JP2004253739A - Magnetic storage element, its recording method and magnetic storage device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic storage element in which a record is stably maintained and further recording is performed with a small recording current even when high recording density is contrived, and to provide its recording method, and a magnetic storage device provided with the magnetic storage element. <P>SOLUTION: A recording layer is constituted by laminating at least three magnetic layers 11A, 12 and 11B. The outer peripheral dimension of an element 10 in a in-plane direction is four times or less the total thickness of the magnetic layers 11A, 12 and 11B, further three times or more the single layer thickness of each of the magnetic layers 11A, 12 and 11B. The magnetic layer 12 having the largest specific resistance is arranged being sandwiched between the other magnetic layers 11A and 11B. In this way a magnetic storage element 10 is constituted. Further, the magnetic storage element 10 is heated to rise the temperature of the magnetic layer 12 having the largest specific resistance up to its Curie point or above. In this state, a magnetic field is applied in a film thickness direction. In this state where the magnetic field is applied, heating is stopped to cool down to the Curie point or below, to record a magnetization condition. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a magnetic storage element suitable for use in a nonvolatile memory, a recording method thereof, and a magnetic storage device configured using the magnetic storage element.
[0002]
[Prior art]
In information devices such as computers, high-speed and high-density DRAMs are widely used as random access memories.
However, since a DRAM is a volatile memory that loses information when the power is turned off, a nonvolatile memory that does not erase information is desired.
[0003]
As a nonvolatile memory, a magnetic random access memory (MRAM) using a magnetic storage element that records information based on a magnetization state of a magnetic material has been developed (for example, see Non-Patent Document 1).
[0004]
In the future, it is necessary to increase the density of the MRAM in order to increase the storage capacity and reduce the size of the device. Accordingly, it is required to further reduce the size of the magnetic storage elements constituting the memory cell.
[0005]
In a magnetic storage element used in an MRAM, magnetization is stabilized using a demagnetizing field generated by making the shape of a magnetic substance rectangular or elliptical, so that the coercive force increases as the element size decreases. In order to suppress this, it is necessary to reduce the film thickness.
[0006]
However, a decrease in the volume and coercive force of the element degrades the thermal stability of the magnetic storage element. That is, since the volume of the element is reduced due to the reduction in the element size, if the coercive force is reduced by reducing the film thickness as described above, the thermal stability of the magnetic storage element is deteriorated. Become.
[0007]
Therefore, a method using a perpendicular magnetization film for a magnetic storage element (for example, see Patent Document 1) has been proposed.
By using a perpendicular magnetization film, the coercive force is reduced to such an extent that the magnetization can be inverted, and the recorded magnetization is stably held.
[0008]
[Non-patent document 1]
Nikkei Electronics 2001.12 (pages 164-171)
[Patent Document 1]
JP 2001-291911 A (FIGS. 1 and 6)
[0009]
[Problems to be solved by the invention]
However, when the perpendicular magnetization film is used as described above, the perpendicular magnetic anisotropy equal to or more than the demagnetizing field is required in order to stabilize the recorded magnetization in the vertical direction, and the magnetization in the in-plane direction (horizontal direction) is required. In general, a larger coercive force is required as compared with the case of using.
[0010]
In addition, in order to facilitate the detection of magnetization, a certain amount of magnetization is required for the element, which makes it difficult to reduce the coercive force.
[0011]
Furthermore, when the element is miniaturized, the reversal of magnetization becomes a simultaneous magnetization reversal without magnetic domain movement, so that the above-described configuration of a perpendicular magnetization film having a large perpendicular magnetic anisotropy and a small coercive force can be realized. Becomes difficult.
[0012]
In order to solve the above-described problem, the present invention provides a magnetic storage element that can stably hold recording and can perform recording with a low recording current even when a high recording density is achieved, and a recording method for the magnetic storage element. A method and a magnetic storage device provided with the magnetic storage element are provided.
[0013]
[Means for Solving the Problems]
A magnetic storage element according to the present invention is a magnetic storage element that holds information by magnetization of a magnetic material, and has a storage layer that holds information in which at least three magnetic layers are stacked, and a magnetic layer in an in-plane direction of the element. The outer dimension is four times or less the total thickness of the magnetic material layers, and three times or more the thickness of a single magnetic layer, and the magnetic material layer having the largest specific resistance among the magnetic material layers is It is arranged so as to be sandwiched between other magnetic layers.
[0014]
The recording method for a magnetic storage element according to the present invention is characterized in that a storage layer for holding information by magnetization of a magnetic substance is formed by laminating at least three magnetic substance layers, and the outer peripheral dimension in the in-plane direction of the element is the total of the magnetic substance layers. The thickness of the magnetic material layer is 4 times or less, and the thickness of each magnetic material layer is 3 times or more, and the magnetic material layer having the largest specific resistance among the magnetic material layers is sandwiched between other magnetic material layers. This magnetic storage element is heated with respect to the magnetic storage element arranged in such a manner that the temperature of the magnetic layer having the highest specific resistance is increased to a temperature equal to or higher than the Curie point of the magnetic layer. On the other hand, a magnetic field in the film thickness direction is applied, heating is stopped in a state where the magnetic field is applied, and the magnetic field is cooled to the Curie point or lower, and the magnetization state is recorded on the magnetic memory element.
[0015]
The magnetic storage device according to the present invention comprises a storage layer for holding information by magnetization of a magnetic body and at least three magnetic layers laminated, and the outer peripheral dimension in the in-plane direction of the element is equal to the total thickness of the magnetic layer. The magnetic layer having the largest specific resistance among the magnetic layers is at least four times the thickness of a single layer of each magnetic layer, and is disposed between the other magnetic layers. Magnetic storage element, and a first wiring and a second wiring that intersect with each other, and the magnetic storage element is arranged at each intersection where the first wiring and the second wiring intersect with each other It is.
[0016]
According to the configuration of the magnetic storage element of the present invention described above, the storage layer for storing information is formed by laminating at least three magnetic layers, and the outer peripheral dimension in the in-plane direction of the element is the total thickness of the magnetic layers. The magnetic layer having the largest specific resistance among the magnetic layers is four times or less of the thickness of each magnetic layer, and is three times or more the thickness of a single layer of each magnetic layer. Therefore, when the magnetic memory element is heated, the temperature of the magnetic layer having the largest specific resistance rises more than that of the other magnetic layers. When the temperature of the magnetic layer having the highest specific resistance is raised to a temperature equal to or higher than its Curie point, the magnetic layer having the highest specific resistance is demagnetized, and the other magnetic layers sandwiching the magnetic layer are separated by two. It can be divided into two magnetic bodies. As a result, the coercive force of the storage layer decreases as the coercive force in the thickness direction of each of the divided magnetic layers, and the direction of magnetization of the magnetic layer is changed by a magnetic field, and information is stored in the storage layer. Recording can be performed.
On the other hand, in the non-heated state, three or more magnetic layers become an integral magnetic material, and the coercive force in the thickness direction of the storage layer increases, so that the recorded information can be stably held. .
Further, the outer peripheral dimension in the in-plane direction of the element is not more than four times the total thickness of the magnetic material layers and is not less than three times the thickness of a single layer of each magnetic material layer. And the coercive force in the thickness direction of the storage layer can be increased when the magnetic layer is separated, and the coercive force in the thickness direction of each magnetic layer when divided by heating is reduced to increase the in-plane magnetostatic property. A dynamic bond can be formed.
[0017]
According to the recording method of the magnetic memory element of the present invention described above, the magnetic memory element of the present invention is heated to heat the magnetic memory element, and the magnetic layer having the highest specific resistance is formed on the magnetic layer. The temperature is raised to above the Curie point, a magnetic field in the thickness direction is applied to the magnetic storage element in that state, and the magnetic layer having the largest specific resistance is raised to a temperature above the Curie point to demagnetize it. The other magnetic layer sandwiching the magnetic layer having a large specific resistance can be divided into two magnetic bodies to reduce the coercive force, and by applying a magnetic field in the film thickness direction with the coercive force reduced. In addition, the magnetization state of the storage layer can be changed.
Then, by stopping the heating in a state where the magnetic field is applied and cooling the magnetic layer below the Curie point, when the magnetization of the magnetic layer having the largest specific resistance is restored by the cooling, the storage layer is cooled according to the direction of the magnetic field. The magnetization of the three or more magnetic layers is aligned, and the magnetization state is recorded.
In the state where the magnetization is uniform as a single magnetic body, the coercive force is large, so that the magnetization state once recorded can be stably held.
[0018]
According to the configuration of the magnetic storage device of the present invention described above, the magnetic storage device of the present invention includes the first wiring and the second wiring that cross each other, and the first wiring and the second wiring By arranging the magnetic storage elements at the intersections where と intersects, it is possible to perform recording on the magnetic storage elements by the above-described recording method.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention relates to a magnetic storage element for holding information by magnetization of a magnetic body, wherein the storage layer for holding information is formed by laminating at least three magnetic layers, and the outer peripheral dimension in the in-plane direction of the element is magnetic. The total thickness of the magnetic layers is not more than four times the total thickness of the magnetic layers, and is not less than three times the thickness of a single layer of each magnetic layer. The magnetic storage element is sandwiched between layers.
[0020]
Further, according to the present invention, in the above magnetic storage element, each magnetic layer forming the storage layer is magnetized in a thickness direction at room temperature.
[0021]
Further, according to the present invention, in the above magnetic storage element, the magnetic layer having the largest specific resistance has a specific resistance twice or more that of the other magnetic layers.
[0022]
According to the present invention, a storage layer for holding information by magnetization of a magnetic material is formed by laminating at least three magnetic material layers, and an outer dimension in an in-plane direction of the element is four times or less of a total thickness of the magnetic material layer. And the magnetic layer having the largest specific resistance among the magnetic layers, which is at least three times the thickness of a single layer of each magnetic layer, is disposed between the other magnetic layers. The magnetic storage element is heated with respect to the element, and the temperature of the magnetic layer having the highest specific resistance is raised to a temperature equal to or higher than the Curie point of the magnetic layer. Is applied, the heating is stopped in a state where the magnetic field is applied, the temperature is cooled below the Curie point, and the magnetization state is recorded on the magnetic storage element.
[0023]
According to the present invention, a storage layer for holding information by magnetization of a magnetic material is formed by laminating at least three magnetic material layers, and an outer dimension in an in-plane direction of the element is four times or less of a total thickness of the magnetic material layer. And the magnetic layer having the largest specific resistance among the magnetic layers, which is at least three times the thickness of a single layer of each magnetic layer, is disposed between the other magnetic layers. A magnetic storage device including an element, a first wiring and a second wiring that intersect each other, and a magnetic storage element is arranged at an intersection where the first wiring and the second wiring intersect. .
[0024]
Further, according to the present invention, in the above magnetic storage device, a current can flow from the first wiring and the second wiring to the magnetic storage element.
[0025]
FIG. 1 shows a schematic configuration diagram of a magnetic storage element as one embodiment of the present invention.
The magnetic storage element 10 serves as a storage layer in which information is recorded in accordance with the direction of magnetization. The magnetic storage element 10 has three layers in which a thin magnetic layer 12 is sandwiched between two thick magnetic layers 11A and 11B. It has a laminated structure of magnetic layers.
[0026]
The material of each of the magnetic layers 11A, 12 and 11B may be a ferromagnetic material containing Fe, Co, or Ni as a main component, a ferrimagnetic material made of an alloy of a rare earth metal and a transition metal, or CrO. ₂ And Fe ₂ O ₃ And the like may be mainly composed of an oxide magnetic material such as
[0027]
Further, these three magnetic layers 11A, 12 and 11B are configured to be perpendicular magnetization films. That is, the film thickness and the dimension in the film surface direction are defined so as to form a perpendicular magnetization film.
By defining the film thickness and the dimension in the film surface direction in this way, it is possible to magnetize in the vertical direction by the effect of shape anisotropy.
[0028]
Further, in magnetic storage element 10 of the present embodiment, thin magnetic layer 12 sandwiched between thick magnetic layers 11A and 11B has a higher specific resistance than thick magnetic layers 11A and 11B. Configuration.
[0029]
More preferably, the specific resistance of the thin magnetic layer 12 is at least twice the specific resistance of the thick magnetic layers 11A and 11B.
[0030]
As a result, when the magnetic memory element 10 is heated, the temperature rise due to the heating of the thin magnetic layer 12 having a higher specific resistance is larger than that of the thin magnetic layer 12, and the temperature of the thin magnetic layer 12 becomes higher than the Curie point first. The magnetization disappears, that is, it becomes non-magnetic.
When the thin magnetic layer 12 becomes non-magnetic, the magnetic coupling between the upper and lower thick magnetic layers 11A and 11B formed through the thin magnetic layer 12 is broken.
Thereby, the magnetic material is divided into the individual magnetic material layers 11A and 11B, and the thickness is reduced, and the coercive force can be reduced.
[0031]
Further, in the magnetic storage element 10 of the present embodiment, in particular, as described above, the thickness of each of the magnetic layers 11A, 12, and 11B and the dimension in the film surface direction are different from those of the magnetic layers 11A, 12, and 11B. Not only becomes a perpendicular magnetization film, but also can realize both recording by reversal of magnetization and stable retention of the recorded magnetization.
That is, as shown in FIG. 1, the thickness of the upper and lower thick magnetic layers 11A and 11B is d1, the thickness of the thin magnetic layer between them is d2 (<d1), and the total thickness of the magnetic layers 11A, 12 and 11B. When the thickness is D (= d1 + d2 + d1), the outer circumferential dimension of the magnetic storage element 10 in the in-plane direction is four times or less the total thickness D of the magnetic layer, and the upper and lower thick magnetic layers (of the specific resistance). The thickness is set to be three times or more the thickness d1 of the small magnetic layers 11A and 11B.
[0032]
With this definition, the dimension (length, width, etc.) of the magnetic storage element 10 in the in-plane direction is relatively small when viewed from the total thickness D of the magnetic layer, and the thickness d1 of the upper and lower magnetic layers is small. From the viewpoint, it is relatively large.
Thus, when the three magnetic layers 11A, 12 and 11B in which no current flows through the magnetic storage element 10 are made of an integral magnetic material, the thickness D is smaller than the dimension in the in-plane direction. Therefore, the coercive force in the film thickness direction (vertical direction) increases. When the coercive force in the thickness direction is large, the magnetization recorded by perpendicular magnetization can be stably held only by the magnetic anisotropy due to the shape.
On the other hand, when a current flows through the magnetic memory element 10 and the magnetic body is divided into two thick magnetic layers 11A and 11B, the film thickness d1 is relatively small as compared with the dimension in the in-plane direction. The coercive force in the thickness direction (vertical direction) is reduced. Since the coercive force in the film thickness direction is small, the magnetization of each magnetic layer is easily directed in the in-plane direction during recording, that is, the magnetostatic coupling in the in-plane direction is easily formed, and the magnetization is reversed with a small magnetic field. It becomes possible to do.
[0033]
Subsequently, a method for recording information in the magnetic storage element 10 according to the present embodiment having the above-described configuration will be described.
[0034]
Here, as shown in FIG. 2A, when the magnetization of each of the magnetic layers 11A, 12, and 11B is downward at room temperature, the magnetization of each of the magnetic layers 11A, 12, and 11B is inverted upward. The procedure for recording the information is described below.
First, a current (upward or downward) is caused to flow in the thickness direction of the magnetic storage element 10. Since the magnetic storage element 10 is heated by this current, the temperature of the thin magnetic layer 12 having a particularly large specific resistance greatly increases.
[0035]
Then, when the magnetization of the thin magnetic layer 12 exceeds the Curie point and disappears, the thin magnetic layer 12 becomes non-magnetic and the magnetic coupling between the upper and lower thick magnetic layers 11A and 11B is cut off. Thereby, as shown in FIG. 2B, magnetostatic coupling occurs in the thick magnetic layers 11A and 11B, and the magnetizations are arranged in the in-plane direction and antiparallel to each other.
In such a state, the coercive force in the film thickness direction becomes small, so that the direction of magnetization can be reversed by applying an upward magnetic field H (see FIG. 2C).
[0036]
Next, when an upward magnetic field H shown in FIG. 2C is applied, the current is stopped and the magnetic memory element 10 is cooled in a state where the magnetic field H is applied. The magnetic coupling of the body layers 11A and 11B is formed, and an upward magnetization in the direction of the magnetic field H is generated in the three magnetic layers 11A, 12 and 11B.
Thereafter, the magnetic field H is removed, and the recording is completed.
[0037]
On the other hand, when reversing the magnetization of the magnetic storage element 10 from upward to downward, as opposed to FIGS. 2A to 2C, the direction of the magnetic field may be downward.
[0038]
In this manner, upward or downward magnetization information is recorded in the magnetic storage element 10 in accordance with the information to be recorded.
[0039]
According to the configuration of the magnetic storage element 10 of the present embodiment described above, by defining the film thickness and the dimension in the in-plane direction as described above, the magnetic storage element 10 is formed as a perpendicular magnetization film. When it is not, the three magnetic layers 11A, 12 and 11B are integrated magnetic materials, and the total thickness D of the magnetic memory element 10 becomes large when viewed from the dimension in the in-plane direction. Has a large coercive force. Thereby, information recorded by perpendicular magnetization can be stably held.
[0040]
Also, the thin magnetic layer 12 sandwiched between the three magnetic layers 11A, 12 and 11B has a higher specific resistance than the upper and lower magnetic layers 11A and 11B, so that the magnetic memory element 10 When an electric current is applied and heated, the temperature of the magnetic layer 12 having a large specific resistance greatly increases to a temperature exceeding the Curie point, and the magnetic layer 12 becomes non-magnetic. At this time, in-plane magnetostatic coupling occurs between the upper and lower magnetic layers 11A and 11B.
Since the thickness d1 of the magnetic layers 11A and 11B is small when viewed from the dimension in the in-plane direction, the coercive force in the film thickness direction is small, and the magnetostatic coupling in the in-plane direction is easily generated. Is easily inverted. This enables recording with a small magnetic field.
[0041]
Therefore, by using the magnetic storage element 10 of the present embodiment, it is possible to stabilize the magnetization even when the magnetic storage elements 10 are integrated at a high density and to easily perform recording with a small magnetic field (magnetic field). Thus, a magnetic storage device capable of stably and accurately recording information can be configured.
[0042]
Then, a magnetic storage device such as an MRAM is configured by arranging the magnetic storage element 10 of the present embodiment at the intersection of a plurality of first wirings and second wirings which are arranged orthogonally in a matrix. be able to.
[0043]
Next, as one embodiment of the magnetic storage device of the present invention, FIG. 3 shows a schematic configuration diagram (perspective view) of a magnetic storage device configured using the magnetic storage element 10 of the above embodiment. FIG. 4 is a plan view of the magnetic storage device shown in FIG. 3 illustrates two vertical and two horizontal magnetic storage elements 10, and FIG. 4 illustrates four vertical and four horizontal magnetic storage elements.
[0044]
As shown in FIGS. 3 and 4, the magnetic storage device 40 has an intersection of a large number of first wirings (for example, bit lines) 21 and second wirings (for example, word lines) 22 arranged in a matrix at right angles. The magnetic storage element 10 has a rectangular planar shape and has the structure shown in FIG.
As shown in FIG. 1, each magnetic storage element 10 includes two thick magnetic layers 11A and 11B with a thin magnetic layer 12 interposed therebetween.
[0045]
When the magnetic storage device 40 is configured as described above, recording is performed on the magnetic storage element 10 as follows, for example.
[0046]
First, one of the first wirings 21 and the second wirings 22 corresponding to the magnetic memory element 10 for performing recording is selected from a large number of the first wirings 21 and the second wirings 22, and the first wirings 21 and 22 are selected. An electric current is applied to the magnetic storage element 10 for recording by applying an electric current to the second wiring 22 and an electric current in the film thickness direction (vertical direction in the figure).
As a result, the temperature of the thin magnetic layer 12 rises and becomes demagnetized beyond the Curie point, so that the magnetic information is stored in the magnetic memory element 10 (“0” or “1”). The direction of the magnetic field applied to the storage element 10 is set, and the magnetic field is applied.
[0047]
At this time, it is set so that a current is applied to raise the temperature to a temperature exceeding the Curie temperature of the thin magnetic layer 12, and then a magnetic field is applied to perform recording.
In other words, the Curie temperature of the thin magnetic layer 12 may be set to be lower than the temperature at the time of recording.
[0048]
Then, while the magnetic field applied to the magnetic storage element 10 is applied, the current flowing through the first wiring 21 and the second wiring 22 is stopped, and the current flowing through the magnetic storage element 10 is eliminated. Allow 10 to cool.
As a result, the magnetization of the thin magnetic layer 12 is restored, and the magnetization directions of the three magnetic layers 11A, 12 and 11B become the film thickness direction. That is, the entire magnetic storage element 10 becomes perpendicular magnetization, and the direction of the magnetization becomes the direction of the magnetic field, that is, the direction of the magnetization corresponding to the content of information. Then, by removing the magnetic field, the recording of the magnetization information in the magnetic storage element 10 ends.
[0049]
These steps can be repeated for the magnetic storage element 10 that needs to record (rewrite) information, and information can be recorded on all the magnetic storage elements 10 that need to record information.
[0050]
By performing the recording as described above, in the selected magnetic storage element 10, a current flows from the corresponding first wiring 21 and the second wiring 22 to the magnetic storage element 10, and the thin magnetic layer 12 is not moved. The magnetic storage element 10 is magnetized to reduce the coercive force in the thickness direction of the magnetic storage element 10, and a magnetic field whose direction is set according to the content of information to be recorded is applied. Be recorded.
On the other hand, in the non-selected magnetic storage element 10, no current flows from the corresponding first wiring 21 and second wiring 22 to the magnetic storage element 10. Even if one of the wirings 21 or 22 is common to the selected magnetic storage element 10, no current flows through the magnetic storage element 10 unless the other wiring is common. For this reason, the three magnetic layers 11A, 12 and 11B remain an integral magnetic material, the coercive force in the thickness direction is large, and the recorded magnetization state can be stably held.
[0051]
According to the configuration of the magnetic storage device 40 of the present embodiment described above, at the time of recording, the coercive force in the film thickness direction of the magnetic storage element 10 can be reduced, and recording can be easily performed. The magnetization state can be stably maintained until recording is performed again.
And, as the magnetic storage element is miniaturized in order to increase the recording capacity, the coercive force increases and it becomes difficult to perform recording, and it tends to become difficult to stably maintain perpendicular magnetization. The magnetic storage device 40 of the present embodiment is suitable for increasing the storage capacity.
[0052]
Here, the magnetic storage element 10 of the embodiment shown in FIG. 1 was actually manufactured, and the magnetic characteristics were examined.
The upper and lower thick magnetic layers 11A and 11B are formed of a 70-nm thick Ni film, and the thin magnetic layer 12 is formed of a 10-nm thick CoRu-SiO ₂ The magnetic storage element 10 was formed by a film.
The specific resistance of the Ni film is 10 μΩcm, CoRu-SiO ₂ The specific resistance of the film is 800 μΩcm.
In manufacturing the magnetic memory element 10, after these three magnetic layers 11A, 12 and 11B are formed, FIB (focused ion beam) processing is performed so that the dimension in the in-plane direction becomes 100 nm square. Processed to.
[0053]
The perpendicular magnetization of the magnetic storage element 10 was measured by the polar Kerr effect. The results are shown in FIGS. 5A and 5B. FIG. 5A shows the magnetization M when no current flows through the element, and FIG. 5B shows the magnetization M when a current of 5 mA flows per element.
[0054]
Comparing FIG. 5A and FIG. 5B, it can be seen that the coercive force is reduced by flowing a current. Therefore, it is understood that writing can be easily performed by passing a current through the element.
[0055]
By the way, the magnetic storage element 10 according to the embodiment shown in FIG. 1 has a rectangular parallelepiped shape (quadratic prism shape).
In the present invention, the shape of the magnetic storage element is not limited to a rectangular parallelepiped (quadratic prism), but may be a cylinder or an elliptical column, or the dimensions of the top surface and the bottom surface may be slightly different (for example, a trapezoidal cross section). However, it suffices if the above condition is satisfied on average.
[0056]
For example, FIGS. 6 and 7 show schematic configuration diagrams of a magnetic storage device 50 in which an elliptic columnar magnetic storage element 20 is formed and a first wiring 21 and a second wiring 22 are similarly arranged. 6, two vertical and two horizontal magnetic storage elements are illustrated in FIG. 6, and four vertical and four horizontal magnetic storage elements 20 are illustrated in FIG.
[0057]
In the magnetic storage device 50, similarly to the magnetic storage device 40 described above, while recording can be easily performed, the recorded magnetization state can be stably held. .
The magnetic storage device 50 is also suitable for increasing the storage capacity, similarly to the magnetic storage device 40 described above.
[0058]
Here, the relationship between the size of the magnetic layer of the magnetic memory element and the coercive force was calculated by micromagnetic.
Specifically, when the shape of the magnetic storage element is a rectangular parallelepiped and when the magnetic storage element is an elliptical column, the thickness z and the in-plane dimensions (vertical and horizontal or long axis / short axis) x and y of the magnetic body are determined. The change of the coercive force in the film thickness direction when changing was obtained.
The magnetic storage element 10 was constituted by the three magnetic layers 11A, 12 and 11B shown in FIG. 1, and the thickness of the thin magnetic layer 12 was 10 nm.
Then, three cases where dimensions in the plane direction (vertical and horizontal or major axis / minor axis) x and y are x = 50 nm, y = 50 nm, x = 50 nm, y = 70 nm, x = 70 nm, and y = 70 nm, respectively. The coercive force in the film thickness direction was calculated by changing the thickness z of the magnetic material. That is, when the three magnetic layers 11A, 12 and 11B are an integral magnetic body, the thickness z of the magnetic body becomes the total thickness D of the magnetic memory element 10, and the thin magnetic layer 12 becomes non-magnetic. When it is divided into upper and lower magnetic layers 11A and 11B, the thickness z of the magnetic substance becomes the thickness d1 of the upper and lower magnetic layers 11A and 11B.
FIG. 8 shows the relationship between the film thickness and the coercive force when the magnetic storage element is a rectangular parallelepiped and is formed as an integral magnetic body.
FIG. 9 shows the relationship between the thickness of each magnetic layer and the coercive force when the magnetic memory element is a rectangular parallelepiped and the magnetic body is divided into upper and lower magnetic layers.
FIG. 10 shows the relationship between the film thickness and the coercive force when the magnetic storage element is formed in an elliptical column and is formed as an integral magnetic body.
FIG. 11 shows the relationship between the film thickness of each magnetic layer and the coercive force when the magnetic memory element has an elliptical column shape and the magnetic body is divided into upper and lower magnetic layers.
[0059]
8 and 10, the coercive force increases as the thickness z of the magnetic body increases, and the thickness z increases as compared with the in-plane dimensions x and y. It can be seen that the coercive force becomes larger when this happens.
When the magnetic material is divided into upper and lower magnetic material layers, the coercive force also increases as the thickness z of the magnetic material increases in this case, as shown in FIGS. In comparison, it can be seen that the coercive force increases as the thickness z increases. Further, when the magnetic layer is divided into upper and lower magnetic layers, the thickness z at which the coercive force starts to increase is slightly smaller than that in the case of a single magnetic body due to the magnetic influence between the layers.
[0060]
It is desirable that the coercive force be large when the magnetic storage element 10 is an integral magnetic body, and small when the magnetic storage element 10 is divided into upper and lower magnetic layers 11A and 11B. The total thickness D of the storage element 10 is relatively large with respect to the in-plane directions x and y, and the thickness d1 of the upper and lower magnetic layers 11A and 11B is compared with the in-plane directions x and y. It is necessary to have a very small configuration.
[0061]
In a magnetic storage device in which a large number of magnetic storage elements are arranged, when recording is performed on each magnetic storage element, there is a magnetic field received from surrounding magnetic storage elements. Unless a magnetic field is applied, desired recording cannot be performed.
Therefore, in order to reduce the magnetic field received from the surrounding magnetic storage elements, it is conceivable that the content of the information recorded in each magnetic storage element is not biased to one of “0” and “1”.
[0062]
For example, it is assumed that 150 “0” and 50 “1” are to be recorded in 200 magnetic storage elements out of 10,000 magnetic storage elements, respectively.
If 200 pieces to be recorded are consolidated (for example, grouped into 10 rows × 20 columns), “0” is concentrated, and in a portion where many “0” are gathered, a magnetic field received from a surrounding magnetic storage element is generated. As a result, the desired recording becomes difficult.
Therefore, if the recording is distributed and controlled by a computer program or the like so that 200 recordings are well distributed among 10,000 recordings, desired recording can be easily performed.
[0063]
In the above-described embodiment, the three-layer structure of the thin magnetic layer 12 having a large specific resistance is sandwiched between the upper and lower magnetic layers 11A and 11B. It is also possible to form a magnetic memory element with four or more magnetic layers by stacking a plurality of magnetic layers with a magnetic layer having high resistance.
Further, a non-magnetic layer (for example, an electrode layer) may be provided at a portion connecting the upper and lower magnetic layers and the outside of the magnetic storage element.
[0064]
Further, the magnetic layer having a large specific resistance sandwiched therebetween is sufficiently thinner than the upper and lower magnetic layers in the samples used in the measurements of FIGS. The thickness may be equal to or less than the thickness.
The merits of making the magnetic layer with high specific resistance sufficiently thin are that the heat capacity becomes small and the temperature rises easily, and when it becomes non-magnetic, magnetostatic coupling to the upper and lower magnetic layers becomes easier. And the like.
[0065]
Further, the magnetic layer having a large specific resistance is preferably located at the magnetic center of the magnetic memory element and substantially at the center of the amount of magnetization. However, the present invention includes other configurations.
[0066]
As a method of heating the magnetic storage element, a method other than the method of directly supplying a current to the magnetic storage element from the above-described wiring is also possible. Is also conceivable.
In a configuration in which a current flows directly from the wiring to the magnetic storage element, in the magnetic storage device 40 shown in FIG. 3, the current only needs to flow from the first wiring 21 and the second wiring 22. This is advantageous in that both selection and heating of the storage element can be performed.
[0067]
Further, in the present invention, the configuration for detecting the magnetization state of the magnetic storage element is not particularly limited. For example, a magnetic tunnel junction element (TMR element), a giant magnetoresistance effect element (GMR element), a Hall element, or the like can be used.
[0068]
The present invention is not limited to the above-described embodiment, and may take various other configurations without departing from the gist of the present invention.
[0069]
【The invention's effect】
According to the present invention described above, when the magnetic memory element is not heated, the magnetic layer acts as an integral magnetic body and the coercive force in the film thickness direction increases, so that the recorded information can be stabilized. Can be held.
Further, by heating the magnetic storage element, the magnetic layer is divided and the coercive force in the film thickness direction decreases, so that recording can be performed with a small magnetic field.
Therefore, according to the present invention, it is possible to configure a magnetic storage device capable of stably recording information.
[0070]
In particular, since the relationship between the total thickness of the magnetic storage element and the thickness of the separated magnetic material layer and the outer peripheral dimension in the in-plane direction is defined within a predetermined range, the magnetic material becomes an integrated magnetic material. In this case, the coercive force in the film thickness direction can be increased when the film is separated, and the coercive force in the film thickness direction when the film is divided can be reduced.
As a result, even if the magnetic storage element is miniaturized, and even if the magnetic storage element is densely integrated and the influence of a magnetic field from an adjacent element increases, information can be easily recorded and the recorded information can be easily recorded. Can be held stably.
In a magnetic storage device, as the size of the magnetic storage element is reduced in order to increase the storage capacity, and as the density of the magnetic storage element is increased, recording of information and retention of the recorded information tend to be more difficult. The present invention is effective for increasing the storage capacity of a magnetic recording device.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of an embodiment of a magnetic storage element of the present invention.
2A to 2C are diagrams for explaining a recording operation of the magnetic storage element of FIG. 1;
FIG. 3 is a schematic configuration diagram (perspective view) of a magnetic storage device using the magnetic storage element of FIG. 1;
FIG. 4 is a plan view of the magnetic storage device of FIG. 3;
5 is a diagram showing a change in magnetic characteristics depending on the presence or absence of a current flowing through the magnetic storage element of FIG. A is a magnetization curve when no current is flowing. B is a magnetization curve in a state where a current is passed.
FIG. 6 is a schematic configuration diagram (perspective view) of another embodiment of the magnetic storage device of the present invention.
FIG. 7 is a plan view of the magnetic storage device of FIG. 6;
FIG. 8 is a diagram illustrating the relationship between the film thickness and the coercive force when the magnetic storage element is a rectangular parallelepiped and formed as an integral magnetic body.
FIG. 9 is a view showing the relationship between the thickness of each magnetic layer and the coercive force when the magnetic storage element is a rectangular parallelepiped and the magnetic body is divided into upper and lower magnetic layers.
FIG. 10 is a diagram showing the relationship between the film thickness and the coercive force when the magnetic storage element is formed into an elliptical column and formed as an integral magnetic body.
FIG. 11 is a diagram showing the relationship between the film thickness of each magnetic layer and the coercive force when the magnetic memory element has an elliptical column shape and the magnetic body is divided into upper and lower magnetic layers.
[Explanation of symbols]
10, 20 magnetic storage element, 11A, 11B, 12 magnetic layer, 21 first wiring, 22 second wiring, 40, 50 magnetic storage device

Claims (6)

A magnetic storage element that holds information by magnetization of a magnetic material,
The storage layer for holding the information is formed by stacking at least three magnetic layers,
An outer circumferential dimension of the element in the in-plane direction is four times or less the total thickness of the magnetic layers, and three times or more the thickness of a single layer of each magnetic layer;
A magnetic memory element, wherein a magnetic layer having the highest specific resistance among the magnetic layers is disposed between other magnetic layers. 2. The magnetic storage element according to claim 1, wherein each magnetic layer constituting the storage layer is magnetized in a thickness direction at room temperature. 2. The magnetic memory element according to claim 1, wherein the magnitude of the specific resistance of the magnetic layer having the largest specific resistance is at least twice that of the other magnetic layers. A storage layer for holding information by magnetization of a magnetic material is formed by stacking at least three magnetic material layers,
An outer circumferential dimension of the element in the in-plane direction is four times or less the total thickness of the magnetic layers, and three times or more the thickness of a single layer of each magnetic layer;
The magnetic layer having the largest specific resistance among the magnetic layers is a magnetic storage element sandwiched between other magnetic layers.
The magnetic storage element is heated to raise the temperature of the magnetic layer having the highest specific resistance to a temperature equal to or higher than the Curie point of the magnetic layer, and in that state, a magnetic field in the thickness direction is applied to the magnetic storage element. ,
A recording method for a magnetic storage element, wherein the heating is stopped in a state where the magnetic field is applied, the temperature is cooled below the Curie point, and the magnetization state is recorded in the magnetic storage element. A storage layer for holding information by magnetization of a magnetic material is formed by stacking at least three magnetic material layers,
An outer circumferential dimension of the element in the in-plane direction is four times or less the total thickness of the magnetic layers, and three times or more the thickness of a single layer of each magnetic layer;
A magnetic storage element in which the magnetic layer having the highest specific resistance among the magnetic layers is disposed between other magnetic layers,
A first wiring and a second wiring that cross each other,
A magnetic storage device, wherein the magnetic storage elements are arranged at intersections where the first wiring and the second wiring intersect, respectively. 6. The magnetic storage device according to claim 5, wherein a current is allowed to flow through the magnetic storage element from the first wiring and the second wiring.

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