JP2004179668A - Magnetoresistive element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetoresistance element capable of improving an MR ratio in a tunnel magnetoresistive (TMR) element and decreasing variation in resistance. <P>SOLUTION: In one form of a TMR element, a surface control layer, which is an amorphous conductor, is arranged between a substrate and a tunnel layer. Also, in another form, at least one of a pair of magnetic layers sandwiching the tunnel layer has a polycrystalline structure having a controlled crystal orientation surface in addition to a fine surface. In still another form, at least one of the pair of magnetic layers includes at least one kind of magnetic element and the element other than the magnetic element, and the average number of electrons calculated from the composition ratio is adjusted to not less than 23.5 and not more than 25.5, or not less than 26.5 and not more than 36. Moreover, in still another form, an alloy containing a surplus element or an element capturing layer for capturing the surplus element including a compound is further formed, and the content of the surplus element is higher in the surplus element capturing layer than any one of the pair of magnetic layers. <P>COPYRIGHT: (C)2004,JPO

Description

  The present invention relates to a magnetoresistance element. This magnetoresistive element can be used, for example, in a reproducing head for a magnetic medium such as a magnetic disk, a magneto-optical disk, and a magnetic tape, a magnetic sensor used in an automobile, and a magnetic random access memory (MRAM).

  In recent years, tunnel magnetoresistive (TMR) elements have been actively studied. In the TMR element, the tunnel transition probability changes according to the angle between the magnetization directions of two ferromagnetic layers arranged so as to sandwich the tunnel nonmagnetic layer (tunnel insulating layer). In the TMR element, a higher MR change can be expected as the spin polarizability near the Fermi surface of the magnetic layer increases. FeCo alloys, NiFe alloys, and half-metallic ferromagnetic materials are known as metal magnetic materials that can be expected to have high polarizability.

  However, a material exhibiting MR characteristics exceeding these metallic magnetic materials has not been reported so far.

  Also, in the TMR element, when the element size becomes submicron, the grain boundary of the polycrystalline substrate or the grain growth of the thick film electrode causes variation in the junction resistance due to a change in the thickness or film quality of the tunnel insulating layer.

  An object of the present invention is to provide a TMR element having a higher MR ratio than the conventional one. Another object of the present invention is to provide a TMR element in which a variation in junction resistance is suppressed.

  A first TMR element of the present invention includes a substrate, and a multilayer film formed on the substrate, wherein the multilayer film includes a tunnel layer, and a pair of magnetic layers sandwiching the tunnel layer. The resistance value changes according to the relative angle of the magnetization direction in the pair of magnetic layers, and a conductive layer is disposed between the substrate and the tunnel layer, and the conductive layers are a) Pt, Pd, Ag, Au, A conductor made of at least one selected from C, Si, Ge, Sn and Pb, b) an amorphous film, c) a microcrystalline film having an average crystal grain size of 5 nm or less, d) a Cu film and a metal film other than Cu And at least one member selected from the group consisting of:

  The second TMR element of the present invention includes a substrate, and a multilayer film formed on the substrate, wherein the multilayer film includes a tunnel layer, and a pair of magnetic layers sandwiching the tunnel layer. The resistance value changes according to the relative angle of the magnetization direction in the pair of magnetic layers, and at least one of the pair of magnetic layers has a lattice constant calculated from e) a crystal structure of 0.1% or more and 5% or more. Lattice distortion represented by different lattice constants in the following ranges; f) a crystal structure different from the crystal structure formed preferentially at normal temperature and pressure (atmospheric pressure); and g) a crystal controlled other than a fine surface. And at least one selected from a polycrystalline structure having an orientation plane.

  A third TMR element of the present invention includes a substrate, and a multilayer film formed on the substrate, wherein the multilayer film includes a tunnel layer, and a pair of magnetic layers sandwiching the tunnel layer. The resistance value changes according to the relative angle of the magnetization direction in the pair of magnetic layers. At least one of the pair of magnetic layers has at least one magnetic element selected from Fe, Co, and Ni, and at least one other than the magnetic element. And an average number of electrons is 23.5 or more and 25.5 or less or 26.5 or more and 36 or less. Here, the average number of electrons is the number of electrons per atom calculated according to the composition, and can be obtained by averaging the atomic numbers (number of electrons) of the atoms in the film.

  A fourth TMR element of the present invention includes a substrate, and a multilayer film formed on the substrate, wherein the multilayer film includes a tunnel layer, and a pair of magnetic layers sandwiching the tunnel layer. The resistance value changes according to the relative angle of the magnetization direction in the pair of magnetic layers, and at least one layer other than the pair of magnetic layers and included in the multilayer film is at least one layer of the pair of magnetic layers. The excess of which decreases the spin polarizability of at least one of the layers when the concentration in the multilayer increases, the multilayer film further includes a surplus element capture layer containing an alloy or compound containing the surplus element, the surplus element The element content is higher in the surplus element trapping layer than in any of the pair of magnetic layers.

  Hereinafter, a preferred embodiment of the present invention will be described.

  As shown in FIG. 1, the TMR element of the present invention has a basic configuration in which a pair of magnetic layers 6 and 8 sandwich a tunnel layer 7. The tunnel layer 7 may be made of an insulator such as a nitride, an oxide, a boride, or a carbide, or a semiconductor. The magnetic layers 6 and 8 may be ferromagnetic or ferrimagnetic.

  The TMR element of the present invention may be a so-called spin valve element. In this case, one of the magnetic layers is a fixed magnetic layer that is relatively hard to rotate the magnetization with respect to the external magnetic field, and the other is a free magnetic layer that is relatively easy to rotate the magnetization. A magnetization rotation control layer such as an antiferromagnetic layer or a laminated ferrimagnetic layer may be magnetically coupled to the fixed layer to suppress magnetization rotation. A soft magnetic layer may be magnetically coupled to the free layer.

(Embodiment 1)
First, the first TMR element of the present invention will be described.

  In this device, a conductive layer (surface property control layer) corresponding to at least one of the above a) to d) is disposed between the substrate and the tunnel layer.

  The layer composed of the predetermined element corresponding to a) functions as a surfactant layer, and has an effect of improving the surface properties of the tunnel layer. The layer (amorphous or microcrystalline) corresponding to b) or c) has the effect of suppressing the roughness of the film formed on this layer and the pinhole of the tunnel layer. The laminate corresponding to d) also improves the roughness and the like of a film formed on the laminate. By these actions, the surface property control layer suppresses the variation in the resistance of the tunnel layer which is miniaturized particularly to the submicron size, and further suppresses the increase in the coercive force due to the orange peel effect.

  When the surface property control layer is at least one selected from a), b) and c), the thickness of this layer is preferably 10 nm or less. This is because the influence of a demagnetizing field in a submicron-sized element can be suppressed. The thickness of the surface property control layer is preferably 0.5 nm or more in order to further suppress the roughness.

  The surface property control layer may be a magnetic layer (magnetic conductive layer) or a non-magnetic layer (non-magnetic conductive layer), and the conductor corresponding to a) is a non-magnetic layer, and c) is a non-magnetic layer. The corresponding microcrystal is preferably a magnetic layer.

  The magnetic conductive layer corresponding to b) or c) includes, for example, a magnetic material mainly composed of at least one selected from Fe, Co, and Ni, and a group of Al, Si, Ga, Ge, and IIa (in the new IUPAC display). Addition of at least one element selected from Group 2) and VIa (Group 6) and at least one element selected from B, C, N, O and P facilitates fabrication. Here, the preferable content of B, C, N, O and P is 10 to 30 atomic%. Here, the main component refers to the element having the largest content among the contained elements.

  In the layer corresponding to d), as the metal film laminated with the Cu film, a metal film having a lattice constant different from the Cu film by 10% or more or a metal film having a crystal structure different from the Cu film is preferable. The preferable thickness of the Cu film is 2 nm or more and 100 nm or less, the preferable thickness of the metal film other than Cu is 0.3 nm or more and 5 nm or less, and the preferable total thickness of the laminate is 50 nm or more and 5 μm or less. This laminate may be used as a lower electrode or a part of a lower electrode.

  The surface property control layer which is a magnetic layer may constitute a part of the magnetic layer. In this case, the surface property control layer is included in the magnetic layer (the magnetic layer 6 in FIG. 1) disposed on the substrate side (the lower part in FIG. 1).

  Usually, the magnetic layer is a layer other than any of a) to d), but the magnetic layer may also serve as a surface property control layer. The magnetic layer provided separately from the surface property control layer may be any one selected from an amorphous magnetic material and a microcrystalline magnetic material having an average crystal grain of 5 nm or less. In this mode, the MR ratio may slightly decrease, but the variation in the junction resistance value decreases.

  As shown in FIG. 2, the surface property control layer 2 may be arranged separately from the magnetic layer 6. In this case, the surface property control layer 2 does not need to be disposed in contact with the magnetic layer 6, and as shown in FIG. 3, the substrate 1 and the magnetic layer (not the side 9 opposite to the substrate 1 as viewed from the tunnel layer 7). 6 as long as it is included in the multilayer film 10 so as to be interposed at the position 5 between them. The surface property control layer, which is a magnetic layer, may be a high coercive force layer or a soft magnetic layer magnetically in contact with the magnetic layer 6 disposed on the substrate side.

  If this TMR element is used, stable junction resistance can be easily obtained even if a polycrystalline substrate having many pinholes and relatively large roughness, such as a ceramic polycrystalline substrate, is used.

(Embodiment 2)
Next, the second TMR element of the present invention will be described.

  In this element, at least one of the magnetic layers has at least one selected from the group consisting of e) a predetermined lattice strain, f) a crystal structure (crystal system) that is not formed preferentially at normal temperature and pressure, and g) a crystal orientation plane other than a fine plane. One type is introduced, so that a higher MR ratio can be obtained.

  In order to introduce at least one of e) to g) into the magnetic layer, for example, a crystal structure control layer may be disposed so as to be in contact with the magnetic layer. As shown in FIG. 2, the crystal structure control layer 2 is preferably formed so as to be in contact with the magnetic layer 6 for introducing lattice distortion or the like. The magnetic layer and the crystal structure control layer may be formed by epitaxially growing the other on either one.

  When introducing a lattice distortion, the crystal structure control layer is preferably formed so as to have a lattice mismatch with a fine crystal plane of a crystal system preferentially formed in the magnetic layer. When the crystal system or the orientation is controlled, it is preferable to form the crystal system such that the lattice mismatch with respect to a plane other than the fine crystal plane is relatively small.

  It is considered that when an appropriate lattice strain corresponding to e) is introduced into the magnetic layer, the spin polarizability near the Fermi surface increases and the MR ratio improves.

The crystal structure control layer for introducing lattice strain is a magnetic element (at least one selected from Fe, Co, and Ni) included in the magnetic layer for introducing lattice distortion, and a material other than these magnetic elements (Fe, Co, and Ni). (Non-magnetic element). For example, when the magnetic layer that introduces lattice distortion is made of a magnetic element M, the crystal structure control layer preferably has M _1-x A _x (A is an element other than the magnetic element; 0 <x <1).

  f) Even if a crystal structure different from the crystal structure that can be preferentially obtained under normal temperature and normal pressure is introduced into the magnetic layer, the MR ratio is improved.

  Under normal temperature and normal pressure, for example, Fe preferentially takes a crystal structure of bcc (body-centered cubic lattice), Co takes hcp (hexagonal close-packed lattice), and Ni takes a crystal structure of fcc (face-centered cubic lattice) preferentially. However, when a magnetic layer having a metastable crystal structure such as fcc-Fe, bcc-Co, and bcc-Ni is used, a higher MR ratio can be obtained.

Similarly, an FeCo alloy (eg, Fe ₅₀ Co ₅₀ ) having a composition that preferentially has a bcc structure may be hcp or fcc. An FeCo alloy (eg, Fe ₁₀ Co ₉₀ ) having a composition that preferentially has an hcp or fcc structure is bcc, and a NiFe alloy having a composition that preferentially has an fcc structure may have a bcc structure.

  According to the study by the inventors, it is preferable that these metastable crystal structures account for 30% or more of the entire crystal structure of the magnetic layer from the viewpoint of improving the MR ratio. Further, even in a magnetic layer in which a non-magnetic element is added to a magnetic element, the effect of improving the MR ratio by introducing a metastable crystal structure can be similarly obtained.

  In many cases, lattice distortion is likely to be simultaneously introduced into a metastable crystal structure. At this stage, it is difficult to separately and clearly explain the effects of the change in crystal structure and the effects of lattice distortion. However, in any case, it is considered that the increase in the spin polarizability due to the change in the band structure accompanying the change in the crystal structure contributes to the improvement in the MR ratio.

  g) Even if a polycrystalline material having a controlled crystal orientation plane other than the fine plane is introduced into the magnetic layer, the MR ratio is improved.

  The magnetic layer has an MR ratio when the component other than the fine surface increases, such as the (111) orientation component when the crystal orientation plane is bcc and the (100) or (110) component when the crystal orientation plane is fcc. growing. Specifically, for example, when it is confirmed by X-ray diffraction that the orientation is other than the fine surface, the MR ratio tends to increase.

  When at least f) and g) are simultaneously introduced into the magnetic layer, a higher MR ratio is obtained. If e) is introduced together with f) and g), a higher MR ratio may be realized.

  In this device, the thickness of the magnetic layer into which at least one of e) to g) is introduced is preferably 3 nm or less.

(Embodiment 3)
Subsequently, the third element of the present invention will be described.

In a magnetic layer made of an alloy of magnetic elements (Fe, Co, and Ni), the highest spin polarizability is obtained in the vicinity of Fe ₇₀ Co ₃₀ . When converted to an average number of electrons, Fe ₇₀ Co ₃₀ corresponds to 26.3 (atomic number of Fe: 26, atomic number of Co: 27; 26 × 0.7 + 27 × 0.3 = 26.3). However, in a magnetic layer containing at least one magnetic element and at least one nonmagnetic element, the MR ratio is improved when the average number of electrons is 23.5 or more and 25.5 or less or 26.5 or more and 36 or less. I do.

  According to the results confirmed in Examples described later, the more preferable average electron number is 24.5 or more and 25.5 or less or 27.5 or more and 32.5 or less. This magnetic layer preferably contains a magnetic element as a main component. Here, the total amount of the magnetic elements may be larger than the total amount of the non-magnetic elements.

  There is no limitation on the applicable non-magnetic element within the range confirmed by the present inventors. Preferred non-magnetic elements include, for example, at least one selected from Si, Al, Ti, V, Cr, Mn, Ru, Rh, Pd, Os, Ir, Pt, B, C, N and O.

(Embodiment 4)
Finally, a fourth device of the present invention will be described.

  This device includes a surplus element trapping layer. The surplus element is an element in which an increase in the concentration in the magnetic layer causes a decrease in the spin polarizability in the magnetic layer, and for example, at least one selected from Mn, Ru, B, C, N, and O corresponds. The surplus element diffuses from the surplus element supply layer to the entire device and to the magnetic layer during the heat treatment in the device manufacturing process. As a result, the spin polarizability of the magnetic layer decreases.

  The surplus element in the magnetic layer may raise the MR ratio of the magnetoresistive element due to a factor different from the spin polarizability.

  Before capturing the surplus element, the surplus element capturing layer preferably contains a metal that forms an alloy or a compound with the surplus element, and after capturing the surplus element, an alloy or a compound containing the surplus element is used. Contains.

  When the tunnel layer is at least one selected from borides, carbides, nitrides, and oxides, at least one selected from B, C, N, and O can be a surplus element. In this case, the surplus element capturing layer preferably contains a metal having a free energy of formation of at least one compound selected from oxides, nitrides, carbides, and borides lower than Fe. Examples of such a metal include at least one selected from the group consisting of Al, Si, a group IVa (group 4), a group Va (group 5), and a group VIa (group 6).

  Excess elements may diffuse from the magnetization rotation suppressing layer in the spin valve type element. A typical surplus element contained in the magnetization rotation suppressing layer is at least one selected from Mn and Ru. Mn diffuses, for example, from an antiferromagnetic layer containing Mn, and Ru diffuses, for example, from a nonmagnetic film containing Ru. This nonmagnetic film can be used as a part of a laminated ferrimagnetic (magnetic film / Ru / magnetic film laminated structure). This laminated ferri-layer may be used not only as a magnetization rotation control layer but also as a magnetic layer itself in a TMR element. In order to capture a surplus element from the magnetization rotation control layer, the surplus element capturing layer preferably contains at least one metal selected from Fe, Ni, Ir, Pd, and Pt.

  The surplus element diffuses from a surplus element supply layer such as a tunnel layer and a magnetization rotation control layer to another layer. After the diffusion, it is preferable that the relational expression of Rs ≧ Rc> Rm holds for the content (concentration) of the surplus element in each layer. Here, Rs is the surplus element content in the surplus element supply layer, Rc is the surplus element content in the surplus element capture layer, and Rm is the surplus element content in the magnetic layer.

  As shown in FIG. 4, the surplus element trapping layer 21 is arranged such that the distance L between the layer and at least one of the magnetic layers (the magnetic layer 8 in FIG. 4) is 10 nm or less in the thickness direction of the multilayer film. It is preferable to arrange them. This is because it is effective for reducing the concentration of surplus elements in the magnetic layer.

  The following is a description of an embodiment common to each element.

  In these elements, for example, at least one of the magnetic layers may contain at least one element selected from B, C, N, O, and P in a range of 0.1 atomic% to 15 atomic%. . This is because it is effective in introducing lattice distortion, controlling the crystal orientation plane, adjusting the average number of electrons, and the like. Further, for example, at least one of the magnetic layers may contain at least one element selected from Mn and a platinum group element in a range of 0.1 at% to 40 at%.

  For the production of these elements, various conventionally known film forming methods such as vacuum evaporation, IBD (ion beam deposition), sputtering, MBE, and ion plating may be applied.

  The tunnel layer may be formed by a sputtering method using a compound target, or a reactive deposition method, a reactive sputtering method, ion assist, or the like may be applied. A CVD method (chemical vapor deposition method) may be used. Further, the metal film may be formed by contacting with a gas having an appropriate partial pressure including a reaction gas or a plasma atmosphere.

  These films may be processed by a physical or chemical etching method such as ion milling, RIE, EB, FIB, I / M, or the like, which is used in a normal semiconductor process, and a photography method. If planarization is required during the fine process, a CMP method or a cluster ion beam etching method may be applied.

  The magnetoresistive element of the present invention can be applied to various magnetic devices. FIG. 5 shows a configuration example when applied to a magnetic head using the free layer 18 as a yoke. On a substrate 11, a lower electrode 13, a control layer 12, an antiferromagnetic film 14, a fixed magnetic layer 16, a tunnel layer 17, a free magnetic layer 18, and an upper electrode 20 are laminated in this order. As the control layer 12, for example, a surface property control layer in the first element and a crystal structure control layer in the second element may be used.

  In this device, a pair of electrodes 13 and 20 are arranged so as to sandwich the magnetic layers 16 and 18 and the tunnel layer 17, and the interlayer insulating film 15 is formed so that all the current flowing between these electrodes passes through the tunnel layer 17. Is arranged. Reference numeral 19 denotes a hard magnetic film or an antiferromagnetic film.

(Example 1)
In this example, a first element of the present invention was manufactured.

  A multilayer film having the following configuration was formed on a polycrystalline AlTiC substrate by using RF magnetron sputtering and an evaporation method using resistance heating.

Ta (3) / Cu (500) / Surface control layer (10) / Ta (3) / PtMn (30) / CoFe (3) / Ru (0.7) / CoFe (3) / Al (0.4; 200Torr Pure oxygen 1min oxidation) / Al (0.3; 200Torr pure oxygen 1min oxidation) / CoFe (3) / NiFe (5) / Ta (3)
However, each layer is described in order from the substrate side, the numerical value in parentheses is the film thickness of each layer in units of nm, and the oxidation conditions of Al are also shown in parentheses (the same applies hereinafter).

  After this film was mesa-processed, Ta was removed by milling, and a film of NiFe (5) / CoPt (30) was formed, and a film of Cu (500) was formed on the final surface except for CoPt immediately above the mesa structure. Thus, an element having a structure similar to that of FIG. 5 was manufactured.

  In order to impart uniaxial anisotropy, PtMn is heat-treated at 280 ° C. in a magnetic field of 5 kOe (approximately 398 kA / m). Heat treatment was applied.

Further, instead of the Cu (500) / surface property control layer (10) in the multilayer film, a laminate in which ten two-layer structures of Cu (50) and the surface property control layer (0.5 or 2.5) were used was used. Except for the above, an element was produced in the same manner as described above. An element was manufactured in the same manner as described above, except that a Si thermal oxidation substrate (Si / SiO ₂ ) was used instead of the polycrystalline AlTiC substrate. For comparison, an element without the surface property control layer was also manufactured.

  For each element, variations in MR ratio, coercive force, and junction resistance were measured. The variation in the junction resistance was measured at 30 points on a 6-inch wafer, and the standard deviation σ was adopted. Table 1 shows the results.

 Here, as the surface property control layer made of Au, a layer formed at room temperature and then heat-treated at 500 ° C. and a layer formed at room temperature and not heat-treated are described. For the other surface property control layers, the layers that were not heat-treated were described. Among the elements corresponding to a), Pt and Pd are preferably formed at room temperature and not heat-treated, while Au is preferably heat-treated at 400 ° C. or higher after film formation, and any of the remaining elements may be used.

  TiSi, ZrAlNiCu, ZrNbAlCu, and CuSiB are amorphous non-magnetic films, CoFeB is an amorphous magnetic film, and FeSiB is a magnetic film having an average crystal grain of 5 nm or less.

  From other experiments, as a metal film alternately stacked with a Cu film, a metal film having a lattice constant different from the Cu film by 10% or more or a metal film having a crystal structure different from the Cu film is particularly effective. Was. It was also confirmed that the use of a metal having a solid solution rate of 10% or less with Cu was more effective. Cr is an example of a metal film satisfying these conditions. Although Pt forms a solid solution on the phase diagram, good results are obtained because the diffusion coefficient for Cu is relatively small.

  Further, an element was manufactured using a CoFeB film or a FeSiNb film instead of the CoFe film on the substrate side in the same film configuration as described above. In these devices, the MR ratio was reduced to 16% and 17%, respectively, but the variation in the junction resistance was 5% and 6%, respectively. The coercive force of both elements was 10 Oe.

  As a result of observation using an AFM (atomic force microscope), it was confirmed that the roughness of the multilayer film was suppressed by the surface property control layer.

(Example 2)
(Example 2-1)
Using RF magnetron sputtering, a multilayer film having the following configuration was formed on a Si substrate with a thermal oxide film.

Ta (3) / Cu (500) / Ta (3) / crystal structure control layer (10) / Fe (3) / Al (0.4; 200 Torr pure oxygen 1 min oxidation) / Al (0.3; 200 Torr pure oxygen 1 min oxidation) / CoFe (3) / Ru (0.7) / CoFe (3) / PtMn (30) / Ta (3)
Further, in the same manner as in Example 1, the device shown in FIG. 6, the reference numerals are the same as those in FIG.

First, a crystal structure controlling layer, Fe _1-x Si _x (110) using the alignment (0 <x <1), by changing the spacing of (110) plane by adjusting the Si amount, Fe on this Lattice strain was introduced into the film. The MR ratio of each device was measured. Table 2 shows the results.

  Here, the elongation of the lattice constant was calculated from the measured value of the lattice constant of the Fe film measured by X-ray diffraction and RHEED (reflection high-speed electron diffraction), and the lattice constant calculated from the crystal structure.

(Example 2-2)
A multilayer film having the following configuration was formed on a glass substrate by using RF magnetron sputtering.

Ta (3) / Cu (500) / Ta (3) / crystal structure control layer (10) / CoFe (3) / Al (0.4; 200 Torr pure oxygen 1 min oxidation) / Al (0.3; 200 Torr pure oxygen 1 min oxidation) / CoFe (3) / Ru (0.7) / CoFe (3) / PtMn (30) / Ta (3)
Further, a device similar to that of FIG. 6 was produced in the same manner as in Example 1.

Here, as the crystalline structure control layer, using a _{Fe 1-x Al x (110} ) orientation (0 <x <1), by adjusting the Al content was introduced lattice distortion CoFe film thereon. The MR ratio of each device was measured. Table 3 shows the results.

(Example 2-3)
A multilayer film having the following configuration was formed on a Cu single crystal substrate using RF magnetron sputtering.

Cu (500; crystal structure control layer) / Fe (5ML) / Al (0.4; 200 Torr pure oxygen 1 min oxidation) / Al (0.3; 200 Torr pure oxygen 1 min oxidation) / CoFe (3) / Ru (0.7) / CoFe (3 ) / PtMn (30) / Ta (3)
Here, 5ML means that five basic lattices are stacked. The Fe film having this thickness was polycrystalline.

  Further, a device similar to that of FIG. 6 was produced in the same manner as in Example 1. In this device, the substrate and the crystal structure control layer also serve as the lower electrode. Here, the orientation of the Cu single crystal was changed to change the crystal structure of Fe.

  Further, an element was manufactured in the same manner as described above except that an MgO single crystal substrate or a Si substrate with a thermal oxide film was used instead of the Cu single crystal substrate, and a Pt film was used as the crystal structure control layer instead of the Cu film.

  For these devices, the MR ratio was measured. Further, the orientation ratio of the Fe film was measured. Here, the orientation ratio was measured by a ratio of peak heights by an X-ray lattice diffraction method. The orientation ratio is the ratio of the area at the interface of the crystal plane. Strictly speaking, the value observed by X-rays and the orientation ratio at the barrier interface are not necessarily the same, but within the range of this embodiment, a good correlation between the orientation ratio measured by the X-ray diffraction method and the MR ratio is obtained. Indicated. Table 4 shows the results.

  In an element having a crystal structure other than the structure (bcc) in which the Fe film is preferentially formed at normal temperature and normal pressure, the MR ratio is improved. A higher MR ratio was obtained for hcp-Fe than for bcc-Fe. In the fcc-Fe film, a higher MR ratio was obtained when the crystal orientation was other than the fine plane (111).

  Similarly, when an fcc-Co film or a bcc-Ni film is formed instead of the fcc-Fe film, the same or higher than the hcp-Co film or the fcc-Ni film formed preferentially. An MR ratio was obtained. Also in these films, higher MR ratios were obtained in directions other than the fine plane.

  From other experiments, it was confirmed that the orientation ratio other than the fine surface is preferably 60% or more, particularly preferably 80% or more, for improving the MR ratio.

(Example 2-4)
Using RF magnetron sputtering, a multilayer film having the following configuration was formed on a Si substrate with a thermal oxide film.

Cu (100) / CuAu (500; crystal structure control layer) / Fe (5ML) / Al (0.4; 200 Torr pure oxygen 1 min oxidation) / Al (0.3; 200 Torr pure oxygen 1 min oxidation) / CoFe (3) / Ru (0.7 ) / CoFe (3) / PtMn (30) / Ta (3)
Further, a device similar to that of FIG. 6 was produced in the same manner as in Example 1.

Here, Cu _1-x Au _x (110) orientation (0 <x <1) is used as the crystal structure control layer, and by adjusting the amount of Au, lattice distortion is caused in the fcc-Fe (100) film thereon. Was introduced. The MR ratio of each device was measured. Table 5 shows the results.

  In the metastable crystal, the MR ratio was improved by introducing lattice distortion.

  In addition, also when the crystal structure control layer was disposed in contact with the magnetic layer far from the substrate, it was confirmed that the MR ratio was improved in the same manner as described above.

(Example 3)
Using RF magnetron sputtering, a multilayer film having the following configuration was formed on a Si substrate with a thermal oxide film.

Ta (3) / Cu (500) / Ta (3) / magnetic layer (3) / Al (0.4; 200 Torr pure oxygen 1 min oxidation) / Al (0.3; 200 Torr pure oxygen 1 min oxidation) / CoFe (3) / Ru ( 0.7) / CoFe (3) / PtMn (30) / Ta (3)
The magnetic layer having a thickness of 3 nm was composed mainly of Fe, and the composition was adjusted by adding an additive element to a target or introducing a reactive gas. Further, a device similar to that of FIG. 6 was produced in the same manner as in Example 1.

  The MR ratio of each device was measured. The MR ratio was normalized by setting the maximum value to 1.0. Table 6 shows the results.

  From Table 6, when a nonmagnetic or diamagnetic element was added to the magnetic metal, the MR ratio showed a maximum value in two regions. This phenomenon was confirmed not only in Fe but also in NiMn alloy, FeCo alloy, NiFeCo alloy and the like. In addition, the same result was obtained not only for the additive elements described above but also for Ti, V, Mn, Ru, Os, Pd, O, C, and B. FeCr having an average number of electrons of 24.5 did not contain a magnetic element (Fe) as a main component, and thus had a low MR ratio.

(Example 4)
(Example 4-1)
Using RF magnetron sputtering, a multilayer film having the following configuration was formed on a Si substrate with a thermal oxide film.

Cu (500) / Excess element trapping layer (1-20) / NiFe (5) / CoFe (1.5) / Al (0.4; 600 Torr pure oxygen 1 min oxidation) / Al (0.3; 600 Torr pure oxygen 1 min oxidation) / CoFe (3 ) / Ru (0.7) / CoFe (3) / PtMn (30) / Ta (3)
Further, a device similar to that of FIG. 6 was produced in the same manner as in Example 1. However, the maximum temperature of the heat treatment was 260 ° C. The MR ratio of each element thus obtained was measured. Table 7 shows the results.

  When the light element in the magnetic layer after the heat treatment was examined by RBS (Rutherford back scattering), the CoFe film was oxidized in the element in which the surplus element trapping layer was the Fe film. In the device in which the surplus element trapping layer was an FeR film (R is a metal having higher oxygen affinity than Fe; each element other than Fe in Table 7), a peak of the oxygen element was confirmed in the surplus element trapping layer. In these devices, the excess element trapping layer contained oxygen at a lower concentration than the tunnel layer and a higher concentration than the magnetic layer.

(Example 4-2)
Using RF magnetron sputtering, a multilayer film having the following configuration was formed on a Si substrate with a thermal oxide film.

Cu (500) / NiFe (5) / CoFe (1.5) / Al (0.4; 600 Torr pure oxygen 1 min oxidation) / Al (0.3; 600 Torr pure oxygen 1 min oxidation) / CoFe (3) / Ru (0.7) / CoFe (1.5 ) / Surplus element trapping layer A (0.5-2) / CoFe (1.5) / PtMn (30) / surplus element trapping layer B (1-5) / Ta (3)
Further, a device similar to that of FIG. 6 was produced in the same manner as in Example 1. However, the maximum temperature of the heat treatment was 350 ° C. The MR ratio of each element thus obtained was measured. Table 8 shows the results.

  Analysis by SIMS and Auger confirmed that Mn contained in the PtMn film was diffused. In the device in which the excess element capturing layers A and B were not formed, the Mn concentration in the magnetic layer (CoFe film) was higher than the Mn concentration in the uppermost Ta film.

  On the other hand, in the element in which the surplus element trapping layer was formed, the Mn concentration in the magnetic layer was lower than the Mn concentration in the surplus element trapping layer. Further, the Mn concentration in the magnetic layer decreased due to the formation of the surplus element capturing layer. The Mn concentration of the magnetic layer in the device in which the surplus element trapping layer A was formed was lower than the Mn concentration in the device in which the surplus element trapping layer B was formed. The surplus element trapping layer is preferably disposed between the surplus element supply layer (antiferromagnetic layer) and the tunnel layer.

FIG. 1 is a cross-sectional view illustrating a basic configuration of a magnetoresistive element of the present invention. FIG. 2 is a cross-sectional view illustrating an embodiment in which a control layer is added to the basic configuration of FIG. 1. FIG. 3 is a cross-sectional view for explaining a preferred arrangement of a control layer. It is sectional drawing for demonstrating the preferable arrangement | positioning of a surplus element capture layer. FIG. 3 is a cross-sectional view illustrating one embodiment of the magnetoresistive element of the present invention. It is sectional drawing which shows another one form of the magnetoresistive element of this invention.

Claims (37)

A substrate, and a multilayer film formed on the substrate, wherein the multilayer film includes a tunnel layer and a pair of magnetic layers sandwiching the tunnel layer, and a relative angle of a magnetization direction in the pair of magnetic layers. A magnetoresistive element whose resistance value changes according to
A magnetoresistive element, wherein a conductive layer is disposed between the substrate and the tunnel layer, and the conductive layer is a microcrystalline film having an average crystal grain size of 5 nm or less. 2. The magnetoresistive element according to claim 1, wherein the conductive layer is a non-magnetic film. 2. The magnetoresistive element according to claim 1, wherein the conductive layer is a magnetic film. The magnetoresistive element according to claim 1, wherein the average thickness of the conductive layer is 10 nm or less. The magnetoresistive element according to claim 1, wherein the substrate is a polycrystalline body. A substrate, and a multilayer film formed on the substrate, wherein the multilayer film includes a tunnel layer and a pair of magnetic layers sandwiching the tunnel layer, and a relative angle of a magnetization direction in the pair of magnetic layers. A magnetoresistive element whose resistance value changes according to
At least one of the pair of magnetic layers has e) a lattice strain represented by a lattice constant difference different from 0.1% to 5% with respect to a lattice constant calculated from the crystal structure, and f) priority at normal temperature and normal pressure. A magnetoresistive element having at least one selected from the group consisting of a crystal structure different from the crystallographically formed structure and g) a polycrystalline structure having a controlled crystal orientation plane other than the fine plane. The multilayer film further includes a crystal structure control layer disposed so as to be in contact with a magnetic layer having at least one selected from e), f) and g), and the e), f) 7. The magnetoresistive element according to claim 6, wherein at least one selected from the group consisting of g) and g) is introduced into the magnetic layer. The magnetic layer having at least e) includes at least one element selected from Fe, Co, and Ni, and the crystal structure control layer includes the at least one element and elements other than Fe, Co, and Ni. A magnetoresistive element according to claim 7. 7. The magnetoresistive element according to claim 6, wherein the multilayer film includes a magnetic layer having at least f) and g). The magnetoresistive element according to claim 9, wherein the multilayer film includes a magnetic layer having e), f) and g). A substrate, and a multilayer film formed on the substrate, wherein the multilayer film includes a tunnel layer and a pair of magnetic layers sandwiching the tunnel layer, and a relative angle of a magnetization direction in the pair of magnetic layers. A magnetoresistive element whose resistance value changes according to
At least one of the pair of magnetic layers contains at least one element selected from Fe, Co, and Ni, and an element other than Fe, Co, and Ni, and has an average number of electrons of 23.5 or more and 25.5 or less. A magnetoresistive element.
Here, the average number of electrons is the number of electrons per atom calculated from the composition ratio. Claims wherein the element other than Fe, Co and Ni is at least one selected from Si, Al, Ti, V, Cr, Mn, Ru, Rh, Pd, Os, Ir, Pt, B, C, N and O. Item 12. The magnetoresistive element according to item 11. The magnetoresistive element according to claim 11, wherein the average number of electrons is 24.5 or more and 25.5 or less. A substrate, and a multilayer film formed on the substrate, wherein the multilayer film includes a tunnel layer and a pair of magnetic layers sandwiching the tunnel layer, and a relative angle of a magnetization direction in the pair of magnetic layers. A magnetoresistive element whose resistance value changes according to
When the concentration of at least one layer other than the pair of magnetic layers and included in the multilayer film in at least one of the pair of magnetic layers increases, the spin polarizability of the at least one layer decreases. Including surplus elements,
The multilayer film further includes a surplus element capturing layer including an alloy or a compound containing the surplus element,
A magnetoresistive element having a surplus element content higher in the surplus element trapping layer than in any of the pair of magnetic layers. The magnetoresistive element according to claim 14, wherein the multilayer film includes a surplus element supply layer, and a surplus element content in the surplus element supply layer is equal to or higher than the content rate in the surplus element capture layer. The magnetoresistive element according to claim 15, wherein the surplus element supply layer is a tunnel layer, and the surplus element is at least one selected from B, C, N, and O. 17. The magnetoresistive element according to claim 16, wherein the surplus element trapping layer contains a compound of a metal selected from oxides, nitrides, carbides, and borides, the free energy of formation of which is lower than Fe. The magnetoresistive element according to claim 15, wherein the surplus element supply layer is at least one selected from an antiferromagnetic layer and a laminated ferrimagnetic layer. The magnetoresistive element according to claim 18, wherein the surplus element is at least one selected from Mn and Ru. The magnetoresistive element according to claim 14, wherein a distance between the surplus element trapping layer and at least one of the pair of magnetic layers is 10 nm or less in a thickness direction of the multilayer film. A substrate, and a multilayer film formed on the substrate, wherein the multilayer film includes a tunnel layer and a pair of magnetic layers sandwiching the tunnel layer, and a relative angle of a magnetization direction in the pair of magnetic layers. A magnetoresistive element whose resistance value changes according to
A magnetoresistive element in which a conductive layer is disposed between the substrate and the tunnel layer, and the conductive layer is a laminate including a multilayer film in which a Cu film and a metal film other than Cu are alternately laminated. 22. The magnetoresistive element according to claim 21, wherein the conductive layer is a non-magnetic film. 22. The magnetoresistive element according to claim 21, wherein the conductive layer is a magnetic film. 22. The magnetoresistive element according to claim 21, wherein the substrate is a polycrystalline body. A substrate, and a multilayer film formed on the substrate, wherein the multilayer film includes a tunnel layer and a pair of magnetic layers sandwiching the tunnel layer, and a relative angle of a magnetization direction in the pair of magnetic layers. A magnetoresistive element whose resistance value changes according to
A conductive layer is disposed between the substrate and the tunnel layer, and the conductive layer is a conductor made of at least one selected from Pt, Pd, Ag, Au, C, Si, Ge, Sn, and Pb. Magnetic resistance element. 26. The magnetoresistive element according to claim 25, wherein the conductive layer is a non-magnetic film. The magnetoresistive element according to claim 25, wherein the conductive layer is a magnetic film. The magnetoresistive element according to claim 25, wherein the average thickness of the conductive layer is 10 nm or less. The magnetoresistive element according to claim 25, wherein the substrate is a polycrystalline body. A substrate, and a multilayer film formed on the substrate, wherein the multilayer film includes a tunnel layer and a pair of magnetic layers sandwiching the tunnel layer, and a relative angle of a magnetization direction in the pair of magnetic layers. A magnetoresistive element whose resistance value changes according to
A magnetoresistive element, wherein a conductive layer is disposed between the substrate and the tunnel layer, and the conductive layer is an amorphous film. 31. The magnetoresistive element according to claim 30, wherein the conductive layer is a non-magnetic film. 31. The magnetoresistive element according to claim 30, wherein the conductive layer is a magnetic film. 31. The magnetoresistive element according to claim 30, wherein the average thickness of the conductive layer is 10 nm or less. 31. The magnetoresistive element according to claim 30, wherein the substrate is a polycrystalline body. A substrate, and a multilayer film formed on the substrate, wherein the multilayer film includes a tunnel layer and a pair of magnetic layers sandwiching the tunnel layer, and a relative angle of a magnetization direction in the pair of magnetic layers. A magnetoresistive element whose resistance value changes according to
At least one of the pair of magnetic layers contains at least one element selected from Fe, Co, and Ni, and an element other than Fe, Co, and Ni, and has an average number of electrons of 26.5 or more and 36 or less. Magnetic resistance element.
Here, the average number of electrons is the number of electrons per atom calculated from the composition ratio. Claims wherein the element other than Fe, Co and Ni is at least one selected from Si, Al, Ti, V, Cr, Mn, Ru, Rh, Pd, Os, Ir, Pt, B, C, N and O. Item 36. The magnetoresistive element according to item 35. The magnetoresistive element according to claim 35, wherein the average number of electrons is 27.5 or more and 32.5 or less.

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