JPWO2011122078A1 - Magnetoresistive element, magnetic disk device, and magnetoresistive storage device - Google Patents

Abstract

A magnetoresistive element having an appropriate sheet resistance and a high magnetoresistance ratio is realized. Therefore, a semimetal having at least one of the L21 structure, the B2 structure, the A2 structure, the C1b structure, or the B1 structure is used for the intermediate layer between the fixed layer and the free layer. Thereby, a uniform intermediate layer having excellent lattice matching with the fixed layer and the free layer can be formed. Further, the electrons that can be transmitted through the intermediate layer are controlled by the laminated structure and doping of the semimetal layer. Thereby, a high magnetoresistance ratio and a high area resistance compared to metal can be realized.

Description

  The present invention relates to a magnetoresistive element having an appropriate sheet resistance and a high magnetoresistance ratio. The magnetic device according to the present invention includes, for example, a magnetoresistive element as a reproducing head, a magnetic disk device applied to the reproducing head, a magnetoresistive memory device using the magnetoresistive element as a memory element, and a magnetic orientation sensor equipped with the magnetoresistive element including.

  As a reproducing head of a hard disk drive (HDD) device, a giant magnetoresistive (GMR) effect head or a tunnel magnetoresistive (TMR) effect head is used. As the density of HDD devices increases, there is a demand for magnetoresistive heads with higher sensitivity. In general, the magnetoresistive head has a structure in which an antiferromagnetic layer / a fixed layer / a nonmagnetic intermediate layer / a free layer are laminated in order from the substrate side. The fixed layer is a layer that fixes magnetization by exchange coupling with the antiferromagnetic layer. The free layer is a layer that responds to an external magnetic field. The relative magnetization direction of the fixed layer and the free layer changes due to the magnetization reversal of the free layer. The magnetoresistive head detects an external magnetic field by a change in electrical resistance when the magnetization direction changes.

  Until now, many read heads in which the direction of current flow is parallel to the film surface, that is, read heads of the CIP (Current-in-plane) method have been put into practical use. In recent years, tunnel magnetism using a tunneling current with a CPP (Current-Perpendicular-to-plane) type reproducing head and an intermediate layer as an insulator is used to further increase the sensitivity of the reproducing head. Research and development of magnetoresistive heads using the resistance (TMR: Tunneling Magneto-resistance) effect are being conducted.

In the TMR head, the rate of change in magnetoresistance (MR) is dramatically improved by applying MgO to the insulating layer. For example, in the case of an element having a sheet resistance of about 2.1 Ωμm ² , an MR change rate of 206% can be obtained (Non-Patent Document 1). However, the TMR head uses an insulator for the tunnel junction. For this reason, while the output is high, the high resistance acts disadvantageously in increasing the speed of rotation. For this reason, further resistance reduction is required.

  On the other hand, the CPP-GMR head employs a structure in which an extremely thin metal layer (Cu or the like) of about several nanometers is formed between two magnetic layers, and a current flows perpendicularly to the film surface. For this reason, in this type of head, it is necessary to detect a very small resistance change that occurs at intervals of about nm. As a result, there is a problem that the MR change rate is small and the output is very small. Further, when the resistance value is very small, it is affected by spin torque noise. For this reason, it has been a problem to increase the resistance value to some extent.

  In order to solve the problem of the CPP-GMR element having a very small resistance value, for example, it is conceivable to make the element structure multilayer. The MR ratio can be increased by multilayering. On the other hand, a narrow read gap is necessary to increase the resolution of the magnetic head. For this reason, a structure in which each element is simply multilayered is not suitable for solving the problem.

  In addition, a structure has been proposed in which the CPP-GMR intermediate layer is a composite layer of a nonmagnetic metal and an insulator, and the insulator has pinholes with low electrical resistance. Hereinafter, the insulating layer having pinholes is referred to as a screen layer. If the current is narrowed down using this screen layer, a high output can be obtained. However, the CPP-GMR adapted for the screen layer has a problem that it becomes difficult to control pinholes in the screen layer, while the output is increased. This is because the resistance value varies depending on the size and the number of pinholes existing in the screen layer. Moreover, as the element size is reduced, the variation becomes remarkable, which becomes a practical problem. In the screen layer, the flowing current is narrowed down, and a current having a large current density flows only in the pinhole. When the current density increases, heat is generated, migration occurs, and the element deteriorates.

JP 2008-283194 A

Appl.Phys.Lett., 93,192109 (2008) Jpn. J. Appl. Phys., 43,540 (2004) J.Mag.Mag.Mat., 316,481 (2007) Phys. Rev. B, 66, 174429 (2002)

  As described above, TMR using an insulator as an intermediate layer needs to have a low resistance, and CPP-GMR using a metal in the intermediate layer needs to have a high resistance. For this reason, the inventor has come to the idea that it is desirable to apply a material having intermediate characteristics between these two materials to the intermediate layer.

There are metalloids (semimetals) such as Sb and Bi as materials that exhibit electrical conductivity characteristics between insulators and metals. Metalloid, as shown in FIG. 3 (a), the Fermi energy E _F is the valence band (shown by the parabolic convex upward.) And the top of the conduction band (in the figure, downwardly convex It has an electronic state that crosses the lowermost part. A metalloid is characterized by its very few electronic states at the Fermi level when compared to metals. Compared to the carrier density of metal (10 ²¹ to 10 ²² cm ^-3 ), the carrier density of metalloid is on the order of 10 ¹⁸ to 10 ²⁰ cm ^-3 . Thus, the semimetal is known as a material system having a low carrier density. Non-Patent Document 2 is a document disclosing a CPP-GMR structure using such a semimetal for the intermediate layer. Non-Patent Document 2 shows a calculation model of a semimetal, and Sb, Bi, FeSi, and CoSi are proposed.

  However, Bi and Sb have a complicated structure such as a rhombohedral structure, and FeSi has a B20 type structure. For this reason, lattice matching is poor with respect to Fe, Co, and Ni (fcc structure, bcc structure, etc.) that are general ferromagnetic metals. In addition, materials such as Bi are materials having a very low melting point (melting point: 271 ° C.), and there is a concern of alloying with other materials and deterioration due to migration.

  In the present invention, not only the lattice matching with the fixed layer and the free layer is excellent, but also a high sensitivity magnetoresistive element composed of an intermediate layer having an excellent area uniformity and a high magnetoresistance ratio. The purpose is to provide.

  In order to achieve the above object, the present invention provides a magnetoresistive element having the following layer structure.

(1) Ferromagnetic pinned layer with the magnetization direction fixed substantially in one direction
(2) Ferromagnetic free layer whose magnetization direction changes according to the external magnetic field
(3) Intermediate layer formed between the fixed layer and the free layer Here, the intermediate layer is divided into L2 ₁ (full Heusler) structure, B2 (CsCl-type) structure, A2 structure, C1 _b (half Heusler) structure or It is formed of a compound material having an elemental composition having a B1 (NaCl-type) structure and having semi-metallic conduction characteristics (carrier density on the order of 10 ¹⁸ to 10 ²⁰ cm ⁻³ ).

By using a semimetal having a crystal structure such as L2 ₁ structure, B2 structure, A2 structure, C1 _b structure or B1 structure in the semimetal layer, a ferromagnetic Heusler alloy, bcc structure or fcc structure ferromagnetic metal It becomes possible to realize a three-layer structure of a fixed layer / intermediate layer / free layer with good consistency.

1 shows an L2 ₁ structure (FIG. 1 (a)), a B2 structure (FIG. 1 (b)), an A2 structure (FIG. 1 (c)), a C1 _b structure (FIG. 1 (d)), and a B1 structure (see FIG. 1). 1 (f)) is a schematic diagram. These metalloids dramatically improve lattice matching with ferromagnetic metals such as Fe and FeCo alloys and Heusler ferromagnetic alloys, compared to rhombohedral metalloids such as Bi and Sb.

For example, consider an example in which the ferromagnetic metal is Fe of the bcc structure and the metalloid intermediate layer is Fe ₂ VAl of the L2 ₁ structure. The lattice constant of Fe ₂ VAl is a _FVA = 5.761Å, which is about twice the lattice constant of Fe with the lattice constant a _Fe = 2.866Å. Fe has the bcc structure shown in FIG. When this bcc structure is three-dimensionally doubled, it becomes the same as the A2 structure shown in FIG. Therefore, the difference in lattice constant from the L2 ₁ structure shown in FIG. 1 (a) is only about 0.5%. From this, it can be seen that the lattice matching is good. It is also possible to change the lattice constant by substituting part of Fe in Fe ₂ VAl with a similar element in the periodic table such as Ru and part of V with Nb. For example, it is possible to adjust the lattice constant of the intermediate layer in consideration of the consistency with the ferromagnetic metal.

Even when the ferromagnetic metal layer is made of an alloy of Co or Ni and the ferromagnetic metal is made of a ferromagnetic Heusler alloy Co ₂ MnSi or Fe ₃ Si having a D0 ₃ structure, it is combined with an intermediate layer having good lattice matching. A structure with extremely good lattice matching can be produced.

  By adopting a structure with good lattice matching, even in the case of a multilayer structure having an interface, the coherent conduction of electrons is maintained, and the magnetoresistance due to the spin degree of freedom of the electrons is easily developed. Since the magnetoresistive element according to the present invention can form a three-layer structure of a fixed layer / intermediate layer / free layer with good matching, a high MR ratio can be realized.

Further, by adopting the layer structure proposed in the present invention, electrons that can be transmitted through the intermediate layer are limited due to the influence of the semi-metal layer that has fewer electronic states at the Fermi level than the metal. Hereinafter, it will be described that the transmission of electrons can be restricted when the metalloid layer is Fe ₂ VAl.

FIG. 2 shows a structure obtained by projecting the Fe ₂ VAl band structure obtained by the first principle calculation onto a two-dimensional surface. According to the phase diagram in which the band structure of Fe ₂ VAl is projected in two dimensions, it can be seen that there are very few states in the wave number space. Further, as shown in Non-Patent Document 3 and the like, the transmittance of electrons in a device having a three-layer structure in which an intermediate layer exists between two electrodes is given by an average value of transmittance depending on the wave number, It is represented by the following formula 1.

Where T _σ is the transmittance of the system, T _kσ is the transmittance depending on the wave number (kx, ky), ε is the energy, σ is the spin degree of freedom, and a is the lattice constant of the crystal It is.

Therefore, when Fe ₂ VAl having a very small number of states in the wave number space is used for the intermediate layer, the transmittance is very small due to the influence of the electronic state. Therefore, in the structure of the present invention, the electron transmittance can be drastically reduced as compared with the case where an ordinary metal is used for the intermediate layer, and even in an ultrathin film having a thickness less than the mean free path (about several nm), the area resistance is reduced. Can be made high enough. On the other hand, when the insulator is an intermediate layer (in the case of TMR), the electron transmittance decreases exponentially as the film thickness increases. For this reason, in order to realize a sheet resistance equivalent to that of a semimetal, an ultrathin film of 1 nm or less must be realized. On the other hand, when a metalloid is used for the intermediate layer, the material is greatly different from a material having no Fermi level state such as an insulator, and a small sheet resistance value equivalent to 1 nm or less can be easily realized. . Thus, in the case of the present invention, an appropriate sheet resistance and a high MR ratio can be realized. Therefore, when the magnetoresistive element according to the present invention is used for a magnetic head, a structure satisfying the requirement for a narrow read gap necessary for improving the resolution can be easily formed.

  FIG. 3 (a) shows a schematic diagram of a semi-metallic band structure. As shown in FIG. 3A, the semimetal has a state of a valence band and a conduction band slightly near the Fermi level. The conduction characteristics of a semimetal are susceptible to its band structure and Fermi level position due to doping. For this reason, the conduction characteristics of the semimetal can be easily changed by doping. At this time, if an element having similar properties such as a family element is doped, only the band structure can be changed while the Fermi level is fixed as shown in FIGS. As a result, the number of states at the Fermi level can be increased or decreased. On the other hand, if the elements having different valence electrons are doped, as shown in FIGS. 3D and 3E, the carrier density of holes or electrons can be changed while the band structure is fixed. That is, only the Fermi level can be changed. Even in this case, the number of states at the Fermi level can be increased or decreased. In any of the doping methods, the state near the Fermi level can be controlled, and the sheet resistance can be adjusted by modulating the state contributing to transmission.

  Further, in the structure having the semi-metal intermediate layer, the current can be appropriately reduced without forming a pinhole structure like the screen layer. When metalloid is used for the intermediate layer, a uniform thin film can be used, so there is no high current density region due to pinholes like the screen layer, and generation of heat and electromigration are suppressed. Can do.

L2 ₁ structure, B2 structure, A2 structure, C1 _b structure, simple bcc structure, schematic view of the B1 structure (NaCl type). A diagram of the band structure at the Fermi level of Fe ₂ VAl projected into a two-dimensional wave number space. The schematic diagram which shows the change of the metalloid band structure by metalloid band structure and doping. The figure which shows the cross-section structural example of the principal part of CPP-GMR. The figure explaining the change of Fe atom concentration distribution in a concentration gradient layer. The figure which shows the cross-section structural example of the principal part of CPP-GMR in an Example. 1 is a diagram showing a schematic configuration example of a magnetic disk device. The figure which shows the schematic structural example of a magnetoresistive memory device.

  Hereinafter, embodiments of the invention will be described with reference to the drawings. In addition, all the form examples mentioned later are examples.

(Semi-metal layer)
The relationship between the crystal structure of the metalloid layer, which is the main feature of the present invention, and specific compounds is shown below.

Examples of the semimetal having the L2 ₁ structure (full Heusler) include Fe ₂ VAl, Fe ₂ NbAl, and Ru ₂ VAl. It is known that a full Heusler alloy exhibits Slater-Pauling behavior (Non-patent Document 4). Therefore, when the total number of valence electrons of Fe ₂ VAl is calculated using the relationship between the number of valence electrons and elements shown in Table 1, 8 × 2 + 5 × 1 + 3 × 1 = 24.

Here, it is expected that all of the X ' ₂ Y'Z' stoichiometric compositions having a total valence electron number of 24 exhibit similar properties. For example, Fe ₂ TiSi has similar properties. Therefore, in the case of the semimetal according to this embodiment, any compound may be used as long as the compound has a composition in which the total valence number is close to 24 from the relationship between the number of valence electrons and elements shown in Table 1. Can do. Basically, it is desirable to use a compound having an L2 ₁ structure which is a regular structure as the semimetal layer. However, it is also possible to use a compound having an A2 structure in which atomic disorder occurs in the L2 ₁ structure and the degree of order decreases and the A2 structure is indistinguishable depending on elements, as the semimetal layer. In this case, the metalloid layer contains at least one or more transition elements in a total range of about 75 atomic%.

The semi-metal having a C1 _b structure, for example MgAgAs, NiTiSn, CoTiSb, FeVSb, ZrNiSn, the half-Heusler alloy having a composition in the vicinity of ZrCoSb. In addition to these, the half-Heusler alloy exhibits a Slater-Pauling behavior like the full-Heusler alloy, and it can be expected that all compounds having the same total number of valence electrons as FeVSb exhibit similar properties.

For example, the total number of valence electrons of FeVSb is 8 × 1 + 5 × 1 + 5 × 1 = 18 from the relationship between the number of valence electrons and elements shown in Table 1. That is, the total number of valence electrons in the stoichiometric composition of X′Y′Z ′ is 18. From the viewpoint of the similarity of the electronic state, any compound having a composition in which the total valence electron number is in the vicinity of 18 due to the relationship between the number of valence electrons and elements shown in Table 1 can be expected to be semi-metallic. Therefore, a compound satisfying a composition having a total number of valence electrons of around 18 can be used as the metalloid layer having a C1 _b structure. Further, when the number of valence electrons of an alkali metal which is an element not specified in Table 1 is 1 and the number of valence electrons of an alkaline earth metal is 2 as a semimetal layer having a C1 _b structure, the total number of valence electrons is 18. A compound having a composition such as MgAgAs can also be used. In this case, the metalloid layer contains at least one or more transition elements in a total range of about 33 to about 66 atomic%.

Examples of semimetals having a B1 structure include ScSb _1-α As _α (0.0 ≦ α ≦ 1.0), YSb _1-α As _α (0.0 ≦ α ≦ 1.0), LnSb _1-α As _α (Ln is a lanthanoid: La , Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu), (0.0 ≦ α ≦ 1.0). In this case, the metalloid layer contains at least one or more transition elements in a total range of about 50 atomic%.

  In the case of the magnetoresistive element according to the invention, the transmittance of electrons in the metalloid layer can be controlled by doping the metalloid layer. The doping to the semimetal layer in the present invention will be described.

The metalloid layer having the L2 ₁ structure, B2 structure, and A2 structure in the present invention has a total valence electron number of 24 based on the calculation of the valence number shown in Table 1 in the stoichiometric composition of X ′ ₂ Y′Z ′. The case is fundamental. For example, a doping technique for keeping the total number of valence electrons constant can be given. Here, Fe ₂ VAl will be described as an example. For example, a part of V (vanadium) atoms is substituted with Nb atoms so that the total number of valence electrons is constant. For example, when Fe ₂ V _0.8 Nb _0.2 Al is used, the total number of valence electrons is 24, and the total number of valence electrons is not changed.

However, the electronic state near the Fermi level of the compound after doping with Nb atoms changes, and the electronic state contributing to the electron transmittance can be controlled. Further, if a part of V (vanadium) atoms is replaced with an element having a different atomic radius, the lattice constant changes, and the lattice constant can be controlled by adjusting the doping amount. In the above example, Y ′ in X ′ ₂ Y′Z ′ has been replaced with an element having the same number of valence electrons, but element X ′ or element Z ′ can also be replaced.

In the semi-metal layer having the C1 _b structure, the total number of valence electrons is 18 based on the calculation of the number of valence electrons shown in Table 1 in the stoichiometric composition of X′Y′Z ′. Therefore, similarly to the L2 ₁ structure, in the C1 _b structure, X′Y′Z ′ can be replaced by an element having the same number of valence electrons.

In addition, there is a doping technique in which the total number of valence electrons is slightly changed. Here, Fe ₂ VAl will be described as an example. For example, consider a case where a part of the V (vanadium) atom is replaced with a Ti atom so that the total valence electron number slightly changes. When the composition after substitution is Fe ₂ V _0.8 Ti _0.2 Al, the total number of valence electrons is 23.8. As a result, the electronic state in the vicinity of the Fermi level changes, and the electron transmittance can be controlled.

In the above example, the method of substituting the element Y ′ in X ′ ₂ Y′Z ′ with an element having the same number of valence electrons has been described, but the element X ′ or the element Z ′ can also be replaced. If the total number of electrons deviates more than 24, it becomes a non-magnetic metal or ferromagnetic metal property, and semi-metallic conduction characteristics cannot be obtained. Therefore, it is desirable to dope so that the total number of valence electrons is in the range of 23.5 to 24.5. For example, it is desirable that the total number of valence electrons after doping falls within a range of about ± 0.5 or about 2% of the total number of valence electrons before doping.

Similarly, in a metalloid layer having a C1 _b structure, the total number of valence electrons is in the range of 17.8 to 18.2 near 18 by substituting each element of X′Y′Z ′ with an element having a different valence number. It is desirable to dope like this. For example, it is desirable that the total number of valence electrons after doping falls within a range of change of about ± 0.2 or about 1.1% of the total number of valence electrons before doping.

In addition, doping with a semi-metal having a B1 structure (for example, ScSb _1-α As _α , YSb _1-α As _α , LnSb _1-α As _α (0.0 ≦ α ≦ 1.0), for example, Mg, Ca, Sr, Ba It is desirable to use at least one of Ti, Zr, Hf, C, Si, Ge, Sn, N, P, O, S, Se, and Te. desirable.

  From the above, it is desirable that the metalloid layer contains at least one or more transition elements in a total range of about 30 to 80 atomic%.

(Ferromagnetic layer)
In the present invention, the material of the ferromagnetic layer is not particularly limited. Therefore, for example, a ferromagnetic metal such as Fe, Co, and Ni, an alloy thereof, and FeCoB can be used for the ferromagnetic layer. If a ferromagnetic Heusler alloy with a spin polarization such as Co ₂ MnAs, Co ₂ MnSi, Co ₂ FeSi, Ru ₂ MnSi, or Mn ₂ VAl is used for the ferromagnetic layer, a structure with good lattice matching can be obtained. It can be formed.

(Structural example of magnetoresistive element)
As shown in FIG. 4A, a CPP-GMR structure can be obtained by laminating the above-described semimetal and a semimetal layer 20 doped with another metal in the middle of the ferromagnetic fixed layer 210 and the ferromagnetic free layer 200. Can be produced. The ferromagnetic pinned layer refers to a layer containing a ferromagnetic material whose magnetization direction is fixed in one direction. A ferromagnetic free layer refers to a layer containing a ferromagnetic material whose magnetization direction changes in response to an external magnetic field.

(Composite metalloid layer)
Hereinafter, a composite metalloid layer that can be used as an intermediate layer between the fixed layer and the free layer will be described.

  As described above, the properties of the metalloid layer can be changed by doping the metalloid layer. At that time, a semi-metal layer having different properties can be laminated in a multilayer structure to form a composite semi-metal layer, which can be used as an intermediate layer.

  FIG. 4B shows a composite metalloid layer 24 in which two metalloid layers are laminated. For example, a semimetal layer 21 having a total valence electron of 23.8 is employed as the semimetal layer 1, and a semimetal layer 22 having a total valence electron number of 24.2 is employed as the semimetal layer 2.

  FIG. 4C shows a composite metalloid layer 24 in which three metalloid layers are laminated. For example, a semi-metal layer 21 with a total valence electron of 23.8 is adopted as the semi-metal layer 1, a semi-metal layer 22 with a total valence electron number of 24 is adopted as the semi-metal layer 2, and the total valence electron number is as the semi-metal layer 3. The 24.2 metalloid layer 23 is employed.

  The composite metalloid layer used as the intermediate layer is not limited to the two-layer structure and the three-layer structure as long as it has the structure of the present invention, and may be a multilayer structure of four or more layers. However, it is desirable that the thickness of the entire intermediate layer, which is the sum of the thicknesses of the layers, is 1 nm or more and 10 nm or less.

Next, a composite metalloid layer having a concentration gradient layer will be described. When the metalloid layer and the ferromagnetic layer form an interface, a layer having a concentration gradient between the ferromagnetic layer and the metalloid layer can be formed. Hereinafter, a case where Fe ₂ VAl is used for the metalloid layer and Fe ₃ Al is used for the ferromagnetic layer will be described.

  As shown by a thick line in FIG. 5, in the case of having an ideal steep ferromagnetic / metalloid interface structure, Fe in the ferromagnetic layer is 75 atomic% and Fe in the semimetal layer is 50 atomic%. In this case, the concentration gradient layer can be formed at the boundary between the semimetal layer and the ferromagnetic layer by forming a layer having different atomic diffusion or atomic% at the interface by heat treatment or the like.

  In order to reduce the total film thickness and make the composite semimetal layer thinner than the mean free path of electrons, a steep composition distribution is desirable, but in order to improve the crystal matching, it is advantageous to form a concentration gradient layer It becomes. Therefore, as shown in FIG. 4D, by forming the composite semimetal layer 24 composed of the concentration gradient layer 220 and the semimetal layer 20 between the ferromagnetic pinned layer 210 and the ferromagnetic free layer 200. The ferromagnetic layer and the semimetal layer having different lattice constants can be smoothly joined. Thereby, the lattice matching between each layer can be improved.

  Such a concentration gradient layer 220 can be produced by a heat treatment after forming a ferromagnetic / metalloid interface. In addition, when two or more targets having different compositions are used, the concentration gradient layer 220 can be produced by adjusting the amount of sputtering simultaneously or alternately.

  The above-described crystal structure and multilayer structure can be easily confirmed by observing a lattice image with a cross-sectional TEM (Transmission Electron Miroscop) or the like. Further, in the electron beam diffraction image, it can be confirmed from the spot-like pattern or the ring-like pattern whether it has a single crystal crystal structure or a polycrystalline crystal structure. The multilayer structure and composition distribution can be confirmed using EDX (Energy Dispersive X-ray spectroscopy), SIMS (Secondary Ionization Mass Spectrometer), X-ray photoelectron spectroscopy, and the like.

  The characteristics of the metalloid can be confirmed by measuring the sheet resistance in the CPP-GMR structure and determining whether the intermediate layer can have a higher sheet resistance than a normal metal (for example, Cu). In addition, the characteristics of the semimetal are that a thin film having the same composition as the semimetal layer is formed on a general substrate (for example, a Si substrate) by a thin film preparation method such as sputtering, and the electric resistance of the thin film is measured and the Hall effect is measured. It can be confirmed by evaluation of carrier density by measurement.

(Mechanism of electron conduction control)
The mechanism of electron conduction control by the semimetal according to the present invention is different from that for limiting the region where current flows in real space such as a screen layer. In the metalloid according to the present invention, by forming a ferromagnetic / metalloid junction with good lattice matching, current flows through the entire thin film in real space, while the conduction channel is limited in wavenumber space. .

[Example 1]
A first embodiment of the present invention will be described. In this example, an Si substrate having a thermal oxide film on the substrate surface was used to produce an electrode, and then the main part of the CPP-GMR film was produced on the electrode.

  FIG. 6A shows a schematic diagram of a cross-sectional structure of a main portion of the magnetoresistive element according to this example. Details of the main part of the produced magnetoresistive element are as shown in the following materials and film thicknesses.

Ta: 3 nm (underlayer 250) / Ru: 2 nm (underlayer 250) /
MnIrCr: 6 nm (antiferromagnetic layer 240) / CoFe: 2 nm (ferromagnetic pinned layer 1 (211)) /
Ru: 0.8 nm (antiparallel coupling layer 230) / CoFe: 4 nm (ferromagnetic pinned layer 2 (212)) /
FeVAl: 2.5 nm (semi-metal intermediate layer 20) / CoFe: 4 nm (ferromagnetic free layer 200) /
Cu: 2 nm (cap layer 260) / Ru: 3 nm (cap layer 260)
The manufactured sample has a sheet resistance of 0.2Ωμm ² and an MR ratio of 100%, realizing an appropriate sheet resistance and a high MR ratio. When a sample with a film thickness of 1.5 nm was prepared as the semimetal Fe ₂ VAl, the sheet resistance decreased. Therefore, the resistance can be adjusted by controlling the film thickness of the semimetal layer, and an appropriate area resistance can be realized.

[Example 2]
A second embodiment of the present invention will be described. In this example, as in Example 1, the main part of the CPP-GMR film was formed on the electrode. The cross-sectional structure in the second embodiment is the same as that in FIG. Details of the main part of the produced magnetoresistive element are as shown in the following materials and film thicknesses.

Ta: 3 nm (underlayer 250) / Ru: 2 nm (underlayer 250) /
MnIrCr: 6 nm (antiferromagnetic layer 240) / CoFe: 2 nm (ferromagnetic pinned layer 1 (211)) /
Ru: 0.8 nm (antiparallel coupling layer 230) / Co ₂ CrAl: 4 nm (ferromagnetic pinned layer 2 (212)) /
Fe ₂ VAl: 2.5 nm (metalloid intermediate layer 20) / Co ₂ CrAl: 4 nm (ferromagnetic free layer 200) /
Cu: 2 nm (cap layer 260) / Ru: 3 nm (cap layer 260)
Inventors, a Co ₂ CrAl in the ferromagnetic pinned layer and the free layer, by sputtering of a mixed target of Co ₂ CrAl, Fe ₂ VAl in the semi-metal layer, it was confirmed that can be produced by sputtering of a mixed target of Fe ₂ VAl . The lattice constant of Heusler ferromagnetic metal Co ₂ CrAl is 5.73 mm, and the lattice constant of semimetal Fe ₂ VAl is 5.76 mm. The difference in lattice constant is about 0.5%, and a structure with very good lattice matching can be produced.

[Example 3]
A third embodiment of the present invention will be described. Also in this example, as in Example 1, the main part of the CPP-GMR film is formed on the electrode. The cross-sectional structure in the third embodiment is also the same as that shown in FIG. Details of the main part of the produced magnetoresistive element are as shown in the following materials and film thicknesses.

Ta: 3 nm (underlayer 250) / Ru: 2 nm (underlayer 250) /
MnIrCr: 6 nm (antiferromagnetic layer 240) / CoFe: 2 nm (ferromagnetic pinned layer 1 (211)) /
Ru: 0.8 nm (antiparallel coupling layer 230) / Co ₂ CrAl: 4 nm (ferromagnetic pinned layer 2 (212)) /
Fe ₂ V _0.9 Ti _0.1 Al: 2.5 nm (metalloid intermediate layer 20) / Co ₂ CrAl: 4 nm (ferromagnetic free layer 200) /
Cu: 2 nm (cap layer 260) / Ru: 3 nm (cap layer 260)
The inventors sputtered the Co ₂ CrAl in the ferromagnetic pinned layer and the free layer with a mixed target of Co ₂ CrAl, so that Fe ₂ V _0.9 Ti _0.1 Al in the semi-metal layer was mixed with Fe ₂ VAl and Ti. It was confirmed that can be produced by sputtering. The inventors have also confirmed that the sheet resistance changes due to Ti doping.

[Example 4]
A fourth embodiment of the present invention will be described. Also in this example, as in Example 1, the main part of the CPP-GMR film is formed on the electrode. FIG. 6B shows a schematic diagram of a cross-sectional structure of the main part of the magnetoresistive element according to this example. Details of the main part of the produced magnetoresistive element are as shown in the following materials and film thicknesses.

Ta: 3 nm (underlayer 250) / Ru: 2 nm (underlayer 250) /
MnIrCr: 6 nm (antiferromagnetic layer 240) / CoFe: 2 nm (ferromagnetic pinned layer 1 (211)) /
Ru: 0.8 nm (antiparallel coupling layer 230) / CoFe: 0.5 nm (interface magnetic layer 270) / Co ₂ MnGe: 4 nm (ferromagnetic pinned layer 2 (212)) /
Ru ₂ VAl: 2.5 nm (metalloid intermediate layer 20) / Co ₂ MnGe: 4 nm (ferromagnetic free layer 200) / CoFe: 0.5 nm (interface magnetic layer 270) /
Cu: 2 nm (cap layer 260) / Ru: 3 nm (cap layer 260)
The inventor has confirmed that a magnetoresistive element having a Heusler ferromagnetic metal Co ₂ MnGe as an intermediate layer and Ru ₂ VAl as a semimetal layer can be produced. The produced magnetoresistive element had a sheet resistance of 0.25 Ωμm ² and an MR ratio of 100%. If a magnetic layer different from the ferromagnetic pinned layer or the free layer such as the interface magnetic layer 270 is formed between the ferromagnetic pinned layer and the nonmagnetic metal Ru or Cu as in this embodiment, the ferromagnetic layer It is possible to prevent diffusion of atoms constituting the fixed layer. Therefore, in this embodiment, an interfacial magnetic layer may be formed at the interface where the ferromagnetic pinned layer and the free layer are joined to the nonmagnetic metal. In addition to the above example, NiFe or the like can be used for the interface magnetic layer.

[Example 5]
A fifth embodiment of the present invention will be described. Also in this example, as in Example 1, the main part of the CPP-GMR film is formed on the electrode. FIG. 6C is a schematic diagram of a cross-sectional structure of the main part of the magnetoresistive element according to the third example. Details of the main part of the produced magnetoresistive element are as shown in the following materials and film thicknesses.

Ta: 3 nm (underlayer 250) / Ru: 2 nm (underlayer 250) /
MnIrCr: 6 nm (antiferromagnetic layer 240) / CoFe: 2 nm (ferromagnetic pinned layer 1 (211)) /
Ru: 0.8 nm (antiparallel coupling layer 230) / CoFe: 0.5 nm (interface magnetic layer 270) / Co ₂ CrAl: 4 nm (ferromagnetic pinned layer 2 (212)) /
Fe ₂ V _0.9 Ti _0.1 Al: 1 nm (metalloid layer 1 (21)) / Fe ₂ V _0.9 Cr _0.1 Al: 1 nm (metalloid layer 2 (22)) /
Co ₂ MnSi: 2 nm (ferromagnetic free layer 200) / CoFe: 0.5 nm (interface magnetic layer 270) /
Cu: 2 nm (cap layer 260) / Ru: 3 nm (cap layer 260)
The inventor made Fe ₂ V _0.9 Ti _0.1 Al of the semimetal layer 1 by sputtering of a mixed target of Fe ₂ VAl and Ti, and Fe ₂ V _0.9 Cr _0.1 Al of the semimetal layer 2 of Fe ₂ VAl and Cr. It was confirmed that it could be produced by sputtering a mixed target.

[Example 6]
A sixth embodiment of the present invention will be described. Also in this example, as in Example 1, the main part of the CPP-GMR film is formed on the electrode. FIG. 6D is a schematic diagram of a cross-sectional structure of the main part of the magnetoresistive element according to the sixth example. Details of the main part of the produced magnetoresistive element are as shown in the following materials and film thicknesses.

Ta: 3 nm (underlayer 250) / Ru: 2 nm (underlayer 250) /
MnIrCr: 6 nm (antiferromagnetic layer 240) / CoFe: 2 nm (ferromagnetic pinned layer 1 (211)) /
Ru: 0.8 nm (antiparallel coupling layer 230) / CoFe: 0.5 nm (interface magnetic layer 270) / Co ₂ CrAl: 4 nm (ferromagnetic pinned layer 2 (212)) /
Fe ₂ V _0.8 Ti _0.2 Al: 1 nm (metalloid layer 1 (21)) / Fe ₂ VAl: 1 nm (metalloid layer 2 (22)) /
Fe ₂ V _0.8 Cr _0.2 Al: 1 nm (metalloid layer 3 (23)) / Co ₂ MnSi: 2 nm (ferromagnetic free layer 200) / CoFe: 0.5 nm (interface magnetic layer 270) /
Cu: 2 nm (cap layer 260) / Ru: 3 nm (cap layer 260)
Inventors, the Fe ₂ V _0.9 Ti _0.1 Al metalloid layer 1 by the sputtering of mixed target of Fe ₂ VAl and Ti, a Fe ₂ VAl metalloid layer 2 by sputtering of a mixed target of Fe ₂ VAl, half It was confirmed that Fe ₂ V _0.9 Cr _0.1 Al of the metal layer 3 can be produced by sputtering of a mixed target of Fe ₂ VAl and Cr.

[Example 7]
In the above-described embodiments, the case where the L2 ₁ structure is the main material in the metalloid layer has been described. However, a compound having a C1 _b structure and a B1 structure controlled to the materials and compositions described above may be used for the semimetal layer.

[Example 8]
In the above-described embodiments, the case where a CoFe alloy or a full Heusler ferromagnetic alloy is mainly used for the ferromagnetic fixed layer and the free layer has been described. However, other half-Heusler ferromagnetic metals and other ferromagnetic metals may be used as the ferromagnetic fixed layer and the free layer.

[Example 9]
In the above-described embodiment, the case where Ta or Ru is used for the base layer has been described. However, a single layer film such as Al, Cu, Cr, Fe, Nb, Hf, Ni, Ta, Ru, NiFe, NiCr, or NiFeCr or a multilayer film of these materials may be used as the underlayer.

[Example 10]
In the above-described embodiment, the case where MnIrCr (6 nm) is used for the antiferromagnetic layer has been described. However, MnIr, MnPt, NiMn, FeMn and other antiferromagnetic materials may be used as the antiferromagnetic layer.

[Example 11]
In the above description, the case where the magnetoresistive element according to the invention is applied to a magnetic reproducing head using CPP-GMR has been mainly described. However, the magnetoresistive element according to the invention can also be applied to various magnetic devices using CPP-GMR elements. Specifically, the present invention can be applied to various sensors such as a nonvolatile memory such as a magnetic random access memory (MRAM) and a magnetic orientation sensor.

  Hereinafter, structural examples of the magnetic disk device (FIG. 7) and the MRAM (FIG. 8) in which the magnetoresistive element according to the invention is applied to a magnetic reproducing head will be briefly described.

  FIG. 7 shows a structural example of the magnetic disk device 720. A magnetic disk 702 that is a recording medium is disposed in a housing 701 of the magnetic disk device 720. FIG. 7 shows the case of a multi-disk structure. Accordingly, one magnetic head is disposed on one magnetic disk 702. The magnetic disk 702 is rotated at high speed by a spindle motor 703. A magnetic head 710 is mounted at the tip of the suspension 700, and the root portion of the suspension 700 is connected to the arm 704. The magnetic head 710 includes a recording head and a reproducing head, and the above-described magnetoresistive element is used for the reproducing head. The arm 704 is driven in a plane parallel to the surface of the magnetic disk 702 by a rotary actuator 705. The magnetic head 710 is moved to a predetermined position on the magnetic disk 702 by the drive control of the arm 704 by the rotary actuator 705. The magnetic disk device 720 is also provided with a signal processing LSI (signal processing circuit) 706 for processing write information and read information.

  FIG. 8 shows an example structure of the MRAM 800. As shown in FIG. 8A, on the base of the MRAM 800, the memory elements 803 made of the magnetoresistive elements described above are formed in a matrix. Of the magnetoresistive element, the ferromagnetic free layer side is connected to the bit line 801, and the ferromagnetic fixed layer side is connected to the source / drain electrodes (one of the main electrodes) of the selection transistor 804. A gate electrode (control electrode) of the selection transistor 804 is connected to the word line 802. Note that the selection transistor 804 is formed of, for example, a MOSFET. The other source / drain electrode (the other of the main electrodes) of the selection transistor 804 is grounded.

  The magnetic azimuth sensor can be configured by forming a bridge circuit with four magnetoresistive elements, and disposing a thin spiral coil on the surface of the bridge circuit via an insulating film.

20: Metalloid layer 21: Metalloid layer 1
22: Metalloid layer 2
23: Metalloid layer 3
24: Composite metalloid layer
200: Ferromagnetic free layer 211: Ferromagnetic fixed layer 1
212: Ferromagnetic pinned layer 2
220: concentration gradient layer 230: antiparallel coupling layer 240: antiferromagnetic layer 250: underlayer 260: cap layer 270: interface magnetic layer

Claims (8)

A pinned layer including a ferromagnetic material whose magnetization direction is fixed in one direction;
A free layer comprising a ferromagnetic material whose magnetization direction changes in response to an external magnetic field;
Having one or more intermediate layers between the ferromagnetic pinned layer and the ferromagnetic free layer;
Or at least one layer of the intermediate layer, and characterized in that it is a semi-metal layer having at least either one structure of the entire or partially L2 ₁ structure, B2 structure, A2 structure, C1 _b structure or B1 structure Magnetoresistive element. The magnetoresistive element according to claim 1,
Sc, Y, La, Ce, Pr, Nd, Sm, Gd, Tb, Dy, Ho, Er, Tm, Lu, Ti, Zr, Hf, Cr, Mo, W, Mn, Re, on the metalloid layer At least one element selected from Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, V, Nb, and Ta is included in a total range of 30 to 80 atomic%. The magnetoresistive element characterized by the above-mentioned. The magnetoresistive element according to claim 2,
The magnetoresistive element, wherein the intermediate layer is a composite intermediate layer including a layer having a gradient in composition of constituent elements between the fixed layer or the free layer and the metalloid compound layer. The magnetoresistive element according to claim 2,
The magnetoresistive element, wherein the intermediate layer is a composite intermediate layer having a multilayer structure of at least two metalloid layers having different constituent elements and compositions. The magnetoresistive element according to claim 1,
The at least one semi-metal layer of the intermediate layer is mainly composed of three elements selected from Fe—V—Al, Fe _— Ti _— Si, Mn—V—Sb, and Ru—V—Al. A magnetoresistive element. The magnetoresistive element according to claim 1,
The magnetoresistive element, wherein the intermediate layer is 1 nm or more and 10 nm or less. A magnetic disk;
A motor for driving the magnetic disk;
A recording head for recording information on the magnetic disk;
A reproducing head for reproducing information from the magnetic disk;
A signal processing circuit for processing the information,
The magnetoresistive element constituting the read head is
A pinned layer including a ferromagnetic material whose magnetization direction is fixed in one direction;
A free layer comprising a ferromagnetic material whose magnetization direction changes in response to an external magnetic field;
Having one or more intermediate layers between the fixed layer and the free layer;
Or at least one layer of the intermediate layer, and characterized in that it is a semi-metal layer having at least either one structure of the entire or partially L2 ₁ structure, B2 structure, A2 structure, C1 _b structure or B1 structure Magnetic disk unit to be used. In a magnetoresistive memory device in which memory elements are arranged in a matrix,
The memory element includes a magnetoresistive element connected to a bit line, and a transistor element in which one of the magnetoresistive element and a main electrode is connected, the other main electrode is grounded, and a control electrode is connected to a word line. Configured,
The magnetoresistive element is
A pinned layer including a ferromagnetic material whose magnetization direction is fixed in one direction;
A free layer comprising a ferromagnetic material whose magnetization direction changes in response to an external magnetic field;
Having one or more intermediate layers between the fixed layer and the free layer;
Or at least one layer of the intermediate layer, and characterized in that it is a semi-metal layer having at least either one structure of the entire or partially L2 ₁ structure, B2 structure, A2 structure, C1 _b structure or B1 structure Magnetoresistive storage device.

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