Classifications

• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N50/00—Galvanomagnetic devices
  • H10N50/10—Magnetoresistive devices
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11C—STATIC STORES
  • G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
  • G11C11/02—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements
  • G11C11/16—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using elements in which the storage effect is based on magnetic spin effect
  • G11C11/161—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using elements in which the storage effect is based on magnetic spin effect details concerning the memory cell structure, e.g. the layers of the ferromagnetic memory cell
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11C—STATIC STORES
  • G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
  • G11C11/02—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements
  • G11C11/16—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using magnetic elements using elements in which the storage effect is based on magnetic spin effect
  • G11C11/165—Auxiliary circuits
  • G11C11/1675—Writing or programming circuits or methods
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11C—STATIC STORES
  • G11C11/00—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor
  • G11C11/18—Digital stores characterised by the use of particular electric or magnetic storage elements; Storage elements therefor using Hall-effect devices
• • H—ELECTRICITY
  • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
  • H10N50/00—Galvanomagnetic devices
  • H10N50/80—Constructional details
  • H10N50/85—Materials of the active region

Definitions

• the present invention relates to a memory element.
• Patent Document 1 discloses technology relating to a magnetoresistance effect element with a magnesium oxide passivation layer and a high-speed, ultra-low power consumption nonvolatile memory using the same.
• the memory has a tunnel magnetoresistance effect (TMR) film consisting of a ferromagnetic memory layer, an insulating layer, and a ferromagnetic fixed layer, and a protective layer, and an MgO passivation layer on the side walls of the orientation control layer, thereby suppressing element diffusion from each layer of the tunnel magnetoresistance effect (TMR) element due to heat treatment at 350 degrees or more, and realizing a magnetic memory cell and magnetic random access memory with stable high output read and low current write characteristics.
• TMR tunnel magnetoresistance effect
• CoFeB CoFeB
• MgO is used for the insulating layer
• the MgO passivation layer has a (001) orientation.
• a memory element includes a fixed layer and a storage layer.
• the fixed layer is made of a first ferromagnetic material having spontaneous magnetization, and the magnetization direction of the first ferromagnetic material is configured to be fixed regardless of the data written to the memory element.
• the storage layer is configured to include an antiferromagnetic material and a second ferromagnetic material having spontaneous magnetization.
• the antiferromagnetic material exhibits an anomalous Hall effect, and the sign of the anomalous Hall coefficient of the antiferromagnetic material is configured to be reversible depending on the data written to the memory element.
• the magnetization direction of the second ferromagnetic material is configured to be reversible in conjunction with the sign of the anomalous Hall coefficient of the antiferromagnetic material depending on the data written to the memory element.
• This configuration makes it possible to provide a new memory device.
• FIG. 1 is a cross-sectional view showing an example of the structure of a memory element 10 according to an embodiment.
• FIG. 2 is a front view showing an example of the structure of a memory element 11 according to a first modified example of the present embodiment.
• FIG. 11 is a diagram showing an example of the structure of a memory element 12 according to a second modified example of the present embodiment.
• FIG. 11 is a front view showing an example of the structure of a memory element 13 according to a third modified example of the present embodiment.
• FIG. 11 is a front view showing an example of the structure of a memory element 14 according to a fourth modified example of the present embodiment.
• FIG. 13 is a front view showing an example of the structure of a memory element 15 according to a fifth modified example of the present embodiment.
• 1A and 1B are diagrams illustrating an example of the configuration of a memory element 20 including another example of a memory layer M.
• the program for implementing the software used in this embodiment may be provided as a non-transitory computer-readable recording medium, or may be provided so that it can be downloaded from an external server, or may be provided so that the program is started on an external computer and its functions are implemented on a client terminal (so-called cloud computing).
• a "unit” can also include, for example, hardware resources implemented by a circuit in the broad sense, and software information processing that can be specifically realized by these hardware resources.
• this embodiment handles various types of information, which can be represented, for example, by physical values of signal values representing voltage and current, high and low signal values as a binary bit collection consisting of 0 or 1, or quantum superposition (so-called quantum bits), and communication and calculations can be performed on a circuit in the broad sense.
• a circuit in the broad sense is a circuit that is realized by at least appropriately combining a circuit, circuitry, a processor, and memory.
• ASICs application specific integrated circuits
• SPLDs simple programmable logic devices
• CPLDs complex programmable logic devices
• FPGAs field programmable gate arrays
• FIG. 1 is a cross-sectional view showing an example of the structure of a memory element 10 according to this embodiment.
• the memory element 10 shown in FIG. 1 comprises a substrate 100, an electrode 102, an antiferromagnetic layer 104, a ferromagnetic layer 106, a barrier layer 108, a ferromagnetic layer 110, and an upper layer 112.
• the memory element 10 according to this embodiment is a so-called MTJ (Magnetic Tunnel Junction) element, which reads out data 1 or 0 based on the difference in tunnel magnetic resistance in the spin equilibrium and anti-equilibrium states due to the tunnel magnetoresistance effect.
• MTJ Magnetic Tunnel Junction
• a memory including the memory element 10 can be used as an MTJ element in, for example, MRAM (Magnetoresistive Random Access Memory), a magnetic head of a HDD (Hard Disk Drive), a racetrack memory, etc.
• the memory element 10 is expected to be used in, for example, STT (Spin Transfer Torque) type MRAM or SOT (Spin Orbit Torque) type MRAM, but may also be used in conventional Vertical MRAM.
• the substrate 100 is made of any material used for memory applications, such as Si.
• the electrode 102 is a layer made of an electrode material used for memory applications, such as W.
• the electrode 102 can be laminated on the substrate 100.
• the antiferromagnetic layer 104 is a layer made of an antiferromagnetic material.
• the antiferromagnetic material according to this embodiment is, for example, an antiferromagnetic material that exhibits an anomalous Hall effect.
• Such an antiferromagnetic material is, for example, an antiferromagnetic material in which an anomalous Hall effect is observed under conditions in which there is no magnetic field.
• Such an antiferromagnetic material is, for example, an antiferromagnetic material in which an anomalous Hall effect is observed at a temperature above room temperature.
• Such an antiferromagnetic material is, for example, an antiferromagnetic material that can take two values by rotating the spin.
• Such an antiferromagnetic material is, for example, a non-collinear antiferromagnetic material.
• Such an antiferromagnetic material may be made of, for example, one or more substances selected from the group consisting of Mn3Sn, Mn3Pt, Mn3Ge, Mn3Ga, and Mn3Ir.
• the non-collinear antiferromagnetic material is, for example, an Mn3X-based alloy such as Mn3Sn, Mn3Ge, or Mn3Ga. These alloys can easily rotate the spin by, for example, polarization by a magnetic octupole. As a result, the sign of the anomalous Hall coefficient of the antiferromagnetic material is reversible depending on the data written in the memory element 10.
• such an antiferromagnetic material may be, for example, a collinear antiferromagnetic material.
• the collinear antiferromagnetic material may be, for example, RuO2 or Mn5Si3.
• such an antiferromagnetic material may be an alloy that forms a cubic crystal, such as Mn3Pt, Mn3Ir, Mn3Rh, or MnPt.
• the antiferromagnetic layer 104 may be stacked on the electrode 102.
• the ferromagnetic layer 106 may be made of a ferromagnetic material used in a ferromagnetic MTJ element, such as Co, CoFeB, or CoFe.
• the ferromagnetic material may contain a magnetic element having a magnetic moment. Examples of such magnetic elements include Fe, Co, Ni, Nd, and Gd.
• the ferromagnetic layer 106 is a layer that functions as a free layer in the MTJ element.
• the material that constitutes the ferromagnetic layer 106 is not particularly limited as long as it functions as a free layer.
• the ferromagnetic layer 106 may be a single layer or a multilayer.
• the ferromagnetic layer 106 since the ferromagnetic layer 106 functions as a free layer, it may contain a magnetic material or a non-magnetic material other than the above-mentioned ferromagnetic material.
• the ferromagnetic layer 106 may be stacked on the antiferromagnetic layer 104.
• the antiferromagnetic layer 104 and the ferromagnetic layer 102 as the second ferromagnetic layer constitute the memory layer M.
• the ferromagnetic material contained in the ferromagnetic layer 102 as the second ferromagnetic layer corresponds to the second ferromagnetic material.
• the memory layer M is configured to include an antiferromagnetic material and a second ferromagnetic material having spontaneous magnetization.
• the memory layer M includes an antiferromagnetic layer 104 made of an antiferromagnetic material, and a ferromagnetic layer 102 as the second ferromagnetic layer made of a second ferromagnetic material. This configuration makes it possible to simplify the operation of the memory layer when writing data.
• An antiferromagnetic material e.g., a tilted antiferromagnetic material that exhibits the anomalous Hall effect and has spontaneous magnetization can reverse the direction of the spontaneous magnetization, for example, by applying an external magnetic field.
• a change in the direction of the spontaneous magnetization means a change in the magnetic structure in the antiferromagnetic material.
• Such a change in the magnetic structure causes a reversal of the sign of the anomalous Hall coefficient.
• a reversal of the sign of the anomalous Hall coefficient means a reversal of the direction of the effective magnetic field inside the antiferromagnetic material.
• Such a reversal of the effective magnetic field inside the antiferromagnetic material can induce a reversal of the spontaneous magnetization of the second ferromagnetic material through the magnetic coupling between the antiferromagnetic material (the antiferromagnetic layer 104 in this embodiment) and the second ferromagnetic material (the ferromagnetic layer 106 in this embodiment).
• the direction of the external magnetic field applied to the antiferromagnetic layer 104 differs depending on the data written to the memory element 10.
• the magnetization direction of the ferromagnetic material is configured to be reversible in conjunction with the sign of the anomalous Hall coefficient of the antiferromagnetic material depending on the data written to the memory element 10.
• the antiferromagnetic layer 104 may be configured to have an interface with the ferromagnetic layer 106. With this configuration, the magnetic coupling between the antiferromagnetic layer 104 and the ferromagnetic layer 106 forming the memory layer M can be strengthened, so that the interlocking between the reversal of the anomalous Hall coefficient of the antiferromagnetic layer 104 and the reversal of the magnetization direction of the ferromagnetic layer 106 can be enhanced.
• the ferromagnetic layer 106 may be stacked on the antiferromagnetic layer 104 without stacking other members such as an insulating film.
• At least a part of the ferromagnetic layer 106 may diffuse into the antiferromagnetic layer 104 by directly contacting the antiferromagnetic layer 104.
• the memory layer M may have a diffusion layer in which particles containing a magnetic element of the second ferromagnetic body are diffused in the antiferromagnetic layer near the interface. With this configuration, the magnetic coupling between the antiferromagnetic layer 104 and the ferromagnetic layer 106 forming the memory layer M can be further strengthened.
• the thickness of the antiferromagnetic layer 104 may be greater than the thickness of the ferromagnetic layer 106.
• the thickness refers to the length in the stacking direction in which each layer is stacked. Also, the thickness refers to the average value of the thickness within the plane. The thickness of a layer is also called the film thickness.
• the barrier layer 108 which is an example of a first insulating layer, is a non-magnetic insulating layer provided to realize TMR.
• the barrier layer 108 is not particularly limited as long as it functions as an insulating layer, and may be, for example, MgO, AlOx, TiOx, etc.
• the barrier layer 108 is laminated on the ferromagnetic layer 106.
• the ferromagnetic layer 110 may be a ferromagnetic material used in a ferromagnetic MTJ element, such as CoFeB or CoFe.
• the ferromagnetic layer 110 is a layer that functions as a fixed layer in the MTJ element.
• the material constituting the ferromagnetic layer 110 is not particularly limited as long as it functions as a fixed layer.
• the ferromagnetic layer 110 may be a single layer or a multilayer.
• the ferromagnetic layer 110 since the ferromagnetic layer 110 functions as a fixed layer, it may contain a magnetic material or a non-magnetic material other than the above-mentioned ferromagnetic material, such as a synthetic antiferromagnet (SAF).
• SAF synthetic antiferromagnet
• the ferromagnetic layer 110 which is an example of a first ferromagnetic layer, corresponds to the fixed layer F in the memory element 10. That is, the memory element 10 includes a fixed layer F and a memory layer M.
• the ferromagnetic material constituting the ferromagnetic layer 110 is an example of a first ferromagnetic material and has spontaneous magnetization.
• the magnetization direction of the ferromagnetic material constituting the ferromagnetic layer 110 is fixed regardless of the data written to the memory element 10. This allows the spontaneous magnetization directions of the ferromagnetic layers 106 and 110 to be changed to parallel or antiparallel by applying an external magnetic field according to the data to be written, thereby changing the tunnel current flowing through the memory element 10.
• This change in the tunnel current i.e., the change in tunnel magnetoresistance
• the memory element 10 can be formed using a smaller amount of antiferromagnetic material than when the entire memory layer is made of the antiferromagnetic material, and the decrease in the effective magnetic field of the entire memory layer can be suppressed while reducing the variation in the crystallinity of the antiferromagnetic material.
• the ferromagnetic layer 110 as the fixed layer F is stacked on the barrier layer 108.
• the barrier layer 108 is arranged between the fixed layer F and the memory layer M, thereby forming a tunnel junction between the fixed layer F and the memory layer M.
• the barrier layer 108 can be arranged between the ferromagnetic layer 110 and the ferromagnetic layer 106.
• the antiferromagnetic layer 104 is configured to be connected to the barrier layer 108 via the ferromagnetic layer 106. With this configuration, it is possible to obtain an antiferromagnetic layer 104 having crystallinity suitable for the structure of the ferromagnetic layer 106.
• the first ferromagnetic material and the second ferromagnetic material contain at least Co elements as particles having a magnetic moment, and more preferably are composed of Co or CoFeB.
• the upper layer 112 is a layer provided on top of the ferromagnetic layer 110.
• the upper layer 112 may be an electrode or a layer made of a material based on known technology for making the memory element 10 function more efficiently.
• the configuration of the upper layer 112 is not particularly limited.
• the upper layer 112 is, for example, stacked on the ferromagnetic layer 110.
• the spin magnetization direction of the antiferromagnetic layer 104, the ferromagnetic layer 106 and/or the ferromagnetic layer 110 is preferably perpendicular (i.e., stacking direction), but may be in-plane.
• FIG. 2 is a front view showing an example of the structure of a memory element 11 according to a first modified example of this embodiment.
• the memory element 11 shown in FIG. 2 may further include a first intermediate layer 105 in addition to the layers 100, 102, 104, 106, 108, 110, and 112 of the memory element 10 shown in FIG. 1.
• the first intermediate layer 105 is disposed between the antiferromagnetic layer 104 and the ferromagnetic layer 106.
• the antiferromagnetic layer 104, the first intermediate layer 105, and the ferromagnetic layer 106 constitute the memory layer M in the memory element 11. Therefore, the ferromagnetic layer 106 does not need to have an interface with the antiferromagnetic layer 104.
• the first intermediate layer 105 can, for example, suppress the diffusion of atoms contained in the antiferromagnetic layer 104 and the ferromagnetic layer 106 during heat treatment.
• the first intermediate layer 105 can also suppress an increase in surface roughness of the antiferromagnetic layer 104 due to heat treatment.
• the first intermediate layer 105 can also promote perpendicular magnetization of the layers above and below. Therefore, the memory layer M does not need to include a diffusion layer.
• the material constituting the first intermediate layer 105 may be, for example, Ta, Mo, Ru, or MgO.
• the material may also be a multilayer of Co/Pt or Ni/Co.
• the material may also be MnSnPt, Co, a CoFe/Ta layer, TbFeCo, Gd, etc.
• FIG. 3 is a diagram showing an example of the structure of a memory element 12 according to a second modified example of this embodiment.
• the memory element 12 shown in FIG. 3 may further include a second intermediate layer 107 in addition to the layers 100, 102, 104, 106, 108, 110, and 112 of the memory element 10 shown in FIG. 1.
• the second intermediate layer 107 may be disposed between the ferromagnetic layer 106 and the barrier layer 108.
• the second intermediate layer 107 may be, for example, a layer for making it easier to control the structure of the interface.
• the material constituting the second intermediate layer 107 may be, for example, Co, Fe, NdCo, Ru, Pd, Ir, etc.
• a known material known as an intermediate layer provided between a ferromagnetic layer and a barrier layer of a ferromagnetic MTJ element may be applied.
• the second intermediate layer 107 may be separate from the memory layer M or may be a part of the memory layer M.
• FIG. 4 is a front view showing an example of the structure of a memory element 13 according to a third modified example of this embodiment.
• the memory element 13 shown in FIG. 4 may further include a third intermediate layer 109 in addition to the layers 100, 102, 104, 106, 108, 110, and 112 of the memory element 10 shown in FIG. 1.
• the third intermediate layer 109 may be disposed between the barrier layer 108 and the ferromagnetic layer 110 in the memory element 10 shown in FIG. 1.
• the third intermediate layer 109 has the same effect as the second intermediate layer 107.
• the material constituting the third intermediate layer 109 is also the same as that of the second intermediate layer 107.
• FIG. 5 is a front view showing an example of the structure of a memory element 14 according to a fourth modified example of this embodiment.
• the memory element 14 shown in FIG. 5 further includes a first intermediate layer 105, a second intermediate layer 107, and a third intermediate layer 109 in addition to the layers 100, 102, 104, 106, 108, 110, and 112 of the memory element 10 shown in FIG. 1.
• These intermediate layers 105, 107, and 109 can be selectively inserted as appropriate.
• the specific aspects of each of these intermediate layers 105, 107, and 109 can be similar to those described above.
• the memory element 15 shown in FIG. 6 may include a ferromagnetic layer 1031, a fourth intermediate layer 1032, and a first intermediate layer 105 in addition to the layers 100, 102, 104, 106, 108, 110, and 112 of the memory element 10 shown in FIG. 1.
• the ferromagnetic layer 1031 is stacked on the electrode 102.
• the fourth intermediate layer 1032 is stacked on the electrode 102.
• the antiferromagnetic layer 104 is stacked on the fourth intermediate layer 1032.
• the first intermediate layer 105 is the same as the first intermediate layer 105 included in the memory element 11 shown in FIG. 2. Note that the fourth intermediate layer 1032 and the first intermediate layer 105 according to this modified example may or may not be provided.
• the ferromagnetic layer 1031 is composed of, for example, the same material as the ferromagnetic layer 106 or the ferromagnetic layer 110 described above. By providing the ferromagnetic layer 1031, polarization at the interface between the ferromagnetic layer 1031 and the antiferromagnetic layer 104 is possible, making it easier to maintain perpendicular magnetization in the antiferromagnetic layer 104. This improves the rotation efficiency (rotation speed) of the spin in the ferromagnetic layer 106 in perpendicular magnetization.
• the ferromagnetic layer 1031, the fourth intermediate layer 1032, the antiferromagnetic layer 104, the first intermediate layer 105, and the ferromagnetic layer 106 constitute the memory layer M in the memory element 15.
• the ferromagnetic layer 1031 corresponds to the third ferromagnetic layer, and the ferromagnetic material constituting the ferromagnetic layer 1031 corresponds to the third ferromagnetic material.
• the memory layer M may further include a third ferromagnetic layer composed of a third ferromagnetic material.
• the magnetization direction of the third ferromagnetic body can be configured to be reversible in conjunction with the sign of the anomalous Hall coefficient of the antiferromagnetic body according to the data written to the memory element 15.
• the third ferromagnetic layer can be configured to be coupled to the second ferromagnetic layer via the antiferromagnetic layer.
• the magnetic coupling between the ferromagnetic body and the antiferromagnetic body in the memory layer M can be further strengthened.
• the second intermediate layer 107 and the third intermediate layer 109 described above may or may not be provided.
• each layer of the memory element 15 is arbitrary.
• the thickness of the ferromagnetic layer 1031 may be, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2 nm, or may be within a range between any two of the values exemplified here.
• the thickness of the ferromagnetic layer 1031 may be 0.1 to 2 nm, preferably 0.3 to 1.5 nm, more preferably 0.4 to 1.3 nm, and more preferably 0.5 to 1.0 nm.
• An example of the thickness of the ferromagnetic layer 1031 is particularly preferable when a material containing Co, such as CoFeB, is used as the ferromagnetic material.
• the thickness of the fourth intermediate layer 1032 are 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and 1 nm, and may be within a range between any two of the numerical values exemplified here.
• the thickness of the fourth intermediate layer 1032 is 0.1 to 1 nm, preferably 0.1 to 0.8 nm, and more preferably 0.2 to 0.5 nm.
• the above example of the thickness of the fourth intermediate layer 1032 is particularly preferable when a material that has low reactivity with adjacent layers, such as MgO or Ta, is used as the material constituting the fourth intermediate layer 1032.
• the thickness of the antiferromagnetic layer 104 may be, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 nm, or may be within a range between any two of the values exemplified here.
• the thickness of the antiferromagnetic layer is 1 to 20 nm, preferably 2 to 18 nm, more preferably 3 to 16 nm, more preferably 4 to 14 nm, and more preferably 5 to 10 nm.
• This thickness of the antiferromagnetic layer 104 is preferable when a non-collinear antiferromagnetic material, such as an Mn3X-based material, more specifically, Mn3Si, is used as the antiferromagnetic material.
• the thickness of the first intermediate layer 105 are 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and 1 nm, and may be within a range between any two of the numerical values exemplified here.
• the thickness of the first intermediate layer 105 is 0.1 to 1 nm, preferably 0.1 to 0.8 nm, and more preferably 0.2 to 0.5 nm.
• the above example thickness of the first intermediate layer 105 is particularly preferred when the material constituting the first intermediate layer 105 is a material that has low reactivity with adjacent layers, such as MgO or Ta.
• the thickness of the ferromagnetic layer 106 may be, for example, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2 nm, or may be within a range between any two of the values exemplified here.
• the thickness of the ferromagnetic layer 106 may be 0.1 to 2 nm, preferably 0.3 to 1.5 nm, more preferably 0.4 to 1.3 nm, and more preferably 0.5 to 1.0 nm.
• the thickness of the ferromagnetic layer 106 is particularly preferred when a material containing Co, such as CoFeB, is used as the ferromagnetic material.
• the thickness of the antiferromagnetic layer 104 may be greater than the thickness of the ferromagnetic layer 106. This makes it easier to apply a magnetic field to the antiferromagnetic layer 104 while increasing the coupling to the spins of the ferromagnetic layer 106.
• the spin of the antiferromagnetic layer 104 is first reversed by passing a current in the stacking direction of the memory element 10 during writing. At that time, the spin of the ferromagnetic layer 106 is pulled and reversed due to magnetic coupling. This makes it possible to write memory 1s and 0s.
• the spin reversal in the antiferromagnetic layer 104 is prioritized, so that the spin can be reversed at a speed faster than the spin reversal of the conventional ferromagnetic layer.
• SOT-MRAM where the spin reversal occurs first in the antiferromagnetic layer 104, which can reverse the spin of the ferromagnetic layer 106 via magnetic coupling.
• MRAM in which the spin is reversed by an external magnetic field.
• FIG. 7 is a diagram showing a configuration example of a memory element 20 including another example of the memory layer M.
• the memory element 20 may include a substrate 200, an electrode 202, a memory layer M, a barrier layer 214, a fixed layer F, and an upper layer 216.
• the specific configuration of the substrate 200 is similar to that of the substrate 100 described above.
• the electrode 202 is laminated on the substrate 200.
• the specific configuration of the electrode 202 is similar to that of the electrode 102.
• the memory layer M is stacked on the electrode 202.
• the memory layer M is configured to be able to change its magnetic state relative to the fixed layer F.
• the memory layer M in this embodiment includes a diffusion layer 204.
• the diffusion layer 204 is configured so that particles having a magnetic moment contained in a ferromagnetic material are diffused into an antiferromagnetic material that exhibits an anomalous Hall effect. With this configuration, a memory layer having a more compact and stronger magnetic moment can be formed.
• Such an antiferromagnetic material is, for example, an antiferromagnetic material in which an anomalous Hall effect is observed under conditions in which there is no magnetic field.
• Such an antiferromagnetic material is, for example, an antiferromagnetic material in which an anomalous Hall effect is observed at a temperature above room temperature.
• Such an antiferromagnetic material is, for example, an antiferromagnetic material that can take two values by spin rotation.
• Such an antiferromagnetic material is, for example, a non-collinear antiferromagnetic material.
• the antiferromagnetic material may be composed of one or more substances selected from the group consisting of Mn3Sn, Mn3Pt, Mn3Ge, Mn3Ga, and Mn3Ir.
• the non-collinear antiferromagnetic material may be, for example, an Mn3X-based alloy such as Mn3Sn, Mn3Ge, or Mn3Ga. These alloys can easily rotate spins, for example, by polarization by a magnetic octupole.
• the antiferromagnetic material may also be, for example, a collinear antiferromagnetic material.
• the collinear antiferromagnetic material may be, for example, RuO2 or Mn5Si3.
• such antiferromagnetic material may be an alloy that forms a cubic crystal, such as Mn3Pt, Mn3Ir, Mn3Rh, or MnPt.
• the ferromagnetic material diffusing into the antiferromagnetic material in the diffusion layer 204 may be composed of a ferromagnetic material used in a ferromagnetic MTJ element, such as Co, CoFeB, CoFe, etc., as in the above-mentioned ferromagnetic layer 106.
• the ferromagnetic material may contain a magnetic element having a magnetic moment. Examples of such magnetic elements include Fe, Co, Ni, Nd, Gd, etc. In particular, Co is preferable as such a magnetic element.
• the diffusion layer 204 is configured, for example, so that magnetic ions Y such as Fe, Co, Ni, Gd, Nd, etc.
• the diffusion layer 204 is preferably made of one or more materials selected from the group consisting of Mn3Si(Co), Mn3Pt(Co), Mn3Ge(Co), Mn3(Co), and Mn3Ir(Co). It is particularly preferable that the diffusion layer 204 is made of Mn3Si(Co).
• the diffusion layer 204 may be formed by stacking layers by, for example, a molecular beam epitaxy method.
• the diffusion layer 204 may also be obtained by sputtering a small amount of ferromagnetic material on an antiferromagnetic material and diffusing the element contained in the ferromagnetic material into the antiferromagnetic material by heat treatment.
• the second ferromagnetic material may contain a magnetic element having a magnetic moment
• the memory layer M may be configured such that at least the magnetic element of the second ferromagnetic material (e.g., a ferromagnetic element such as Co) is dispersed in the antiferromagnetic material.
• the second ferromagnetic material is not limited to a material configured such that the ferromagnetic layer 106 and the antiferromagnetic layer 104 can be separated as layers, as described in the memory elements 10 to 15.
• the second ferromagnetic material may be formed such that the ferromagnetic element (e.g., Co) is dispersed in the antiferromagnetic material (e.g., Mn 3 Sn) of the antiferromagnetic layer 104.
• Co elements which are an example of the magnetic elements of the second ferromagnetic material, may be dispersed in the antiferromagnetic layer 104 so as to be doped, or may be dispersed so as to substitute for Mn elements in the antiferromagnetic material, or the second ferromagnetic material and the antiferromagnetic material may form an alloy, a solid solution, or a eutectic.
• the memory layer M may be configured so that the second ferromagnetic material and the antiferromagnetic material form an inseparable integrated phase.
• the barrier layer 206 which serves as the first insulating layer, is a non-magnetic insulating layer provided to realize TMR.
• the barrier layer 108 is not particularly limited as long as it functions as an insulating layer, and may be, for example, MgO, AlOx, TiOx, etc.
• the ferromagnetic layer 208 corresponds to the first ferromagnetic layer and functions as the fixed layer F.
• the ferromagnetic layer 208 is stacked on the barrier layer 206.
• the specific configuration of the ferromagnetic layer 208 is similar to that of the ferromagnetic layer 110 described above.
• the upper layer 210 is a layer provided on top of the ferromagnetic layer 208.
• the upper layer 210 may be an electrode or a layer made of a material based on a known technology for making the memory element 20 function more efficiently.
• the configuration of the upper layer 210 is not particularly limited.
• the upper layer 210 is, for example, stacked on the ferromagnetic layer 208.
• a memory element comprising a fixed layer and a storage layer, the fixed layer being composed of a first ferromagnetic material having spontaneous magnetization, the magnetization direction of the first ferromagnetic material being configured to be fixed regardless of data written to the memory element, the storage layer being composed of an antiferromagnetic material and a second ferromagnetic material having spontaneous magnetization, the antiferromagnetic material exhibiting an anomalous Hall effect, the sign of the anomalous Hall coefficient of the antiferromagnetic material being configured to be reversible depending on data written to the memory element, and the magnetization direction of the second ferromagnetic material being configured to be reversible in conjunction with the sign of the anomalous Hall coefficient of the antiferromagnetic material depending on data written to the memory element.
• a memory element can be formed using a smaller amount of antiferromagnetic material than when the entire memory layer is made of the antiferromagnetic material, which reduces the variation in the crystallinity of the antiferromagnetic material while suppressing a decrease in the effective magnetic field of the entire memory layer.
• This configuration makes it possible to simplify operations on the memory layer when writing data.
• a memory element according to (2) above further comprising a first insulating layer, the first insulating layer being disposed between the fixed layer and the memory layer, thereby forming a tunnel junction between the fixed layer and the memory layer, and the antiferromagnetic layer being configured to be connected to the first insulating layer via the second ferromagnetic layer.
• This configuration makes it possible to obtain an antiferromagnetic layer with crystallinity suited to the structure of the second ferromagnetic layer.
• This configuration strengthens the magnetic coupling between the antiferromagnetic layer and the second ferromagnetic layer that form the memory layer, thereby improving the linkage between the reversal of the anomalous Hall coefficient of the antiferromagnetic layer and the reversal of the magnetization direction of the second ferromagnetic layer.
• This configuration can further strengthen the magnetic coupling between the antiferromagnetic layer and the second ferromagnetic layer that form the memory layer.
• a memory element according to any one of (2) to (5) above, wherein the second ferromagnetic body includes a magnetic element having a magnetic moment, and the memory layer is configured such that at least the magnetic element is dispersed in the antiferromagnetic body.
• a memory element according to any one of (2) to (6) above, wherein the storage layer further comprises a third ferromagnetic layer made of a third ferromagnetic material, the magnetization direction of the third ferromagnetic material is configured to be reversible in conjunction with the sign of the anomalous Hall coefficient of the antiferromagnetic material depending on the data written to the memory element, and the third ferromagnetic layer is configured to be coupled to the second ferromagnetic layer via the antiferromagnetic layer.
• This configuration can further strengthen the magnetic coupling between the ferromagnetic material and the antiferromagnetic material in the memory layer.
• a memory element according to any one of (2) to (7) above, wherein the thickness of the antiferromagnetic layer is greater than the thickness of the second ferromagnetic layer.
• This configuration makes it easy to apply a magnetic field to the antiferromagnetic layer while improving the coupling to the spin of the second ferromagnetic layer.
• a memory element according to any one of (1) to (8) above, wherein the particles having a magnetic moment contained in the second ferromagnetic material are configured to diffuse into the antiferromagnetic material.
• This configuration makes it possible to form a memory layer that is more compact and has a stronger magnetic moment.
• 10 memory element, 11: memory element, 12: memory element, 13: memory element, 14: memory element, 15: memory element, 20: memory element, 100: substrate, 102: electrode, 102: ferromagnetic layer, 104: antiferromagnetic layer, 105: first intermediate layer, 106: ferromagnetic layer, 107: second intermediate layer, 108: barrier layer, 108: ferromagnetic layer, 109: third intermediate layer, 110: ferromagnetic layer, 112: upper layer, 200: substrate, 202: electrode, 204: diffusion layer, 206: barrier layer, 208: ferromagnetic layer, 210: upper layer, 214: barrier layer, 216: upper layer, 1031: ferromagnetic layer, 1032: fourth intermediate layer, F: fixed layer, M: memory layer

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• 2024
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