Magnetic shift register

Abstract

This magnetic shift register comprises a plurality of magnetic shift register units, a writing unit, and a reading unit. Each of the plurality of magnetic shift register units includes a magnetic material layer extending in a specific direction. The writing unit electrically connects the plurality of magnetic shift register units in series. A pulse current corresponding to serial data flows through the writing unit and as a result, spin information is transferred to the magnetic material layers. The spin information is buffered in the plurality of magnetic shift register units by means of magnetic domain wall motion that accompanies a shift current flowing in the specific direction. The reading unit is able to read the spin information buffered in the plurality of magnetic shift register units. The electrical resistances at either end of the plurality of magnetic shift register units in the specific direction are different from one another.

Description

Magnetic Shift Register

[0001] The present invention relates to a magnetic shift register.

[0002] Registers and memories that utilize domain wall motion are known.

[0003] For example, Patent Document 1 describes a photonic spin register. This photonic spin register includes a shift register section and a write section. The shift register section has a magnetic layer extending in one direction. The write section writes spin information by transferring information contained in a pulse-amplitude-modulated optical signal input in series to the spin state of the magnetic domains in the magnetic layer by a photocurrent corresponding to the optical signal or by irradiation with the optical signal. When a shift current flows in one direction through the shift register section, domain walls move within the magnetic layer, causing the spin information to move and be buffered in the magnetic layer.

[0004] Patent Document 1 also describes a photonic spin register having multiple shift register units (see FIG. 7 of Patent Document 1). In this photonic spin register, a control unit selects one of the multiple shift register units to which a shift current flows.

[0005] Patent Document 2 describes a domain wall motion memory. One example of this domain wall motion memory is one in which multiple magnetic memory wires can be written to using a single write magnetic wire (see FIG. 13 of Patent Document 2). In this example, a selection transistor is connected to one end of each magnetic memory wire, and data is simultaneously written to all magnetic memory wires that intersect with the write magnetic wire and have corresponding pinned portions. In unselected magnetic memory wires, the written bit is moved in advance from the position where it intersects with the write magnetic wire to prevent overwriting of the already written bit. Meanwhile, in the selected magnetic memory wire, a current pulse is passed through the write magnetic wire, and then a shift current is passed through the magnetic memory wire via the selection transistor, and the written bit is transferred.

[0006] International Publication No. 2022 / 158545 Japanese Patent Application Laid-Open No. 2015-60971

[0007] In the photonic spin register described in Patent Document 1, a control unit selects one of multiple shift register units to pass a shift current through. In the magnetic memory wire selected in the domain wall motion memory described in Patent Document 2, a current pulse is passed through the write magnetic wire, and then a shift current is passed through the magnetic memory wire via a selection transistor.

[0008] The techniques described in Patent Documents 1 and 2 require elements such as transistors to control the shift currents to the multiple shift register units and the multiple magnetic memory wires, which increases the number of transistors required, which is not advantageous from the perspective of reducing power consumption.

[0009] In view of the above circumstances, the present invention provides a magnetic shift register that is advantageous from the viewpoint of reducing power consumption.

[0010] The present invention provides a magnetic shift register comprising: a plurality of magnetic shift register units, each including a magnetic layer extending in a specific direction; a write unit electrically connecting the plurality of magnetic shift register units in series along a direction perpendicular to the specific direction and the thickness direction of the magnetic layer; and a read unit attached to each of the plurality of magnetic shift register units, wherein spin information corresponding to each bit of serial data is transferred to the magnetic layer of the plurality of magnetic shift register units by causing a pulse current corresponding to serial data to flow through the write unit, and the spin information is buffered in the plurality of magnetic shift register units by domain wall motion caused by the shift current flowing in the specific direction in the plurality of magnetic shift register units, and the read unit is capable of reading out the spin information buffered in the plurality of magnetic shift register units, and the plurality of magnetic shift register units have different electrical resistances at both ends in the specific direction.

[0011] The above magnetic shift register is advantageous from the viewpoint of reducing power consumption.

[0012] FIG. 1 is a diagram schematically illustrating an example of a magnetic shift register. FIG. 2 is a cross-sectional view schematically illustrating an example of a magnetic shift register unit. FIG. 3 is a diagram schematically illustrating changes in spin information buffered in the magnetic shift register. FIG. 4 is a diagram schematically illustrating another example of a magnetic shift register. FIG. 5 is a diagram showing another example of a magnetic shift register unit. FIG. 6 is a diagram schematically illustrating yet another example of a magnetic shift register. FIG. 7 is a diagram schematically illustrating changes in spin information buffered in the magnetic shift register shown in FIG. 6.

[0013] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the following description is for illustrative purposes only and the present invention is not limited to the following embodiments. In the accompanying drawings, the X-axis, Y-axis, and Z-axis are perpendicular to one another.

[0014] FIG. 1 is a diagram illustrating an example of a magnetic shift register. As shown in FIG. 1, the magnetic shift register 1a includes multiple magnetic shift register units 10, a write unit 20, and a read unit 30. FIG. 2 is a cross-sectional view illustrating an example of a magnetic shift register unit. As shown in FIGS. 1 and 2, each of the multiple magnetic shift register units 10 includes a magnetic layer 11 extending in a specific direction (X-axis direction). The number of magnetic shift register units 10 included in the magnetic shift register 1a is not limited to a specific value as long as it is two or more. The magnetic shift register 1a includes five magnetic shift register units 10, for example, a first magnetic shift register unit 10a, a second magnetic shift register unit 10b, a third magnetic shift register unit 10c, a fourth magnetic shift register unit 10d, and a fifth magnetic shift register unit 10e.

[0015] The writing unit 20 electrically connects the multiple magnetic shift register units 10 in series along a specific direction (X-axis direction) and a direction (Y-axis direction) perpendicular to the thickness direction (Z-axis direction) of the magnetic layer 11. As shown in Fig. 2, the writing unit 20 includes, for example, multiple writing elements 22 corresponding to the multiple magnetic shift register units 10, respectively. The writing elements 22 are, for example, spin Hall elements and include a heavy metal that exhibits the spin Hall effect. Examples of such heavy metals are Pt, W, and Ta.

[0016] Pulse current I corresponding to serial data P When the pulse current I flows through the write unit 20, spin information corresponding to each bit of the serial data is transferred to the magnetic layers 11 of the multiple magnetic shift register units 10. P The end of the writing unit 20 on the downstream side in the flow direction of the magnetic flux is connected to a ground electrode. The spin information transferred to the magnetic layer 11 is transferred to the magnetic shift register units 10 in a specific direction (X-axis direction) by a shift current I S The magnetic domain wall motion caused by the flow of the pulse current I is buffered in the plurality of magnetic shift register units 10. For example, five magnetic shift register units 10 consisting of the first magnetic shift register unit 10a, the second magnetic shift register unit 10b, the third magnetic shift register unit 10c, the fourth magnetic shift register unit 10d, and the fifth magnetic shift register unit 10e are buffered in the plurality of magnetic shift register units 10 by the pulse current I P The electrodes are arranged in this order in the flow direction.

[0017] As shown in FIG. 1, the magnetic shift register 1a receives, for example, a shift current I S Each of the magnetic shift register units 10 is connected to the current source 40.

[0018] 1, the readout unit 30 is attached to each of the plurality of magnetic shift register units 10. The readout unit 30 is configured to be able to read the spin information buffered in the plurality of magnetic shift register units 10.

[0019] In the magnetic shift register 1a, the electrical resistances at both ends of the plurality of magnetic shift register units 10 in a specific direction (X-axis direction) are different from each other. With this configuration, the magnetic shift register 1a generates a shift current I S Therefore, the magnetic shift register 1a is advantageous in terms of reducing power consumption. S The flow of current is less restricted by the operating speed of the transistor, and the magnetic shift register 1a is advantageous from the viewpoint of high-speed processing.

[0020] If the electrical resistances at both ends of the plurality of magnetic shift register units 10 in a specific direction are the same, there is a possibility that the operation of the magnetic shift register will be affected as described below. As described above, the plurality of magnetic shift register units 10 are electrically connected in series along the Y-axis direction by the writing unit 20, and the pulse current I P The end of the writing unit 20 on the downstream side in the flow direction of the current is connected to the ground electrode. Due to this configuration, when a shift current is passed from the current source 40 to each of the magnetic shift register units 10 without adjusting the shift current by a transistor or the like, the current density [A / m 2 ] may vary. Such variations in the current density of the shift current in the multiple magnetic shift register units 10 may cause variations in the domain wall motion in the magnetic layer 11 caused by the shift current. Therefore, if the electrical resistances at both ends of the multiple magnetic shift register units 10 are the same, the variations in the domain wall motion caused by the shift current may prevent the spin information from being buffered appropriately, which may cause problems in the operation of the magnetic shift register.

[0021] On the other hand, in the magnetic shift register 1a, the electrical resistances at both ends of the plurality of magnetic shift register units 10 in a specific direction (X-axis direction) are different from each other. This allows the shift current I to be supplied from the current source 40 to each of the plurality of magnetic shift register units 10 at a desired current density without controlling the shift current by a transistor or the like. STherefore, the magnetic shift register 1a is easily configured to pass the magnetic domain wall 11 and the magnetic domain wall 11 is easily spun, and the current density of the shift current is less likely to vary among the magnetic shift register units 10. Therefore, the magnetic domain wall movement caused by the shift current is less likely to vary among the magnetic shift register units 10, and the spin information written in the magnetic layer 11 by the writing unit 20 can be appropriately buffered. As a result, the magnetic shift register 1a is less likely to experience problems in operation.

[0022] As long as the electrical resistances at both ends of the plurality of magnetic shift register units 10 in a specific direction are different from each other, the arrangement of the plurality of magnetic shift register units 10 is not limited to a specific mode. P With this configuration, the current density of the shift current is less likely to vary among the magnetic shift register units 10. For example, the magnetic shift register units 10 are arranged in descending order of electrical resistance in the direction of flow of R 10a >R 10b >R 10c >R 10d >R 10e The condition is met. Under this condition, R 10a , R 10b , R 10c , R 10d , and R 10e are the electrical resistances at both ends in a specific direction of the first magnetic shift register unit 10a, the second magnetic shift register unit 10b, the third magnetic shift register unit 10c, the fourth magnetic shift register unit 10d, and the fifth magnetic shift register unit 10e, respectively.

[0023] In the plurality of magnetic shift register units 10, the difference (R2-R1) between the electrical resistance R1 and the electrical resistance R2 is, for example, 5% or more of the electrical resistance R1. This makes it less likely that variations in shift current density will occur. The electrical resistances R1 and R2 are the electrical resistances at both ends of adjacent magnetic shift register units 10 in a specific direction (X-axis direction) in the plurality of magnetic shift register units 10. The condition R2>R1 is satisfied. The difference (R2-R1) may be 10% or more, 20% or more, 50% or more, or 100% or more of the electrical resistance R1.

[0024] As long as the electrical resistances at both ends of the plurality of magnetic shift register units 10 in a particular direction are different from each other, the relationship between the lengths of the plurality of magnetic shift register units 10 in the particular direction is not limited to a specific relationship. As shown in FIG. 1 , the plurality of magnetic shift register units 10 have, for example, different lengths from each other in the particular direction. With this configuration, the electrical resistances at both ends of the magnetic shift register unit 10 in the particular direction can be adjusted to a desired range by adjusting the length of the magnetic shift register unit 10 in the particular direction. In this case, the plurality of magnetic shift register units 10 may have the same or different widths and may have the same or different thicknesses.

[0025] The plurality of magnetic shift register units 10 are connected to a pulse current I P The magnetic shift register units 10 are arranged in descending order of length in a specific direction in the flow direction of the magnetic flux. 10a >L 10b >L 10c >L 10d >L 10e The condition is met. Under this condition, L 10a , L 10b , L 10c , L 10d , and L 10e are the lengths in a specific direction of the first magnetic shift register unit 10a, the second magnetic shift register unit 10b, the third magnetic shift register unit 10c, the fourth magnetic shift register unit 10d, and the fifth magnetic shift register unit 10e, respectively.

[0026] Shift current I S The adjustment of the shift current I is not limited to a specific mode. The spin information written in the magnetic layer 11 by the writing unit 20 is, for example, adjusted by the shift current I without modulating the current value of the current source 40. Sis passed in parallel to the plurality of magnetic shift register units 10, and is buffered in the plurality of magnetic shift register units 10. For example, no active element such as a transistor or element for modulating the current value such as a variable resistor is disposed between the current source 40 and the magnetic shift register unit 10. When the spin information is buffered in the plurality of magnetic shift register units 10 in this way, the shift current is not adjusted by a transistor or the like, and therefore the power consumption of the magnetic shift register 1a is likely to be reduced. In addition, the processing in the magnetic shift register 1a is likely to be fast. Although resistance loss may occur in the wiring between the current source 40 and the magnetic shift register unit 10, the occurrence of such resistance loss does not constitute modulation.

[0027] As shown in FIG. 2 , each of the multiple magnetic shift register units 10 further includes, for example, a spin Hall layer 12 and a substrate 13. The spin Hall layer 12 is disposed on the substrate 13. The magnetic layer 11 is disposed on the spin Hall layer 12. The substrate 13 is, for example, a single-crystal silicon substrate, a magnesium oxide substrate, or a glass substrate. The substrate 13 may be a single-crystal silicon substrate with a thermal oxide film. The spin Hall layer 12 contains a heavy metal that exhibits the spin Hall effect. Examples of such heavy metals are Pt, W, and Ta. The spin Hall layer 12 may also contain a topological insulator or topological semimetal that exhibits the spin Hall effect. Examples of such materials are IrO2, Bi3Se2, and BiSb. A part of the spin Hall layer 12 can function as a write element 22 of the write unit 20. The spin Hall layer 12 includes, for example, a portion extending along the Y-axis direction, and the portion where this portion intersects with the magnetic layer 11 of the magnetic shift register unit 10 in a planar view can function as the write element 22. The magnetic material included in the magnetic layer 11 is not limited to a specific magnetic material as long as it is capable of transferring, buffering, and reading spin information. An example of the magnetic material is a topological antiferromagnet or ferrimagnet having a composition of Mn3X, where X is, for example, Sn. An example of the ferrimagnet is GdFeCo. The magnetic layer 11 may also include a synthetic antiferromagnet. An example of the synthetic antiferromagnet is a stack formed by combining two or more elements selected from Co, Ni, Pt, and Ru.

[0028] The magnetic layer 11 has, for example, a first region 11a and a second region 11b. The first region 11a is a region in which the magnetic order direction is fixed in advance by a magnet. The second region 11b is a region for buffering spin information written in the first region 11a by the write element 22. The write element 22 is, for example, disposed in contact with the position in the first region 11a closest to the second region 11b. A shift current I is supplied from a current source 40 to the magnetic shift register unit 10. S When a current flows through the magnetic layer 11 and the spin Hall layer 12, for example, the magnetic domain wall of the magnetic layer 11 moves, causing spin information to move from the first region 11a to the second region 11b, where the spin information is buffered.

[0029] As shown in FIG. 2 , the readout unit 30 is disposed, for example, on a predetermined position of the second region 11b. The readout unit 30 includes, for example, a barrier layer 31 and a fixed layer 32. The barrier layer 31 includes a non-magnetic material such as MgO. The fixed layer 32 is, for example, a layer whose magnetic order is fixed in its thickness direction. A terminal for reading out an electrical signal is connected to the fixed layer 32. The second region 11b functions as a free layer whose magnetic order is reversible. Therefore, the second region 11b and the readout unit 30 form a magnetoresistive element such as a magnetic tunnel junction element. The readout unit 30 reads out an electrical signal corresponding to the spin information buffered in the magnetic domain of the second region 11b by, for example, the magnetoresistive effect. The readout unit 30 may be, for example, a pair of electrodes arranged along a direction perpendicular to the longitudinal direction of the magnetic shift register unit 10. This electrode can detect the anomalous Hall effect corresponding to the spin information of the magnetic material by passing a shift current through the spin shift register or a current with a current density lower than the shift current from a current source 40, thereby detecting the buffered information.

[0030] The magnetic layer 11 has, for example, a perpendicular magnetic order along its thickness direction. The magnetic order of the first region 11a is, for example, fixed downward in advance. The magnetic order of the fixed layer 32 of the reading unit 30 is, for example, fixed upward. For example, the magnetic order direction of the magnetic domain directly below the reading unit 30 being parallel and antiparallel to the magnetic order direction of the fixed layer 32 corresponds to bit data "1" and "0," respectively.

[0031] A pulse current I P When the pulse current I flows, a spin current is generated in the thickness direction of the magnetic layer 11 of the write element 22, and a spin-orbit torque (SOT) acts on the magnetic order of the part of the first region 11a that contacts the write element 22. This can reverse the magnetic order of that part. For example, when the magnetic order of that part of the first region 11a is reversed from downward to upward, spin information corresponding to bit data "1" is written. P As described above, the shift current I corresponds to serial data. For example, the magnetic order is reversed during the pulse width period when a current with a current density equal to or greater than a predetermined value flows through the write unit 20, and the magnetic order is not reversed during other periods. As a result, one bit of serial data is transferred to the spin state of the magnetic domain in the first region 11a, thereby writing one bit of spin information. After that, a shift current I S flows, SOT acts on the magnetic layer 11, and a shift current I S The domain wall of the magnetic layer 11 moves in the direction of the arrow (positive direction of the X-axis). As a result, one bit of spin information moves toward the second region 11b. The magnetic order of the magnetic domain in the first region 11a returns to its initial state. Coherent domain wall movement is possible in each of the multiple magnetic shift register units 10.

[0032] Shift current I S Since the shift current I S However, the resistivity of the spin Hall layer 12 is significantly lower than that of the magnetic layer 11. For example, a larger shift current I flows through the spin Hall layer 12 than through the magnetic layer 11. SThe thickness of these layers is adjusted so that the shift current I flows. Therefore, the SOT is dominant over the STT. S The domain wall moves in the direction of (positive direction of the X axis).

[0033] The amount of spin information that can be buffered in the second region 11b of the multiple magnetic shift register units 10 may be the same or different. For example, 5 bits of spin information are buffered in the first magnetic shift register unit 10a. 4 bits of spin information are buffered in the second magnetic shift register unit 10b. 3 bits of spin information are buffered in the third magnetic shift register unit 10c. 2 bits of spin information are buffered in the fourth magnetic shift register unit 10d. 1 bit of spin information is buffered in the fifth magnetic shift register unit 10e. In the multiple magnetic shift register units 10, the reading unit 30 is arranged, for example, at the position farthest from the writing element 22 in a specific direction so that the buffered spin information can be read.

[0034] The magnetic shift register unit 10 may not include, for example, the spin Hall layer 12. In this case, for example, the shift current I S flows in the negative direction of the X-axis through the magnetic shift register unit 10, causing the domain wall of the magnetic layer 11 to move in the positive direction of the X-axis due to the STT. In this case, for example, a spin Hall element that can function as the write element 22 can be disposed on the magnetic layer 11.

[0035] 3 is a diagram showing a change in spin information buffered in the magnetic shift register. The writing unit 20 supplies a pulse current I corresponding to 5-bit serial data of, for example, “a”, “b”, “c”, “d”, and “e”. P In the serial data, five bits "a", "b", "c", "d", and "e" are arranged in this order, and each of "a", "b", "c", "d", and "e" is either "1" or "0".

[0036] First, the pulse current I corresponding to the "a" bit Pflows through the write unit 20, and the write element 22 writes spin information corresponding to this bit into each of the magnetic shift register units 10. Next, a shift current I S is applied, and the spin information corresponding to the bit "a" is buffered in each of the magnetic shift register units 10 by the domain wall motion.

[0037] Next, the pulse current I corresponding to the "b" bit P flows through the write unit 20, and the write element 22 writes spin information corresponding to this bit into each of the magnetic shift register units 10. Next, a shift current I S is flowed, and the spin information corresponding to the bit "b" is buffered in each of the multiple magnetic shift register units 10 by the domain wall motion. As described above, since 1 bit of spin information is buffered in the fifth magnetic shift register unit 10e, the spin information corresponding to the bit "a" is overwritten with the spin information corresponding to the bit "b" and buffered. Therefore, the spin information corresponding to the bit "a" disappears from the fifth magnetic shift register unit 10e.

[0038] Next, the pulse current I corresponding to the "c" bit P flows through the write unit 20, and the write element 22 writes spin information corresponding to this bit into each of the magnetic shift register units 10. Next, a shift current I S is flowed, and the spin information corresponding to the bit "c" is buffered in each of the multiple magnetic shift register units 10 by the domain wall motion. In the fifth magnetic shift register unit 10e, the spin information corresponding to the bit "b" is overwritten with the spin information corresponding to the bit "c" and buffered. Since two bits of spin information are buffered in the fourth magnetic shift register unit 10d, the spin information corresponding to the bits "a" and "b" is overwritten with the spin information corresponding to the bits "b" and "c" and buffered. Therefore, the spin information corresponding to the bit "a" disappears from the fourth magnetic shift register unit 10d.

[0039] Next, the pulse current I corresponding to the bit "d" P flows through the write unit 20, and the write element 22 writes spin information corresponding to this bit into each of the magnetic shift register units 10. Next, a shift current I S is flowed, and spin information corresponding to bit "d" is buffered in each of the multiple magnetic shift register units 10 by domain wall motion. In the fifth magnetic shift register unit 10e, spin information corresponding to bit "c" is overwritten with spin information corresponding to bit "d" and buffered. In the fourth magnetic shift register unit 10d, spin information corresponding to bits "b" and "c" is overwritten with spin information corresponding to bits "c" and "d", respectively, and buffered. Since 3-bit spin information is buffered in the third magnetic shift register unit 10c, spin information corresponding to bits "a", "b", and "c" is overwritten with spin information corresponding to bits "b", "c", and "d", respectively, and buffered. Therefore, spin information corresponding to bit "a" disappears from the third magnetic shift register unit 10c.

[0040] Next, the pulse current I corresponding to the "e" bit P flows through the write unit 20, and the write element 22 writes spin information corresponding to this bit into each of the magnetic shift register units 10. Next, a shift current I Sis flowed, and spin information corresponding to the bit "e" is buffered in each of the multiple magnetic shift register units 10 by domain wall motion. In the fifth magnetic shift register unit 10e, spin information corresponding to the bit "d" is overwritten with spin information corresponding to the bit "e" and buffered. In the fourth magnetic shift register unit 10d, spin information corresponding to the bits "c" and "d" is overwritten with spin information corresponding to the bits "d" and "e", respectively, and buffered. In the third magnetic shift register unit 10c, spin information corresponding to the bits "b", "c", and "d" is overwritten with spin information corresponding to the bits "c", "d", and "e", respectively, and buffered. Since 4-bit spin information is buffered in the second magnetic shift register unit 10b, spin information corresponding to the bits "a", "b", "c", and "d" is overwritten with spin information corresponding to the bits "b", "c", "d", and "e", respectively, and buffered. Therefore, the spin information corresponding to the bit “a” disappears from the second magnetic shift register unit 10 b. Since 5-bit spin information is buffered in the first magnetic shift register unit 10 a, the spin information corresponding to the bits “a”, “b”, “c”, “d”, and “e” is buffered.

[0041] When a predetermined voltage is applied to the magnetoresistive element formed by the second region 11b and the read section 30, a read current flows in the thickness direction of the magnetic layer 11, and this read current is output from a terminal connected to the fixed layer 32. The magnitude of the read current varies depending on the electrical resistance of the magnetoresistive element, which is generated by the magnetoresistive effect. Therefore, a "1" or a "0" can be distinguished based on the magnitude of the output read current (electrical signal). For example, when the magnetic order of the fixed layer 32 and the magnetic order of the magnetic domain directly below it are in the same direction (parallel state), the magnetoresistive element is in a low resistance state, and when these magnetic orders are in opposite directions (antiparallel state), the magnetoresistive element is in a high resistance state. Therefore, data corresponding to the former state is distinguished as a "1," and data corresponding to the latter state is distinguished as a "0."

[0042] The readout unit 30 reads out, for example, spin information that is buffered simultaneously in the multiple magnetic shift register units 10 and corresponds to bits in different orders in the serial data, one by one from each of the multiple magnetic shift register units 10. To enable such an operation, the readout unit 30 is attached to each of the multiple magnetic shift register units 10. With this configuration, serial data can be converted into parallel data in the multiple magnetic shift register units 10 and read out.

[0043] For example, as described above, when spin information corresponding to 5-bit serial data of “a”, “b”, “c”, “d”, and “e” is buffered in multiple magnetic shift register units 10, the spin information corresponding to bits “a”, “b”, “c”, “d”, and “e” is read out from the first magnetic shift register unit 10a, the second magnetic shift register unit 10b, the third magnetic shift register unit 10c, the fourth magnetic shift register unit 10d, and the fifth magnetic shift register unit 10e, respectively.

[0044] The magnetic shift register 1a can be modified from various viewpoints. For example, the magnetic shift register 1a may be modified to a magnetic shift register 1b shown in FIG. 4. The magnetic shift register 1b has the same configuration as the magnetic shift register 1a, except for parts that will be particularly described. Components of the magnetic shift register 1b that are the same as or correspond to components of the magnetic shift register 1a are denoted by the same reference numerals, and detailed description thereof will be omitted. The description of the magnetic shift register 1a also applies to the magnetic shift register 1b, unless technically inconsistent.

[0045] 4, in the magnetic shift register 1b, the multiple magnetic shift register units 10 have different widths. This width is the dimension of the magnetic shift register unit 10 in the Y-axis direction. With this configuration, the electrical resistance at both ends of the magnetic shift register unit 10 in a specific direction can be adjusted to a desired range by adjusting the width of the magnetic shift register unit 10. In this case, the multiple magnetic shift register units 10 may have the same or different lengths in the specific direction and may have the same or different thicknesses.

[0046] The plurality of magnetic shift register units 10 are connected to a pulse current I P The magnetic shift register units 10 are arranged in ascending order of width in the flow direction of the magnetic material. 10a <W 10b <W 10c <W 10d <W 10e The condition is satisfied. Under this condition, W 10a , W 10b , W 10c , W 10d , and W 10e are the widths of the first magnetic shift register unit 10a, the second magnetic shift register unit 10b, the third magnetic shift register unit 10c, the fourth magnetic shift register unit 10d, and the fifth magnetic shift register unit 10e, respectively.

[0047] In the magnetic shift register 1b, 5 bits of spin information can be buffered in each of the multiple magnetic shift register units 10. The readout unit 30 is attached so that, for example, the spin information corresponding to bits in different orders in the serial data is buffered in the multiple magnetic shift register units 10 at the same time and can be read out one by one from each of the multiple magnetic shift register units 10. For example, as shown in FIG. 4, in the multiple magnetic shift register units 10, the distance in a specific direction between the readout unit 30 and the write unit 20 is P The readout unit 30 is attached to each of the plurality of magnetic shift register units 10 so that the magnetic flux is read out in ascending or descending order in the flow direction.

[0048] The magnetic shift register 1a may be modified so that the plurality of magnetic shift register units 10 have different thicknesses. With such a configuration, the electrical resistance at both ends of the magnetic shift register unit 10 in a specific direction can be adjusted to a desired range by adjusting the thickness of the magnetic shift register unit 10. In this case, the plurality of magnetic shift register units 10 may have the same or different lengths in the specific direction, and may have the same or different widths. The plurality of magnetic shift register units 10 may be configured to, for example, be driven by a pulse current I P The layers may be arranged in the machine direction in ascending order of thickness.

[0049] FIG. 5 is a diagram showing another example of a magnetic shift register unit. As shown in FIG. 5, the readout unit 30 of the magnetic shift register unit 10 does not need to include the fixed layer 30. In this case, the readout unit 30 includes electrodes 33a and 33b. In the thickness direction of the magnetic layer 11, the magnetic layer 11 and the barrier layer 31 are disposed between the electrodes 33a and 33b. The electrode 33a is disposed on the barrier layer 31. When a current is applied so that an anomalous Hall effect occurs in the magnetic domain of the magnetic layer 11 directly below the barrier layer 31, the direction of the Hall voltage generated changes depending on the state of magnetic order of the magnetic domain. The readout unit 30 outputs an electrical signal according to the direction of the Hall voltage via the electrodes 33a and 33b, and can distinguish between "1" and "0" depending on the direction of the Hall voltage.

[0050] The magnetic shift register 1a or 1b may be modified as shown in FIG. 6 as a magnetic shift register 1c. The magnetic shift register 1c is configured in the same manner as the magnetic shift register 1a, except for portions that will be particularly described. The same reference numerals are used to designate components of the magnetic shift register 1c that are the same as or correspond to components of the magnetic shift register 1a or 1b, and detailed descriptions thereof will be omitted. The descriptions regarding the magnetic shift register 1a or 1b also apply to the magnetic shift register 1c, unless technically inconsistent.

[0051] As shown in FIG. 6 , the magnetic shift register 1c includes multiple magnetic shift register groups. The number of magnetic shift register groups included in the magnetic shift register 1c is not limited to a specific number as long as it is two or more. The magnetic shift register 1c includes, for example, a first magnetic shift register group 10m and a second magnetic shift register group 10n. The first magnetic shift register group 10m includes, for example, five magnetic shift register units 10, including a first magnetic shift register unit 10a, a second magnetic shift register unit 10b, a third magnetic shift register unit 10c, a fourth magnetic shift register unit 10d, and a fifth magnetic shift register unit 10e. The second magnetic shift register group 10n includes, for example, five magnetic shift register units 10, including a sixth magnetic shift register unit 10f, a seventh magnetic shift register unit 10g, an eighth magnetic shift register unit 10h, a ninth magnetic shift register unit 10i, and a tenth magnetic shift register unit 10j. The sixth magnetic shift register unit 10f, the seventh magnetic shift register unit 10g, the eighth magnetic shift register unit 10h, the ninth magnetic shift register unit 10i, and the tenth magnetic shift register unit 10j are configured similarly to the first magnetic shift register unit 10a, the second magnetic shift register unit 10b, the third magnetic shift register unit 10c, the fourth magnetic shift register unit 10d, and the fifth magnetic shift register unit 10e, respectively.

[0052] In the magnetic shift register 1c, the current source 40 includes a switch for switching, among the multiple magnetic shift register groups, the magnetic shift register group to which the shift current flows from the current source 40. For example, the current source 40 can switch between a state in which the shift current flows to the magnetic shift register unit 10 of the first magnetic shift register group 10m and a state in which the shift current flows to the magnetic shift register unit 10 of the second magnetic shift register group 10n.

[0053] In the magnetic shift register 1c, during a period in which a pulse current and a shift current are flowing through the multiple magnetic shift register units 10 of a specific magnetic shift register group, a voltage for reading spin information is applied to the readout unit 30 of another magnetic shift register group. This allows spin information buffered in another magnetic shift register group to be read while writing to a specific magnetic shift register group. This allows spin information to be read at a low frequency, and the frequency of processing after converting serial data to parallel data can be slowed. For example, in the magnetic shift register 1c, the magnetic shift register groups in which spin information is written and buffered by flowing a pulse current and a shift current are sequentially switched. In addition, the magnetic shift register groups from which the buffered spin information is read are sequentially switched.

[0054] 7 is a diagram showing a change in spin information buffered in the magnetic shift register 1c. As shown in FIG. 7, a pulse current I corresponding to 5-bit serial data of “a”, “b”, “c”, “d”, and “e” is supplied to the writing unit 20 corresponding to the first magnetic shift register group 10m. P In addition, a shift current I from the current source 40 flows. Sflows through the plurality of magnetic shift register units 10 of the first magnetic shift register group 10m. As a result, spin information corresponding to the serial data is buffered in the plurality of magnetic shift register units 10 of the first magnetic shift register group 10m. Next, the spin information buffered in the plurality of magnetic shift register units 10 of the first magnetic shift register group 10m is read out. For example, spin information corresponding to bits "a", "b", "c", "d", and "e" is read out from the first magnetic shift register unit 10a, the second magnetic shift register unit 10b, the third magnetic shift register unit 10c, the fourth magnetic shift register unit 10d, and the fifth magnetic shift register unit 10e, respectively. During the period when the spin information buffered in the plurality of magnetic shift register units 10 of the first magnetic shift register group 10m is read out, a pulse current I corresponding to 5-bit serial data of, for example, "f", "g", "h", "i", and "j" is supplied to the writing unit 20 corresponding to the second magnetic shift register group 10n. P In addition, a shift current I from the current source 40 flows. S flows through the plurality of magnetic shift register units 10 of the second magnetic shift register group 10n. As a result, spin information corresponding to the serial data is buffered in the plurality of magnetic shift register units 10 of the second magnetic shift register group 10n. In the serial data, five bits "f", "g", "h", "i", and "j" are arranged in this order, and each of "f", "g", "h", "i", and "j" is "1" or "0".

[0055] A first aspect of the present invention provides a magnetic shift register comprising: a plurality of magnetic shift register units each including a magnetic layer extending in a specific direction; a write unit electrically connecting the plurality of magnetic shift register units in series along a direction perpendicular to the specific direction and a thickness direction of the magnetic layer; and a read unit attached to each of the plurality of magnetic shift register units, wherein spin information corresponding to each bit of serial data is transferred to the magnetic layer of the plurality of magnetic shift register units by causing a pulse current corresponding to serial data to flow through the write unit, the spin information is buffered in the plurality of magnetic shift register units by domain wall motion caused by the shift current flowing in the specific direction in the plurality of magnetic shift register units, the read unit is capable of reading out the spin information buffered in the plurality of magnetic shift register units, and the plurality of magnetic shift register units have different electrical resistances at both ends in the specific direction.

[0056] A second aspect of the present invention provides a magnetic shift register according to the first aspect, wherein the spin information is buffered in the plurality of magnetic shift register units by causing the shift current to flow in parallel in the plurality of magnetic shift register units without modulating a current value of a current source of the shift current.

[0057] A third aspect of the present invention provides the magnetic shift register according to the first or second aspect, wherein the plurality of magnetic shift register units are arranged in ascending order of the electrical resistance in the flow direction of the pulse current.

[0058] A fourth aspect of the present invention provides the magnetic shift register according to any one of the first to third aspects, wherein the plurality of magnetic shift register units have different lengths in the specific direction.

[0059] A fifth aspect of the present invention provides the magnetic shift register according to any one of the first to fourth aspects, wherein the plurality of magnetic shift register units have widths different from each other.

[0060] A sixth aspect of the present invention provides the magnetic shift register according to any one of the first to fifth aspects, wherein the plurality of magnetic shift register units have thicknesses different from each other.

[0061] A seventh aspect of the present invention provides a magnetic shift register according to any one of the first to sixth aspects, wherein the readout unit reads out the spin information, which is buffered in the plurality of magnetic shift register units at the same time and corresponds to bits in different orders in the serial data, one by one from each of the plurality of magnetic shift register units.

Claims

1. A magnetic shift register comprising: a plurality of magnetic shift register units, each including a magnetic layer extending in a specific direction; a write unit electrically connecting the plurality of magnetic shift register units in series along a direction perpendicular to the specific direction and the thickness direction of the magnetic layer; and a read unit attached to each of the plurality of magnetic shift register units, wherein spin information corresponding to each bit of serial data is transferred to the magnetic layer of the plurality of magnetic shift register units by causing a pulse current corresponding to serial data to flow through the write unit, the spin information is buffered in the plurality of magnetic shift register units by domain wall movement caused by the shift current flowing in the specific direction in the plurality of magnetic shift register units, the read unit is capable of reading out the spin information buffered in the plurality of magnetic shift register units, and the electrical resistances of both ends of the plurality of magnetic shift register units in the specific direction are different from each other.

2. The magnetic shift register according to claim 1, wherein the spin information is buffered in the plurality of magnetic shift register units by causing the shift current to flow in parallel through the plurality of magnetic shift register units without modulating the current value of a current source of the shift current.

3. The magnetic shift register according to claim 1, wherein the plurality of magnetic shift register units are arranged in descending order of the electrical resistance in the flow direction of the pulse current.

4. The magnetic shift register according to claim 1, wherein the plurality of magnetic shift register units have different lengths in the specific direction.

5. The magnetic shift register according to claim 1, wherein the plurality of magnetic shift register units have widths different from each other.

6. The magnetic shift register according to claim 1, wherein the plurality of magnetic shift register units have thicknesses different from each other.

7. The magnetic shift register according to claim 1, wherein the readout unit reads out the spin information, which is buffered in the plurality of magnetic shift register units at the same time and corresponds to bits in different orders in the serial data, one by one from each of the plurality of magnetic shift register units.

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