JPH11274597A - Magnetic reluctance element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an element having magnetic reluctance effect wherein large magnetic reluctance ratio which can be used for a memory element even at room temperature and low magnetic field. SOLUTION: La1-x Srx MnO3 (x>0.17) of large Sr composition which becomes ferromagnetic substance and La1-x Srx MnO3 (x<0.17) of small Sr composition which becomes paramagnetic insulator are used for a tunnel insulation film 3. Since La1-x Srx MnO3 of the same constituent element is used for an insulation film 5, spin scattering of an interface can be restrained and furthermore, a film thickness can be controlled by film formation. Therefore, it is excellent in uniformity of element characteristics unlike the one composed of Fe/Al2 O3 . If an insulation film is constructed to be held by ferromagnetic metal and alloy such as La1-x Srx MnO3 and Fe, CO, Ni, it is easy to use as a memory.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a magnetoresistive element using a Mn oxide.

[0002]

2. Description of the Related Art An element utilizing a magnetoresistance effect in which electric resistance changes depending on the presence or absence of a magnetic field is used as a reproducing magnetic head of a hard disk or a magnetic sensor. Attempts have also been made to use it as a memory element for reading out the spin direction of a ferromagnetic material using the magnetoresistance effect.

As a reproducing magnetic head or a magnetic sensor,
A magnetic artificial lattice (spin valve) film using a multilayer film of a ferromagnetic metal and a paramagnetic metal, which has a relatively large magnetoresistance effect at room temperature, has been used. However, as a memory element, the magnetic artificial lattice film has not yet reached a practical level because the magnetoresistance effect is still small and the spin direction of the ferromagnetic material cannot be read sufficiently.

Therefore, as a device for obtaining a large magnetoresistance effect, a magnetoresistance device having a thin paramagnetic insulating film sandwiched between a ferromagnetic metal such as Fe / Al2O3 / Fe has been reported (J. M.
agn.Magn. Matter., vOl.139, L321 (1995)). This magnetoresistive element has a large magnetoresistance effect (tunnel magnetoresistance effect) of 10% or more at room temperature. In this magnetoresistive element, when electrons tunnel through an insulating film, the density of states on the Fermi surface of the ferromagnetic material differs depending on the spin, so that the tunnel conductance is higher when the spins of the two ferromagnetic films are antiparallel than when the spins are parallel. Since it is small, a high rate of change in resistance occurs.

The rate of change in resistance (magnetoresistive ratio: MR) is obtained by calculating the spin polarizabilities of two ferromagnetic layers sandwiching an insulating film by P1 and P2, respectively.
If P2, it is given as in equation (1). MR = 2 P1P2 / (1-P1P2) .... (1) As can be seen from the equation (1), the magnetoresistance element sandwiching a thin paramagnetic insulating film with a ferromagnetic metal has a spin polarizability P1 and P2. If a large ferromagnetic metal is used, a large magnetoresistance ratio can be obtained.

For example, in the case of Fe / Al2O3 / Fe which is conventionally known, a resistance change of about 18% can be obtained at room temperature. However, with such a change, if an attempt is made to read out as an electric signal by the Si integrated circuit, the signal becomes almost the same as the circuit noise and cannot be used as a stable memory element.

On the other hand, a magnetoresistive element using a perovskite type Mn oxide represented by La1-x Srx MnO3 as a ferromagnetic material having a large spin polarization at room temperature is known. This magnetoresistive element has a high Curie point and is a ferromagnetic La1-xSrx MnO3 (x> 0.17) up to room temperature.
Is used as a ferromagnetic material, and SrTiO3 (thickness
6nm) La1-x Srx MnO3 (x> 0.17) / S
rTiO3 / La1-x Srx MnO3 (x> 0.17) multilayer structure.

However, this magnetoresistive element has a temperature of 4.
At 2K, a maximum magnetoresistance ratio of 380% can be obtained, but at a temperature of 250K
Above, the magnetoresistance ratio becomes almost zero. This reason is considered to be due to the interface structure between the SrTiO3 insulating film and the La1-x Srx MnO3 ferromagnetic film. (Literature: App
lied Physics Letters, v Olume69, p3266, 1996)

[0009]

As described above, a magnetoresistive element having a sufficiently large magnetoresistance ratio at room temperature, which can be used for reading data from a memory element, has not been obtained. An object of the present invention is to provide a magnetoresistance element having a high magnetoresistance ratio at room temperature.

[0010]

Means for Solving the Problems The present invention to achieve the above object, consists of a single crystal or polycrystalline, the first consisting of La _1-x Sr _x MnO ₃ conductive film exhibiting ferromagnetism at the temperature of use and electrodes are formed on the first electrode, and La _1-y Sr _y MnO ₃ insulating film exhibiting paramagnetic at the temperature of use, the L
and a second electrode consisting of a _1-y Sr _y MnO ₃ layer insulating film which is formed in ferromagnetic material, when there is a potential difference between said first electrode and the second electrode, electrons La _1-y
The sr _y MnO ₃ insulating film to provide a magnetic resistance element, characterized in that the tunnel.

Further, according to the present invention, the second electrode is made of a single crystal or a polycrystal, and exhibits a ferromagnetic property at a use temperature.
Providing a magnetoresistive element characterized by comprising a _1-z Sr _z MnO ₃ conductive film.

The present invention also provides a magnetoresistive element, wherein the second electrode is made of iron, cobalt, chromium, manganese, nickel or an alloy containing these.

[0013] The present invention, the La _1-y Sr _y MnO
₍₃₎ To provide a magnetoresistive element characterized in that the insulating film is crystalline or amorphous. Further, the present invention provides a magnetoresistive element characterized in that the first electrode temporarily undergoes a phase transition to paramagnetic metal by flowing a current through the first electrode.

[0014] The present invention also provides a magnetoresistive element characterized in that the first electrode temporarily undergoes a phase transition to a paramagnetic metal by irradiating the first electrode with light and heating.
Further, the present invention provides a first electrode made of a La _1-x Sr _x MnO ₃ conductive film which is composed of a single crystal layer or a polycrystalline layer and exhibits ferromagnetism at a use temperature, and formed on the first electrode, and La _1-y Sr _y MnO ₃ insulating film exhibiting paramagnetic at the temperature of use,
The third electrode showing the La and _1-y Sr _y MnO ₃ second electrode showing the formed ferromagnetic on the insulating film, the formed ferromagnetic to the La _1-y Sr _y MnO ₃ insulating film The second electrode and the third electrode are electrically connected in series via the first electrode, and there is a potential difference between the second electrode and the third electrode. , The electron is the La
The _1-y Sr _y MnO ₃ insulating film to provide a magnetic resistance element, characterized in that the tunnel.

Further, according to the present invention, the second electrode and the third electrode
Electrodes, made of single crystal or polycrystalline, provides a magnetoresistive element characterized by comprising La _1-z Sr _z MnO ₃ conductive film exhibiting ferromagnetism at use temperatures.

Further, according to the present invention, the second electrode and the third electrode
Wherein the electrode is made of iron, cobalt, nickel, or an alloy thereof. The La _1-y Sr _y MnO ₃ insulating film to provide a magnetoresistive element which is a crystal or amorphous.

Further, the present invention provides a magnetoresistive element characterized in that the first electrode temporarily undergoes a phase transition to a paramagnetic metal by passing a current through the first electrode. The present invention also provides a magnetoresistive element characterized in that the first electrode temporarily transitions to a paramagnetic metal by irradiating the first electrode with light and heating.

[0018] The present invention comprises a single crystal or polycrystalline, a first electrode consisting of La _1-x Sr _x MnO ₃ conductive film exhibiting ferromagnetism at the temperature of use, it is formed on the first electrode The general formula ABO ₃ (A is P
r, Nd, Gd, Y or Sr, B are Sc, Rh, Sb, Zr, Sn, C
d or Re), comprising an insulating film having a lattice mismatch with LaMnO ₃ of 2% or less, and a second electrode made of a ferromagnetic material formed on the insulating film. And an electron tunnels through the insulating film when there is a potential difference between the first electrode and the second electrode.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. Figure 1 shows La1-x Srx
FIG. 3 is an electronic phase diagram of a MnO3 system. The horizontal axis shows the composition ratio (x) of La and Sr, and the vertical axis shows the temperature (K). In the figure, TN is the antiferromagnetic phase transition temperature, TC is the ferromagnetic phase transition temperature, T
S indicates the structural phase transition temperature. PI is always an insulator phase,
PM indicates a permanent conductor phase, AFI indicates an antiferromagnetic insulator phase, FI indicates a ferromagnetic insulator phase, and FM indicates a ferromagnetic conductor phase.

According to the present invention, La1-x Srx M which becomes a ferromagnetic conductor (the region of FM in FIG. 1) at a use temperature (particularly around normal temperature).
On the nO3 film, a La1-x Srx MnO3 film which becomes a paramagnetic insulator (the area of PI in FIG. 1) at the operating temperature (especially near normal temperature) is laminated, and the La1-x Srx MnO3 film is further laminated on the paramagnetic insulator. La1-x Srx MnO3 with ferromagnetic material laminated
It is a tunnel junction type magnetoresistive element having a ferromagnetic conductor film / La1-x Srx MnO3 paramagnetic insulator film / ferromagnetic structure.

In the present invention, since the magnetoresistance effect element uses the La1-x Srx MnO3 ferromagnetic conductive film which is 100% spin-polarized at the operating temperature, a high magnetoresistance ratio can be obtained as can be seen from the equation (1). it can. Further, in the present invention, L
a1-x Srx MnO3 ferromagnetic conductive film / La1-x Srx
Since the interface of the MnO3 paramagnetic insulating film is a homojunction having the same constituent elements, the state of the interface is good. Therefore, the conventional La1-x Srx MnO in which the state of the tunnel junction interface is not good.
3 Ferromagnetic conductive film / SrTiO3 insulator / La1-x Srx
Compared with a tunnel junction type magnetoresistive element made of a MnO3 ferromagnetic conductive film, the present invention can suppress the spin scattering caused by the interface structure, and can obtain a high magnetoresistance ratio even at around room temperature.

At the operating temperature, especially around room temperature (297K),
The La1-x Srx MnO3 film becomes a ferromagnetic material when the composition of Sr is (x> 0.17), and becomes a paramagnetic insulator when (x <0.17). Therefore, the present invention only needs to have a structure of La1-x Srx MnO3 (x> 0.17) ferromagnetic conductive film / La1-x Srx MnO3 (x <0.17) paramagnetic insulating film / ferromagnetic material. However, in order to obtain a temperature margin, the difference between the Sr compositions of the respective films is preferably 0.04 or more.

In the present invention, La1-x Srx MnO
3 After forming a ferromagnetic conductive film on the substrate,
The film thickness can be controlled by directly forming the rx MnO3 permanent insulating film. Therefore, as compared with a system having different constituent elements such as an Fe / Al2O3 system, the device characteristics are more uniform.

The present invention also relates to a ferromagnetic material such as Fe, Ni, C
Using La and their alloys, La1-xSrxMnO3 ferromagnetic conductive film / La1-xSrxMnO3 paramagnetic insulating film / F
e, Ni, CO or an alloy ferromagnetic material containing these can be used. In this structure, the upper layer is a metal that is easily etched, so that it can be easily processed. The present invention also relates to a ferromagnetic conductive material using Fe, Ni, CO, or an alloy thereof, and using a La1-xSrxMnO3 ferromagnetic conductive film / La1-x
Srx MnO3 paramagnetic insulating film / La1-x Srx MnO
3 The structure can be a ferromagnetic conductive film. In this structure, since both ferromagnetic materials are formed of La1-x Srx MnO3 films, a greater magnetoresistance effect can be realized. In this structure, the composition of Sr in each ferromagnetic conductive film may be the same or different. Next, a case where the magnetoresistive element of the present invention is used for a memory will be described. (Embodiment 1) In this embodiment, a La1-x Srx MnO3 ferromagnetic conductive film / La1-x Srx MnO3 paramagnetic insulating film / F
This is an example in which a magnetoresistive element having a structure of a ferromagnetic metal such as e, Co, or Ni is used as a memory. Standard type (single metal electrode) FIG. 2 is a cross-sectional view of the magnetoresistive element according to the first embodiment of the present invention.

This magnetoresistive element is composed of La1-x Srx M formed on a SrTiO3 substrate 1 having a (001) plane.
nO3 (x = 0.3) ferromagnetic conductive film 2, this ferromagnetic conductive film 2
La1-x Srx MnO3 (x = 0.1) paramagnetic insulating film 3 formed thereon, ferromagnetic metal film 4 of Co formed for each bit on this paramagnetic insulating film 3, this ferromagnetic metal film 4, a SiO2 insulating film 5 formed on the insulating film 5, and a magnetic field generating wiring 6 made of TiAu formed on the insulating film 5. The La1-x Srx MnO3 (x = 0.1) paramagnetic insulating film 3 acts as a tunnel insulating film, and the ferromagnetic conductive films 2, 4
When a voltage is applied in between, a current flows.
At this time, when the spin directions in the ferromagnetic conductive film are aligned, the current easily flows, and when they are not aligned, the current hardly flows. This magnetoresistive element has a large magnetoresistive effect, and can provide a large current ratio when spins are aligned and when spins are not aligned.

Next, a method of manufacturing the magnetoresistive element will be described. First, an SrTiO3 substrate 1 having a (001) plane is set in an ultrahigh vacuum apparatus. Next, oxygen or ozone is introduced into an ultrahigh vacuum apparatus by a molecular beam epitaxy (MBE) method, and the crucible containing La, Sr, and Mn is heated to sublimate each component and irradiate the substrate as a molecular beam. , La1-x Srx MnO3 (x = 0.3) single crystal film 2
Was grown to a thickness of 700 nm. La1-x Srx MnO
3 (x = 0.3) The composition of the single crystal film 2 is La, Sr, Mn
The temperature of the crucible containing each of the raw materials was adjusted to control the amount of the molecular beam flux of each raw material. Substrate temperature is 65
0 ° C. As can be seen from FIG. 1, La1-x Srx
The MnO3 (x = 0.3) single crystal film 2 is a ferromagnetic conductor at the operating temperature of this device (normal earth environment: 223K to 323K).

Next, La, S are continuously applied without breaking the vacuum.
The La1-x Srx MnO3 (x = 0.1) layer 3 having a thickness of 0.6 nm was formed by changing the temperature of the crucible containing r and Mn. As can be seen from FIG. 1, La1-x Srx Mn
The O3 (x = 0. 1) single crystal film 2 is a paramagnetic insulator at the operating temperature of this device (normal earth environment 223K to 323K). Further, a La1-x Srx MnO3 (x = 0.1
) Layer 3 can be used as a tunnel insulating film.

Next, the substrate 1 on which the ferromagnetic conductive film 2 and the paramagnetic insulating film 3 were formed was taken out of the ultrahigh vacuum apparatus, and Co was deposited to a thickness of 50 nm on the paramagnetic insulating film 3 by sputtering. Thereafter, a 100 nm SiO2 insulating film was deposited at a substrate temperature of 300 DEG C. by a plasma CVD method.

Next, 0.5 μm on the surface by photolithography
After providing a resist mask (corresponding to one bit) of a micron square, the SiO2 insulating film was selectively removed with ammonium fluoride to form a SiO2 insulating film 5.

Next, after removing the resist with an organic solvent, a part of the Co film was removed by ion milling at low acceleration using the SiO 2 insulating film 5 as a mask to form a ferromagnetic film 4.
Next, using disilane and oxygen as raw materials again by the thermal CVD method,
A 200 nm thick SiO2 insulating film (not shown) was deposited on the surface of the substrate as a wiring insulating film.

Next, the substrate was transferred into an electron beam evaporation apparatus, and a Ti film was deposited to a thickness of 100 nm and an Au film was deposited to a thickness of 500 nm.
Next, a Ti / Au wiring 6 having a width of 0.5 μm for applying a magnetic field to the CO ferromagnetic electrode 4 was formed by photolithography. At this time, the Ti film was used to improve the adhesion between the Au film and the underlying SiO2 insulating film 5.

Finally, La1-x Srx MnO3 (x = 0.3)
Electrodes for contact were formed on the ferromagnetic conductive film 2 and the Co ferromagnetic metal 4 to form a magnetoresistive element. In this magnetoresistive element, the CO ferromagnetic metal 4 and La1-x Srx MnO3 were used.
(X = 0.3) Appropriate DC voltage is applied between the ferromagnetic conductive films 2 so that the tunnel current flows most.

In this magnetoresistive effect element, the coercive force of the Co ferromagnetic metal is about 0.5 Om square and 50 nm thick, so that it is about 100 Oe, and La1-x Srx MnO3 (x = 0.3
3.) The holding power of the ferromagnetic conductive film 2 was several Oe. Therefore, when the applied magnetic field is 50 Oe, the spin of the La1-x Srx MnO3 ferromagnetic conductive film 2 is inverted without the spin of the Co ferromagnetic metal 4 moving. The resistance changes from the case where the spins are parallel to the case where the spins are anti-parallel. When the tunnel magnetoresistance effect of this magnetoresistance effect element was examined, the applied magnetic field was 50 Oe (1 Oe = 103 / 4pA / m).
As a result, a magnetoresistance ratio of about 90% was obtained at room temperature.

The magnetoresistive element of this embodiment has a La1-x
The Srx MnO3 ferromagnetic conductor is generally used because it has a smaller coercive force than ferromagnetic metals such as Co and can easily reverse spins with a small magnetic field. As the ferromagnetic metal, a ferromagnetic metal made of Fe, Ni, an alloy thereof, or a ferromagnetic metal containing Cr or Mn may be used in addition to CO.

Next, a method of operating the magnetoresistive element thus produced as a memory, that is, a method of writing and reading information will be described. The method of writing information is such a current that the spin direction of the ferromagnetic film 4 having the larger coercive force is rewritten rightward or leftward in the magnetic field generating wiring 6, that is, the coercive force of the CO ferromagnetic metal 4 (several 100 Oe). The current may be sufficient to induce a magnetic field exceeding the above-mentioned value) through the TiAu magnetic field generating wiring 6 to reverse the spin. For example, a rightward direction may be defined as 0, and a leftward direction may be defined as 1.

Next, a method of reading information will be described with reference to FIG. The horizontal axis in FIG. 3 represents a time change, and the vertical axis in FIG. 3A represents the amount of change in the current flowing through the magnetic field generating wiring 6.
The vertical axes of (b), (c), (d) and (e) indicate the ferromagnetic film 4 /
La1-x Srx MnO3 paramagnetic tunnel insulating film 3 / L
a1-x Srx MnO3 represents a tunnel current value flowing between the ferromagnetic conductive films 2. 3 (b), (c), (d),
The upper arrow in (e) indicates the spin direction of the ferromagnetic film 4, and the lower arrow indicates the spin direction of the La1-x Srx MnO3 ferromagnetic conductive film 2.

First, as shown in FIG. 3A, the spin of the ferromagnetic film 4 is not reversed in the magnetic field generating wiring 6,
La1-x Srx MnO3 (x = 0.3) A current I1 is applied to the extent that the spin direction of the ferromagnetic conductive film 2 is reversed. At this time L
a1-x Srx MnO3 (x = 0.3) The change in the tunnel current I2 is measured while changing the spin direction of the ferromagnetic conductive film 2.

As shown in FIG. 3B, in the initial state, the spin direction of the ferromagnetic metal film 4 is rightward, and La1-x Srx
When the spin direction of the MnO3 ferromagnetic conductive film 2 is to the left, when the current I1 is changed as shown in FIG. 3A, the current I2 changes from small to small to large.

As shown in FIG. 3C, in the initial state, the spin direction of the ferromagnetic metal film 4 is rightward, and La1-xS
When the spin direction of the rx MnO3 ferromagnetic conductive film 2 is rightward, when the current I1 is changed as shown in FIG.
The current I2 changes from large to small to large.

As shown in FIG. 3D, in the initial state, the spin direction of the ferromagnetic metal film 4 is leftward, and La1-xS
When the spin direction of the rx MnO3 ferromagnetic conductive film 2 is to the left, when the current I1 is changed as shown in FIG.
The current I2 changes from large to large to small.

As shown in FIG. 3E, in the initial state, the spin direction of the ferromagnetic metal film 4 is leftward, and La1-xS
When the spin direction of the rx MnO3 ferromagnetic conductive film 2 is rightward, when the current I1 is changed as shown in FIG.
The current I2 changes from small to large to small.

The direction of the spin of the Co ferromagnetic metal 4 to which the information is written can be determined by the increase or decrease of I2 when the direction of the current of the magnetic field inducing wire 6 changes. If it corresponds, the memory can be read.

Next, another reading method different from the above-mentioned reading method will be described with reference to FIG. The horizontal axis in FIG. 4 represents a time change, the vertical axis in FIG. 4 (a) represents the amount of change in the current flowing through the magnetic field generating wiring 6, and the vertical axes in FIGS. 4 (b), (c), and (d) represent strong values. The tunnel current value flowing between the magnetic film 4 / La1-xSrxMnO3 paramagnetic tunnel insulating film 3 / La1-xSrxMnO3 ferromagnetic conductive film 2 is shown. 3 (b), (c),
The upper arrow in (d) indicates the spin direction of the ferromagnetic film 4 and the lower arrow indicates the spin direction of the La1-x Srx MnO3 ferromagnetic conductive film 2.

In this read method, not only the Co ferromagnetic metal 4 but also the La1-x Srx MnO3 ferromagnetic conductive film 2 is subjected to spin writing, and the CO ferromagnetic metal 4, La1-
x Srx MnO3 This is a method of reading out both spins of the ferromagnetic conductive film 2.

First, as shown in FIG. 4A, the spin of the ferromagnetic film 4 is not inverted in the magnetic field generating wiring 6,
La1-x Srx MnO3 (x = 0.3) A current I1 is applied to the extent that the spin direction of the ferromagnetic conductive film 2 is reversed. At this time L
a1-x Srx MnO3 (x = 0.3) The change in the tunnel current I2 is measured while changing the spin direction of the ferromagnetic conductive film 2.

As shown in FIG. 4B, in the initial state, the spin direction of the ferromagnetic metal film 4 is leftward, and La1-x Srx M
When the spin direction of the nO3 ferromagnetic conductive film 2 is right,
When the current I1 is changed as indicated by the solid line in FIG. 4A, the current I2 changes from small to large to small. First, change from small to large (ferromagnetic metal 4 left spin, La1-x Srx
The combination of MnO3 (x = 0.3) ferromagnetic conductive film 2 right spin) can be seen. At this time, since the current is finally changed as shown by the solid line in FIG. 4A, the combination of spins in the initial state is preserved.

Next, as shown in the upper part of FIG. 4C, the initial state is such that the spin direction of the ferromagnetic metal film 4 is left,
When the spin direction of the 1-x Srx MnO3 ferromagnetic conductive film 2 is to the left, when the current I1 is changed as shown by the solid line in FIG. Change. By changing from large to large first, the combination of (ferromagnetic metal 4 left spin, La1-x Srx MnO3 (x = 0.3) ferromagnetic conductive film 2 left spin) can be understood. At this time, since the current is finally changed as shown by the dotted line in FIG. 4A, the combination of spins in the initial state is preserved.

Next, as shown in the lower part of FIG. 4C, the initial state is such that the spin direction of the ferromagnetic metal film 4 is right,
When the spin direction of the 1-x Srx MnO3 ferromagnetic conductive film 2 is to the left, when the current I1 is changed as shown by the solid line in FIG. Change. By changing from small to small first, the combination of (ferromagnetic metal 4 right spin, La1-x Srx MnO3 (x = 0.3) ferromagnetic conductive film 2 left spin) can be understood. At this time, since the current is finally changed as shown by the dotted line in FIG. 4A, the combination of spins in the initial state is preserved.

Next, as shown in FIG. 4D, in the initial state, the spin direction of the ferromagnetic metal film 4 is rightward, and the La1-xS
When the spin direction of the rx MnO3 ferromagnetic conductive film 2 is rightward, when the current I1 is changed as indicated by the solid line in FIG. 4A, the current I2 changes from large to small to large. First, change from large to small (ferromagnetic metal 4 right spin, La1-x
Srx MnO3 (x = 0.3) ferromagnetic conductive film 2 right spin)
You can see the combination of At this time, since the current is finally changed as shown by the solid line in FIG. 4A, the combination of spins in the initial state is preserved.

Thus, using this reading method,
Since it is possible to read out four different states,
Bit information can be stored in one cell. Judgment of spin direction from change in current value I2 and accompanying magnetic field induced current I1
Can be controlled by providing a CMOS circuit or TTL circuit externally. In the present invention, a large number of the above-described magnetoresistive elements shown in FIG.
By controlling I1 and judging changes in I2 by combining TTL circuits, etc., a high-density integrated circuit can be realized. According to the present invention, the amount of change in I2 that is sufficiently larger than the noise level of the silicon integrated circuit can be obtained, so that reading for each bit can be performed accurately.

In the present invention, La1-x Srx MnO3
Instead of the paramagnetic insulating film 3, La1-x Srx Oy formed without sublimation of Mn paramagnetic insulating film or La + Sr: M
A permanent insulating film in which the composition ratio of n: O deviates from 1: 1: 3, or a film obtained by further doping other metal ions with impurities can also be used as the tunnel insulating film. This is also valid in all of the following embodiments.

As described above, in this structure, La1-x S
Since the coercive force of the rx MnO3 ferromagnetic conductive film is small, the coercive force of the La1-x Srx MnO3 ferromagnetic conductive film is different from that of the ferromagnetic metal such as Fe, CO and Ni. By using the ferromagnetic layer having the larger magnetic force as the storage layer, the magnetoresistance is slightly reduced, but the element can be easily used as a nonvolatile memory.

In this embodiment, the CO ferromagnetic film 4
Instead, as shown in FIG. 5, it becomes a ferromagnetic metal at room temperature and becomes La1-x Srx MnO3 (x> 0.17 where x = 0.17).
0.3) layer and the lower layer La1-x Srx MnO3 (x =
0.3) A film having a different Sr composition from the ferromagnetic conductive film 2 and having a difference in coercive force may be used. La1-x Srx M of the second layer
The nO3 ferromagnetic conductive film 7 may be grown following the insulating film by MBE. La1-x Srx MnO3 Both the La1-x Srx MnO3 ferromagnetic conductive films 2 and 7 sandwiching the insulating film 3 have a spin polarizability of almost 100%, so the magnetoresistance effect is further increased and a maximum of about 150% is obtained. Was.

Since this structure exhibits a large magnetoresistance effect even with a small magnetic field, it is suitable not only for memories but also for highly sensitive magnetic heads and magnetic sensors. (Example 2) Standard type polycrystalline La1-xSrxMnO3 + amorphous insulating film (single metal electrode) FIG. 6 is a sectional view of a magnetoresistive element according to Example 2 of the present invention.

This magnetoresistive element is composed of a polycrystalline La1-x Srx MnO3 (x = 0.35) ferromagnetic conductive film 9 formed on a Si substrate 8 and a La1-x Srx MnO3 (x = 0.35) ferromagnetic conductive film 9 formed on the ferromagnetic conductive film 9.
x Srx MnO3 (x = 0.1) paramagnetic insulating film 10, ferromagnetic metal film 11 made of COFe formed for each bit on paramagnetic insulating film 10, and formed on ferromagnetic metal film 11
It is formed of a SiO2 insulating film 5 and a magnetic field generating wiring 6 made of TiAu formed on the insulating film 5. La1-x S
The rx MnO3 (x = 0.1) paramagnetic insulating film 10 functions as a tunnel insulating film, and a current flows when a voltage is applied between the ferromagnetic conductive films 9 and 11. At this time, when the spin directions in the ferromagnetic conductive film are aligned, the current easily flows, and when they are not aligned, the current hardly flows. This magnetoresistive element has a large magnetoresistive effect, and can provide a large current ratio when spins are aligned and when spins are not aligned.

Next, a method of manufacturing this magnetoresistive element will be described. A polycrystalline La1-x Srx MnO3 (x = 0.35) ferromagnetic conductive film 9 was grown to a thickness of 300 nm on a Si substrate 8 at a substrate temperature of 550 DEG C. by MBE.

Next, the substrate temperature is lowered to 100 ° C. or lower, and an amorphous La1-x Srx MnO3 (x = 0.1) paramagnetic insulating film 10 having a thickness of 0.4 nm is formed on the ferromagnetic conductive film 9 by reducing the Sr composition. Was formed. As shown in FIG. 1, this paramagnetic insulating film 10 becomes a paramagnetic insulator at an element operating temperature (227 K to 327 K) and can be used as a tunnel insulating film. Next, the substrate was taken out, and 500 nm of COFe was deposited on the substrate surface by a sputtering method. Then, Example 1
In the same manner as described above, the element is separated into a square of 0.5 μm square and amorphous La1-x Srx MnO3 (x = 0.1)
COFe ferromagnetic metal film 11 on paramagnetic insulating film 10, SiO
Two insulating films 5 were formed.

Next, in the same manner as in the first embodiment,
The Ti / Au magnetic field generating wiring 6 was formed by photolithography and lift-off techniques. Next, the polycrystalline La1-
x Srx MnO3 (x = 0.35) Ferromagnetic conductive film 9, COFe
An electrode for contact is formed on the ferromagnetic metal film 11, and the COFe ferromagnetic metal film 11 and the polycrystalline La1-x Srx MnO3 (x = 0.
35) A DC voltage of an appropriate magnitude was applied between the ferromagnetic conductive films 9 so as to adjust the tunnel current to flow most.

When the tunnel magnetoresistive effect of the magnetoresistive element thus produced was examined, the applied magnetic field was 10 Oe.
^{(However, 1 Oe = 10 3 / 4p} A / m) under the resistance change of about 70% was observed at room temperature. In this case, the spin of the CoFe ferromagnetic metal film 11 does not move and the polycrystalline La1-x Srx MnO
3 When only the spins of the ferromagnetic conductive film 9 are inverted, the resistance changes from a case where the respective spins are parallel to a case where the respective spins are antiparallel.

In this embodiment, the amorphous La1-x Srx
If the following method is used to form the MnO3 (x = 0.1) paramagnetic insulating film 10 in addition to the above method, the film can be formed without changing the substrate temperature.

First, a polycrystalline La1-x Srx MnO3 (x = 0.1) is placed on the polycrystalline La1-x Srx MnO3 ferromagnetic conductive film 9.
At the same time, boron, carbon, or phosphorus is simultaneously supplied as an impurity under the condition that the paramagnetic insulating film can be grown. B2O3, carbon, P2O5, etc. are suitable for the respective raw materials.

Next, this substrate is sublimated by laser ablation or sputtering. Thereby, the polycrystalline La
1-x Srx MnO3 paramagnetic insulating film is composed of microcrystalline La1-xS
The structure changes to a structure in which the amorphous La1-x Srx MnO3 paramagnetic insulating film 13 surrounds the rxMnO3 paramagnetic insulator 12. Since the amorphous structure surrounds the microcrystalline body, it prevents leakage current at the microcrystalline interface,
Even at 0.4 nm to 10 nm, a high-quality tunnel paramagnetic insulating film having no pinhole can be obtained. Even in this structure, the polycrystalline L
a1-x Srx MnO3 ferromagnetic conductive film 9 and amorphous L
The interface structure of the a1-x Srx MnO3 paramagnetic insulating film 10 is improved, and unnecessary scattering of electrons can be prevented.

In this embodiment, La1-x Srx MnO
3 The method of forming the paramagnetic insulating film 10 includes a method of forming an underlying La1-xS
After growing the rx MnO3 ferromagnetic conductive film 9, there is also a method in which the substrate is heated to a high temperature (for example, about 1100 DEG C.) in an oxygen atmosphere to excessively oxidize the vicinity of the surface to make it amorphous.
In this case, the crystal layer is likely to be amorphized for each unit cell in the vertical direction of the substrate due to distortion, so that the thickness can be controlled with high precision as in the case of the film forming method.

The magnetoresistive element of this embodiment can be used as a nonvolatile memory as in the first embodiment. In this case, if a CMOS circuit or TTL circuit is made in the silicon substrate area around the element, it will be a monolithic memory element, and it can be reduced in cost and size compared to separately making a magnetoresistive element and a silicon element and mounting it in a hybrid. Benefits are born.

The magnetoresistive element memory according to the present embodiment also employs a polycrystalline La1-x S
The spin of the rx MnO3 ferromagnetic conductive film 9 and the ferromagnetic film 11 can be read and written.

In this embodiment, instead of the CoFe ferromagnetic film 11, La1-
An xSrx MnO3 (e.g., x> 0.17) layer can be used. At this time, the lower layer La1-x Srx MnO3 (x =
0.35) A film having a different Sr composition from the ferromagnetic conductive film 9 and having a difference in coercive force may be used. In this case, the upper layer La1-x
The Srx MnO3 ferromagnetic conductive film may be grown following the amorphous La1-x Srx MnO3 insulating film 10 by MBE. This element can also be used as a high-sensitivity magnetic head and a magnetic sensor as described above.

Example 3 Tunnel junction between La1-xSrxMnO3 (multiple electrodes) FIG. 8 is a sectional view of a magnetoresistive element according to Example 3 of the present invention. In the magnetoresistance effect element of this embodiment, La1-x
Srx MnO3 ferromagnetic conductive film / La1-x Srx MnO3
This is an example in which the structure of the paramagnetic insulating film / La1-xSrxMnO3 ferromagnetic conductive film is connected in series.

As shown in FIG. 8, the magnetoresistive element of this embodiment is composed of La1-x Srx MnO formed on the substrate 1.
3 Ferromagnetic conductive film 2, two La1-x Srx MnO3 paramagnetic tunnel insulating films formed on the ferromagnetic conductive film 2, La1-x Srx MnO3 formed on the paramagnetic tunnel insulating film 3, respectively. Consisting of a ferromagnetic conductive film 14,
The La1-x Srx MnO3 ferromagnetic conductive films 14 are connected in series via a power supply.

Next, a method of manufacturing this magnetoresistive element will be described. First, La1-xS
rx MnO3 (x = 0.1) polycrystal and La1-x Srx MnO
3 (x = 0.3) Polycrystal is formed.

Next, in the vacuum furnace, the (001) plane
An rTiO3 substrate 1 is set. Next, oxygen is introduced into the vacuum furnace by several TOrr, and an excimer laser is irradiated on the La1-x Srx MnO3 (x = 0.3) polycrystalline target by a laser ablation method, so that the single crystal La1 is placed on the SriTiO3 substrate 1. -x Srx MnO3 (x = 0.3) A ferromagnetic conductive film is formed to a thickness of 1500 nm. Similarly, La1-x Srx
A polycrystalline target of MnO3 (x = 0.1) is irradiated with an excimer laser to obtain a single crystal La1-x Srx MnO3 (x = 0.
3) Single crystal La1-x Srx MnO3 on ferromagnetic conductive film
(X = 0.1) A 1 nm paramagnetic insulating film is formed. Similarly, an excimer laser is irradiated on a La1-x Srx MnO3 (x = 0.3) polycrystalline target to obtain a single-crystal La1-xS
rx MnO3 (x = 0.1) Single crystal La1-
x Srx MnO3 (x = 0.3) ferromagnetic conductive film of 200 nm
Grow sequentially.

Next, single-crystal La1-x Srx MnO3 (x = 0.3) ferromagnetic conductive film / single-crystal La1-x Srx MnO3 (x = 0.1) only in a 2-micron square region by photolithography.
Paramagnetic insulating film / single crystal La1-x Srx MnO3 (x = 0.
3) Etching is performed up to the interface of the substrate 1 so that the ferromagnetic conductive film remains.

Next, S was deposited on this substrate by plasma CVD.
iN is deposited on the 50 nm surface. Subsequently, a resist for electron beam, such as ZEP, is applied on the surface, and the center of a 2-micron square region is linearly exposed to electron beam and developed to form a resist mask of 100 nm size. Using this as a mask, only SiN is first etched with ammonium fluoride. Then S
Using iN as a mask, etching was performed from the surface by low-acceleration ion milling, and La1-x Srx MnO3 (x =
0.3) Etch halfway through the ferromagnetic conductive film 2 and dig a groove with a width of 100 nm as shown in FIG. 8 to obtain La1-x Srx on the surface.
MnO3 (x = 0.3) Ferromagnetic conductive film 14 and single crystal La1-x
The Srx MnO3 (x = 0.1) paramagnetic insulating film 3 is divided into two regions.

Next, contact electrodes are provided in the two regions and the lower La1-x Srx MnO3 (x = 0.3) layer in the same manner as in the first embodiment. Appropriate bias voltages were applied to the contact electrodes so that a tunnel current flowed, thereby producing a magnetic effect element.

This tunnel current fluctuates with respect to the magnetic field due to the magnetoresistance effect. La1-xSrx MnO3 (x
= 0.3) is 100% spin-polarized, and the magnetoresistance effect is large. The rate of change of the double tunnel current at zero magnetic field and several Oe is about 170% at room temperature. It can be used as a memory, a high-sensitivity magnetic head, and a magnetic sensor as in the above embodiments.

In this embodiment, the left and right La1-x Srx MnO
3 Although the size of the ferromagnetic conductive film 14 is the same, the coercive force can be made different between the left and right by changing the size between the left and right. The coercive force of the ferromagnetic material is expressed by the width of the electrode as W and the thickness as t.
Then, if W is sufficiently large (about 10 times or more) compared to t, it is proportional to t / W. Therefore, the coercive force can be freely adjusted by changing the width and thickness of the left and right ferromagnetic materials. When the coercive force of the left and right ferromagnetic materials is changed, there are a plurality of rates of change of the magnetoresistance effect, which can be used for a multivalued memory. As a method for providing a difference in the holding power between the left and right ferromagnetic materials, La1-
There is a method of changing the Sr composition of xSrxMnO3.

(Example 4) Tunnel between La1-xSrxMnO3 and ferromagnetic metal (multiple electrodes) FIG. 9 is a sectional view of a semiconductor device according to Example 4 of the present invention. In the magnetoresistive element of this embodiment, La1-x Srx
This is an example in which the structures of a MnO3 ferromagnetic metal film / La1-x Srx MnO3 paramagnetic insulating film / a ferromagnetic metal film such as Fe, Co, and Ni are connected in series.

As shown in FIG. 9, the magnetoresistive element according to the present embodiment is composed of La1-x Srx MnO formed on the substrate 1.
3 Ferromagnetic conductive film 15, two La1-x Srx MnO3 paramagnetic tunnel insulating films 16 formed on the ferromagnetic conductive film 15, Fe, Co, Made of a ferromagnetic metal film 17 such as Ni,
The ferromagnetic metal films 17 are respectively connected in series via a power supply.

Next, a method for producing this magnetoresistive element will be described. First, a target was prepared in the same manner as in Example 3, and a single crystal La was formed by laser ablation.
1-x Srx MnO3 (x = 0.5)
A single crystal La1-x Srx MnO3 (x = 0.05) paramagnetic insulating film 16 having a thickness of 00 nm is sequentially formed on the substrate 1 with a thickness of 1 nm. In this case, La1-x Srx MnO3 was obtained in the same manner as in Example 2.
(X = 0.5) Ferromagnetic conductive film 15 is polycrystalline, La1-x Sr
The xMnO3 (x = 0.05) paramagnetic insulating film 16 may be made amorphous.

Next, the single crystal La1-x Srx MnO3 (x = 0.
05) Form a CoFe ferromagnetic metal film on the paramagnetic insulating film 16. Next, a single-crystal La1-x Srx MnO3 (x = 0.5) ferromagnetic conductive film / single-crystal La1-x Srx MnO3 (x = 0.05) paramagnetic insulating film / CoFe ferromagnetic metal in a 2-micron square region by photolithography Etching is performed up to the interface of the substrate 1 so that the film remains.

Next, S was formed on the substrate by plasma CVD.
iN is deposited on the 50 nm surface. Subsequently, an electron beam resist such as ZEP is applied to the surface, and the center of a 2 micron square region is linearly exposed to an electron beam and developed to form a 0.1 micron resist mask. Using this as a mask, first, only the SiN insulating film is etched with ammonium fluoride to form a SiN insulating film 5. Next, using the SiN insulating film 5 as a mask, the surface is etched by low-acceleration ion milling to separate the ferromagnetic metal film 17 on the substrate into two regions by etching as shown in FIG. At this time, the ferromagnetic metal film 17 is formed of the underlying La1-x Srx MnO.
3 (x = 0.05) Since a sufficiently high etching ratio can be obtained with the paramagnetic tunnel insulating film 16, only the ferromagnetic metal film 17 can be selectively etched.

Next, a magnetic field generating wiring 6 is formed on the SiN insulating film 5 by photolithography. The current direction and the current value of the magnetic field generating electrode are made the same. A contact electrode is provided on each of the three ferromagnetic electrodes, and an appropriate bias voltage is applied to each of the contact electrodes so that a tunnel current flows. Thus, the magnetoresistive element of this example was formed. This magnetoresistive element also has La1-x Srx MnO3 (x = 0.
5) Since the ferromagnetic conductive film 15 is 100% spin-polarized, a large tunnel magnetoresistance effect is observed.

The magnetoresistive element of this embodiment is also shown in FIGS.
When a magnetic field that causes only the La1-x Srx MnO3 layer to undergo spin reversal is applied at the same timing as in the first embodiment, the spin direction of CoFe can be read from the change in the tunnel current according to the same principle as in the first embodiment. Can be used.

In the magnetoresistive element of this embodiment, the coercive force can be adjusted by changing the electrode sizes of the left and right ferromagnetic metal films 17. If the width of the electrode is W and the thickness is t, if W is sufficiently larger than t (about 10 times or more), the coercive force is proportional to t / W. The coercive force can be adjusted. The coercive force can be differentiated by changing the width on the left and right.

(Embodiment 5) LaMnO3 substrate Sr diffusion type FIG. 10 is a sectional view of a magnetoresistive element according to Embodiment 5 of the present invention. The magnetoresistive effect element of the present embodiment is: La
Sr is diffused into the 1-x Srx MnO3 paramagnetic insulating film to form a La1-x Srx MnO3 ferromagnetic conductive region, and the La1-x Srx MnO3 ferromagnetic conductive film / La is formed in the direction of the substrate surface.
1-x Srx MnO3 ferromagnetic conductive film / La1-x Srx M
This is an nO3 ferromagnetic conductive film structure.

That is, the magnetoresistive element of this embodiment is
The LaMnO3 paramagnetic insulating film formed on the substrate 1 and the two La1-x Srx MnO3 ferromagnetic conductive regions 19 formed by diffusing in the LaMnO3 paramagnetic insulating film 18; The -x Srx MnO3 ferromagnetic conductive region 19 is configured to tunnel-join through a LaMnO3 paramagnetic tunnel insulating film.

Next, a method for manufacturing this magnetoresistive element will be described. First, the LaMnO3 paramagnetic insulating film 1 was formed by MBE, laser ablation, or sputtering.
8 is grown on the substrate 1 to a thickness of about 500 nm. Next, LaMn
The O3 paramagnetic insulating film 18 is etched into a 2 micron square device region.

Next, the LaMnO 3 paramagnetic insulating film 18
On top of this, 200 nm of SiO2 is deposited by CVD. Next, by using photolithography or electron beam lithography, a window having a size of 1 mm × 0.8 mm is formed at two locations by opening 0.05 μm in an element area of 2 μm square using resist.

Next, the SiO 2 in the window portion of the resist was
Is vertically processed by reactive ion etching to obtain LaMnO.
After exposing the three layers, the substrate is horizontally anisotropically etched with ammonium fluoride to reduce the width of SiO2 to 10
Narrow down to nm.

Next, after removing the resist with an organic solvent, 20 nm thick Sr21 is deposited on the surface by sputtering. When this is heated at 900 ° C. in an oxygen atmosphere, Sr diffuses from the surface to form a La1-x Srx MnO3 ferromagnetic conductive region 19. Although the composition x is spatially distributed, almost all of the diffusion regions have a composition region where x> 0.175 is a ferromagnetic conductor. At this time, the diffusion layer advances under the SiO2 layer, and the L
This means that two La1-x Srx MnO3 ferromagnetic wire regions having a width of about 0.9 micron were formed with the aMnO3 paramagnetic insulator therebetween.

Next, a contact electrode was formed on the La1-x Srx MnO3 ferromagnetic conductive region 19 in the same manner as in the previous embodiment, to produce a magnetoresistive element. This element is La
Since 1-xSrx MnO3 is 100% spin-polarized, the tunnel magnetoresistive effect is large, and nearly 100% at room temperature was obtained. This element can be used as a high-sensitivity magnetic sensor. Further, by providing a ferromagnetic electrode such as CO instead of the contact electrode, it can be used as a writable memory according to the same principle as in the above embodiment.

The magnetoresistive element of this embodiment is of a planar type, which is advantageous when integrated and used. (Embodiment 6) FIG. 11 is a sectional view of a magnetoresistive element according to Embodiment 6 of the present invention. The magnetoresistive element of this embodiment has a structure of a La1-x Srx MnO3 ferromagnetic conductive region / La1-x Srx MnO3 paramagnetic tunnel insulating region / La1-x SrxMnO3 (x = 0.5) ferromagnetic conductive region in the substrate surface direction. Was prepared by an atomic force microscope.

A method for fabricating the magnetoresistive element of this embodiment will be described. First, a La1-x Srx MnO3 ferromagnetic conductive film is grown on the substrate 1 by several tens of nm. Next, a current is passed and locally oxidized (increased oxygen composition) using a probe coated with a metal of the atomic force microscope probe 24 in the air to obtain La1-x Srx MnO3 + y paramagnetic of about 10 nm. An insulating film 22 can be formed. This is in principle the same as the method used for processing nanometer-sized Ti electrodes and the like (Reference: Japanese Journal of Appl.
ied Physics, vOl.32, L553, (1993)). The paramagnetic insulating region may be formed by applying an electron beam to the La1-x Srx MnO3 ferromagnetic conductive film to desorb oxygen to make the film paramagnetic insulative.

In this embodiment, by applying a current to the La1-x Srx MnO3 layer or raising the temperature by irradiating light, the La1-x Srx MnO3 is temporarily transformed into a paramagnetic metal to apply a magnetic field. In this method, the spin is fixed in the direction of the magnetic field during cooling.

Finally, an electrode was formed in the La1-x Srx MnO3 (x = 0.5) ferromagnetic conductive region 23 to complete the magnetoresistive element of this embodiment. The magnetoresistive element of this example could also obtain a high magnetoresistance ratio.

(Embodiment 7) Writing and erasing by heat FIG. 12 is a sectional view of a magnetoresistive element according to Embodiment 7 of the present invention. The basic configuration of the ferromagnetic thin film is the same as that of the first embodiment. The difference is that a separate contact electrode is also provided for the La1-x Srx MnO3 ferromagnetic conductive film 2 and connected to a DC or AC power supply. On the other hand, La1-x Srx M
For the ferromagnetic metal electrode 4 on the nO3 paramagnetic insulating film 3, a material having a large coercive force such as CO is used, and the spin is fixed.

The spin of the La1-x Srx MnO3 ferromagnetic conductive film 2 is inverted with a magnetic field smaller than the coercive force of the ferromagnetic metal electrode 4. The feature of the magnetoresistive effect element of this embodiment is that the direction of spins can be collectively changed by passing a current through the La1-x Srx MnO3 ferromagnetic conductive film 2 and raising the temperature to erase information. It is in. In this method, the La1-x Srx MnO3 ferromagnetic conductor is heated to a temperature higher than the temperature at which phase transition to the paramagnetic metal shown in FIG. The phase transition temperature is S
The r composition is about 70 ° C. for 0.25 and about 100 ° C. for 0.3 or more. The thickness of the La1-x Srx MnO3 ferromagnetic conductive film 2 is set to 100 nm or less so that heating can be performed with a small current. Further, in order to increase the cooling rate after erasing, the surface area around the element is increased so as to increase the thermal conductivity.

Further, laser irradiation is performed, and La at the irradiated portion is irradiated.
It is also possible to erase the spin information by increasing the temperature of the 1-x Srx MnO3 ferromagnetic conductive film 2. (Example 8) Another perovskite having an insulating film (single electrode) FIG. 13 is a sectional view of a magnetoresistive element according to Example 8 of the present invention. In the present embodiment, a paramagnetic insulating film having the structure of the first embodiment is formed by a general formula ABO3 which exhibits paramagnetism at a use temperature.
(A is Pr, Nd, Gd, Y or Sr, B is Sc, Rh, Sb, Z
This is an example in which the insulating film is represented by (r, Sn, Cd or Re) and has a lattice mismatch with LaMnO3 of 2% or less. Since these films also have the same perovskite crystal structure as La1-x Srx MnO3, a uniform and high quality heterojunction can be formed.

The magnetoresistive element of this embodiment is made of SrTi
La1-xSrx MnO3 (x =
0.4) Ferromagnetic conductive film 2, Sr (Rh0.5Sb0.5) O3 paramagnetic tunnel insulating film 25 formed on paramagnetic conductive film 2,
A CoFe ferromagnetic metal film 26 formed on the paramagnetic insulating film 25, a SiN insulating film 27 formed on the ferromagnetic metal film 26, and a Ti / Au magnetic field generated on the insulating film 27 It consists of wiring 28.

Next, a method for manufacturing the magnetoresistive element of this embodiment will be described. First, a single crystal film of a La1-x Srx MnO3 (x = 0.4) ferromagnetic conductive film 2 was grown to a thickness of 300 nm on an SrTiO3 substrate 1 by MBE. The substrate temperature was 850 ° C.

Next, an Sr (Rh0.5Sb0.5) O3 layer paramagnetic tunnel insulating film 25 was formed to a thickness of 2 nm. This film is made of La1-x S
Since the lattice mismatch with rx MnO3 is small, a high-quality insulating film with few defects can be obtained even with a thin film having a thickness of 2 nm.

Next, the substrate was taken out of the vacuum furnace, a 500 nm CoFe ferromagnetic metal film 26 was deposited on the surface of the substrate by sputtering, and a SiN insulating film 27 was formed thereon. afterwards,
The element was separated into a square of 0.5 micron.

Next, the CoFe ferromagnetic electrode 26 and La1-xS
A 0.5 μm wide TiAu magnetic field generating wiring for applying a magnetic field to the rx MnO3 (x = 0.4) ferromagnetic conductive film 2 was formed by photolithography and lift-off techniques.

Next, La1-x Srx MnO3 (x = 0.4)
An electrode for contact is formed on the ferromagnetic conductive film 2, and an appropriate DC voltage is applied between the electrode 28 for generating a CoFe magnetic field and the La1-x Srx MnO3 (x = 0.4) ferromagnetic conductive film 2. ,
Adjust so that the tunnel current flows the most.

Thus, the magnetoresistive element of this example was manufactured. Examination of the tunnel magnetoresistance effect of this magnetoresistance effect element revealed that the applied magnetic field was 10 Oe (however, 1 Oe
Under ^{e = 10 3 / 4p A /} m), the resistance change of about 60% was observed at room temperature. These elements of this embodiment can also be used as a nonvolatile memory as in the first embodiment. Example 1
The ferromagnetic layer La1-x Srx MnO is operated according to the same operation principle as
3 The ferromagnetic conductive film 2 can be used as a memory for reading and writing spins.

In this embodiment, instead of the CoFe ferromagnetic film, La1-x Srx becomes a ferromagnetic metal at room temperature.
MnO3 (x> 0.17) layer and lower La1-x Srx
A film having a different Sr composition from MnO3 (x = 0.4) and having a difference in coercive force may be used. In this case, the second-layer ferromagnetic material La1-x Srx MnO3 may be grown following the amorphous insulating film by MBE. This element can also be used as a high-sensitivity magnetic head and a magnetic sensor as described above.

Also, as in the previous embodiment, La1-x Sr
The x MnO3 layer may be polycrystalline. In this case, although the magnetoresistive effect is slightly reduced, a large substrate is used regardless of the type of the underlying substrate, so that the structure is suitable for mass production. The magnetoresistance effect element of the present invention described above is
La1-x Srx MnO3 ferromagnetic conductive film and La1-x Srx
MnO3 has an interface structure of a paramagnetic tunnel insulating film. L
a1-x Srx MnO3 is 0.1 to 0.2 nm in the [001] axis direction.
It is a cubic crystal called a perovskite structure having a unit cell with a period (the period depends on the Sr composition). In the perovskite structure, a unit cell is a structure in which oxygen is coordinated at the vertex of an octahedron centered on the position of a Mn atom and La or Sr surrounds the periphery. When this material is formed into a film, the unit cells tend to be formed one by one. The tunnel resistance of the device is very sensitive to the thickness of the tunnel insulating film. By using this property, it is easy to precisely control the thickness of the very thin tunnel insulating film (paramagnetic insulating film) of 1 nm or less. Can be manufactured.

The La1-xS used in the present invention
Pr, Nd, or Sm instead of La for rx MnO3;
Even if Ce or Ca is added to some extent at the crystal position, a crystal having a similar crystal structure and similar physical properties can be obtained. These elements or other impurities at room temperature (normal earth environment-
A material added to such an extent that ferromagnetism is not impaired at about 50 ° C. to 50 ° C.) can be used as the ferromagnetic metal electrode. In the above embodiment, it is possible to increase the magnetoresistance effect by connecting a plurality of magnetoresistance effect elements in series by wiring.

[0108]

According to the present invention, L having a spin polarizability of 100% is used.
a1-x Srx MnO3 ferromagnetic conductive film and La1-x Srx
By using a stacked structure of MnO3 paramagnetic tunnel insulating films, a larger magnetoresistance effect can be obtained at room temperature and in a low magnetic field than a device using a conventional magnetic metal material, and the device characteristics are excellent in uniformity. Therefore, it can be used as a memory element, a magnetic head, and a magnetic sensor.

[Brief description of the drawings]

FIG. 1 shows La1- for describing an embodiment of the present invention.
Phase diagram of the xSrx MnO3 layer.

FIG. 2 is a sectional view of the magnetoresistive element according to the first embodiment of the present invention.

FIG. 3 is a diagram for explaining a reading method when the magnetoresistance effect element of the present invention is used for a memory.

FIG. 4 is a diagram for explaining a reading method when the magnetoresistance effect element of the present invention is used for a memory.

FIG. 5 is a sectional view of the magnetoresistive element according to the first embodiment of the present invention.

FIG. 6 is a sectional view of a magnetoresistive element according to a second embodiment of the present invention.

FIG. 7 is a diagram in which a microcrystalline La1-x Srx MnO3 paramagnetic insulating film is dispersed in an amorphous La1-x Srx MnO3 paramagnetic insulating film.

FIG. 8 is a sectional view of a magnetoresistive element according to a third embodiment of the invention.

FIG. 9 is a sectional view of a magnetoresistive element according to a fourth embodiment of the present invention.

FIG. 10 is a sectional view of a magnetoresistive element according to a fifth embodiment of the present invention.

FIG. 11 is a sectional view of a magnetoresistive element according to a sixth embodiment of the invention.

FIG. 12 is a sectional view of a magnetoresistive element according to a seventh embodiment of the present invention.

FIG. 13 is a sectional view of a magnetoresistive element according to an eighth embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... La1-x Srx MnO3 ferromagnetic conductive film 3 ... La1-x Srx MnO3 paramagnetic tunnel insulating film 4 ... ferromagnetic metal film 5 ... insulating film 6 ... Magnetic field generation wiring 7 La1-x Srx MnO3 ferromagnetic conductive film 8 Si substrate 9 polycrystalline La1-x Srx MnO3 ferromagnetic conductive film 10 amorphous La1-x Srx MnO3 paramagnetic Tunnel insulating film 11 ... Ferromagnetic film 12 ... Microcrystalline La1-x Srx MnO3 paramagnetic insulator 13 ... Amorphous La1-x Srx MnO3 paramagnetic insulating layer 14 ... La1-x Srx MnO3 ferromagnetic Conductive film 15 ... La1-x Srx MnO3 Ferromagnetic conductive film 16 ... La1-x Srx MnO3 Paramagnetic tunnel insulating film 17 ... Ferromagnetic metal film 18 ... LaMnO3 film 19 ... La1-x Srx MnO3 ferromagnetic conduction Region 20: SiO2 insulating film 21: Sr film 22: La1-x Srx MnO3 + y Paramagnetic insulating region 23: La1-x Srx MnO3 Ferromagnetic conductive region 24: Atomic force microscope Probe 25 ... Sr (Rh0.5Sb0.5) O3 paramagnetic insulating film 26 ... ferromagnetic metal film 27 ... insulating film 28 ... magnetic field generating wiring

────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI H01B 3/00 H01B 3/12 319 3/12 319 322 322 G01R 33/06 R

Claims (13)

[Claims] 1. A first electrode made of a single crystal or a polycrystal and made of a La _1-x Sr _x MnO ₃ conductive film exhibiting ferromagnetism at a use temperature, and a first electrode formed on the first electrode and used at a use temperature. and La _1-y Sr _y MnO ₃ insulating film exhibiting paramagnetic in this L
and a second electrode consisting of a _1-y Sr _y MnO ₃ layer insulating film which is formed in ferromagnetic material, when there is a potential difference between said first electrode and the second electrode, electrons La _1-y
Magnetoresistive element characterized by tunneling the sr _y MnO ₃ insulating film. Wherein said second electrode is made of a single crystal or polycrystalline, La _1-z Sr _z MnO showing ferromagnetism at use temperatures
_2. The magnetoresistive element according to claim 1, comprising _three conductive films. 3. The method according to claim 1, wherein the second electrode is a ferromagnetic metal made of iron, cobalt, chromium, manganese, nickel or an alloy containing these.
The magnetoresistive element as described in the above. Wherein said La _1-y Sr _y MnO ₃ claim 1 having an insulating film, characterized in that it is amorphous, claim 2 or claim 3 magnetoresistive element according. 5. The first electrode according to claim 1, wherein a current is applied to said first electrode.
5. The magnetoresistive element according to claim 1, wherein said electrode temporarily undergoes a phase transition to paramagnetic metal. 6. The method according to claim 1, wherein the first electrode is temporarily transformed into a paramagnetic metal by irradiating the first electrode with light and heating. The magnetoresistive element according to claim 3 or 4. 7. A first electrode made of a La _1-x Sr _x MnO ₃ conductive film which is composed of a single crystal layer or a polycrystal layer and exhibits ferromagnetism at a use temperature, and is formed on the first electrode. and La _1-y Sr _y MnO ₃ insulating film exhibiting paramagnetic at the temperature of use, and a second electrode showing the formed ferromagnetic this La _1-y Sr _y MnO ₃ insulating film, the La _1-y ; and a third electrode showing the formed ferromagnetic on sr _y MnO ₃ insulating film,
The second electrode and the third electrode are electrically connected in series via the first electrode, and when there is a potential difference between the second electrode and the third electrode, electrons are transferred to the La. _1-y S
A magnetoresistive element characterized by tunneling through an r _y MnO ₃ insulating film. 8. The second electrode and the third electrode are made of a single crystal or polycrystal, and exhibit a ferromagnetism at a use temperature.
Magnetoresistive element according to claim 7, characterized in that it consists of _1-z Sr _z MnO ₃ conductive film. 9. The method according to claim 9, wherein the second electrode and the third electrode are iron,
8. The magnetoresistive element according to claim 7, wherein the element is a ferromagnetic metal made of cobalt, chromium, manganese, nickel or an alloy containing these. Wherein said La _1-y Sr _y MnO ₃ claim 7 in which the insulating film is characterized in that the amorphous, claim 8
Alternatively, the magnetoresistive element according to claim 9. 11. The method according to claim 7, wherein the first electrode temporarily changes its phase to a paramagnetic metal by passing an electric current through the first electrode. Item 1
0. A magnetoresistive element according to item 0. 12. The method according to claim 7, wherein the first electrode temporarily undergoes a phase transition to a paramagnetic metal by heating by irradiating the first electrode with light. The magnetoresistance element according to claim 9 or 10. 13. A first electrode comprising a La _1-x Sr _x MnO ₃ conductive film which is made of a single crystal or polycrystal and exhibits ferromagnetism at a use temperature, and a first electrode formed on the first electrode and used at a use temperature The general formula ABO ₃ (A is Pr, Nd, Gd, Y
Alternatively, Sr and B are represented by Sc, Rh, Sb, Zr, Sn, Cd, or Re), and the lattice mismatch with LaMnO ₃ is 2% or less, and the ferromagnetic film formed on the insulation film A magnetoresistive element comprising: a second electrode made of a body; and when there is a potential difference between the first electrode and the second electrode, electrons tunnel through the insulating film.