500.10355.6Comparative21.030.410.562.000.01719.3Example 1

Based on the results in Table 1, it was found that the magnetoresistance effect elements of Examples 1 to 3 in which the content α of Fe and the content β of the component X satisfied the scope of the disclosure had a larger value of RA and a larger MR ratio than the magnetoresistance effect element of Comparative Example 1 in which the content α of Fe and the content β of the component X were outside the scope of the disclosure.

Example 4

The magnetoresistance effect element102shown inFIG.3was produced in the same manner as that in Example 1 except that the first NiAl layer40and the second NiAl layer60were not provided.

Example 5 and Comparative Example 2

The magnetoresistance effect element102was produced in the same manner as that in Example 4 except that the compositions of the first ferromagnetic layer30and the second ferromagnetic layer70were changed to the composition shown in the following Table 2. Here, the compositions of the first ferromagnetic layer30and the second ferromagnetic layer70were adjusted by a co-sputtering method using a Ge target.

Evaluation

The MR ratio and RA of the magnetoresistance effect elements produced in Examples 4 and 5 and Comparative Example 2 were measured by the above methods.

The results are shown in the following Table 2.

TABLE 2Composition of first ferromagnetic layer andsecond ferromagnetic layer (molar ratio)Totalcontent ofEvaluationX componentFe and XRACoFeGaGecomponent(Ω · μm2)MR(%)Example 421.030.410.862.300.04420.0Example 521.030.410.962.310.05722.3Comparative21.030.410.562.000.04115.9Example 2

Based on the results in Table 2, it was found that, in the magnetoresistance effect element in which the first NiAl layer40and the second NiAl layer60were not provided, the magnetoresistance effect elements of Examples 4 and 5 in which the content α of Fe and the content β of the component X satisfied the scope of the disclosure had a larger value of RA and a larger MR ratio than the magnetoresistance effect element of Comparative Example 2 in which the content α of Fe and the content β of the component X were outside the scope of the disclosure.

Example 6

The magnetoresistance effect element103shown inFIG.4was produced in the same manner as that in Example 1 except that a CoFe layer having a thickness of 10 nm was provided as a fourth underlayer on the underlayer20, the first ferromagnetic layer30and the second ferromagnetic layer70were a Co2Fe1.02Ga0.40Ge0.22Mn0.76layer, and the thickness of the second ferromagnetic layer70was set to 5 nm.

The first ferromagnetic layer30and the second ferromagnetic layer70were formed by a co-sputtering method using a Co2Fe1Ga0.5Ge0.5alloy target and a Mn target as targets.

Comparative Example 3

The magnetoresistance effect element103was produced in the same manner as that in Example 6 except that the compositions of the first ferromagnetic layer30and the second ferromagnetic layer70were changed to the composition shown in the following Table 3. Here, the compositions of the first ferromagnetic layer30and the second ferromagnetic layer70were adjusted by a co-sputtering method using a Mn target.

Evaluation

The MR ratio and RA of the magnetoresistance effect elements produced in Example 6 and Comparative Example 3 were measured by the above methods. The results are shown in the following Table 3.

TABLE 3Composition of first ferromagnetic layer andsecond ferromagnetic layer (molar ratio)Totalcontent ofEvaluationX componentFe and XRACoFeGaGeMncomponent(Ω · μm2)MR(%)Example 621.020.400.220.762.400.06820.1Comparative21.020.400.220.382.020.04715.9Example 3

Based on the results in Table 3, it was found that, in the magnetoresistance effect element including the fourth underlayer24, the magnetoresistance effect element of Example 6 in which the content α of Fe and the content β of the component X satisfied the scope of the disclosure had a larger value of RA and a larger MR ratio than the magnetoresistance effect element of Comparative Example 3 in which the content α of Fe and the content β of the component X were outside the scope of the disclosure.

FIG.12shows a graph in which the MR ratio (Magnetoresistance ratio) and RA (Resistance Area product) of the magnetoresistance effect elements produced in Examples 1 to 6 and Comparative Examples 1 to 3 were plotted. InFIG.12, the MR ratio and RA of the magnetoresistance effect elements produced in Examples 1 to 6 and Comparative Examples 1 to 3 and the CPP-GMR element described in Non-Patent Document 1 were plotted in the graph shown in FIG. 5 in Non-Patent Document 2.

Based on the graph inFIG.12, it was found that the magnetoresistance effect elements obtained in Examples 1 to 6 had a larger MR ratio and RA than the magnetoresistance effect elements obtained in Comparative Examples 1 to 3. In particular, it was found that the magnetoresistance effect element obtained in Example 3 was able to be operated at a critical current density Jc of 2.5 to 5.0×107A/cm2.

Example 7

A magnetoresistance effect element104shown inFIG.13was produced as follows. The configurations of respective layers of the magnetoresistance effect element104were as follows.

Substrate10: MgO single crystal substrate, thickness of 0.5 mm

Underlayer20:

Second underlayer22: Cr layer, thickness of 10 nm

Third underlayer23: Ag layer, thickness of 100 nm

First insertion layer91: Ni layer, thickness of 0.21 nm

First ferromagnetic layer30

Substrate-side first ferromagnetic layer30B: Co2Fe1.03Ga0.41Ge0.86layer, thickness of 7 nm

Non-magnetic layer-side first ferromagnetic layer30A: Co2Fe1.13Ga0.41Ge0.76layer, thickness of 3 nm

First NiAl layer40: thickness of 0.21 nm

Non-magnetic layer50: Ag layer, thickness of 5 nm

Second NiAl layer60: thickness of 0.21 nm

Second ferromagnetic layer70

Non-magnetic layer-side second ferromagnetic layer70A: Co2Fe1.03Ga0.41Ge0.86layer, thickness of 4 nm

Cap layer-side second ferromagnetic layer70B: Co2Fe1.03Ga0.41Ge0.86layer, thickness of 4 nm

Second insertion layer92: Ni layer, thickness of 0.21 nm

Cap layer80: Ru layer, thickness of 5 nm

In order to improve the flatness of the surface of the substrate10, the substrate10was heated at 600° C. and left for 30 minutes, and then cooled to room temperature. Next, the second underlayer22(Cr layer) was formed on the substrate10by a sputtering method. Next, the third underlayer23(Ag layer) was formed on the second underlayer22by a sputtering method to form the underlayer20. The substrate10on which the underlayer20was formed was heated at 300° C. for 15 minutes and then cooled to room temperature.

After cooling, the first insertion layer91(Ni layer) was formed on the underlayer20formed on the substrate10. The first insertion layer91was formed by a sputtering method.

The substrate-side first ferromagnetic layer30B (Co2Fe1.03Ga0.41Ge0.86layer) having a thickness of 7 nm was formed on the first insertion layer91. The substrate-side first ferromagnetic layer30B was formed by a co-sputtering method using a Co2Fe1Ga0.5Ge0.5alloy target and a Ge target as targets.

The non-magnetic layer-side first ferromagnetic layer30A (Co2Fe1.13Ga0.41Ge0.76layer) having a thickness of 3 nm was formed on the substrate-side first ferromagnetic layer30B. The non-magnetic layer-side first ferromagnetic layer30A was formed by a co-sputtering method using a Co2Fe1Ga0.5Ge0.5alloy target, a Ge target, and an Fe target as targets.

The substrate10on which the first ferromagnetic layer30including the substrate-side first ferromagnetic layer30B and the non-magnetic layer-side first ferromagnetic layer30A were formed was heated at 600° C. for 15 minutes, and then cooled to room temperature.

The first NiAl layer40was formed on the first ferromagnetic layer30by a sputtering method. The first NiAl layer40was formed by a co-sputtering method using a Ni50Al50alloy target and an Al target as targets. In this case, the main composition of the first NiAl layer40was Al.

Next, the non-magnetic layer50(Ag layer) was formed on the first NiAl layer40by a sputtering method.

Next, the second NiAl layer60was formed on the non-magnetic layer50by a sputtering method. The second NiAl layer60was formed by a co-sputtering method using a Ni50Al50alloy target and a Ni target as targets. In this case, the main composition of the second NiAl layer60was Ni.

Then, the non-magnetic layer-side second ferromagnetic layer70A (Co2Fe1.03Ga0.41Ge0.86layer) having a thickness of 4 nm was formed on the second NiAl layer60. The non-magnetic layer-side second ferromagnetic layer70A was formed by a co-sputtering method using a Co2Fe1Ga0.5Ge0.5alloy target and a Ge target as targets. Then, the substrate10on which the non-magnetic layer-side second ferromagnetic layer70A was formed was heated at 500° C. for 15 minutes, and then cooled to room temperature.

The cap layer-side second ferromagnetic layer70B (Co2Fe1.03Ga0.41Ge0.86layer) having a thickness of 4 nm was formed on the non-magnetic layer-side second ferromagnetic layer70A. The cap layer-side second ferromagnetic layer70B was formed by a co-sputtering method using a Co2Fe1Ga0.5Ge0.5alloy target and a Ge target as targets. Then, the substrate10on which the cap layer-side second ferromagnetic layer70B was formed was heated at 450° C. for 15 minutes and then cooled to room temperature.

After cooling, the second insertion layer92(Ni layer) was formed on the second ferromagnetic layer70formed on the substrate10. The second insertion layer92was formed by a sputtering method. Finally, the cap layer80(Ru layer) was formed on the second insertion layer92(Ni layer) by a sputtering method. Thus, the magnetoresistance effect element104shown inFIG.13was produced.

The obtained magnetoresistance effect element104was filled with a resin, the magnetoresistance effect element104was cut in the lamination direction, and the cut surface was polished. Elements Fe, Co, Ga, Ge, Ru, Ag, Ni, and Al were mapped on the cut surface of respective layers from the third underlayer23to the cap layer80using an energy dispersive X-ray spectrometer (EDS).FIG.14shows distribution diagrams of the elements.FIG.14(a)shows a cross-sectional view of the magnetoresistance effect element104,FIG.14(b)shows a distribution diagram of Fe, Co, Ga, Ge, Ru, and Ag on the cut surface of the magnetoresistance effect element104, andFIG.14(c)shows a distribution diagram of Ni and Al on the cut surface of the magnetoresistance effect element104. In the distribution diagrams ofFIGS.14(b) and14(c), the horizontal axis represents a distance in the lamination direction using a point on the third underlayer23as a starting point 0. The vertical axis represents atom %. Based on the distribution diagram of elements inFIG.14, it was confirmed that, from the third underlayer23toward the cap layer80, the layer containing Ag (the third underlayer23), the layer containing Ni (the first insertion layer91), the layer containing Co, Fe, Ga, and Ge (the first ferromagnetic layer30), the NiAl layer containing a larger amount of Al than that of Ni (the first NiAl layer40), the layer containing Ag (the non-magnetic layer50), the NiAl layer containing a larger amount of Ni than that of Al (the second NiAl layer60), the layer containing Co, Fe, Ga, and Ge (the second ferromagnetic layer70), the layer containing Ni (the second insertion layer92), and the layer containing Ru (the cap layer80) were formed. In addition, it was confirmed that the non-magnetic layer-side first ferromagnetic layer30A of the first ferromagnetic layer30had a lower Ge concentration and a higher Fe concentration than the substrate-side first ferromagnetic layer30B. In addition, a tendency of the non-magnetic layer-side first ferromagnetic layer30A of the first ferromagnetic layer30to have a higher Ga concentration near the non-magnetic layer50was observed. In addition, a tendency of the non-magnetic layer-side second ferromagnetic layer70A of the second ferromagnetic layer70to have a higher Ga concentration near the non-magnetic layer50was observed.

In addition, the cut surface of the magnetoresistance effect element104filled with a resin was observed using an annular dark field-scanning transmission electron microscope (ADF-STEM) method, an electron beam diffraction image of a small area of the cut surface was obtained using a convergent-beam electron diffraction (CBED) method, and the crystal structure was identified. The results are shown inFIG.15AandFIG.15B.FIG.15Ashows a STEM image of the cut surface of the magnetoresistance effect element, andFIG.15Bshows electron beam diffraction images of areas 1 to 8 in the TEM image inFIG.15A. The areas 1 to 4 were areas in the first ferromagnetic layer30, the area5was an area in the non-magnetic layer50, and the areas 6 to 8 were areas in the second ferromagnetic layer70. As a result, diffraction spots from the (001) plane derived from the B2 structure was confirmed in the first ferromagnetic layer30and the second ferromagnetic layer70. That is, it was confirmed that the crystal structure had a regularity including the B2 structure (CsCl structure). In addition, in the substrate-side first ferromagnetic layer30B and the non-magnetic layer-side first ferromagnetic layer30A of the first ferromagnetic layer30, in addition to diffraction spots from the (001) plane derived from the B2 structure, diffraction spots from the (111) plane derived from the L21 structure having a higher regularity than the B2 structure were confirmed. That is, it was confirmed that the crystal structure had a regularity including the L21 structure.

EXPLANATION OF REFERENCES

101,102,103,104Magnetoresistance effect element10Substrate20Underlayer21First underlayer22Second underlayer23Third underlayer24Fourth underlayer30First ferromagnetic layer30A Non-magnetic layer-side first ferromagnetic layer30B Substrate-side first ferromagnetic layer40First NiAl layer50Non-magnetic layer60Second NiAl layer70Second ferromagnetic layer70A Non-magnetic layer-side second ferromagnetic layer70B Cap layer-side second ferromagnetic layer80Cap layer91First insertion layer92Second insertion layer201Magnetic recording device202,203Magnetic recording element210Magnetic head220Resistance-measuring device230Power supply240Measurement unit300Spin current magnetization rotating element400Magnetic domain wall-moving type magnetic recording element401First ferromagnetic layer402Second ferromagnetic layer403Non-magnetic layer404First magnetization fixed layer405Second magnetization fixed layer500Magnetic thin wire device510Magnetic recording medium511Magnetic thin wire511A First magnetic domain511B Second magnetic domain512Underlayer513Substrate520Magnetic recording head530Pulse power supply600Magnetic domain wall-moving type spatial optical modulator610First magnetization fixed layer620Second magnetization fixed layer630Light modulation layer631,636Overlapping area632,635Initial magnetic domain area633,634Magnetic domain change areaDW Magnetic domain wall