JP2000174359A - Reluctance element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain significant in-plane reluctance variation by composing the magnetic film of a reluctance element of a composite perovskite oxide composed of specified elements, thereby enhancing the spin polarization rate. SOLUTION: A lower magnetic film 2 of Sr2FeReO6 is deposited on an SrTiO3 substrate 1 through RF sputtering and an upper magnetic film 4 of Sr2FeReO6 is deposited thereon through an SrTiO3 insulation layer 3. These magnetic films 3, 4 are composed of a composite perovskite oxide shownby A2+xtm'1+yTM '1+zO6-δ. In the formula, A is one kind selected from among Ca, Sr, Ba, tm' is one kind selected from among Mn, Ni, Co, Cr, Mg, and TM' is Re, δ is oxygen deficiency, and -0.2<x<0.2, -0.2<y<0.2, -0.2<z<0.2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetoresistive element utilizing a change in magnetoresistance when a magnetic field is applied to a magnetic film.

[0002]

2. Description of the Related Art At present, a magnetoresistive element utilizing a magnetoresistance, in particular, a giant magnetoresistance, has an in-plane magnetoresistance change due to a laminated film of a metal magnetic material / metal nonmagnetic material and a laminated film of a metal magnetic material / insulator. There are a GMR (Giant magneto resistive) element and a TMR (Tunneling magneto resistive) element utilizing a magnetoresistance change due to a spin-polarized tunnel effect, and are mainly applied to a magnetic head. Furthermore, MRA utilizing the magnetoresistance change due to the above-mentioned laminated film
M (Magneto resistive random access memory) and the like are being studied.

However, metal magnetic materials used in these conventional magnetoresistive elements, for example, Fe, Ni, C
Since o, permalloy, and the like originally have a low spin polarization, there is a problem that a change in in-plane magnetoresistance or a magnetoresistance change due to a spin polarization tunnel effect due to application of a magnetic field cannot be obtained. There is also a problem that the resistivity itself is too small.

[0004] In order to solve these problems, it has been proposed to use a so-called semimetal for the magnetic material to be used. Since the semimetal has a high spin polarization and a high original resistivity, it can provide performance that is easy to use as a magnetoresistive element. The semi-metal here is doped La
A conductive perovskite oxide having magnetism such as MnO ₃ may be used.

However, these conductive perovskite oxides generally have a problem that the magnetic transition point (Tc) is low. For example, there is a problem that the magnetic transition point of the LaMnO ₃ system is just above room temperature and cannot be applied to an actual magnetoresistive element. On the other hand, as a substance having a high resistivity and a high magnetic transition point, there is a conductive magnetic oxide such as magnetite Fe ₃ O ₄ or a derivative thereof, and proposals have been made to use these for a magnetoresistive element.

However, the electric conduction in these substances is of a thermally activated type of localized electrons, and the in-plane magnetoresistance change of the magnetic substance itself is small. In addition, the magnetoresistance change due to the spin-polarized tunnel effect in the laminated film of the magnetite Fe ₃ O ₄ and the insulating film is different from the case of using the usual metallic magnetic material, and both the spatially localized up spin and down spin are different. There is a problem that a large change due to the application of a magnetic field cannot be obtained because the contribution of the magnetic field is simultaneously observed.

[0007]

As described above, as described above, the spin polarization ratio is high, a large in-plane magnetoresistance change or a magnetoresistance change caused by a spin polarization tunnel is exhibited, and a high magnetic transition point is obtained. A magnetic material having an appropriate resistivity has not yet been obtained, and a magnetoresistive element having good magnetoresistance characteristics in a practical temperature range centered on room temperature has not been obtained.

The present invention has been made in view of the above problems, has a high spin polarization rate, shows a large in-plane magnetoresistance change and a magnetoresistance change due to a spin polarization tunnel, and has a high magnetic transition point. Using a magnetic film with an appropriate resistivity,
It is an object of the present invention to provide a magnetoresistive element having good magnetoresistance characteristics in a practical temperature range centered on room temperature.

[0009]

According to the present invention, in a magnetoresistive element having at least a magnetic film, the magnetic film substantially has the general formula (1) A _{2 + x} tm ′ _{1 + y} TM ′ _{1 + z}
O _6−δ (A is at least one kind selected from Ca, Sr, Ba, tm ′ is at least one kind selected from Mn, Ni, Co, Cr, Mg, TM ′ is Re, −0.2 <x <0 .
2, -0.2 <y <0.2, -0.2 <z <0.2, where δ is the amount of oxygen deficiency). In the above magnetoresistive element,
It is desirable to have an insulator film between at least two magnetic films and operate by a spin-polarized tunnel effect between the magnetic films.

Further, according to the present invention, in a magnetoresistive element having at least a magnetic film, the magnetic film may be represented by the general formula (2) A
_{2 + x tm 1 + y TM} 1 + z O 6-δ (A is Ca, S
At least one selected from r and Ba, tm is Fe,
At least one selected from Mn, Ni, Co, Cr, Mg; TM is at least one selected from Mo, Re;
A magnetoresistive element comprising a composite perovskite oxide represented by -0.2 <x <0.2, -0.2 <y <0.2, -0.2 <x <0.2, and δ is the amount of oxygen deficiency), and having lattice distortion. It is. Here, it is desirable that the lattice strain of the magnetic film is obtained by epitaxially growing a composite perovskite oxide on substrates having different lattice constants. Further, it is desirable that the in-plane lattice constant of the magnetic film has a value of 99.5% or less or 100.5% or more of the lattice constant of the bulk material having the same composition. Further, in the above-described magnetoresistive element, it is desirable that an insulator film is provided between at least two magnetic films and the device operates by a spin-polarized tunnel effect between the magnetic films.

Further, the present invention relates to a magnetoresistive element having at least a magnetic film, wherein the magnetic film substantially has the general formula (2) A _{2 + x} tm _{1 +} yTM _{1 + z} O _6-δ (A is C
tm is at least one kind selected from a, Sr, and Ba.
At least one selected from Fe, Mn, Ni, Co, Cr, Mg, TM is at least one selected from Mo and Re, -0.2 <x <0.2, -0.2 <y <0.2, -0.2 <x < (0.2, δ is the amount of oxygen deficiency). A magnetoresistive element characterized in that particles composed of a composite perovskite oxide having magnetism indicated by () are dispersed in an insulator. In the above-described magnetoresistive element, it is desirable to operate by a spin polarization tunnel effect between particles.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS [1] For use in a magnetoresistive element of the present invention
The magnetic film to be used has substantially the general formula (1) A _{2 + x}t
m '_{1 + y}TM '_{1 + z}O_6-δ(A is Ca, Sr, B
at least one selected from a, tm 'is Mn, Ni,
At least one selected from Co, Cr and Mg, TM '
Is Re, -0.2 <x <0.2, -0.2 <y <0.2, -0.2 <Z <0.2, δ is oxygen
Deficiency, the composite perovskite oxide
It is characterized by that.

In the general formula (1), x, y, z, and δ representing the composition deviation and the amount of oxygen deficiency are preferably values close to 0, but may be any values within the above range.

The composite perovskite oxide represented by the general formula (1) has a high spin polarization, shows a large in-plane magnetoresistance change and a magnetoresistance change due to a spin polarization tunnel, and has a high magnetic transition point. In addition, it has the property of having high resistivity while having conductivity. Therefore, when used as a magnetic film of a magnetoresistive element, the magnetoresistive element is
It shows excellent magnetoresistance characteristics in a practical temperature range centered on room temperature.

Among the composite perovskite oxides of the general formula (1), those in which A is Ba, tm 'is Fe, and TM' is Re are ferrimagnetic materials having a Neel point of 334 K and exhibit conductivity. Similarly, those in which A is Sr, tm 'is Fe, and TM' is Re are conductive magnetic oxides having a Neel point of 411K. Since both have a very high spin polarization due to their electronic structures, they have particularly excellent properties as magnetoresistive element materials and are therefore preferable.

[2] Further, the general formula (2) including the composition range represented by the general formula (1) A _{2 + x} tm _{1 + y} TM _{1 + z}
O _6-δ (B is at least one kind selected from Ca, Sr and Ba, and tm is Fe, Mn, Ni, Co, Cr, Mg
At least one selected from Mo and Re; -0.2 <x <0.2, -0.2 <y <0.2, -0.
2 <Z <0.2, δ is an oxygen deficiency), and the composite perovskite oxide has a lattice strain, particularly preferably a lattice strain obtained by epitaxially growing the composite perovskite oxide on a substrate having a different lattice constant. By introducing, the magnetic transition point and the magnetism can be further increased. Further, among the composite perovskite oxides represented by the general formula (2), even if the bulk material is an insulator, conductivity can be generated.

In the general formula (2), x, y, z, and δ representing the composition deviation and the oxygen deficiency are preferably values close to 0, but may be any values in the above range.

For example, in the composite perovskite oxide represented by the general formula (2), A is Ba, tm is Mn, TM
Is a compound of Re (TN = 105K), A is Ba, tm is Co,
TM is a compound of Re (TN = 40K), A is Ba, tm is N
It is known that composite perovskite oxides such as compounds with i and TM of Re (TN = 18K) (in () are the magnetic transition temperature of the bulk material) are insulators in the bulk material. However, conductivity can be obtained due to artificial lattice strain introduced by epitaxial growth on a substrate having a lattice mismatch. The magnetic transition point is also higher than that of the bulk material, and can be used as a magnetic film of a magnetoresistive element.

For example, in the composite perovskite oxide represented by the general formula (2), A is Ba, tm is Mg, T
M is a compound of Re, A is Ba, tm is Co, and TM is Re.
Are bulky non-magnetic insulators, but they can also exhibit conductivity and magnetism due to artificially introduced lattice strain as described above.

The lattice strain introduced into the magnetic film can take an arbitrary value depending on the type of the target device and the operating temperature. However, in order to effectively increase the metallization and the magnetic transition point,
It is desirable that the lattice constant of the magnetic film is changed by 0.5% or more from the lattice constant of the original bulk material. That is, it is desirable that the in-plane lattice constant of the magnetic film has a value of 99.5% or less or 100.5% or more of the lattice constant of the bulk material having the same composition.

In the case of a compound having a sufficiently high magnetic transition point, A is Sr, tm is Fe, and TM is Mo, sufficient characteristics can be obtained even with a small lattice strain. It is necessary to obtain the above-mentioned amount of lattice distortion for a significant increase.

The reason why the compound represented by the general formula (2) can exhibit conductivity even in an insulator due to artificially introduced lattice strain is as follows.

In general, an A ₂ tmTMO ₆ compound (tm is Fe, Co, Mn, Ni or Mg, and TM is Re or Mo) is a reaction between a d electron localized on tm and a d electron localized on TM. This indicates ferromagnetic coupling, and these localized electrons exhibit thermally activated electrical conduction at each site. Here, in the case of A ₂ FeReO ₃ or A ₂ FeMoO ₃ ,
3d unoccupied orbit (minimum energy unoccupied orbit LU)
MO) and the energy of the 5d and 4d occupied orbits (the maximum energy occupied orbital HOMO) of Re and Mo are hybridized to form a band having a finite bandwidth and exhibit conductivity. The conduction electrons involved in this electric conduction have antiparallel spins with other 3d electrons localized on Fe, and the spin polarization of the conduction electrons is very high, close to 1 in effect. I have.

For other insulators, tm unoccupied orbit LUM
Since the energy difference between O and the TM occupied orbital HOMO is large and a hybrid orbital cannot be formed, electrons are considered to be localized on each ion.

However, by giving an appropriate lattice strain by epitaxial growth or the like in which a lattice constant mismatch with an appropriate substrate is set, these tm unoccupied orbits LUMO
Or TM unoccupied orbit HOMO or HOMO and T on tm
It is possible to change the energy of the LUMO on M, and to introduce an appropriate lattice strain to allow hybridization of these orbitals and, thereby, conductivity.

As described above, by utilizing the lattice constant mismatch with the substrate or the like, the bulk material is an insulator A ₂ tmTMO.
Thin film can be obtained that exhibits conductivity at ₆ compounds. At this time, since the transfer of tm electrons and TM electrons increases, a high magnetic transition temperature can be obtained even with a bulk material having a low magnetic transition temperature.

The change in the transfer due to the lattice strain can be used not only to metallize a non-magnetic insulating composite perovskite oxide to make it a magnetic material, but also to use a substance which originally exhibits electric conduction and magnetic order. The magnetic transition point can be raised.

For example, in the bulk material, A having a magnetic transition point of 450 K is Sr, tm is Fe, and TM is Mo. The magnetoresistance effect at room temperature has already been reported. At a temperature higher than room temperature such as ° C., a sufficient magnetoresistance change cannot be obtained. This substance is deposited on a substrate with a lattice mismatch, and lattice distortion is introduced by in-plane compression or expansion of the in-plane lattice constant to obtain a higher magnetic transition temperature and, consequently, a higher magnetoresistance change at a higher temperature. Can also.

Such a change in the physical properties of the oxide due to lattice mismatch with the substrate is caused by BaTiO ₃ or Ba _1-x Sr _x T
This is a well-known phenomenon even for a dielectric such as iO _{3. In} this case, the ferroelectric ordering temperature (Curie point) of the dielectric film can be greatly changed by lattice distortion (Jpn.J.Ap.
pl.Phys., 33, part1, P5297, K. Abe, et al., (1994)).

It is also known that the magnetically conductive perovskite oxide SrRuO ₃ similar to the present invention has a remarkable change in magnetic transition point due to lattice distortion (App.
l.Phys.Lett., 73, P1200, N.Fukushima et al., (1998))
In order to obtain a magnetic film having lattice distortion due to such lattice mismatch, MBE or MOC is applied to a bulk substrate having a lattice constant different from that of the compound represented by the general formula (2).
It can be obtained by forming a film using various film forming methods such as VD, LASER evaporation, and sputtering. In particular, in order to form a relatively thick film without relaxing lattice distortion, it is more effective to form a film by a sputtering method in which the flying particle energy during film formation is relatively large.

In particular, in order to introduce these lattice strains, it is effective to form a film by epitaxial growth on a substrate having a lattice constant different from that of the bulk composite perovskite oxide represented by the general formula (2).

The substrate to be used is, for example, a single crystal substrate such as STO or MgO, or SrTiO ₃ , TiN or Ti on Si.
A film provided with a barrier layer such as _1-x Al _x N, C on Si
A film provided with a barrier layer such as oSi ₂ or Ti _1-x Al _x N, or as an intermediate layer SrRuO ₃ or LaRu
A substrate provided with a conductive perovskite compound film such as O ₃ or La _1-x Sr _x CoO _3, or a film made of various ferrites such as Fe ₃ O ₄ can be used. For the purpose of forming a magneto-resistive element on Si, an insulating film such as SrTiO ₃ epitaxially grown on Si or TiN epitaxially grown on Si is used.
The magnetic body such as a film or a _{Ti 1-x} Al x N film may be epitaxially grown. By using an antiferromagnetic material or a ferromagnetic material for the intermediate layer used here, a GMR element or a TM
In the R element, one of the magnetic films can be fixed.

As a means for optimizing the lattice mismatch between the substrate and the magnetic film, the constituent element A of the general formula (2) may be replaced with alkaline earth having a different ionic radius. For example, Sr
₂ A part of Sr of FeMoO ₆ was converted to Ba having a large ion radius.
, A larger lattice constant can be obtained, and a smaller lattice constant can be obtained by partially substituting Ca with a small ionic radius.

It is also possible to introduce a rare earth as a substituting element. In the rare earth element substitution, the effect of the lattice constant due to the difference in ionic radius and the lattice mismatch is obtained, and the tm and the formal charge of the TM ion can be changed. It is possible to optimize the characteristics of the GMR and TMR elements.

[3] When a magnetoresistive element is formed using the magnetic film according to the present invention as described in [1] and [2] above, the magnetic film according to the present invention and the non-magnetic metal film are used. It is possible to form a so-called GMR element using the in-plane resistance change as a laminated film.

It is also possible to laminate a magnetic film, a non-magnetic insulating film, and a magnetic film to produce a TMR element utilizing a change in interlayer tunnel current between magnetic materials. In such a TMR element, the magnetic film according to the present invention is used for at least one of the magnetic films.

In such a TMR element, the same upper and lower magnetic films of the composite perovskite oxide according to the present invention are used as the upper and lower magnetic films, and the upper and lower magnetic films are preserved by utilizing shape anisotropy and the like. Although it is possible to make the magnetic force different, it is also possible to set the difference in coercive force by using magnetic materials having different compositions in the composite perovskite oxide according to the present invention. Further, the magnetic film according to the present invention is used as one of the upper and lower magnetic films, and Co, Fe,
It is possible to use a metal magnetic film such as Co—Fe or Ni—Fe, or to use a LaMnO ₃ -based, Tl
Of course, it is also possible to use a Mn oxide-based or Fe ₃ O ₄ -based magnetic film. Furthermore, as a method of setting the coercive force of the upper and lower magnetic materials to different values, providing a fixed layer made of a ferromagnetic material and an antiferromagnetic material in close proximity to one magnetic material, or adding appropriate impurities to various magnetic materials By doing so, the coercive force can be adjusted.

In the TMR element, the nonmagnetic insulating film is preferably made of an insulating perovskite compound such as SrTiO ₃ .

[4] The magnetic film used in the magnetoresistive element of the present invention contains the composite perovskite oxide having magnetism represented by the general formula (2), and the composite perovskite oxide having the magnetism May be dispersed in an insulator.

A particularly preferred composition of the particles composed of the magnetic composite perovskite oxide is Sr ₂ FeMo.
O ₆ , Sr ₂ FeReO ₆ , Sr _2-x Ba _x FeMo
O ₆ , Sr _2-x Ba _x FeReO ₆ (0 ≦ x ≦ 2) and the like, whereby a granular TMR element having a high transition temperature and a large magnetoresistance ratio is obtained.

Generally, in the composite perovskite oxide of the general formula (2), two kinds of B site ions of tm and TM are usually ordered, and a crystal in which tm and TM are alternately arranged is formed. In the bulk material, this state, that is, the ordered phase has the original crystal structure, but tm,
It is possible to form a random phase in which TM exists at random, and further form a film having a microstructure composed of a regular phase having a diameter of several tens to several hundreds of atoms separated by a layer composed of several tens to several tens of irregular phases. It can also be created.

The above-mentioned ordered phase is a conductive magnetic phase. In the irregular phase, the tm-TM network essential for electric conduction is cut off, so that the ordered phase exhibits insulating properties. It has become.

In the composite perovskite thin film having a structure in which the ordered phase and the disordered phase are mixed, the conductive magnetic domain phase has a structure in which the conductive magnetic domain phase is separated by a thin insulating nonmagnetic boundary phase. Like a dispersion film in which metal fine particles are dispersed in an insulating film, the electric conduction of this film can be described by a spin-polarized tunnel between conductive magnetic domains.

In this case, it is possible to obtain a larger magnetoresistance by reversing the magnetization direction between the respective domains due to the external magnetic field and a larger magnetoresistance change rate by utilizing a tunnel with a separately provided conductive magnetic electrode film. Furthermore, since the electric resistance of the domain structure film can be arbitrarily set by controlling the domain diameter, the thickness of the boundary phase, and the conductivity,
It is possible to obtain a magnetoresistive element having a resistivity and a resistance change rate suitable for the application.

Such a magnetoresistive film having a domain structure composed of an ordered phase and an irregular phase of the composite perovskite oxide represented by the general formula (2) is formed by forming a magnetic film having the composition represented by the general formula (2). Although it can be easily obtained by appropriately setting the conditions, for example, a slight composition deviation such as tm> Tm or tm <TM is introduced, or Fe used as tm is used.
It can be more easily realized by introducing a small amount of a non-magnetic element such as Mg or Y into a magnetic element such as.

In the above, an element using a magnetoresistive film having a domain structure composed of a regular phase and an irregular phase of the composite perovskite oxide represented by the general formula (2) has been described. A granular structure dispersed in another insulator may be used. At this time, various insulators can be used as the insulator, but SiO ₂ , Al ₂ O ₃ , SrTiO _3, or various types of glass are preferable.

When a magnetoresistive element is formed using such a magnetic film, a phenomenon in which a tunnel current between domains is changed by a magnetic field by changing a coercive force of each domain in the magnetic film is used. Alternatively, a magnetic electrode may be provided on the magnetic film, and a phenomenon in which a tunnel current changes due to a change in the magnetization direction between the electrode and the magnetic domain in the magnetic film may be used. Of course, it is also possible to create a magnetoresistive element having the effects of the above two phenomena.

As the magnetic electrode used here, it is possible to use the same kind of magnetic substance among the above-mentioned composite perovskite oxides, and to use magnetic substances having different compositions among the composite perovskite oxides.

Further, a metal magnetic material such as Co, Fe, Co—Fe, or Ni—Fe may be used as both or one of the magnetic material electrodes.
Of course, it is also possible to use a magnetic material of a ₃ system, a TlMn oxide system, or a Fe ₃ O ₄ system.

[5] As described above, the magnetoresistive element according to the present invention easily provides a magnetic head or the like having a large magnetoresistance change at a high temperature, but this magnetoresistive element is applied to an LSI memory. Of course, it can be used for a storage element or an arithmetic element using a change in magnetoresistance.

Further, the magnetic film according to the present invention can be effectively used for reducing a leak current of a thin film capacitor used for a memory such as a DRAM. In a capacitor used in these devices, a capacitor using an extremely thin dielectric film is required to increase the capacitance. However, in such a capacitor, an increase in leakage due to a tunnel current may be a problem. If the magnetic film according to the present invention is used as the electrode material of such a capacitor and the upper and lower electrodes are given antiparallel magnetization, it is extremely effective in reducing the tunnel current.

Further, it is of course possible to use the dependence of the tunnel current on the magnetization direction for storage and calculation.

[0053]

The present invention will be described in detail with reference to the following examples.
You. (Example 1, Comparative Example 1, Comparative Example 2) Sr₂FeReO₆
Tunneling magnetoresistive element (TMR element)
Child). FIG. 1 shows the TMR element according to the first embodiment.
It is a schematic diagram. SrTiO ₃On the substrate (STO substrate) 1
And Sr₂FeMoO₃The lower magnetic film 2 is laminated,
And SrTiO₃Insulating layer 3, Sr₂FeMoO₃Upper magnet
Are stacked in this order.

First, the Sr ₂ FeReO ₆ lower magnetic film 2 was formed on the STO substrate 1 by using ordinary RF sputtering.
OA was deposited. An SrTiO ₃ insulating layer 3 is placed on this
A, and an upper magnetic film 4 of Sr ₂ FeReO ₆ was deposited at 600 A in the same manner.

It was confirmed by RHEED and XRD that each layer was epitaxially grown on the STO (100) plane of the substrate.

The upper magnetic film 4 is processed into a size of 30 μm × 30 μm by ion milling to obtain 4.2 K.
Changes in tunnel current between the upper and lower magnetic films in a magnetic field (magnetic field is parallel to the film surface) at various temperatures up to 500 K were measured.

FIG. 2 is a characteristic diagram showing the resistance change rate ΔR / Rp of the TMR element according to the first embodiment at room temperature due to a magnetic field. (Where ΔR is the resistance change due to the magnetic field, Rp
Is a resistance in a zero magnetic field). It can be seen that a very large resistance change is obtained even at room temperature. Here, it is considered that the difference in the coercive force at which the upper and lower magnetic films are reversed is due to the shape anisotropy of the film.

On the other hand, as Comparative Example 1, La _0.7 Sr _0. A TMR element similar to that of Example 1 was produced except that ₃ MnO ₃ was used.

As Comparative Example 2, the substrate 1 and the insulating film 3
A TMR element similar to that of Example 1 was produced except that gO and Fe ₃ O ₄ were used for the upper magnetic film 2 and the lower magnetic film 4.

TMR of Example 1, Comparative Examples 1 and 2
The tunnel current change was measured for the device at various temperatures from 4.2K to 400K. FIG. 3 is a characteristic diagram showing the temperature dependence of the resistance change rate in Example 1 and Comparative Examples 1 and 2. In FIG. 3, 5 indicates the characteristics of Example 1, 6 indicates the characteristics of Comparative Example 2, and 7 indicates the characteristics of Comparative Example 2.

In Example 1, a large TMR change was obtained at each temperature up to 400 K, whereas in Comparative Example 1, no TMR change was obtained at a temperature of 150 K or more, and in Comparative Example 2, a tunnel change was observed at 160 K or more. Only a small change in TMR was obtained such that the current was not observable.

It can be seen that the magneto-conductive composite perovskite oxide having a high magnetic transition temperature is used for the magnetic film of the TMR element according to the present invention, so that it shows a high magnetoresistance change over a wide temperature range. Example 2 A TMR element using a Ba ₂ FeReO ₆ film as a magnetic film was manufactured. The configuration of the TMR element was the same as that shown in FIG. Further, it was the same as Example 1 except that the upper magnetic film 4 and the lower magnetic film 2 were made of Ba ₂ FeReO ₆ .

It was confirmed by RHEED and XRD that each layer was epitaxially grown on the STO (100) plane of the substrate.

The upper magnetic film is formed by ion milling.
Processed to a size of 0 micron x 30 micron, 4.2K
Changes in tunnel current between the upper and lower magnetic films in a magnetic field (magnetic field is parallel to the film surface) at various temperatures up to 400 K were measured. As a result, a large TMR change was obtained at each temperature up to 400K. Example 3 A TMR element using a Sr ₂ FeMoO ₆ film as a magnetic film was manufactured. The configuration of the TMR element was the same as that shown in FIG. The Sr ₂ FeMoO ₆ lower magnetic film 2 is formed on the STO substrate 1 by using ordinary RF sputtering.
000 A was deposited. At this time, the in-plane lattice constant of the Sr ₂ FeMoO ₆ lower magnetic film 2 is reduced from the original bulk value of 7.86 A to 7.81 A by epitaxial growth on the STO substrate. It was found by XRD that the lattice constant of was extended from a bulk value of 7.89 A to 8.02 A. The magnetization of this magnetic film was measured using a SQUID susceptibility system, and it was found that the magnetic transition point of this magnetic film was at about 520K. S
It is known that r ₂ FeMoO ₆ has a magnetic transition point of about 450 K in bulk, and this transition temperature rise is considered to be caused by lattice distortion due to epitaxial growth.

Further, an SrTiO ₃ insulating layer 3 was deposited thereon at a thickness of 60 A, and an Sr ₂ FeMoO ₆ upper magnetic film 4 was deposited at a thickness of 600 A. Each layer is the STO of the substrate
The fact that epitaxial growth is on the (100) plane
HEED and XRD confirmed.

The upper magnetic film 4 was processed into a size of 30 μm × 30 μm by ion milling, and a change in tunnel current between the upper and lower magnetic films in a magnetic field (the magnetic field was parallel to the film surface) was measured.

The change in tunnel current between the upper and lower magnetic films in a magnetic field (the magnetic field is parallel to the film surface) was measured at various temperatures from 4.2K to 500K. As a result, a large TMR change was obtained at each temperature up to 500K. (Embodiment 4) In Embodiment 4, an A ₂ tmTMO ₆ -based compound which inherently exhibits semiconductor-like electrical conductivity is used in bulk, and it is shown that a magnetic film into which lattice strain introduced artificially by epitaxial growth exhibits conductivity. confirmed. Further, a TMR element using the magnetic film was manufactured.

First, a Ba ₂ CoReO ₆ film was formed to a thickness of 500 A on an STO substrate by using multiple RF sputtering. At this time, the in-plane lattice constant is 8.01 A, the lattice constant in the direction perpendicular to the substrate surface is 8.12 A, and the bulk crystal has a lattice constant of 8.0.
It was confirmed by XRD that the obtained magnetic film was a highly distorted tetragonal crystal, while the cubic crystal was 78A.

When the electric conductivity and magnetic properties of the magnetic film were examined using a usual four-terminal method and a SQUID magnetometer, the magnetic film showed conductivity and TN = 4
It was found to be 00K ferrimagnetic. While the bulk crystal of this material is a semiconductor with TN = 40K,
It is considered that the above characteristics were obtained due to lattice strain artificially introduced by epitaxial growth.

The Ba ₂ CoRe formed as described above
A TMR element was manufactured and the magnetoresistance effect was measured in the same manner as in Example 1 except that the O ₆ magnetic film was changed to the upper magnetic film and the lower magnetic film, and the Sr ₂ FeReO ₆ of Example 1 was used. The same result as that of the TMR element was obtained. Particles consisting of Sr ₂ FeMoO ₆ with (Example 5) Magnetic was produced between particles TMR element using a structural domain structure film dispersed in an insulator. FIG. 6 shows the configuration of the TMR element. An Sr ₂ FeMoO ₆ magnetic film 12 was deposited on the STO substrate 10 by 300 A using RF sputtering. By adjusting the sputtering conditions at this time, the S
The r ₂ FeMoO ₆ film 12 has a domain structure in which ordered domains 8 of Fe / Mo are separated by an irregular array region 9 in which Fe / Mo is randomly distributed. Confirmed using such techniques.

The magnetic material film was processed into a size of 30 μm × 30 μm by ion milling,
When the applied magnetic field dependence of the electric resistance of the magnetic film was measured at various temperatures up to 00K, it was confirmed that a large magnetoresistance change was obtained in the temperature range from 4.2K to 400K. This is due to the fact that the coercive force of the grains differs between the grains, and that the spin-polarized tunnel current between the grains has changed significantly.

The resistivity of this magnetic film is 10 at room temperature.
Even when a small GMR element having a relatively high millimeter ohmcm is manufactured, an element having a resistance value which is easy to use in terms of a circuit configuration can be manufactured.

FIGS. 4 and 5 are schematic views for explaining the magnetic film of the fifth embodiment. FIG. 4 shows A ₂ having uniform long-range order.
In conceptual diagram showing a crystal structure of TmTMO ₆ complex perovskite, black spots ATMO ₃ region, white dots indicate the ATMO ₃ region. Almost the entire region of the crystal is a region exhibiting a uniform magnetic conductivity of the A ₂ tmTMO ₆ structure. FIG. 5 is a conceptual diagram showing an A ₂ tmTMO ₆ composite perovskite having a domain structure according to Example 5, in which the magnetic conductive region (shaded portion) of the uniform A ₂ tmTMO ₆ structure has non-uniform tm / TM and insulating properties. It can be seen that they are separated by the boundary region indicating. Electric conduction occurs in spin-selective tunnels between the domains, and thus a high magnetoresistance effect is obtained. (Embodiment 6) Embodiment 6 has the same configuration as the TMR element shown in Embodiment 5. Using the magnetic film of Example 5 and a magnetic metal or a conductive magnetic oxide as an electrode material,
It utilizes TMR between domains in the membrane. Sr ₂ FeReO ₆ film having long-range order as an electrode material, and Sr ₂ F having a domain structure similar to that of Example 5 as a magnetic film.
A TMR element was constructed using the eReO ₆ film. Here, the magnetic electrode film and the domain structure film may be laminated in a direction perpendicular to the substrate, or may be a planar type in which a fine magnetic film and an electrode are formed in a plane. When the same TMR measurement was performed as in the example, a TMR device having higher resolution with respect to the magnetic field could be obtained. (Embodiment 7) Embodiment 7 is an example of a magnetoresistive element using a granular film in which a magnetic conductive composite perovskite is dispersed in an insulating matrix. Co as the lower electrode
A film was formed, and a granular film (thickness: 1000 A) in which 50 to 100 A of Sr ₂ FeReO ₆ fine particles were dispersed in a SiO ₂ matrix was formed by sputtering a relatively high sputtering pressure and SiO ₂ on the film. . A homogeneous Sr ₂ FeReO ₆ film was deposited as an upper electrode, and the tunnel current of this film in a magnetic field was measured.
A resistance change rate equivalent to that of Example 1 was obtained. Further, the particles constituting the granular film are Sr ₂ FeMoO ₆ and Sr
_{When two} types of 2FeMoO ₆ were used, a large rate of change could be obtained at a lower magnetic field.

FIG. 6 is a schematic diagram showing a granular film magnetoresistive element according to the seventh embodiment. 8 in the figure is A ₂ tmTMO
₆ are dispersed fine particles made of a magnetic material, 9 is a dispersion medium made of SiO ₂ or the like, and 10 and 11 are electrode films. (Embodiment 8) In Embodiment 8, a TMR element according to the present invention is
This is an example in which fine processing is performed on a substrate. First, Ti _0.9 Al in which oxidation resistance is improved by adding TiN or AlN on the Si single crystal plug from which the natural oxide film has been removed.
_{The 0.1} N film was formed by RF magnetron sputtering to 200
A was deposited. At this time, it was confirmed by RHEED and XRD that the Ti (Al) N film was epitaxially grown in a Si shape by setting the substrate temperature to 650 ° C. Furthermore, Sr ₂ FeMoO ₆ as a lower magnetic film on this
SrTiO ₃ as a barrier layer, Sr as an upper magnetic film
FeMoO ₆ at 400A, 100A, 200A respectively
It was deposited by epitaxial growth and processed using RIE and ion milling. Further, dTEOS as an insulating film and Al wiring as a signal line were formed on the upper portion, thereby producing a magnetic memory cell shown in FIG. FIG. 7 is a conceptual diagram of a TMR device created on Si shown in Example 8. In the figure, 12 is a single crystal Si plug, 13 is Ti (A
1) N barrier layer, 14 is a lower magnetic film, 15 is an STO barrier layer, 16 is an upper magnetic film, 17 is a TEOS insulating film,
Reference numeral 18 denotes a signal readout Al wiring, and 19 denotes a magnetic field application signal wiring. When we measured the magnetic properties of this device,
It was confirmed that the magnetic transition temperature of the upper and lower magnetic films was 490 ° C., which is higher than the bulk value, and the coercive force of the magnetic film was 200 Oe and 500 Oe, respectively. By applying an appropriate current to the signal line of this device, the magnetization direction of the upper magnetic body is reversed to change the TMR current between the upper and lower magnetic bodies, and as a circuit element of a nonvolatile magnetic memory (MRAM) or a spin transistor. It can be used. (Embodiment 9) In Embodiment 9, the TMR element according to the present invention is made of Si.
This is an example in which fine processing is performed on a substrate. First, Ti _0.9 Al _0.1 N was placed on the Si substrate from which the natural oxide film had been removed.
The film was deposited at 200 A by RF magnetron sputtering. At this time, by setting the substrate temperature to 650 ° C., the Ti
It was confirmed by RHEED and XRD that the AlN film was epitaxially grown in a Si shape. On top of this, Sr ₂ FeMoO ₆ as a lower magnetic film and a barrier layer
Sr ₂ FeReO ₆ pseudo-granular film as an intermediate magnetic film, and SrFeMoO ₆ as an upper magnetic film
00A, 500A, and 200A were deposited and processed using RIE and ion milling. Further, dTEOS as an insulating film and Al wiring as a signal line were formed on the upper portion, thereby producing a magnetic memory cell shown in FIG. When the magnetic characteristics of this device were measured, the magnetic transition temperature of the upper and lower magnetic films was 490 ° C., the intermediate magnetic film was 480 ° C. and had a Curie point higher than the bulk value, and the coercive force of the magnetic film was lower and higher. It was confirmed that they were 200 Oersted and 500 Oersted, respectively. The intermediate layer has a structure in which conductive magnetic domains having different coercive forces are separated by non-magnetic / insulating domains as described above, and is larger than a magnetic field caused by a current applied to a signal line. The TMR change rate can be obtained. By applying an appropriate current to the signal line of this device, the magnetization direction of the upper magnetic body is reversed to change the TMR current between the upper and lower magnetic bodies, and as a circuit element of a nonvolatile magnetic memory (MRAM) or a spin transistor. It can be used.

FIG. 8 is a view showing the T formed on Si shown in the ninth embodiment.
It is a conceptual diagram of an MR device. In the figure, 20 is a single crystal Si plug, 21 is a TiAlN barrier layer, 22 is a lower magnetic film, 23 is a pseudo-granular intermediate magnetic film layer, 24 is an upper magnetic film, 25 is a TEOS insulating film, and 26 is a signal readout Al. The wiring 27 is a signal wiring for applying a magnetic field.

[0076]

According to the present invention, the spin polarization ratio is high, showing a large in-plane magnetoresistance change and a magnetoresistance change due to the spin polarization tunnel, and has a high magnetic transition point and an appropriate resistivity. A magnetoresistive element using a magnetic film and having good magnetoresistance characteristics in a practical temperature range centered on room temperature can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a TMR element in Example 1.

FIG. 2 is a characteristic diagram showing a resistance change rate ΔR / Rp of a TMR element in Example 1 due to a magnetic field at room temperature.

FIG. 3 is a characteristic diagram showing the temperature dependence of the rate of change of resistance in Example 1 and Comparative Examples 1 and 2.

FIG. 4 is a conceptual diagram showing a crystal structure of an A ₂ tmTMO ₆ composite perovskite having a uniform long-range order.

FIG. 5 shows A ₂ t having a domain structure in Example 3.
MTMO ₆ conceptual diagram showing the crystal structure of the complex perovskite.

FIG. 6 is a schematic view showing a granular film magnetoresistive element according to a fifth embodiment.

FIG. 7 is a schematic diagram of a TMR element formed on Si shown in Example 8.

FIG. 8 is a schematic view of a TMR element formed on Si shown in Example 9.

[Explanation of symbols]

1 ... substrate 2 ... lower magnetic film 3 ... insulating layer 4 ... upper magnetic film 5 ... Example 1 6 ... Comparative Example 2 7 ... Comparative Example 2 ₈ ... A 2 tmTMO ₆ made of a magnetic material dispersed fine particles 9 ... SiO ₂ Dispersion medium composed of, for example, 10, 11, an electrode film 12, a single-crystal Si plug 13, a Ti (Al) N barrier layer 14, a lower magnetic film 15, an STO barrier layer 16, an upper magnetic film 17, a TEOS insulating film 18, and the like. Signal readout Al wiring 19 ... Signal wiring for applying a magnetic field 20 ... Single-crystal Si plug 21 ... TiAlN barrier layer 22 ... Lower magnetic film 23 ... Pseudo-granular intermediate magnetic film layer 24 ... Upper magnetic film 25 ... TEOS insulating film 26 ... Signal readout Al wiring 27 ... Signal wiring for applying magnetic field

Continued on the front page (72) Inventor Hiromi Yuasa 72 Horikawa-cho, Saiwai-ku, Kawasaki-shi, Kanagawa F-term in Toshiba Kawasaki Office (reference) 5E049 AB03 AB09 AB10 AC00 BA12 BA16

Claims (7)

[Claims] 1. A magnetoresistive element having at least a magnetic film, wherein the magnetic film substantially has the general formula (1) A
_{2 + x} tm ′ _{1 + y} TM ′ _{1 + z} O _6−δ (A is Ca,
At least one selected from Sr and Ba, tm 'is M
at least one selected from n, Ni, Co, Cr and Mg, TM 'is Re, -0.2 <x <0.2, -0.2 <y <0.2, -0.2 <z <
A magnetoresistive element comprising a composite perovskite oxide represented by (0.2, δ is the amount of oxygen deficiency). 2. A magnetoresistive element having at least a magnetic film, wherein the magnetic film has a general formula (2) A _{2 + x} tm
_{1 + y} ™ _{1 + z} O _6-δ (A is at least one selected from Ca, Sr, and Ba, and tm is Fe, Mn, Ni,
At least one selected from Co, Cr, Mg, TM is at least one selected from Mo, Re, -0.2 <x <0.
2. A magnetoresistive element comprising a composite perovskite oxide represented by -0.2 <y <0.2, -0.2 <x <0.2, and δ being the amount of oxygen deficiency) and having lattice distortion. 3. The magnetoresistive element according to claim 2, wherein the lattice strain of the magnetic film is obtained by epitaxially growing a composite perovskite oxide on substrates having different lattice constants. 4. The magnetoresistive element according to claim 2, wherein the in-plane lattice constant of the magnetic film is 99.5% or less or 100.5% or less of the lattice constant of a bulk having the same composition. % Or more. 5. The magnetoresistive element according to claim 1, wherein an insulating film is provided between at least two magnetic films, and the device operates by a spin-polarized tunnel effect between the magnetic films. Magnetoresistive element. 6. A magnetoresistive element having at least a magnetic film, wherein the magnetic film substantially has the general formula (2) A _{2 + x}
tm _{1 +} yTM _{1 + z} O _6-δ (A is Ca, Sr, Ba
Tm is at least one selected from Fe, Mn, N
at least one selected from i, Co, Cr, and Mg;
M is at least one selected from Mo and Re, -0.2 <x <
0.2, -0.2 <y <0.2, -0.2 <x <0.2, where δ is the amount of oxygen deficiency), characterized in that particles composed of a composite perovskite oxide having magnetic properties are dispersed in an insulator. Magnetic resistance element. 7. The magnetoresistive element according to claim 6, wherein
A magnetoresistive element characterized by operating by spin-polarized tunnel effect between particles.