Storage device, storage medium, and manufacturing method thereof

Abstract

To provide a storage device that writes data transmitted by communication pulsed light by the communication pulsed light.SOLUTION: An electric field is applied by radiating communication pulsed light to a photosensitive magnetic fine wire whose temperature is raised by irradiation with a unit light pulse to change a magnetization direction to a direction of an external magnetic field and whose domain wall moves when the electric field is applied. Since the magnetization direction is changed by the communication pulsed light itself, writing can be performed at the speed of optical communication, and an amount of power required for writing is reduced. When necessary, a plurality of magnetic fine wires are selectively used according to chronological order, a multiple-bit simultaneous reading technique is also used. It becomes possible to read at the speed of optical communication.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This specification discloses a storage device and a storage medium that can be written with pulsed light for communication, and a method for manufacturing the storage medium.

[0002] As used herein, the following terms have the following meanings: Pulsed light for communication: Pulsed light that flashes or changes brightness in response to data. It has a high communication speed of 1 Gbps or more, and the light intensity of the bright pulse can be as weak as mW or less. Optical fiber for communication: Refers to optical fiber through which pulsed light for communication passes. This is a general term for not only the optical fiber that constitutes the infrastructure, but also the optical fiber used for optical communications in homes, vehicles, devices, equipment, systems, etc. Pulsed light that has passed through a communication optical fiber: Multiple types of communication pulsed light with different frequencies or multiple types of communication pulsed light with different polarization planes may pass through a communication optical fiber. In this specification, light obtained by dispersing the superimposed light that has passed through a communication optical fiber according to wavelength, polarization plane, etc. is referred to as pulsed light that has passed through a communication optical fiber. Pulsed light that has passed through a communication optical fiber is a type of communication pulsed light. However, optical fiber may not be used in short-distance optical communication systems, and communication pulsed light that does not pass through a communication optical fiber also exists. Magnetic nanowire: A nanowire made of a material in which magnetic domains move within the material when an electric field is applied (it can also be said that the pair of magnetic domain walls that define the magnetic domains move). In some cases, an applied electric field causes a current to flow, while in other cases, a potential difference is applied via an insulator, so no current flows even when an electric field is applied. Some are made of a single alloy film, while others are made of a laminate of multiple types of films. Photosensitive magnetic nanowire: Among the magnetic nanowires mentioned above, whose magnetic domains move when an electric field is applied, this refers to a magnetic nanowire in which the magnetization direction of the irradiated region changes to the direction of the external magnetic field when irradiated with a unit bright pulse included in pulsed light for communication. The magnetic nanowire itself may be made of a photosensitive material (a material in which the magnetization direction changes when irradiated with a unit bright pulse is called photosensitive), or it may be composed of a combination of a photosensitive material and a magnetic nanowire magnetically coupled to that material. In the latter case, the magnetic nanowire may or may not be photosensitive. Memory device: A memory device equipped with a light-sensitive magnetic nanowire, an electric field application device, and a writing device, capable of writing data transmitted by pulsed light for communication (for example, a time-series change pattern of bits such as 1,1,1... or 1,0,1...) into the magnetic nanowire. Storing the data is important, and there are cases where it is not necessary to read the data when writing it. A data reading device can be added when necessary and is not essential to this memory device. Unit bright pulse: This refers to the bright pulse with the shortest duration contained in pulsed light for communication, and its duration is called the unit bright pulse time. Since multiple unit bright pulses may occur in succession, the actual duration of a bright pulse may be a multiple of the unit bright pulse time. Unit dark pulse: This refers to the dark pulse with the shortest duration contained in pulsed light for communication, and its duration is called the unit dark pulse time. The unit dark pulse time may be equal to or different from the unit light pulse time. Since multiple unit dark pulses may occur in succession, the actual duration of a dark pulse may be a multiple of the unit dark pulse time. Unit pulse: A general term for unit bright pulse and unit dark pulse. [Background technology]

[0003] There has been active research into technologies for writing data into magnetic nanowires. Typically, data is written by using a method that uses a magnetic field generated by an electric current to reverse the magnetization direction over a partial length range of the entire length of the magnetic nanowire, and by controlling whether or not to reverse the direction in a time series. If this technology is used to write data transmitted by pulsed light for communication into a magnetic nanowire, it is necessary to switch on and off the current according to the changing pattern of brightness and darkness of the pulsed light for communication, which requires a photoelectric conversion process and requires a large amount of power for the writing process. Data cannot be written into a magnetic nanowire using the pulsed light for communication itself.

[0004] In Non-Patent Document 1, the magnetization direction is reversed by irradiating a portion of a magnetic nanowire with laser light. This technology requires irradiation with high-intensity laser light for an extremely short period of time in order to reverse the electron spin direction by utilizing the magnetic term inherent in the laser light, and a femtosecond laser with an output of up to 100 kW is used. The repetition rate of femtosecond lasers is slow, with a data writing speed of 0.1 bps. This technology cannot reverse the magnetization direction using communication pulsed light with an intensity of less than mW. It also cannot support communication speeds of 1 Gbps or more. [Prior art documents] [Non-patent literature]

[0005] [Non-Patent Document 1] Integrating all-optical switching with spintronics, MLM Lalieu, R. Lavrijsen & B. Koopmans, Nature Communications (2019) 10:110 Summary of the Invention [Problem to be solved by the invention]

[0006] The above technology does not allow data to be written to a magnetic nanowire using pulsed light for communication. However, the inventors' research revealed that, by selecting the type and specifications of the magnetic nanowire, a phenomenon can be achieved in which the magnetization direction of the irradiated region changes to the direction of an external magnetic field when the magnetic nanowire is irradiated with a unit bright pulse contained in pulsed light for communication. That is, it was confirmed that there exists a magnetic nanowire in which the magnetization direction of the irradiated region changes to the direction of an external magnetic field due to the heating effect when the pulsed light for communication is "bright," but does not change when the pulsed light is "dark." In this specification, a magnetic nanowire whose magnetization direction after irradiation with a unit bright pulse changes from the magnetization direction before irradiation is referred to as a photosensitive magnetic nanowire. This specification discloses a device that writes data transmitted by a communication pulsed light into a magnetic nanowire in a time-series manner by combining a photoinduced phenomenon in which the magnetization direction is changed by a communication pulsed light with a phenomenon in which magnetic domains are moved along the length of the magnetic nanowire. It also discloses a storage medium and a method for manufacturing the same.

[0007] Depending on the conditions under which the laser beam is irradiated onto the magnetic nanowire, the magnetic nanowire can be locally heated, instantly generating a large temperature gradient along and / or perpendicular to the film surface of the magnetic nanowire, generating a large amount of thermoelectron current along this temperature gradient. This thermoelectron current has spin and becomes a thermal spin current. The STT (spin transfer torque) and SOT (spin orbit torque) generated by this thermal spin current facilitate the phenomenon of changing the magnetization direction to the direction of an external magnetic field. Utilizing the thermal spin current makes it possible to reduce the intensity of the unit bright pulse required to change the magnetization direction. To effectively utilize the thermal spin current, the combination of materials and thickness of the magnetic layer and heavy metal layer are important. This technology can be applied to change the magnetization direction using a weak unit bright pulse, utilizing the thermal spin current flowing along the temperature gradient. [Means for solving the problem]

[0008] The storage device disclosed in this specification comprises a photosensitive magnetic nanowire, an electric field application device, and a writing device. The photosensitive magnetic nanowire has the property that when irradiated with a unit bright pulse contained in optical pulse light for communication, the magnetization direction of the irradiated region changes to the direction of an external magnetic field, and when an electric field is applied, the magnetic domains move in the longitudinal direction. The magnetic domain movement here refers to the magnetic nanowire itself being stationary, and the magnetic domains moving within the stationary magnetic nanowire. The electric field application device applies an electric field to the magnetic nanowire. While applying an electric field can sometimes cause a current to flow through the magnetic nanowire, in other cases, a potential difference is applied via an insulator, preventing current from flowing even when an electric field is applied. The magnetic domain migration speed can be adjusted by adjusting the electric field strength or current density.

[0009] The writing device uses the unit bright pulses contained in the communication pulsed light and an external magnetic field to change the magnetization direction of the irradiated region of the photosensitive magnetic nanowire to the direction of the external magnetic field. That is, when the communication pulsed light is bright, the temperature rises when irradiated with the bright pulsed light, and the magnetization direction of the irradiated region changes to the direction of the external magnetic field. The magnetization direction may also be changed using the thermal spin current described above. On the other hand, when the communication pulsed light is dark (the intensity of the pulsed light is zero or weak), the temperature does not rise to a temperature that changes the magnetization direction.

[0010] To change the magnetization direction of a magnetic nanowire, a technique of directly irradiating a light pulse onto the photosensitive magnetic nanowire or a technique of irradiating a material magnetically coupled to the magnetic nanowire with light pulse may be used. If the material is heated by irradiation with a unit bright pulse, causing a phenomenon in which the material changes its magnetization direction to match the external magnetic field, this change in magnetization direction can be propagated to the magnetic nanowire, and the magnetization direction of a portion of the magnetic nanowire can be reversed to match the external magnetic field.

[0011] In this technology, the magnetization direction before being changed to the direction of the external magnetic field must be oriented in a direction different from that of the external magnetic field. The configuration for this is not particularly limited, and the magnetic nanowire may be magnetized in the different direction along its entire length, or the magnetic nanowire may be made to pass through an initial magnetization device before passing through a writing device, and then magnetized in the different direction by the initial magnetization device. In this specification, changing the magnetization direction from a direction different from that of the external magnetic field to the direction of the external magnetic field may be referred to as reversing the direction of the external magnetic field.

[0012] In the storage device disclosed in this specification, the relationship is set as follows: "magnetic domain migration speed" > "unit reversed magnetic domain length / (unit bright pulse time + unit dark pulse time)." The magnetic domain migration speed here refers to the average migration speed of magnetic domains calculated over the total time obtained by adding up the unit bright pulse time and the unit dark pulse time. When the magnetic domain migration speed changes within the unit bright pulse time (for example, when an electric field is intermittently applied to a magnetic nanowire, magnetic domains move intermittently), or when the magnetic domain migration speed changes within the unit dark pulse time, it refers to the average migration speed within the total time. When this speed condition is met, a non-reversed magnetic domain remains between two adjacent reversed magnetic domains, sandwiching the minimum non-reversed magnetic domain that serves as the unit, and the non-reversed magnetic domain does not disappear.

[0013] The unit reversed magnetic domain length here refers to the distance along the length of the magnetic nanowire in the region where the magnetization direction is reversed by irradiation with a unit bright pulse. It may differ from the unit non-reversed magnetic domain length described below, and may also differ from the unit magnetic domain length. Unless otherwise specified, the length referred to in this specification refers to the distance along the length of the magnetic nanowire.

[0014] If necessary, a reading device can be added to this storage device. As will be described later, the reading device requires electrical signal processing, and if the communication speed of the communication pulsed light is high, it is difficult to complete the reading process within the light-dark change period. In the case of this storage device, as will be described later, the effective reading speed can be increased by simultaneously using multiple magnetic nanowires and multiple magnetization direction detection devices, and the communication speed of the communication pulsed light, the writing speed, and the effective reading speed can be matched. For example, data transmitted by the communication pulsed light can be relayed, transmitted, and transferred to an external device such as a hard disk.

[0015] It is also possible to distribute and transfer the arrangement of magnetic domains written in one magnetic nanowire to multiple transfer magnetic nanowires. For example, three transfer magnetic nanowires can be used, with bits 1, 4, 7... stored in the first transfer magnetic nanowire, bits 2, 5, 8... stored in the second transfer magnetic nanowire, and bits 3, 6, 9... stored in the third transfer magnetic nanowire. This also extends the time available for reading data.

[0016] The technology disclosed in this specification provides a variety of new storage media. For example, it provides a storage medium characterized by a focusing lens, thermal insulation, heat sink, etc. in relation to the temperature rise caused by a unit bright pulse, a storage medium equipped with multiple magnetic nanowires for dual or distributed data storage, and a new structure realizing multiple magnetic nanowires. It also provides a storage medium that realizes an M-RAM structure using a magnetization direction detection device and transistors that turn on and off depending on the magnetization direction. Furthermore, it also provides a method for manufacturing the storage medium. [Effects of the Invention]

[0017] The memory device disclosed in this specification combines the phenomenon of directly or indirectly reversing the magnetization direction of a portion of the length of a magnetic nanowire by raising the temperature with a pulsed light for communication (more precisely, a unit bright pulse), and the phenomenon of moving the magnetic domains along the length of the magnetic nanowire, to form an arrangement of reversed magnetic domains corresponding to a bright pulse and non-reversed magnetic domains corresponding to a dark pulse in the magnetic nanowire, and can store data transmitted by the pulsed light for communication in the magnetic nanowire. The technology allows data to be written directly or indirectly into the magnetic nanowire using pulsed light for communication, making it possible to support high-speed optical communication. Furthermore, the technology does not require a photoelectric conversion process, reducing the amount of power required to operate the storage device. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a schematic plan view of a storage device according to an embodiment. [Figure 2] FIG. 2 is a schematic cross-sectional view of the storage device of FIG. 1; [Figure 3] 2 is a timing chart illustrating the operation of the storage device of FIG. 1; [Figure 4] FIG. 2 is a diagram illustrating the relationship between a temperature rising region, an external magnetic field effective region, and a reversed magnetic domain. [Figure 5] FIG. 1 is a diagram illustrating the relationship between pulsed light and magnetic domains in a magnetic nanowire. [Figure 6] FIG. 10 is a diagram illustrating another example of an external magnetic field generating device. [Figure 7] FIG. 10 is a diagram illustrating another example of the external magnetic field generating device. [Figure 8] FIG. 2 is a schematic cross-sectional view of a storage medium according to an embodiment. [Figure 9] 1 is a diagram illustrating a magnetic nanowire, a temperature-rising region, and a reversed magnetic domain. [Figure 10] FIG. 1 is a diagram illustrating a temperature rise region and reversed magnetic domains when a heat sink is present. [Figure 11] 10A and 10B are diagrams illustrating another example of a temperature rise region and reversed magnetic domains when a heat sink is present. [Figure 12] 3A to 3C are diagrams illustrating the operation of the storage device according to the embodiment. [Figure 13] 1 shows the relationship between the power during writing and the voltage of the read signal. [Figure 14] The relationship between the current density and the magnetic domain motion speed in a magnetic nanowire is shown. [Figure 15] This shows the relationship between reception sensitivity and transfer speed (transfer rate). [Figure 16] This shows the relationship between transfer speed (transfer rate) and the power consumption required for data transfer. [Figure 17] Schematic perspective view of a storage device that uses four optical fibers. [Figure 18] FIG. 18 is a surface view of the storage device of FIG. [Figure 19] FIG. 17 shows the relationship between the irradiation area, the effective area of ​​the external magnetic field, and the magnetic nanowire of the storage device. [Figure 20] FIG. 10 is a perspective view of another example storage device that uses four optical fibers. [Figure 21] FIG. 21 is a rear view of the storage device of FIG. 20. [Figure 22] FIG. 21 is a surface view of the storage device of FIG. [Figure 23] FIG. 20 shows the relationship between the irradiation area, the effective area of ​​the external magnetic field, and the magnetic nanowire of the storage device. [Figure 24] 10A and 10B are a cross-sectional view and a plan view of a storage device according to a first modified example. [Figure 25] 10A and 10B are a cross-sectional view and a plan view of a storage device according to a second modified example. [Figure 26] 11A and 11B are a cross-sectional view and a plan view of a storage device according to a third modified example. [Figure 27] FIG. 10 is a perspective view of a storage device according to a fourth modified example. [Figure 28] FIG. 13 is a cross-sectional view of a storage device according to a fifth modified example. [Figure 29] FIG. 13 is a perspective view of a storage device according to a sixth modified example. [Figure 30] FIG. 13 is a plan view of a storage device according to a seventh modified example. [Figure 31] FIG. 13 is a plan view of a storage device according to an eighth modified example. [Figure 32] FIG. 13 is a plan view of a storage device according to a ninth modified example. [Figure 33] FIG. 23 is a plan view of a storage device according to a tenth modified example. [Figure 34] FIG. 20 is an explanatory diagram of the operation of the storage device of Modified Example 10. [Figure 35] FIG. 23 is a cross-sectional view of a storage device according to an eleventh modification. [Figure 36]FIG. 23 is a cross-sectional view of a storage device according to a twelfth modified example. [Figure 37] FIG. 23 is a cross-sectional view of a storage device according to a thirteenth modification. [Figure 38] FIG. 20 is a cross-sectional view of a storage device according to a fourteenth modification. [Figure 39] FIG. 22 is a schematic perspective view of a storage device according to a fifteenth modified example. DETAILED DESCRIPTION OF THE INVENTION

[0019] (First Example) FIG. 1 shows a plan view of a storage device 1 according to an embodiment, which includes a photosensitive magnetic nanowire, an electric field application device, a writing device, a reading device (reproducing device), and a switching device. In this embodiment, two photosensitive magnetic nanowires 2A and 2B, each of which is photosensitive, are alternately used. Hereinafter, the photosensitive magnetic nanowires 2A and 2B are abbreviated as magnetic nanowires 2A and 2B. The electric field application device includes two DC power supplies 15A and 15B, two switches 14A and 14B, two nonmagnetic conductors 4A and 4B, and a common nonmagnetic conductor 4. The writing device includes an external magnetic field generator 6 for initial magnetization and an external magnetic field generator 8 for writing, and utilizes an irradiation area 10 of pulsed light that has passed through a communication optical fiber. The reading device includes a sensor array 12A that simultaneously reads multiple bits of data written in the magnetic nanowire 2A, and a sensor array 12B that simultaneously reads multiple bits of data written in the magnetic nanowire 2B. In this embodiment, TMR sensors whose resistance value changes depending on the magnetization direction of the magnetic nanowire are arranged. The storage device of this embodiment also includes a control device 16, which transfers or relays data transmitted by the communication pulsed light to a hard disk drive HDD 17. The control device 16 controls the operation of power supplies 15A and 15B and switches 14A and 14B based on a clock signal contained in the communication pulsed light, and transmits data detected by the sensor arrays 12A and 12B to the HDD 17. The magnetic nanowires 2A and 2B are also part of an electric field application device, a writing device, and a reading device, respectively. The control device 16 and switches 14A and 14B, etc., form a switching device.

[0020] Fig. 2 shows a cross-sectional view, with the above components formed on a polycarbonate substrate 18. Each of the sensor arrays 12A and 12B has 16 TMR sensors arranged therein, and each sensor is connected to a control device 16, although some of the connections are not shown in Fig. 2. In Fig. 2, reference numeral 19 denotes a dielectric material, which fixes the sensor arrays 12A and 12B, magnetic nanowires 2A and 2B, external magnetic field generating films 6 and 8, etc. onto the substrate 18 and insulates them from one another. The drawings used in this application are for the purpose of technical explanation only, and details are omitted and dimensions may not be accurately shown.

[0021] When switch 14A is turned on, a current flows from DC power supply 15A, and the current flows from left to right through magnetic nanowire 2A. Magnetic nanowire 2A is preferably formed of an RE-TM ferrimagnetic material; in this example, a TbCoFe alloy was used. However, the material is not limited to this; it may be an alloy based on rare earth elements and 3d transition elements, or a multilayer film composed of rare earth elements and 3d transition metal elements. These are ferrimagnetic materials and are perpendicular magnetization films with the easy axis of magnetization perpendicular to the film surface. A multilayer film composed of a 3d transition metal and a noble metal, which forms a perpendicular magnetization film, may also be used. In these magnetic nanowires, not only do magnetic domains move when an electric field is applied, but also, when irradiated with a unit bright pulse contained in pulsed light for communication, the magnetization direction of the irradiated region changes to the direction of the external magnetic field and becomes fixed. Magnetic nanowire 2A is formed of a photosensitive material and is itself a photosensitive magnetic nanowire.

[0022] Spin transfer torque (STT) is required for the magnetic domain walls to move due to an electric current, and a heterostructure consisting of a magnetic layer and a heavy metal layer with a large spin-orbit torque (SOT) is desirable. While STT is the force that drives the magnetic domain walls caused by the spin of electrons flowing through the magnetic material, SOT drives the magnetic domain walls when the flow of electrons flowing through the heavy metal layer penetrates into the magnetic layer due to the influence of the heterointerface. On the other hand, when a magnetic nanowire is irradiated with laser light, it is locally heated, instantly creating a large temperature gradient in the film plane and perpendicular to it, and a large amount of thermoelectron current is generated along this temperature gradient. These thermoelectrons become a thermal spin current, which has spin. Recording magnetic domains can be easily formed by the STT and SOT created by this thermal spin current. Recording magnetic domains can be formed even with low laser power. To effectively utilize this thermal spin current, the combination of materials and thickness of the magnetic and heavy metal layers are important.

[0023] To enhance the light-induced temperature rise effect, it is best to increase the light confinement effect by placing optimal dielectric layers or light-reflecting films on the light-incident and light-transmitting sides of the magnetic nanowire. For this purpose, it is best for the magnetic nanowire to be thin enough to transmit light. To maximize the light confinement effect, it is best to have a configuration in which reflected light does not return to the light-incident side, or transmitted light does not come out.

[0024] To enhance the temperature-raising effect, it is important that the magnetic nanowire is not only able to confine light but also has thermal insulation properties. It is also advantageous to have an insulating structure that includes the substrate. For example, glass or plastic, which has low thermal conductivity, is good for the substrate. In the case of a Si substrate, it is also preferable that the substrate surface has a dielectric film of 100 nm or more.

[0025] When an electric field is applied to the magnetic nanowire 2A and a current flows through it, the magnetic domains and domain walls in the magnetic nanowire 2A move in the same direction as the current. The speed at which the magnetic domains and domain walls move can be adjusted by the current value. In this example, a current value that moves at a speed of 2500 m / sec is passed. The same applies to the magnetic thin wire 2B, and a duplicate description will be omitted. In this specification, to distinguish between multiple magnetic nanowires, capital letters are used as subscripts, and when describing phenomena common to multiple magnetic nanowires, the subscripts are omitted.

[0026] An external magnetic field generator 6 for initial magnetization (a magnetic field generating film in this embodiment) applies a downward magnetic field to the magnetic wire 2 with a strength greater than the coercive force of the magnetic wire 2 at room temperature. The external magnetic field generator 6 is magnetically coupled to the left end of the magnetic wire 2, and aligns the magnetization direction of the magnetic domains moving from left to right in the magnetically coupled region downward.

[0027] An external magnetic field generator 8 for writing (a magnetic field generating film in this embodiment) applies an upward magnetic field to the magnetic wire 2, the strength of which is smaller than the coercive force of the magnetic wire 2 at room temperature but greater than the coercive force of the heated magnetic wire 2. The external magnetic field generator 8 is located downstream of the external magnetic field generator 6 in the direction of domain wall movement, and magnetic domains whose magnetization directions have been aligned downward by the external magnetic field generator 6 are magnetically coupled to the external magnetic field generator 8. The external magnetic field generator 8 is located inside the irradiation area 10 of the communication pulsed light, and a region heated by irradiation with a unit bright pulse of the communication pulsed light is magnetically coupled to the external magnetic field generator 8. When a magnetic domain passes through the area magnetically coupled to the external magnetic field generator 8, if the magnetic domain has been heated by the bright pulse, the magnetization direction of the passing magnetic domain is reversed to upward; if the magnetic domain has not been heated by the dark pulse, the magnetization direction of the passing magnetic domain is not reversed and remains downward. As a result, the magnetization direction of the magnetic domains that pass through the magnetic coupling region with the external magnetic field generating device 8 during the irradiation of the bright pulse becomes upward, and the magnetization direction of the magnetic domains that pass through the magnetic coupling region during the irradiation of the dark pulse becomes downward, and data corresponding to the time-series change pattern of light and dark is written along the length of the magnetic nanowire 2.

[0028] Since the coercivity of the magnetic nanowire 2 decreases with increasing temperature, the magnetization direction of the magnetic nanowire reverses when the temperature reaches a point where the coercivity equals the "strength of the external magnetic field." Hereinafter, unless otherwise specified, the external magnetic field for writing will be abbreviated as the "external magnetic field." In this specification, the temperature at which the relationship of coercivity equals the "strength of the external magnetic field" is referred to as the reversal temperature. The reversal temperature can be selected depending on the material of the magnetic nanowire, and the heat dissipation or heat insulation of the magnetic nanowire can be adjusted by the elements placed around the magnetic nanowire. Therefore, the magnetic nanowire can be set to heat up to the reversal temperature within the unit bright pulse time (40 psec in this example). In this specification, the required temperature rise time is the time from the start of bright pulse irradiation until the reversal temperature is reached and the reversal occurs 38 psec after the start of bright pulse irradiation. In this case, the required temperature rise time is 38 psec. After the required temperature rise time has elapsed, the length of the reversed magnetic domains increases as the domain walls move until the bright pulse ends.

[0029] Organize the meaning of terms. External magnetic field: Unless otherwise specified, this refers to the external magnetic field for writing, not the external magnetic field for initial magnetization. External magnetic field effective region: This refers to a region where the external magnetic field for writing that reverses the magnetization direction is dominant. Reversal temperature: The temperature at which the coercive force equals the strength of the external magnetic field. Heat-up region: The region that has been heated above the inversion temperature. It expands as the bright pulse elapses, and cools down and disappears within the unit dark pulse period. Heat-up time: The time from the start of bright pulse irradiation until the temperature reaches the inversion temperature

[0030] This technology utilizes the phenomenon of heating with bright pulsed light and reversing the direction of an external magnetic field, so the magnetization direction is reversed in the region where the heated region and the effective region of the external magnetic field overlap. When the temperature-rising region expands over time to include the external magnetic field effective region, the magnetization directions of the magnetic nanowires within the external magnetic field effective region reverse almost simultaneously at the point when the temperature-rising region expands to include the external magnetic field effective region. The distance along the length of the magnetic nanowire in this region where the magnetization directions reverse simultaneously is called the "simultaneous reversal length." When the temperature-rising region expands to include the external magnetic field effective region, the relationship between the "simultaneous reversal length" and the "length of the external magnetic field effective region" holds.

[0031] Even if the effective area of ​​the external magnetic field is large and the heated region expands during the duration of the bright light pulse, it may remain within the effective area of ​​the external magnetic field. In this case, the length of the reversed magnetic domain increases in accordance with the expansion of the heated region. In this case, the unit reversed magnetic domain length corresponding to a unit bright pulse is determined by the size of the heated region. Since the expansion rate of the heated region is usually faster than the domain migration rate, the unit reversed magnetic domain length is determined by the size of the heated region at the end of the bright pulse.

[0032] 1, the temperature rise region expands to include the effective region of the external magnetic field, and the distance along the length of the magnetic nanowire 2 in the region where the external magnetic field generator 8 reverses the magnetization direction upward is set to 100 nm. In addition, the single pulse duration of the communication pulsed light irradiating the irradiation region 10 is 40 psec, achieving a communication speed of 25 Gbps.

[0033] Figure 4 shows the temperature change when the start time of the unit bright pulse irradiation is set to zero. After 8 psec has elapsed, the region 40-8 that has risen to the inversion temperature is narrow, and the external magnetic field generator 8 does not reverse the magnetization direction upward. As time passes, the region that has risen to the inversion temperature increases. In this example, after 38 psec has elapsed, the region magnetically coupled to the external magnetic field generator 8 rises to above the inversion temperature. That is, the region magnetically coupled to the external magnetic field generator 8 is included in the heated region 40-38. As a result, after 38 psec has elapsed from the start time of the bright pulse irradiation, the magnetization direction of the region magnetically coupled to the external magnetic field generator 8 reverses almost simultaneously to the upward direction. The length of the inversion region at this time is 100 mm. The simultaneous inversion length = 100 mm. In this example, the pulse duration is 40 psec, and the bright pulse continues for 2 psec after reversal, during which time the magnetic domains continue to move. As mentioned above, in this example, a current value is passed through the magnetic nanowire that causes the domain walls to move at a speed of 2500 m / sec, so the reversed magnetic domains expand by 5 nm over the 2 psec period. As a result, a unit bright pulse forms a reversed magnetic domain 105 nm long. In this example, the unit reversed magnetic domain length is 105 nm.

[0034] When the temperature-rising region expands to include the external magnetic field effective region and reversals occur almost simultaneously throughout the external magnetic field effective region, the relationship is generally expressed as follows: Unit reversal domain length = simultaneous reversal length + magnetic domain movement speed × (bright pulse duration after the required temperature-rising time).

[0035] The heated region at the end of a unit bright pulse can be narrowed by using a focusing lens or the like to narrow the irradiation range of the pulsed light, or by placing a plasmon antenna or heat sink within the irradiation range. The magnetic domain size can also be reduced by miniaturizing the heated region. When miniaturizing the magnetic domain size by miniaturizing the heated region, there is no need to confine the effective region of the external magnetic field to a narrow region. In this case, the length of the heated region at the end of a unit bright pulse is the unit reversed magnetic domain length. Generally, the expansion rate of the heated region is faster than the magnetic domain migration rate, so the length of the heated region at the end of a unit bright pulse is the unit reversed magnetic domain length.

[0036] Figure 3 (2) shows an example of the time series change in brightness of pulsed light for communication, with 30A showing the shortest dark pulse and 32A showing the shortest bright pulse. Both pulse durations are equal, 40 psec in this example. 30B shows a dark pulse consisting of two consecutive shortest dark pulses, and 32B shows a bright pulse consisting of two consecutive shortest bright pulses. In the case of (2), a time series change of "bright, dark, light, light, dark, dark, light, dark..." is shown, and this is an example of the data referred to in this specification.

[0037] FIG. 5 shows the relationship between data and the magnetic domains and magnetization direction in the magnetic nanowire. (1) shows the case where the pulsed light changes from bright to dark, and (1a) shows the relationship between the magnetic domains and magnetization direction in the magnetic nanowire. Hatched magnetic domains indicate reversed magnetic domains that have reversed in the direction of the external magnetic field, while unhatched magnetic domains indicate non-reversed magnetic domains that have not been reversed by the external magnetic field. 51a indicates a reversed magnetic domain formed by the bright pulse 51, 52a indicates a non-reversed magnetic domain that remains in response to the dark pulse 52, 53a indicates a reversed magnetic domain formed by the bright pulse 53, and 54a indicates a non-reversed magnetic domain that remains in response to the dark pulse 54. Period T55 in FIG. 5(1) is the pulse time (40 psec in this example). Period T56 is the required temperature rise time (38 psec in this example). Period T57 corresponds to 38 to 40 psec in FIG. 4. Reversed magnetic domain 51a is formed within period T57. The length of the reversed magnetic domain 51a is the simultaneous reversal length (100 nm in FIG. 4 in this embodiment) plus the domain movement distance during period T57 (5 nm in this embodiment), and the unit reversed magnetic domain length in this embodiment is 105 nm. Period T58 corresponds to the period during which the magnetic domains are not reversed, and the length of this period is equal to the pulse time plus the required heating time. The length of the non-reversed region 52a is (pulse time + required heating time) × domain movement speed − "simultaneous reversal length," which is 95 nm in this embodiment. Note that the relationship is (pulse time + required heating time) × domain movement speed − "simultaneous reversal length" = (2 × pulse time) × domain movement speed − unit reversed magnetic domain length. As described above, the unit switched magnetic domain length in this example is 105 nm, and the unit non-switched magnetic domain length is 95 nm, which are different from each other.

[0038] Figure 5(2) shows the case where "dark-dark" occurs continuously. Period T'58 corresponds to the period during which the magnetic domains are not reversed by the continuous dark pulses, and the length of the corresponding non-reversed magnetic domain is (pulse time x 2 + required temperature rise time) x magnetic domain motion speed - "simultaneous reversal length," which is 195 nm in this example. Figure 5(3) shows the case where "bright-bright" occurs consecutively. Period T'57 corresponds to the period during which the magnetic domains are reversed by consecutive bright pulses, and the length of the corresponding reversed magnetic domain is the simultaneous reversal length (100 nm in this example) plus the domain movement distance during period T'57 (105 nm in this example), which is 205 nm in this example.

[0039] As shown in Figures 5(1a), (2a), and (3a), the domain wall position changes depending on the light and dark change pattern and is not constant, but it does not deviate significantly. For example, regardless of the light and dark pattern, position P1 is located within the magnetic domain corresponding to the first pulse 51, position P2 is located within the magnetic domain corresponding to the second pulse 52, position P3 is located within the magnetic domain corresponding to the third pulse 53, and position P4 is located within the magnetic domain corresponding to the fourth pulse 54.

[0040] By utilizing the above, it is possible to read multiple bits of data simultaneously in parallel. By placing a sensor that detects a value that changes depending on the magnetization direction of the first magnetic domain at position P1, a second identical sensor at position P2, a third identical sensor at position P3, and a fourth identical sensor at position P4, it is possible to read the magnetization directions of four magnetic domains simultaneously in parallel.

[0041] As mentioned above, in this embodiment, writing one bit takes 40 psec. In contrast, detecting the magnetization direction using a sensor that detects values ​​that change in response to the magnetization direction (e.g., Tunneling Magneto Resistive, TMR) requires 100 psec or more. If multiple sensors can read multiple bits simultaneously in parallel, the problem of each sensor's reading process being too slow to keep up with the communication speed can be solved.

[0042] In this embodiment, pulse time × magnetic domain motion velocity = 100 nm, which is equal to the spacing between the aforementioned positions P1, P2, P3, and P4. In this specification, pulse time × magnetic domain motion velocity = unit magnetic domain length. If sensors that detect different values ​​depending on the magnetization direction of the magnetic nanowire are arranged at intervals of the unit magnetic domain length, it becomes possible to read the magnetization directions of multiple magnetic domains simultaneously and in parallel.

[0043] The terms explained above will now be clarified. Unit magnetic domain length: Pulse time x magnetic domain movement speed. Unit domain length: The length of a unit reversed magnetic domain formed by a unit bright pulse. When forming a reversed magnetic domain, it may take time to heat up, regions may be formed that reverse almost simultaneously, or the heated region may have an extension, so it differs from the unit domain length. Unit non-reversed magnetic domain length: This refers to the length of a unit non-reversed magnetic domain that remains in response to a unit dark pulse. This length is (2 x pulse time) x domain migration speed - unit reversed magnetic domain length. If the phenomenon of almost simultaneous reversal occurs during the required heating time, it is equal to (pulse time + required heating time) x domain migration speed - "simultaneous reversal length." If the relationship is "domain migration speed" > "unit reversed magnetic domain length / (2 x pulse time)," a non-reversed magnetic domain will remain between two adjacent reversed magnetic domains, sandwiching the smallest non-reversed magnetic domain corresponding to the unit dark pulse, and the non-reversed magnetic domain will not disappear.

[0044] 12A in Fig. 1 shows a row of 16 TMR sensors, and the spacing between adjacent sensors satisfies the relationship of positions P1, P2, P3, etc. in Fig. 5. In other words, the spacing is set to the relationship of unit magnetic domain length. As shown in Figure 5 (1a) to (3a), the length of one magnetic domain can be 95 nm or 105 nm. The length of each magnetic domain is not necessarily unit domain length. However, if the sensors are arranged at intervals that satisfy the relationship of spacing = unit domain length, it is possible to obtain a positional relationship in which each sensor faces approximately the center of each magnetic domain. This makes it possible to simultaneously read the magnetization directions of multiple magnetic domains.

[0045] In this embodiment, data is written to 16 magnetic domains in magnetic wire 2A for 16 consecutive pulses. Data is then written to 16 magnetic domains in magnetic wire 2B for the next 16 consecutive pulses. The time required for each process is 40 psec × 16. In this embodiment, while writing data to 16 magnetic domains in magnetic wire 2B, the magnetization directions of 16 magnetic domains in magnetic wire 2A are read. Although processing by each sensor requires 40 psec or more, because 16 bits of data are read simultaneously in parallel, 16 bits of data can be detected within 40 psec × 16, and the read data can be relayed to HDD 17. Even though it takes time for each sensor to read the data, because 16 bits are read simultaneously in parallel, data can be relayed to HDD 17 at optical communication speeds.

[0046] Figure 3 shows a timing chart. (1) and (2) show the light and dark patterns of pulsed light for communication. For ease of understanding, the diagram shows the clock signal (1) and the data signal (2) separately, but in reality, a clock signal, data signal, clock signal, and data signal are sent in time series. In the diagram, the clock signal is shown as a single bit, but in reality, a multi-bit signal that follows a specified protocol is used as the clock signal.

[0047] In this embodiment, switch 14A is turned on at a predetermined timing (the arrival of the predetermined timing is determined using a clock signal), energizing magnetic wire 2A and starting the movement of the magnetic domain wall of magnetic wire 2A (see (3)). At this time, the magnetic domain wall of magnetic wire 2B does not move (see (5)). A light-dark pattern of communication pulsed light is written longitudinally along the magnetic wire 2A, along which the magnetic domain wall moves. After 16 × 40 psec has elapsed, current is applied for another predetermined time (34 in (3)) before the current to magnetic wire 2A is stopped. The predetermined time 34 is set to the time it takes for the last bit that passed through external magnetic field generator 8 to move to a position facing the most upstream sensor in sensor array 12A. When the current is stopped, 16 magnetic domains are stopped corresponding to the 16 sensors. During period 36, the magnetization directions of the 16 magnetic domains are read simultaneously and in parallel, and the read data is sent to HDD 17. Data may be sent to the HDD 17 in parallel or serial.

[0048] After writing 16 bits of data to the magnetic nanowire 2A, switch 14B is turned on to energize magnetic nanowire 2B, causing the magnetic domain wall of magnetic nanowire 2B to begin moving (see (5)). A light-dark pattern of the communication pulsed light is written lengthwise along the magnetic nanowire 2B as the domain wall moves. After 16 × 40 psec has elapsed, the current is applied for another predetermined time (38 in (5)) before being turned off. The predetermined time 38 is set to the time it takes for the last bit that passed through the external magnetic field generator 8 to move to a position facing the most upstream sensor in the sensor array 12B. When the current is turned off, the 16 magnetic domains are in a stopped state corresponding to the 16 sensors. After that, until data is written again to magnetic nanowire 2B (during this time, data is written to magnetic nanowire 2A), the magnetization directions of the 16 magnetic domains are read simultaneously and in parallel, and the read data is sent to HDD 17. Data may be sent to the HDD 17 in parallel or serial. Thereafter, the processing period of "writing data to magnetic wire 2A while reading data from magnetic wire 2B" and the processing period of "writing data to magnetic wire 2B while reading data from magnetic wire 2A" are alternated. Switches 14A, 14B, etc. constitute a switching device.

[0049] As described above, according to this embodiment, (1) Data can be written using weak communication pulse light of less than mW. (2) Data can be written using communication pulsed light, which changes brightness at high speed (1 Gbps or more). (3) No photoelectric conversion device is required for writing data. (4) The problem of data reading speed being slower than the data transmission speed can be addressed by using technology that reads multiple bits simultaneously in parallel. (5) To store data while reading multiple bits simultaneously, multiple magnetic nanowires are used in a time sequence. These features will be put to good use, realizing a new world of data storage.

[0050] The above is merely an example, and the present invention is not limited to the above examples. For example, (1) The magnetic nanowire is not limited to RE-TM ferrimagnetic materials. Any material can be used as long as it can be heated to the reversal temperature with a single pulse, reverses the direction of the external magnetic field when it exceeds the reversal temperature, and moves the magnetic domains (domain walls) when an electric field is applied, and can achieve the required magnetic domain movement speed. (2) The present invention is not limited to magnetic nanowires through which a current flows when an electric field is applied, but may be magnetic nanowires through which no current flows when an electric field is applied. (3) The present invention is not limited to magnetic nanowires in which the domain walls move in the longitudinal direction when a current is passed through the magnetic nanowire in the longitudinal direction. Magnetic nanowires in which the domain walls move in the longitudinal direction when an electric field is applied along the cross section of the magnetic nanowire may also be used. (4) The number of magnetic thin wires is not limited to two, but may be three or more. (5) There are cases where data can be recorded at the speed of optical communication, and data reading can be handled by other circumstances and technologies. In this case, the reading device can be omitted, and only one magnetic nanowire is required. (6) The number of bits that can be read simultaneously is not limited to 16 and may be more or less than this. (7) The magnetization direction detection sensor is not limited to a tunnel current detection sensor, and may be a magnetic sensor, a voltage sensor, a current sensor, or an optical sensor. (8) Depending on the optical communication protocol, the unit bright pulse time and the unit dark pulse time may differ. Even in this case, if the relationship is "magnetic domain movement speed" > "unit reversed magnetic domain length / (unit bright pulse time + unit dark pulse time)", a non-reversed magnetic domain will remain between two adjacent reversed magnetic domains, sandwiching the smallest non-reversed magnetic domain corresponding to the unit dark pulse, and the non-reversed magnetic domain will not disappear. (9) When writing data to a magnetic nanowire, the magnetic domain migration speed may change. For example, an electric field may be applied intermittently to the magnetic nanowire, causing the domain wall to move intermittently. In this case, the magnetic domain migration speed described in (8) above refers to the average migration speed of the domain wall calculated over the total time of the unit bright pulse time and the unit dark pulse time. (10) Instead of a magnetic material whose magnetization direction changes to the direction of an external magnetic field when heated above a holding temperature, it is possible to use a magnetic material whose magnetization direction is fixed to the direction of an external magnetic field when heated above a predetermined temperature and then cooled below that temperature. (Second Example)

[0051] As shown in Figure 6, the external magnetic field generator 8A for writing may be a composite film consisting of a magnetic film 8e that generates an upward magnetic field and magnetic films 8a, 8b, 8c, 8d, and 8f that are arranged around it and generate downward magnetic fields. The magnetic films 8a, 8b, 8c, 8d, and 8f that are arranged around it and generate downward magnetic fields narrow the area in which the upward magnetic field is generated in the magnetic nanowire 2, which is advantageous for minimizing the length of the reversed magnetic domains. A shorter magnetic domain length increases the amount of data that can be stored in a magnetic nanowire of the same length. It also slows down the speed at which the domain walls move. (Third Example)

[0052] 7, a DC power supply 8a and a non-magnetic conductor 8b constitute an external magnetic field generator 8 for writing. The conductor 8b crosses the magnetic wires 2A and 2B in an irradiation region 10 at a height perpendicular to the longitudinal direction of the magnetic wires 2A and 2B. An upward magnetic field is generated in the region to the right of the conductor 8b by the current flowing through the conductor 8b. The upward external magnetic field can reverse the magnetization direction of the magnetic nanowires 2A and 2B to the upward direction. This constitutes an external magnetic field generator 8 for writing. In the case of Figure 7, prior to writing data, the magnetic wires 2A and 2B are magnetized (magnetized) downward over their entire length. There is no limitation on the method for magnetizing them downward; they can be placed in a downward magnetic field with a strength equal to or greater than the coercive force. A downward magnetic field is generated in the region to the left of the conductive path 8b. Since the magnetic wires 2A and 2B are initially set downward, no particular problems arise. (Fourth Example)

[0053] 8 shows a cross section of the substrate 18, the magnetic nanowire 2, etc. This storage medium is stacked in the following order from the incident side of the pulsed light for communication 9: a light-intensity enhancing dielectric film 84, a thin protective film 83, the magnetic nanowire 2, a light-intensity enhancing dielectric film 82, a metal reflective film 81, and the substrate 18. The light-intensity enhancing dielectric film 84 is formed in the area irradiated with the pulsed light for communication 9, but is not formed in the area where the magnetization direction detection sensor array 12 is arranged. At the arrangement position of the magnetization direction detection sensor array 12, the distance between the detection sensor 12 and the magnetic nanowire 2 is shortened to increase detection sensitivity. The metal reflective film 81 reflects the pulsed light 9 that has passed through the magnetic nanowire 2 back toward the magnetic nanowire 2, allowing the weak (mW or less) pulsed light to heat the magnetic nanowire 2. The light-intensity enhancing dielectric film 84 and the light-intensity enhancing dielectric film 82 confine the communication pulsed light 9 between them, allowing the magnetic nanowire 2 to be heated by the weak communication pulsed light.

[0054] The storage medium of this embodiment not only incorporates optical innovations that effectively utilize weak communication pulsed light, but also takes into consideration thermal properties that make it easier to heat the magnetic nanowire 2 with weak communication pulsed light 9. In the region irradiated with the pulsed light 9, a thick light-intensity enhancing dielectric film 84 is used to improve heat insulation and make it easier to heat the magnetic nanowire 2. In contrast, in the data reading region where heat insulation is not required, the thick light-intensity enhancing dielectric film 84 is removed to increase detection sensitivity. (Fifth Example)

[0055] Figure 9 shows the case where one magnetic nanowire 2 is placed within the irradiation area 10 of the communication pulsed light. Curve 91 shows the temperature distribution in the transverse direction of the magnetic nanowire, and curve 92 shows the temperature distribution in the longitudinal direction of the magnetic nanowire. By utilizing the positional relationship in which the magnetic nanowire 2 passes near the center of the approximately circular temperature-raising area 40, the shape of the reversed magnetic domain 93 can be made approximately rectangular, and the occurrence of write and read errors can be suppressed. (Sixth Example)

[0056] 10 shows an example in which a heat sink 104 is added to the left of the temperature-rising region 40. In this case, as shown by curve 102, the temperature distribution in the longitudinal direction of the magnetic nanowire becomes asymmetric, and the temperature drops sharply from the center of the irradiation region 10 to the left. The temperature-rising region 40 spreads from the center to the right, but hardly to the left. As a result, the length of the unit reversed magnetic domain 103 becomes shorter. (Seventh Example)

[0057] 11 shows an example in which a heat sink 104 is added to the left side of the temperature rising region 40, and an external magnetic field effective region 118 is formed in a part of the right side region. As a result, the length of the unit reversed magnetic domain 113 becomes even shorter. (Eighth Example)

[0058] 12 shows an embodiment in which the operating frequency of the magnetization direction detector 12 is equal to the blinking frequency of the communication pulsed light 9. In this case, one magnetic nanowire 2 may be used. In this embodiment, a current is applied from a power source 15 to move the magnetic domains from left to right through the magnetic nanowire 2, and the magnetization direction of the magnetic nanowire 2 is set downward by the magnetized film 6 for initialization at the most upstream portion. The communication pulse light 9 passing through the optical fiber 123 is focused by a focusing lens 122 and irradiates the region magnetically coupled with the magnetized film 8 for writing. In this embodiment, the size of the heated region at the end of the unit bright pulse is approximately equal to the size of the external magnetic field effective region. Magnetic domains that were bright pulsed when they passed through the external magnetic field effective region are heated and the magnetization direction of the magnetized film 8 is reversed (upward). Magnetic domains that were dark pulsed when they passed through the external magnetic field effective region are not heated, so the magnetization direction of the magnetized film 8 is not reversed (upward) and maintains the downward magnetization direction. The magnetization direction detector 12 detects whether the magnetization direction is upward or downward for each magnetic domain it passes through and outputs the detection results in chronological order. This device can store data transmitted by communication pulsed light 9 in one magnetic nanowire 2 and can reproduce the recorded data. The magnetic nanowire 2 in this embodiment is a light-sensitive magnetic nanowire.

[0059] Figure 13 shows the power required for writing in the example shown in Figure 12 on the horizontal axis and the voltage of the read signal on the vertical axis. It shows that a signal with a detectable strength can be read as long as the power is -35 dBm or higher. This experiment was performed at 1 Gbps. Figure 14 shows the applied current density on the horizontal axis and the obtained magnetic domain motion speed on the vertical axis in the example of Figure 12. Increasing the current density increases the magnetic domain motion speed, and high-speed motion of 5000 m / sec or more can be achieved. In Figure 15, the horizontal axis represents receiver sensitivity and the vertical axis represents data transfer rate. Range 152 represents the case of conventional optical communications, while range 151 represents the case of the present technology. Performance improvements can be achieved with the present technology. In Figure 16, the horizontal axis represents the data transfer rate, and the vertical axis represents the power consumption required for transfer. Line 162 represents the case of conventional optical communications, while line 161 represents the case of this technology. This technology makes it possible to dramatically reduce power consumption.

[0060] By preliminarily giving the magnetic properties of a magnetic nanowire a spatial distribution, it becomes possible to drive the magnetic domains recorded on the magnetic nanowire with a lower current. For example, a heat treatment laser beam is focused on the center of the magnetic nanowire, and the focused beam is moved along the length of the magnetic nanowire. By performing this heat treatment in advance, the coercivity of the central part of the magnetic nanowire decreases, allowing the domain walls in the central part of the wire to be driven with a lower current density.

[0061] When a red laser with a wavelength of 690 nm is focused onto a GdFeCo magnetic nanowire with an objective lens numerical aperture (NA) of 0.5, a light spot of about 1 μm diameter is created on the nanowire. This is then continuously irradiated along the nanowire at a speed of 1 μm / sec. As a result, the coercivity at the center of the nanowire, which was 850 Oe before laser irradiation, decreased to 520 Oe. As a result, the domain wall driving current density with a pulse width of 3 nsec before laser irradiation was 3x10 11 A / m 2 , the domain wall motion velocity was 1900 m / sec, while the current density after laser irradiation was 0.5x10 11 A / m 2 The magnetic domain wall motion speed was increased to 3000 m / sec. The same phenomenon was confirmed by applying a current with a high current density to the magnetic nanowire in advance. 11 A / m 2 When the current was applied for 1 μs, the coercivity in the central part of the magnetic nanowire decreased to 680 Oe. This resulted in a domain wall driving current density of 1.8x10 11 A / m 2 The magnetic domain wall motion speed was increased to 2200 m / sec. 11 A / m 2 Even when this domain wall-driving current pulse was applied 100 times to the magnetic nanowire, the coercivity at the center of the magnetic nanowire remained at 850 Oe, indicating that applying a long pulse current with a high current density in advance is effective in improving the domain wall motion speed and reducing the driving current density. This discovery is extremely important for this proposal. The mechanism is thought to be that laser irradiation and application of a large current significantly reduce the variation in the initial magnetic properties when the magnetic nanowire is fabricated, and significantly reduce the number of pinning sites that hinder domain wall motion. Measurement of the spatial coercivity distribution in the magnetic nanowire is effective for evaluating this.

[0062] (Example 1) Fig. 17 shows memory devices for four optical fibers 171a, 171b, 171c, and 171d. Four sets of memory devices are formed on the light receiving surface (surface) of memory device 172, as shown in Fig. 18. Lowercase alphabetic subscripts indicate the correspondence, for example, 10a is the irradiation range for optical fiber 171a. In this embodiment, four magnetic nanowires 2A, 2B, 2C, and 2D are used per optical fiber. By using four magnetic nanowires, data written to one magnetic nanowire 2A can be read while data is being written sequentially to three magnetic nanowires, for example, the magnetic nanowires 2B, 2C, and 2D, which relaxes the time restriction on reading. There is no restriction on the number of magnetic thin wires used in one optical fiber, and it may be 11 or more as shown in FIG.

[0063] It is possible to magnetize all of the magnetic nanowires 2A to 2K downward before use, and once data has been stored in all of the magnetic nanowires 2A to 2K, the data can be stored in a new storage medium, in which case no magnetic field generator for initial magnetization is required. As shown in Figure 19, a conducting wire 4 for current application and an external magnetic field generator 8 for writing may be placed within the irradiation area 10.

[0064] As shown in Figures 20 to 22, it is possible to arrange condenser lenses 22a, 22b, 22c, and 22d on the front surface (surface irradiated with pulsed light) of a transparent substrate 173, and arrange magnetic nanowires 2 and the like on the back surface. In this case, using polycarbonate for the transparent substrate increases the magnetic domain movement speed. Furthermore, because it is a resin substrate, it can be manufactured inexpensively using nanoimprint technology, which will be described later.

[0065] Figure 23 shows the relationship between the temperature-rising region 40, the magnetic wire 2, and the non-magnetic conductive wire 4. In this example, the effective region of the external magnetic field is widely spread. As shown in Figure 23, the boundary between the magnetic wire 2 and the non-magnetic conductive wire 4 is located slightly inside the temperature-rising region 40. During manufacturing, a wiring pattern is formed by RE-TM not only in the area where the magnetic wire 2 is to be formed, but also in the area where the non-magnetic conductive wire 4 is to be formed. Then, an ion implantation process is performed on the portion that will become the non-magnetic conductive wire 4 to remove the ability of magnetic domain movement. By using the ion implantation method, the boundary between the magnetic wire 2 and the non-magnetic conductive wire 4 can be adjusted to a position slightly inside the temperature-rising region 40.

[0066] According to this embodiment, the magnetization direction of the magnetic wire 2 is reversed at a portion 2α where the magnetic wire 2 enters the temperature-rising region 40. The portion 2α where the magnetic wire 2 enters the temperature-rising region 40 becomes the unit reversal magnetic domain length. The unit reversal magnetic domain length can be made smaller by adjusting the length of the portion 2α.

[0067] Figure 24 shows an example in which, instead of directly irradiating the magnetic nanowire with pulsed light for communication, the material magnetically coupled to the magnetic nanowire is irradiated with pulsed light for communication, causing the material to heat up due to the irradiation, resulting in a phenomenon in which the magnetization direction of the material is reversed by the temperature increase, and this reversal phenomenon is propagated to the magnetic nanowire. In the example of Figure 24, a photosensitive magnetic nanowire is formed by combining a material 242 in which the magnetization direction of the irradiated region of a unit bright pulse changes to the direction of an external magnetic field, and a magnetic nanowire 2 magnetically coupled to that material 242.

[0068] In Figure 24, 242 is a multilayer film that is often used in magneto-optical memory materials, and it comprises a recording layer and a memory layer. When the temperature rises above the holding temperature, the magnetization in the heated region reverses, and this reversal phenomenon propagates toward the outer periphery (propagating beyond the heated region toward the outer periphery). When the material is cooled below the holding temperature, the magnetization in the cooled region reverses again (returning to the initial magnetization direction), and this re-reversal phenomenon propagates toward the outer periphery. Reference numeral 242α indicates the region where the material 242 and the magnetic nanowire 2 are magnetically coupled, and the magnetization direction of the magnetic nanowire 2 is aligned with that of the portion 242α. The magnetic nanowire 2 and the material 242 are insulated by an insulating film 243, but the insulating film 243 is thin and does not interfere with the magnetic coupling.

[0069] In this embodiment, too, the changing pattern of light and dark pulsed light can be written to the magnetic nanowire 2 via the material 242. The length of the unit reversed magnetic domain can be adjusted by the length of the region where the material 242 and the magnetic nanowire 2 are magnetically coupled, and it is easy to adjust it to the desired length.

[0070] Figure 25 shows an example in which another magnetic nanowire 252 intersecting the magnetic nanowire 2 is used, and the added magnetic nanowire 252 is irradiated with pulsed light. The magnetic nanowire 2 and the magnetic nanowire 252 are connected by a non-magnetic conductive wire 254. This non-magnetic conductive wire 254 is a magnetic nanowire in which ions have been injected to make it unable to move magnetic domains. At the crossing point between the magnetic nanowire 2 and the magnetic nanowire 252, an insulating film 253 is interposed between them to prevent the formation of a short circuit.

[0071] The magnetic nanowire 252 is magnetized downward along its entire length. When a bright pulse is irradiated onto the irradiation region 10, its center is heated above its coercive temperature. Because the magnetic nanowire 252 around the heated region is magnetized downward, a magnetic field leaking from the surrounding magnetic nanowire 252 is applied to the heated region. An upward magnetic field is generated at the center of the downward magnetic field. As a result, an upward external magnetic field acts on the heated region, reversing its magnetization direction to an upward direction. In this embodiment, the downward magnetized magnetic nanowire 252 also serves as an external magnetic field generator, and this leaking magnetic field is used to reverse the magnetization direction of the heated region. When a dark pulse is irradiated, no heated region is formed, and no reversal phenomenon occurs.

[0072] In this embodiment, an arrangement of magnetic domains whose magnetization direction is reversed in response to the changing pattern of the brightness of the pulsed light is formed in the magnetic wire 252, and this arrangement moves downward and passes through the three-dimensional intersection with the magnetic wire 2. When passing through the three-dimensional intersection, the magnetization direction of the magnetic wire 252 is transferred to the magnetic wire 2. As a result, an arrangement of magnetic domains whose magnetization direction is reversed in response to the changing pattern of the brightness of the pulsed light is formed in the magnetic wire 2, and this arrangement moves from left to right. According to this embodiment, the length of the unit reversed magnetic domain formed in the magnetic nanowire 2 can be adjusted by the shape of the part where the magnetic nanowire 252 and the magnetic nanowire 2 cross over each other, making it easy to adjust to a desired length. Although the magnetic nanowire 252 in this embodiment is a light-sensitive type, the magnetic nanowire 2 does not have to be a light-sensitive type.

[0073] In Figure 26, a non-magnetic conductor 264 crosses the magnetic nanowire 2 at an intersection. An external magnetic field for writing is generated by the non-magnetic conductor 264, and a current is passed through the non-magnetic conductor 264 and the magnetic nanowire 2 to move the domain wall in the magnetic nanowire 2. The center of the pulsed light is on the right side of the intersection, and heats the magnetic nanowire 2 located on the right side well. On the right side of the intersection, the current flowing through the non-magnetic conductor 264 generates an external magnetic field pointing upward. In this example, when a bright pulse is applied, the temperature rises in the region to the right of the intersection, causing the magnetization direction to reverse upward. When a dark pulse is applied, the temperature does not rise, and the magnetization direction does not reverse. In this example, the current that moves the domain wall in the magnetic nanowire 2 can be used to obtain an external magnetic field for writing. A downward magnetic field is generated by the current on the left side of the intersection. By arranging the magnetic path, it is possible to create a relationship in which the downward magnetic field passes through a specific location of the magnetic nanowire 2 in a concentrated manner. A downward magnetic field with a strength equal to or greater than the coercive force of the magnetic nanowire at room temperature can be applied to the magnetic nanowire 2, and this can be used as the external magnetic field for initial magnetization. A photosensitive type is used for the magnetic nanowire 2 in this embodiment.

[0074] When irradiating a magnetic nanowire with a pulsed current, there is a concern that continued irradiation may deteriorate the magnetic nanowire 2, no matter how weak the pulsed current is. In Figure 27, the tip of an optical fiber 272 can be displaced in the X and Y directions by an XY actuator 273. By moving it in the X direction, the magnetic nanowire to be used can be selected, and by moving it in the Y direction, the irradiation position can be displaced along the length of the magnetic nanowire. This can extend the life of the storage device. In the case of FIG. 27, a condenser lens 274 is formed on the rear surface of a transparent substrate 271, and the magnetic nanowire 2 and the like are formed on the front surface of the transparent substrate.

[0075] 28 shows the process of forming a condenser lens 274 on the back surface of a transparent substrate 271 and forming magnetic nanowires 2 and the like on the front surface of the transparent substrate 271. The transparent substrate 271 is made of resin and can be molded using a molding die. The condenser lens 274 can be molded by forming a lens surface on the molding die in advance. In this example, a mold is used to create a step in the magnetic nanowire formation region. An RE-TM film is then vapor-deposited in the step formation region. By adjusting the step shape, it is possible to electromagnetically insulate the RE-TM film deposited on the top surface of the step from the RE-TM film deposited on the bottom surface of the step. This allows for mass production of magnetic nanowires. Nanoimprint technology using a mold can improve the mass productivity of memory devices and reduce manufacturing costs. Furthermore, because the RE-TM film deposited on the top surface and the RE-TM film deposited on the bottom surface of the step are separated vertically as shown in Figure 28, there is no need to form gaps between adjacent magnetic nanowires in the horizontal direction. This increases the number of magnetic nanowires that can be formed per unit area.

[0076] Note that an alloy or a multilayer film may be used for the magnetic nanowire 2. When a multilayer film is used, it is sufficient to repeat the deposition process on the stepped portion, and it can be manufactured by nanoimprinting.

[0077] (Other embodiments) As shown in Figure 29, multiple magnetic nanowires A1, A2, A3, and A4 may be arranged along the optical axis of the focused pulsed light for communication 9A. Each magnetic nanowire is thin and transparent, and a phenomenon can be achieved in which all of the magnetic nanowires A1, A2, A3, and A4 arranged along the optical axis are heated to a temperature above their holding temperature by the pulsed light for communication 9A. In this case, the magnetic nanowire to which data is written can be selected by selecting the magnetic nanowire to which a current that moves the domain wall is applied from among the magnetic nanowires A1, A2, A3, and A4. By arranging multiple magnetic nanowires along the optical axis, the storage capacity can be increased by the number of wires.

[0078] When multiple magnetic nanowires A1, A2, A3, and A4 are arranged along the optical axis of the communication pulsed light 9A, it is difficult to detect the magnetization direction using a TEM sensor. In this case, a read light 29 is used to select the magnetic nanowires whose magnetization direction is to be read and energized. A magneto-optical phenomenon then occurs between the energized magnetic nanowire and the read light 29, and by detecting this, the magnetization direction of the energized magnetic nanowire can be detected. To measure the magneto-optical effect, a certain amount of light must be input to the photodetector. Therefore, an optical design that provides a certain level of reflectivity or transmittance for the read light 29 is important. By selecting the dielectric or reflective films to be placed on the light incident side and light transmission side of the magnetic nanowire 2, it is possible to ensure the amount of reflected or transmitted light of the read light 29 input to the photodetector, thereby enabling efficient heating of the magnetic nanowire 2 using the communication pulsed light 9. Both effects can be achieved.

[0079] If an even larger storage capacity is required, the focal depth of the communication pulsed light 9 can be changed in the optical axis direction. Figure 29 shows a case where the focal depth of the communication pulsed light 9 can be adjusted in three stages, as shown by 9A, 9B, and 9C. 9B is not shown, but is at an intermediate depth between 9A and 9C. 29, four magnetic nanowires A1, A2, A3, and A4 are arranged with respect to the focused communication light 9A, four magnetic nanowires B1, B2, B3, and B4 are arranged with respect to the focused communication light 9B, and four magnetic nanowires C1, C2, C3, and C4 are arranged with respect to the focused communication light 9C. When storing data in any one of the magnetic nanowires A, the focal depth is adjusted to the focal depth shown in 9A. When storing data in any one of the magnetic nanowires B, the focal depth is adjusted to the focal depth shown in 9B. When storing data in any one of the magnetic nanowires C, the focal depth is adjusted to the focal depth shown in 9C. For example, when adjusted to 9B (not shown), the focused pulsed light for communication 9B is too deep for the four magnetic nanowires A1, A2, A3, and A4 to be heated to the holding temperature, and the focused pulsed light for communication 9B is too shallow for the four magnetic nanowires C1, C2, C3, and C4 to be heated to the holding temperature. On the other hand, the four magnetic nanowires B1, B2, B3, and B4 are heated to a temperature higher than the holding temperature by the pulsed light for communication 9B. In this case, the focal depth of the reading light 29 can also be displaced in the optical axis direction. When reading data from any one of the magnetic wires A, the focal depth is adjusted to the focal depth shown in 29A, when reading data from any one of the magnetic wires B, the focal depth is adjusted to the focal depth shown in 29B, and when reading data from any one of the magnetic wires C, the focal depth is adjusted to the focal depth shown in 29C.

[0080] As mentioned above, multiple types of pulsed light with different wavelengths and polarization planes may pass through a single optical fiber for communication. In this case, the pulsed light can be separated into each type of pulsed light. The device shown in Figure 29 can be applied to the separated pulsed light. For example, pulsed light with a wavelength of λ1 can be focused as shown in 9A and stored in the magnetic nanowires A1 to A4, pulsed light with a wavelength of λ2 can be focused as shown in 9B and stored in the magnetic nanowires B1 to B4, and pulsed light with a wavelength of λ3 can be focused as shown in 9C and stored in the magnetic nanowires C1 to C4.

[0081] 30 shows an embodiment in which a plasmon antenna is used to narrow the irradiation area of ​​the communication light 9. By using plasmon antennas 30a and 30b, the irradiation area of ​​the communication pulsed light 9 can be concentrated in a narrow range shown in 30c, thereby increasing the temperature rise effect of the magnetic nanowire 2A, shortening the reversed magnetic domain length, and increasing the data storage density. By using plasmon antennas 30d and 30e, the irradiation area of ​​the communication pulsed light 9 can be concentrated in a narrow range shown in 30f, increasing the temperature rise effect of the magnetic nanowire 2B, shortening the reversed magnetic domain length, and increasing the data storage density. As shown in FIG. 31, the irradiated area of ​​the communication pulsed light 9 can be concentrated on a narrow area 31d on the magnetic nanowire 2A and a narrow area 31e on the magnetic nanowire 2B by using plasmon antennas 31a, 31b, and 31c.

[0082] As shown in Figure 32, the magnetic nanowire 2 may be branched into branch lines 2a and 2b. In this case, the arrangement of magnetic domains formed in the magnetic nanowire 2 before branching is transferred to and stored in both the branched magnetic nanowires 2a and 2b, enabling data mirroring. There is no restriction on the number of branch lines, and there may be three or more. There is also no restriction on the number of branch points, and branching may occur at multiple locations.

[0083] The magnetic domain migration speed can be changed depending on the position along the length of the continuous magnetic nanowire. In the case of Figure 32, a current of 2I flows through the magnetic nanowire 2 before branching, and a current of I flows through each of the magnetic nanowires 2a and 2b after branching. As a result, the magnetic domain migration speed is fast in the magnetic nanowire 2 before branching, and slow in the magnetic nanowires 2a and 2b after branching. For example, the magnetic domain migration speed in the magnetic nanowire 2 before branching is 2500 m / sec, and the magnetic domain migration speed in the magnetic nanowires 2a and 2b after branching is 1250 m / sec (the current and the magnetic domain migration side are not necessarily proportional, but they may be). In this case, a relationship can be achieved in which the length of the magnetic domain 32A in the magnetic nanowire 2 before branching is 250 nm, and the lengths of the magnetic domains 32B and 32C in the magnetic nanowires 2a and 2b after branching are 125 nm, thereby increasing the memory density.

[0084] As shown in Fig. 33, data stored in one photosensitive magnetic nanowire 330 can be transferred and stored in a plurality of magnetic nanowires in a dispersed manner. In the case of Fig. 33, data is transferred and stored in 16 magnetic nanowires indicated by 331 to 346 (however, reference numbers 333 to 344 are omitted). A pulsed light is irradiated onto a region 370 of the magnetic nanowire 330, and an arrangement of magnetic domains whose magnetization direction changes in response to the changing pattern of brightness of the pulsed light is stored. Arrow 350 indicates the direction of magnetic domain movement in the magnetic nanowire 330. The arrangement of magnetic domains may also be stored in the magnetic nanowire 330 via a material whose magnetization direction is reversed by a unit bright pulse. The 16 magnetic wires 331-346 cross one magnetic wire 330 at intervals corresponding to the unit magnetic domain length of the magnetic wire 330. Arrows 351 indicate the direction of magnetic domain movement of the magnetic wires 331-346. In this embodiment, multiple transfer magnetic wires 331 to 346 cross a write magnetic wire 330, which changes the magnetization direction of the magnetic domain depending on the data, at intervals corresponding to the unit magnetic domain length of the magnetic wire 330, and are magnetically coupled at the crossing points. According to this embodiment, the first transfer magnetic wire 331 stores 1st, 17th, 33rd, 49th, etc. bits of data, the second transfer magnetic wire 332 stores 2nd, 18th, 34th, 50th, etc. bits of data, the 15th transfer magnetic wire 345 stores 15th, 31st, 47th, 63rd, etc. bits of data, and the 16th transfer magnetic wire 346 stores 16th, 32nd, 48th, 64th, etc. bits of data. In addition, 360 in FIG. 33 indicates an M-RAM, which will be described later.

[0085] 34 shows the process of distributing and storing data of the magnetic nanowire 330 among three magnetic nanowires 331, 332, and 333. For simplicity, a case where unit bright pulses and unit dark pulses are alternately repeated as shown in (a) is described here. (c) to (g) schematically show the magnetic domains in the magnetic nanowire 330 and the transferred magnetic nanowires 331, 332, and 333, where the hatching from left to right indicates the reversed magnetic domains in the magnetic nanowire 330 and the hatching from right to left indicates the reversed magnetic domains in the transferred magnetic nanowires 331, 332, and 333, and the overlapping regions are cross-hatched. Time t4 indicates the end time of the unit dark pulse corresponding to the fourth bit, and the right ends of the magnetic domains in the magnetic nanowire 330 coincide with the right ends of the transferred magnetic nanowires 331, 332, and 333. Time t4a indicates the time when each magnetic domain in the magnetic wire 330 moves to the right from time t4, and the left end of each magnetic domain in the magnetic wire 330 coincides with the left end of the transfer magnetic wires 331, 332, and 333. During the period from time t4 to t4a, the magnetization direction of the region of each transfer magnetic wire 331, 332, and 333 that is magnetically coupled to the magnetic wire 330 does not change. As shown in (b), when a current is applied during the period from time t4 to t4a to move the magnetic domains of the transfer magnetic wires 331, 332, and 333 upward, the magnetic domains having the magnetization direction move upward during the period. A first bit of data is stored in the transfer magnetic wire 331, a second bit of data is stored in the transfer magnetic wire 332, and a third bit of data is stored in the transfer magnetic wire 332.

[0086] Time t7 indicates the end time of the unit bright pulse corresponding to the seventh bit, and the right ends of each magnetic domain in the magnetic wire 330 coincide with the right ends of the transferred magnetic wires 331, 332, and 333. That is, the right end of the magnetic domain corresponding to the fourth bit coincides with the right end of the transferred magnetic wire 331, the right end of the magnetic domain corresponding to the fifth bit coincides with the right end of the transferred magnetic wire 332, and the right end of the magnetic domain corresponding to the sixth bit coincides with the right end of the transferred magnetic wire 333. Time t7a indicates the time when each magnetic domain in the magnetic wire 330 moves right and the left ends of each magnetic domain in the magnetic wire 330 coincide with the left ends of the transferred magnetic wires 331, 332, and 333. That is, the left end of the magnetic domain corresponding to the fourth bit coincides with the left end of the transfer magnetic wire 331, the left end of the magnetic domain corresponding to the fifth bit coincides with the left end of the transfer magnetic wire 332, and the left end of the magnetic domain corresponding to the sixth bit coincides with the left end of the transfer magnetic wire 333. During the period from time t7 to t7a, the magnetization directions of the regions of the transfer magnetic wires 331, 332, and 333 that are magnetically coupled to the magnetic wire 330 do not change. As shown in (b), when a current is applied during the period from time t7 to t7a to move the magnetic domains of the magnetic wires 331, 332, and 333 upward, the magnetic domains having the magnetization directions during this period move upward. The fourth bit of data is newly stored in the transfer magnetic wire 331, the fifth bit of data is newly stored in the transfer magnetic wire 332, and the sixth bit of data is newly stored in the transfer magnetic wire 332.

[0087] As a result of the above, as shown in (g), the 1st, 4th... bits of data are stored in the transfer magnetic nanowire 331, the 2nd, 5th... bits of data are stored in the transfer magnetic nanowire 332, and the 3rd, 6th... bits of data are stored in the transfer magnetic nanowire 333. The data transmission speed in each of the transfer magnetic nanowires 331, 332, and 333 is slowed to one-third of the data transmission speed in the magnetic nanowire 330. As is clear from (a) and (b), the electric field shown in (b) is applied to the transfer magnetic nanowire every several pulses of the communication pulsed light shown in (a). In the case of Figure 34, an electric field is applied to the transfer magnetic nanowire every three pulses of the communication pulsed light. The magnetic domains move intermittently in the transfer magnetic fine wires 331, 332, and 333, and data can be read by utilizing the stop periods. In addition, the period available for data reading can be extended, and the time allocated to data reading processing can be increased.

[0088] A TMR sensor can be used for the sensor 12 shown in FIG. 1. As shown in FIG. 35, the TMR sensor uses a sensor 386 to detect the series resistance of a magnetic domain 380 of a magnetic nanowire, an intermediate layer 382, ​​and a pinned layer 384 whose magnetization direction is pinned downward. If the magnetization directions of the magnetic domain 380 and the pinned layer 384 are aligned, the resistance is low; if they are not aligned, the resistance is high. Therefore, the magnetization direction of the magnetic nanowire 380 can be detected from the output of the sensor 386 that detects the resistance. As shown in FIG. 36, the magnetic nanowire 380 may be attached to an existing TMR sensor in which a free layer 390, an intermediate layer 382, ​​a pinned layer 384, and a sensor 386 are stacked, via an insulating layer 388. The magnetization direction of the magnetic nanowire 380 is transferred to the free layer 390. The resistance value detected by the sensor 386 changes depending on the magnetic field direction of the magnetic domain 380.

[0089] Instead of a structure that detects resistance, a transistor that switches on and off based on that resistance can be used. Figure 37 shows an M-RAM in which the sensor 386 in Figure 35 is replaced with a transistor 392. Figure 38, like Figure 36, shows an existing M-RAM in which a magnetic nanowire 380 is attached to it via an insulating layer 388. The transistor 392 switches on and off depending on the magnetization direction of the magnetic domain 380. For example, if the magnetization direction of the magnetic domain 380 is reversed, the transistor 392 turns off; if the magnetization direction of the magnetic domain 380 is not reversed, the transistor 392 turns on. Conversely, the on / off state of the transistor 392 determines the magnetization direction of the magnetic domain 380, the brightness or darkness of the pulse corresponding to that magnetic domain, and even the 1 or 0 of the data written in the magnetic nanowire. The structures in Figures 37 and 38 are M-RAMs themselves, allowing random access and calculations of data. In other words, calculations using data are possible when transmitted to the HDD 17.

[0090] As shown in Fig. 39, data passing through one communication optical fiber 391 can be distributed and stored in a plurality of light-sensitive magnetic nanowires. Fig. 39 shows an example in which data is distributed and stored in 25 magnetic nanowires 392-1 to 392-25, where 1st, 26th, 51st... bits of data are stored in the first magnetic nanowire 392-1, 2nd, 27th, 52nd... bits of data are stored in the second magnetic nanowire 392-2, and 25th, 50th, 75th... bits of data are stored in the 25th magnetic nanowire 392-25.

[0091] Twenty-five EO modulators EO1 to EO25 are attached to the communication optical fiber 391. Each EO modulator utilizes the phenomenon in which the refractive index of the cladding of the optical fiber 391 changes depending on whether or not a voltage is applied. When no voltage is applied, the refractive index of the cladding is at its normal value, and the communication light travels along the length of the optical fiber while being confined in the core. When a voltage is applied to the EO modulator, the refractive index of the cladding increases, and the communication light leaks out of the optical fiber, passing from the core through the cladding. The leaked communication light is focused by a focusing lens and illuminates the corresponding light-sensitive magnetic nanowire.

[0092] In this example, as shown in Fig. 39(3), the unit bright pulse time T and the unit dark pulse time T are both 40 psec, the communication speed is 25 Gbps, and the refractive index of the core is 1.5.

[0093] (1) in Figure 39 shows the distribution of light and dark in the communication light in the optical fiber 391 at time t1. The communication light speed in the communication optical fiber 391 is determined by the relationship between the speed of light in a vacuum and the refractive index of the core, so the length L of the bright area and the length L of the dark area are 8 mm. The 25 EO modulators EO1 to EO25 are arranged at intervals of 8 mm, which is equal to the length L of the bright area and the length L of the dark area. Note that arrow A indicates the direction of travel of the bright area and the dark area, hatching indicates a bright area, and areas without hatching indicate a dark area. Furthermore, numbers such as 1 and 2 indicate bit numbers.

[0094] Time t1 indicates the time when the tips of the bright and dark regions (hereinafter collectively referred to as pulse regions) in the optical fiber 391 coincide with the right ends of the EO modulators. If the pulse region corresponding to the first EO modulator EO1 at this time is the first bit, then the second bit corresponds to the second EO modulator EO2, and the 25th bit corresponds to the 25th EO modulator EO25. 39(2) indicates the time when the rear end of the pulse region coincides with the left end of each EO modulator. Between times t1 and t1a, the first bit continues to correspond to the first EO modulator EO1, the second bit continues to correspond to the second EO modulator EO2, and the 25th bit continues to correspond to the 25th EO modulator EO25. If voltages are applied to the EO modulators EO1 to EO25 between times t1 and t1a, the first bit of communication light will illuminate the first magnetic nanowire 392-1, the second bit of communication light will illuminate the second magnetic nanowire 392-2, and the 25th bit of communication light will illuminate the 25th magnetic nanowire 392-25. If the communication light illuminating the magnetic nanowire is bright, the magnetic domain in the irradiated area of ​​the magnetic nanowire will be reversed, and if the communication light illuminating the magnetic nanowire is dark, the magnetic domain in the irradiated area of ​​the magnetic nanowire will not be reversed. Hatched magnetic domains indicate reversed magnetic domains, and unhatched magnetic domains indicate non-reversed magnetic domains. Data transmitted by the communication light is written into the light-sensitive magnetic nanowire.

[0095] 39(1) indicates the time when 40 psec×25 pulse time has elapsed since time t1. At time t2, the 26th bit is at a position corresponding to the first EO modulator EO1, the 27th bit is at a position corresponding to the second EO modulator EO2, and the 50th bit is at a position corresponding to the 25th EO modulator EO25. If voltages are applied to the EO modulators EO1 to EO25 at time t2, the 26th bit of data is stored in the first magnetic wire 392-1, the 27th bit of data is stored in the second magnetic wire 392-2, and the 50th bit of data is stored in the second magnetic wire 392-25.

[0096] In each magnetic nanowire, a reversed magnetic domain is formed when the data light is bright, and a non-reversed magnetic domain is formed when the data light is dark. The length of the magnetic domain is approximately 1 μm. A current is passed through each magnetic nanowire, which moves the magnetic domain in the direction of arrow B. In this storage device, one storage process is performed for every 25 bits. The storage process cycle is 1000 psec. A current is passed through each magnetic nanowire, which moves the magnetic domain at a speed of 1 μm / 1000 psec (1000 m / sec).

[0097] Although the dimensional ratio is not accurate in the figure, the spacing L between adjacent EO modulators is 8 mm, while the width W of the magnetic nanowire is approximately 1 μm. Therefore, as shown in Figure 39 (4), it is possible to arrange 4,000 magnetic nanowires within the spacing L between adjacent EO modulators while maintaining a spacing G of 1 μm between adjacent magnetic nanowires. If the magnetic nanowire group can move relative to the EO modulator group in the direction of arrow A, it becomes possible to select a magnetic nanowire to store data from among the 4,000 magnetic nanowires. This can increase the storage capacity by 4,000 times.

[0098] The above is an example, and the present invention is not limited to this. For example, if the communication speed is 100 Gbps and the pulse time is 10 psec, the distance L between adjacent EO modulators can be set to 2 mm, and the speed of movement of the magnetic domains in the magnetic nanowire can be adjusted to 6000 m / sec. Both of these can be adjusted. It is also possible to arrange multiple magnetic nanowires in the distance L between adjacent EO modulators. [Explanation of symbols]

[0099] 1: Storage device 2:Magnetic thin wire 4: Non-magnetic conducting wire 6: External magnetic field generator for initialization 8: External magnetic field generator for writing 9: Optical fiber for communication - pulsed light passing through 10: Irradiation area 12: Magnetization direction detection device (sensor) array 14: Switch 15:DC power supply 16: Control device 17: Hard disk drive 18: Circuit board 19: insulating film 40: Temperature rising region 242:Magnetization direction reversal and propagation material 273: XY actuator

Claims

1. It is equipped with a light-sensitive magnetic nanowire, an electric field application device, and a writing device. the photosensitive magnetic nanowire has a property that when irradiated with a unit bright pulse included in pulsed light for communication, the magnetization direction of the irradiated region changes to the direction of an external magnetic field, and when an electric field is applied, the magnetic domain moves in the length direction; the electric field application device applies the electric field to the photosensitive magnetic nanowire; The writing device changes the magnetization direction of the irradiated region to the direction of the external magnetic field by utilizing the temperature rise caused by irradiation of the bright pulse and the external magnetic field when the pulsed light for communication is a bright pulse, and does not change the magnetization direction when the pulsed light for communication is a dark pulse.

2. The storage device according to claim 1, characterized in that the electric field application device applies an electric field of an intensity that results in a magnetic domain migration speed that satisfies the relationship "magnetic domain migration speed" > "unit reversal magnetic domain length / (unit bright pulse time + unit dark pulse time)," where the duration of a unit bright pulse is defined as a unit bright pulse time, the duration of a unit dark pulse is defined as a unit dark pulse time, and the distance along the length of the photosensitive magnetic nanowire in the region where the magnetization direction changes upon irradiation with a unit bright pulse is defined as a unit reversal magnetic domain length.

3. There are a plurality of the photosensitive magnetic nanowires, 3. The storage device according to claim 1, wherein said electric field application device selects said photosensitive magnetic nanowires to which said electric field is to be applied in a time-division manner.

4. The method further includes a plurality of transfer magnetic fine wires and a transfer electric field application device that applies an electric field to the transfer magnetic fine wire group, the transferred magnetic nanowire group is magnetically coupled to the photosensitive magnetic nanowire at intervals corresponding to a unit magnetic domain length; 3. The storage device according to claim 1, wherein the electric field applying device for transfer applies the electric field to the group of magnetic fine wires for transfer every several pulses of the pulsed light for communication.

5. The optical fiber includes an optical fiber through which the communication pulse light passes, a plurality of the photosensitive magnetic nanowires, and a plurality of EO modulators, the plurality of EO modulators are arranged with respect to the optical fiber at intervals equal to a unit pulse region length within the optical fiber; 3. The storage device according to claim 1, wherein a respective photosensitive magnetic fine wire is disposed for each EO modulator.

6. A storage device according to any one of claims 1 to 5, characterized in that the photosensitive magnetic nanowire is a magnetic nanowire formed from a material in which the magnetization direction of the area irradiated with the unit bright pulse changes in the direction of the external magnetic field.

7. A storage device according to any one of claims 1 to 5, characterized in that the photosensitive magnetic nanowire is formed from a combination of a material in which the magnetization direction of the area irradiated with the unit bright pulse changes in the direction of the external magnetic field, and a magnetic nanowire magnetically coupled to that material.

8. 8. The storage device according to claim 1, wherein the writing device comprises an external magnetic field generating device.

9. 8. The storage device according to claim 1, wherein the writing device utilizes a leakage magnetic field from a non-inverted region as the external magnetic field.

10. A storage medium having a substrate on which a photosensitive magnetic nanowire is formed, which has the property that when irradiated with a unit bright pulse contained in pulsed light for communication, the magnetization direction of the irradiated area changes to the direction of an external magnetic field, and when an electric field is applied, the magnetic domain moves in the longitudinal direction.

11. A condenser lens is formed on one side of the transparent substrate.

11. The storage medium according to claim 10, wherein the photosensitive magnetic nanowire is formed on the opposite surface of the transparent substrate.

12. 12. The storage medium according to claim 11, wherein the transparent substrate is a resin substrate, and the condenser lens is molded on a part of the resin substrate.

13. The storage medium described in claim 11 or 12, characterized in that the transparent substrate is a resin substrate, a step is formed in a portion of the resin substrate, an RE-TM film is formed in that portion, and the RE-TM film is separated into multiple photosensitive magnetic nanowires by the step.

14. A storage medium described in any one of claims 10 to 13, characterized in that the thermal insulation between the photosensitive magnetic nanowire and room temperature is high in the area where the communication pulse light is irradiated onto the photosensitive magnetic nanowire, and is low in the area where the magnetization direction of the photosensitive magnetic nanowire is detected.

15. 14. The storage medium according to claim 10, wherein a heat sink is formed in a part of the region of the photosensitive magnetic nanowire where the pulsed light for communication is irradiated.

16. a detection device for detecting the magnetization direction of the light-sensitive magnetic nanowire; 16. The storage medium according to claim 10, wherein the detection device comprises a transistor that turns on and off depending on the magnetization direction of the photosensitive magnetic nanowire.

17. 17. The storage medium according to claim 10, further comprising a plurality of detectors for detecting the magnetization direction of the photosensitive magnetic nanowire.

18. a step of molding a transparent resin substrate having a condenser lens formed thereon using a molding die; a step of manufacturing a photosensitive magnetic nanowire on the transparent resin substrate, A storage medium manufacturing method characterized in that the photosensitive magnetic nanowire has the property that when irradiated with a unit bright pulse contained in pulsed light for communication, the magnetization direction of the irradiated area changes to the direction of an external magnetic field, and when an electric field is applied, the magnetic domain moves in the longitudinal direction.

19. A step of molding a resin substrate having a step formed in a partial area using a molding die; a step of forming a film on the step-forming region of the resin substrate to manufacture a plurality of photosensitive magnetic nanowires; A storage medium manufacturing method characterized in that the photosensitive magnetic nanowire has the property that when irradiated with a unit bright pulse contained in pulsed light for communication, the magnetization direction of the irradiated area changes to the direction of an external magnetic field, and when an electric field is applied, the magnetic domain moves in the longitudinal direction.

Images