JP2006092626A - Memory and its recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a memory in which information can be recorded at high speed and whose reliability is high. <P>SOLUTION: The memory 10 is constituted by providing a memory layer 4 holding information by a magnetization state of a magnetic object, a memory element 6 provided for this memory layer 4 through a nonvolatile layer 3 and having at least a magnetization fixed layer 2 in which a direction of magnetization is fixed, a current supply means 7 to flow current between the memory layer 4 and the magnetization fixed layer 2 through the nonmagnetic layer 3, and a magnetic field applying means 8 for applying a magnetic field to the memory element 6. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention includes a memory element having a memory layer that holds information according to the magnetization state of a magnetic substance, and a memory in which information is recorded by changing the magnetization state of the memory layer by passing a current through the memory element, and the recording thereof Related to the method.

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).

  The MRAM reverses the magnetization of the magnetic layer of the magnetic memory element at the intersection of the address lines by passing a current through two orthogonal address lines (word lines and bit lines) and by a current magnetic field generated from each address line. Information recording.

However, in order to stably hold the recorded information, a certain coercive force is required in the magnetic layer (storage layer) for recording information.
On the other hand, in order to rewrite the recorded information, a certain amount of current must be passed through the address wiring.
As the elements constituting the MRAM become finer, the address wiring becomes thinner, so that a sufficient current cannot flow.

Therefore, attention has been paid to a magnetic memory having a configuration using magnetization reversal by spin injection as a configuration capable of reversing magnetization with a smaller current (see, for example, Patent Document 1).
Magnetization reversal by spin injection is to cause magnetization reversal in another magnetic material by injecting spin-polarized electrons that have passed through the magnetic material into another magnetic material.
Magnetization reversal by spin injection has an advantage that magnetization reversal can be realized with a small current even if the element is miniaturized.

Nikkei Electronics 2001.1.22 (pages 164-171) JP 2003-17782 A

  However, in order to perform magnetization reversal by spin injection, since a current is directly passed through the storage element, it is necessary to make the recording current as small as possible so that the storage element is not destroyed or deteriorated by the recording current.

In particular, if the pulse width of the recording current is shortened in order to perform recording at high speed, the current required for recording increases, so that the failure due to deterioration or destruction of the storage element due to the increase in current increases.
For this reason, it has been difficult to realize a magnetic memory capable of high-speed operation with high reliability.

  In order to solve the above-described problems, the present invention provides a highly reliable memory capable of recording information at high speed and a recording method therefor.

  The memory according to the present invention includes at least a storage layer that holds information according to the magnetization state of a magnetic material, and a magnetization fixed layer that is provided to the storage layer via a nonmagnetic layer and whose magnetization direction is fixed. The device includes a current supply means for causing a current to flow between the storage layer and the magnetization fixed layer via the nonmagnetic layer, and a magnetic field application means for applying a magnetic field to the storage element.

  The memory recording method of the present invention includes a storage layer that holds information according to the magnetization state of a magnetic material, and a magnetization fixed layer that is provided to the storage layer via a nonmagnetic layer and whose magnetization direction is fixed. In a memory comprising at least a storage element, a current supply means for flowing a current between the storage layer and the magnetization fixed layer via a nonmagnetic layer, and a magnetic field application means for applying a magnetic field to the storage element When recording information, a current is supplied by a current supply means, a current is passed between the storage layer and the magnetization fixed layer, and a pulse magnetic field or an oscillating magnetic field is applied to the storage element by the magnetic field application means. is there.

According to the above-described memory configuration of the present invention, a storage layer that holds information according to the magnetization state of the magnetic material, and a magnetization fixed that is provided to the storage layer via a nonmagnetic layer and the magnetization direction is fixed. A storage element having at least a layer, and current supply means for causing a current to flow between the storage layer and the magnetization fixed layer via the non-magnetic layer. By flowing a current between them, information can be recorded by changing the magnetization state (magnetization direction) of the storage layer by so-called spin injection.
In addition, since a magnetic field applying unit for applying a magnetic field to the memory element is provided, when recording information, the magnetic field is applied to the memory element by the magnetic field applying unit, and the magnetization direction of the memory layer of the memory element Can be shifted from the easy magnetization axis by the action of the magnetic field, so that the magnetization direction of the memory layer can be easily reversed by spin injection. As a result, the current required to record information can be reduced, and the magnetization can be quickly reversed without undergoing the vibration of magnetization that occurs before the magnetization direction of the storage layer is reversed. become.

According to the memory recording method of the present invention described above, when information is recorded in the memory of the present invention, a current is supplied by the current supply means, and a current is supplied between the storage layer and the magnetization fixed layer. By applying a pulse magnetic field or an oscillating magnetic field to the memory element by the magnetic field applying means, the magnetization direction of the memory layer of the memory element is easily magnetized by the action of the magnetic field by the action of the pulse magnetic field or the oscillating magnetic field from the magnetic field applying means. Shifting from the axis facilitates reversal of the magnetization direction of the storage layer by spin injection. As a result, the current required for recording information can be reduced, and the magnetization reversal can be performed quickly without passing through the magnetization oscillation that occurs before the reversal of the magnetization direction of the storage layer.
In addition, since the magnetic field applied to the memory element from the magnetic field applying means is a pulsed magnetic field or an oscillating magnetic field, the effect of preventing the reversal of the magnetization direction of the memory layer due to spin injection is smaller than when a continuous magnetic field is applied. can do.

In the memory of the present invention and the recording method of the memory of the present invention, the direction of the magnetic field by the magnetic field applying means may be substantially the same as the hard axis of the storage layer of the storage element.
With such a configuration, the direction of magnetization of the storage layer can be efficiently shifted from the easy magnetization axis by a magnetic field in substantially the same direction as the hard axis of magnetization of the storage layer. As a result, even if a weak magnetic field is used, the current required for recording information can be reduced, and the effect that the magnetization can be reversed quickly can be obtained.

  In the memory recording method of the present invention, when recording information, a pulse current is supplied by the current supply means, a pulse magnetic field is applied to the storage element by the magnetic field application means, and the end of the pulse magnetic field is set to the end of the pulse current. When it is earlier or at the same time, the action of shifting the magnetization direction of the storage layer by the pulse magnetic field from the easy axis does not disturb the action of reversing the magnetization direction of the storage layer by the pulse current. As a result, the current required for recording information can be greatly reduced.

In the memory recording method of the present invention, when recording information, an alternating magnetic field is applied to the storage element by the magnetic field applying means, and the frequency of the alternating magnetic field is generated when a current is passed through the storage element. It is also possible to make it substantially the same as the oscillation frequency of the layer magnetization.
In this case, since the frequency of the alternating magnetic field is substantially the same as the frequency of the magnetization vibration of the storage layer, it is possible to efficiently assist the reversal of the magnetization of the storage layer. Therefore, the current (recording current) required for recording information can be greatly reduced. Further, the recording current can be reduced even with a weak magnetic field.

According to the present invention described above, it is possible to reduce the current (recording current) required for recording information.
As a result, failures due to deterioration or destruction of the memory element can be reduced, and the reliability of the memory can be improved. Further, since power consumption when recording information can be reduced, a memory with low power consumption can be realized.
Furthermore, when recording information by supplying a pulse current from the current supply means, the recording current increases as compared with the case of supplying a continuous current. However, according to the present invention, information recording is performed by supplying a pulse current. Even when the recording is performed, the recording current can be reduced. As a result, the pulse width of the pulse current can be shortened, information can be recorded in a short time, and the information recording speed can be increased.

  According to the present invention described above, since it is possible to perform the magnetization reversal quickly without passing through the vibration of the magnetization that occurs before the reversal of the magnetization direction of the storage layer, it is possible to record information at a high speed. It becomes possible.

  Therefore, according to the present invention, information can be recorded at high speed and a highly reliable memory can be realized.

  First, an outline of the present invention will be described prior to description of specific embodiments of the present invention.

  In order to achieve the above-described purpose, that is, to realize a memory capable of recording information with a small current and capable of recording information at high speed, the optimum structure and recording method have been studied. At least two magnetic layers of a storage layer that holds the direction (magnetization state) as information and a magnetization fixed layer (having a reference layer serving as a reference for information) in which the magnetization direction is fixed, and a nonmagnetic layer sandwiched between them In a storage element in which information is recorded by a current flowing through a nonmagnetic layer, a magnetic field is applied simultaneously when information is recorded, so that information can be recorded with a small recording current even with a short-width pulse current. We have found that it is possible to record, and it is possible to realize a highly reliable memory by reducing failures due to deterioration or destruction of the memory element.

  Here, for each case of magnetization reversal by a magnetic field and magnetization reversal by spin-polarized current injection, a magnetization locus (change in magnetization vector) was calculated. The calculation results are shown in FIGS. 1A and 1B. FIG. 1A shows the case of magnetization reversal by a magnetic field, and FIG. 1B shows the case of magnetization reversal by spin-polarized current injection. 1A and 1B, the x-axis is the film thickness direction of the magnetic material, the y-axis is the hard magnetization axis direction of the magnetic material, and the z-axis is the easy magnetization axis direction of the magnetic material.

In both FIG. 1A and FIG. 1B, the magnetization that was initially upward in the figure (z-axis component is positive) is reversed in the figure downward (z-axis component is negative). The first magnetization vector (x, y, z) is (0, 0, +1), and the magnetization vector after inversion is (0, 0, -1).
In the magnetization reversal by the magnetic field in FIG. 1A, the magnetization moves rapidly until the upward magnetization becomes downward, and the vibration of the magnetization is observed after the reversal. However, the operation until the reversal is fast, and the magnetization reversal is possible in a short time.
On the other hand, in the magnetization reversal by the spin-polarized current in FIG. 1B, magnetization oscillation is observed before the reversal. In particular, at the initial stage when the current is started to flow, a lot of time is spent only by repeating small vibrations around the easy magnetization axis.

Therefore, in order to perform the magnetization reversal faster in the magnetization reversal by spin injection, it is necessary to flow more current and reduce the number of times of magnetization oscillation until the reversal.
However, when a large amount of current is passed, the power consumption increases accordingly.

In order to operate at high speed without increasing power consumption, it is necessary to adopt another method instead of a method of increasing current.
Therefore, it is considered effective to shift the direction of magnetization from the easy magnetization axis of the storage layer by applying a magnetic field during magnetization reversal by spin injection. This method makes it possible to reduce the number of initial vibrations and shorten the time required for magnetization reversal.

At this time, if a magnetic field is applied in the hard axis direction, the direction of magnetization can be shifted from the easy axis by the weakest magnetic field.
However, when a continuous magnetic field is applied, the movement of magnetization due to spin injection is hindered by the magnetic field, so it is necessary to use a pulse magnetic field, an alternating magnetic field, or the like.

Furthermore, when applying a pulsed magnetic field, it is preferable that the end of the pulse of the magnetic field be at least earlier than the end of the pulse of the spin injection current at least in order not to disturb the movement of magnetization due to spin injection.
Also, the magnetic field pulse and the spin injection current pulse do not need to overlap, and may be separated by a certain amount of time, or the two pulse widths may be different.

In addition, the magnetic field to be applied is an oscillating magnetic field (magnetic field in which the intensity of the magnetic field oscillates) having substantially the same period as the magnetization oscillating period observed at the time of magnetization reversal by spin injection. Since reversal can be assisted, magnetization reversal can be performed with a weaker magnetic field and less current.
As the oscillating magnetic field, for example, a magnetic field whose polarity changes like an alternating magnetic field or a magnetic field whose intensity changes with the same polarity can be considered.

  Next, a specific embodiment of the present invention that satisfies the above-described configuration of the present invention will be described.

As an embodiment of the present invention, FIG. 2 shows a schematic configuration diagram (perspective view) of unit memory cells constituting a memory.
From the lower layer, the antiferromagnetic layer 1, the magnetization fixed layer (reference layer) 2 whose magnetization direction is fixed by the antiferromagnetic layer 1, the nonmagnetic layer 3, and the storage layer that holds information by the magnetization state (magnetization direction) 4 and the upper electrode layer 5 are laminated | stacked and the memory element 6 is comprised. The magnetization fixed layer (reference layer) 2 serves as a reference for the magnetization direction with respect to the storage layer 4.

A wiring (current line) 7 for flowing a current to the storage element 6 is connected on the storage element 6.
A wiring (address line) 8 for applying a magnetic field is provided slightly above the storage element 6 and above.
A selection transistor 9 is connected to the side of the antiferromagnetic layer 1 that also serves as the lower electrode layer.
A memory cell 10 is configured by the memory element 6, the current line 7, the address line 8, and the selection transistor 9 described above.
A memory can be configured by arranging a large number of memory cells 10 having the configuration shown in FIG. 2 in a column or matrix.

An antiferromagnetic material such as PtMn can be used for the antiferromagnetic layer 1.
For the magnetization fixed layer (reference layer) 2, a magnetic material having a large spin polarization such as CoFe is suitable. The magnetization fixed layer 2 may be a single layer, or may have a configuration in which a plurality of magnetic layers are laminated via a nonmagnetic layer such as Ru.
For the nonmagnetic layer 3, an insulator such as metal Cu or Al oxide that has little spin scattering in spin injection is suitable.
For the memory layer 4, a crystalline or amorphous magnetic material mainly composed of Fe, Co, and Ni can be used.
For the upper electrode layer 5, a material having good conductivity, for example, Ta or W can be used.
The current line 7 and the address line 8 are preferably composed of Al or Cu having a low resistance.

In FIG. 2, the x, y, and z axes are defined in the same manner as the respective axes in FIGS. 1A and 1B, the x axis is the thickness direction of the memory layer 4, and the y axis is the magnetization difficulty of the memory layer 4. It is the axial direction, and the z-axis is the easy axis direction of magnetization of the storage layer 4.
Since the address line 8 for applying the magnetic field is formed so as to extend in the z-axis direction, that is, the magnetization easy axis direction of the storage layer 4, the magnetization of the storage layer 4 is caused by passing a current through the address line 8. A magnetic field in the difficult axis direction (y-axis direction) can be applied.

In the memory cell 10 of the present embodiment, when information is recorded, the film thickness is measured between the antiferromagnetic layer 1 and the upper electrode layer 5 of the memory element 6 through the current line 7, the selection transistor 9, and the like. A current in the direction is supplied, and a current is supplied to the address line 8 to apply a magnetic field in the hard axis direction (y-axis direction) of the storage layer 4.
By passing a current in the thickness direction between the antiferromagnetic layer 1 and the upper electrode layer 5 of the memory element 6, a current flows between the memory layer 4 and the magnetization fixed layer 2, and the memory is stored by spin-polarized current injection. The magnetization direction of the layer 4 can be reversed. At this time, by applying a magnetic field in the hard axis direction of the storage layer 4, the magnetization direction of the storage layer 4 is shifted from the easy axis direction, and the magnetization direction is easily reversed by spin-polarized current injection. Can do.
Since the magnetization direction can be easily reversed, it can be reversed in a short time or with a smaller current.

  As described above, since the continuous magnetic field hinders the movement of magnetization of the storage layer 4, the current flowing through the address line 8 is changed to the pulse current so as to be a pulse magnetic field or an oscillating magnetic field (for example, an alternating magnetic field). , Current that vibrates, or alternating current.

In particular, when a pulse magnetic field is applied by the address line 8 and a pulse current is passed through the storage element 6 as a recording current through the current line 7, the selection transistor 9 or the like, the pulse current and the pulse magnetic field are The relationship between the timings of application is important.
In order to shift the magnetization direction of the storage layer 4 from the easy axis direction and to easily reverse the magnetization direction by spin-polarized current injection, the start of the pulse magnetic field is set simultaneously with the start of the pulse current or the pulse current It is desirable to precede the start.
Further, it is desirable that the end of the pulse magnetic field is earlier or at the same time as the end of the pulse current.

The pulse magnetic field and the pulse current may have the same pulse timing or may overlap, and the pulse widths of both may be the same or different.
Even if the end of the pulse magnetic field precedes the start of the pulse current, if the distance between them is shorter to some extent, the effect of reducing the reversal current is obtained. This is because the interval between the two pulses is short, so that the magnetization direction of the storage layer 4 is deviated from the easy magnetization axis direction by the pulse magnetic field and is completely deviated before returning to the easy magnetization axis direction. This is because the magnetization reversal is started by the spin-polarized current injection.

  In particular, when an alternating magnetic field is applied via the address line 8, the magnetization of the storage layer 4 generated when a current is passed through the storage element 6 at the frequency of the alternating magnetic field, that is, the alternating frequency applied to the address line 8. When the frequency is substantially the same as the frequency of the vibration, the effect of reducing the current required for magnetization reversal (reversal current) is increased.

According to the configuration of the memory according to the above-described embodiment, a current magnetic field is generated by flowing a current through the address line 8, thereby changing the magnetization direction of the storage layer 4 of the storage element 6 from the easy magnetization axis by the action of the magnetic field. Shifting facilitates reversal of the magnetization direction of the memory layer 4 by spin injection.
As a result, the current required for recording information can be reduced, and magnetization reversal can be performed quickly without passing through the magnetization oscillation that occurs before the reversal of the magnetization direction of the storage layer 4. .

Since the current required for recording information can be reduced, failures due to deterioration or destruction of the memory element 6 can be reduced, and the reliability of the memory can be improved. Further, since power consumption when recording information can be reduced, a memory with low power consumption can be realized.
Further, when recording information by supplying a pulse current through the current line 7, the recording current increases as compared with the case of supplying a continuous current. However, in the memory according to the present embodiment, the pulse current is supplied. Thus, even when information is recorded, the recording current can be reduced. As a result, the pulse width of the pulse current can be shortened, information can be recorded in a short time, and the information recording speed can be increased.
Further, since the magnetization reversal can be performed promptly by the action of the current magnetic field, it is possible to increase the speed of information recording.

  Therefore, it is possible to record information at high speed and to realize a highly reliable memory.

Further, according to the memory configuration of the present embodiment, the address line 8 for applying a current magnetic field to the storage element 6 is formed extending in the z-axis direction, that is, the easy magnetization axis direction of the storage layer 4. 8, the current magnetic field in the hard axis direction of the storage layer 4 can be applied.
The current magnetic field in the hard axis direction of the storage layer 4 can efficiently shift the magnetization direction of the storage layer 4 from the easy axis.
As a result, even if the current magnetic field from the address line 8 is weak, it is possible to reduce the current required for recording information, and to effect quick magnetization reversal.
Accordingly, it is possible to reduce the amount of current flowing through the address line 8 in order to generate a current magnetic field.

(Example)
Here, in the configuration of the memory / storage element of the present invention, the dimensions and composition of the storage layer were specifically set to examine the characteristics.

Then, a memory cell 20 having the configuration shown in FIG.
The memory cell 20 is slightly different from the memory cell 10 shown in FIG. That is, the lower electrode layer 11 is provided under the antiferromagnetic layer 1, and the selection transistor 9 is omitted. Further, the magnetization fixed layer 2 has a configuration in which three layers of a magnetic layer 12, a nonmagnetic layer 13, and a magnetic layer 14 are stacked, and the magnetic layer 14 serves as a reference layer. The upper electrode layer 5 also serves as a protective layer for protecting the memory layer 4.
Other configurations are the same as those of the memory cell 10 shown in FIG.

On the underlying lower electrode layer 11, an antiferromagnetic layer 1 made of a PtMn film with a thickness of 30 nm, a magnetic layer 12 made of a CoFe film with a thickness of 2 nm, and a nonmagnetic layer 13 made of a Ru film with a thickness of 0.7 nm. A magnetic layer (reference layer) 14 made of a CoFe film having a thickness of 2 nm, a nonmagnetic layer 3 made of a Cu film having a thickness of 5 nm, a memory layer 4 made of a NiFe film having a thickness of 5 nm, and a Ta film having a thickness of 10 nm. The upper electrode layer (protective layer) 5 was sequentially formed, and the memory element 6 was formed.
Next, each layer of the memory element 6 was patterned into an elliptical shape having a long side of about 200 nm and a short side of about 150 nm.
Thereafter, a current line 7 was formed on the upper electrode layer (protective layer) 5 and a wiring 8 for applying a magnetic field via an insulating layer was formed.
Next, the PtMn film of the antiferromagnetic layer 1 is regularly crystallized by heat treatment in a magnetic field of 300 ° C., 10 hours, about 1 Tesla, and the magnetization direction of the magnetic layer (reference layer) 14 of the magnetization fixed layer 21 is changed to one direction. I tried to face.
Note that the coercive force of the manufactured memory element 6 was 110 [Oe].

(Measurement of reverse current Ic)
The resistance of the memory element 6 was measured while sweeping the amount of current flowing between the lower electrode layer 11 and the upper electrode layer, and the inversion current Ic was obtained from the current value at which the resistance changed.
A current that changes the magnetization directions of the storage layer 4 and the reference layer 14 from the parallel state to the antiparallel state is defined as a negative reversal current (−Ic), and a current that changes from the antiparallel state to the parallel state is a positive reversal current. These inversion currents + Ic and −Ic were measured as (+ Ic), and ½ of the difference between the positive inversion current (+ Ic) and the negative inversion current (−Ic) was taken as the average value of the inversion current Ic.

First, when the direction of magnetization of the memory layer 4 was reversed only by the spin-polarized current passed through the memory element 6 without applying a magnetic field, the measured value and the theoretical value of the average value of the reversal current Ic were obtained. . In addition, the measured value and theoretical value of the average value of the reversal current Ic were similarly obtained by changing the pulse width (ns; nanosecond) using the spin-polarized current as a current pulse.
Note that when the pulse width is 10 ns or less, the current required for inversion becomes too large, and the memory element 6 is destroyed by flowing a large current, so that the inversion current cannot be measured. Therefore, we decided to estimate that part by theoretical values.
FIG. 4 shows the relationship between the measured value and theoretical value of the average value of the reversal current Ic and the current pulse width.
From FIG. 4, it is expected that the actually measured value almost coincides with the theoretical value, and that the reversal current Ic increases abruptly when the pulse width of the recording current is shortened from the theoretical value of the pulse width of 10 ns or less.

Next, when the direction of magnetization was reversed, when a uniform external magnetic field was applied in the hard axis direction of the recording layer 4, the relationship between the strength of the external magnetic field and the reversal current was measured. An inversion current when a current was continuously passed through the memory element 6 and an inversion current when a pulse current having a pulse width of 50 ns was passed were examined.
The measurement results are shown in FIG. FIG. 5 shows a positive inversion current (+ Ic) and a negative inversion current (−Ic), respectively. The absolute value of the current is larger in the negative inversion current.

As shown in FIG. 5, the reversal current hardly depends on the external magnetic field strength when the continuous current or the pulse current is passed.
As described above, the reversal current when a pulse current is passed is a larger value than the reversal current when a continuous current is passed.

  Next, the magnetic field applied to the memory element 6 was a pulse magnetic field having a pulse width of 10 ns, and the relationship between the magnetic field strength and the reversal current was examined. When a current is continuously passed through the memory element 6, a pulse current with a pulse width of 50 ns is passed, and a pulse current with a pulse width of 10 ns is passed, the inversion current is measured by changing the intensity of the pulse magnetic field. did. Note that the timing of the current and the pulse magnetic field is such that when the pulse current is applied, the end of the pulse magnetic field is 1 ns earlier than the end of the pulse current, and when the continuous current is applied, there is no current pulse end, so the continuous current is A pulsed magnetic field was applied at an appropriate time during the flow. The measurement results are shown in FIG.

  FIG. 6 shows that when a pulsed magnetic field is applied, the reversal current decreases as the magnetic field strength increases, unlike when a continuous magnetic field is applied. In particular, it can be seen that when the current pulse width is short, the reversal current is remarkably reduced and the effect of the magnetic field is remarkable.

  Next, the intensity of the magnetic field pulse is set to 50 [Oe], the pulse widths of the current pulse and the magnetic field pulse are both set to 3 ns, the pulse interval between the magnetic field pulse and the current pulse (the difference in time of the pulse) is changed, The average value of Ic was measured. The measurement results are shown in FIG. In FIG. 7, the pulse interval (difference in pulse time) on the horizontal axis is positive when the magnetic field pulse is first and the current pulse is later, and negative when the current pulse is first and the magnetic field pulse is later.

FIG. 7 shows that the pulse interval is positive, that is, the magnetic field pulse first has a greater effect of reducing the reversal current. Even when there is no overlap between the magnetic field pulse and the current pulse, an interval up to a certain extent (for example, +4 ns) Even in the vicinity, an effect of reducing the inversion current can be seen.
On the other hand, when the current pulse is first, it can be seen that the effect of reducing the inversion current is hardly obtained.

Next, the case where information is recorded on the storage layer by applying an alternating magnetic field to the storage element will be described.
While applying a magnetic field of 10 [Oe] to the storage element 6 in the hard axis direction of the storage layer 4, a continuous current of 0.2 mA is applied in a state where the magnetization directions of the storage layer 4 and the reference layer 14 are antiparallel. The signal observed at both ends of the storage element 6 after flowing through the storage element 6 was subjected to frequency analysis with a spectrum analyzer. The result of this analysis is shown in FIG.
From FIG. 8, a strong peak is observed at about 1.05 GHz.
Moreover, the peak seen in the vicinity of 2.1 GHz is the second harmonic component.
Therefore, it is observed that the magnetization of the storage layer 4 is oscillating at about 1.05 GHz by spin injection.

  Next, a current was passed through the memory element 6 while applying an alternating magnetic field having a frequency of 1.05 GHz, and the relationship between the magnetic field strength and the reversal current was examined. The pulse width of the current flowing through the storage element 6 is 10 ns, the frequency of the alternating magnetic field is 1.05 GHz, and the direction of the alternating magnetic field is parallel to the hard axis of magnetization of the storage layer 4, and the easy axis of magnetization of the storage layer 4 Measurements were made in parallel and in parallel. The measurement results are shown in FIG.

From FIG. 9, when an alternating magnetic field is applied parallel to the easy magnetization axis of the storage layer 4, the reversal current hardly changes even when the magnetic field strength is changed, but the alternating magnetic field is parallel to the hard magnetization axis of the storage layer 4. It can be seen that the reversal current decreases as the magnetic field strength increases.
That is, it can be seen that applying an alternating magnetic field in a direction parallel to the hard axis of magnetization of the storage layer 4 has a great effect of reducing the reversal current.
When the direction of the alternating magnetic field is inclined with respect to the hard axis and the easy axis of the storage layer 4, the effect is smaller than when the direction is parallel to the hard axis, but the reversal current is reduced. It is possible to reduce.

  Furthermore, when an alternating magnetic field was applied parallel to the hard axis of magnetization of the storage layer 4, the alternating magnetic field frequency was changed to 0.7 GHz, 1 GHz, and 1.5 GHz, and the relationship between the magnetic field strength and the reversal current was examined. The measurement results are shown in FIG.

  From FIG. 10, at 1 GHz close to the peak of the frequency (see FIG. 8) observed when a current is passed through the memory element 6, the effect of reducing the reversal current due to the alternating magnetic field is great. It can be seen that the effect of reducing the reversal current is reduced.

In the above-described embodiment, the storage element 6 in which the antiferromagnetic layer 1 and the magnetization fixed layer 2 including the reference layer are provided below the storage layer 4 is configured. In addition, the memory element may be configured by providing an antiferromagnetic layer as an upper layer.
Note that the antiferromagnetic layer may be omitted if the magnetization direction can be fixed by the magnetization fixed layer alone.
Further, each magnetic layer of the magnetization fixed layer and the storage layer may be formed by stacking a plurality of magnetic layers having different materials and compositions.

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

It is a locus of magnetization at the time of magnetization reversal obtained by calculation. A This is a case of magnetization reversal by a magnetic field. This is the case of magnetization reversal by B spin polarization current. 1 is a schematic configuration diagram (perspective view) of a unit memory cell of a memory according to an embodiment of the present invention. It is a schematic block diagram (perspective view) of the memory cell of an Example. It is a figure which shows the relationship between the measured value of the pulse width of the electric current pulse sent through the memory | storage element of FIG. 3, and the average value of a reverse current, and a theoretical value. It is a figure which shows the relationship between the magnetic field intensity at the time of applying a continuous magnetic field to the memory element of FIG. 3, and an inversion current. It is a figure which shows the relationship between the magnetic field intensity at the time of applying a pulse magnetic field to the memory element of FIG. 3, and an inversion current. It is a figure which shows the average change of the inversion current with respect to a pulse interval at the time of applying the current pulse and magnetic field pulse of 3 ns pulse width to the memory element of FIG. It is a figure which shows the frequency spectrum of the signal observed when an electric current is sent through the memory element of FIG. It is a figure which shows the relationship between the magnetic field intensity at the time of applying an alternating magnetic field to the memory element of FIG. 3, and an inversion current. It is a figure which shows the relationship between a magnetic field intensity | strength when changing the frequency of an alternating magnetic field at the time of applying an alternating magnetic field to the memory element of FIG. 3, and an inversion current.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Antiferromagnetic layer, 2 Magnetization fixed layer, 3,13 Nonmagnetic layer, 4 Memory layer, 5 Upper electrode layer, 6 Memory element, 7 Current line, 8 Address line (Wiring for applying a magnetic field), 10, 20 memory cells, 11 lower electrode layer, 12 magnetic layer, 14 magnetic layer (reference layer)

Claims (6)

A storage element having at least a storage layer that retains information according to a magnetization state of a magnetic material, and a magnetization fixed layer that is provided to the storage layer via a nonmagnetic layer and whose magnetization direction is fixed;
Current supply means for causing a current to flow between the storage layer and the magnetization fixed layer via the nonmagnetic layer;
A memory comprising: magnetic field applying means for applying a magnetic field to the memory element.   The memory according to claim 1, wherein the direction of the magnetic field by the magnetic field applying unit is substantially the same as the hard axis of magnetization of the storage layer of the storage element. A storage element having at least a storage layer that retains information according to a magnetization state of a magnetic material, and a magnetization fixed layer that is provided to the storage layer via a nonmagnetic layer and whose magnetization direction is fixed;
Current supply means for causing a current to flow between the storage layer and the magnetization fixed layer via the nonmagnetic layer;
In a memory comprising a magnetic field applying means for applying a magnetic field to the storage element,
When recording information, a current is supplied by the current supply means, a current is passed between the storage layer and the magnetization fixed layer, and a pulse magnetic field or an oscillating magnetic field is applied to the storage element by the magnetic field application means. A method for recording in a memory, comprising: applying.   When recording information, whether a pulse current is supplied by the current supply means, a pulse magnetic field is applied to the storage element by the magnetic field application means, and the end of the pulse magnetic field is made earlier than the end of the pulse current 4. The memory recording method according to claim 3, wherein the same time is set.   When recording information, an alternating magnetic field is applied to the storage element by the magnetic field applying means, and the frequency of the alternating magnetic field is applied to the vibration of the magnetization of the storage layer that occurs when a current is passed through the storage element. 4. The memory recording method according to claim 3, wherein the frequency is substantially the same. 4. The memory recording method according to claim 3, wherein the direction of the magnetic field by the magnetic field applying unit is substantially the same as the hard axis of magnetization of the storage layer of the storage element.

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