Magnetic nanowire memory device and magnetic domain driving method

Abstract

To provide a magnetic nanowire memory device and a magnetic domain driving method on a magnetic nanowire for reducing a driving current applied to the magnetic nanowire.SOLUTION: A magnetic nanowire memory device 1 includes: a magnetic nanowire 10 in which a magnetic domain 15 is formed on a nanowire-shaped magnetic body and the magnetic domain 15 is driven in an extending direction; a recording element 20 which is a nanowire-shaped conductor placed to be insulated from and cross the magnetic nanowire 10 and serves as a flow path for a recording current IR that magnetizes the magnetic nanowire 10; and a current control unit 30 that applies a drive current ID to the magnetic nanowire 10 by driving the magnetic domain 15, and applies an assist current IA that assists the driving of the magnetic domain 15 to the recording element 20 so as to be smaller than the recording current IR.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a magnetic nanowire memory device and a method for driving a magnetic domain in a magnetic nanowire. [Background technology]

[0002] A magnetic nanowire memory device is a magnetic recording device that uses a magnetic nanowire formed into a thin wire as a medium. For example, Patent Document 1 describes a magnetic nanowire memory device in which one recording element, which is a conductor formed into a thin wire, is formed so as to cross the magnetic nanowire via an insulating layer. Patent Document 2 describes a magnetic nanowire memory device with two recording elements. In a magnetic nanowire memory device, magnetic domains are formed in the magnetic nanowire by the magnetic field of a current applied to the recording element. A magnetic domain is a region with the same magnetization direction. When the magnetization directions of adjacent magnetic domains are different, a magnetic wall is formed between the magnetic domains. A magnetic domain wall is a transition region of the magnetization direction, and inside the magnetic domain wall, the magnetization direction gradually changes. In a magnetic nanowire memory device, the magnetic domains and domain walls are moved in the extension direction of the magnetic nanowire by magnetic domain driving. It is known that when a pulsed current of a certain value or more is applied to a magnetic nanowire, the magnetic domains and domain walls move while maintaining their magnetization direction. Magnetic domain driving is an operation that utilizes this phenomenon to move the magnetic domains and domain walls. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2022-179046 A [Patent Document 2] Patent Publication No. 2021-026788 Summary of the Invention [Problem to be solved by the invention]

[0004] In a magnetic nanowire memory device, whether it has one recording element or two, information can be sequentially stored in the magnetic nanowire by repeating magnetic domain formation and magnetic domain driving. However, when there are two recording elements, a magnetic domain wall is formed at the position where the magnetic domain intersects with the recording element in the magnetic domain formation. Then, in the magnetic domain driving, the magnetic domain wall is pinned at the position where the magnetic domain intersects with the recording element, and the magnetic domain cannot move. For this reason, there is a problem that the magnetic domain driving in the case of two recording elements requires a larger driving current, which is the current applied to the magnetic nanowire, than in the case of one recording element. In addition, a reduction in the driving current is desired even in the case of one recording element.

[0005] The present invention has been made to solve the above problems, and has an object to provide a magnetic nanowire memory device and a method for driving magnetic domains in a magnetic nanowire that reduce the drive current applied to the magnetic nanowire. [Means for solving the problem]

[0006] A magnetic nanowire memory device according to an embodiment includes a magnetic nanowire in which a magnetic domain is formed in a thin-line magnetic material and the magnetic domain is driven in an extension direction, a recording element which is a thin-line conductor arranged to be insulated from and intersect with the magnetic nanowire and serves as a flow path for a recording current that magnetizes the magnetic nanowire, and a current control unit which applies a driving current to the magnetic nanowire in driving the magnetic domain and applies an assist current to the recording element which is smaller than the recording current and assists in driving the magnetic domain.

[0007] In addition, a magnetic domain driving method according to an embodiment is a magnetic domain driving method for driving a magnetic domain formed in a magnetic wire, which is a thin-line-shaped magnetic material, in the extension direction of the magnetic wire, and includes applying a driving current to the magnetic wire and applying an assist current smaller than the recording current to a recording element, which is a thin-line-shaped conductor arranged to be insulated from and cross the magnetic wire and serves as a flow path for a recording current that magnetizes the magnetic wire, and applying the assist current so as to be synchronized with the driving current. Effect of the Invention

[0008] According to the present invention, it is possible to provide a magnetic nanowire memory device and a method for driving a magnetic domain in a magnetic nanowire, which are capable of reducing the drive current applied to the magnetic nanowire. [Brief description of the drawings]

[0009] [Figure 1] 1 is a block diagram illustrating an outline of a magnetic nanowire memory device according to an embodiment. [Figure 2A] 5A and 5B are cross-sectional views for explaining the formation of downward magnetic domains in the magnetic nanowire memory device according to the embodiment. [Figure 2B] 5A and 5B are cross-sectional views for explaining the formation of upward magnetic domains in the magnetic nanowire memory device according to the embodiment. [Figure 2C] 5A and 5B are cross-sectional views for explaining assistance of magnetic domain driving in the magnetic nanowire memory device according to the embodiment. [Diagram 3] 1 is a photograph illustrating a domain wall driven by applying an assist current along with a drive current. [Figure 4] 4 is a graph illustrating current waveforms of a drive current and an assist current applied in driving the domain wall in FIG. 3. [Diagram 5] 4 is a flowchart illustrating a method for recording magnetic domains according to the embodiment. [Figure 6A] 4 is a plan view illustrating a state in which a magnetic nanowire is initialized in the magnetic domain recording method according to the embodiment. FIG. [Figure 6B] 4A to 4C are plan views illustrating a state in which magnetic domains are formed in the magnetic domain recording method according to the embodiment. [Figure 6C] 11 is a plan view illustrating a state in which a magnetic domain is driven with assistance from an assist current in the magnetic domain recording method according to the embodiment. FIG. [Figure 6D] 11 is a plan view illustrating a state in which the next magnetic domain is formed in the magnetic domain recording method according to the embodiment. FIG. [Figure 6E] 11 is a plan view illustrating a state in which a magnetic domain is driven with assistance from an assist current in the magnetic domain recording method according to the embodiment. FIG. [Figure 7A]FIG. 11 is a cross-sectional view for explaining assistance of magnetic domain driving when there is one recording element. [Figure 7B] FIG. 11 is a cross-sectional view for explaining assistance of magnetic domain driving when there are three recording elements. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] [Magnetic nanowire memory device] A magnetic nanowire memory device 1 according to an embodiment will be described with reference to the drawings. The magnetic nanowire memory device 1 is a memory device that can sequentially record and reproduce information in magnetic domains aligned in the extension direction of a linear magnetic nanowire. Here, the magnetization direction of each magnetic domain is either upward or downward, and the magnetic nanowire memory device 1 can record and reproduce, for example, binary information. 1, the magnetic nanowire memory device 1 includes a magnetic nanowire 10, a recording element 20, a current control unit 30, a reproducing element 40, and a detection processing unit 50. The magnetic nanowire 10 and the recording element 20 are insulated by an insulating film 60. Although the following description will be given of a case in which there is one magnetic nanowire 10, the magnetic nanowire memory device 1 can perform parallel processing of recording and reproducing information by arranging a plurality of magnetic nanowires 10, for example, in parallel.

[0011] (magnetic thin wire) The magnetic nanowire 10 is a thin magnetic body that serves as an information recording medium. Magnetic domains 15, which are regions with the same magnetization direction, are formed in the magnetic nanowire 10, and information is recorded as the magnetization direction of each magnetic domain 15. In Figures 1 to 2C, 7A, and 7B, the magnetization directions are indicated by white arrows. The magnetic domains 15 are aligned in the extension direction of the magnetic nanowire 10, and domain walls 16 are magnetically formed between the magnetic domains 15 whose magnetization directions are reversed. The magnetic nanowire 10 is a film-like member whose width is greater than its thickness. The magnetic nanowire 10 is made of a material that is easily magnetized in the thickness direction, i.e., the perpendicular direction. The material of the magnetic nanowire 10 can be a multilayer film such as a Co / Pd multilayer film in which a transition metal such as Co is repeatedly laminated with Pd, Pt, and Cu, an alloy (RE-TM alloy) of a rare earth metal such as Tb-Fe-Co or Gd-Fe and a transition metal, or a rare earth multilayer film such as Tb / Co.

[0012] (Recording element) The recording element 20 is a thin wire-shaped conductor that serves as a flow path for a recording current IR that forms a magnetic domain. The recording element 20 is also a flow path for an assist current IA that assists magnetic domain driving. The recording element 20 is disposed so as to intersect with the magnetic nanowire 10. The recording element 20 and the magnetic nanowire 10 are in a twisted position with an insulating film 60 interposed therebetween. Here, the recording element 20 is disposed above the magnetic nanowire 10 so as to be perpendicular to the magnetic nanowire 10 in a plan view. Here, two parallel recording elements 20 are arranged with a gap G1 between them. The width of the gap G1 is preferably 2 μm or less from the viewpoint of not reducing the magnetic field of the recording current IR. The material of the recording element 20 may be a metal such as Cu, Al, Au, Ag, Ta, Cr, Co, or an alloy thereof, or may be a laminate of these. Note that the two recording elements 20 may be described as one being a first recording element 21 and the other being a second recording element 22, or as recording elements 21 and 22.

[0013] A magnetic flux concentration member 25 for concentrating magnetic flux may be disposed in the gap G1. By disposing the magnetic flux concentration member 25, magnetic domains are easily formed. The material of the magnetic flux concentration member 25 may be soft ferrite such as Mn-Zn ferrite, Ni-Zn ferrite, Mn-Ni ferrite, or Ni-Zn-Co ferrite.

[0014] The insulating film 60 is disposed between the recording element 20 and the magnetic nanowire 10. The insulating film 60 is disposed so that the magnetic nanowire 10 and the recording element 20 do not come into contact with each other, and may be disposed, for example, so as to cover the entire magnetic nanowire 10. In FIG. 1, the insulating film 60 is omitted except for the periphery of the recording element 20. The thickness of the insulating film 60 may be, for example, 10 nm added to the thickness of the magnetic nanowire 10, and is preferably 20 nm or less from the viewpoint of not reducing the magnetic field of the recording current IR. The material of the insulating film 60 may be, for example, an oxide film such as SiO2.

[0015] (Current control section) The current control unit 30 is a device that controls the current applied to the magnetic nanowire 10 and the recording element 20. The current control unit 30 converts a sequence of binary information to be recorded in the magnetic nanowire 10 into a sequence of magnetization directions, and forms magnetic domains by applying a recording current IR to the recording element 20. The current control unit 30 also applies a drive current ID to the magnetic nanowire 10 and an assist current IA to the recording element 20 to drive the magnetic domains. The current control unit 30 is wired independently to the magnetic nanowire 10 and the recording element 20, and can independently control the current applied to each of them. Furthermore, when there are multiple recording elements 20, the current control unit 30 is wired independently to each of the multiple recording elements 20, and can independently control the current applied to the multiple recording elements 20. Here, the currents of the first recording element 21 and the second recording element 22 are independently controlled.

[0016] (recording current) The recording current IR is a current that is applied to the recording element 20 to form magnetic domains. When the magnetic field of the recording current IR exceeds the coercive force of the magnetic nanowire 10, the magnetization direction of the magnetic nanowire 10 is reversed and magnetic domains are formed. The magnetic field can be strengthened by increasing the recording current IR. The magnitude of the recording current IR for forming magnetic domains varies greatly depending on the structure of the magnetic nanowire memory device 1 and the materials of the recording element 20, etc.

[0017] Here, a case where there are two recording elements 20 will be described. As illustrated in FIG. 2A and FIG. 2B, recording currents IR are applied to the two recording elements 20 in mutually opposite directions. In FIG. 2A, a recording current IR1 perpendicular to the paper surface and directed from the front side to the back side is applied to the first recording element 21, and a recording current IR2 directed from the back side to the front side is applied to the second recording element 22. The magnetic fields MR of the recording currents IR1 and IR2 are generally downward in the region of the magnetic nanowire 10 located between the first recording element 21 and the second recording element 22. The magnetic field MR forms a downward magnetic domain 15A in the magnetic nanowire 10A whose magnetization direction was upward, and a domain wall 16A is formed directly below the recording element 20. In Fig. 2B, the directions of the recording currents IR1 and IR2 are reversed with respect to Fig. 2A, and the magnetic field MR is generally upward in the region of the magnetic nanowire 10 located between the first recording element 21 and the second recording element 22. Then, the magnetic field MR forms an upward magnetic domain 15B in the magnetic nanowire 10B, whose magnetization direction was downward, and a domain wall 16B is formed directly below the recording element 20. Note that Figs. 2A to 2C, 7A and 7B are schematic cross-sectional views, and the reproducing element is omitted.

[0018] (Drive current) The driving current ID is applied to the magnetic nanowire 10 to drive the magnetic domains. The magnetic domains are driven by applying a pulsed driving current ID to the magnetic nanowire 10. It is said that the magnetic domains can be driven when the current density of the driving current flowing through the magnetic nanowire 10 exceeds a certain value. The direction of the magnetic domain drive is determined by the direction of the electron e - The direction of movement of electron e - The direction in which moves is opposite to the direction of the drive current ID.

[0019] (Assist current) The assist current IA is a current that is applied to the recording element 20 and assists the magnetic domain drive. The assist current IA is applied together with the drive current ID. The assist current IA is applied so that the magnetic field at the position of the domain wall 16 is in the direction of magnetic domain drive. The assist current IA is smaller than the recording current IR and does not reverse the magnetization direction of the magnetic domain 15. Again, the case where there are two recording elements 20 will be described. In FIG. 2C, the direction of magnetic domain drive is to the right, and the magnetic nanowire 10A has an electron e - A driving current ID is applied such that the magnetic field moves to the right. Together with the driving current ID, assist currents IA1 and IA2 are applied to the first recording element 21 and the second recording element 22 in the same direction, perpendicular to the paper surface and from the back side to the front side. The directions of the magnetic fields MA of the assist currents IA1 and IA2 are both rightward at the positions of the two domain walls 16A.

[0020] By assisting the magnetic domain drive by the assist current IA, for example, the pinned magnetic domain wall 16 can be driven, and the drive current required for magnetic domain drive can be reduced. Such an assist effect tends to increase as the assist current IA is increased. For example, if the assist current IA is smaller than one-tenth of the recording current IR, no clear assist effect can be obtained. On the other hand, since the assist current IA is a current applied to the recording element 20, if it approaches the magnitude of the recording current IR, it may affect the magnetization direction. For this reason, the magnitude of the assist current IA can be set to 10% to 50% of the recording current IR, and preferably 20% to 40%. Note that with an assist current IA that is 50% of the magnitude of the recording current IR, the magnetization direction already formed in the magnetic domain 15 will not be reversed.

[0021] The assist current IA is preferably applied in synchronization with the driving current ID so as to rise simultaneously with or before the rising edge of the driving current ID, and is preferably applied throughout the time period during which the driving current ID is being applied. In other words, it is preferable that the time period during which the driving current ID is applied is included in the time period during which the assist current IA is applied. For example, the assist current IA can be applied in the form of a pulsed current having the same pulse width as the driving current ID, in synchronization with the rising edge of the driving current ID so as to rise simultaneously.

[0022] (Reproducing element) The reproducing element 40 is an element that converts the change in the magnetization direction of the magnetic nanowire 10 into an electric signal. The reproducing element 40 can be, for example, a magnetic head for a hard disk. Here, the reproducing element 40 is arranged so as to contact the upper surface of the magnetic nanowire 10. When magnetic domain driving is performed continuously, the magnetization direction of the magnetic domain 15 directly below the reproducing element 40 changes from moment to moment. The reproducing element 40 outputs the change in the magnetization direction of each magnetic domain 15 as an electric signal ES.

[0023] (Detection processing unit) The detection processing unit 50 is connected to the reproducing element 40, and is a device that converts the electrical signal ES from the reproducing element 40 into binary information or the like.

[0024] The magnetic nanowire memory device 1 having the above-mentioned configuration not only applies the driving current ID to the magnetic nanowire 10 in magnetic domain driving, but also applies the driving current ID to the magnetic nanowire 10 and the assist current IA to the recording element 20, thereby assisting the driving of the domain wall 16 with the magnetic field of the assist current IA, and reducing the driving current ID required for magnetic domain driving. Also, by applying the assist current IA without changing or by increasing the driving current ID, the speed of magnetic domain driving can be increased. Since the domain wall 16 directly below the recording element 20 is pinned, it may be difficult to drive the magnetic domain by applying only the driving current ID. If an attempt is made to drive the pinned domain wall 16 by increasing the driving current ID, the driving current ID may become excessively large, which may cause burning or breakage. By applying an assist current IA to the recording element 20, the magnetic nanowire memory device 1 can drive even the domain wall 16 directly below the recording element 20 with a normal driving current ID or an even lower driving current ID.

[0025] Next, an experiment that confirmed that the driving of the domain wall is assisted by the assist current will be described. This experiment was performed using an experimental device 100 in which a magnetic nanowire 10E, a recording element 20E, and an insulating film are formed on a silicon substrate. As shown in FIG. 3, the device 100 includes four parallel magnetic nanowires 10E and two parallel recording elements 20E that are perpendicular to the four magnetic nanowires 10E. One end of each of the four magnetic nanowires 10E is connected to one electrode 11E, and the other end is connected to one electrode 12E. The recording element 20E is disposed above the magnetic nanowire 10E, insulated by an insulating film formed on the magnetic nanowire 10E.

[0026] The magnetic nanowire 10E was formed by laminating three Co / Tb layers, with a 0.3 nm thick Co layer as the upper layer and a 0.55 nm thick Tb layer as the lower layer, on a 3 nm thick Pt layer. The magnetic nanowire 10E has a line width of 3 μm. The recording element 20E was formed by laminating a 90 nm thick Au layer on a 5 nm thick Ta layer. The recording element 20E has a line width of 4 μm. The insulating film is made of 18 nm thick SiO2. The magnetic nanowire 10E and the recording element 20E were formed on a surface thermally oxidized silicon substrate. First, in FIG. 3, recording currents in the opposite directions were applied to the two recording elements 21E and 22E to form magnetic domains. As a result, a downward magnetic field was formed between the recording elements 21E and 22E, and an upward magnetic field was formed in the magnetic nanowires 10E on the right and left sides of the two recording elements. Domain walls were formed under each of the two recording elements 21E and 22E.

[0027] Next, an experiment was conducted to see whether the domain wall could be driven by applying the driving current ID to the magnetic nanowire 10E and the assist currents IA1 and IA2 to the recording element 20E. The driving current ID was applied so that the direction in which electrons move was to the right. The assist currents IA1 and IA2 were applied in the same direction, from top to bottom in FIG. 3. FIG. 4 is a graph showing an example of an outline of the applied current waveform. In FIG. 4, the vertical axis represents the current density of the driving current and the assist current, and the horizontal axis represents time. Waveform W1 represents the driving current ID for the four magnetic nanowires combined, and waveform W2 represents the assist currents IA1 and IA2 for each recording element. The drive current and assist current were applied as pulsed currents with a pulse width of about 5 μs, rising and falling almost simultaneously. The current density I1 of the drive current was large enough to drive the magnetic domains if the magnetic domain walls were not pinned at the position of the recording element. The current density I2 of the assist current was set to two types: one that was about 1 / 4 the current density of the recording current for forming the magnetic domains, and one that was smaller than 1 / 10 the current density of the recording current.

[0028] It was confirmed that the domain wall 16E was driven to the right when the current density I2 of the assist current was set to about 1 / 4 of the recording current. FIG. 3 is a photo taken by a magneto-optical microscope after application of the driving current and the assist current when the current density I2 of the assist current was set to about 1 / 4 of the recording current. In FIG. 3, the domain wall 16E formed under the recording element 21E is driven to the area on the right side of the two recording elements. In addition, the moving distance of the domain wall 16E is larger than the distance between the centers of the two recording elements 20E, which is an indication of the width of the magnetic domain. On the other hand, when the current density I2 was set to less than 1 / 10 of the recording current, the domain wall 16E did not move from under the recording elements 21E and 22E. This result supports the fact that the effect of assisting the magnetic domain drive can be obtained by setting the current density of the assist current to 10% to 50% of the recording current. It was also found that by applying an assist current in addition to the drive current, the drive of the domain wall by the drive current is assisted, and the domain wall can be driven without increasing the drive current even when it is pinned at the position of the recording element.

[0029] [Magnetic domain driving method] Next, a magnetic domain driving method according to the embodiment will be described. The magnetic domain driving method according to the embodiment is a magnetic domain driving method for driving a magnetic domain formed in a magnetic wire 10, which is a thin-line magnetic material, in the extension direction of the magnetic wire 10, and includes applying a driving current ID to the magnetic wire 10 and applying an assist current IA smaller than the recording current to a recording element 20, which is a thin-line conductor arranged to be insulated from and cross the magnetic wire 10 and serves as a flow path of a recording current IR that magnetizes the magnetic wire 10, and applies the assist current IA in synchronization with the driving current ID. The magnetic domain driving method according to the embodiment can be performed, for example, in step S14 of the magnetic domain recording method S10. The magnetic domain recording method S10 is a method for recording a plurality of magnetic domains aligned in the extension direction of the magnetic nanowire 10.

[0030] The magnetic domain recording method S10 includes forming magnetic domains 15 in the magnetic nanowire 10 near the recording element 20, driving the formed magnetic domains 15, and forming the next magnetic domains 15 near the recording element 20, and repeating this process to form a row of magnetic domains 15 in the magnetic nanowire 10. Here, the case where there are two recording elements 20 will be described with reference to Figs. 5 to 6E. 5, the magnetic domain recording method S10 converts information to be recorded into magnetization information and sequentially sends it out (step S11), and when there is next magnetization information (step S12), it applies a recording current to the recording element to form magnetic domains (step S13), and then applies a drive current to the magnetic nanowire and an assist current to the recording element to drive the magnetic domains (step S14), repeating the steps. Note that the magnetization information is data in which values ​​of magnetization directions are arranged to correspond to binary information to be recorded, etc.

[0031] In step S11, the information to be recorded is converted into magnetization information. The magnetization information is a sequence of magnetization direction values, for example, either upward or downward. The magnetization direction values ​​are sent out one by one in sequence. The conversion into magnetization information is made in accordance with a reproduction method so that the magnetization direction values ​​can be detected by a reproduction element or the like and the original binary information or the like can be read out.

[0032] In step S12, it is determined whether there is magnetic information to be recorded in the next magnetic domain. If there is magnetic information, the process proceeds to step S13 to form the magnetic domain, and if there is no magnetic information, the magnetic domain recording method S10 ends.

[0033] In step S13, a recording current is applied to the recording element to form a magnetic domain. Here, as illustrated in FIG. 6A, the magnetic nanowire 10 is initialized so that the magnetization direction is upward. The magnetic domain is formed in a formation region 14, which is a region of the magnetic nanowire 10 between the two recording elements 21 and 22. Note that FIG. 6A to FIG. 6E are schematic plan views, and show that the magnetization direction UM is upward and the magnetization direction DM is downward. 6B, in forming a magnetic domain, recording currents IR1 and IR2 in mutually opposite directions are applied to two recording elements 21 and 22. Here, a magnetic domain 151 whose magnetization direction is downward is formed in the formation region 14.

[0034] In step S14, a driving current is applied to the magnetic nanowire and an assist current is applied to the recording element to drive the magnetic domain. The assist current is smaller than the recording current. Here, as shown in FIG. 6C, a driving current ID is applied so that the direction of electron movement is rightward, and the magnetic domain is driven to the right. Then, assist currents IA1 and IA2 in the same direction are applied to the two recording elements 21 and 22. The assist current is applied so as to be synchronized with the driving current. It is preferable that the synchronization is performed so that the time width for applying the driving current is included in the time width for applying the assist current. In step S14, the magnetic domain 151 whose magnetization direction is downward is driven rightward, and the next magnetic domain is formed in the formation region 14 whose magnetization direction is now upward. In the magnetic domain recording method S10, steps S13 and S14 are repeated until there is no next magnetization information.

[0035] For example, following step S14 in which magnetic domain 151 is driven, step S13 is performed a second time. As a result, magnetic domain 152 with a downward magnetization direction can be formed next to magnetic domain 151, as illustrated in Fig. 6D. Then, in the second step S14, magnetic domains 151 and 152 are driven to the right, and the magnetization direction of formation region 14 becomes upward again, as illustrated in Fig. 6E. In each of steps S13 and S14 which are repeatedly performed, the recording currents IR1 and IR2 are applied to the two recording elements in mutually opposite directions, and the assist currents IA1 and IA2 are applied to the two recording elements in the same direction.

[0036] In the magnetic domain recording method S10, the current control unit 30 can convert the input binary information string into a magnetic information string, control the recording current that forms the magnetic domain in the magnetization direction, and control the drive current and assist current that move the formed magnetic domain.

[0037] Step S14 may be combined with other magnetic domain forming methods, etc. Even when step S14 is combined with steps other than steps S11, S12, and S13, it is possible to assist the magnetic domain driving by the driving current ID and to perform the magnetic domain driving by suppressing the driving current ID.

[0038] The recording element 20 may be disposed below the magnetic nanowire 10, or may be disposed both above and below the magnetic nanowire 10 so as to sandwich the magnetic nanowire 10 therebetween. The assist current IA can also assist the driving of the domain wall 16 at or near the position where the magnetic nanowire 10 and the recording element 20 intersect. As illustrated in Figs. 7A and 7B, even when there is one recording element 20 or three or more recording elements 20, the magnetic domain driving can be assisted by applying an assist current IA such that the magnetic field at the position of the magnetic domain wall 16 is oriented in the direction of magnetic domain driving. In Fig. 7B, three recording elements 20 are arranged in parallel to each other. The same applies when four or more recording elements 20 are arranged in parallel to each other, and the magnetic domain driving can be assisted by applying an assist current IA in the same direction to the multiple recording elements 20. [Explanation of symbols]

[0039] 1 Magnetic nanowire memory device 10 Magnetic thin wire 15 magnetic domains 16 Domain wall 20 Recording element 30 Current control section 40 Regenerative element 50 Detection processing section 60 Insulating film 100 Equipment (for experiments) IR Recording Current ID Drive current IA Assist Current

Claims

1. a magnetic nanowire in which magnetic domains are formed in a nanowire-shaped magnetic body, and the magnetic domains are driven in an extension direction; a recording element which is a thin-line conductor arranged to be insulated from and cross the magnetic nanowire and serves as a path for a recording current that magnetizes the magnetic nanowire; a current control section that applies a drive current to the magnetic nanowire in driving the magnetic domain and also applies an assist current to the recording element that is smaller than the recording current and assists in driving the magnetic domain.

2. 2. The magnetic nanowire memory device according to claim 1, wherein the current control section applies the assist current so as to be synchronized with the drive current.

3. The recording elements are arranged in parallel to each other, The magnetic nanowire memory device according to claim 1 , wherein the current control section applies the assist current in the same direction to a plurality of the recording elements.

4. The recording elements are arranged in two parallel rows, 2. The magnetic nanowire memory device according to claim 1, wherein the current control section applies the recording currents in mutually opposite directions to the two recording elements, and applies the assist current in the same direction to the two recording elements.

5. 5. The magnetic nanowire memory device according to claim 1, wherein the magnitude of the assist current is 10% to 50% of the magnitude of the recording current.

6. A magnetic domain driving method for driving a magnetic domain formed in a magnetic nanowire, which is a thin-line-shaped magnetic body, in an extension direction of the magnetic nanowire, comprising the steps of: A drive current is applied to the magnetic nanowire, applying an assist current smaller than the recording current to a recording element which is a thin-line conductor arranged to be insulated from and cross the magnetic nanowire and serves as a path of a recording current that magnetizes the magnetic nanowire; The magnetic domain driving method applies the assist current so as to be synchronized with the drive current.

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