JP2001345496A - Magnetic element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic element where a magnetoresistance change factor is large, a saturation magnetic field is small, and an element resistance is adjusted to an appropriate value, with less variation for stable characteristics. SOLUTION: There are provided a granular magnetic film 4 where manganese oxide fine particles having a perovskite structure represented by A1-xBxMnO3 (A represents La, Pr, Nd or Sm while B represents Ca, Sr, or Ba, with x>0.17.) are dispersed in dielectrics matrix; and two layers of magnetic layers 2 and 6 with different magnetic characteristics which face each other across the granular magnetic film. As the magnetization directions of the magnetic layers 2 and 6 are made parallel/non-parallel, the electric resistance along the lamination interface of the granular magnetic film 4 provides a different resistance value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a magnetic element having a granular magnetic film in which ferromagnetic fine particles of manganese oxide having a perovskite structure are dispersed in a dielectric matrix. This magnetic element is very useful for applications such as a magnetic head and a magnetic recording device.

[0002]

2. Description of the Related Art The magnetoresistive effect is a phenomenon in which electric resistance changes when a magnetic field is applied to a certain kind of magnetic material, and is used for a magnetic field sensor, a magnetic head, and the like. Thin films such as permalloy have been widely used for magnetoresistive elements. By using this in a reproducing head such as a hard disk, high-density magnetic recording has been achieved. However, since the rate of change in magnetoresistance of the permalloy thin film is as small as about 2 to 3%, there is a problem that sufficient sensitivity cannot be obtained in order to achieve higher density recording.

In recent years, it has been found that a so-called granular magnetic film in which magnetic ultrafine particles are dispersed in a nonmagnetic metal matrix exhibits a giant magnetoresistance effect based on spin-dependent conduction (Pbys. Rev. Lett. 68). , 3745 (1992)), which is expected to improve the characteristics of a magnetoresistive head and the like (Japanese Patent Application Laid-Open No. 7-3070013). Such a granular magnetic film has a high resistance in the absence of a magnetic field because the spins of each magnetic ultrafine particle are oriented in an irregular direction due to the properties of the magnetic ultrafine particles. , The resistance decreases, and as a result, a magnetoresistance effect based on spin-dependent scattering is exhibited. Granular magnetic films are expected to be next-generation magnetoresistive elements because they are relatively easy to fabricate, but in this case, the magnetic ultrafine particles exhibit superparamagnetism, so the saturation magnetic field is essentially very large. Have a problem.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the granular magnetic film, and has a large magnetoresistance change rate, a small saturation magnetic field, and an element resistance adjusted to an appropriate value. It is another object of the present invention to provide a magnetic element which can perform stable operation with a small variation.

[0005]

The magnetic element of the present invention has the general formula A ₁ -xB _x MnO ₃ (where A is La, Pr, Nd or Sm).
And B represents Ca, Sr or Ba. x> 0.1
7) a granular magnetic film in which manganese oxide fine particles having a perovskite structure represented by 7) are dispersed in a dielectric matrix, and two magnetic layers having different magnetization characteristics opposed to each other with the granular magnetic film interposed therebetween. According to the feature that the magnetization directions of the two magnetic layers are parallel / antiparallel, the electrical resistance in the direction along the lamination interface of the granular magnetic films has different resistance values.

When the magnetization directions of two magnetic layers (hereinafter, referred to as ferromagnetic layers) sandwiching the granular magnetic film are the same (hereinafter, referred to as "parallel"), the magnetization is generated by the magnetization of the two ferromagnetic layers. By the magnetic field, the individual fine particles of manganese oxide dispersed in the granular magnetic film are magnetized in the same direction as the two ferromagnetic layers. Therefore, the manganese oxide fine particles have the same spin conduction band, and the conduction electrons are in a rejection capable of tunneling. In this state, when a voltage is applied between the two electrodes formed on the granular magnetic film, The conduction electrons are conducted between the fine particles by a tunnel effect, and a tunnel current flows.

On the other hand, when the magnetizations of the two ferromagnetic layers sandwiching the granular magnetic film are in opposite directions (hereinafter, referred to as "anti-parallel"), the magnetic field is small and individual manganese oxide fine particles cannot be magnetized. Also, for example, ferromagnetic manganese oxide La
_{Since 1-x} Sr _x MnO ₃ (x ≧ 0.25) has a small coercive force, when either one of the ferromagnetic layers reverses the magnetization, the magnetization becomes scattered, and the probability that adjacent fine particles have a conduction band of the same spin is high. Become smaller. For this reason, even if a voltage is applied between the two electrodes formed on the granular magnetic film, the probability that conduction electrons can tunnel between the particles is greatly reduced,
The resistance becomes higher as compared with the case where the magnetization directions of the two ferromagnetic layers are parallel.

That is, a giant magnetoresistance change can be obtained by reversing the magnetization of one of the two ferromagnetic layers sandwiching the granular magnetic film by an external magnetic field. Also, for example, ferromagnetic manganese oxide La _1-x Sr _x M
nO ₃ (x ≧ 0.25) has a spin polarization in the conduction band of almost 100%, which is larger than the metal ferromagnetic fine particles, so that the magnetization directions of the ferromagnetic layers sandwiching the granular magnetic film correspond to the parallel / antiparallel state. The change in magnetoresistance of the granular film increases.

[0009]

FIG. 1 is a schematic configuration diagram of a magnetic element (spin valve device) illustrating an embodiment of the present invention. From the bottom of the figure, the antiferromagnetic layer 1, the first ferromagnetic layer 2,
A non-magnetic insulating layer 3 and a granular magnetic film 4 are sequentially laminated, and a pair of electrodes 7 for flowing a current parallel to the film surface of the granular magnetic film 4 are formed on both ends of the upper surface of the granular magnetic film 4. A nonmagnetic insulating layer 5 is provided on a portion of the upper surface of the granular magnetic film 4 between the pair of electrodes 7.
The second ferromagnetic layers 6 are sequentially stacked.

The granular magnetic film 4 has the general formula A _1-x B _x
Manganese oxide fine particles having a perovskite structure represented by MnO ₃ (A represents La, Pr, Nd or Sm, B represents Ca, Sr or Ba; x> 0.17) are contained in a dielectric matrix. Become distributed. As the manganese oxide fine particles, La _1-x Sr _x MnO ₃ (x ≧ 0.
It is preferable to use those having a perovskite structure of 25) (hereinafter, appropriately referred to as “LSMO particles”). L
In addition to SMO particles, Nd _1-x Sr _x MnO ₃ , Pr _1-x C
a _x MnO ₃ , La _1-x Sr _x MnO _{3 and the} like can also be used.

On the other hand, as the dielectric matrix, Si
Oxides such as O ₂ , A ₁₂ O ₃ , ZrO ₂ , SiN, AIN,
It is preferable to use a nitride such as BN.

In the granular magnetic film 4, manganese oxide fine particles dispersed in a dielectric matrix are:
Preferably, the crystal is oriented at least with respect to one axis of the crystal. Here, “oriented” includes a state where each particle is substantially substantially oriented, and includes a case where most of the fine particles are oriented and a part is not oriented.

Thus, most of the manganese oxide fine particles simultaneously change the magnetization state according to the change in the magnetization of one ferromagnetic layer. Further, by applying an external magnetic field in the direction of the easy axis of magnetization of the manganese oxide fine particles, the magnetic field necessary for changing the magnetization state of the manganese oxide fine particles can be reduced.

The average particle size of the manganese oxide fine particles is 5 n
m or less. As a result, the magnetization of the manganese oxide fine particles is generated by a weak external magnetic field,
Higher-order tunneling that occurs when the number of particles is 3 or more can be easily caused.

The thickness of the granular magnetic film 4 is 2 to 10 n.
m is preferable.

First ferromagnetic layer 2 and second ferromagnetic layer 6
Is preferably formed of a ferromagnetic material having soft magnetic properties. In the example of FIG. 1, since the first ferromagnetic layer 2 is in contact with the antiferromagnetic layer 1, the magnetization direction is fixed. The magnetization direction of the second ferromagnetic layer 6 can be changed by an external magnetic field.

First ferromagnetic layer 2 and second ferromagnetic layer 6
Is preferably a ferromagnetic layer composed of a metal compound containing metallic cobalt or metallic iron or a multilayer containing at least these metallic compounds. Also, at least one
It is also preferable that the layer is composed of perovskite-type manganese oxide.

The first ferromagnetic layer 2 and the second ferromagnetic layer 6
Although the layers have different magnetization characteristics, specifically, NiFe,
It is composed of CoFe, Co, and a laminated film thereof. In the configuration of FIG. 1, since the magnetization direction of the first ferromagnetic layer is fixed, the coercive force of the ferromagnetic layer alone may be the same.

The thickness of the first ferromagnetic layer 2 and the second ferromagnetic layer 6 is preferably about 10 to 25 nm.

In the example shown in FIG. 1, nonmagnetic insulating layers 3 and 5 are provided between the granular magnetic film 4 and the upper and lower ferromagnetic layers 2 and 6, respectively. As the nonmagnetic insulating layers 3 and 5, oxides such as SiO ₂ , A1 ₂ O ₃ and ZrO ₂ , Si
It is preferable to use a nitride such as N, AIN, or BN.
By providing the non-magnetic insulating layers 3 and 5, the granular magnetic film 4 is electrically and magnetically separated, the leakage current to the ferromagnetic layers 2 and 6 is suppressed, and the upper and lower ferromagnetic layers 2 and 6 are used. An increase in the coercive force of the granular magnetic film 4 can be suppressed.

In this magnetic element, if the magnetization directions of the upper and lower ferromagnetic layers 2 and 6 are the same, the LSMO particles in the granular magnetic film 4 are magnetized in the same direction as the ferromagnetic layers 2 and 6. The LSMO particles have ferromagnetic properties, and the conduction band is separated into two conduction bands 301 and 302 by exchange interaction as shown in FIG. Here, electrons existing in the conduction band 302 having a low electron energy level are up-spin, and the conduction band 30 having a high electron energy level is present.
The electron present in 1 is down spin. That is, L
Electrons in which the direction of magnetization of the SMO particles and the direction of angular momentum of electrons are parallel are up-spin, and electrons in which the direction of magnetization M of the ferromagnetic material is antiparallel to the direction of angular momentum are down-spin.

When the other adjacent LSMO particle is also magnetized in the same direction, the distribution curve of the electron state density with respect to the energy level becomes exactly the same. Therefore,
As shown in FIG. 2B, it is possible to draw an energy phase diagram separated into two conduction bands, a conduction band 304 for up spin and a conduction band 303 for down spin.

In the granular film, the adjacent LSMO
The particles are close enough. That is, since the insulating layer between the particles is very thin, when an appropriate bias voltage is applied to the pair of electrodes 7 in FIG. 1, electrons can tunnel through the insulating layer from one LSMO particle to the other LSMO particle. However, when electrons tunnel, conservation of spin angular momentum is essential, so the same spin energy level must exist in the conduction band of both LSMO particles.

When the magnetization directions of the adjacent LSMO particles are parallel, as shown in FIGS. 2A and 2B, the Fermi level exists in the conduction band of both up spins.
Upspin electrons at the Fermi level in one LSMO particle can transition to the same energy level in the other LSMO particle, resulting in a lower electrical resistance between the electrodes 7.

On the other hand, when the magnetizations of the upper and lower ferromagnetic layers 2 and 6 are anti-parallel, the respective magnetic fields cancel each other out, so that the magnetization of the LSMO particles in the granular film becomes insufficient, and one of the particles is lost. The magnetization directions vary. LSM
As a representative example of a state where the magnetizations of the O particles are not aligned, a case where two adjacent LSMO particles are magnetized in antiparallel will be described.

FIG. 3 is a schematic diagram of a conduction band when two adjacent LSMO particles are magnetized in antiparallel. FIG.
2A is magnetized in the same direction as in FIG. 2A, and a Fermi level exists in the up-spin conduction band.
However, FIG. 3 (b) is magnetized in the opposite direction,
Unlike FIG. 2A, the Fermi level exists in the conduction band of the upspin. In this state, even if an appropriate bias voltage is applied to the electrode 7, there is no state where the spin angular momentum can be preserved at the transition destination, so that electrons cannot tunnel between the LSMO particles via the insulating layer. Similarly, tunneling cannot be performed when two adjacent LSMO particles are magnetized other than antiparallel, so that the electric resistance between the pair of electrodes 7 becomes extremely large.

Accordingly, of the two magnetic layers 2 and 6 opposed to each other with the granular magnetic film 4 interposed therebetween, the magnetization of the magnetic layer whose magnetization direction can be easily reversed is changed to change the magnetization of the two ferromagnetic layers 2 and 6. By making the magnetization directions of 6 parallel / antiparallel, the resistance of the granular magnetic film 4 can be largely changed, and a magnetic element such as a spin valve device having a large change in magnetoresistance can be realized.

By using the magnetic element of the present invention, for example, this magnetic element is arranged near two wirings through which a half-select current flows, and simultaneously passes through two wirings by a magnetic field generated when the half-select current flows. Recording information as a magnetization direction on one of the two ferromagnetic layers having different magnetization characteristics of the magnetic element;
By making the magnetization directions of the two magnetic layers parallel / anti-parallel, a magnetic memory from which information is read can be configured.

FIG. 4 specifically shows an example in which the magnetic element (spin valve device) of the present invention is used as a magnetic memory (solid memory). Each device (spin valve element 401) is arranged near two wirings through which a half-selection current flows, and a half-selection current (changes the magnetization of only the element at the intersection) is simultaneously applied to the two magnetic field forming wirings 403. Due to the magnetic field generated when flowing, information can be recorded on the spin valve device in one of the two ferromagnetic layers with the information as the magnetization direction. In addition, reading of information can be performed by detecting a change in resistance of the device or a change in time of the resistance with the signal detection line 402.

In such recording / reproducing, the magnetization directions of the two ferromagnetic layers having different magnetization characteristics are made parallel / antiparallel by an external magnetic field or a magnetic field generated by a current flowing in the vicinity. Utilizes that the electrical resistance changes. In the magnetic element of the present invention, a granular magnetic film in which fine particles of a specific manganese oxide are dispersed in a dielectric matrix is disposed between two magnetic layers, and the magnetization directions of the two magnetic layers are parallel or other than parallel. In response to the state described above, the electric resistance in the direction along the lamination interface of the granular magnetic film greatly changes. As a result, a device having a large change in magnetoresistance compared to a conventional spin valve device can be obtained.

[0031]

The present invention will be described in more detail with reference to the following examples.

Example 1 A magnetic element having the structure shown in FIG. 1 was manufactured as follows.

[0033] In the present embodiment, using A1 ₂ O ₃ insulating film as a dielectric matrix, the A1 ₂ O ₃ having an average particle diameter of about 3nm in the insulating film _{La 1-x Sr x MnO 3} (0.25 ≦ x ≤
0.85) to form a granular magnetic film 4 in which manganese oxide fine particles having a perovskite structure are dispersed. In this granular magnetic film 4,
The manganese oxide fine particles were formed such that they were substantially oriented in one crystal axis direction, and the distance between the particles was dispersed at about 1 nm.

The first ferromagnetic layer 2 has a thickness of 10
nm of NiFe, and the thickness of the second ferromagnetic layer 6 is 10 n.
m, MnF having a thickness of 25 nm as the antiferromagnetic layer 1
e, the nonmagnetic insulating layers 3 and 5 are made of Al ₂ having a thickness of 1 nm;
O ₃ was formed.

As a result of measuring the magnetic characteristics of this magnetic element,
In response to the change in the magnetization direction of the second ferromagnetic layer due to the external magnetic field, a large resistance change is obtained, and the change amount is
A good result was obtained, which was larger than the conventional granular spin valve structure using Co fine particles.

[0036]

As described above, according to the present invention,
It is possible to provide a magnetic element which has a large magnetoresistance change rate, a small saturation magnetic field, can adjust the element resistance to an appropriate value, and has stable characteristics with little variation.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a magnetic element (spin valve device) illustrating an embodiment of the present invention.

FIG. 2 is a schematic diagram of an electronic structure of adjacent LSMO particles in a granular magnetic film in a magnetization parallel state.

FIG. 3 is a schematic diagram of an electronic structure of an adjacent LSMO particle in a granular magnetic film when the magnetization thereof is antiparallel.

FIG. 4 is a diagram showing an example of a driving method when the magnetic element (spin valve device) of the present invention is used as a magnetic memory (solid memory).

[Explanation of symbols]

REFERENCE SIGNS LIST 1 antiferromagnetic layer 2 first ferromagnetic layer 4 granular magnetic film 3, 5 nonmagnetic insulating layer 6 second ferromagnetic layer 7 electrode 301 conduction band of down spin of LSMO particle in parallel magnetization 302 LSMO particle in parallel magnetization Conduction band of down-spin of another LSMO particle in parallel magnetization 304 conduction band of down-spin of another LSMO particle in parallel magnetization 305 conduction band of up-spin of another LSMO particle in anti-parallel magnetization 306 Up-spin conduction band of other LSMO particles in parallel magnetization

Continued on the front page (72) Inventor Ryoji Fujiwara 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term in Canon Inc. (reference) 2G017 AA02 AB07 AD55 AD63 AD65 5D034 BA03 BA04 BA05 CA08 5E049 AA09 BA12 CB02 DB02 DB12

Claims (10)

[Claims] A compound represented by the general formula A _1-x B _x MnO ₃ (A is La, P
r represents Nd or Sm, and B represents Ca, Sr or Ba. x> 0.17) a granular magnetic film in which manganese oxide fine particles having a perovskite structure represented by x> 0.17) are dispersed in a dielectric matrix, and two layers having different magnetization characteristics opposed to each other with the granular magnetic film interposed therebetween. A magnetic layer, wherein the two magnetic layers have different electrical resistances in a direction along a lamination interface of the granular magnetic films in accordance with the magnetization direction of the two magnetic layers being parallel / antiparallel. Magnetic element. 2. The manganese oxide fine particles are oriented at least to one axis of perovskite crystal.
The magnetic element as described in the above. 3. The manganese oxide fine particles having an average particle size of 5
The magnetic element according to claim 1, wherein the thickness is not more than nm. 4. The magnetic element according to claim 1, wherein a nonmagnetic insulating layer is provided between the granular magnetic film and a magnetic layer sandwiching the granular magnetic film. 5. The method according to claim 1, wherein the manganese oxide fine particles are La _1-x Sr _x
2. The magnetic element according to claim 1, having a perovskite structure represented by MnO ₃ (0.25 ≦ x ≦ 0.85). 6. The method according to claim 1, wherein the dielectric matrix is SiO ₂ , Al _2.
2. The magnetic element according to claim 1, comprising O ₃ , ZrO ₂ , SiN, AIN or BN. 7. The magnetic element according to claim 1, wherein at least one of the two magnetic layers having different magnetization characteristics is in contact with another magnetic material having different magnetization characteristics or an antiferromagnetic layer. 8. The magnetic material according to claim 1, wherein the two ferromagnetic layers having different magnetization characteristics are ferromagnetic layers composed of a metal compound containing metallic cobalt or metallic iron, or a multilayer containing at least these metallic compounds. element. 9. The magnetic element according to claim 1, wherein at least one of the two ferromagnetic layers having different magnetization characteristics is made of perovskite-type manganese oxide. 10. A magnetic element according to claim 1, wherein the magnetic element is arranged near a crossing of two wires, and a magnetic field generated when a half-selection current flows through the two wires simultaneously. A magnetic memory in which information is recorded as a magnetization direction on one of two ferromagnetic layers having different magnetization characteristics of the magnetic element, and the information is read out by making the magnetization directions of the two magnetic layers parallel / anti-parallel.