JP4581394B2 - Magnetic memory - Google Patents

Description

  The present invention relates to a magnetic memory, and is suitable for application to a nonvolatile memory.

In information devices such as computers, DRAMs with high speed and high density are widely used as random access memories.
However, since DRAM is a volatile memory in which information disappears when the power is turned off, a nonvolatile memory in which information does not disappear is desired.

  As a candidate for a non-volatile memory, a magnetic random access memory (MRAM) that records information by magnetization of a magnetic material has attracted attention and is being developed (for example, see Non-Patent Document 1).

  In the future, in MRAM, it is necessary to increase the density in order to increase the storage capacity or reduce the size of the device, and further reduction of the magnetic storage elements constituting the memory cell is required.

  In the MRAM, a current is supplied to each of two types of address wirings (for example, word lines and bit lines) orthogonal to each other, and information is recorded and held in a magnetic memory element at the intersection of the address wirings by a generated current magnetic field. Information is recorded by reversing the magnetization direction of the magnetic layer (storage layer).

In addition, in the MRAM, as a method of reading recorded information, a method is provided in which a selection transistor is provided in each magnetic memory element and current is passed only to the magnetic memory element of the selected memory cell to read information. There is a system in which a magnetic memory element is electrically connected to different types of address wirings, and information is read by passing a current between these two types of address wirings.
In the latter case, since no selection transistor is provided, the structure is simple and high-density integration is possible.

  However, if a selection transistor is not provided, a current may also flow through the magnetic memory element of a memory cell other than the target memory cell, so that information recorded in a desired memory cell can be read accurately. It becomes difficult.

Therefore, as a method for solving this problem, for example, a diode is provided (for example, see Patent Document 1), or the potential of an address wiring such as a word line or a bit line is controlled (for example, see Patent Document 2). Therefore, attempts have been made to increase the read accuracy by reducing the current flowing through the magnetic memory element other than the target memory cell.
Nikkei Electronics 2001.1.22 (pages 164-171) JP 2002-304880 A JP 2002-8369 A

  However, in these methods, it is necessary to add a diode, a circuit component for controlling the potential, etc., so that the structure is complicated and a magnetic memory in which magnetic storage elements are integrated at a high density can be realized. It becomes difficult.

  In order to solve the above-described problems, the present invention provides a magnetic memory that can be integrated with a high density and that can read out recorded information with high accuracy, while adding fewer circuit components. To do.

  The magnetic memory of the present invention includes a magnetic storage element having a storage layer that holds information according to the magnetization state of a magnetic material, and two types of wirings that intersect each other, and the magnetic storage element is located near the intersection of these two types of wirings. The storage layer is configured by stacking at least two or more magnetic layers so that the magnetization directions of the upper and lower magnetic layers are antiparallel to each other, and for reading via the nonmagnetic layer with respect to the storage layer A magnetic layer is provided, current is passed through two types of wiring, and the direction of magnetization of the storage layer is changed by the generated current magnetic field, whereby information is recorded in the storage layer, and current is supplied to the magnetic storage element. The information recorded in the storage layer is read by reversing the magnetization direction of the magnetic layer for reading by flowing polarized electrons and detecting the resistance change of the magnetic storage element. is there

According to the above-described configuration of the magnetic memory of the present invention, at least two or more magnetic layers are stacked so that the magnetization directions of the upper and lower magnetic layers are antiparallel to each other, so that the storage layer is formed. On the other hand, since the magnetic layer for reading is provided via the nonmagnetic layer, the magnetizations of the upper and lower magnetic layers that are antiparallel to each other cancel each other, and the combined magnetization of the entire storage layer is reduced. Therefore, the magnetic influence on the read magnetic layer is reduced, so that the magnetization direction of the read magnetic layer can be easily changed.
Further, by recording the current in the magnetic memory element by injecting polarized electrons by injecting polarized electrons, the magnetization direction of the magnetic layer for reading is reversed and the change in resistance of the magnetic memory element is detected. By reading information, the direction of magnetization of the magnetic layer for reading can be changed by flowing a current into the magnetic memory element and injecting polarized electrons. The resistance value of the nonmagnetic layer between the read magnetic layer and the storage layer is determined by the magnetization direction of the magnetic layer on the read magnetic layer side of the storage layer and the magnetization direction of the read magnetic layer. Since the resistance varies depending on the relationship, the resistance of the entire magnetic memory element also varies depending on the relationship of the magnetization directions.
Therefore, by detecting the resistance change of the magnetic storage element, the relationship between the magnetization direction of the magnetic layer on the read magnetic layer side of the storage layer and the magnetization direction of the read magnetic layer can be understood, and the memory The direction of magnetization of the magnetic layer, that is, the content of recorded information can be known.
At the time of reading information, in order to detect a change in resistance of the target (read target) magnetic memory element, a current is passed through the wiring corresponding to the target magnetic memory element. At this time, a current may flow also in a magnetic storage element that is not intended (other than a target to be read), but even if a current flows through a wiring corresponding to the magnetic storage element that is not the purpose, the amount of current that flows is small. Therefore, the number of polarized electrons to be injected decreases, and a sufficient amount of polarized electrons to change the magnetization direction of the read magnetic layer is not injected. For this reason, only the resistance change of the target (read target) magnetic memory element is observed as the resistance change of the magnetic memory element, and the non-target (non-read target) magnetic memory element does not contribute.
Therefore, the information recorded in the storage layer of the target magnetic storage element can be accurately read from the resistance change of the magnetic storage element.

According to the above-described present invention, the magnetization direction of the read magnetic layer changes relatively easily. Therefore, the magnetization direction can be easily reversed by injecting polarized electrons .
Then, a magnetic layer for reading is added to the magnetic memory element, and it is only necessary to configure a circuit component for supplying a current necessary for recording and reading information to the wiring, and the number of added circuit components is reduced. be able to.
Therefore, it is possible to realize a magnetic memory integrated with high density.

  Further, according to the present invention, the information recorded in the storage layer of the target (read target) magnetic storage element can be accurately read from the resistance change of the magnetic storage element, and the information recorded in the storage layer Can be read with high accuracy.

Prior to the description of the embodiment of the magnetic memory of the present invention, FIG. 9 shows a perspective view of the simplest (simple matrix configuration) MRAM as a general MRAM configuration.
A plurality of address lines 101 extending in the left-right direction in the figure and address lines 102 extending in the front-rear direction in the figure are provided, and a magnetic memory element including a storage layer at the intersection of these two types of address lines 101, 102 110 is arranged. The address wiring 101 is disposed above the magnetic memory element 110, and the address wiring 102 is disposed below the magnetic memory element 110.

Next, a schematic configuration diagram of one embodiment of the magnetic memory is shown in FIGS. FIG. 1 is a schematic cross-sectional view of a main part of one unit of memory cells constituting a magnetic memory. FIG. 2 is a schematic plan view of one unit memory cell.

This embodiment is applied to a magnetic memory (see, for example, US Patent Application Publication No. 2003/0072174) that records information in a storage layer of a magnetic storage element using switching characteristics.

As shown in FIG. 1, this magnetic memory has a magnetic memory element 10 having three magnetic layers: a first magnetic layer 1, a second magnetic layer 2, and a third magnetic layer 3. .
The first magnetic layer 1 and the second magnetic layer 2 are stacked with the nonmagnetic layer 4 interposed therebetween, and the magnetization M1 of the first magnetic layer 1 and the magnetization M2 of the second magnetic layer 2 are opposite to each other. They are magnetically coupled so that they are parallel.
The storage structure 6 that holds information in the direction of magnetization (magnetization state) is configured by the laminated structure of the first magnetic layer 1, the nonmagnetic layer 4, and the second magnetic layer 2.
The third magnetic layer 3 is disposed with respect to the second magnetic layer 2 via a nonmagnetic layer (insulating layer or nonmagnetic conductive layer) 5.
In FIG. 1, the other portions of the magnetic memory element 10 are not shown.

  Examples of the material of the nonmagnetic layer 5 sandwiched between the second magnetic layer 2 and the third magnetic layer 3 include a metal material such as Cu, an oxide such as aluminum oxide, and a nitride such as aluminum nitride. Other carbides can be used.

  Each of the first magnetic layer 1, the second magnetic layer 2, and the third magnetic layer 3 may be a single layer, different magnetic layers may be laminated, or magnetically coupled via a nonmagnetic layer. A plurality of magnetic layers may be used, and the magnetic coupling may be a ferromagnetic coupling or an antiferromagnetic coupling.

Further, in the magnetic memory, as shown in the schematic plan view of FIG. 2, the first address wiring 11 extending in the left-right direction in the figure is arranged above the magnetic memory element 10 in the same manner as the MRAM shown in FIG. A second address line 12 extending in the front-rear direction in the figure is arranged below the magnetic memory element 10, and the first address line 11 and the second address line 12 are substantially orthogonal to each other.
A magnetic memory element 10 is disposed at the intersection of the first and second address lines 11 and 12.
The second address wiring 12 is disposed below the third magnetic layer 13 shown in FIG.
The planar shape of the magnetic memory element 10 is circular. The easy magnetization axes 13 of the magnetic layers 1, 2, 3 constituting the magnetic memory element 10 are arranged so as to have an inclination angle θ (0 <θ <90 °) with respect to the first address wiring 11. .
Although not shown in the drawing, a large number of first address lines 11 and second address lines 12 are provided in a grid pattern according to the number of memory cells in the column direction and row direction.

In this configuration, since the magnetic interaction occurs in the first magnetic layer 1 and the second magnetic layer 2, the first magnetic layer 1 and the second magnetic layer 2 are applied when a uniform external magnetic field is applied. Cannot be reversed.
Therefore, when information is recorded in the storage layer 6 of the magnetic storage element 10, the first address is used to reverse the directions of the magnetization M1 of the first magnetic layer 1 and the magnetization M2 of the second magnetic layer 2. A current is passed through each of the wiring 11 and the second address wiring 12 to induce a current magnetic field.
The combined magnetic field of the current magnetic field by the first address wiring 11 and the current magnetic field by the second address wiring 12 forms a rotating magnetic field that rotates clockwise or counterclockwise, although not shown.
By changing the direction of the magnetization M1 of the first magnetic layer 1 and the direction of the magnetization M2 of the second magnetic layer 2 by applying a current magnetic field, information (for example, information “1” or information "0") can be recorded.

  More specifically, a time difference is provided between the current of the first address wiring 11 and the current of the second address wiring 12 and the switching characteristics are used (described in US Patent Application Publication No. 2003/0072174 described above). The direction of the magnetization M1 of the first magnetic layer 1 and the direction of the magnetization M2 of the second magnetic layer 2 are changed and finally reversed from the direction before recording.

It is desirable that the inclination angle θ of the easy magnetization axis 13 of the magnetic layers 1, 2, 3 constituting the magnetic memory element 10 with respect to the first address wiring 11 is approximately 45 °.
As a result, the directions of the magnetizations M1 and M2 of the first magnetic layer 1 and the second magnetic layer 2 even if the currents of the first address line 11 and the second address line 12 have only one polarity. Can be recorded, and the amount of current required for reversing the directions of these magnetizations M1 and M2 can be made substantially equal (the amount of current when reversing from one direction to the other). And the amount of current when reversing from the other direction to one direction can be made substantially equal).

In this embodiment , the first magnetic layer 1 and the second magnetic layer 2 are configured to have substantially the same amount of magnetization.
Thereby, the magnetization M1 of the first magnetic layer 1 and the magnetization M2 of the second magnetic layer 2 cancel each other, so that the combined magnetization of the storage layer 6 becomes very small and the magnetic field leaking to the outside is reduced. Therefore, the magnetic influence from the first and second magnetic layers 1 and 2 on the third magnetic layer 3 is reduced. Thereby, the direction of the magnetization M3 of the third magnetic layer 3 can be changed relatively easily.

In this embodiment , the thickness T3 of the third magnetic layer 3 is smaller (thinner) than the thickness T1 of the first magnetic layer 1 and the thickness T2 of the second magnetic layer 2. The film thickness T1 of the first magnetic layer 1 and the film thickness T2 of the second magnetic layer 2 are substantially equal in order to make the magnetization amount substantially equal.
Thus, by making the third magnetic layer 3 thinner than the first magnetic layer 1 and the second magnetic layer 2, the first and second magnetic layers 3 with respect to the third magnetic layer 3 can also be made. The magnetic influence from the layers 1 and 2 can be reduced.
Instead of reducing the thickness of the third magnetic layer 3, the planar pattern shape of the third magnetic layer 3 is made different from the planar pattern shapes of the first magnetic layer 1 and the second magnetic layer 2 ( For example, the effect of reducing the magnetic influence from the first and second magnetic layers 1 and 2 on the third magnetic layer 3 can be obtained in the same manner. Thus, when the magnetic influence from the first and second magnetic layers 1 and 2 on the third magnetic layer 3 is reduced, the magnetization M2 of the third magnetic layer 3 is changed to that of the first magnetic layer 1. It becomes easy to reverse the magnetization M1 and the magnetization M2 of the second magnetic layer 2.

Further, in this embodiment , in particular, the direction of the magnetization M3 of the third magnetic layer 3 is reversed by causing a current to flow through the second address wiring 12 below the magnetic memory element 10 to generate a current magnetic field. Constitute.
Then, the third magnetic layer 3 is used as a read magnetic layer, and information recorded in the first magnetic layer 1 and the second magnetic layer 2 of the storage layer 6 is read using the third magnetic layer 3. .

Hereinafter, an operation of reading information recorded in the storage layer 6 in the magnetic memory of this embodiment will be described.
Here, the direction of the magnetization M3 of the third magnetic layer 3 is changed by changing the direction (polarity) of the current flowing through the second address line 12 below the third magnetic layer 3.

First, FIGS. 3A and 3B show the magnetization state of each layer when the direction of the current flowing through the second address wiring 12 is changed.
3A and 3B, the direction of the magnetization M3 of the third magnetic layer 3 changes, but the magnetization of the storage layer 6 that retains information, that is, the magnetization M1 and the second magnetic layer 1 of the first magnetic layer 1. It is assumed that the magnetization M2 of the layer 2 does not change. The magnetization M1 of the first magnetic layer 1 is directed downward to the right in the drawing, and the magnetization M2 of the second magnetic layer 2 is directed to the upper right in the drawing. When the current flowing through the second address wiring 12 at the time of reading is made sufficiently smaller than the current at the time of recording, the directions of the magnetizations M1 and M2 of the storage layer 6 do not change in this way. On the other hand, when the current flowing at the time of reading is made slightly smaller than the current at the time of recording, the directions of the magnetizations M1 and M2 of the storage layer 6 change due to the current magnetic field from the second address wiring 12, but when the current is stopped, Return to.

In FIG. 3A, the direction of the current I flowing through the second address wiring 12 is directed from the back to the front in the figure, whereby a counterclockwise current magnetic field H is generated and the magnetization M3 of the third magnetic layer 3 is changed. Turn down to the left. Therefore, the direction of the magnetization M3 of the third magnetic layer 3 is antiparallel to the direction of the magnetization M2 of the second magnetic layer.
In FIG. 3B, the direction of the current I flowing through the second address wiring 12 is directed from the front to the back in the figure, whereby a clockwise current magnetic field H is generated, and the magnetization M3 of the third magnetic layer 3 is changed. Turn to the upper right. Therefore, the direction of the magnetization M3 of the third magnetic layer 3 is parallel to the direction of the magnetization M2 of the second magnetic layer.

Then, if an appropriate nonmagnetic material or thickness is selected for the nonmagnetic layer 5 between the second magnetic layer 2 and the third magnetic layer 3, the direction of the magnetization M2 of the second magnetic layer 2 and The relationship with the direction of the magnetization M3 of the third magnetic layer 3 can be detected by a resistance via the nonmagnetic layer 5.
For example, when the second magnetic layer 2 and the third magnetic layer 3 are magnetic layers mainly composed of a transition metal such as Co or Fe, and the nonmagnetic layer 5 is made of aluminum oxide, the second magnetic layer 2 and the third magnetic layer 3 When the direction of the magnetization M2 of the layer 2 and the direction of the magnetization M3 of the third magnetic layer 3 are parallel, the resistance of the nonmagnetic layer 5 is small, and when the direction is antiparallel, the resistance of the nonmagnetic layer 5 is large.
That is, FIG. 3A is a high resistance state, and FIG. 3B is a low resistance state.

  As the resistance of the nonmagnetic layer 5 changes in this way, the resistance of the entire magnetic memory element 10 also changes. That is, the resistance of the magnetic memory element 10 is increased in FIG. 3A, and the resistance of the magnetic memory element 10 is decreased in FIG. 3B.

On the other hand, when the information recorded in the storage layer 6 is opposite to that shown in FIG. 3 (the magnetization M1 of the first magnetic layer 1 is in the upper right direction and the magnetization M2 of the second magnetic layer 2 is in the lower left direction). The resistance of the magnetic memory element 10 is reversed with respect to the direction of the current I flowing through the second address wiring 12.
That is, when the current I is the same as in FIG. 3A (from the back to the front), the resistance is low, and when the current I is the same as FIG. 3B (from the front to the back), the resistance is high.

Therefore, in the present embodiment , information recorded in the storage layer 6 is read using such characteristics in the magnetic layers 1, 2, and 3 of the magnetic storage element 10.
Specifically, the current I flowing through the second address wiring 12 is changed with time as shown in FIG. 4A, for example. That is, after holding for a while with a constant current amount in one polarity, the current amount and polarity are changed, and then holding for a while with a constant amount of current in the other polarity.
Thus, by changing the current I with time, the direction of the magnetization M3 of the third magnetic layer 3 is reversed.
Thereby, the resistance of the magnetic memory element 10 changes with time as shown in FIG. 4B. In FIG. 4B, for the sake of convenience, the case where the resistance decreases is information “0”, and the case where the resistance increases is information “1”.
As shown in FIG. 4B, since the change in resistance of the magnetic memory element 10 differs depending on the content of information recorded in the storage layer 6, it becomes possible to read out the information recorded in the storage layer 6.

  In addition, even if the time change of the current I flowing through the second address wiring 12 is reversed from that shown in FIG. 4A, the information recorded in the storage layer 6 can be read out similarly.

Next, in this embodiment , a read operation when a plurality of magnetic memory elements 10 are arranged to configure a magnetic memory will be described.
Here, as shown in a plan view in FIG. 5, a case where there are nine magnetic storage elements 10 in three vertical and three horizontal directions will be described. Corresponding to the nine magnetic storage elements 10, three first address lines 11 (11A, 11B, 11C) and three second address lines 12 (12P, 12Q, 12R) are arranged in a lattice pattern. Has been placed. For example, the first address wiring 11 is a bit line, and the second address wiring 12 is a word line.
A capacitor 13 and a resistor 14 are connected in series to one end of each second address line 12 to form a differentiation circuit 15.

For example, when reading information recorded in the magnetic memory elements 10 (10BP, 10BQ, 10BR) in the center row, the magnetic memory to be read out of the first address lines (word lines) 11 is used. The address wiring 11B corresponding to the elements 10BP, 10BQ, and 10BR is selected, the current i is supplied while maintaining a constant potential, and the direction (polarity) of the current i is changed halfway.
At this time, since the magnetization M3 of the third magnetic layer 3 is reversed in the magnetic memory elements 10BP, 10BQ, 10BR corresponding to the address wiring 11B, the magnetic memory element 10 is changed according to the information recorded in the respective memory layers 6. Resistance decreases or increases.
As a result, a positive or negative pulse signal 16 is observed by the differentiating circuit 15 connected to the second address wiring 12 according to the recorded information.

Here, in the magnetic memory elements 10 in the other rows where the first address wiring 11 is not selected, no current flows through the first address wiring 11 or current flows through the first address wiring 11. However, since the amount of current is small and a current magnetic field sufficient to reverse the direction of the magnetization M3 of the third magnetic layer 3 is not generated, the direction of the magnetization M3 of the third magnetic layer 3 does not reverse, and the magnetic memory element There is no 10 resistance change.
Therefore, the observed pulse signal 16 is not affected by the magnetic memory elements 10 in the unselected rows, and only the resistance change of the magnetic memory elements 10 in the desired center row contributes. Therefore, the information content of the magnetic memory element 10 of the target memory cell can be read accurately.
In FIG. 5, it can be seen from the pulse signal 16 that the left and right magnetic memory elements 10BP and 10BR have the same information, and the middle magnetic memory element 10BQ has different information.

  Thus, even in a magnetic memory in which a large number of magnetic storage elements 10 are arranged, information recorded in the magnetic storage element 10 of a desired memory cell can be read out accurately.

According to the above-described embodiment , the magnetization M1 of the first magnetic layer 1 and the magnetization M2 of the second magnetic layer 2 are antiparallel to each other, and the first magnetic layer 1 and the second magnetic layer 1 Since the magnetization amount of the magnetic layer 2 is substantially equal, the magnetization M1 of the first magnetic layer 1 and the magnetization M2 of the second magnetic layer 2 cancel each other, and the first and second magnetic layers with respect to the third magnetic layer 3 are cancelled. Since the magnetic influence from 1 and 2 is reduced, the direction of the magnetization M3 of the third magnetic layer 3 can be changed relatively easily.
As a result, the direction of the magnetization M3 of the third magnetic layer 3 can be easily reversed by the current magnetic field H generated by the current I of the second address wiring 12.

  The resistance value of the nonmagnetic layer 5 between the third magnetic layer (reading magnetic layer) 3 and the storage layer 6 is equal to the third magnetic layer (reading magnetic layer) 3 side of the storage layer 6. The direction of the magnetization M2 of the second magnetic layer 2 and the direction of the magnetization M3 of the third magnetic layer 3 vary. For this reason, the resistance of the entire magnetic memory element 10 also changes depending on the relationship between the directions of the magnetizations M2 and M3.

Therefore, by detecting the resistance change of the magnetic memory element 10 by reversing the direction of the magnetization M3 of the third magnetic layer (reading magnetic layer) 3, the direction of the magnetization M2 of the second magnetic layer 2 can be detected. The relationship with the direction of the magnetization M3 of the third magnetic layer 3 is known, and thereby the direction of the magnetizations M1 and M2 of the magnetic layers 1 and 2 of the storage layer 6, that is, the content of information recorded in the storage layer 6 is known.
Further, in the magnetic memory element 10 of the undesired memory cell, a sufficient current magnetic field is not generated to change (invert) the direction of the magnetization M3 of the third magnetic layer 3, so that the resistance change of the magnetic memory element 10 is caused. What is observed is only a change in resistance of the target (read target) magnetic memory element 10, and a non-target (non-read target) magnetic memory element 10 does not contribute.

Therefore, according to this embodiment , even in a magnetic memory having a simple matrix configuration in which a memory cell is not provided with a selection transistor, information recorded in the storage layer 6 of the magnetic storage element 10 of the desired memory cell is accurately read out. It becomes possible.
This makes it possible to realize a magnetic memory integrated with a higher density by adopting a simple matrix configuration.

Next, an embodiment of the magnetic memory of the present invention will be described.
In this embodiment, a current is passed between the storage layer and the read magnetic layer, and unipolar electrons are injected into the read magnetic layer, thereby reversing the magnetization of the read magnetic layer. .
FIG. 6 shows a schematic configuration diagram of an embodiment of a magnetic memory of the present invention. FIG. 6 is a schematic cross-sectional view of the main part of one unit of memory cells constituting the magnetic memory.

In the magnetic memory element 20 of the present embodiment, the first magnetic layer 1, the second magnetic layer 2, the third magnetic layer 3, and the nonmagnetic layers 4 and 5 are the same as the magnetic memory element 10 shown in FIG. It is the same composition as.
Also, a schematic plan view of a memory cell can be the same configuration as the configuration shown in FIG.

In the present embodiment, in particular, a laminated structure of a magnetization fixed layer 21 and an antiferromagnetic layer 22 is provided below the third magnetic layer 3 serving as a read magnetic layer with a nonmagnetic layer 23 interposed therebetween. .
The magnetization M21 of the magnetization fixed layer 21 is fixed to the left in the figure by the antiferromagnetic layer 22.
Thus, by providing the laminated structure of the magnetization fixed layer 21 and the antiferromagnetic layer 22 below the third magnetic layer 3, the magnetization M3 of the third magnetic layer 3 is obtained by the action of the magnetization fixed layer 21. It becomes possible to fix the direction of the.
In the present embodiment, the magnetization fixed layer 21 and the third magnetic layer 3 are laminated via the nonmagnetic layer (for example, a nonmagnetic conductive layer) 23, so that the magnetization fixed layer 21 and the third magnetic layer 3 are stacked. Due to the magnetic interaction, the direction of the magnetization M3 of the third magnetic layer 3 is leftward, that is, the direction of the magnetization M21 of the magnetization fixed layer 21 is opposite (antiparallel).
Then, the direction of the magnetization M3 of the third magnetic layer 3 is fixed in a manner other than during operation, that is, when information recording or information reading is not performed on the memory cell.

  Each of the first magnetic layer 1, the second magnetic layer 2, the third magnetic layer 3, and the magnetization fixed layer 21 may be a single layer, different magnetic layers may be laminated, or a nonmagnetic layer may be formed. A plurality of magnetic layers magnetically coupled to each other may be used, and the magnetic coupling may be a ferromagnetic coupling or an antiferromagnetic coupling.

Hereinafter, an operation of reading information recorded in the storage layer 6 in the magnetic memory of the present embodiment will be described.
In the present embodiment, the third magnetic layer (reading magnetic layer) is injected by injecting polarized electrons into the magnetic memory element 20 by passing a current through the magnetic memory element 20 through an address wiring (not shown). 3 is configured to change the direction of the magnetization M3.

  Since electrons that have passed through a magnetic material undergo spin polarization, when a current is passed through a magnetic material with a large volume through a magnetic material with a small volume, the magnetization of the magnetic material with the smaller volume is parallel to the magnetization with a larger volume. It has the property that force works to become.

In this embodiment, the storage layer 6 is configured as in the previous embodiment, and the third magnetic layer 3 is formed thinner than the first magnetic layer 1 and the second magnetic layer 2. When polarized electrons are injected from the first magnetic layer 1 side toward the third magnetic layer 3 (current flows from the third magnetic layer 3 side toward the first magnetic layer 1), the second A force acts on the magnetization M3 of the third magnetic layer 3 so that the direction is parallel to the magnetization M2 of the magnetic layer 2 of the second magnetic layer 2.
Instead of forming the third magnetic layer 3 thin, the planar pattern of the third magnetic layer 3 can be made smaller than the planar pattern of the first magnetic layer 1 and the second magnetic layer 2. Since the volume of the magnetic layer 3 can be reduced, the same effect can be obtained.

For this reason, when the current amount exceeds a certain amount, as shown in FIG. 7A, the direction of the magnetization M2 of the second magnetic layer 2 and the direction of the magnetization M3 of the third magnetic layer 3 are antiparallel. 7B, the magnetization M3 of the third magnetic layer 3 is reversed so as to be parallel to each other.
On the other hand, as shown in FIG. 7C, when the direction of the magnetization M2 of the second magnetic layer 2 and the direction of the magnetization M3 of the third magnetic layer 3 are parallel, there is no change.

As in the previous embodiment , the resistance of the nonmagnetic layer 5 changes depending on the relationship between the direction of the magnetization M2 of the second magnetic layer 2 and the direction of the magnetization M3 of the third magnetic layer 3. As a result, the resistance of the entire magnetic memory element 20 also changes.
Therefore, if a current is passed through the magnetic storage element 20 and a change in voltage due to a change in the amount of current is detected, the respective states can be separated, so that the information recorded in the storage layer 6 can be read out. Is possible.
Here, a change in voltage due to a change in current is shown in FIG. Curve A is a change in the case shown in FIGS. 7A and 7B, and curve B is a change in the case shown in FIG. 7C. In the curve A, it turns out that it changes to low resistance more than fixed current amount.

Also in the configuration of the present embodiment, when a magnetic memory is configured by arranging a plurality of magnetic storage elements 20, information recorded in the storage layer 6 of the target (read target) magnetic storage element 20. Can be read accurately.
In the present embodiment, the circuit configuration is slightly different from the configuration shown in FIG. 5, but current flows from the two types of intersecting address wirings to the target (read target) magnetic storage element 20, and What is necessary is just to comprise so that the voltage of the both ends of the magnetic memory element 20 can be observed, and the circuit components to add are comparatively few.

The target magnetic memory element 20 (to be read) can be injected with polarized electrons sufficient to reverse the direction of the magnetization M3 of the third magnetic layer (reading magnetic layer) 3 from the address wiring. Since a large amount of current flows, the direction of the magnetization M3 of the third magnetic layer 3 can be reversed, and the resistance of the magnetic memory element 20 changes.
On the other hand, in the magnetic storage element 20 that is not intended (other than the read target), no current flows, or even if a current flows, the amount of current is small, and the magnetization of the third magnetic layer (reading magnetic layer) 3 Since polarized electrons sufficient to reverse the direction of M3 cannot be injected, the direction of the magnetization M3 of the third magnetic layer 3 does not reverse and the resistance of the magnetic memory element 20 does not change.
For this reason, the observed resistance change (voltage change shown in FIG. 8) is not affected by the undesired magnetic memory element 20, and only the desired resistance change of the magnetic memory element 20 contributes. Accordingly, the information content of the magnetic memory element 20 of the target memory cell can be read accurately.

According to the present embodiment described above, similarly to the previous embodiment , the magnetization M1 of the first magnetic layer 1 and the magnetization M2 of the second magnetic layer 2 cancel each other, and the first and Since the magnetic influence from the second magnetic layers 1 and 2 is reduced, the direction of the magnetization M3 of the third magnetic layer 3 can be changed relatively easily.
This makes it possible to easily reverse the direction of the magnetization M3 of the third magnetic layer 3 by injecting polarized electrons accompanying the current flowing through the magnetic memory element 20.

  The resistance value of the nonmagnetic layer 5 between the third magnetic layer (reading magnetic layer) 3 and the storage layer 6 is equal to the third magnetic layer (reading magnetic layer) 3 side of the storage layer 6. The direction of the magnetization M2 of the second magnetic layer 2 and the direction of the magnetization M3 of the third magnetic layer 3 vary. For this reason, the resistance of the entire magnetic memory element 20 also changes depending on the relationship between the directions of the magnetizations M2 and M3.

Accordingly, by detecting the change in resistance of the magnetic memory element 20 by reversing the direction of the magnetization M3 of the third magnetic layer (reading magnetic layer) 3, the direction of the magnetization M2 of the second magnetic layer 2 is detected. The relationship with the direction of the magnetization M3 of the third magnetic layer 3 is known, and thereby the direction of the magnetizations M1 and M2 of the magnetic layers 1 and 2 of the storage layer 6, that is, the content of information recorded in the storage layer 6 is known.
Further, in the magnetic memory element 20 of the undesired memory cell, a current amount of current that generates polarized electrons sufficient to change (invert) the direction of the magnetization M3 of the third magnetic layer 3 does not flow. Therefore, only the resistance change of the target magnetic storage element 20 (to be read) is observed as the resistance change of the magnetic storage element 20, and the other purpose (other than the target to be read) of the magnetic storage element 20 is not observed. Does not contribute.

Therefore, according to the present embodiment, the information recorded in the storage layer 6 of the magnetic storage element 20 of the desired memory cell is accurately stored even in a magnetic memory having a simple matrix configuration in which no selection transistor is provided in the memory cell. Can be read out.
This makes it possible to realize a magnetic memory integrated with a higher density by adopting a simple matrix configuration.

In addition, according to the present embodiment, the laminated structure of the magnetization fixed layer 21 and the antiferromagnetic layer 22 is provided below the third magnetic layer 3, so that it is not in operation (information recording or information reading). The direction of the magnetization M3 of the third magnetic layer 3 is fixed when the memory cell is not), and the magnetization M3 of the third magnetic layer 3 due to the injection of polarized electrons The direction can be reversed only by reversing from a fixed direction, and the direction of the current flowing through the magnetic memory element 20 in order to inject polarized electrons can be made only one.
As a result, the circuit configuration of the magnetic memory can be simplified.

Note that the configuration in which the stacked structure of the magnetization fixed layer 21 and the antiferromagnetic layer 22 is provided below the third magnetic layer 3 can also be applied to the configuration of the magnetic memory element 10 of the previous embodiment. . In that case, a laminated structure of the magnetization fixed layer 21 and the antiferromagnetic layer 22 is provided between the second address wiring 12 and the third magnetic layer 3. This simplifies the circuit configuration of the magnetic memory by generating a current magnetic field from the second address wiring 12 to reverse the direction of the magnetization M3 of the third magnetic layer 3 to only one direction. It becomes possible.

Further, instead of providing the laminated structure of the magnetization fixed layer 21 and the antiferromagnetic layer 22, in the above-described embodiment , the magnetization of the third magnetic layer (reading magnetic layer) 3 is performed by an external magnetic field except during operation. It is also possible to fix the direction of M3. In this way, it is possible to simplify the circuit configuration of the magnetic memory by fixing the direction of the magnetization M3 of the third magnetic layer 3 except during operation by an external magnetic field.

In the above-described embodiment, the two types of wirings 11 and 12 for applying a current magnetic field to the magnetic memory element are orthogonal to each other. However, the present invention includes a case where the two types of wirings cross each other at an angle. .
In the above-described embodiment, the magnetic memory element of each memory cell is arranged at the intersection of two types of wiring. However, in the present invention, the magnetic memory element is arranged near the two types of intersection (near the intersection). This includes cases where

In the above-described embodiment , the storage layer is configured by the two magnetic layers of the first magnetic layer and the second magnetic layer. However, the storage layer may be configured by three or more magnetic layers.
For example, each of the first magnetic layer and the second magnetic layer is composed of a plurality of magnetic layers magnetically coupled in antiparallel by magnetic interaction, that is, for example, the magnetization directions of the upper and lower magnetic layers are antiparallel. It may be configured to have four or six magnetic layers magnetically coupled so as to be.
Further, for example, three or more magnetic layers may be magnetically coupled so that the magnetization directions of the upper and lower magnetic layers are antiparallel, that is, the magnetization directions are staggered.

  The present invention is not limited to the above-described embodiments, and various other configurations can be taken without departing from the gist of the present invention.

It is a schematic sectional drawing of the principal part of the memory cell of 1 unit of a magnetic memory . It is a schematic plan view of the memory cell of 1 unit of a magnetic memory . FIGS. 3A and 3B are diagrams showing magnetization states of respective layers when the direction of current is changed in the magnetic memory of FIGS. 1 and 2. FIGS. A and B are diagrams for explaining an operation of reading information in the magnetic memory of FIGS. 1 and 2. FIG. 3 is a plan view when a plurality of magnetic memory elements are arranged in the magnetic memory of FIGS. 1 and 2. It is a schematic sectional drawing of the principal part of the memory cell of 1 unit of the magnetic memory of embodiment of this invention . FIGS. 7A to 7C are diagrams illustrating an operation of reading information in the magnetic memory of FIG. FIG. 7 is a diagram showing a change in voltage when the current passed through the magnetic memory element is changed in the magnetic memory of FIG. 6. It is a perspective view of MRAM of a simple matrix structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 1st magnetic layer, 2nd 2nd magnetic layer, 3rd 3rd magnetic layer, 4, 5, 23 Nonmagnetic layer, 6 Storage layer, 10, 20 Magnetic storage element, 11 1st address wiring, 12 1st 2 address lines, 21 magnetization fixed layer, 22 antiferromagnetic layer

Claims (2)

A magnetic storage element having a storage layer for holding information by the magnetization state of the magnetic material;
Two types of wiring intersecting each other,
The magnetic memory element is arranged near the intersection of the two types of wiring;
The storage layer is configured by laminating at least two or more magnetic layers so that the magnetization directions of the upper and lower magnetic layers are antiparallel to each other,
A read magnetic layer is provided to the storage layer via a nonmagnetic layer,
Information is recorded in the storage layer by passing a current through the two types of wiring and changing the magnetization direction of the storage layer by a generated magnetic field.
A current is passed through the magnetic memory element to inject polarized electrons, thereby reversing the magnetization direction of the read magnetic layer and detecting a change in resistance of the magnetic memory element. Reads the information that is being read from the magnetic memory. 2. The magnetic memory according to claim 1 , wherein the read magnetic layer is formed to have a smaller film thickness or a smaller planar pattern than the magnetic layer of the storage layer.

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