JP2020127005A - Magnetoresistance effect element - Google Patents

Abstract

To provide a magnetoresistance effect element capable of achieving a high MR ratio.SOLUTION: A magnetoresistance effect element according to the present invention comprises: a first ferromagnetic layer; a second ferromagnetic layer; and a nonmagnetic spacer layer existing between the first ferromagnetic layer and the second ferromagnetic layer. At least one of the first ferromagnetic layer and the second ferromagnetic layer contains a metallic compound having a half-Heusler type crystal structure. The metallic compound contains a functional material as well as X atoms, Y atoms, and Z atoms constituting a unit lattice of the half-heusler type crystal structure. The functional material is smaller than any of the X atoms, the Y atoms, and the Z atoms in atomic number.SELECTED DRAWING: Figure 1

Description

The present invention relates to a magnetoresistive effect element.

A giant magnetoresistive (GMR) element including a multilayer film of a ferromagnetic layer and a nonmagnetic layer, and a tunnel magnetoresistive (TMR) element using an insulating layer (tunnel barrier layer, barrier layer) for the nonmagnetic layer are known. There is. GMR elements and TMR elements have been attracting attention as elements for magnetic sensors, magnetic heads, high frequency components, and magnetic random access memories (MRAM). The magnetoresistive effect element has a magnetoresistive effect ratio (MR ratio) as one of the figures of merit, and development is underway to increase the magnetoresistive effect ratio (MR ratio). It is said that the MR ratio is increased by using a high spin polarized material for the ferromagnetic layer, and the Heusler alloy is an example of the high spin polarized material.

In Non-Patent Document [1], a NiMnSb/Ag/NiMnSb-based GMR in which NiMnSb having a half-Heusler crystal structure, which is one of Heusler alloys, is used as a ferromagnetic layer and Ag is used as a nonmagnetic layer A device is disclosed.

Scientific Reports 5. 18387 (2015)

The MR ratio of the magnetoresistive element described in Non-Patent Document [1] is at most 8% at room temperature, which is not as high as expected. One of the reasons for this is considered to be that the half-Heusler crystal structure has a vacancy. The vacancies are considered to cause the distortion of the crystal structure, and the distortion of the crystal structure lowers the MR ratio.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a magnetoresistive effect element capable of improving the MR ratio.

As a result of intensive studies, the present inventors have found that the addition of a predetermined element to the material forming the ferromagnetic layer stabilizes the crystal structure of the ferromagnetic layer and improves the MR ratio of the magnetoresistive element. .. That is, the present invention provides the following means in order to solve the above problems.

(1) The magnetoresistive effect element according to the first aspect includes a first ferromagnetic layer, a second ferromagnetic layer, and between the first ferromagnetic layer and the second ferromagnetic layer. A certain non-magnetic spacer layer, wherein at least one of the first ferromagnetic layer and the second ferromagnetic layer includes a metal compound having a half-Heusler crystal structure, the metal compound is functional. A material and an X atom, a Y atom and a Z atom forming a unit cell of the half-Heusler type crystal structure, wherein the functional material is an atom from any atom of the X atom, the Y atom and the Z atom. The number is small. By satisfying the configuration, the metal compound having a half-Heusler crystal structure has a stable crystal structure while maintaining a high spin polarization rate. As a result, the MR ratio of the magnetoresistive effect element is improved.

(2) In the magnetoresistive effect element according to the above aspect, the functional material may be at least one atom selected from the group consisting of B, C, N, and F. By satisfying the structure, the crystal structure becomes more stable. As a result, the MR ratio of the magnetoresistive effect element is improved.

(3) In the magnetoresistive effect element according to the above aspect, the composition ratio of the functional material in the metal compound may be 0.1 at% (0.1 mol%) or more and 7 at% (7 mol%) or less. By satisfying the structure, the crystal structure becomes more stable. As a result, the MR ratio of the magnetoresistive effect element is improved.

(4) In the magnetoresistive effect element according to the above aspect, the functional material may be boron, and the composition ratio of the functional material in the metal compound may be 0.1 at% or more and 9.8 at% or less.

(5) In the magnetoresistive effect element according to the above aspect, the functional material may be carbon, and a composition ratio of the functional material in the metal compound may be 0.11 at% or more and 8.8 at% or less.

(6) In the magnetoresistive effect element according to the above aspect, the functional material may be nitrogen, and the composition ratio of the functional material in the metal compound may be 0.09 at% or more and 7.2 at% or less.

(7) In the magnetoresistive effect element according to the above aspect, the functional material may be fluorine, and the composition ratio of the functional material in the metal compound may be 0.13 at% or more and 7.2 at% or less.

(8) In the magnetoresistive effect element according to the above aspect, the X atom is selected from the group consisting of Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Ag, Cd, Ir, Pt, and Au 1. At least one atom, and the Y atom is selected from the group consisting of Ti, V, Cr, Mn, Y, Zr, Nb, Hf, Ta, Gd, Tb, Dy, Hd, Er, Fe, Tm, Yb and Lu. One or more atoms selected, wherein the Z atom is one or more selected from the group consisting of Al, Si, Ga, Ge, As, In, Sn, Sb, Tl, Pd, Bi, Se, Te. May be an atom of. When the composition is satisfied, the crystal structure is easily stabilized in the composition that satisfies the composition of the Heusler alloy, and the production is facilitated.

(9) In the magnetoresistive effect element according to the above aspect, the X atom is at least one atom selected from Ni, Pd, Pt, Co, and Rh, and the Y atom is selected from Mn, Cr, Fe, and V. The Z atom may be one or more atoms selected from the group consisting of, and the Z atom may be one or more atoms selected from the group consisting of Se, Te, and Sb. When the structure is satisfied, the spin polarization ratio of the ferromagnetic Heusler alloy contained in the first ferromagnetic layer and/or the second ferromagnetic layer becomes high, and the MR ratio of the magnetoresistive effect element becomes large.

(10) In the magnetoresistive effect element according to the above aspect, the metal compound may have a crystal structure of a C1b structure or a B2 structure. When the structure is satisfied, the spin polarization ratio of the ferromagnetic Heusler alloy contained in the first ferromagnetic layer and/or the second ferromagnetic layer becomes high, and the MR ratio of the magnetoresistive effect element becomes large.

(11) In the magnetoresistive effect element according to the above aspect, one of the first ferromagnetic layer and the second ferromagnetic layer includes a metal compound having a half-Heusler crystal structure, and the other is a full Heusler type. The metal compound having a crystal structure, and the metal compound having a full-Heusler crystal structure may include the X atom, the Y atom and the Z atom. If the structure is satisfied, the spin polarization of at least one of the first ferromagnetic layer and the second ferromagnetic layer can be further increased, and the MR ratio of the magnetoresistive effect element is increased.

(12) In the magnetoresistive effect element according to the above aspect, the metal compound having the full-Heusler crystal structure is represented by a composition formula Co ₂ L _α M _β , and the L atom is at least one of Mn and Fe. And α satisfies 0.7<α<1.6, the M atom includes at least one of Al, Si, Ge, and Ga, and β satisfies 0.65<β<1.35. You may meet. When the structure is satisfied, the spin polarization of at least one of the first ferromagnetic layer and the second ferromagnetic layer is further increased, and the MR ratio of the magnetoresistive effect element is increased.

(13) In the magnetoresistive effect element according to the above aspect, an insertion layer is provided between at least one of the first ferromagnetic layer and the second ferromagnetic layer and the nonmagnetic spacer. However, the insertion layer may include Co, Fe, or a CoFe alloy. When the structure is satisfied, the insertion layer eliminates the mismatch at the interface between the ferromagnetic layer and the nonmagnetic spacer layer, and the magnetization stability of the ferromagnetic layer is improved. As a result, the temperature dependence of the MR ratio of the magnetoresistive effect element is reduced.

(14) In the magnetoresistive effect element according to the above aspect, the thickness of the insertion layer may be 0.2 nm or more and 1.2 nm or less. When the structure is satisfied, a high MR ratio can be obtained while maintaining the temperature dependence of the MR ratio.

(15) In the magnetoresistive effect element according to the above aspect, the nonmagnetic spacer layer may be made of metal. When the structure is satisfied, the magnetoresistive effect element has low RA and high MR ratio.

(16) In the magnetoresistive effect element according to the above aspect, the nonmagnetic spacer layer may be made of Ag or an Ag alloy. When the structure is satisfied, the magnetoresistive effect element has a low RA and a higher MR ratio.

According to the present invention, the MR ratio of the magnetoresistive effect element can be improved.

It is a cross-sectional schematic diagram of the magnetoresistive effect element concerning this embodiment. It is a schematic diagram of the crystal structure of the Heusler alloy concerning this embodiment. It is a schematic diagram of the magnetoresistive device which has the magnetoresistive effect element which concerns on this embodiment.

Hereinafter, the present invention will be described in detail with reference to the drawings. In the drawings used in the following description, in order to make the features of the present invention easy to understand, there are cases in which the features that are the features are enlarged for convenience, and the dimensional ratios of the components may be different from the actual ones. is there. The materials, dimensions, and the like exemplified in the following description are examples, and the present invention is not limited thereto and can be appropriately modified and implemented within the scope of the invention.

"Magnetic resistance element"
FIG. 1 is a schematic sectional view of the magnetoresistive effect element according to the present embodiment. The magnetoresistive effect element 10 shown in FIG. 1 includes a first ferromagnetic layer 1, a second ferromagnetic layer 2, and a nonmagnetic spacer layer 3. In addition to these layers, the magnetoresistive effect element 10 may have a cap layer, a base layer and the like. Hereinafter, the direction perpendicular to the plane in which the first ferromagnetic layer 1 spreads may be referred to as the stacking direction.

(First ferromagnetic layer, second ferromagnetic layer)
The first ferromagnetic layer 1 and the second ferromagnetic layer 2 each include a ferromagnetic material and have magnetization. The magnetoresistive effect element 10 outputs the relative angle change of these magnetizations as a resistance value change. For example, when the magnetization direction of the second ferromagnetic layer 2 is fixed in one direction and the magnetization direction of the first ferromagnetic layer 1 is variable with respect to the magnetization direction of the second ferromagnetic layer 2, The magnetization direction of the first ferromagnetic layer 1 changes with respect to the magnetization direction of the second ferromagnetic layer 2. As a result, the relative angle between the two magnetizations changes, and the resistance value of the magnetoresistive effect element 10 changes. The thickness of the first ferromagnetic layer 1 is, for example, 1 nm to 20 nm, and the thickness of the second ferromagnetic layer 2 is, for example, 1 nm to 20 nm. A layer whose magnetization direction is fixed is generally called a fixed layer, and a layer whose magnetization direction is variable is generally called a free layer. The first ferromagnetic layer 1 and the second ferromagnetic layer 2 may each be composed of a plurality of layers. Hereinafter, the case where the first ferromagnetic layer 1 is a free layer and the second ferromagnetic layer is a fixed layer will be described as an example.

At least one of the first ferromagnetic layer 1 and the second ferromagnetic layer 2 contains a ferromagnetic Heusler alloy, and preferably consists essentially of a ferromagnetic Heusler alloy. The ferromagnetic Heusler alloy has a half Heusler type crystal structure whose composition formula is represented by XYZ in the stoichiometric composition and a full Heusler type crystal structure whose composition formula (chemical formula) is represented by X ₂ YZ in the stoichiometric composition. There is. At least one of the first ferromagnetic layer 1 and the second ferromagnetic layer 2 contains a metal compound having a half-Heusler crystal structure. At least one of the first ferromagnetic layer 1 and the second ferromagnetic layer 2 is made of, for example, a metal compound having a half-Heusler crystal structure. The metal compound is, for example, a metal compound layer spreading in a plane intersecting the stacking direction. The metal compound contains an X atom, a Y atom, a Z atom and a functional material. The X atom, the Y atom, and the Z atom are each atom that forms the unit cell of the half-Heusler crystal structure, as represented by the composition formula. The functional material is an atom having an atomic number smaller than that of any of the X atom, the Y atom, and the Z atom. The functional material is not limited to one type of atom, and may be two or more types. The functional material is, for example, Li, Be, B, C, N, O, F, Na, Mg. The functional material is small in size and mainly intersperses between the lattices of the half-Heusler crystal structure. The functional material penetrates into the vacancies without significantly distorting the half-Heusler crystal structure, and thus stabilizes the half-Heusler crystal structure. As a result, the magnetoresistive effect of the magnetoresistive effect element 10 becomes large.

Here, “in the stoichiometric composition, represented by the composition formula XYZ or X ₂ YZ” means that the compound is not limited to the stoichiometric composition and may be a non-stoichiometric composition. That is, when the composition formula is XYZ, it is not necessary that the ratio of X atoms, Y atoms and Z atoms is exactly 1:1:1. When the composition formula is X ₂ YZ, X atoms, Y atoms and Z atoms are It is not necessary that the ratio of is exactly 2:1:1.

The functional material may be one or more selected from the group consisting of B, C, N and F. These atoms stabilize the half-Heusler crystal structure, and further stabilize the crystal structure of at least one of the first ferromagnetic layer 1 and the second ferromagnetic layer 2.

The composition ratio of the functional material according to the definition below may be 0.1 at% or more and 7 at% or less.

When the functional material is boron (B), the composition ratio of the functional material in the metal compound is, for example, 0.1 at% or more and 9.8 at% or less, preferably 0.6 at% or more and 9.8 at% or less, More preferably, it is 3.9 at% or more and 7.3 at% or less.

When the functional material is carbon (C), the composition ratio of the functional material in the metal compound is, for example, 0.11 at% or more and 8.8 at% or less, preferably 4.2 at% or more and 8.8 at% or less, More preferably, it is 5.6 at% or more and 6.3 at% or less.

When the functional material is nitrogen (N), the composition ratio of the functional material in the metal compound is, for example, 0.09 at% or more and 7.2 at% or less, preferably 3.2 at% or more and 7.2 at% or less, More preferably, it is 4.7 at% or more and 5.7 at% or less.

When the functional material is fluorine (F), the composition ratio of the functional material in the metal compound is, for example, 0.13 at% or more and 7.2 at% or less, preferably 0.9 at% or more and 7.2 at% or less, More preferably, it is 3.7 at% or more and 4.7 at% or less.

The X atom forming the unit cell of the half-Heusler crystal structure is, for example, one selected from the group consisting of Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Ag, Cd, Ir, Pt, and Au. These are the atoms. The Y atom forming the unit cell of the half-Heusler crystal structure is, for example, Ti, V, Cr, Mn, Y, Zr, Nb, Hf, Ta. It is at least one atom selected from the group consisting of Gd, Tb, Dy, Hd, Er, Fe, Tm, Yb, and Lu. However, the case where both X and Y atoms are Fe atoms is excluded. The Z atom forming the unit cell of the half-Heusler crystal structure is, for example, one selected from the group consisting of Al, Si, Ga, Ge, As, In, Sn, Sb, Tl, Pd, Bi, Se, and Te. These are the above elements.

The X atom is preferably at least one atom selected from the group consisting of Ni, Pd, Pt, Co and Rh. The Y atom is preferably one or more atoms selected from the group consisting of Mn, Cr, Fe and V. The Z atom is preferably at least one atom selected from the group consisting of Se, Te and Sb. The half-Heusler type crystal structure (XYZ) metal compound is, for example, NiMnSe, NiMnTe, NiMnSb, PtMnSb, PdMnSb, CoFeSb, NiFeSb, RhMnSb, CoMnSb, IrMnSb, NiCrSb.

Half-Heusler alloy, for example, A2 structure, B2 structure, comprising any of the crystalline structure of C1 _b structure. Here, “including any crystal structure” is meant to include, for example, a case where a part of the C1 _b structure has an A2 structure or a B2 structure.

Here, the crystal structures of the half Heusler alloy and the full Heusler alloy described later will be described with reference to FIG.

FIG. 2A, FIG. 2B, and FIG. 2C are schematic diagrams of crystal structures in which the compound represented by the composition formula of X ₂ YZ (Full Heusler alloy) is easily selected. FIG. 2D, FIG. 2E, and FIG. 2F are schematic views of crystal structures in which the compound represented by the composition formula of XYZ (half Heusler alloy) can be easily selected.

2A shows an L2 ₁ structure, and FIG. 2D shows a C1 _b structure. In these structures, the X atom, the Y atom, and the Z atom are contained at predetermined sites. The unit cell of the L2 ₁ structure is composed of four face-centered cubic lattices (fcc), and the structure in which one X atom is removed is the C1 _b structure. Therefore, the C1 _b structure has vacancies as compared with the L2 ₁ structure.

FIG. 2B shows the B2 structure derived from the L2 ₁ structure, and FIG. 2E shows the B2 structure derived from the C1 _b structure. In these crystal structures, the X atom is contained in a predetermined site, but the Y atom and the Z atom are not contained in the most stable sites, and are randomly housed in each site. That is, the probability that the Y atom and the Z atom are accommodated in the specific site is disturbed. 2(c) shows the A2 structure derived from the L2 ₁ structure, and FIG. 2(f) shows the A2 structure derived from the C1 _b structure. In these crystal structures, the X atom, the Y atom, and the Z atom are not contained in the most stabilizing sites, but are randomly housed in each site. That is, the probability that the X atom, the Y atom, and the Z atom are accommodated in the specific site is disturbed. In the compound represented by the composition formula of X ₂ YZ, the crystallinity is high in the order of L2 ₁ structure>B2 structure>A2 structure. In the compound represented by the composition formula of XYZ, the crystallinity is high in the order of C1 _b structure>B2 structure>A2 structure. The crystal structure of the half-Heusler alloy is preferably C1 _b structure or B2 structure.

Further, one of the first ferromagnetic layer 1 and the second ferromagnetic layer 2 contains a metal compound having a half-Heusler crystal structure, and the other one is a full Heusler crystal whose composition formula is represented by X ₂ YZ. You may include the metal compound which has a structure. One of the first ferromagnetic layer 1 and the second ferromagnetic layer 2 may be made of a metal compound having a full Heusler crystal structure.

The X atoms, Y atoms, and Z atoms forming the unit lattice of the full Heusler type crystal structure are the same as the X atoms, Y atoms, and Z atoms forming the unit lattice of the half Heusler type crystal structure. The X atom is, for example, at least one atom selected from the group consisting of Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Ag, Cd, Ir, Pt, and Au. Y atom is Ti, V, Cr, Mn, Y, Zr, Nb, Hf, Ta. Gd, Tb, Dy, Hd, Er, Fe, Tm, Yb, Lu is one or more kinds of atoms, and Z atom is Al, Si, Ga, Ge, As, In, Sn, Sb, Tl, It is at least one atom selected from Pd and Bi. Examples of the metal compound having a full Heusler crystal structure (X ₂ YZ) include Co ₂ FeSi, Co ₂ FeGe, Co ₂ FeGa, Co ₂ MnSi, Co ₂ Mn _1-a Fe _a Al _b Si _1-b , and Co _2. FeGe _1-c Ga c, and the like.

The metal compound having the full Heusler crystal structure (X ₂ YZ) may be, for example, Co ₂ L _α M _β . The L atom is one aspect of the above Y atom, and is, for example, at least one atom of Mn and Fe. The M atom is one aspect of the Z atom described above, and is one or more atoms selected from the group consisting of Si, Al, Ga, and Ge. In addition, Co ₂ L _α M _β satisfies 0.7<α<1.6 and 0.65<β<1.35.

The Heusler alloy represented by Co ₂ L _α M _β has a high spin polarizability. Therefore, the magnetoresistive effect element 10 exhibits a large magnetoresistive effect. Further, when the conditions of 0.7<α<1.6 and 0.65<β<1.35 are satisfied, the lattice constant of the Heusler alloy has a small difference from the lattice constant when the stoichiometric composition is satisfied. Therefore, the lattice mismatch between the first ferromagnetic layer 1 and/or the second ferromagnetic layer 2 and the nonmagnetic spacer layer 3 becomes small. As a result, the magnetoresistive effect element exhibits a high MR ratio. However, the Heusler alloy does not necessarily have to satisfy the conditions of 0.7<α<1.6 and 0.65<β<1.35.

The Heusler alloy having a full Heusler crystal structure includes a crystal structure having an A2 structure, a B2 structure, or an L2 ₁ structure. The B2 structure Heusler alloy exhibits higher spin polarizability than the A2 structure Heusler alloy. The Heusler alloy having the L2 ₁ structure exhibits higher spin polarizability than the Heusler alloy having the B2 structure.

Further, at least one of the first ferromagnetic layer 1 and the second ferromagnetic layer 2 may include a ferromagnetic material that is not a Heusler alloy. The ferromagnetic material is, for example, a soft magnetic material. The ferromagnetic material is, for example, a ferromagnetic layer extending in a plane intersecting the stacking direction. The ferromagnetic material is, 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, and at least one or more of these metals and B, C and N. Alloys containing the elements of Specifically, the ferromagnetic material is, for example, Co-Fe, Co-Fe-B, or Ni-Fe.

By stacking the above-mentioned Heusler alloy and Co, Fe, or CoFe alloy, the stability of the magnetization of the Heusler alloy can be increased. Further, an insertion layer may be provided between the first ferromagnetic layer 1 and the nonmagnetic spacer layer 3 and/or between the second ferromagnetic layer 2 and the nonmagnetic spacer layer 3. The insertion layer contains, for example, Co, Fe, or a CoFe alloy. The insertion layer may be made of Co, Fe, or a CoFe alloy, for example. The insertion layer is preferably Co _x Fe _1-x (0.5≦x≦0.8). The thickness of the insertion layer is preferably 0.2 nm or more and 1.2 nm or less. The insertion layer enhances the lattice matching between the first ferromagnetic layer 1 and the nonmagnetic spacer layer 3 and/or between the second ferromagnetic layer 2 and the nonmagnetic spacer layer 3. Moreover, since the insertion layer is thin, spin scattering due to the insertion layer can be suppressed.

In order to make the second ferromagnetic layer 2 a fixed layer, the coercive force of the second ferromagnetic layer 2 is made larger than the coercive force of the first ferromagnetic layer 1. When an antiferromagnetic material such as IrMn or PtMn is adjacent to the second ferromagnetic layer 2, the coercive force of the second ferromagnetic layer 2 increases. Further, in order to prevent the leakage magnetic field of the second ferromagnetic layer 2 from affecting the first ferromagnetic layer 1, the second ferromagnetic layer 2 may have a structure of synthetic ferromagnetic coupling.

(Non-magnetic spacer layer)
The nonmagnetic spacer layer 3 is made of, for example, an insulator. In this case, the nonmagnetic spacer layer 3 becomes a tunnel barrier layer. The insulator used for the nonmagnetic spacer layer 3 is, for example, TiO ₂ , HfO ₂ , Al ₂ O ₃ , SiO ₂ , MgO, ZnAl ₂ O ₄ , γ-Al ₂ O ₃ , MgGa ₂ O ₄ , MgAl ₂ O. It is ₄ mag. Further, the insulator may have a mixed crystal structure containing any one of the above as a main component. In addition to these, the insulator may be a material in which a part of Al, Si, Mg is replaced with Zn, Be or the like. When MgO or MgAl ₂ O ₄ is used among these materials, the nonmagnetic spacer layer 3 exhibits a coherent tunnel effect, and the magnetoresistive effect element 10 exhibits a high MR ratio. The nonmagnetic spacer layer 3 may be made of metal, for example. In this case, the metal is, for example, an alloy containing at least one metal element of Cu, Au, Ag, Cr, V, Al, W, and Pt. Furthermore, the nonmagnetic spacer layer 3 may be made of a semiconductor. In this case, the semiconductor is, for example, Si, Ge, ZnO, GaO, InSnO, InZnO, CuInSe ₂ , CuGaSe ₂ , Cu(In,Ga)Se _2, or the like.

In order to reduce RA (area resistance) of the magnetoresistive effect element 10 and obtain a high MR ratio, the nonmagnetic spacer layer 3 is preferably made of metal.

The nonmagnetic spacer layer 3 may be Ag or Ag alloy. When the nonmagnetic spacer layer 3 is Ag or an Ag alloy, the Fermi surface of the ferromagnetic layer and the Fermi surface of the nonmagnetic spacer layer are well matched, and the magnetoresistive effect element exhibits a higher MR ratio. The Ag alloy is, for example, Ag _1-x Sn _x , Ag _1-x Mg _x , Ag _1-x Zn _x , Ag _1-x Al _x, or the like. Here, the range of x is 0<x<0.25, for example. When the range of x is in this range, the lattice mismatch between the ferromagnetic layer and the nonmagnetic spacer layer 3 becomes small, and the matching of the Fermi surface of each layer becomes good.

When the nonmagnetic spacer layer 3 is made of an insulating material, its thickness is preferably 0.4 nm or more and 3 nm or less. When the non-magnetic spacer layer 3 is made of a metal, its thickness is preferably 1 nm or more and 10 nm or less. When the nonmagnetic spacer layer 3 is made of a semiconductor, its film thickness is preferably 0.6 nm or more and 5 nm or less. This increases the MR ratio of the magnetoresistive effect element.

(Element shape and dimensions)
The laminated body composed of the first ferromagnetic layer 1, the non-magnetic spacer layer 3 and the second ferromagnetic layer 2 constituting the magnetoresistive effect element 10 is formed by known photolithography (electron beam lithography) and dry etching (Ar). It is finely processed into a columnar shape by ion milling or the like). The shape of the laminated body in plan view can be various shapes such as a circle, a quadrangle, a triangle, and a polygon, but a circular shape is preferable in terms of symmetry. That is, it is preferable that the laminate has a columnar shape.

When the laminate has a columnar shape, the diameter in plan view is preferably 80 nm or less, more preferably 60 nm or less, and further preferably 30 nm or less. When the diameter is 80 nm or less, it becomes difficult to form a domain structure in the ferromagnetism, and it becomes unnecessary to consider a component different from spin polarization in the ferromagnetic layer. Further, when the thickness is 30 nm or less, the ferromagnetic layer has a single domain structure, and the magnetization reversal speed and probability are improved. In addition, there is a strong demand for reduction in resistance of miniaturized magnetoresistive elements.

(Other)
In the present embodiment, as the magnetoresistive effect element 10, an example of the top pin structure in which the first ferromagnetic layer 1 is a free layer and the second ferromagnetic layer 2 is a fixed layer is given. However, the structure of the magnetoresistive effect element 10 is not limited to this case, and may be a bottom pin structure.

As described above, the magnetoresistive effect element 10 according to the present embodiment contains a half-Heusler type metal compound, and this metal compound contains a predetermined functional material. The functional material enhances the stability of the half-Heusler crystal structure by penetrating the vacancies. Further, since the functional material does not significantly distort the crystal structure of the half-Heusler crystal structure, it is possible to maintain the high spin polarization rate originally exhibited by the metal compound of the half-Heusler crystal structure. As a result, the MR ratio of the magnetoresistive effect element 10 according to the present embodiment is improved as compared with the case where the functional material is not included.

The magnetoresistive effect element according to the present embodiment can be used as a memory such as a magnetic sensor or MRAM.

"Method for manufacturing magnetoresistive effect element"
Next, a method of manufacturing the magnetoresistive effect element will be described.
The method of manufacturing a magnetoresistive effect element according to the present embodiment includes a step of stacking a first ferromagnetic layer 1, a nonmagnetic spacer layer 3, and a second ferromagnetic layer 2. These layers can be formed by a known method such as a sputtering method, a vapor deposition method, a laser ablation method, or a molecular beam epitaxial (MBE) method.
(Evaluation method)

Further, the MR ratio of the manufactured magnetoresistive effect element 10 was measured. FIG. 3 is a schematic view of the magnetoresistive effect device used for the measurement of the MR ratio as seen in a plan view from the stacking direction. The magnetoresistive effect element 10 is provided at a position where the first wiring 15 and the second wiring 11 intersect. The magnetoresistive effect element 10 has a cylindrical shape with a diameter of 80 nm. An electrode 12 is provided on the first wiring 15, and the electrode 12 is connected to a power source 13 and a voltmeter 14. By applying a voltage from the power supply 13, a current flows in the stacking direction of the magnetoresistive effect element 10. At this time, the potential difference of the magnetoresistive effect element 10 is monitored by the voltmeter 14. Then, a resistance change of the magnetoresistive effect element is observed by applying a current or a voltage to the magnetoresistive effect element 10 while sweeping the magnetic field from the outside.

The MR ratio is generally represented by the following formula.
MR ratio _{(%) = (R AP -R} P) / R P × 100
R _P is a resistance when the magnetization directions of the first ferromagnetic layer 1 and the second ferromagnetic layer 2 are parallel, and R _AP is the magnetization direction of the first ferromagnetic layer 1 and the second ferromagnetic layer 2. This is the resistance when antiparallel.

Composition analysis of the first ferromagnetic layer 1 and the second ferromagnetic layer 2 was performed by energy dispersive X-ray analysis (EDS) in a transmission electron microscope (TEM) after preparing a thin sample using a focused ion beam. .. For example, when the functional material is B, the composition ratio of B is defined by atomic composition percentage (at %), and 100דB atom number”/(“X atom number”+“Y atom number”+“Z atom number” "+"B atom number"). The analysis method is not limited to this, and secondary ion mass spectrometry (SIMS), atom probe method, electron energy loss spectroscopy (EELS) can also be used.

The TEM-EDS analysis result was a value obtained by subtracting the background signal of the measurement element.

(Example 1-1)
The magnetoresistive effect element 10 shown in FIG. 1 was produced on a MgO(001) substrate. First, 20 nm of Cr and 40 nm of Ag were laminated in this order on the substrate as a base layer (also serving as a first wiring 15 described later), and NiMnSbB was laminated to 30 nm as the first ferromagnetic layer 1. Then, Ag was laminated on the first ferromagnetic layer 1 as the nonmagnetic spacer layer 3 to a thickness of 5 nm. Next, on the non-magnetic spacer layer 3, NiMnSbB is stacked to a thickness of 6 nm as the second ferromagnetic layer 2, and Ru is deposited to a thickness of 20 nm as a cap layer (also serving as the second wiring 11 described later) to form the magnetoresistive element 10. Obtained. Each layer on the substrate was manufactured by a sputtering method, and Ar was used as a sputtering gas. The NiMnSbB film was formed by simultaneous sputtering of a NiMnSb target and a B target. After forming this magnetoresistive effect element, heat treatment was performed in a magnetic field to impart uniaxial magnetic anisotropy to the first ferromagnetic layer 1 and the second ferromagnetic layer 2. The heat treatment temperature in this heat treatment in a magnetic field was 300° C., and the strength of the applied magnetic field was 5 kOe (399 kA/m).

Using the method described above, the composition ratio of B contained in the first ferromagnetic layer 1 and the second ferromagnetic layer 2 and the MR ratio of the magnetoresistive effect element were measured.

The composition ratio of B contained in the first ferromagnetic layer 1 and the second ferromagnetic layer 2 was 0.1 at %. Here, the composition ratio of B was measured by preparing a thin sample with a focused ion beam and performing energy dispersive X-ray analysis (EDS) with a transmission electron microscope (TEM).

(Examples 1-2 to 1-7)
Magnetoresistance under the same conditions as in Example 1-1, except that the conditions for simultaneous sputtering of the NiMnSb target and the B target in Example 1-1 were changed to change the composition ratio of B contained in NiMnSb. The effect element 10 was produced. Further, the composition ratio of B and the MR ratio were measured in the same procedure as in Example 1-1. The results are shown in Table 1.

(Comparative Example 1-1)
Example 1-1 except that the B target was not used and only the NiMnSb target was used to form the first ferromagnetic layer 1 and the second ferromagnetic layer 2 with respect to the manufacturing conditions of Example 1-1. The magnetoresistive effect element 10 was manufactured under the same conditions as described above. Further, the composition ratio of B and the MR ratio were measured in the same procedure as in Example 1-1. The results are shown in Table 1. The composition ratio of B in Comparative Example 1-1 was below the detection limit (0.01 at% or less).

(Examples 2-1 to 2-7)
A magnetoresistive effect element 10 was produced under the same conditions as in Example 1-1, except that the first ferromagnetic layer 1 and the second ferromagnetic layer 2 were produced by co-sputtering a NiMnSb target and a C target.

(Examples 3-1 to 3-7)
A magnetoresistive effect element 10 was prepared under the same conditions as in Example 1-1, except that the first ferromagnetic layer 1 and the second ferromagnetic layer 2 were formed by sputtering a NiMnSb target with a mixed gas of Ar and nitrogen. It was made. The composition ratio of nitrogen was controlled by the partial pressure ratio of Ar and nitrogen.

(Examples 4-1 to 4-7)
The magnetoresistive effect element 10 was manufactured under the same conditions as in Example 1-1, except that the first ferromagnetic layer 1 and the second ferromagnetic layer 2 were formed by sputtering a NiMnSb target with a mixed gas of Ar and fluorine. It was made. The composition ratio of fluorine was controlled by the partial pressure ratio of Ar and fluorine.

1 first ferromagnetic layer;
2 second ferromagnetic layer;
3 tunnel barrier layer;
10 magnetoresistive effect element;
11 second wiring;
12 electrodes;
13 power supply;
14 Voltmeter;
15 First wiring;
20 Magnetoresistive device

Claims (16)

A first ferromagnetic layer,
A second ferromagnetic layer,
A non-magnetic spacer layer between the first ferromagnetic layer and the second ferromagnetic layer,
At least one of the first ferromagnetic layer and the second ferromagnetic layer contains a metal compound having a half-Heusler crystal structure,
The metal compound includes a functional material and X atoms, Y atoms and Z atoms forming a unit cell of the half-Heusler crystal structure,
The magnetoresistive effect element, wherein the functional material has an atomic number smaller than that of any of the X atom, the Y atom, and the Z atom. The magnetoresistive effect element according to claim 1, wherein the functional material is at least one atom selected from the group consisting of B, C, N, and F. The magnetoresistive effect element according to claim 1, wherein the composition ratio of the functional material in the metal compound is 0.1 at% or more and 7 at% or less. The functional material is boron,
The magnetoresistive effect element according to claim 1, wherein the composition ratio of the functional material in the metal compound is 0.1 at% or more and 9.8 at% or less. The functional material is carbon,
The magnetoresistive effect element according to claim 1, wherein a composition ratio of the functional material in the metal compound is 0.11 at% or more and 8.8 at% or less. The functional material is nitrogen,
The magnetoresistive effect element according to claim 1, wherein the composition ratio of the functional material in the metal compound is 0.09 at% or more and 7.2 at% or less. The functional material is fluorine,
The magnetoresistive effect element according to claim 1, wherein the composition ratio of the functional material in the metal compound is 0.13 at% or more and 7.2 at% or less. The X atom is at least one atom selected from the group consisting of Fe, Co, Ni, Cu, Zn, Ru, Rh, Pd, Ag, Cd, Ir, Pt, and Au,
The Y atom is one or more selected from the group consisting of Ti, V, Cr, Mn, Y, Zr, Nb, Hf, Ta, Gd, Tb, Dy, Hd, Er, Fe, Tm, Yb, and Lu. Is an atom of
The Z atom is one or more atoms selected from the group consisting of Al, Si, Ga, Ge, As, In, Sn, Sb, Tl, Pd, Bi, Se, Te. 13. The magnetoresistive effect element according to any one of 1. The X atom is at least one atom selected from the group consisting of Ni, Pd, Pt, Co and Rh,
The Y atom is at least one atom selected from the group consisting of Mn, Cr, Fe and V,
The magnetoresistive effect element according to claim 8, wherein the Z atom is at least one atom selected from the group consisting of Se, Te, and Sb. The magnetoresistive effect element according to claim 1, wherein the metal compound has a crystal structure of a C1 _b structure or a B2 structure. One of the first ferromagnetic layer and the second ferromagnetic layer contains a metal compound having a half-Heusler crystal structure, the other contains a metal compound having a full Heusler crystal structure,
The magnetoresistive effect element according to any one of claims 1 to 10, wherein the metal compound having a full-Heusler crystal structure contains the X atom, the Y atom, and the Z atom. The metal compound having the full-Heusler crystal structure is represented by the composition formula Co ₂ L _α M _β ,
The L atom includes at least one atom of Mn and Fe,
The M atom includes at least one atom selected from Al, Si, Ge, and Ga,
The above α satisfies 0.7<α<1.6,
The magnetoresistive effect element according to claim 11, wherein the β satisfies 0.65<β<1.35. An insertion layer is provided between at least one of the first ferromagnetic layer and the second ferromagnetic layer, and the nonmagnetic spacer layer,
13. The magnetoresistive effect element according to claim 1, wherein the insertion layer has Co, Fe, or a CoFe alloy. The magnetoresistive effect element according to claim 13, wherein the film thickness of the insertion layer is 0.2 nm or more and 1.2 nm or less. The magnetoresistive effect element according to claim 1, wherein the nonmagnetic spacer layer is made of metal. The magnetoresistive effect element according to claim 15, wherein the non-magnetic spacer layer is made of Ag or an Ag alloy.

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