JP2005183826A - Magnetic memory - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a megnetic memory being capable of recording an information by the small quantity of a current even when the coercive force of a storage layer is increased by the shrinkage of a magnetic storage element and being stable against the change of an ambient temperature. <P>SOLUTION: The magnetic memory has the magnetic storage element with a storage layer 3 preserving the information by a magnetized state and heating mechanisms 4 heating the storage layer 3 for the magnetic storage element. The memory is constituted so that the layer 3 is composed of a plurality of magnetic layers containing two layers of the magnetic layers 1 and 2 having mutually different Curie temperature or compensation temperature, and the layer 3 is heated at a temperature, which does not exceed the Curie temperature or the compensation temperature of the magnetic layer having highest Curie temperature or compensation temperature, by the heating mechanisms 4 when the information is recorded. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a magnetic memory and is suitable for use in 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 MRAM, a magnetic layer (storage layer) that records and holds information is formed into a rectangular shape such as a rectangle or an ellipse, and the recorded information is stabilized by stabilizing the magnetization by shape anisotropy using the demagnetizing field. Is held for a long time. As a result, it can be used as a nonvolatile memory.
In addition, information is recorded in a magnetic memory element at the intersection of the address lines by passing a current through each of two orthogonal address lines (for example, word lines and bit lines) and generating a current magnetic field. This is done by reversing the magnetization direction of the magnetic layer (memory layer) to be held.

In the future, in MRAM, it is necessary to increase the density in order to increase the storage capacity or to reduce the size of the device, and further reduction in the size of the magnetic storage element constituting the memory cell is required. .
In order to be able to retain information for a long period of time even when the size of the magnetic memory element is reduced, the magnetic anisotropy of the magnetic memory element, particularly the magnetic anomaly of the magnetic layer (memory layer) on which information is recorded and retained is determined. It is necessary to increase the direction.

  However, if the magnetic anisotropy of the storage layer is increased, the coercive force of the storage layer increases, and a large current is required for recording information. Therefore, an increase in power consumption and an increase in the size of the current drive circuit are inevitable. This is a problem in realizing a high-density memory.

Therefore, as a method of reducing the current (recording current) necessary for recording information, a method of temporarily lowering the coercive force of the magnetic layer (storage layer) that holds the information in a magnetized state by heating the magnetic storage element ( For example, see Patent Document 1).
By adopting this method, the coercive force of the storage layer at the time of recording can be reduced and the recording current can be reduced, so that information can be recorded easily.

FIG. 10 schematically shows an example of a magnetic memory that has been conventionally proposed and has a configuration in which a heating mechanism is provided to heat the storage layer of the magnetic storage element. FIG. 10A shows a schematic plan view of a unit memory cell constituting the magnetic memory, and FIG. 10B shows a schematic sectional view of the unit memory cell.
As shown in FIG. 10A, a magnetic layer having an elliptical plane pattern constitutes a storage layer 51, that is, a magnetic layer that holds information in a magnetized state.
In parallel with the memory layer 51, a resistance element 52 is disposed, and electrodes are connected to the left and right ends of the resistance element 52. The memory layer 51 and the resistance element 52 are electrically insulated.
In this magnetic memory, by passing a current through the electrode 53 to the resistance element 52, the resistance element 52 can generate heat and the memory layer 51 can be heated. That is, the resistance element 52 constitutes a heating mechanism for the memory layer.
Nikkei Electronics 2001.1.22 (pages 164-171) JP 2002-245774 A

  In the magnetic memory having the configuration shown in FIG. 10 described above, in order to reduce the coercive force of the storage layer 51 by heating, a magnetic material having a low Curie temperature and a large temperature change in magnetic characteristics is used as the material of the storage layer 51. It is necessary to use it.

  However, such a magnetic material having a large temperature change in magnetic characteristics has a problem that the change in magnetic characteristics becomes large even with a change in environmental temperature.

  In order to solve the above-described problem, in the present invention, even when the coercive force of the storage layer is increased by reducing the size of the magnetic storage element, information can be recorded with a small amount of current. The present invention provides a magnetic memory that is stable against changes.

  The magnetic memory of the present invention includes a magnetic storage element having a storage layer for storing information according to a magnetization state, and a heating mechanism for heating the storage layer of the magnetic storage element, and the storage layers have different Curie temperatures or compensation temperatures. When recording information, the storage layer has a temperature that does not exceed the Curie temperature or compensation temperature of the magnetic layer having the highest Curie temperature or compensation temperature by a heating mechanism. Is heated.

According to the configuration of the magnetic memory of the present invention described above, the storage layer is composed of a plurality of magnetic layers including two magnetic layers having different Curie temperatures or compensation temperatures. Even if the magnetization of the magnetic layer with a low compensation temperature is decreased, the magnetic layer with a high Curie temperature or the compensation temperature is recorded by the magnetic layer with a high Curie temperature or the compensation temperature because the change in magnetization and coercive force is small. Information (magnetization state) is retained.
Therefore, it is possible to hold the recorded information stably even when the environmental temperature rises.
When recording information, the magnetization of the magnetic layer having a low Curie temperature or compensation temperature is reduced by heating, the coercive force is reduced, and the recording can be easily performed with a small amount of recording current. to enable.
Also, when recording information, the storage layer is heated by the heating mechanism at a temperature that does not exceed the Curie temperature or compensation temperature of the magnetic layer having the highest Curie temperature or compensation temperature, so the Curie temperature or compensation temperature is the highest. The magnetization of the high magnetic layer is not lost, and stable repeated operation is possible.

In the magnetic memory of the present invention, the temperature distribution of the storage layer when the storage layer is heated by the heating mechanism may be not uniform in the storage layer.
With such a configuration, when the storage layer is heated, the temperature of a part of the region in the storage layer is increased, and the coercive force of the part of the region is greatly reduced. Thus, the coercive force can be reduced efficiently, and recording can be performed with a smaller amount of recording current.

In the magnetic memory of the present invention, the cooling rate of the storage layer after being heated by the heating mechanism may be not uniform in the storage layer.
With this configuration, when the storage layer is cooled after being heated, a temperature distribution is formed in the storage layer, and the region where the cooling rate is low has a higher temperature and a lower coercive force than the other regions. Therefore, it is possible to perform recording with a smaller recording current.

In the magnetic memory of the present invention, it is possible to adopt a configuration in which the magnetizations of at least two of the magnetic layers constituting the storage layer are arranged in antiparallel.
By adopting such a configuration, the magnetizations of the two anti-parallel magnetic layers cancel each other, so that the total magnetization (apparent magnetization) of the entire storage layer becomes smaller, and recording can be performed with a smaller amount of recording current. Since the combined magnetization of the entire storage layer does not change greatly with changes in environmental temperature, information recorded in the recording layer can be stably held.

In the magnetic memory of the present invention, at least one magnetic layer of a plurality of magnetic layers constituting the storage layer may be made of a ferrimagnetic material.
By adopting such a configuration, the ferrimagnetic material has a compensation temperature at a relatively low temperature above room temperature, and the magnetization direction is reversed before and after the compensation temperature, so that the change in magnetization of the magnetic layer due to heating increases. . This makes it possible to perform recording with a smaller amount of recording current.

According to the above-described present invention, it is possible to stably maintain recording even when the environmental temperature changes, and it is possible to record information with a small recording current.
As a result, even if the coercive force of the storage layer increases due to the reduction in the size of the magnetic storage element, it is possible to record information with a small amount of current, so that power consumption during recording can be reduced, By downsizing the magnetic storage element of the memory cell, it is possible to increase the storage capacity, increase the density, increase the integration, and reduce the size of the magnetic memory.

  In addition, the temperature distribution of the memory layer when the memory layer is heated by the heating mechanism is not uniform in the memory layer, or the cooling rate of the memory layer after being heated by the heating mechanism is uniform in the memory layer. When the configuration is not, recording can be performed with a recording current of a smaller amount of current.

  A schematic configuration diagram of an embodiment of a magnetic memory of the present invention is shown in FIGS. 1A and 1B. FIG. 1A is a schematic plan view of a unit memory cell constituting the magnetic memory, and FIG. 1B is a schematic sectional view of the unit memory cell.

The two magnetic layers, the lower first magnetic layer 1 and the upper second magnetic layer 2, constitute a storage layer 3 that holds information in a magnetized state. The storage layer 3 constitutes a magnetic storage element.
As shown in FIG. 1A, the upper second magnetic layer 2 is formed in an elliptical plane pattern. Thereby, it has shape anisotropy in the left-right direction in the figure. The lower first magnetic layer 1 is also formed in the same elliptical planar pattern as the second magnetic layer 2 although not shown.
The lower first magnetic layer 1 is connected to the electrode 4 at both left and right ends. Thus, a current can be passed through the storage layer 3 such as the first magnetic layer 1 through the electrode 4.

In the present embodiment, in particular, the Curie temperature or compensation temperature of the two magnetic layers 1 and 2 constituting the storage layer 3 of the magnetic storage element is made different.
For example, the lower first magnetic layer 1 is a magnetic layer having a high Curie temperature or compensation temperature, and the upper second magnetic layer 2 is a magnetic layer having a low Curie temperature or compensation temperature.
Alternatively, the lower first magnetic layer 1 is a magnetic layer having a low Curie temperature or compensation temperature, and the upper second magnetic layer 2 is a magnetic layer having a high Curie temperature or compensation temperature.

Examples of the material for the magnetic layer having a high Curie temperature include NiFe and CoFe.
Examples of the material for the magnetic layer having a low Curie temperature include NiFeMn, CoFeCr, Ni, and GdFe.
Examples of the material for the magnetic layer having a compensation temperature include ferrimagnetic materials having a compensation temperature above room temperature, such as GdFeCo and TbCo.

As described above, when the Curie temperature or the compensation temperature of the two magnetic layers 1 and 2 are different from each other, a current is passed through the storage layer 3 through the electrode 4 to heat the storage layer 3 and raise the temperature. Of the two magnetic layers 1 and 2 constituting the memory layer 3, in the magnetic layer having a low Curie temperature or compensation temperature, the saturation magnetization is lowered and the coercive force is lowered. This makes it possible to record information on the storage layer 3 with a small amount of recording current.
On the other hand, among the two magnetic layers 1 and 2 constituting the storage layer 3, in the magnetic layer having a high Curie temperature or compensation temperature, even if the storage layer 3 is heated to increase the temperature, the change in coercive force is small. . For this reason, even when the environmental temperature rises and the temperature of the entire storage layer 3 rises, the change in magnetization of the magnetic layer having a high Curie temperature or compensation temperature is small and the change in coercive force is also small. It becomes possible to hold stably.

  In particular, when a ferrimagnetic material having a compensation temperature above room temperature is used as a magnetic layer having a low Curie temperature or a compensation temperature, the magnetization direction is reversed at temperatures above and below the compensation temperature, and the magnetization changes due to a temperature difference. Is likely to occur.

In the present embodiment, the operating temperature (the temperature at which information is recorded on the storage layer 3 and the temperature at which the information recorded on the recording layer 3 is read) is set to the two magnetic layers 1 and 2 constituting the storage layer 3. The Curie temperature or the compensation temperature of the magnetic layer having a high compensation temperature is set to a temperature not exceeding the Curie temperature or the compensation temperature.
As a result, the magnetization of the magnetic layer having a high Curie temperature or compensation temperature is not lost, and a stable repeated operation can be performed.

  Furthermore, in the present embodiment, since the electrodes 4 are connected to both end portions of the lower first magnetic layer 1, when current is passed through the electrodes 4, the portions on the electrodes 4 of the storage layer 3 (both ends) (Part) has a small amount of current, and the amount of current in the central portion of the memory layer 3 is large. As a result, the central portion of the memory layer 3 has a larger amount of heat generation and a higher temperature rise than the both end portions.

As described above, since the temperature rise in the central portion of the storage layer 3 is large, even if there is almost no change in the magnetization of the magnetic layer having a high Curie temperature or compensation temperature, the central portion of the magnetic layer having a low Curie temperature or compensation temperature can be obtained. Since the saturation magnetization is extremely lowered, the balance of magnetization is lost and the coercive force is lowered, so that information can be recorded on the storage layer 3 with a smaller amount of recording current. It becomes possible.
On the other hand, when the environmental temperature rises, the temperature of the entire storage layer 3 rises uniformly, so that the magnetization of the magnetic layer with a low Curie temperature or compensation temperature decreases, but the balance of magnetization is not lost, There is almost no change in magnetization of the magnetic layer having a high Curie temperature or compensation temperature, and the change in coercive force is small. For this reason, the information recorded in the storage layer 3 is stably held.

Further, for example, when the electrode 4 is made of a material having a high thermal conductivity (for example, copper), the cooling rate at both ends of the memory layer 3 in contact with the electrode 4 after the heating is stopped increases, and the central portion of the memory layer 3 is increased. The temperature of becomes relatively high. Also in this case, the saturation magnetization of the central portion of the magnetic layer having a low Curie temperature or compensation temperature is extremely lowered and the balance of magnetization is lost. Information can be recorded in the storage layer 3.
In addition, instead of configuring the electrode 4 with a material having a high thermal conductivity, for example, a similar effect can be obtained even if heat sinks are attached to both ends of the memory layer 3 to facilitate heat dissipation.

Furthermore, in order to reduce the change in the coercive force of the storage layer with respect to changes in the environmental temperature and increase the decrease in the coercive force of the storage layer with respect to partial heating, the magnetization direction of the first magnetic layer 1 and the second magnetic layer The two magnetization directions are preferably antiparallel to each other.
For this purpose, for example, a nonmagnetic layer having an appropriate thickness is formed between the first magnetic layer 1 and the second magnetic layer 2, and a magnetic layer is formed between the two magnetic layers 1 and 2. What is necessary is just to make a coupling | bonding and exchange interaction work.
If one magnetic layer is made of a ferromagnetic material made of a transition metal and the other magnetic layer is made of a ferrimagnetic material made of a rare earth and a transition metal and having a compensation temperature equal to or higher than room temperature, The magnetization of the body and the magnetization of the ferrimagnetic material are antiparallel.

  A magnetic memory having a large number of memory cells can be configured by arranging a large number of memory cells having the configuration shown in FIGS. 1A and 1B.

According to the configuration of the magnetic memory of the present embodiment described above, the storage layer 3 of the magnetic storage element forming each memory cell has two magnetic layers having different Curie temperatures or compensation temperatures (the first magnetic layer 1). And the second magnetic layer 2), when information is recorded, the magnetization of the magnetic layer having a low Curie temperature or compensation temperature is reduced by heating, thereby reducing the coercive force and reducing the amount of current. It is possible to easily perform recording with a recording current of.
On the other hand, a magnetic layer having a high Curie temperature or compensation temperature retains recorded information (magnetization state) because the change in magnetization and coercive force due to temperature rise is small.
Therefore, the information recorded in the storage layer 3 can be stably held even when the environmental temperature rises.

  Further, according to the present embodiment, the operating temperature is set not to exceed the Curie temperature or the compensation temperature of the magnetic layer having a high Curie temperature or the compensation temperature, so that the magnetization of the magnetic layer having the high Curie temperature or the compensation temperature is increased. Stable and repeatable operation is possible without being lost.

Further, according to the present embodiment, the electrode 4 is directly connected to both end portions of the first magnetic layer 1 below the memory layer 3, and a current is passed through the memory layer 3 through the electrode 4. It is configured to heat. As a result, a large amount of current flows through the central portion of the storage layer 3, and heat generation increases, so that the temperature rise in the central portion of the storage layer 3 increases and the temperature becomes higher than both end portions of the storage layer 3. That is, a non-uniform temperature distribution is formed in the memory layer 3.
When the storage layer is uniformly heated, the coercive force cannot be changed so much, but by forming a non-uniform temperature distribution in the storage layer, the magnetic layer constituting the storage layer 3 can be efficiently formed. The coercive force can be changed.
Further, when the electrode 4 is made of a material having a high thermal conductivity, the cooling rate at both ends of the memory layer 3 is increased at the time of cooling after heating, so that the temperature of the central part of the memory layer 3 is relatively increased. Therefore, the temperature distribution can be formed in the storage layer 3 and the coercive force of the magnetic layer constituting the storage layer 3 can be changed efficiently.

According to the present embodiment, since the coercive force of the magnetic layer can be changed efficiently in this way, it is possible to record information even if heating is performed with a smaller current amount. It becomes possible to reduce the current.
Therefore, it is possible to reduce the amount of current required for recording and reduce power consumption during recording.
In addition, even if the coercive force of the storage layer increases due to the reduction of the magnetic memory element, it becomes possible to record information with a small amount of current. Therefore, by reducing the magnetic memory element constituting the memory cell, It is possible to increase the storage capacity, increase the density, increase the integration, and reduce the size of the magnetic memory.

  In the above-described embodiment, the magnetic memory element that constitutes each memory cell is formed by only the memory layer 3, but the magnetic memory element may be formed of, for example, a magnetization fixed layer or an antiferromagnetic layer whose magnetization direction is fixed. It is also possible to adopt a configuration in which a magnetic layer other than the storage layer or another nonmagnetic layer is provided.

Further, in the above-described embodiment, the temperature distribution is formed in the memory layer 3 by connecting the electrodes 4 to both ends of the memory layer 3 and causing the memory layer 3 to flow through the electrode 4 to generate heat. However, it is also possible to form a temperature distribution in the memory layer by other methods.
For example, even if only a part of the storage layer is heated by a heating mechanism provided outside the storage layer, it is possible to form a temperature distribution in the storage layer in the same manner.
Further, even when a plurality of materials having different thermal conductances are brought into contact with the storage layer, it is possible to form a temperature distribution in the storage layer due to a difference in heat dissipation rate.

In the above-described embodiment, the storage layer 3 is composed of the two magnetic layers 1 and 2, but in the present invention, the storage layer may be composed of three or more magnetic layers.
When the storage layer is constituted by three or more magnetic layers, the Curie temperature or the compensation temperature is different for at least two of the magnetic layers constituting the storage layer (three or more layers). The operating temperature is a temperature that does not exceed the Curie temperature or compensation temperature of the magnetic layer having the highest Curie temperature or compensation temperature.
Furthermore, in order to reduce the change in the coercive force of the storage layer with respect to the change in the environmental temperature and increase the decrease in the coercive force of the storage layer with respect to partial heating, among the magnetic layers (three or more layers) constituting the storage layer, It is desirable that the magnetizations of at least a pair (two layers) of magnetic layers are arranged antiparallel.
It is particularly desirable that the magnetic layer having a low Curie temperature or compensation temperature and the layer having a high Curie temperature or compensation temperature are arranged in antiparallel.

Here, a method of manufacturing the magnetic memory having the configuration shown in FIG. 1 will be described with reference to FIGS. 2A to 2E. 2A to 2E show magnetic memory elements of two memory cells arranged side by side.
First, as shown in FIG. 2A, a part of the insulating layer 5 formed on the substrate is removed to form a trench 5A for wiring embedding.
Next, after the metal is entirely formed so as to fill the groove 5A, the surface is polished and flattened to expose the insulating layer 5 as shown in FIG. 2B. Thereby, the electrode 4 made of metal is formed in the groove 5A.
Next, as shown in FIG. 2C, the magnetic memory element 7 including the memory layer 3 is formed on the electrode 4 so that both end portions are electrically connected to the electrode 4.
Next, after forming the insulating layer 8 so as to cover the surface, as shown in FIG. 2D, a part of the insulating layer 8 on the magnetic memory element 7 is removed to form a hole to expose the magnetic memory element 7. .
Subsequently, the hole of the insulating layer 8 is filled to form an electrode layer entirely, and the electrode layer is patterned to form an upper electrode 9 connected to the magnetic memory element 7 as shown in FIG. 2E.
The electrode (lower electrode) 4 is formed so that a current can flow through the electrode 4 by being connected to a wiring or the like (not shown).
In this manner, a magnetic memory having the memory cell having the configuration shown in FIG. 1 can be manufactured.

(Example)
Here, in the configuration of the magnetic memory according to the present invention, the dimensions and the magnetization amount of the storage layer of the magnetic storage element were specifically set, and the characteristics were examined.

First, the difference in characteristics between the case where the memory layer was heated uniformly and the case where a part of the memory layer was heated to form a non-uniform temperature distribution was examined.
FIG. 3A is a plan view showing a plan view (a shape used for track and track pits of an athletics track) and a magnetic memory element 30 having a size of 100 nm × 200 nm as a first model. It comprised so that sectional drawing might be shown.
In this magnetic memory element 30, a first magnetic layer 31 having a thickness of 2 nm, a saturation magnetic flux density Ms of 800 emu / cm ³ , a high Curie temperature, a nonmagnetic layer 32 having a thickness of 1 nm, The memory layer 34 is configured by stacking a second magnetic layer 33 having a thickness of 10 nm, a saturation magnetic flux density Ms ′ (400 emu / cm ³ at room temperature), and a low Curie temperature.
This first model assumes a case where the entire storage layer is uniformly heated, and the saturation magnetic flux density Ms ′ of the second magnetic layer 33 having a low Curie temperature decreases as the temperature rises. And

Further, as shown in the plan view of FIG. 4A, the planar shape of the magnetic memory element is the same as that of FIG. 3A, but a magnetic memory element 40 having a different memory layer configuration is adopted as the second model, and the cross section of FIG. The configuration was as shown in the figure.
In the magnetic memory element 40, the first magnetic layer 31 and the nonmagnetic layer 32 have the same configuration as that in FIG. 3B, but the central portion 36A having a width of 70 nm in the second magnetic layer 36 has a saturation magnetic flux density Ms ′. (The room temperature is 400 emu / cm ³ ), and both end portions 36B have a saturation magnetic flux density Ms (800 emu / cm ³ ). The thickness of the second magnetic layer 36 was 10 nm, which is the same as that of the second magnetic layer 33 in FIG. 3A. Then, the first magnetic layer 31, the nonmagnetic layer 32, and the second magnetic layer 36 are stacked to constitute the storage layer 37.
This second model assumes a case where a part of the storage layer (center portion) is heated to form a non-uniform temperature distribution in the storage layer. Of the second magnetic layer 36 having a low Curie temperature, It is assumed that the saturation magnetic flux density Ms ′ of the central portion 36A decreases with an increase in temperature, and both end portions 36B of the second magnetic layer 36 maintain a high saturation magnetic flux density Ms.

  In any model, it is assumed that the magnetization direction of the first magnetic layer 31 and the magnetization directions of the second magnetic layers 33 and 36 are antiparallel to each other due to magnetostatic coupling.

With respect to the first model and the second model, the saturation magnetic flux density Ms ′ of the second magnetic layers 33 and 36 having a low Curie temperature is changed, and the storage layers 34 and 37 at the respective values of the saturation magnetic flux density Ms ′. The coercive force of was calculated by micromagnetic.
The calculation results are shown in FIG. In FIG. 5, curve A shows the case of the first model, and curve B shows the case of the second model.

From FIG. 5, in the first model in which the saturation magnetic flux density Ms ′ of the entire second magnetic layer 33 decreases, as shown by the curve A, the coercive force slightly decreases as the saturation magnetic flux density decreases. It will not drop below a certain level.
On the other hand, in the second model in which the saturation magnetic flux density Ms ′ of only the central portion 36A of the second magnetic layer 36 is lowered, as shown by the curve B, the coercive force is increased as the saturation magnetic flux density is lowered. It decreases monotonously, and the coercive force becomes zero when the saturation magnetic flux density is 100 emu / cm ³ or less.
That is, even when the temperature is the same (the saturation magnetic flux density Ms ′ is the same in FIG. 4), when locally heated, the coercivity of the magnetic layer is greatly reduced compared to when the whole is heated. Understand.
Therefore, by locally heating the storage layer, the decrease in the coercivity of the magnetic layer constituting the storage layer can be increased, and information can be recorded efficiently by changing the magnetization state of the magnetic layer. I understand.

Subsequently, as shown in a plan view in FIG. 6A, the magnetic memory has the same planar shape as the magnetic memory element 30 in FIG. 3A and the magnetic memory element 40 in FIG. 4A and has a size of 1.2 μm × 0.5 μm. The element 10 was adopted as a third model and configured as shown in a cross-sectional view in FIG. 6B.
In the magnetic memory element 10, both left and right end portions in the figure are formed on the electrodes 23, and the distance between the electrodes 23 on both sides is 0.5 μm.
Further, as shown in FIG. 6B, the laminated structure of the magnetic memory element 10 is formed from a lower layer, an underlayer 11 made of a Ta film with a thickness of 10 nm, and a NiFeCu film with a thickness of 10 nm at a low Curie temperature (about 200 ° C.). A certain first magnetic layer 12, a nonmagnetic layer 13 made of a Ru film with a thickness of 2 nm, a second magnetic layer 14 made of a CoFe film with a thickness of 3 nm and a high Curie temperature, and an Al film with a thickness of 1 nm are formed. After that, a tunnel insulating layer 15 made of an aluminum oxide film formed by plasma oxidation treatment, a third magnetic layer 16 made of a CoFe film having a thickness of 2 nm, a nonmagnetic layer 17 made of a Ru film having a thickness of 0.8 nm, a film A fourth magnetic layer 18 made of a CoFe film having a thickness of 2 nm, an antiferromagnetic layer 19 made of a PtMn film having a thickness of 30 nm, and an upper electrode 20 made of a Ta film having a thickness of 30 nm were used.
The first magnetic layer 12, the nonmagnetic layer 13, and the second magnetic layer 14 constitute a storage layer 21. Further, the magnetization directions of the third magnetic layer 16 and the fourth magnetic layer 18 are fixed by the antiferromagnetic layer 19. The third magnetic layer 16, the nonmagnetic layer 17, and the fourth magnetic layer 18 constitute a magnetization fixed layer (reference layer) that serves as a reference for the magnetization direction of the storage layer 21.
In FIG. 6, reference numeral 24 denotes an insulating layer that insulates the two electrodes 23.

  That is, in the magnetic memory element 10 of the third model, the memory layer 21 is constituted by the first magnetic layer 12 and the second magnetic layer 14 having different Curie temperatures, and is connected to both end portions of the magnetic memory element 10. A current can be passed through the storage layer 21 of the magnetic memory element 10 through the electrode 23, which satisfies the configuration of the magnetic memory element of the magnetic memory of the present invention.

For this third model magnetic memory element 10, the temperature change in each part of the first magnetic layer 12 (which has a low Curie temperature) when a pulse current is passed between the left and right electrodes 23 is calculated. Asked. The calculation results are shown in FIG. In FIG. 7, the horizontal axis indicates the position (center to both ends) in the magnetic memory element 10, and the vertical axis indicates the temperature. The pulse width of the pulse current is 1 nsec. Then, the time t (nsec) elapsed from the start time of the pulse current is changed. When t = 0, the curve A, when t = 0.5, the curve B, and when t = 1.0 (pulse The curve C is shown when the current is finished), the curve D when t = 1.5, the curve E when t = 2.0, and the curve F when t = 3.0.
Note that the calculation is made assuming that all the materials around the magnetic memory element 10 are SiO ₂ .

As can be seen from FIG. 7, when a current is passed through the magnetic memory element 10, the temperature at the central portion of the element increases particularly greatly, and the temperature distribution increases. Then, after the current is stopped (curve D), the temperature at the end of the element rises as the temperature of the central portion decreases.
Further, after 3 nm, the temperature is slightly higher than the initial state, but the temperature distribution is almost flat.

Subsequently, as a configuration of the present invention, a configuration similar to that of the embodiment shown in FIG. 1 (a configuration in which a part of a storage layer composed of two magnetic layers is heated) and a comparative example in which a storage layer is provided The change in the coercive force of the memory layer due to the temperature change was obtained by calculation when the memory layer was composed of a single magnetic layer having a low Curie temperature and was uniformly heated in the same manner as in FIG.
Specifically, the temperature rise of the memory layer when the memory layer is heated (by current) is calculated from the specific heat of the material of each layer constituting the memory layer, and the temperature change of the temperature of each part and the magnetization of the component material From this, the magnetization of the memory layer was estimated, the magnetization distribution of the entire memory layer was obtained, and the coercive force of the memory layer was calculated from the magnetization distribution by micromagnetics. Then, it was assumed that heating was performed by passing an electric current, and the current was stopped when the coercive force Hc became 1/10 of the initial coercive force value Hc0. The amount of current was 5 mA in all cases.
The calculation results are shown in FIG. FIG. 8 shows a change in coercive force with respect to the elapsed time t, and the case of the configuration of the present invention is shown by a curve I, and the case of a comparative example is shown by a curve II.

FIG. 8 shows that curve I and curve II are compared. In the case of the configuration in which a part of the memory layer of the present invention is heated, the change in coercive force is large with respect to the elapsed time t. It can be seen that the magnetic recovery is fast.
Therefore, a high-speed recording operation can be expected by heating a part of the memory layer of the present invention.

Next, as a configuration of the present invention, in the same configuration as that of the embodiment shown in FIG. 1 (a configuration in which a part of the storage layer composed of two magnetic layers is heated), it is connected to both end portions of the storage layer. The coercive force at each current value was calculated by changing the current value when a pulse current was passed between the electrodes. In both cases, the pulse width of the pulse current is 3 nsec.
The calculation results are shown in FIG.

  From FIG. 9, it can be confirmed that when the pulse current is 2 mA or more, the coercive force is remarkably reduced, which is effective in reducing the operating current.

  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.

1A and 1B are schematic configuration diagrams of one unit memory cell of a magnetic memory according to an embodiment of the present invention. 8A to 8E are process diagrams showing a method for manufacturing the magnetic memory of FIG. 1. It is a figure which shows the 1st model of A and B magnetic memory elements. It is a figure which shows the 2nd model of A and B magnetic memory elements. FIG. 5 is a diagram illustrating a relationship between a saturation magnetic flux density and a coercive force in the models of FIGS. 3 and 4. A and B are views showing a third model (configuration of the magnetic memory of the present invention) of the magnetic memory element. In the model of FIG. 6, it is a figure which shows the time change of the temperature distribution in each position of a memory | storage layer when a pulse current is sent. It is a figure which shows the time change of a coercive force when a pulse current is sent with respect to the structure which heats a part of memory | storage layer of this invention, and the structure of a comparative example, respectively. It is a figure which shows the relationship between the electric current amount when a pulse current is sent with respect to the magnetic memory of the structure which heats a part of memory | storage layer of this invention, and a coercive force. A and B are schematic configuration diagrams of a magnetic memory configured to heat a storage layer of a magnetic storage element by providing a conventionally proposed heating mechanism.

Explanation of symbols

1, 12, 31 First magnetic layer, 2, 14, 33, 36 Second magnetic layer, 3, 21, 34, 37 Storage layer, 4, 23 Electrode 10, 30, 40 Magnetic storage element 13, 17, 32 Nonmagnetic layer, 15 tunnel insulating layer, 19 antiferromagnetic layer, 22 magnetization fixed layer (reference layer)

Claims (5)

A magnetic storage element having a storage layer for storing information according to a magnetization state;
A heating mechanism for heating the storage layer of the magnetic storage element,
The storage layer is composed of a plurality of magnetic layers including two magnetic layers having different Curie temperatures or compensation temperatures,
When recording information, the memory layer is heated by the heating mechanism at a temperature not exceeding the Curie temperature or compensation temperature of the magnetic layer having the highest Curie temperature or compensation temperature. .   The magnetic memory according to claim 1, wherein a temperature distribution of the storage layer when the storage layer is heated by the heating mechanism is not uniform in the storage layer.   The magnetic memory according to claim 1, wherein a cooling rate of the storage layer after being heated by the heating mechanism is not uniform in the storage layer.   2. The magnetic memory according to claim 1, wherein magnetizations of at least two magnetic layers among the plurality of magnetic layers constituting the storage layer are arranged in antiparallel. 2. The magnetic memory according to claim 1, wherein at least one of the plurality of magnetic layers constituting the storage layer is made of a ferrimagnetic material.

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