Magnetic shift register

Abstract

This magnetic shift register comprises a plurality of magnetic shift register units, a writing unit, and a reading unit. A pulsed current corresponding to serial data flows through the writing unit, and spin information corresponding to each bit of the serial data is thereby transferred to a magnetic body layer of the plurality of magnetic shift register units. The spin information transferred to the magnetic body layer is buffered by the plurality of magnetic shift register units by magnetic domain wall displacement accompanying the flow of a shift current in a specific direction. The reading unit is buffered at the same time by the plurality of magnetic shift register units, and reads the spin information corresponding to bits in a different order in the serial data one by one from each of the plurality of magnetic shift register units.

Description

Magnetic Shift Register

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

[0002] A register utilizing domain wall motion is 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 equipped with 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. The shift current flows only through a specific shift register unit until writing of spin information to that specific shift register unit is completed. Once writing of spin information to that specific shift register unit is completed, the shift current flows through another shift register unit.

[0005] International Publication No. 2022 / 158545

[0006] In the photonic spin register described in Patent Document 1, a shift current flows only through a specific shift register unit until writing of spin information to the specific shift register unit is completed. The photonic spin register described in Patent Document 1 does not assume that serial data will be converted into parallel data using multiple shift register units.

[0007] In the photonic spin register described in Patent Document 1, the control unit must be configured so that it can select the shift register unit to which the shift current will flow from among multiple shift register units, which can place constraints on the design of the shift register.

[0008] In view of the above circumstances, the present invention provides a magnetic shift register that can convert serial data into parallel data using a plurality of magnetic shift register units.

[0009] 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 reads out the spin information buffered simultaneously in the plurality of magnetic shift register units and corresponding to bits of different orders in the serial data, one by one, from each of the plurality of magnetic shift register units, and converts the serial data into parallel data.

[0010] According to the magnetic shift register, serial data can be converted into parallel data using a plurality of magnetic shift register units.

[0011] FIG. 1 is a diagram schematically showing an example of a magnetic shift register. FIG. 2 is a cross-sectional diagram schematically showing an example of a magnetic shift register unit. FIG. 3 is a diagram schematically showing changes in spin information buffered in the magnetic shift register. FIG. 4 is a diagram schematically explaining another example of a magnetic shift register unit. FIG. 5 is a diagram schematically explaining yet another example of a magnetic shift register unit. FIG. 6 is a diagram schematically showing another example of a magnetic shift register. FIG. 7 is a diagram schematically showing changes in spin information buffered in the magnetic shift register. FIG. 8 is a diagram schematically explaining yet another example of a magnetic shift register unit. FIG. 9 is a diagram schematically showing yet another example of a magnetic shift register. FIG. 10 is a diagram schematically showing changes in spin information buffered in the magnetic shift register shown in FIG. 9.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] 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, for example, 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.

[0016] 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.

[0017] 1, the readout unit 30 is attached to each of the multiple magnetic shift register units 10. The readout unit 30 is configured to be able to read spin information buffered in the multiple magnetic shift register units 10. The readout unit 30 reads out spin information that is buffered in the multiple magnetic shift register units at the same time and corresponds to bits in different orders in the serial data from each of the multiple magnetic shift register units 10 one by one, and converts the serial data into parallel data. In this way, the magnetic shift register 1a can convert serial data into parallel data using the multiple magnetic shift register units 10.

[0018] In the magnetic shift register 1a, a shift current I is supplied to only a specific magnetic shift register unit 10 from among the plurality of magnetic shift register units 10. S In other words, in the magnetic shift register 1a, the shift current I S may be washed away.

[0019] 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. With this configuration, the crystalline orientation of the material in the magnetic layer 11 is likely to be in a desired state, and the performance of the magnetic shift register 1a is likely to be improved. The substrate 13 is, for example, a single-crystal silicon substrate, a magnesium oxide substrate, or a glass substrate. The substrate 13 may also 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 IrO 2 , Bi 3 Se 2 , and BiSb. A portion 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.

[0020] 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. SWhen 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.

[0021] 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.

[0022] 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.

[0023] A pulse current I PWhen 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.

[0024] 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. S The thickness t of the magnetic layer 11 is set so that 11 , the thickness t of the spin Hall layer 12 12 , and their sum t M Therefore, SOT becomes dominant over STT, and the shift current I S The domain wall moves in the direction of (positive direction of the X axis).

[0025] 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 Sflows 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.

[0026] The amount of spin information that can be buffered in the second region 11b may be the same or different in the multiple magnetic shift register units 10. For example, each of the multiple magnetic shift register units 10 can buffer 5 bits of spin information.

[0027] For example, the distance between the position where the spin information is read by the readout unit 30 and the position where the spin information is transferred differs among the multiple magnetic shift register units 10. With this configuration, even if spin information corresponding to the same serial data is buffered in each of the multiple magnetic shift register units 10, the serial data can be converted into parallel data using the multiple magnetic shift register units 10.

[0028] In the magnetic shift register 1a, for example, in the plurality of magnetic shift register units 10, the distance between the position where the spin information is read by the readout unit 30 and the position where the spin information is transferred is determined by a pulse current I P In the plurality of magnetic shift register units 10, for example, D 10a >D 10b >D 10c >D 10d >D 10e or D 10a <D 10b <D 10c <D 10d <D 10e The condition is met. Under this condition, D 10a , D 10b , D 10c , D 10d , and D 10eare the distances between the position where the spin information is read by the readout unit 30 and the position where the spin information is transferred in 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.

[0029] 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".

[0030] First, the pulse current I corresponding to the "a" 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 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.

[0031] 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 plurality of magnetic shift register units 10 by the domain wall motion. As a result, the spin information corresponding to the bits "a" and "b" is buffered in each of the plurality of magnetic shift register units 10.

[0032] Next, the pulse current I corresponding to the "c" 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 flowed, and the spin information corresponding to the bit “c” is buffered in each of the plurality of magnetic shift register units 10 by the domain wall motion. As a result, the spin information corresponding to the bits “a”, “b”, and “c” is buffered in each of the plurality of magnetic shift register units 10.

[0033] 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 the spin information corresponding to the bit “d” is buffered in each of the plurality of magnetic shift register units 10 by the domain wall motion. As a result, the spin information corresponding to the bits “a”, “b”, “c”, and “d” is buffered in each of the plurality of magnetic shift register units 10.

[0034] 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 S is flowed, and the spin information corresponding to the bit “e” is buffered in each of the magnetic shift register units 10 by the domain wall motion. As a result, the spin information corresponding to the bits “a”, “b”, “c”, “d”, and “e” is buffered in each of the magnetic shift register units 10.

[0035] 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, for example, data corresponding to the former state is distinguished as a "1," and data corresponding to the latter state is distinguished as a "0."

[0036] For example, as described above, spin information corresponding to 5-bit serial data of “a”, “b”, “c”, “d”, and “e” can be buffered in multiple magnetic shift register units 10. In this case, the readout unit 30 attached to the first magnetic shift register unit 10a reads out the spin information corresponding to the “a” bit. The readout unit 30 attached to the second magnetic shift register unit 10b reads out the spin information corresponding to the “b” bit. The readout unit 30 attached to the third magnetic shift register unit 10c reads out the spin information corresponding to the “c” bit. The readout unit 30 attached to the fourth magnetic shift register unit 10d reads out the spin information corresponding to the “d” bit. The readout unit 30 attached to the fifth magnetic shift register unit 10e reads out the spin information corresponding to the “e” bit. The reading of the spin information corresponding to the 5-bit serial data of “a”, “b”, “c”, “d”, and “e” can be performed as a parallel process. Therefore, the serial data can be converted into parallel data by the magnetic shift register 1a and output.

[0037] The magnetic shift register 1a can be modified from various viewpoints. FIG. 4 is a diagram for explaining another example of the magnetic shift register unit. As shown in FIG. 4, the magnetic layer 11 may be disposed on the substrate 13, and the spin Hall layer 12 may be disposed on the magnetic layer 11. In such a case, the magnetic shift register unit 10 also receives the shift current I S When the current flows, the SOT is applied to the magnetic layer 11 by the spin Hall layer 12, and a shift current I S The magnetic domain wall of the magnetic layer 11 can be moved in the direction of the positive X-axis direction.

[0038] FIG. 5 is a diagram illustrating 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 32. In this case, the readout unit 30 includes, for example, 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 to the magnetic domain of the magnetic layer 11 directly below the electrode 33a so that an anomalous Hall effect occurs, 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.

[0039] The magnetic shift register 1a may be modified as shown in FIG. 6 as a magnetic shift register 1b. The magnetic shift register 1b has the same configuration as the magnetic shift register 1a, except for parts that will be particularly described. Components that are the same as or correspond to those of the magnetic shift register 1a are given the same reference numerals, and detailed descriptions thereof will be omitted. The descriptions of the magnetic shift register 1a and its modifications also apply to the magnetic shift register 1b, unless technically inconsistent.

[0040] In the magnetic shift register 1b, the spin information transferred to the magnetic layers 11 of the plurality of magnetic shift register units by the writing unit 20 is transferred in a specific direction (X-axis direction) by a shift current I SThe magnetic shift register units 10 buffer the spin information corresponding to bits in different orders in the serial data by domain wall motion caused by the flow of current. At this time, the domain wall motion occurs at different domain wall motion velocities [m / sec] in the magnetic shift register units 10. By utilizing such differences in domain wall motion velocities, the magnetic shift register units 10 can buffer spin information corresponding to bits in different orders in the serial data.

[0041] In the magnetic shift register 1b, for example, the domain wall motion speed in the plurality of magnetic shift register units 10 is P In the plurality of magnetic shift register units 10, for example, S 10a <S 10b <S 10c <S 10d <S 10e The condition is satisfied. Under this condition, S 10a , S 10b , S 10c , S 10d , and S 10e are the domain wall motion velocities in 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.

[0042] In the multiple magnetic shift register units 10 of the magnetic shift register 1b, the difference (S2-S1) between the domain wall motion velocity S1 and the domain wall motion velocity S2 is, for example, 5% or more of the domain wall motion velocity S1. The domain wall motion velocity S1 and the domain wall motion velocity S2 are the domain wall motion velocities in adjacent magnetic shift register units 10 among the multiple magnetic shift register units 10. The difference (S2-S1) may be 10% or more, 20% or more, 50% or more, or 100% or more of the domain wall motion velocity S1.

[0043] 6, in the magnetic shift register 1b, the plurality of 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 domain wall motion speeds of the plurality of magnetic shift register units 10 can be made different by adjusting the width 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 a specific direction (X-axis direction) and may have the same or different thicknesses.

[0044] 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 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.

[0045] 7 is a diagram showing a change in spin information buffered in the magnetic shift register. In the magnetic shift register 1b, similarly to the magnetic shift register 1a, the writing unit 20 receives a pulse current I corresponding to 5-bit serial data of, for example, “a”, “b”, “c”, “d”, and “e”. P is washed away.

[0046] First, the pulse current I corresponding to the "a" 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 the spin information corresponding to the bit "a" is buffered in each of the multiple magnetic shift register units 10 by the domain wall motion. In FIG. 7, the area surrounded by the dashed circle indicates the position where the spin information is read by the readout unit 30. As shown in FIG. 7, for example, in the fifth magnetic shift register unit 10e, the spin information corresponding to the bit "a" is buffered in each of the multiple magnetic shift register units 10 by the single shift current I S The magnetic domain wall movement accompanying this causes the signal to be buffered at a position where it can be read by the reading unit 30 .

[0047] 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 spin information corresponding to the bit "b" is buffered in each of the multiple magnetic shift register units 10 by domain wall motion. As a result, spin information corresponding to the bits "a" and "b" is buffered in the first magnetic shift register unit 10a, the second magnetic shift register unit 10b, the third magnetic shift register unit 10c, and the fourth magnetic shift register unit 10d. In the fourth magnetic shift register unit 10d, the spin information corresponding to the bit "a" is buffered at a position readable by the readout unit 30. In the fifth magnetic shift register unit 10e, the spin information buffered at a position readable by the readout unit 30 is overwritten with the spin information corresponding to the bit "b".

[0048] 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 Sis flowed, and spin information corresponding to the bit "c" is buffered in each of the multiple magnetic shift register units 10 by domain wall motion. As a result, spin information corresponding to the bits "a", "b", and "c" is buffered in the first magnetic shift register unit 10a, the second magnetic shift register unit 10b, and the third magnetic shift register unit 10c. In the third magnetic shift register unit 10c, the spin information corresponding to the bit "a" is buffered at a position readable by the readout unit 30. In the fourth magnetic shift register unit 10d, the spin information buffered at a readable position by the readout unit 30 is overwritten with the spin information corresponding to the bit "b". In the fifth magnetic shift register unit 10e, the spin information buffered at a readable position by the readout unit 30 is overwritten with the spin information corresponding to the bit "c".

[0049] 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 the bit "d" is buffered in each of the multiple magnetic shift register units 10 by domain wall motion. As a result, spin information corresponding to the bits "a", "b", "c", and "d" is buffered in the first magnetic shift register unit 10a and the second magnetic shift register unit 10b. In the second magnetic shift register unit 10b, the spin information corresponding to the bit "a" is buffered at a position readable by the readout unit 30. In the third magnetic shift register unit 10c, the spin information buffered at the readout position by the readout unit 30 is overwritten with the spin information corresponding to the bit "b". In the fourth magnetic shift register unit 10d, the spin information buffered at the readout position by the readout unit 30 is overwritten with the spin information corresponding to the bit "c". In the fifth magnetic shift register unit 10e, the spin information buffered at the readout position by the readout unit 30 is overwritten with the spin information corresponding to the bit "d".

[0050] 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 S is 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. As a result, spin information corresponding to the bits "a", "b", "c", "d", and "e" is buffered in the first magnetic shift register unit 10a. In the first magnetic shift register unit 10a, the spin information corresponding to the bit "a" is buffered at a position readable by the readout unit 30. In the second magnetic shift register unit 10b, the spin information buffered at the readout position by the readout unit 30 is overwritten with the spin information corresponding to the bit "b". In the third magnetic shift register unit 10c, the spin information buffered at the readout position by the readout unit 30 is overwritten with the spin information corresponding to the bit "c". In the fourth magnetic shift register unit 10d, the spin information buffered at the readout position by the readout unit 30 is overwritten with the spin information corresponding to the bit "d". In the fifth magnetic shift register unit 10e, the spin information buffered at the readout position by the readout unit 30 is overwritten with the spin information corresponding to the bit "e". As a result, in the multiple magnetic shift register units 10, spin information corresponding to bits of different orders in the serial data is buffered at positions that can be read by the reading unit 30. The spin information is read in parallel from the multiple magnetic shift register units 10 by the reading unit 30, and the serial data is converted into parallel data.

[0051] There is no particular limitation on the method for making the domain wall motion speeds different from one another in the plurality of magnetic shift register units 10. For example, as described above, if the plurality of magnetic shift register units 10 have different widths from one another, the electrical resistances of the plurality of magnetic shift register units 10 are different from one another, and therefore, the shift current I SThe current densities in the two directions can be made different from each other. The higher the current density, the faster the domain wall motion speed.

[0052] In the plurality of magnetic shift register units 10 having the configuration shown in FIG. 2, FIG. 4, or FIG. 5, the thickness t 11 , the thickness t of the spin Hall layer 12 12 , and their sum t M may be different from each other. This allows the domain wall motion speeds to be different from each other in the multiple magnetic shift register units 10. In this case, the multiple magnetic shift register units 10 may have the same or different lengths in a specific direction (X-axis direction) and may have the same or different widths.

[0053] For example, the sum t M is the same, the thickness t 11 Thickness t 12 The larger the ratio of the thickness t 11 Thickness t 12 This is because the larger the ratio, the more likely SOT is to be dominant compared to STT.

[0054] For example, thickness t 11 Thickness t 12 If the ratio of is the same, the sum t M The smaller the value of t, the faster the domain wall motion speed. M The smaller the shift current I S This is because the current density can become large.

[0055] FIG. 8 is a diagram illustrating another example of a magnetic shift register unit. As shown in FIG. 8, the magnetic shift register unit 10 may further include a spin Hall layer 14 in addition to the spin Hall layer 12. The magnetic layer 11 is disposed between the spin Hall layer 12 and the spin Hall layer 14 in the thickness direction. The spin Hall layer 12 and the spin Hall layer 14 contain, for example, different materials in which the spin currents generated by the spin Hall effect are directed in opposite directions. In this configuration, the domain wall motion speeds of the multiple magnetic shift register units 10 can be made different from one another by combining the materials contained in the spin Hall layer 12 and the spin Hall layer 14. An example of a combination of the materials contained in the spin Hall layer 12 and the spin Hall layer 14 is a combination of Pt and W.

[0056] 8, the positions of the spin Hall layers 12 and 14 may be interchanged. The magnetic shift register unit 10 may include three or more spin Hall layers containing different materials.

[0057] In the plurality of magnetic shift register units 10, the above-described modes for making the domain wall motion speeds different from one another may be combined as appropriate.

[0058] The magnetic shift registers 1a and 1b may be modified to a magnetic shift register 1c shown in FIG. 9. The magnetic shift register 1c is configured in the same manner as the magnetic shift register 1a or 1b, except for parts 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 the 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.

[0059] As shown in FIG. 9 , 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.

[0060] 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.

[0061] 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.

[0062] 10 is a diagram showing a change in spin information buffered in the magnetic shift register 1c. As shown in FIG. 10, 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".

[0063] 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 the 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 reads out the spin information buffered simultaneously in the plurality of magnetic shift register units and corresponding to bits of different orders in the serial data, one by one, from each of the plurality of magnetic shift register units, and converts the serial data into parallel data.

[0064] A second aspect of the present invention provides the magnetic shift register of the first aspect, wherein the distances between the position where the spin information is read by the readout unit and the position where the spin information is transferred are different from each other in the plurality of magnetic shift register units.

[0065] 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 cause the domain wall motion at different domain wall motion speeds in 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 the 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 reads out the spin information buffered simultaneously in the plurality of magnetic shift register units and corresponding to bits of different orders in the serial data, one by one, from each of the plurality of magnetic shift register units, and converts the serial data into parallel data.

2. The magnetic shift register according to claim 1, wherein the distances between the position where the spin information is read by the readout unit and the position where the spin information is transferred are different in the plurality of magnetic shift register units.

3. The magnetic shift register according to claim 1, wherein the magnetic shift register units cause the domain wall motion at different domain wall motion speeds in the magnetic shift register units.

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