JP2022059441A - Magnetic memory element and magnetic memory device - Google Patents

Abstract

To provide a high-density, high-capacity, high-reliability magnetic device having a function of a shift register for writing information, moving the information with current, and reading the information by using magnetic tunnel junction (MTJ), a function of a high-capacity non-volatile memory represented by a NAND FLASH memory, and a function of a next-generation VNAND memory.SOLUTION: A magnetic memory element 101 comprises: a spin-orbit torque (SOT) generation source 111 that generates a spin-orbit torque; and a magnetic thin wire 114 whose one end is connected with a principal surface of the SOT generation source 111. The magnetic memory element stores information by using both the spin-orbit torque generated in the SOT generation source 111 and a current flowing in the magnetic thin wire 114. Directions of magnetization that are information are parallel to an extending direction of the magnetic thin wire 114.SELECTED DRAWING: Figure 1

Description

The present invention relates to a magnetic memory element and a magnetic memory device, and is a high-density, large-capacity, high-reliability racetrack-type magnetic memory element having the functions of, for example, a shift register and a next-generation VN NAND memory used as a large-capacity non-volatile memory. And magnetic memory devices.

The recording capacity of large-capacity non-volatile memory represented by NAND Flash memory is increasing due to the development of three-dimensional technology. However, since semiconductor memory records information depending on the presence or absence of electric charge in the memory cell, it takes time to physically move electrons.

On the other hand, the magnetic memory can essentially record in a short time within several tens of picoseconds. As far as pure recording time is concerned, magnetic memory is 10 to 20 times faster than semiconductor memory. In recent years, a domain wall drive phenomenon (domain wall current drive phenomenon) by applying a current has been found in a one-dimensional structure called a magnetic fine wire, which is made by processing a magnetic material into a linear shape of several hundred nanometers. Then, it has been attempted to electrically access the magnetization information by using this phenomenon.

Further, as described in Non-Patent Document 1, the racetrack memory is an original memory having a U-shaped three-dimensional structure in which a magnetic thin wire is stretched in a direction perpendicular to a substrate. In this memory, a write head creates a magnetic domain in a magnetic wire, and a pulse current is applied in the left-right direction to read information and move it to the head. If the information you want to read is at the end, it will take some time, but it also has a random access function. Data is read out by the MTJ element.

Racetrack memory S.S.P Parkin, M. Hayashi, and L. Thomas, Science, vol. 320 pp.190-194 (2008).

However, shift registers that write information, move information by current, and read information using a magnetic tunnel junction (MTJ), large-capacity non-volatile memory represented by NAND FLASH memory, and next-generation VN NAND memory. There is a demand for a magnetic device with higher density, higher capacity, and higher reliability.

The magnetic memory element of one embodiment includes a SOT generation source that generates a spin-orbit torque (SOT), and a magnetic thin wire that connects to the main surface of the SOT generation source at one end. The direction of the spin-orbit torque generated at the SOT generation source is perpendicular to the direction in which the magnetic wire is stretched.

According to the magnetic memory element of one embodiment, as a shift register that writes information, moves information by an electric current, and reads information using MTJ, a large-capacity non-volatile memory represented by a NAND FLASH memory, and a next-generation V NAND memory. It is possible to provide a high-density, large-capacity, high-reliability magnetic device having the above functions.

The magnetic memory element of one embodiment may include an insulating layer laminated on the other end of the magnetic wire and a fixed layer laminated on the insulating layer.

According to the magnetic memory element of one embodiment, information can be read out by a tunnel magnetoresistive element (TMR element).

The magnetic memory element of one embodiment may include a non-magnetic metal layer laminated on the other end of the magnetic wire and a fixed layer laminated on the non-magnetic metal layer.

According to the magnetic memory element of one embodiment, information can be read out by a giant magnetoresistive element (GMR element).

The magnetic memory element of one embodiment is connected to the fixed layer with a first electrode and a second electrode that allow a current to flow to the SOT generation source in a direction perpendicular to the direction of the spin orbit torque, and a current is applied to the magnetic thin wire. A third electrode for flowing may be provided.

According to the magnetic memory element of one embodiment, a plurality of pieces of information can be written and moved on the magnetic thin wire.

The magnetic memory device of one embodiment is provided with a controller for passing a current between the magnetic memory element and the first electrode and the second electrode in a direction corresponding to the information to be written.

According to the magnetic memory device of one embodiment, information can be written to a magnetic wire as magnetization.

In the magnetic memory device of one embodiment, the controller may pass a current for moving a magnetic domain in the magnetic wire between the first electrode and the third electrode.

According to the magnetic memory device of one embodiment, a plurality of pieces of information can be stored and moved in a magnetic wire.

According to the magnetic memory element and the magnetic memory device of the present invention, a shift register that writes information, moves information by electric current, and reads information using MTJ, a large-capacity non-volatile memory represented by NANDFLASH memory, and next-generation It is possible to provide a high-density, large-capacity, high-reliability magnetic device having a function as a VN NAND memory.

It is a figure of the magnetic memory apparatus which concerns on Embodiment 1. FIG. It is a figure explaining the operation of the magnetic memory apparatus which concerns on Embodiment 1. FIG. It is a figure explaining the operation of the magnetic memory apparatus which concerns on Embodiment 1. FIG. It is a figure explaining the operation of the magnetic memory apparatus which concerns on Embodiment 1. FIG. It is a figure explaining the operation of the magnetic memory apparatus which concerns on Embodiment 1. FIG. It is a figure explaining the operation of the magnetic memory apparatus which concerns on Embodiment 1. FIG. It is a figure explaining the operation of the magnetic memory apparatus which concerns on Embodiment 1. FIG. It is a figure which shows an example of the calculation result using LLG. It is a figure which shows an example of the calculation result using LLG. It is a figure which shows an example of the calculation result using LLG. It is a figure which shows an example of the calculation result using LLG. It is a figure which shows an example of the calculation result using LLG. It is a figure which shows an example of the calculation result using LLG. It is a figure which shows an example of the calculation result using LLG.

Embodiment 1
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram of a magnetic memory device according to the first embodiment. In FIG. 1, the structure of the magnetic memory element is shown in a perspective view, and the circuit connected to the magnetic memory element is shown in a schematic diagram.

In FIG. 1, the magnetic memory device 100 includes a magnetic memory element 101 and a controller 102. The magnetic memory element 101 includes a SOT generation source 111, a first electrode 112, a second electrode 113, a magnetic wire 114, an insulating layer 115, a fixed layer 116, and a third electrode 117. As shown in FIG. 1, the SOT generation source 111, the magnetic thin wire 114, the insulating layer 115, and the fixed layer 116 are laminated in this order.

The SOT generation source 111 is an electrode that generates spin-orbit torque. The SOT generation source 111 connects the magnetic thin wire 114 in a direction substantially perpendicular to the main surface. Further, the SOT generation source 111 generates spin-orbit torque in a direction substantially perpendicular to the main surface. Then, the SOT generation source 111 generates a spin-orbit torque in the lower part (114b) of the magnetic thin wire 114. The direction of magnetization written in the magnetic wire 114 by the spin-orbit torque generated from the SOT generation source 111 in the lower part (114b) of the magnetic wire 114 and the current flowing through the magnetic wire 114 is the information to be stored. In FIG. 1, the direction of the spin-orbit torque is the Y-axis direction, which changes the direction of magnetization of the lower part (114b) of the magnetic wire 114. That is, the direction of the spin-orbit torque generated by the SOT generation source 111 and the direction of the magnetization written on the magnetic wire 114 (information to be rewritten) are perpendicular to each other, and the direction of the magnetization and the direction in which the magnetic wire 114 is stretched are parallel. In FIG. 1, the lower portion 114b of the magnetic fine wire 114 is described with a diameter different from that of the magnetic fine wire 114, but the diameter of the lower portion 114b may be different from or the same as that of the magnetic fine wire 114.

Specifically, the SOT generation source 111 can generate spin-orbit torque by passing a current between the first electrode 112 and the second electrode 113. The SOT source 111 is generally a non-magnetic metal. For example, the SOT source 111 may include a topological insulator. A topological insulator is a substance that conducts electricity on the surface while the inside of the substance is an insulator. For example, topological insulators include semimetal bismuths and bismuth compounds. In particular, BiTeSb or BiSb is suitable as a topological insulator. Further, the topological insulator may have a conductive inside by changing the composition. Further, the SOT generation source 111 may contain at least one metal of Rh, Pt, W and Ta.

Further, the SOT generation source 111 can also be a combination of Ti and a magnetic material such as the ferromagnet NiFe or CoFeB. (S. C. Baek et al., Nat. Mater. 17 (2018) 509)

The first electrode 112 is an electrode connected to one end of the SOT generation source 111. The second electrode 113 is an electrode connected to the other end of the SOT generation source 111. Further, the first electrode 112 and the second electrode 113 are connected to the controller 102 by electrical wiring.

The magnetic thin wire 114 is a magnetic material having magnetic anisotropy. The thin magnetic wire 114 is connected to the SOT generation source 111 at one end and to the insulating layer 115 at the other end. In FIG. 1, the magnetic thin wire 114 is a thin wire extending in the Z-axis direction. That is, the stretching direction of the magnetic wire 114 is perpendicular to the direction of the spin-orbit torque generated by the SOT generation source 111, and is parallel to the direction of magnetization.

Further, the magnetic thin wire 114 is preferably a Pillar type magnetic fine wire. Further, it is desirable that the magnetic thin wire 114 is a ferromagnetic metal. The magnetic thin wire 114 is a magnetic thin wire formed as an elongated magnetic material. Then, a current flows through the magnetic wire 114, and the domain wall (the boundary of the section facing a certain magnetization direction) moves, which functions as a domain wall moving memory. Specifically, a current is passed through the magnetic wire 114 to generate a spin transfer torque (STT). Further, a current is passed through the SOT generation source 111 arranged under the end of the magnetic thin wire 114 to generate SOT in the lower part (114b) of the magnetic thin wire 114. By using this STT and SOT together, the domain wall and magnetic domain are recorded in the magnetic wire 114.

For example, the magnetic thin wire 114 includes a Co / Ni multilayer film, a CoNi alloy, a Co / Pd multilayer film, a CoPd alloy, a Co / Pt multilayer film, a CoPt alloy, a Tb / FeCo multilayer film, a TbFeCo alloy, a CoFe alloy, and a CoFeB alloy. It is preferably composed of a Fe / Ni multilayer film or a FeNi alloy.

The magnetic thin wire 114 can take a wide variety of shapes. The magnetic thin wire 114 shown in FIG. 1 is a magnetic thin wire formed as an elongated magnetic material, and extends on a straight line (here, the Z axis). The cross section of the magnetic thin wire 114 can take a wide variety of cross-sectional shapes. For example, the cross section of the magnetic thin wire 114 may have a circular shape or a square shape.

The insulating layer 115 is structurally connected to the magnetic thin wire 114 at one end. The insulating layer 115 is a non-magnetic insulator. For example, the insulating layer 115 is a layer containing an insulating substance as a main component. The insulating layer 115 is made of an insulating film such as MgO. As the material constituting the insulating layer 115, an oxide having a NaCl structure is preferable, and in addition to the above-mentioned MgO, CaO, SrO, TiO, VO, NbO and the like can be mentioned, but the function as the insulating layer 115 is hindered. It is not particularly limited as long as it does not cause a problem. As the material, for example, spinel type MgAl ₂ O ₄ or the like may be used. In the first embodiment, the MR element is composed of the magnetic thin wire 114, the insulating layer 115, and the fixed layer 116, but the GMR element may be composed of a metal such as Cu instead of the insulating layer 115.

The fixed layer 116 is a ferromagnet having vertical magnetic anisotropy. That is, the fixed layer 116 is a layer having magnetic anisotropy parallel to the stretching direction of the magnetic thin wire 114. Further, the fixed layer 116 is structurally connected to the insulating layer 115 at one end. Further, the fixed layer 116 is connected to the third electrode 117 at the other end. The fixed layer 116 is a ferromagnetic metal layer in which the direction of magnetization is fixed. For example, the fixed layer 116 may be composed of an Fe-based material such as CoFeB or CoFe, a Co / Pt multilayer film, or a composite thereof. These magnetic thin wires 114, the insulating layer 115, and the fixed layer 116 constitute a TMR element.

The third electrode 117 is an electrode connected to the fixed layer 116. Further, the third electrode 117 is connected to the controller 102 by electrical wiring.

The controller 102 writes and reads information from the magnetic memory element 101. Further, the controller 102 moves information in the magnetic thin wire 114. These operations are realized by the controller 102 applying a voltage or passing a current between the first electrode 112, the second electrode 113, and the third electrode 117.

The controller 102 changes the direction of the current flowing between the first electrode 112 and the second electrode 113 according to the information to be written. For example, when writing the binary number 0 to the magnetic memory element 101, the controller 102 causes a current to flow from the first electrode 112 to the second electrode 113. Alternatively, when writing the binary number 1 to the magnetic memory element 101, the controller 102 causes a current to flow from the second electrode 113 to the first electrode 112. The binary value and the direction of the current may be reversed.

Further, the controller 102 applies a constant voltage between the first electrode 112 and the third electrode 117, measures the current value flowing between the third electrode 117 and the first electrode 112, and magnetizes the magnetic thin wire 114. Read the orientation (ie the value of the written information).

Further, the controller 102 passes a constant current (sense current) between the first electrode 112 and the third electrode 117, and measures the voltage (potential difference) between the first electrode 112 and the third electrode 117. The direction of magnetization of the magnetic wire 114 (that is, the value of the written information) may be read out.

With the above configuration, the magnetic memory device 100 writes and reads data. Next, an operation in which the controller 102 writes information to the magnetic memory element 101 and an operation in which the controller 102 moves information in the magnetic wire 114 will be described. 2 to 6 are diagrams illustrating the operation of the magnetic memory device according to the first embodiment.

FIG. 2 describes the start of information writing in the first bit. In FIG. 2, the controller 102 passes a current J ₂ in the direction corresponding to the information of the first bit between the first electrode 112 and the second electrode 113, so that the lower part of the magnetic wire 114 (114b) from the SOT generation source 111. ), A spin-orbit torque in the Y-axis direction is generated. In the example of FIG. 2, a current J ₂ flows from the second electrode 113 to the first electrode 112, and a domain wall is generated in the lower part (114b) of the magnetic wire 114.

Further, when the controller 102 passes a current J1 from the third electrode 117 to the _first electrode 112, the generated domain wall moves upward on the magnetic wire 114. FIG. 3 shows a state in which the writing of the information of the first bit is completed. As shown in FIG. 3, the downward magnetization M1 is written on the magnetic thin wire 114 with a length of _one bit.

Next, in FIG. 4, the start of information writing in the second bit will be described. In FIG. 4, the controller 102 causes the current J2 in the direction corresponding to the information of the _second bit to flow between the first electrode 112 and the second electrode 113, so that the lower part of the magnetic wire 114 (114b) from the SOT generation source 111. ), The spin-orbit torque is generated. In FIG. 4, a current J ₂ flows from the first electrode 112 to the second electrode 113, a spin-orbit torque opposite to the explanation in FIG. 2 is generated, and a domain wall is generated in the lower part (114b) of the magnetic wire 114. There is.

Further, when the controller 102 passes a current J ₁ from the third electrode 117 to the first electrode 112, the magnetization M ₁ corresponding to the information of the first bit moves to the third electrode 117 side, and the generated domain wall is generated. Moves to the magnetic wire 114. In FIG. 5, the downward magnetization M ₁ of the first bit moves inside the magnetic wire 114 toward the third electrode 117, and the upward magnetization M ₂ of the second bit moves inside the magnetic wire 114.

As described above, the controller 102 writes information to the magnetic memory element 101, and further moves the information in the magnetic wire 114.

Next, an operation in which the controller 102 reads information from the magnetic memory element 101 and an operation in which the controller 102 moves information in the magnetic wire 114 will be described. FIG. 7 is a diagram illustrating the operation of the magnetic memory device according to the first embodiment.

As shown in FIG. 7, the controller 102 applies a constant voltage between the first electrode 112 and the third electrode 117, and measures the current value J3 flowing between the _third electrode 117 and the first electrode 112. Thereby, the direction of magnetization of the upper end of the magnetic wire 114 (that is, the value of the information written on the top (115 side) of the magnetic wire 114) is read out.

Further, the controller 102 passes a constant current between the first electrode 112 and the third electrode 117, and measures the voltage (potential difference) between the first electrode 112 and the third electrode 117 to measure the magnetic wire 114. The direction of magnetization at the upper end (that is, the value of the information written at the top (115 side) of the magnetic wire 114) may be read out. Then, the controller 102 reads out the second information by moving the magnetization of the magnetic wire 114 upward with a constant current and moving the second information from the top to the top. Similarly, the third and fourth information is read out in sequence.

At the time of reading, the controller 102 does not pass a current (or does not apply a voltage) between the first electrode 112 and the second electrode 113.

In this way, the magnetic memory device 100 uses STT and SOT in combination to move the domain wall (the boundary of the section facing a certain magnetization direction). The magnetic fine wire 114 functions as a domain wall movable memory.

Next, we investigated the possibility that the recording capacity of the magnetic device of the present invention is equal to or greater than that of the next-generation VNAND. In a micromagnetic simulation (LLG) based on the Landau-Lifshits-Gilbert equation, the length of the magnetic wire is 200 nm and the width is 10 nm, and the striped magnetic domain structure in which 10-bit information is magnetized in a plane is the initial state. Created. Micromagnetics simulation was performed with magnetic parameters of saturation magnetization (Ms): 300 kA / m, exchange stiffness constant: 1.0 pJ / m, vertical magnetic anisotropy: 100 kJ / m ³ , and DMI constant 0.015 mJ / m ² . However, the state became stable while maintaining the number of bits in the initial state. Therefore, 500 bits of information can be stored in a magnetic wire with a length of 10 μm. This storage capacity is 10 μm in height, 150 nm in diameter, and is equivalent to 1 to 2 times the recording capacity of 96-layer VN NAND.

In addition, a computer experiment was conducted using an LLG assuming permalloy (FeNi alloy) for the operation of the magnetic memory element 101 shown in FIG. The results are shown in FIGS. 8 to 14. 8 to 14 are diagrams showing an example of a calculation result using LLG.

As shown in FIGS. 8 to 10, the spin-orbit torque generated from the SOT generation source 111 (omitted in the figure) changes the magnetization direction of the lower portion (114b) of the magnetic wire 114 to form a domain wall. Then, as shown in FIGS. 10 to 11, the domain wall moves on the magnetic wire 114. Similarly, as shown in FIGS. 12 to 14, the domain wall moves on the magnetic wire 114. In this way, it can be seen that data can be written and moved by generating SOT on the lower portion 114b of the magnetic thin wire 114 and passing a current through the magnetic thin wire 114.

When the conventional race track structure and thin wire are used, it is necessary to provide an electrode for data movement, a recording thin wire for data recording, an MTJ element for reading, and the like. However, the magnetic memory of the first embodiment is provided. According to the device, data can be written, moved and read by the three-terminal structure.

Further, according to the magnetic memory device of the first embodiment, a shift register that writes information by using SOT wiring and a Pillar type magnetic thin wire, moves the information by an electric current, and reads the information by using an MTJ, and a NAND FLASH memory. It is possible to provide a high-density, large-capacity, high-reliability magnetic device having a function as a large-capacity non-volatile memory represented by the above and a next-generation VN NAND memory.

The present invention is not limited to the above embodiment, and can be appropriately modified without departing from the spirit. For example, in the above embodiment, the example in which the magnetic thin wire 114, the insulating layer 115, and the fixed layer 116 constitute a TMR element has been described, but a non-magnetic metal layer may be laminated instead of the insulating layer 115 to form a GMR element. ..

Further, in the above embodiment, the magnetic fine wires 114 and 114b, the insulating layer 115 and the fixed layer 116 are represented by a cylindrical shape in FIG. 1, but any of them may be used as long as they are laminated. For example, the rectangular parallelepiped shapes may be laminated.

100 Magnetic memory device 101 Magnetic memory element 102 Controller 111 SOT source 112 First electrode 113 Second electrode 114 Magnetic thin wire 115 Insulation layer 116 Fixed layer 117 Third electrode 114b Lower part of magnetic thin wire 114

Claims (6)

SOT generation source that generates spin-orbit torque and
At one end, it is equipped with a magnetic thin wire that connects to the main surface of the SOT generation source.
A magnetic memory element in which the direction of the spin-orbit torque generated in the SOT generation source is perpendicular to the direction in which the magnetic fine wire is stretched, and the magnetic domain in the magnetic fine wire and the direction in which the magnetic fine wire is stretched are parallel. The first electrode and the second electrode, which allow a current to flow through the SOT generation source in a direction perpendicular to the direction of the spin-orbit torque,
The magnetic memory element according to claim 1, further comprising a third electrode connected to the fixed layer and allowing a current to flow through a magnetic thin wire. The insulating layer laminated on the other end of the magnetic thin wire and
The magnetic memory element according to claim 2, further comprising a fixed layer laminated on the insulating layer. A non-magnetic metal layer laminated on the other end of the thin magnetic wire,
The magnetic memory element according to claim 2, further comprising a fixed layer laminated on the non-magnetic metal layer. The magnetic memory element according to claim 3 or 4,
A magnetic memory device including a controller for passing a current between the first electrode and the second electrode in a direction corresponding to the information to be written. The magnetic memory device according to claim 5, wherein the controller flows a current for moving a magnetic domain in the magnetic wire between the first electrode and the third electrode.

Images