JP6743641B2 - Magnetic field modulation mechanism, magnetic field modulation element, analog memory element, and high frequency filter - Google Patents

Description

The present invention relates to a magnetic field modulation mechanism, a magnetic field modulation element, an analog memory element, and a high frequency filter.

As a next-generation non-volatile memory that replaces flash memory, which has reached its limit of miniaturization, resistance change memory that stores data using resistance change elements, such as MRAM (Magnetroresistive Random Access Memory) and ReRAM (Resistancne Random Access Memory), PCRAM (Phase Change Random Access Memory), etc. are receiving attention.

As methods for increasing the density (capacity) of the memory, there are various methods such as a method of making the recording bit per one element of the memory multi-valued, in addition to a method of making the element itself of the memory small. Various multi-valued methods have been proposed (for example, Patent Documents 1 to 3).

One of the MRAMs is called a domain wall drive type or a domain wall moving type (for example, Patent Document 4). In the domain wall drive type MRAM, an electric current is caused to flow in the in-plane direction of a domain wall drive layer (which may also serve as a magnetization free layer), and the domain wall is moved by the spin transfer effect of spin-polarized electrons to magnetize the ferromagnetic film. The data is written by reversing in the direction corresponding to the direction of the write current.
Patent Document 4 describes a method of multi-value recording or analog recording of a domain wall drive type MRAM.
In MRAM, different data writing methods have been proposed. In addition to domain wall drive type MRAM, magnetic field writing type, yoke magnetic field writing type, STT (Spin Transfer Torque) type, SOT (Spin Orbit Torque) type MRAM, etc. are known. Has been.

JP, 2005-088669, A International Publication No. 2009/072213 JP, 2016-004924, A International Publication No. 2009/101827 JP-A-3-273540

However, in the conventional domain wall drive type MRAM, since it is necessary to pass a current in the in-plane direction of the domain wall drive layer at the time of reading, there is a possibility that the domain wall of the domain wall driving layer may be moved by the current passed at the time of reading. When the domain wall moves to the outside of the portion where the domain wall drive layer and the magnetoresistive effect element overlap, the signal finally becomes a digital signal of 0 or 1 in the domain wall drive type MRAM, and should be used as an analog memory. Was difficult. On the contrary, if the domain wall movement is not completed outside the portion where the domain wall drive layer and the magnetoresistive effect element overlap in a plan view, the domain wall will move during reading and the signal at the time of erroneous writing or initial reading will change. There is a problem such as doing. Therefore, for the conventional domain wall drive type MRAM, it is desired to develop a stable reading means.

On the other hand, there is also a demand for the development of a new type of MRAM capable of multi-level recording and analog recording, which has never been achieved.

A conventional MRAM is an element that assumes a binary digital signal in which the directions of magnetization of two ferromagnetic layers in a magnetoresistive effect element are parallel or antiparallel, and the conventional MRAM is multivalued. It is not possible to handle simple signals or analog signals. However, if the relative angles of magnetization of the two ferromagnetic layers can be fixed to a plurality of or arbitrary angles other than 0° (parallel) or 180° (antiparallel), multilevel recording or analog recording is possible. MRAM can be realized. Here, as a method of fixing the relative angle of magnetization of the two ferromagnetic layers to such an angle, applying an external magnetic field can be considered. In order to apply the external magnetic field, for example, a method of disposing a permanent magnet in the vicinity of the magnetoresistive effect element, a method of utilizing a magnetic field induced by an electric current, or the like can be considered. However, the magnitude of the magnetic field applied to the magnetoresistive effect element cannot be changed by simply disposing the permanent magnet near the magnetoresistive effect element. Therefore, the resistance of the magnetoresistive effect element cannot be changed and cannot be used as an analog memory. Although it is possible to change the magnitude of the external magnetic field applied to the magnetoresistive effect element by a method of mechanically moving a magnet like a hard disk drive, it is not realistic to make an analog memory by using this method. Absent. Further, in the method of utilizing the magnetic field induced by the current, it is necessary to keep the current flowing in order to apply the magnetic field for fixing the relative angle of the magnetizations of the two ferromagnetic layers as the non-volatile data, which results in energy consumption. It is disadvantageous from a viewpoint, and this is not realistic either.

Ideally, there is no energy consumption while the magnitude of the magnetic field is variable, and the relative angles of the magnetizations of the two ferromagnetic layers are fixed, and the energy is consumed only when the relative angle is changed. Is.

Here, the ferromagnetic material that constitutes the ferromagnetic layer has many microscopic magnetic domains, and the spontaneous magnetization of each magnetic domain cancels each other to reduce the magnetostatic energy to a stable demagnetized state. Then, no magnetic field is generated outside (FIG. 1(a)). By applying an external magnetic field (H) to this demagnetized ferromagnetic material, the domain walls forming the magnetic domain move so that the magnetic domain having the same magnetization as the magnetic field direction grows, and is oriented in the same direction as the external magnetic field. When the number of magnetic domains increases, the magnetic domain as a whole has magnetization (M) in that direction (FIG. 1(b)). In this state, this ferromagnetic substance generates a magnetic field outside. Furthermore, the state where only the magnetic domain facing the same direction as the external magnetic field and the domain wall disappears is the saturation state of magnetization, and in this state the maximum magnetic field is generated outside. The magnetization at this time is called saturation magnetization (Ms) (FIG. 1(c)).
As described above, the ferromagnetic body that did not generate a magnetic field outside in the state of FIG. 1A generates a magnetic field to the outside as the number of magnetic domains facing the same magnetic field direction increases as shown in FIG. Then, as shown in FIG. 1C, only the magnetic domains oriented in the same direction as the external magnetic field generate a magnetic field of the maximum magnitude in that direction.
The ferromagnetic material that generates a magnetic field to the outside in this way is a magnet, but the present inventor has been able to combine the basic structure of this magnet with the domain wall drive layer in the domain wall drive MRAM. The idea of the present invention was to use the domain wall drive layer, which was regarded as the magnetization free layer of the two ferromagnetic layers in the magnetoresistive element, as a magnet.

The concept of this idea will be described with reference to the schematic diagram of FIG.
The domain wall drive layer M has one domain wall DW and is composed of two magnetic domains R and L having opposite magnetizations with the domain wall DW interposed therebetween. In this domain wall drive layer M, the direction and magnitude of the magnetic field generated (supplied) from the end surface Ma of the domain wall drive layer M to the outside can be changed depending on the position of the domain wall DW.
In FIG. 2A, the domain wall DW is closer to the end face Mb side, and the magnetic domain L having the rightward magnetization has a larger volume than the magnetic domain R having the leftward magnetization. Reflecting this, the direction of the magnetic field supplied from the end surface Ma to the outside is rightward, and its magnitude reflects the difference in volume between the magnetic domains L and R.
Further, in FIG. 2B, the domain wall DW is slightly closer to the end face Ma side from the center, and the volume of the magnetic domain R having leftward magnetization is slightly larger than that of the magnetic domain L having rightward magnetization. Reflecting this, the direction of the magnetic field supplied from the end surface Ma to the outside is leftward, and the magnitude thereof reflects the difference in volume between the magnetic domains L and R.
Further, in FIG. 2C, the domain wall DW is closer to the end face Ma side, the magnetic domain R having the leftward magnetization has a larger volume than the magnetic domain L having the rightward magnetization, and the difference in size is shown in FIG. ) Is the opposite of the case. Reflecting this, the direction of the magnetic field supplied from the end surface Ma to the outside is leftward, and the magnitude itself is the same as in the case of FIG. 2A.
The movement of the domain wall DW in FIGS. 2A to 2C can be performed by causing a spin polarization current to flow in the domain wall drive layer M, similarly to the movement of the domain wall DW performed in the domain wall drive MRAM.
As described above, the direction and magnitude of the magnetic field supplied from the domain wall drive layer can be changed depending on the position of the domain wall, and the position of the domain wall does not change unless a spin-polarized current is passed, so that there is no energy consumption and constant. The magnetic field can be continuously supplied to the outside.

The magnetic domain wall drive layer as such a magnet is arranged in the vicinity of the magnetoresistive effect element, and the magnetic domain wall is moved by causing a spin polarization current to flow in the magnetic domain wall drive layer, and the direction of the magnetic field generated from the magnetic domain wall drive layer is changed. By changing the size, the magnetization direction and size of the magnetization free layer of the magnetoresistive effect element are changed, and thereby the relative angle of magnetization between the magnetization fixed layer and the magnetization free layer of the magnetoresistive effect element is controlled. It is the basic concept of the present invention.
The magnetoresistive effect element is an element that utilizes the fact that the resistance value differs depending on the relative angle of magnetization of the magnetization fixed layer and the magnetization free layer. The resistance value is determined depending on whether or not it is turned. Under the idea of using a domain wall drive layer, which was previously regarded as a magnetization free layer in a domain wall drive MRAM, as a magnet capable of supplying a variable magnetic field (hereinafter, the domain wall drive layer in this case is referred to as a “variable magnetic field supply unit”). That is, the resistance value of the magnetoresistive effect element can be freely designed in a multivalued or analog manner by arranging one or more variable magnetic field supply units for the magnetoresistive effect element. Will be possible.

The present invention has been made in view of the above circumstances, and a magnetic field modulation mechanism that can be used in a memory of a new type capable of multilevel recording and analog recording, and a magnetic field modulation element and an analog memory element using the same. , An object is to provide a high frequency filter.

The present invention provides the following means in order to solve the above problems.

(1) A magnetic field modulation mechanism according to an aspect of the present invention is a magnetic field modulation mechanism capable of variably applying a magnetic field to an element that utilizes a response to an external magnetic field, and has a magnetic domain wall. A variable magnetic field supply unit, which is composed of a region and a second region and a third region located between these regions, and is capable of changing the magnetic field supplied by domain wall drive; and a first magnetization direction in contact with the first magnetic region A first domain wall supply layer, a second domain wall supply layer in contact with the second region, and having a second magnetization direction opposite to the first magnetization direction, the first domain wall supply layer, and the first domain wall supply layer. A current source that is electrically connected to the two domain wall supply layers and supplies a current to the variable magnetic field supply unit, and drives the domain wall in the variable magnetic field supply unit by the current supplied from the current source.

(2) In the magnetic field modulation mechanism according to (1), the element may be a magnetoresistive effect element.

(3) In the magnetic field modulation mechanism according to (1) or (2), at least one of the first domain wall supply layer and the second domain wall supply layer has a synthetic antiferromagnetic structure. Good.

(4) In the magnetic field modulation mechanism described in any one of (1) to (3) above, the first domain wall supply layer is provided on the opposite side of the first domain wall supply layer with the variable magnetic field supply unit interposed therebetween. A third domain wall supply layer having the same magnetization direction as the above may be provided.

(5) In the magnetic field modulation mechanism according to any one of (1) to (4), the second domain wall supply layer is provided on the opposite side of the second domain wall supply layer with the variable magnetic field supply unit interposed therebetween. A fourth domain wall supply layer having the same magnetization direction as the above may be provided.

(6) A magnetic field modulation element according to an aspect of the present invention includes a magnetic field modulation mechanism according to any one of (1) to (5) above and a magnetoresistive effect in which magnetic characteristics are changed by the magnetic field modulation mechanism. And an element.

(7) In the magnetic field modulator according to the above (6), a projection region of the variable magnetic field supply unit onto a plane orthogonal to a moving direction of a domain wall overlaps a side surface of a magnetization free layer of the magnetoresistive effect element. Further, the magnetic field modulation mechanism and the magnetoresistive effect element may be arranged.

(8) The magnetic field modulation element according to any one of (6) and (7) may include a plurality of magnetic field modulation mechanisms according to any one of (1) to (4).

(9) In the magnetic field modulation element according to any one of (6) to (8), the first domain wall supply layer is the magnetic layer that is more magnetic than the first domain wall supply layer and the second domain wall supply layer. It may be arranged at a position close to the resistance effect element, and the first domain wall supply layer may have a synthetic antiferromagnetic structure.

(10) An analog memory element according to one aspect of the present invention includes the magnetic field modulation element according to any one of (6) to (9) above, and the direction and/or direction of a magnetic field generated from the variable magnetic field supply unit. Alternatively, there is provided means for writing information in the magnetoresistive effect element by changing the size and reading the resistance value of the magnetoresistive effect element.

(11) A magnetic neuron element according to one aspect of the present invention includes the analog memory element according to (10) above, and uses resistance values of a magnetoresistive effect element included in the analog memory element in a multivalued or analog manner. A current source having a control circuit for controlling so that a write current that can be caused to flow to the variable magnetic field supply unit is provided, and the control circuit has at least three resistance ranges that can be read by the difference in the resistance value of the magnetoresistive effect element. It is possible to control so that a write current of the number of pulses is passed.

(12) A variable high-frequency filter according to one aspect of the present invention can apply a high-frequency current to the analog memory element described in (10) above and extract a signal of a specific frequency corresponding to an external magnetic field.

According to the magnetic field modulation mechanism of the present invention, it is possible to provide a magnetic field modulation mechanism that can be used in a memory capable of a novel type of multilevel recording or analog recording.

It is a conceptual diagram for demonstrating the state where the ferromagnetic material was magnetized, (a) shows a demagnetization state, (b) shows a domain wall movement state, (c) shows a saturation state. It is a conceptual diagram for demonstrating the position of the domain wall in a domain wall drive layer, and the direction and magnitude of the magnetic field which generate|occur|produces the exterior at that time. 1 is a vertical cross-sectional view schematically showing an example of a magnetic field modulation element according to an embodiment of the present invention. It is a conceptual diagram for explaining the relationship between the position of the domain wall and the direction and magnitude of the magnetic field generated from the variable magnetic field supply unit. It is a conceptual diagram of the magnetization curve of a magnetization free layer and a magnetization fixed layer, (a) is the magnetization curve of the magnetization easy axis direction of the magnetization free layer, (b) is the magnetization curve of the magnetization hard axis direction of the magnetization free layer, (c) FIG. 4 is a conceptual diagram of a magnetization curve of the magnetization fixed layer in the easy axis direction. 1 is a vertical cross-sectional view schematically showing an example of a magnetic field modulation element according to an embodiment of the present invention. It is a graph which shows the relationship between the position of the domain wall in a variable magnetic field supply part, and the resistance value of a magnetoresistive effect element. FIG. 6 is a vertical sectional view schematically showing an example of a magnetic field modulation element according to another embodiment of the present invention. It is the figure which showed typically an example of the magnetic field modulation element which concerns on other embodiment of this invention, (a) is a vertical sectional view, (b) is a top view. FIG. 10 is a plan view for explaining that the direction of magnetization of the magnetization free layer is changed by changing the synthetic magnetic field in the magnetic field modulation element shown in FIG. 9. FIG. 6 is a vertical sectional view schematically showing an example of a magnetic field modulation element according to another embodiment of the present invention. FIG. 6 is a vertical sectional view schematically showing an example of a magnetic field modulation element according to another embodiment of the present invention. FIG. 6 is a vertical sectional view schematically showing an example of a magnetic field modulation element according to another embodiment of the present invention. It is a figure which shows the concept of the artificial brain using the magnetic neuron element which concerns on one Embodiment of this invention.

Hereinafter, configurations of a magnetic field modulation mechanism, a magnetic field modulation element, an analog memory element, a high frequency filter, and a magnetic neuron element to which the present invention is applied will be described with reference to the drawings. In the drawings used in the following description, in order to make the features easy to understand, the features may be enlarged for convenience, and the dimensional ratios of the components may not be the same as the actual ones. .. Further, the materials, dimensions, and the like exemplified in the following description are examples, and the present invention is not limited to them, and can be appropriately modified and implemented within a range where the effects of the present invention are exhibited. .. The device of the present invention may include other layers as long as the effects of the present invention are exhibited.

(Magnetic field modulation mechanism and magnetic field modulation element)
FIG. 3 is a vertical sectional view schematically showing an example of the magnetic field modulation element according to the embodiment of the present invention. In FIG. 3, the stacking direction of each layer, that is, the direction (perpendicular direction) orthogonal to the main surface of each layer is defined as the Z direction. Each layer is formed parallel to the XY plane orthogonal to the Z direction.
The magnetic field modulation element 100 shown in FIG. 3 includes a magnetic field modulation mechanism 10 and a magnetoresistive effect element 20.

The magnetic field modulation mechanism of the present invention is a magnetic field modulation mechanism capable of variably applying a magnetic field to an element that utilizes a response to an external magnetic field. The magnetic field modulation mechanism of the present invention can variably apply a magnetic field to a magnetic field applied object.
Here, in the present specification, “an element that utilizes a response to an external magnetic field” is an element that includes a component whose characteristics change when an external magnetic field is applied, and, for example, a magnetoresistive element, There is a magneto-optical element that uses the Faraday effect.
Hereinafter, a case where the element that utilizes the response to the external magnetic field is a magnetoresistive effect element will be described as an example.

The magnetic field modulation mechanism 10 has a domain wall DW, and includes a first region 1a, a second region 1b, and a third region 1c located between these regions, and a variable magnetic field supply that can change the magnetic field supplied by domain wall drive. The first domain wall supply layer 2 in contact with the portion 1 and the first region 1a and having the first magnetization direction; and the second magnetization direction in contact with the second region 1b and opposite to the first magnetization direction. A current source 4 which is electrically connected to the first domain wall supply layer 2 and the second domain wall supply layer 3 and which supplies a current to the variable magnetic field supply unit 1. The domain wall in the variable magnetic field supply unit 1 can be driven by the current supplied from the magnetic field generator 4.

The magnetoresistive effect element 20 has a magnetization fixed layer 21, a magnetization free layer 22, and a nonmagnetic layer 23 sandwiched between these layers.
The magnetization of the magnetization fixed layer 21 is fixed in one direction, and the direction of the magnetization of the magnetization free layer 22 relatively changes, so that the magnetization fixed layer 21 functions as the magnetoresistive effect element 20. When applied to a coercive force difference type (pseudo spin valve type) MRAM, the coercive force of the magnetization fixed layer is larger than the coercive force of the magnetization free layer, and the exchange bias type (spin When applied to a valve (spin valve type) MRAM, the magnetization direction of the magnetization fixed layer is fixed by exchange coupling with the antiferromagnetic layer.
The magnetoresistive effect element 20 is a tunneling magnetoresistive (TMR) element when the nonmagnetic layer 23 is made of an insulator, and a giant magnetoresistive (GMR:) element when the nonmagnetic layer 23 is made of metal. Giant Magnetoresistance) element.
The structure of a known magnetoresistive effect element can be used as the magnetoresistive effect element included in the present invention. For example, each layer may be composed of a plurality of layers, or may be provided with another layer such as an antiferromagnetic layer for fixing the magnetization direction of the magnetization fixed layer.

A known material can be used as the material of the magnetization fixed layer 21. For example, a metal selected from the group consisting of Cr, Mn, Co, Fe and Ni, and an alloy containing one or more of these metals and exhibiting ferromagnetism can be used. Further, an alloy containing these metals and at least one element of B, C, and N can also be used. Specifically, Co-Fe and Co-Fe-B are mentioned.
Further, in order to obtain higher output, it is preferable to use a Heusler alloy such as Co ₂ FeSi. The Heusler alloy includes an intermetallic compound having a chemical composition of X ₂ YZ, X is a transition metal element or a noble metal element of Co, Fe, Ni, or Cu group on the periodic table, and Y is Mn or V. , Cr or Ti group transition metal and can take the elemental species of X, and Z is a typical element of group III to group V. For _example, Co 2 _FeSi, etc. Co 2 MnSi and _{Co 2 Mn 1-a Fe a} Al b Si 1-b can be mentioned.
Further, in order to increase the coercive force of the magnetization fixed layer 21 with respect to the magnetization free layer 23, an antiferromagnetic material such as IrMn or PtMn may be used as a material in contact with the magnetization fixed layer 21. Further, in order to prevent the leakage magnetic field of the magnetization fixed layer 21 from affecting the magnetization free layer, a synthetic ferromagnetic coupling structure may be used.

Further, when the magnetization direction of the magnetization fixed layer 21 is perpendicular to the stacking plane, it is preferable to use a stacked film of Co and Pt. Specifically, the magnetization fixed layer 21 includes [Co(0.24 nm)/Pt(0.16 nm)] ₆ /Ru(0.9 nm)/[Pt(0.16 nm)/Co(0.16 nm)] _4. /Ta (0.2 nm)/FeB (1.0 nm).

The variable magnetic field supply unit 1 in the magnetic field modulation mechanism 10 is made of a ferromagnetic material, and its magnetization direction can be reversed. The variable magnetic field supply unit 1 has a domain wall, and allows the domain wall to move in a direction in which spin-polarized conduction electrons flow by causing a spin polarization current equal to or more than a threshold value to flow in a direction penetrating the domain wall (X direction). it can.

The variable magnetic field supply unit 1 has a domain wall DW, and includes a third region 1c driven by the domain wall DW, and a first region 1a and a second region 1b located on both sides of the third region 1c.
In the variable magnetic field supply unit 1, the first region 1a joined to the first domain wall supply layer 2 whose magnetization is fixed has its magnetization fixed by exchange coupling with the first domain wall supply layer 2, and also has its magnetization fixed. The magnetization of the second region 1b joined to the formed second domain wall supply layer 3 is fixed by exchange coupling with the second domain wall supply layer 3. On the other hand, the magnetization of the third region 1c located between the first region 1a and the second region 1b is reversible.

As a material of the variable magnetic field supply unit 1, a known material that can be used for the magnetization free layer can be used. In particular, a soft magnetic material can be applied. For example, a metal selected from the group consisting of Cr, Mn, Co, Fe and Ni, an alloy containing one or more of these metals, and these metals and at least one or more elements of B, C and N are included. The alloy etc. which are used can be used. Specific examples thereof include Co-Fe, Co-Fe-B, and Ni-Fe.

The variable magnetic field supply unit is not particularly limited in shape as long as it can supply a variable magnetic field to the outside by driving the domain wall. The most typical shape may be, for example, an elongated shape. Further, the entire shape does not have to be uniform.
The length of the variable magnetic field supply unit 1, that is, the total length of the first region and the second region and the third region located between these regions is preferably 60 nm or more. Usually, if it is less than 60 nm, it tends to be a single magnetic domain, and it may not have a domain wall.

The thickness of the variable magnetic field supply unit 1 is not particularly limited as long as it functions as a variable magnetic field supply unit, but can be set to, for example, 2 to 60 nm. When the thickness of the variable magnetic field supply unit 1 is 60 nm or more, a domain wall may be formed in the stacking direction. However, whether or not a domain wall is formed in the stacking direction depends on the balance with the shape anisotropy of the variable magnetic field supply unit. Therefore, as long as the thickness of the variable magnetic field supply unit 1 is less than 60 nm, there is no problem because a domain wall is formed.

The magnetic field modulation mechanism 10 and the magnetoresistive effect element 20 are arranged so that the projection region of the variable magnetic field supply unit 1 on the surface orthogonal to the moving direction of the domain wall overlaps the side surface of the magnetization free layer 22 of the magnetoresistive effect element 20. It is preferably arranged. This is because the magnetic field Hex generated from the end surface 1A of the variable magnetic field supply unit 1 is efficiently supplied to the magnetization free layer 22.
Further, the magnetic field modulation mechanism 10 is configured so that the projection region of the variable magnetic field supply unit 1 on the plane orthogonal to the moving direction of the domain wall is included in the side surface of the magnetization free layer 22 of the magnetoresistive effect element 20 (see the dotted line in FIG. 3 ). It is more preferable that the magnetoresistive effect element 20 is arranged. This is because the magnetic field Hex generated from the end surface 1A of the variable magnetic field supply unit 1 is efficiently supplied by the magnetization free layer 22.

In FIG. 3, arrows M1, M2, M3, and M4 indicate the magnetization directions of the respective layers, and arrows M5 and M6 respectively indicate the domain wall DW of the variable magnetic field supply unit 1 as a boundary. The magnetization direction of the portion on the side of the first domain wall supply layer 2 and the magnetization direction of the portion on the side of the second domain wall supply layer 3 are shown with the domain wall DW as a boundary.
In the example shown in FIG. 3, the variable magnetic field supply unit 1, the first domain wall supply layer 2, the second domain wall supply layer 3, the magnetization fixed layer 21, and the magnetization free layer 22 have the in-plane magnetic anisotropy (the in-plane easy magnetization axis). 2), the layers may be perpendicular magnetic films having perpendicular magnetic anisotropy (perpendicular magnetic easy axis). For example, NiFe is a material that easily forms an in-plane magnetized film. A Co/Ni laminated film is an example of a material that is easy to form a perpendicular magnetization film.
The use of the in-plane magnetized film has a high MR ratio and makes it difficult to write by STT at the time of reading, so that a large reading voltage can be used. On the other hand, when the perpendicular magnetization film is used, the resistance to thermal agitation is large, and thus it is difficult to erase data.

At least one of the first domain wall supply layer 2 and the second domain wall supply layer 3 preferably has a synthetic antiferromagnetic structure. Here, the synthetic antiferromagnetic structure is a structure in which two ferromagnetic layers sandwich a magnetic coupling layer such as Ru, and the magnetic coupling layer is antiferromagnetic between the two ferromagnetic layers sandwiching it. It is a structure that causes ferromagnetic coupling. In this structure, the magnetization direction of one ferromagnetic layer is strongly held by the other ferromagnetic layer (antiferromagnetic layer).
With this configuration, it is possible to fix the magnetization directions of the first domain wall supply layer and the second domain wall supply layer to opposite sides by one-time magnetic field annealing. In addition, when the domain wall supply layer having the synthetic antiferromagnetic structure has improved resistance to an external magnetic field and the magnetization direction of the other domain wall supply layer not having the synthetic antiferromagnetic structure is no longer antiparallel, a strong magnetic field is generated. The stability of the magnetization direction can be restored by simply applying.

Of the first domain wall supply layer 2 and the second domain wall supply layer 3, it is preferable that the first domain wall supply layer 2 arranged near the magnetoresistive element has a synthetic antiferromagnetic structure.
Since the synthetic antiferromagnetic structure is provided in the first domain wall supply layer 2, the magnetic field applied to the magnetoresistive effect element 20 from the first domain wall supply layer 2 can be suppressed. The variable magnetic field supply unit 1 has a function of applying an arbitrary magnetic field to the magnetoresistive effect element 20, but if the first domain wall supply layer 2 does not have a synthetic antiferromagnetic structure, the variable domain supply unit 1 also receives from the first domain wall supply layer 2. A magnetic field is applied to the magnetoresistive effect element 20. In this case, the magnetic field from the variable magnetic field supply unit 1 is modulated, but the magnetic field from the first domain wall supply layer 2 is constant, so the origin of the magnetic field is shifted by the amount of the magnetic field from the first domain wall supply layer 2. There is a problem that it ends up. By having the synthetic antiferromagnetic structure, it becomes possible to suppress the magnetic field from the first domain wall supply layer 2.

The magnetoresistive effect element 20 shown in FIG. 3 may be a memory cell which is a part of MRAM. Also in this case, the magnetoresistive effect element 20 has a laminated structure in which two ferromagnetic layers are laminated with the nonmagnetic layer interposed therebetween. The two ferromagnetic layers are a magnetization fixed layer (pin layer) whose magnetization direction is fixed and a magnetization free layer (free layer) whose magnetization direction is reversible. The value of the electric resistance of the magnetoresistive effect element is larger when the magnetization directions of the magnetization fixed layer and the magnetization free layer are antiparallel than when they are parallel. In the magnetoresistive effect element which is the memory cell of the conventional MRAM, the parallel state of the magnetization is associated with the data “0” and the antiparallel state is associated with the data “1” by utilizing the difference in the magnitude of the resistance value. As a result, the data is stored in a nonvolatile manner. The data is read by passing a read current through the magnetoresistive effect element (through the laminated structure) and measuring the resistance value of the magnetoresistive effect element. Data writing in the conventional MRAM is performed by flowing a spin polarization current to reverse the magnetization direction of the magnetization free layer.

As shown in FIG. 3, when the domain wall DW is closer to the end surface 1B side of the variable magnetic field supply unit 1 and the volume of the magnetic domain L having the rightward magnetization is larger than that of the magnetic domain R having the leftward magnetization, this is reflected. The direction of the magnetic field Hex supplied from the end face 1A to the outside is rightward, and its magnitude reflects the difference in volume between the magnetic domains L and R.
In this case, a rightward external magnetic field Hex acts on the magnetoresistive element 20.

On the other hand, as shown in FIG. 4, by causing a current to flow through the variable magnetic field supply unit 1 via the first domain wall supply layer 2 and the second domain wall supply layer 3 by the current source 4, the domain wall DW is moved toward the end face 1A side. When the magnetic domain R having the leftward magnetization has a larger volume than the magnetic domain L having the rightward magnetization, the direction of the magnetic field Hex supplied from the end facet 1A to the outside is opposite to the leftward direction in FIG. Become.
Depending on the magnitude of the external magnetic field Hex, the magnetization direction of the magnetization free layer 22 of the magnetoresistive effect element 20 is reversed as shown in FIG.
When the magnetoresistive effect element 20 shown in FIGS. 3 and 4 is a part of the MRAM, in the magnetoresistive effect element 20 shown in FIG. 3, the magnetization directions of the magnetization fixed layer and the magnetization free layer are antiparallel to each other. On the other hand, in the magnetoresistive effect element 20 shown in FIG. 4, the resistance values are small because the magnetization directions of the magnetization fixed layer and the magnetization free layer are antiparallel, and the data values are “1” and “0”, respectively. Has been recorded.
In this way, the magnetic field modulation mechanism of the present invention can be used as a new writing means in the conventional MRAM that records in binary.

Next, a method of applying multi-valued or analog recording by applying the magnetic field modulation mechanism of the present invention to the configuration of the conventional MRAM will be described.

FIG. 5 is a conceptual diagram of the magnetization curves of the magnetization free layer and the magnetization fixed layer.
5A and 5C are conceptual diagrams of a magnetization curve of the magnetization free layer in the easy axis direction (X direction) and a magnetization curve of the magnetization fixed layer in the easy axis direction, respectively. As shown in FIG. 5A, in the magnetization easy axis direction of the magnetization free layer, when the applied external magnetic field H is increased, the external magnetic field H is steeply magnetized and saturated. On the other hand, the magnetization fixed layer has a common point of being abruptly magnetized by an external magnetic field H, but is different in that it is saturated by an external magnetic field H larger than that of the magnetization free layer.
On the other hand, FIG. 5B is a conceptual diagram of a magnetization curve in the hard axis direction (Y direction) of the magnetization free layer. In the hard axis direction, the magnetization of the magnetization free layer is gradually magnetized as the applied external magnetic field H is increased.

In a conventional MRAM, in general, the magnetization direction of the magnetization free layer is reversed in the easy axis direction of the magnetization free layer to make the magnetization direction of the magnetization free layer parallel or anti-parallel to the magnetization direction of the magnetization fixed layer. Writing (recording) in binary. As the writing method, in the “STT method” that uses the current mainstream spin transfer torque, a spin current having the same spin state as that of the magnetization fixed layer is generated by passing a write current through the magnetoresistive effect element. Polarized electrons are supplied from the magnetization fixed layer to the magnetization free layer or extracted from the magnetization free layer to the magnetization fixed layer, and as a result, the magnetization of the magnetization free layer is inverted by the spin transfer effect. In this way, the direction of the write current passing through the magnetoresistive effect element defines the magnetization direction of the magnetization free layer.
As described above, since the method of reversing the magnetization direction by passing the write current through the magnetoresistive effect element, it is considered difficult to write (record) more than two values in the future. ..
On the other hand, in writing (recording) by the magnetic field modulation mechanism of the present invention, a magnet (magnetic field modulation mechanism of the present invention) is arranged in the vicinity of the magnetoresistive effect element, and the magnetization direction of the magnetization free layer is fixed by the magnetic field. Since it is a method of doing so, it is possible to fix in two or more magnetization directions. The magnetic field of this magnet does not change unless a current is passed through the variable magnetic field supply unit to move the domain wall. That is, according to the writing (recording) by the magnetic field modulation mechanism of the present invention, multivalued or analog recording can be performed.

Hereinafter, a method of multilevel recording or analog recording by writing (recording) by the magnetic field modulation mechanism of the present invention will be described.
The first embodiment is a case of utilizing the direction of magnetization in the hard axis direction of the magnetization free layer. As shown in FIG. 5B, the direction and magnitude of magnetization in the hard axis direction of the magnetization free layer gradually and continuously change according to the magnitude of the applied external magnetic field.
FIG. 6 has a configuration similar to that of FIG. 4, except that the hard axis directions of the two ferromagnetic layers of the magnetoresistive effect element are oriented in the X direction. The magnetoresistive effect element 20 shown in FIG. 6 is assumed to be a part of the MRAM.
In the configuration shown in FIG. 6, the magnetization of the magnetization free layer 22 of the magnetoresistive effect element 20 is oriented in the −X direction, and is parallel to the magnetization of the magnetization fixed layer 21. At this time, depending on the position of the domain wall DW of the variable magnetic field supply unit 1, the direction of the magnetic field Hex emitted from the end surface 1A of the variable magnetic field supply unit 1 is the −X direction.
From the state where the domain wall DW is in the vicinity of the side surface 2B on the +X side of the first domain wall supply layer 2 in the plan view from the +Z direction (P1 in FIG. 6), a current is passed through the variable magnetic field supply unit 1 to cause the domain wall DW to flow. When the position of is moved in the +X direction, the magnitude of the magnetic field Hex in the −X direction becomes smaller (see FIG. 2B), and the domain wall DW is changed in plan view from the +Z direction. When the magnetic field Hex reaches the center (P2 in FIG. 6), the magnitude of the magnetic field Hex becomes zero, and when the position of the domain wall DW is further moved in the +X direction, the direction of the magnetic field Hex becomes +. Facing in the X direction, the size increases.
Consider how the magnetization of the magnetization free layer 22 changes with respect to changes in the direction and magnitude of the magnetic field Hex. The application time is until the magnetization direction and magnitude of the magnetization free layer 22 change as desired and become constant. When the direction of the magnetic field Hex begins to face the +X direction, the magnitude of the magnetization of the magnetization free layer 22 that faces the −X direction begins to decrease, and the magnitude of the magnetic field Hex in the +X direction becomes a predetermined magnitude. When it exceeds, the magnetization direction of the magnetization free layer 22 faces the +X direction, and the magnitude of the magnetization direction of the magnetization free layer 22 in the +X direction also increases as the magnitude of the magnetic field Hex increases.

FIG. 7 is a graph showing the relationship between the position of the domain wall in the variable magnetic field supply unit 1 and the resistance value of the magnetoresistive effect element. P1 to P3 on the horizontal axis correspond to the positions of the domain walls shown in FIG.
The position of the domain wall in the variable magnetic field supply unit 1 corresponds to the magnitude of the magnetization of the magnetization free layer.
In this way, by moving the position of the magnetic domain wall of the variable magnetic field supply unit 1, the direction and/or the magnitude of the external magnetic field applied to the magnetoresistive effect element is changed, and the direction and/or the magnitude of the magnetization of the magnetization free layer are changed. Can be changed. Then, the change in the magnitude of the magnetization of the magnetization free layer changes stepwise or continuously depending on whether the position of the domain wall in the variable magnetic field supply unit 1 is changed stepwise or continuously. Can be made. Thereby, the magnitude of the resistance value of the magnetoresistive effect element can be changed stepwise or continuously. In this way, multi-value recording or analog recording becomes possible.
The case where the magnetization of the magnetization free layer in the hard axis direction is changed has been described above, but the present invention can be applied to the magnetization in the easy axis direction. However, since the change in the magnetization in the easy axis direction with respect to the external magnetic field is steeper than the magnetization in the hard axis direction, the control becomes difficult accordingly.

The second embodiment of multi-level recording or analog recording by writing (recording) by the magnetic field modulation mechanism of the present invention is a method using a plurality of magnetic field modulation mechanisms of the present invention. That is, this is a method of writing (recording) on one magnetoresistive effect element using a plurality of magnetic field modulation mechanisms. The principle of multi-valued recording or analog recording is the same as in the first embodiment.
FIG. 8 is a vertical sectional view schematically showing an example of the magnetic field modulation element according to another embodiment of the present invention.
The magnetic field modulation element 200 shown in FIG. 8 includes two magnetic field modulation mechanisms 10, 10 ′ and a magnetoresistive effect element 20. Note that, in FIG. 8, the two magnetic field modulation mechanisms 10 and 10 ′ are only partially drawn.

In the magnetic field modulation element 200 shown in FIG. 8, the magnetic field modulation mechanism 10′ is provided on the side opposite to the magnetic field modulation mechanism 10 with the magnetoresistive effect element 20 in between in the configuration shown in FIG. The configuration is different. In particular, another variable magnetic field supply unit 1'is arranged at a position symmetrical to the variable magnetic field supply unit 1 with the magnetoresistive effect element 20 interposed therebetween.
The other magnetic field modulation mechanism 10 ′ also has the same configuration as the magnetic field modulation mechanism 10. That is, a variable magnetic field supply unit 1′ having a domain wall DW′, composed of a first region and a second region and a third region located between these regions, and capable of changing the magnetic field supplied by the domain wall drive; A first domain wall supply layer that is in contact with the first region and has a first magnetization direction, and a second domain wall supply layer that is in contact with the second region and has a second magnetization direction that is opposite to the first magnetization direction. ', and a current source 4'which is electrically connected to the first domain wall supply layer and the second domain wall supply layer 3'and supplies a current to the variable magnetic field supply unit 1'.

In the magnetic field modulation element 200, external magnetic fields Hex and Hex′ can be applied to the magnetoresistive effect element 20 from the magnetic field modulation mechanism 10 and the magnetic field modulation mechanism 10 ′ arranged at a position symmetrical to the magnetic field modulation mechanism 10. That is, in addition to the external magnetic field Hex from the magnetic field modulation mechanism 10, as the external magnetic field Hex' from the magnetic field modulation mechanism 10', a current is supplied to the variable magnetic field supply unit 1'by the current source 4'to drive the domain wall DW'. Thus, the magnetoresistive effect element 20 can be provided with a desired orientation and/or size.
In this configuration, the external magnetic field applied to the magnetoresistive effect element 20 is controlled not by one magnetic field modulation mechanism but by two magnetic field modulation mechanisms, so that the external magnetic field can be controlled more precisely.
Further, by setting the external magnetic field Hex′ from the magnetic field modulation mechanism 10 ′ to have the same direction and/or magnitude as the external magnetic field Hex from the magnetic field modulation mechanism 10, a stable magnetic field is given to the magnetoresistive effect element 20. be able to.

The third embodiment of multilevel recording or analog recording by writing (recording) by the magnetic field modulation mechanism of the present invention is also common to the second embodiment in that a plurality of magnetic field modulation mechanisms of the present invention are used, but a plurality of magnetic fields are used. The difference is that the modulation mechanism and the magnetoresistive effect element are not arranged in a straight line.
The magnetic field modulation element shown in FIG. 9 includes two magnetic field modulation mechanisms and one magnetoresistive effect element 20.
FIG. 9A shows variable magnetic field supply units 11A and 11B according to the present invention, which are arranged orthogonal to each other on a plane parallel to the XY plane around the side surface of the magnetoresistive effect element 20 (particularly the side surface of the magnetization free layer 22). A schematic sectional view of an example of the magnetic field modulation element of the present invention provided with two, and a schematic plan view taken along a plane including the magnetization free layer 22 are shown in (b). In FIG. 9, the first domain wall supply layer, the second domain wall supply layer, and the current source included in each magnetic field modulation mechanism are not shown.

In FIG. 9, the variable magnetic field supply units 11A and 11B supply external magnetic fields Hex1 and Hex2 from their end faces, respectively. In this case, a combined magnetic field of the external magnetic fields Hex1 and Hex2 acts on the magnetization free layer 22.
Based on the concept of a vector, two vectors having different directions can be used as a basic vector and a composite vector of all directions in a plane including these vectors can be created. Then, the two variable magnetic field supply units 11A and 11B can be used to generate an external magnetic field (synthetic magnetic field) in all directions in the XY plane. That is, by controlling the magnitudes of the magnetic fields supplied from the two variable magnetic field supply units 11A and 11B to control the positions of the respective magnetic domain walls, in-plane parallel to the magnetization free layer of the magnetoresistive effect element ( An external magnetic field (synthetic magnetic field) in all directions in the XY plane can be given. Then, the magnetization of the magnetization free layer can be oriented in any direction in the XY plane.
For example, due to the external magnetic field (composite magnetic field) generated by the two variable magnetic field supply units 11A and 11B, the magnetization of the magnetization free layer has the magnetization in the direction shown in FIG.

By moving the positions of the domain walls of the two variable magnetic field supply units 11A and 11B, the direction and/or the magnitude of the external magnetic field (composite magnetic field) given to the magnetoresistive effect element is changed, and the magnetization direction of the magnetization free layer is changed. And/or the size can be varied. Then, the change in the magnitude of the magnetization of the magnetization free layer depends on whether the position of the domain wall in the variable magnetic field supply units 11A and 11B is changed stepwise or continuously, depending on whether it changes stepwise or continuously. Can also be changed. Thereby, the magnitude of the resistance value of the magnetoresistive effect element can be changed stepwise or continuously. In this way, multi-value recording or analog recording becomes possible.

Furthermore, in addition to two vectors having different directions, a third vector not included in the plane including these vectors can be used as a basic vector to create a composite vector in all directions of the three-dimensional space. Then, in addition to the two variable magnetic field supply units 11A and 11B, a third variable magnetic field supply unit that is not included in the plane including the variable magnetic field supply units 11A and 11B is used to An external magnetic field (composite magnetic field) can be created.
That is, in addition to the two variable magnetic field supply units 11A and 11B shown in FIG. 9, by providing a third variable magnetic field supply unit that is not included in the plane including the variable magnetic field supply units 11A and 11B. An external magnetic field (composite magnetic field) in all directions of the three-dimensional space created by these three variable magnetic field supply units can be applied to the magnetization free layer of the magnetoresistive element. Therefore, the magnetization of the magnetization free layer can be oriented in any direction in the three-dimensional space.

FIG. 11 is a cross-sectional view schematically showing an example of another embodiment of the magnetic field modulation mechanism. In FIG. 11, the current source is not shown.
As shown in FIG. 11, a third domain wall supply layer 32 having the same magnetization direction as that of the first domain wall supply layer 2 is provided on the opposite side of the first domain wall supply layer 2 across the variable magnetic field supply unit 1. Good.
A third domain wall supply layer 32 is installed on the side opposite to the side where the first domain wall supply layer 2 is installed, with the variable magnetic field supply unit 1 as the center, and the magnetization direction of the third domain wall supply layer 32 is the first domain wall. By setting the magnetization direction of the supply layer 2 to be the same, it is possible to suppress noise that occurs when a current is passed through the first domain wall supply layer 2 and the third domain wall supply layer 32.

Further, as shown in FIG. 11, a fourth domain wall supply layer 33 having the same magnetization direction as the second domain wall supply layer 3 is provided on the opposite side of the second domain wall supply layer 3 with the variable magnetic field supply unit 1 interposed therebetween. You may prepare.
A fourth domain wall supply layer 33 is installed on the side opposite to the side where the second domain wall supply layer 3 is installed with the variable magnetic field supply unit 1 as the center, and the magnetization direction of the fourth domain wall supply layer 33 is the second domain wall. By setting the magnetization direction of the supply layer 3 to be the same, it is possible to suppress noise generated when a current is applied to the second domain wall supply layer 3 and the fourth domain wall supply layer 33.
In the example shown in FIG. 11, both the third domain wall supply layer 32 and the fourth domain wall supply layer 33 are provided, but the configuration may be provided with only one of them.

FIG. 12 is a sectional view schematically showing an example of still another embodiment of the magnetic field modulation mechanism.
In the magnetic field modulation mechanism illustrated so far, the end surface 2A on the −X side and the end surface 3B on the +X side of the first domain wall supply layer 2 and the second domain wall supply layer 3 are located on the −X side of the variable magnetic field supply unit 1, respectively. Although the arrangement is such that the end faces 1A and +X side end face 1B coincide (are flush) with each other (see FIG. 3), the present invention is not limited to this.

For example, as shown in FIG. 12, the −X side surface 12A of the first domain wall supply layer 12 does not coincide with the −X side end surface 31A of the variable magnetic field supply unit 31, and the first domain wall supply layer 12 approaches the second domain wall supply layer 3 side. It may be configured to be arranged.
With this configuration, the influence of the magnetic flux generated from the first domain wall supply layer 12 can be reduced. A method of reducing the influence of the magnetic flux generated from the first domain wall supply layer 12 is that the first domain wall supply layer 12 has a synthetic antiferromagnetic structure, and the magnetic flux circulates inside the first domain wall supply layer 12 to supply the first domain wall. There is also a method of reducing the influence of the magnetic flux emitted from the layer 12.
In the configuration shown in FIG. 12, the variable magnetic field supply unit 31 includes a third region 31c in which the domain wall DW can be driven and regions on both sides thereof are a first region 31a and a second region 31b, and the first region 31a is + It is composed of a region overlapping the first domain wall supply layer 12 and a region located on the −X side thereof in a plan view from the Z direction.

FIG. 13 is a sectional view schematically showing an example of still another embodiment of the magnetic field modulation mechanism.
In the magnetic field modulation mechanism illustrated so far, the variable magnetic field supply unit has a uniform shape as a whole, but the invention is not limited to this. The magnetoresistive effect element can have a shape capable of effectively applying a magnetic field.

For example, the end on the magnetoresistive effect element side of the variable magnetic field supply unit 1 shown in FIG. 3 and the like is formed of the end face 1A parallel to the YZ plane, but as shown in FIG. The variable magnetic field supply unit 41 may be sharpened toward the resistance effect element.
With this configuration, the direction of the magnetization of the magnetization free layer can be changed and fixed by a magnetic field in which the magnetic field supplied to the magnetoresistive effect element is less concentrated.
In the example shown in FIG. 13, the end portion 41A of the variable magnetic field supply unit 41 on the magnetoresistive effect element side is sharp, but even if it is not sharp, the magnetoresistive effect element is configured to have a protruding end portion. The magnetic field supplied to can be concentrated.

In the above, the case where the magnetic field modulation mechanism of the present invention alone is used to change the direction and/or size of the magnetization of the magnetization free layer in the magnetoresistive effect element has been described, but the magnetic field modulation mechanism of the present invention is used as an assisting means. May be. Therefore, in the conventional MRAM, the magnetic field modulation mechanism of the present invention can be used as the assisting means.

In the magnetic field modulation element of the present invention, the positional relationship between the magnetoresistive effect element and the magnetic field modulation mechanism (particularly the variable magnetic field supply unit) can be varied, and the magnetization of the magnetization free axis in the magnetoresistive effect element mainly depends on the magnetic field modulation mechanism. Can be determined in terms of how to change the orientation and/or size of the.
Further, although the magnetic field modulation element of the present invention can record information in a multivalued or analog manner, it goes without saying that the information can be recorded in binary.

As a method of manufacturing the magnetic field modulation mechanism and the magnetic field modulation element of the present invention, a known method of manufacturing MRAM including a method of manufacturing a conventional domain wall drive MRAM can be used.

(Analog memory device)
The analog memory device of the present invention includes the magnetic field modulation device of the present invention, and by changing the position of the magnetic domain wall by passing a current through the variable magnetic field supply unit, the magnitude of the magnetic field generated from the variable magnetic field supply unit is changed. It is provided with means for writing information and reading the resistance value of the magnetoresistive effect element.
As the means for reading the resistance value of the magnetoresistive effect element, the same means as in the conventional MRAM (for example, a current passing through the magnetoresistive effect element is flowed to read the resistance value) can be used.

By using the magnetic field modulation element of the present invention, a change in the applied magnetic field is written as information (data), and a means for supplying a read current to the magnetic field modulation element to read the information is used. It can be recorded and read in a multivalued or analog manner.

(Magnetic neuron element)
The magnetic neuron memory of the present invention includes the analog memory element of the present invention, and a write current is supplied to the variable magnetic field supply unit so that the resistance value of the magnetoresistive effect element included in the analog memory element can be used in a multivalued or analog manner. A current source having a control circuit for controlling so as to flow, and the control circuit can control so as to flow a write current in at least three resistance ranges that can be read due to a difference in resistance value of the magnetoresistive effect element. is there.

The analog memory device of the present invention can be used as a magnetic neuron device that is a device that simulates synapse operation. It is preferable that the synapse has a linear output with respect to an external stimulus. Further, it is preferable that there is no hysteresis when a reverse load is applied, and that reversible. As shown in FIG. 7, in the magnetoresistive effect element of the present invention, the position of the domain wall continuously changes. The horizontal axis of FIG. 7 represents the moving distance of the domain wall, which can be regarded as the number of pulses of the current passed through the variable magnetic field supply unit, and a relatively linear resistance change can be shown. Also, since the resistance change can be changed depending on the magnitude of the current and the time of the applied current pulse, consider the magnitude and direction of the current and the time of the applied current pulse as an external load. You can

(Early stage of memory)
For example, even if the domain wall of the variable magnetic field supply unit moves, the read resistance does not change depending on the magnitude of the magnetic field generated by the variable magnetic field supply unit. This state can be called the initial stage of memory. Although not recorded as data in the initial stage of storage, it is ready for recording data.

(Main memory stage)
When the read resistance starts to change, a current is further passed to form a load from the outside, and the read resistance changes in proportion to the load to some extent. This is the main memory stage. That is, the case where the reading resistance changes can be called the main memory stage of memory. The stage immediately before the read resistance starts to change can be defined as memory or no memory, and the stage where the read resistance stops changing can be defined as no memory or memory. As a matter of course, when the write current is reversed, it has the opposite effect.

(Memory deepening stage)
When the domain wall is moved to such an extent that the magnitude of the magnetization of the domain wall drive layer is not affected, the output during reading does not change. That is, it means that the memory is not lost even when an external load is applied, and this can be called a memory deepening stage. The case where the domain wall is arranged at such a position can be called a deepening stage of memory.
If the currents flowing between the first domain wall supply layer 2 and the second domain wall supply layer 3 are reversed, the correspondence between the initial stage of memory, the main memory stage and the deepening stage of memory, and each memory unit is reversed. ..

(Memory forgetting stage)
The memory can be forgotten by restoring the direction and magnitude of the magnetization of the domain wall drive layer.

(Artificial brain using magnetic neuron element)
The magnetic neuron element of the present invention is a memory that can simulate the movement of synapses and go through the main memory stage. The analog memory element of the present invention can be placed on a plurality of circuits to simulate a brain. With the arrangement of evenly arrayed vertically and horizontally like a general memory, it is possible to form a highly integrated brain.
Further, as shown in FIG. 14, in the arrangement in which a plurality of magnetic neuron elements having a specific circuit are arrayed as one lump, it is possible to form a brain having a different degree of recognition from an external load. For example, it is possible to create an individuality such as a brain that is sensitive to color or a brain that has a high degree of understanding of language. In other words, the information obtained from an external sensor is subjected to recognition processing in the five sense areas optimized for visual, taste, tactile, olfactory and auditory recognition, and further, in the logical thinking area, the following It is possible to create a process of deciding behavior. Furthermore, when the material of the variable magnetic field supply unit is changed, the driving speed of the domain wall with respect to the load and the method of forming the domain wall are changed, so that it is possible to form an artificial brain that is unique to the change.

(Variable high frequency filter)
The variable high-frequency filter of the present invention can apply a high-frequency current to the analog memory element of the present invention to extract a signal of a specific frequency corresponding to an external magnetic field.

1, 10A, 10B, 31, 41 Variable magnetic field supply unit 1a First region 1b Second region 1c Third region 2, 12 First domain wall supply layer 3 Second domain wall supply layer 4 Current source 10 Magnetic field modulation mechanism 20 Magnetoresistive effect Element 21 Magnetization pinned layer 22 Magnetization free layer 23 Nonmagnetic layer 32 Third domain wall supply layer 33 Fourth domain wall supply layer 100, 200 Magnetic field modulation element DW Domain wall

Claims (9)

A magnetic field modulation mechanism, and a magnetoresistive effect element whose magnetic characteristics can be changed by the magnetic field modulation mechanism,
The magnetic field modulation mechanism has a domain wall, is composed of a first region and a second region, and a third region located between these regions, and a variable magnetic field supply unit capable of changing a magnetic field supplied by driving the domain wall, A first domain wall supply layer that is in contact with the first region and has a first magnetization direction, and a second domain wall that is in contact with the second region and has a second magnetization direction that is opposite to the first magnetization direction. A supply layer, a current source electrically connected to the first domain wall supply layer and the second domain wall supply layer, and supplying a current to the variable magnetic field supply unit. For driving a domain wall in the variable magnetic field supply unit,
The magnetic field modulation mechanism and the magnetoresistive effect element are arranged such that a projection region of the variable magnetic field supply unit on a plane orthogonal to the moving direction of the domain wall overlaps a side surface of the magnetization free layer of the magnetoresistive effect element. The magnetic field modulation element . The magnetic field modulation element according to claim 1, wherein at least one of the first domain wall supply layer and the second domain wall supply layer has a synthetic antiferromagnetic structure . The third domain wall supply layer having the same magnetization direction as that of the first domain wall supply layer is provided on the opposite side of the first domain wall supply layer with the variable magnetic field supply unit interposed therebetween. The magnetic field modulation element according to . The fourth domain wall supply layer having the same magnetization direction as that of the second domain wall supply layer is provided on the opposite side of the second domain wall supply layer with the variable magnetic field supply unit interposed therebetween. The magnetic field modulator according to claim 1 . The magnetic field modulation element according to claim 1, comprising a plurality of the magnetic field modulation mechanisms. Of the first domain wall supply layer and the second domain wall supply layer, the first domain wall supply layer is located closer to the magnetoresistive effect element, and the first domain wall supply layer is a synthetic antiferromagnetic layer. The magnetic field modulation element according to claim 1, which has a structure . The magnetic field modulation element according to any one of claims 1 to 7 is provided, and information is written to the magnetoresistive effect element by changing a direction and/or a magnitude of a magnetic field generated from the variable magnetic field supply unit. An analog memory device having means for reading the resistance value of the magnetoresistive effect element. The analog memory element according to claim 7 is provided, and a control is performed so that a write current that allows the resistance value of the magnetoresistive effect element included in the analog memory element to be used in a multivalued or analog manner is supplied to the variable magnetic field supply unit. A magnetic neuron element comprising a current source having a control circuit, wherein the control circuit can control so as to flow a write current of a pulse number within at least three resistance ranges that can be read by a difference in resistance value of the magnetoresistive effect element. A variable high-frequency filter capable of applying a high-frequency current to the analog memory element according to claim 7 and extracting a signal of a specific frequency corresponding to an external magnetic field.

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