JP2022181838A - Control method of magnetic thin wire device - Google Patents

Abstract

To provide a control method of a magnetic thin wire device capable of realizing an operation as a device by suppressing a leak current.SOLUTION: A control method of a magnetic thin wire device 1 comprising: a magnetic thin wire 10 that is a thin wire-shaped magnetic body; and a recording element 20 that is arranged to the magnetic thin wire via an inter-layer insulation layer 30 and records information into the magnetic thin wire as a magnetic domain by a current magnetic field. The recording element 20 includes two conductive parts which are crossed at a skew position with the magnetic thin wire 10, records the magnetic domain to a magnetic thin wire region nipped by the two conductive parts on the magnetic thin wire 10 at the time of recording, generates a predetermined potential difference between recording power supplies 41 and 42 so that a recording current capable of recording the magnetic domain flows in the recording element 20 and the potential difference between the magnetic thin wire 10 and the recording element 20 is reduced by the first recording power supply 41 and the second recording power supply 42 electrically connected to the recording element 20 at the time of recording, and applies a pulse voltage of a reverse coding to each conductive part from the pair of recording power supplies 41 and 42 connected to both ends of each conductive part.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method of controlling a magnetic wire device, and more particularly to a method of controlling a magnetic wire device that records information as magnetic domains by means of a current magnetic field.

Conventionally, a magnetic wire using a material having perpendicular magnetic anisotropy is known. For example, as magnetic nanowire materials, a multilayer structure of cobalt (Co) and terbium (Tb), which has been proven as a perpendicular magnetization film, and a multilayer structure of cobalt and palladium (Pd) have been used to realize magnetic domain has been reported to be successful in driving As a recording element (recording unit) in this type of magnetic wire device, a method of recording information by placing a conventional HDD recording head in contact with the magnetic wire has been considered. However, since the protective film of the recording head has a thickness of about several hundred nanometers, there are problems that the recording head cannot be placed on the magnetic nanowire as close as possible, and the recording head has a mechanically moving part such as a suspension. As a result, there is a problem such as misalignment during alignment.

Therefore, as in the magnetic nanowire device 101 shown in FIG. 15A, by arranging the magnetic nanowire 110 and the conductive wire (the recording element 120) so as to be in an orthogonal twist position with the interlayer insulating layer 130 interposed therebetween, these solves the problem of For the sake of clarity, it is assumed that all the magnetic wires 110 are pre-magnetized downward in the initial value.

FIG. 15(b) shows the principle of forming magnetic domains in a magnetic wire device of this structure. A current magnetic field (recording magnetic field H) is generated around the recording element 120 in a clockwise direction along the recording current A by causing a current (recording current A) to flow through the conductor (recording element 120 ). When the intensity of the current magnetic field is greater than the intensity of the anisotropic magnetic field of the magnetic nanowire 110 having perpendicular magnetic anisotropy, upward or downward magnetic domains can be formed on the magnetic nanowire 110 (magnetic domain recording). FIG. 15(c) schematically shows the spread of the recording magnetic field H in the cross section of the recording element 120 and the magnetic wire 110 and the state of the magnetic domain D formed. When the magnetic wire 110 is a perpendicular magnetization medium, the vector component in the film thickness direction of the recording magnetic field vector spreading concentrically around the recording element 120 mainly contributes to the magnetization reversal.

An evaluation system at this time is shown in FIG. 16 (device overhead view) and FIG. 17 (device cross-sectional view). A recording power supply 40 is connected to the recording element 120 , and a recording current (pulse voltage) can be applied to the recording element 120 . By changing the direction of the recording current (positive or negative of the current), upward and downward magnetic domains can be formed on the magnetic wire 110 . Specifically, it is assumed that one end 121 of the conducting wire (printing element 120) is connected to the terminal 40a of the recording power supply 40, and the other end 122 is grounded. One end (left end) of the magnetic wire 110 is connected to the terminal 51 a of the first driving power source 51 . The other end (right end) of the magnetic wire 110 is connected to the terminal 52 a of the second driving power source 52 . Reference numerals 40b, 51b and 52b are ground terminals, and reference numerals 40c, 51c and 52c are operation display units.
The recording power supply 40 applies a positive recording current (pulse voltage) to the recording element 120 when recording an upward magnetic domain, and a negative recording current when recording a downward magnetic domain (pulse voltage). A first drive power source 51 and a second drive power source 52 are connected to both ends of the magnetic wire 110, and the magnetic domains on the magnetic wire 110 can be moved (driven) left and right. When moving (driving) the magnetic domain to the right, it is realized by applying a driving current (pulse voltage) from the first driving power supply 51 to the second driving power supply 52 . Further, when moving (driving) to the left, it is realized by applying a driving current (pulse voltage) from the second driving power supply 52 to the first driving power supply 51 .

Conventionally, a method of using a conductive wire (metal wiring) provided perpendicular to a magnetic nanowire as a recording element has been widely practiced (see, for example, Non-Patent Document 1). In addition, in the recording magnetic field generated by a single recording element, the magnetic domain formed on the magnetic nanowire spreads in the longitudinal direction of the magnetic nanowire, making it difficult to form the minute magnetic domain, and the shape of the magnetic domain fluctuates. On the other hand, a conducting wire (recording element) straddles the magnetic nanowire twice, i.e., going forward and backward. A method of controlling the magnetic domain length by performing magnetic domain recording has been proposed (see Patent Document 1 and Non-Patent Document 2).

Japanese Patent Application Laid-Open No. 2020-27805

Tsuyoshi Kondo, 7 others, ``Position control technology for magnetic domain walls in Co/Ni wires and its application to magnetic shift registers'', Institute of Electronics, Information and Communication Engineers Technical Research Report, October 12, 2017, vol. 117, no.24, p. .13-16 Mayumi Kawana, 3 others, "Simulation of Magnetic Domain Formation in Magnetic Nanowires in Various Recording Device Shapes", Abstracts of Annual Meetings of the Magnetics Society of Japan, August 28, 2018, Vol. 42, P.109

In the magnetic wire device 101, the recording element 120 and the magnetic wire 110 must be electrically isolated, so an interlayer insulating layer 130 must be inserted between them. The interlayer insulating layer 130 needs to ensure insulation, but if it is thicker than necessary, the distance between the magnetic wire 110 and the recording element 120 increases, and the current magnetic field applied to the magnetic wire 110 increases. weakens. As a result, the recording current required for recording increases, and the application of a large current to the recording element 120 causes damage to the element. Therefore, it is desirable that the film thickness of the interlayer insulating layer 30 is small. However, by making the interlayer insulating layer 130 thinner, there is a possibility that part of the recording current may flow out to the magnetic wire 110 as a leakage current during recording. This leakage current causes the magnetic domains already formed on the magnetic wire 110 to be unintentionally driven during magnetic domain recording. Since magnetic domain recording and magnetic domain driving occur at the same time, the magnetic domains may expand during recording, increasing the minimum bit length.

In addition, in an element with a large leakage current, the magnetic domain to be recorded and the already formed magnetic domain are broken apart by Joule heat (the magnetic domain becomes a maze pattern), so magnetic domain recording itself becomes difficult. Suppression of leakage current is essential for stable magnetic domain recording. Since the film thickness of the interlayer insulating layer is very thin (for example, about ten and several nanometers), when a plurality of magnetic wires are manufactured on the same substrate, a leak current may occur due to the difference in variation between them.

In addition, in device fabrication, when fabricating the magnetic nanowire/interlayer insulating layer/recording element in that order on the substrate, the layered structure is formed through many processes such as pattern formation by electron beam lithography, material deposition by sputtering equipment, and resist stripping. The current situation is to form Therefore, due to yield problems during fabrication (thickness and uniformity of interlayer insulating layers, edge shape of magnetic wires and recording elements, non-uniformity of film thickness on the substrate, etc.), devices must be manufactured under conditions where leakage current does not occur. Even if you design It is most desirable to manufacture an element that can completely suppress leakage current, but if it is possible to suppress unnecessary leakage current by devising device control technology even in an element that generates leakage current, the problem of yield of the element can be solved. Furthermore, even defective devices can be utilized within a certain range.

The present invention has been made in view of the problems described above, and an object of the present invention is to provide a control method for a magnetic wire device capable of suppressing leakage current and realizing operation as a device.

In order to solve the above-described problems, a method for controlling a magnetic wire device according to the present invention includes: a magnetic wire, which is a magnetic material in the form of a wire; a recording element for recording information as a magnetic domain in a magnetic wire device, wherein the recording element has two conductive wire portions that intersect with the magnetic wire at a twisted position; A magnetic domain is recorded in the magnetic wire region sandwiched between the two conductor portions on the wire, and a recording current capable of recording the magnetic domain is generated by two or more recording power sources electrically connected to the recording element during the recording. A pair of recording power sources connected to both ends of the conducting wire, generating a predetermined potential difference between each recording power source so as to flow to the recording element and to reduce the potential difference between the magnetic wire and the recording element. Therefore, pulse voltages having opposite signs are applied to the lead portions.

ADVANTAGE OF THE INVENTION This invention has the outstanding effect shown below.
According to the control method of the magnetic wire device, it is possible to suppress the leak current from the recording element to the magnetic wire in the magnetic wire device and realize the device operation. In addition, it is possible to increase the possibility that even a device that cannot be used in the prior art as an element with a large leakage current can be utilized by suppressing the leakage current. Therefore, yield can be improved.

FIG. 2 is a schematic diagram of connecting a magnetic wire device and a power source according to an embodiment of the present invention. FIG. 2 is a schematic diagram of a magnetic wire device in which four magnetic wires used in an experiment are arranged in parallel and a power supply. FIG. 3 is a schematic diagram showing the cross section of the magnetic wire device in FIG. 2 and the connection of the power supply; FIG. 10 is a waveform diagram of a recording current flowing through the recording element when a pulse voltage is applied from the second recording power source to the recording element in Experiment 1; FIG. 5 is a waveform diagram of leakage current 1 and leakage current 2 that flowed through the magnetic nanowire when the recording current of FIG. 4 was passed through the recording element; FIG. 10 is a waveform diagram of a pulse voltage applied from the first recording power supply to the recording element in Experiment 2; FIG. 10 is a waveform diagram of a pulse voltage applied to the recording element from the second recording power supply simultaneously with the first recording power supply in Experiment 2; FIG. 10 is a waveform diagram of a recording current flowing through a recording element in Experiment 2; FIG. 10 is a waveform diagram of leakage current 1 and leakage current 2 that flowed through four magnetic wires in Experiment 2; 4 is a timing chart of voltages applied when repeating magnetic domain recording and magnetic domain driving on a magnetic wire device. FIG. 11 is a magneto-optic microscope image of magnetic domains generated in a magnetic wire device by repeating the timing chart of FIG. 10 ; FIG. 5 is a schematic diagram of a first modified example of the control method for the magnetic wire device according to the embodiment of the present invention; FIG. 10 is a schematic diagram of a second modified example of the control method for the magnetic wire device according to the embodiment of the present invention; FIG. 10 is a schematic diagram of a third modified example of the control method for the magnetic wire device according to the embodiment of the present invention; FIG. 15(a) is a schematic diagram of a magnetic nanowire device, FIG. 15(b) is a schematic diagram (overhead view) of magnetic domain recording on a magnetic nanowire, and FIG. 15(c) is a schematic diagram of magnetic domain recording on a magnetic nanowire. (cross-sectional view). FIG. 16 is a schematic diagram of connecting the magnetic wire device of FIG. 15 and a power supply; FIG. 17 is a schematic diagram showing the cross section of the magnetic wire device in FIG. 16 and the connection of the power supply;

[Method for controlling magnetic wire device]
A method of controlling a magnetic wire device will be described with reference to FIG. In this embodiment, the magnetic wire device 1 will be described as a memory.
The magnetic wire device 1 includes a magnetic wire 10 which is a fine wire-shaped magnetic body, a recording element 20 which is arranged in the magnetic wire 10 with an interlayer insulating layer 30 interposed therebetween and records information as a magnetic domain on the magnetic wire 10 by a current magnetic field, It has The recording element 20 has two conductive wire portions that intersect the magnetic wire 10 at a twisted position, and records a magnetic domain in a magnetic wire region sandwiched between the two conductive wire portions on the magnetic wire 10 during recording.
The method of controlling the magnetic wire device is such that, during recording, two or more recording power supplies electrically connected to the recording element 20 cause a recording current capable of recording the magnetic domain to flow through the recording element 20, and the magnetic nanowire 10 and A predetermined potential difference is generated between the recording power sources so as to reduce the potential difference with the recording element 20, and pulse voltages of opposite signs are applied to the conductor from a pair of recording power sources 41 and 42 connected to both ends of the conductor. do.

As shown in FIG. 1, the recording element 20 has a U-shaped structure in which two conductor portions are connected. It is Also, here, two recording power sources (first recording power source 41 and second recording power source 42) are used. It is preferable that the magnitudes of the pulse voltages applied from the pair of recording power sources 41 and 42 to the lead portions are equal. To reduce the potential difference between the magnetic wire 10 and the recording element 20 so that the current value of the current leaking from the recording element 20 to the magnetic wire 10 during recording is reduced to a current value that does not drive the magnetic domains on the magnetic wire 10. is preferable, and it is more preferable that the potential difference between the magnetic wire 10 and the recording element 20 is zero. Here, the magnetic domain on the magnetic wire 10 refers to a magnetic domain to be recorded on the magnetic wire 10 or a magnetic domain already recorded.

[Configuration of magnetic wire device]
Next, the detailed configuration of each part of the magnetic wire device 1 will be further described.
In this embodiment, as shown in FIG. 1, the magnetic wire device 1 has, as an example, one magnetic wire 10 and a recording element 20 having two conductor portions. In the magnetic wire device 1 , a recording element 20 is formed on the magnetic wire 10 with an interlayer insulating layer 30 interposed therebetween at a twisted position with respect to the magnetic wire 10 .

The magnetic wire 10 is a thin film, and is formed in a narrow wire-like shape with a thickness and a width that are small relative to its length. The thickness of the magnetic wire 10 can be, for example, 5 nm to 2 μm, the width can be, for example, 20 nm to 100 μm, and the length can be, for example, 100 nm to 500 μm. In the examples described later, the film thickness of the magnetic wire 10 is assumed to be on the order of several nanometers. The magnetic wire 10 is formed into the shape described above by electron beam writing, photolithography, etching, or lift-off. In order to use the magnetic wire 10 as a recording medium and record information at high density, it is preferable to use a magnetic material having perpendicular magnetic anisotropy as the material of the magnetic wire 10 . Examples of such materials include alloys such as Co--Tb, Co--Pd, Co--Cr, Co--Pt and Co--Cr--Pt, and rare earth metals and transition metals such as Tb--Fe--Co and Gd--Fe. and an alloy (RE-TM alloy), and a multi-layer laminated structure film composed of the above elements.

The recording element 20 is a conducting wire, and is a recording element conductive layer that forms a magnetic domain inside the magnetic wire 10 while being electrically isolated from the magnetic wire 10 . In the recording element 20 , a conductive wire portion is arranged orthogonally to the magnetic wire 10 at a twisted position so as to straddle the magnetic wire 10 twice. The ranges of thickness, width, length, etc. of the recording element 20 can be substantially the same as the ranges of thickness, width, length, etc. of the magnetic wire 10 . In the examples described later, the film thickness of the recording element 20 is assumed to be, for example, on the order of 100 nm.

As a material of the recording element 20, a general electrode material can be applied. Specifically, for example, metals such as Cu, Al, Au, Ag, Ta, Cr, and Co with good conductivity and alloys thereof can be used. As a method for forming the recording element 20, for example, an electrode material is formed into a film by a known method such as a sputtering method, an electron beam drawing or photolithography process, and a process such as an etching or lift-off method can be used.

Although the cross-sectional shape of the recording element 20 is circular in the example shown in FIG. 1, it may be rectangular. Moreover, the cross-sectional shapes of the recording element 20 and the magnetic wire 10 may be square, rectangular, polygonal, circular, elliptical, or the like.

The insulator forming the interlayer insulating layer 30 is made of a general insulator material. Examples of such materials include oxide films such as SiO ₂ and Al ₂ O ₃ , silicon nitride (Si ₃ N ₄ ) and MgF ₂ . The shape of the interlayer insulating layer 30 is not limited to the illustrated flat plate shape as long as it is stably supported on a substrate (not shown). For example, an insulating material may be filled between the recording elements 20 . Alternatively, the interlayer insulating layer 30 may be an insulating film in which an insulating material is spread around the recording element 20 .

[System configuration]
As shown in FIG. 1, the evaluation system 2 that controls the magnetic wire device 1 includes a first recording power supply 41, a second recording power supply 42, and a first driving power supply 51 and a second driving power supply 52. . In the system 2, the same components as those of the system 102 shown in FIG. In the first recording power supply 41 and the second recording power supply 42, reference numerals 41a and 42a denote terminals, reference numerals 41b and 42b denote ground terminals, and reference numerals 41c and 42c denote operation display portions. The first recording power supply 41 and the second recording power supply 42 are each connected to two terminals of the recording element 20 and can apply pulse voltages of opposite signs to each other.
The first recording power source 41 and the second recording power source 42 are connected to both ends of the conducting wire (the recording element 20) arranged in a U shape.

During recording, a pulse voltage is applied to the recording element 20 from the first recording power source 41, and a pulse voltage having the same amplitude and a sign opposite to that of the first recording power source 41 is applied from the second recording power source 42 at the same timing. do. The recording current flowing through the recording element 20 at this time is the voltage difference between the pulse voltage of the first recording power source 41 and the opposite sign of the pulse voltage of the second recording power source 42, and corresponds to the resistance value of the recording element 20. A recording current flows. At this time, the potential of the recording element 20 seen from the magnetic nanowire 10 is the sum of the pulse voltage from the first recording power supply 41 and the opposite sign of the pulse voltage from the second recording power supply 42, so it appears to be 0 V, that is, It has the same potential as the magnetic wire 10, and no leakage current flows. The magnitude of the recording voltages of the first recording power source 41 and the second recording power source 42 is a potential difference sufficient to flow a recording current. is not necessarily equal, as long as it is small enough to suppress , but is most desirable.

In this embodiment, as shown in FIG. 1, the recording element 20 is U-shaped (a shape in which one conductor wiring intersects the magnetic wire 10 twice in the process of reciprocating), which is folded at a portion other than directly above the magnetic wire 10 . is. With this configuration, it is possible to easily apply pulse voltages having the same amplitude and opposite signs to the first recording power source 41 and the second recording power source 42, and the recording element 20 and the magnetic wire 10. It is possible to make the potential difference of 0 V apparently.

[Magnetic wire device having a plurality of magnetic wires]
It is preferable that the magnetic wire device includes a plurality of magnetic wires 10 and two conductor portions of the recording element 20 intersect the plurality of magnetic wires 10 at twisted positions. The reason for this is that when a magnetic wire memory is realized in the future, it is expected that several million magnetic wires will be arranged in parallel. Then, the recording element is arranged so that the two conductor portions are orthogonal to these parallel magnetic wires, and the synthesized magnetic field generated in the gap between the two conductor portions causes the magnetic field to be recorded on all the parallel magnetic wires. A recording control is assumed in which magnetic domains having the same magnetization direction are recorded.

Therefore, in the following, in order to verify whether or not the same information can be recorded simultaneously in multiple magnetic wires as shown in FIG. , Experiment 2). In the system 2B shown in FIG. 2, the same components as those of the system 2 in FIG. A magnetic wire device 1B is different from the magnetic wire device 1 in FIG. 1 in that four magnetic wires 10 are provided. The recording element 20 is U-shaped, and the two conductors intersect each magnetic wire 10 twice at a twisted position, so that a composite magnetic field of currents (recording currents) flowing through the two conductors is generated. forms a magnetic domain between the two conductor portions. By shortening the distance (gap) between the conductor portions, the range of the synthesized magnetic field can be narrowed, and the length of the magnetic domain to be recorded can be shortened. From the viewpoint of recording density, it is desirable to shorten the gap. For example, by using electron beam lithography, it is possible to form a minute gap of about 40 nm to 100 nm. Experiments 1 and 2 will be described in order below.

(Experiment 1)
Four magnetic wires 10 arranged in parallel are formed on a surface thermally oxidized silicon substrate by sputtering. As the magnetic wire 10, one having perpendicular magnetization characteristics is used, and this time, a multilayer laminated film (film thickness 4.5 nm) of cobalt and terbium is deposited, and platinum is deposited thereon to make the total film thickness 7.5 nm. . Also, the width of the magnetic wire 10 at this time was set to 3 μm. The multilayer laminated film is composed of 5 pairs of alternately laminated layers of cobalt having a thickness of 0.3 nm and terbium having a thickness of 0.6 nm.

Silicon nitride was deposited to a thickness of 18 nm as an interlayer insulating layer 30 on the magnetic wire 10 . A U-shaped conductive wire (recording element 20) was formed thereon with a film thickness of 100 nm and a width of 3 μm. One of the U-shaped conductors is used as an outward path, and the other as a return path.

At this time, the gap between the conductor portions of the recording element 20 was set to 100 nm. The thickness of the interlayer insulating layer 30 is set to 18 nm, which is sufficient to ensure insulation between the recording element 20 and the magnetic wire 10 . However, an element with poor insulation caused by non-uniformity caused by the yield in the formation of a multi-layered device or the position on the substrate is selected. In this element, it is assumed that a leakage current is generated from the recording element 20 to the magnetic wire 10 during magnetic domain recording. The following experiment 1 was conducted using this device with poor insulation.

Experiment 1 is an experiment according to a comparative example for explaining the effects of the present invention, in which only the recording voltage application process is performed during magnetic domain recording. In Experiment 1, recording current was supplied from the second recording power supply 42 without using the first recording power supply 41 of FIG. According to experiments so far, in the magnetic wire 10 and the U-shaped recording element 20 configured as described above, when a current of about 100 mA flows through the recording element 20 in a state where there is no leakage current, the magnetic wire 10 It has been confirmed that magnetic domains can be recorded in Further, it has been confirmed by previous experiments that the magnetic domains of the four magnetic wires 10 arranged in parallel as shown in FIG.

FIG. 4 shows a recording current waveform when a recording current of 71.6 mA and 3 μs is applied from the second recording power source 42 to the first recording power source 41 to the recording element 20 . Note that the recording current can be observed by the second driving power source 52, for example. FIG. 5 shows the leak currents 1 and 2 that flowed through the interlayer insulating layer 30 to the magnetic wire 10 at this time. Here, the leakage current 1 is the leakage current that flows from the magnetic wire 10 to the first drive power source 51 side as shown in FIG. 3, and the leakage current 2 is the leakage current that flows from the magnetic wire 10 to the second drive power source 52 side. leakage current. Note that the current and voltage values described with reference to FIGS. 4 to 8 are values at 1.5×10 ⁻⁶ s.

As shown in FIG. 5, leak current 1 was 13 mA and leak current 2 was 15 mA. Among them, the magnitude of leakage current 2 (15 mA) was the same magnitude as the drive current for driving the magnetic domain of the magnetic wire 10 . Therefore, it was confirmed that the magnetic domain already formed on the magnetic wire 10 was driven to the right (toward the second driving power source 52) in FIG. In addition, an attempt was made to apply a recording current of 100 mA, which enables magnetic domain recording, from the second recording power supply 42, but the leakage current increased further, not only driving the magnetic domains but also causing the magnetic domains of the magnetic nanowire as a whole to form a maze pattern. , could not record the magnetic domain. Note that the maze patterning of magnetic domains is a phenomenon in which the magnetic domains of a magnetic nanowire are broken apart by Joule heat of leak current.

(Experiment 2)
Since magnetic domain recording could not be performed by the method of Experiment 1, two recording power supplies 41 and 42 were connected to both ends of the conducting wire (recording element 20), respectively, as shown in FIG. Then, the recording voltage (pulse voltage) shown in FIG. 6 was applied to the first recording power supply 41, and the recording voltage (pulse voltage) shown in FIG. 7 was applied to the second recording power supply 42 at the same time. These recording voltages have an amplitude of 7.5 V and a pulse width of 3 μs, but have opposite signs. That is, a recording voltage of −7.5 V was applied to the recording element 20 from the first recording power supply 41 and a recording voltage of +7.5 V was applied from the second recording power supply 42 . Although the pulse width is set to 3 μs here, it is not limited to this as long as the pulse width is sufficient for magnetic domain recording. However, it is desirable for magnetic nanowire devices to be able to record magnetic domains at high speed, and for that purpose, it is desirable that the pulse width be small.

At this time, the potential difference between the second recording power supply 42 (positive pulse power supply) and the first recording power supply 41 (negative pulse power supply) is 15 V, and the potential difference is generated. 1 A current is applied in the direction of the recording power supply 41 .
At this time, the potential difference between the magnetic wire 10 and the recording element 20 is the sum of the voltages of the first recording power supply 41 and the second recording power supply 42, and thus becomes 0V. Therefore, leakage current from the recording element 20 through the interlayer insulating layer 30 can be suppressed. The gap between the conductors of the recording element 20 is 100 nm, which is sufficiently long compared to the thickness of the interlayer insulating layer 30 (18 nm). No destruction of magnetic domains was observed.

FIG. 8 shows the waveform of the recording current actually flowing through the recording element 20 (the direction from the second recording power source 42 to the first recording power source 41 is positive). FIG. 9 shows the leak currents 1 and 2 that flowed through the interlayer insulating layer 30 to the magnetic wire 10 at this time. As shown in FIG. 8, a current of 108 mA (>100 mA) flows through the recording element 20, and it was confirmed that this recording current was sufficient to record the magnetic domain in each magnetic nanowire 10. was made. Further, as shown in FIG. 9, the leakage currents 1 and 2 at this time were about −3 mA to +3 mA, which was sufficiently lower than the driving current (15 mA) for driving the magnetic domains. Under the conditions of Experiment 2, the sufficiently suppressed leak current at which the magnetic domain of the magnetic wire 10 does not move is, for example, a current of 3.5 mA or less.

As an example, in the magnetic wire device 1, FIG. 10 shows a case where upward magnetic domain recording and driving of the magnetic domain recorded at that time and downward magnetic domain recording and driving of the magnetic domain recorded at that time are alternately repeated. will be described with reference to FIG. 10 is a timing chart when magnetic domain recording and magnetic domain driving on the magnetic wire device 1 are alternately repeated using the first recording power source 41, the second recording power source 42, and the second driving power source 52. An example.

In this example, during magnetic domain recording, during the period from time t0 to time t11, the recording element 20 is controlled so that the recording current flows from the second recording power source 42 toward the first recording power source 41. A positive pulse voltage was applied from the second recording power supply 42 and a negative pulse voltage was applied from the first recording power supply 41 .
During another magnetic domain recording, during the period from time t12 to time t13, the recording element 20 is controlled so that the recording current flows from the first recording power source 41 toward the second recording power source 42. A positive pulse voltage was applied from the first recording power source 41 and a negative pulse voltage was applied from the second recording power source 42 .

When the magnetic domain is driven (time t11 to time t12, time t13 to time t14), the first drive power source 51 is set to 0 V, and the second drive power source 52 is set to a negative pulse power source, as shown in FIG. A negative drive voltage (negative pulse voltage) was applied to the fine wire 10 from the second drive power source 52 . For example, during the magnetic domain driving period from time t11 to time t12, by applying a pulse voltage of 500 ns to the magnetic wire 10 three times, the drive current (14 mA, 500 ns drive current) directed from the first drive power source 51 to the second drive power source 52 current) was allowed to flow. In this method, even if there is a leak current from the recording element 20 to the magnetic wire 10, it can be used as a drive current. Here, a drive current of 500 ns is applied three times in order to drive the magnetic domain sufficiently to observe it with a magneto-optical microscope. You can freely choose the number of times. However, increasing the pulse width causes heating of the magnetic nanowire, so this can be avoided by reducing the pulse width and increasing the number of times of application.

When driving the magnetic domain, on the contrary, the second driving power source 52 is set to 0 V, the first driving power source 51 is used as a positive pulse power source, and a positive driving voltage (positive driving voltage) is applied to the magnetic wire 10 from the first driving power source 51 . Magnetic domains can be similarly driven by applying a pulsed voltage).

FIG. 11 is a magneto-optical microscope image of a magnetic nanowire in which upward magnetic domains and downward magnetic domains are alternately formed by repeating the timing chart of FIG. is enlarged and displayed. In the magnetic wire 10, a magnetic domain is recorded in a magnetic wire region between the center of one (left in FIG. 11) conductor portion of the recording element 20 and the center of the other (right in FIG. 11) conductor portion. Each of the four magnetic domains D is a magnetic domain driven rightward from directly below the recording element 20 . From the right end, it corresponds to the upward magnetic domain, the downward magnetic domain, the upward magnetic domain, and the downward magnetic domain.

The present invention is not limited to the above-described embodiments, and various modifications are possible.
(First modification)
Also, although a specific example in which the magnetic wire 10 contains Co—Tb as the magnetic material has been described, other materials having perpendicular magnetic anisotropy may be used. If the magnetic material constituting the magnetic wire device contains a material such as Tb that is oxidized by oxygen or moisture, the oxidation of the magnetic wire may make it difficult to drive the magnetic domain. Moreover, if the magnetization in the magnetic nanowire is lost due to the progress of oxidation, and magnetic domain recording becomes difficult, the function as a magnetic nanowire device will be lost. Therefore, depending on the type of magnetic material, it is preferable to enclose the magnetic wire device in a container that is sufficiently shielded from the outside air in order to prevent the magnetic wire device from being oxidized. A schematic diagram of this modification is shown in FIG. In the system 2C shown in FIG. 12, the same components as those of the system 2B shown in FIG. A container 60 for blocking outside air isolates the magnetic wire device 1B from the atmosphere. Reference numerals 60a, 60b, 60c, and 60d denote connectors, and these connectors enable the magnetic wire device 1B inside the container 60 to be energized while isolating the atmosphere outside the container 60. FIG. Also, the atmosphere 70 inside the container 60 that shuts off the outside air is filled with a dry nitrogen atmosphere or is in a vacuum. According to this modification, by preventing oxidation of the magnetic wire device, more accurate control and evaluation of magnetic domain recording and magnetic domain driving can be achieved.

(Second modification)
The number of recording power supplies used for controlling the magnetic wire device is not limited to two, and may be four as shown in FIG. In the system 2D shown in FIG. 13, the same components as those of the system 2 shown in FIG. In the third recording power source 43 and the fourth recording power source 44, reference numerals 43a and 44a denote terminals, reference numerals 43b and 44b denote ground terminals, and reference numerals 43c and 43c denote operation display portions. In the recording element of the magnetic wire device 1 shown in FIG. 13, the two conductor portions 20a and 20b are electrically separated. In this system 2D, the four recording power sources 41 to 44 are used so that recording currents flow simultaneously in opposite directions to the two conductor portions 20a and 20b of the recording element. pulse voltages of opposite signs are applied to the lead portions from a pair of recording power supplies connected to both ends of the wires. Specifically, pulse voltages of opposite signs are applied to the conductor portion 20a from the first recording power source 41 and the third recording power source 43 connected to both ends of the conductor portion 20a. At the same time, pulse voltages of opposite signs are applied to the conductor portion 20b from the second recording power source 42 and the fourth recording power source 44 connected to both ends of the conductor portion 20b. This system 2D can also achieve the same effect as this system 2 of FIG.

(Third modification)
The number of recording power supplies used for controlling the magnetic wire device may be three as shown in FIG. In the system 2E shown in FIG. 14, the same components as those of the system 2 shown in FIG. In this system 2E, three recording power sources 41 to 43 are used, and pulse voltages of opposite signs are generated from a first recording power source 41 and a second recording power source 42 connected to both ends of a conductor connected in the recording element 20. is applied to the conductor. The third recording power source 43 can be connected to any position other than both ends of the conductive wire portions connected in the recording element 20 . The recording voltage applied to the recording element 20 by the third recording power supply 43 depends on the voltages applied to the first recording power supply 41 and the second recording power supply 42, and the third recording voltage is applied from the end of the recording element 20 with respect to the total length of the conductive wire. It can be set according to the ratio of the length to the power source 43 . This system 2E can also have the same effect as this system 2 of FIG.

Although the magnetic wire device 1 is assumed to be a memory, it may be a spatial light modulator. In the case of a reflective spatial light modulator, the magnetic wire 10 is preferably one that can change the polarization state of incident light, that is, one that has a strong magneto-optical effect.

1, 1B magnetic wire device 2, 2B, 2C, 2D, 2E system 10 magnetic wire (magnetic substance)
20 recording element 20a conductor portion (recording element)
20b Conductor (recording element)
30 Interlayer insulating layer 41 First recording power supply (recording power supply)
42 second recording power supply (recording power supply)
43 Third recording power supply (recording power supply)
44 fourth recording power supply (recording power supply)
51 First drive power supply 52 Second drive power supply 60 Container for blocking outside air D Magnetic domain

Claims (9)

A control method for a magnetic wire device comprising: a magnetic wire that is a thin magnetic material; and a recording element that is arranged in the magnetic wire with an interlayer insulating layer interposed therebetween and records information as a magnetic domain on the magnetic wire by a current magnetic field. There is
The recording element has two conductor portions that intersect with the magnetic nanowire at a twist position, and records a magnetic domain in a magnetic nanowire region sandwiched between the two conductor portions on the magnetic nanowire during recording,
At the time of recording, two or more recording power sources electrically connected to the recording element allow a recording current capable of recording a magnetic domain to flow through the recording element, and a potential difference between the magnetic wire and the recording element is adjusted. A magnetic wire characterized in that a predetermined potential difference is generated between each recording power source so as to reduce the potential difference between the recording power sources, and pulse voltages having opposite signs are applied to the conductive wire portion from a pair of recording power sources connected to both ends of the conductive wire portion. How the device is controlled. The recording element has a U-shaped structure in which the two conductive wire portions are connected,
2. The method of controlling a magnetic wire device according to claim 1, wherein the pair of recording power sources are connected to both ends of the two conductive wire portions. 3. The method of controlling a magnetic wire device according to claim 2, wherein two recording power supplies are used. 4. The method of controlling a magnetic wire device according to claim 3, wherein the pulse voltages applied from the pair of recording power sources to the lead portions are equal in magnitude. The magnetic nanowire and the recording medium are arranged so as to reduce the current value of the current leaking from the recording element to the magnetic nanowire during the recording to a current value that does not drive the magnetic domain to be recorded on the magnetic nanowire or the magnetic domain already recorded on the magnetic nanowire. 5. The method of controlling a magnetic wire device according to claim 3, wherein a potential difference with the element is reduced. In the recording element, the two conductor portions are electrically separated,
A pair of recording power supplies connected to both ends of the conductors of the recording element so that recording currents flow simultaneously in opposite directions to the conductors of the recording element. 2. The method of controlling a magnetic wire device according to claim 1, wherein pulse voltages having opposite signs are applied from a recording power source to said conductor portion. The magnetic wire device includes a plurality of the magnetic wires,
7. The magnetic field according to any one of claims 1 to 6, wherein the recording element is configured such that two of the conductor portions intersect with a plurality of the magnetic wires at twisted positions. Control method for thin wire devices. 8. The method of controlling a magnetic wire device according to claim 1, wherein the magnetic wire device is a memory or a spatial light modulator. 9. The method of controlling a magnetic wire device according to claim 8, wherein the magnetic wire device is enclosed in a container that can be kept in a dry nitrogen atmosphere or in a vacuum while being isolated from the outside air.

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