Write-once magnetic nanowire memory

Abstract

To provide a storage device capable of stably holding recorded information after finalizing.SOLUTION: A write-once type magnetic nanowire memory 1 includes: a plurality of magnetic nanowires 10; one or two recording elements 20 that are arranged perpendicular to the plurality of magnetic nanowires 10 and write data to the magnetic nanowire 10 by a current magnetic field generated by supplying and generating current for writing at normal recording; a plurality of detection elements 50 that are provided for each magnetic nanowire 10 and detect data written to the magnetic nanowire 10; and a fuse 31 as a means for eliminating the recording function of the recording element 20 during finalizing.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a write-once type magnetic fine wire memory that records information in binary in correspondence with the magnetization direction of magnetic domains with respect to a magnetic recording medium composed of a fine wire-shaped magnetic material, and particularly to a write-once type magnetic fine wire memory that does not permit any data modification or additional writing after finalization.

Background Art

[0002] For example, broadcasting stations are hoping for the emergence of a storage medium (a write-once memory for archive video recording) that can stably hold the photographed or broadcast video for a long period (almost permanently). Currently, optical disks, magnetic tapes, and magnetic disks are used as storage media for archive video recording. However, optical disks have a problem of being unreadable due to corrosion of the reflective layer. Magnetic tapes also have a problem of being unreadable due to deterioration of the binding material of the magnetic material. Magnetic disks also have a problem of being unreadable due to mechanical malfunction such as the drop of the magnetic head or the failure of the disk rotation motor. Therefore, it is essential for a storage medium for archive video recording to have a solid memory configuration having various performances such as large capacity, high-speed reproduction, write-once performance, and the performance of holding information permanently.

[0003] On the other hand, the present applicant is promoting research on magnetic fine wire memories in order to realize the ultra-high speed and large capacity storage required for future so-called 3D TVs such as space image reproduction type TVs. A magnetic fine wire memory uses a magnetic fine wire as a recording medium. Video information is generally sequential data, and a magnetic fine wire memory has a sequential access solid memory configuration (race track memory) suitable for storing data sequentially (continuously) in the length direction of the magnetic fine wire (see Patent Documents 1 to 3).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] The invention described in Patent Document 1 allows for modification and addition of stored data, making it unsuitable as a storage medium for archival video recording where stable video storage for a long period (almost permanently) is desired.

[0006] Furthermore, the magnetic nanowire memory disclosed in Patent Documents 2 and 3 allows for modification or addition of data stored in the magnetic nanowire medium by applying a recording current to the recording element later, even when accumulating and storing data for a long period of time, and thus there was room for improvement.

[0007] This invention has been made in view of the above-mentioned problems, and aims to provide a write-once type magnetic nanowire memory that can stably retain recorded information after finalization. [Means for solving the problem]

[0008] To solve the aforementioned problems, the write-once magnetic nanowire memory according to the present invention comprises a plurality of magnetic nanowires, one or two recording elements arranged orthogonally to the plurality of magnetic nanowires and writing data to the magnetic nanowires by a current magnetic field generated when a writing current is supplied during normal recording, a plurality of detection elements provided for each magnetic nanowire for detecting the data written to the magnetic nanowire, and means for erasing the recording function of the recording elements when finalized.

[0009] Furthermore, the write-once magnetic nanowire memory according to the present invention comprises a plurality of magnetic nanowires, one or two recording elements arranged orthogonally to the plurality of magnetic nanowires and writing data to the magnetic nanowires by a current magnetic field generated when a writing current is supplied during normal recording, a plurality of detection elements provided for each magnetic nanowire to detect data written to the magnetic nanowire, an integrated control unit having a circuit that oversees the entire data recording and playback processing, a pulse current source that supplies pulse current to the magnetic nanowires, a recording system control unit having a circuit that controls the recording current flowing through the recording elements, a playback system control unit having a circuit that controls the playback of data detected by the detection elements, and means for erasing the recording function of the recording elements when finalized. [Effects of the Invention]

[0010] The present invention provides the following excellent effects. According to the write-once magnetic nanowire memory of the present invention, it is possible to prohibit any data modification or addition after finalization. According to the write-once magnetic nanowire memory of the present invention, it is possible to stably retain the recorded information after finalization. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic diagram showing the configuration of a write-once type magnetic nanowire memory according to the first embodiment of the present invention. [Figure 2] Figure 1 shows a waveform diagram illustrating an example of the recording current in a write-once magnetic nanowire memory. [Figure 3] This is a schematic diagram showing the configuration of a write-once type magnetic nanowire memory according to a second embodiment of the present invention. [Figure 4] This is a schematic diagram showing the configuration of a write-once type magnetic nanowire memory according to a third embodiment of the present invention. [Figure 5] This is a schematic diagram showing the configuration of a write-once type magnetic nanowire memory according to the fourth embodiment of the present invention. [Figure 6]It is a schematic diagram showing the configuration of a write-once type magnetic fine wire memory according to the fifth embodiment of the present invention. [Figure 7] It is a schematic diagram showing the configuration of a write-once type magnetic fine wire memory according to the sixth embodiment of the present invention. [Figure 8] It is a schematic diagram showing the configuration of a write-once type magnetic fine wire memory according to the seventh embodiment of the present invention. [Figure 9] It is a schematic diagram showing the procedure for rewriting the reproduced data by the write-once type magnetic fine wire memory of FIG. 8. [Figure 10] It is a schematic diagram showing the configuration of a write-once type magnetic fine wire memory according to the eighth embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0015] The plurality of magnetic fine wires 10 each function as a recording medium (magnetic fine wire medium) and are arranged in parallel in a plane on a substrate not shown. The substrate is a base for constituting the write-once type magnetic fine wire memory 1 and is a substrate in a broad sense for forming the recording element 20 and the magnetic fine wires 10, and a known substrate material can be applied.

[0016] The plane in which the plurality of magnetic fine wires 10 are arranged in parallel is hereinafter referred to as the magnetic fine wire medium region 2. In FIG. 1, the write-once type magnetic fine wire memory 1 includes four magnetic fine wires 10 in the magnetic fine wire medium region 2, but the number of magnetic fine wires 10 is not particularly limited. Magnetic domains D with a recording bit length are formed on the magnetic fine wires 10 by the recording element 20. In FIG. 1, the information "1" recorded on the magnetic fine wire 10 is shown as a downward magnetic domain, and the information "0" is shown as an upward magnetic domain.

[0017] The magnetic fine wires 10 can be made of a known magnetic material. Specifically, transition metals such as Fe, Co, Ni, Gd, Tb, and noble metals such as Pd, Pt are repeatedly laminated, such as Co / Pt multilayer films and Tb / Co multilayer films, alloys of rare earth metals and transition metals such as Tb-Fe-Co, Gd-Fe (RE-TM alloys), L , ,

[0018] ,

[0017] , , 10 , Examples include FePt, FePd, etc. as L-based regular alloys.

[0018] To drive the magnetic domain walls formed on the magnetic nanowire 10, conductor wiring 15 is connected to both ends of the magnetic nanowire 10, and a DC pulse current is supplied from the pulse current source 120 via the conductor wiring 15. The region enclosed between a pair of nearest magnetic domain walls is called a magnetic domain, and driving (moving) the magnetic domain walls with current is also called driving the magnetic domain. Furthermore, the direction in which the magnetic domains formed on the magnetic nanowire 10 are driven is assumed to be unidirectional, from the recording element 20 to the detection element 50.

[0019] The recording element 20 is provided for recording information on the magnetic nanowire 10 and is a component equivalent to the recording head in a magnetic disk, for example. The recording element 20 is a conductor perpendicular to the magnetic nanowire 10 and generates a magnetic field when an electric current is supplied to it. The recording element 20 is made of a thin metal film and consists of a common electrode metal material such as metals or alloys thereof, such as Cu, Al, Au, Ag, Ta, Cr, etc. Among such metal materials, Au is particularly preferred because it has high conductivity and is chemically stable.

[0020] An interlayer insulating layer (not shown) is formed between the recording element 20 and the magnetic nanowire 10. For example, an oxide film such as SiO2 or Al2O3, or a known inorganic insulating material such as Si3N4 or MgF2 can be applied to the interlayer insulating layer. Alternatively, a laminated film of oxide films or inorganic insulating materials may be used. In Figure 1, the recording element 20 is positioned below (on the substrate side of) the magnetic nanowire 10, but the recording element 20 may also be positioned above the magnetic nanowire 10.

[0021] The method by which the recording element 20 records magnetic domains on the magnetic nanowire 10 involves supplying a recording current to the recording element 20 from an externally provided pulsed current source (hereinafter referred to as the recording power supply) to supply the recording current. The current flowing through the recording element 20 generates a magnetic field, and this current-magnetic field locally reverses the magnetization of the magnetic nanowire 10. This locally reversed magnetization region is recorded as a magnetic domain.

[0022] The detection element 50 detects magnetic domains (information) recorded in the magnetic nanowire 10. The detection element 50 is a magnetic head for playback, which detects the direction of leakage flux generated from the magnetic domain directly below it and outputs a signal corresponding to the direction of magnetization to the playback system control unit 140.

[0023] The main control unit 110 is the primary control unit that controls all operations of the write-once magnetic nanowire memory 1. Like a normal magnetic nanowire memory, the write-once magnetic nanowire memory 1 performs recording (writing information), playback (reading information), and driving (bit shifting of magnetic domains). In other words, the main control unit 110 controls the operation of the recording system control unit 130, the playback system control unit 140, and the pulse power supply, as well as the input / output control necessary for memory operation. For example, the main control unit 110 controls the timing of supplying pulse current from the pulse current source 120 to each magnetic nanowire 10. For example, the main control unit 110 can receive commands from the input unit 150, such as commands to start recording or commands to finalize.

[0024] The pulse current source 120 supplies a DC pulse current to each magnetic nanowire 10 in order to bit-shift the magnetic domains (information) formed on the magnetic nanowires 10. Bit shifting means that the magnetic domains formed on the magnetic nanowires 10 are shifted approximately by the length of the recording bit in the longitudinal direction of the magnetic nanowire 10 by one pulse of the pulse current.

[0025] The recording control unit 130 divides the input information signal and supplies current to the recording element 20 in order to record the divided unit information on each magnetic nanowire 10. The recording control unit 130 may also be equipped with a recording power supply. The playback control unit 140 synthesizes the information signals obtained from each detection element 50 to reconstruct the signal. The reconstructed signal (video signal, audio signal) is output from the output unit 160. The input unit 150 consists of input devices such as button switches, touch panels, remote controls, mice, and keyboards connected to the write-once magnetic nanowire memory 1, which allow the operator to input commands. The output unit 160 is an output device such as a liquid crystal display or speaker connected to the write-once magnetic nanowire memory 1, which can present video and audio signals to the user.

[0026] The fuse 31 is connected to the recording element 20 and, when blown, renders the data storage state of the magnetic nanowire 10 unrewritable. The fuse 31 does not blow under the magnitude of the recording current that flows through the recording element 20 during normal recording. The insertion point of the fuse 31 is not particularly limited as long as it is somewhere along the connection from the recording system control unit 130 to the recording element 20. The fuse 31 is connected in series with the recording element 20. The fuse 31 is made of a metallic material that has a higher resistance value than the conductive material used in the recording element 20. If the material used in the recording element 20 is, for example, Cu, Al, or Au, the fuse 31 is made of tungsten, nichrome wire, or a material commonly used in fuses.

[0027] Figure 2 is a waveform diagram showing an example of the recording current of the write-once magnetic nanowire memory shown in Figure 1. In the recording current pulse shown in Figure 2, the current value In is the current value that flows through the recording element 20 under normal circumstances, and represents the absolute value of the current value that can generate a magnetic field to reverse the magnetization of the magnetic nanowire 10, which is necessary for recording magnetic domains. Here, the current value required to form a downward magnetic domain is set to +In, and the current value required to form an upward magnetic domain is set to -In. For example, the recording current that flows between time T1 and time T2 forms information "1" (downward magnetic domain), and the recording current that flows between time T3 and time T4 forms information "0" (upward magnetic domain). On the other hand, the current value If is the current value that flows through the recording element 20 when the fuse blows, and represents the absolute value of the current value required to blow the fuse 31. The current value If is greater than the current value In. The current value If is set to a magnitude that will reliably blow the fuse 31. On the other hand, if the current value If is excessive, the recording element 20 may overheat and degrade the nearby magnetic nanowires 10, so it is preferable to set it to an appropriate value. The recording power supply is configured to switch between supplying two stages of current: a writing current supplied to the recording element 20 during normal recording and a melting current supplied to the recording element 20 during finalization. According to the write-once magnetic nanowire memory 1, during long-term storage, the recording element 20 can be permanently rendered inoperable (finalized) by passing an excessive current (current value If) through the fuse 31 to cause it to melt, thereby constructing a desired write-once storage device.

[0028] (Second Embodiment) Next, a write-once type magnetic nanowire memory 1B according to the second embodiment will be described with reference to Figure 3. Components identical to those in the write-once type magnetic nanowire memory 1 shown in Figure 1 are denoted by the same reference numerals and their descriptions are omitted.

[0029] The write-once magnetic nanowire memory 1B has a structure in which a portion of the conductor constituting the recording element 20B is narrowed, instead of connecting a fuse to the recording element 20B. In other words, in the write-once magnetic nanowire memory 1B, the means of deactivating the recording function of the recording element 20B is the narrowed portion 32, which is a narrowed portion of the conductor constituting the recording element 20B. The narrowed portion 32 does not melt with the magnitude of the recording current that flows through the recording element 20B during normal recording, and when it melts, the electrical connection between the recording element 20B and the recording power supply becomes impossible, making the data storage state of the magnetic nanowire 10 unrewritable. In this embodiment as well, the recording power supply is configured to switch between supplying two stages of current: a writing current supplied to the recording element 20B during normal recording and a melting current supplied to the recording element 20B during finalization.

[0030] The constricted portion 32 of the recording element 20B may be located within the magnetic nanowire medium region 2 in which many magnetic nanowires 10 are arranged in parallel, or it may be located outside the magnetic nanowire medium region 2. However, when the constricted portion 32 of the recording element 20B is cut, the metal material of the recording element 20B melts, and the molten metal scatters as fine particles (spatter) and reattaches as metal particles. Since this spatter may cause a short circuit between the magnetic nanowire media, it is more preferable to provide the constricted portion 32 of the recording element 20B outside the magnetic nanowire medium region 2.

[0031] According to the write-once type magnetic nanowire memory 1B, during long-term storage, an excessive current such as the current value If shown in Figure 2 can melt the constricted portion 32 of the recording element 20B itself, thereby permanently rendering the recording element 20B inoperable.

[0032] (Third embodiment) Next, a write-once type magnetic nanowire memory 1C according to the third embodiment will be described with reference to Figure 4. Components identical to those in the write-once type magnetic nanowire memory 1 shown in Figure 1 are denoted by the same reference numerals and their descriptions are omitted.

[0033] The write-once magnetic nanowire memory 1C has a structure in which two parallel recording elements 21 and 22 are arranged orthogonally to a large number of parallel-arranged magnetic nanowires 10. In this write-once magnetic nanowire memory 1C, when writing information to the magnetic nanowire 10, pulse currents (current A and current B) are passed through the two recording elements 21 and 22 in opposite directions, and the resulting magnetic fields are combined in the gap between the two recording elements 21 and 22. This write-once magnetic nanowire memory 1C uses this combined magnetic field to record magnetic domains of any magnetization direction on the magnetic nanowire 10. At this time, in the gap between the two recording elements 21 and 22, the direction of the magnetic field generated by the recording current (current A) flowing through recording element 21 and the direction of the magnetic field generated by the recording current (current B) flowing through recording element 22 are the same, so they reinforce each other, resulting in a combined magnetic field, which allows for efficient writing with a small recording current.

[0034] The write-once magnetic nanowire memory 1C has a configuration in which a fuse 31 is connected in series with the recording element 22. Therefore, during long-term storage, an excessive current is passed through the fuse 31 to melt it, permanently rendering the recording element 22 inoperable (finalizing it), thereby creating the desired write-once memory device. Alternatively, the fuse 31 may be connected in series with the recording element 21, or with two recording elements 21 and 22, each having a fuse 31 connected in series.

[0035] (Modified version of the third embodiment) Instead of connecting a fuse, a narrowed section 32 (see Figure 3) may be created by narrowing a portion of the conductor constituting at least one of the two recording elements 21, 22. In this way, it is also possible to melt the recording element itself with excessive current, permanently rendering the recording element inoperable.

[0036] (Fourth Embodiment) Next, a write-once magnetic nanowire memory 1D according to the fourth embodiment will be described with reference to Figure 5. Note that components identical to those in the write-once magnetic nanowire memory 1C shown in Figure 4 are denoted by the same reference numerals and their descriptions are omitted.

[0037] The write-once magnetic nanowire memory 1D differs from the write-once magnetic nanowire memory 1C shown in Figure 4 in that it uses a U-shaped recording element 20D instead of two parallel recording elements. The U-shaped recording element 20D has a structure in which the two recording elements 21 and 22 shown in Figure 4 are electrically connected at one end of each. The write-once magnetic nanowire memory 1D records magnetic domains in any magnetization direction on the magnetic nanowire 10 using a combined current magnetic field generated in the U-shaped gap.

[0038] The write-once magnetic nanowire memory 1D has a configuration in which a fuse 31 is connected in series with the recording element 20D. Therefore, during long-term storage, an excessive current is passed through this fuse 31 to melt it, permanently rendering the recording element 20D inoperable (finalizing) it, thereby creating the desired write-once memory device.

[0039] (Modified version of the fourth embodiment) Instead of connecting a fuse, a narrowed section 32 (see Figure 3) may be created by narrowing a portion of the conductor constituting the recording element 20D. In this way, it is also possible to melt the recording element itself with excessive current, permanently rendering the recording element inoperable.

[0040] In the first to fourth embodiments described above, the means for deactivating the recording function of the recording element is a fuse 31 made of a material with higher resistance than the conductor material of the wire constituting the recording element 20, or a constricted section 32 in the wire constituting the recording element 20B where a portion of the wire is narrowed, and it is designed to melt when a predetermined current larger than the writing current is supplied during finalization. In other words, in the first to fourth embodiments described above, the means for deactivating the recording function of the recording element during finalization is either located in the immediate vicinity of the recording element or is the recording element itself, but it is not limited to these. The means of disabling the recording function of a recording element may be to prevent the generation of an electric field around the recording element, that is, to disable the recording element's electric field generation function. Below, as typical examples of means of disabling the recording element's electric field generation function, embodiments (5th and 6th embodiments) will be described in which the circuit that controls the flow of recording current to the recording element is made electrically inaccessible, or the circuit that controls the flow of recording current is physically destroyed.

[0041] (Fifth embodiment) A write-once magnetic nanowire memory 1E according to the fifth embodiment will be described with reference to Figure 6. Components identical to those in the write-once magnetic nanowire memory 1 shown in Figure 1 are denoted by the same reference numerals and their descriptions are omitted. The write-once magnetic nanowire memory 1E does not have a fuse, and the functions of the control unit 110E differ from those of the write-once magnetic nanowire memory 1.

[0042] In the write-once magnetic nanowire memory 1E, the means for erasing the recording function of the recording element 20 is a function of the control unit 110E. When the integrated control unit 110E receives a command (function stop command) to stop the function of the recording system control unit 130 from an external source via the input unit 150, it sends this function stop command to the recording system control unit 130. In other words, the integrated control unit 110E functions as a means to automatically stop the function of the recording system control unit 130 itself when a function stop command is input to the recording system control unit 130 from an external source. As a result, when a function stop command is input to the recording system control unit 130, the data storage state of the magnetic nanowire 10 can be made unrewritable.

[0043] After finalization is performed, that is, after the recording control unit 130 itself has been shut down in response to a command, the recording control unit 130 may be configured not to accept any commands, or the overall control unit 110E may be configured not to accept commands that would restart the recording control unit 130. This ensures that the data stored in the magnetic nanowire 10 is not altered or added to.

[0044] (Modified version of the fifth embodiment) The write-once magnetic nanowire memory 1E may, in response to an external command, disable the function of the wiring path that sends control signals from the main control unit 110E to the recording control unit 130, rather than disabling the function of the recording control unit 130 itself. In this case, when the control unit 110E receives a command (function stop command) via the input unit 150 from an external source to break the path from the control unit 110E to the recording system control unit 130, it disables this path. To disable the path, a switch that switches and cuts the wiring can be installed in the middle of the path, and when the control unit 110E receives a command, it can activate the switch to switch and cut the wiring. In this way, the control unit 110E functions as a means to break the path from the control unit 110E to the recording system control unit 130 when a function stop command is input to the control unit 110E from an external source. In this modified example as well, when a function stop command is input to the control unit 110E, the data storage state of the magnetic nanowire 10 can be made unrewritable.

[0045] (Sixth Embodiment) A write-once magnetic nanowire memory 1F according to the sixth embodiment will be described with reference to Figure 7. Components identical to those in the write-once magnetic nanowire memory 1 shown in Figure 1 are denoted by the same reference numerals and their descriptions are omitted. The write-once magnetic nanowire memory 1F differs from the write-once magnetic nanowire memory 1 in that it does not have a fuse and includes a package 200 configured to physically destroy the circuit that controls the flow of the recording current after finalization.

[0046] The write-once magnetic nanowire memory 1F is packaged with multiple magnetic nanowires 10, recording elements 20, multiple detection elements 50, a pulse current source 120, a recording system control unit 130, a playback system control unit 140, and an overall control unit 110. In the write-once magnetic nanowire memory 1F, the means for erasing the recording function of the recording element 20 is a partial break-off portion 201 on the outer periphery of the package that corresponds to a point where the path from the overall control unit 110 to the recording system control unit 130 can be broken. By breaking off the partial break-off portion 201 on the outer periphery of the package, the data storage state of the magnetic nanowire 10 is made unrewritable.

[0047] In the example shown in Figure 7, the partial folding section 201 is located above the folding line 202 of the rectangular package 200 in Figure 7, in the outer peripheral region of the package including the top edge. The recording system control unit 130 is located inside the package 200 at the location corresponding to the partial folding section 201. Furthermore, the wiring route from the main control unit 110 to the recording system control unit 130 crosses the folding line 202.

[0048] It is preferable that the material and thickness of at least the partially foldable portion 201 of the package 200 be determined so that it can be easily folded by hand. Furthermore, the folding position may be indicated by a dashed line or similar marking so that it is easily visible to a person. This prevents damage to circuits and other components necessary for retrieving stored information after the partial folding section 201 has been folded. Furthermore, the shape of the area to be folded may be, for example, a groove, a dotted line, or a crease. This makes it possible for a person to easily fold it by hand without using a jig.

[0049] (Modified version of the fifth embodiment) The write-once magnetic nanowire memory 1F may be provided with a partial break-off section 201 corresponding to a location where the circuit of the recording system control unit 130 itself can be broken, instead of a location where the path from the overall control unit 110 to the recording system control unit 130 can be broken. In this case, the means for erasing the recording function of the recording element 20 in the write-once magnetic nanowire memory 1F is the partial break-off section 201 on the outer periphery of the package, which corresponds to a location where the circuit of the recording system control unit 130 itself can be broken inside the package 200, and by breaking off the partial break-off section 201 on the outer periphery of the package, the data storage state of the magnetic nanowire 10 is made unrewritable. In this modified example, the fold line 202 of the package 200 can be set closer to the top edge in Figure 7, or limited to the location where the circuit of the recording control unit 130 is located, thereby minimizing the package area that becomes unnecessary after finalization.

[0050] (Modified versions of the 5th and 6th embodiments) In the write-once type magnetic nanowire memory 1E,1F, when an external command (function stop command) is input or the circuit is physically destroyed by breaking off the partial break-off portion 201 on the outer circumference of the package in order to disable the current magnetic field generation function of the recording element, the power supply may be cut off instead of destroying the recording system control unit 130 itself or severing the path from the main control unit 110 to the recording system control unit 130. In this case, the means for disabling the recording function of the recording element 20 is to mechanically or electrically disconnect the power supplied to the recording system control unit 130. By disconnecting the power supplied to the recording system control unit 130, the data storage state of the magnetic nanowire 10 is made unrewritable.

[0051] The method for disconnecting the power supplied to the recording control unit 130 can be the same as described in the fifth and sixth embodiments, such as inputting a command to disconnect the power from an external source, or physically destroying the power supply line by breaking off the partial break-off portion 201 on the outer circumference of the package. Alternatively, a fuse may be pre-connected to the power supply line supplied to the recording control unit 130, and the fuse on the power supply line may be blown out after finalization. Note that the write-once magnetic nanowire memories 1E and 1F may be equipped with recording elements 21 and 22 (see Figure 4) or recording element 20D (see Figure 5) instead of recording element 20.

[0052] (Seventh Embodiment) A write-once magnetic nanowire memory 1G according to the seventh embodiment will be described with reference to Figure 8. Components identical to those in the write-once magnetic nanowire memory 1 shown in Figure 1 are denoted by the same reference numerals and their descriptions are omitted. In addition to recording (writing information), playback (reading information), and driving (bit shifting of magnetic domains), the write-once magnetic nanowire memory 1G also performs the operation of writing the played-back data back to the magnetic nanowire 10. Therefore, the write-once magnetic nanowire memory 1G differs from the write-once magnetic nanowire memory 1 in that it includes a second recording element 60 and a write-back control unit 170.

[0053] The second recording element 60 is arranged orthogonally to a plurality of magnetic nanowires 10 and writes data detected by the detection element 50 to the magnetic nanowires 10 using an electric magnetic field. The write-back control unit 170 has a circuit that controls the recording current flowing to the second recording element 60. In the write-once magnetic nanowire memory 1G, after the fuse 31 is blown and the recording function of the recording element 20 is lost (after finalization), the second recording element 60 has a recording function. However, the control circuit of the write-back control unit 170 is an independent circuit from the control circuit of the recording element 20, and cannot be modified or appended to from the outside.

[0054] In the write-once magnetic nanowire memory 1G, when data is retrieved, a pulsed current is supplied in the longitudinal direction of the magnetic nanowire 10 to drive the magnetic domains (binary information) recorded on the magnetic nanowire 10. At this time, in Figure 8, the magnetic domains recorded near the recording element 20 (for example, magnetic domain D) are driven to directly below the detection element 50. Each detection element 50 detects the magnetization direction of the magnetic domain that has moved directly below it. Subsequently, the magnetic domain whose magnetization direction has been detected is repeatedly subjected to subsequent bit shifts and disappears from the end of the magnetic nanowire 10 (right end in Figure 8). However, with the second recording element 60 and the write-back control unit 170, after data is retrieved, the same data can be written back to the starting end side of the magnetic nanowire 10 (left side in Figure 8).

[0055] The control of writing back the playback data can be achieved by performing the following two steps in succession. In this case, the control unit 110 of the write-once magnetic nanowire memory 1G writes one of the two values ​​of information to all magnetic nanowires 10 in the first step, and then bit-shifts the magnetic domains only for the magnetic nanowires 10 for which it is necessary to write back and restore the written information (magnetic domain). In the second step, the same process is performed for the other of the two values ​​of information.

[0056] A specific example of controlling the write-back of playback data will be explained with reference to Figure 9. Here, in order to distinguish the four magnetic nanowires 10, they will be referred to as the first magnetic nanowire, the second magnetic nanowire, the third magnetic nanowire, and the fourth magnetic nanowire from top to bottom in Figure 9(a). As shown in Figure 9(a), it is assumed that the information "1" is detected from the first magnetic nanowire, the information "0" is detected from the second magnetic nanowire, the information "0" is detected from the third magnetic nanowire, and the information "1" is detected from the fourth magnetic nanowire. In this case, the procedure for writing back the information "1", "0", "0", and "1" to each of the four magnetic nanowires 10 is as follows.

[0057] (Step S1) As shown in Figure 9(b), by passing a recording current (current A) through the second recording element 60, the same magnetic domain of information "1" is formed in all magnetic nanowires 10. In this example, it is only necessary to actually write back "1" to the first and fourth magnetic nanowires. Therefore, as shown in Figure 9(c), a DC pulse current for current driving is supplied from the pulse current source 120 (see Figure 8) only to the first and fourth magnetic nanowires, and the magnetic domain of the recorded information "1" is shifted to the right by one bit.

[0058] (Step S2) Following step S1, as shown in Figure 9(d), a recording current (current B) in the opposite direction to that in step S1 is passed through the second recording element 60 to form magnetic domains of the same information "0" in all magnetic nanowires 10. In this example, it is only the second and third magnetic nanowires that actually need to have "0" written back. Therefore, as shown in Figure 9(e), a DC pulse current is supplied from the pulse current source 120 (see Figure 8) to the second and third magnetic nanowires only to shift the magnetic domains of the recorded information "0" one bit to the right. These two steps complete the process of writing the information “1”, “0”, “0”, and “1” back to each of the four magnetic nanowires 10, from top to bottom as shown in Figure 9(e).

[0059] Alternatively, step S2 may be performed before step S1, and the same effect can be achieved with these two steps. Furthermore, if information is continuously recorded on the four magnetic nanowires 10 and this information is to be detected continuously, the continuous information can be written back by repeating a two-step operation each time one bit of information is detected.

[0060] Figure 8 shows a configuration in which the second recording element 60 is positioned above the magnetic nanowire 10, but it may also be positioned below the magnetic nanowire 10, similar to the recording element 20. Also, Figure 8 shows a configuration in which the second recording element 60 is positioned to the left of the recording element 20, but the second recording element 60 may also be positioned to the right of the recording element 20.

[0061] This seventh embodiment may be implemented in combination with other compatible embodiments (the second to sixth embodiments). Furthermore, in the write-once magnetic nanowire memory 1G, if the two recording elements 21 and 22 (see Figure 4) are arranged orthogonally to demarcate a predetermined length region of each of the multiple magnetic nanowires 10, and when the fifth or sixth embodiment is combined, the second recording element 60 can be omitted, and the memory may be configured in this manner. However, in that case, the write-back control unit 170 shall have a circuit that controls the recording current flowing through the two recording elements 21 and 22 when writing the data detected by the detection element 50 to the magnetic nanowire 10.

[0062] (Eighth embodiment) The write-once magnetic nanowire memory 1H according to the eighth embodiment will be described with reference to Figures 10(a) and 10(b) (and Figure 1 as appropriate). Components identical to those in the write-once magnetic nanowire memory 1 shown in Figure 1 are denoted by the same reference numerals and their descriptions are omitted. The write-once magnetic nanowire memory 1H comprises a package 210 formed by stacking multiple write-once magnetic nanowire memories 1, and a magnetic shield 3.

[0063] In other words, the write-once magnetic nanowire memory 1H is packaged with multiple stacked surfaces of multiple magnetic nanowires 10 arranged in a planar manner, along with a recording element 20 and multiple detection elements 50. The package 210 may include a pulse current source 120, a recording system control unit 130, a playback system control unit 140, and an overall control unit 110.

[0064] The magnetic shield 3 covers at least a portion of the package 210. It is preferable that the write-once magnetic nanowire memory 1H is equipped with the magnetic shield 3 before the recording function of the recording element 20 necessary for writing information is lost. As the magnetic shield material, high-permeability soft magnetic materials commonly used for magnetic shielding purposes, such as permalloy, can be directly applied. Because the write-once magnetic nanowire memory 1H is equipped with the magnetic shield 3, it is possible to prevent the loss of stored data due to magnetic fields from the surrounding environment, such as disturbances that occur unintentionally during long-term storage.

[0065] Figures 10(a) and 10(b) show a write-once magnetic nanowire memory 1H with a magnetic shield 3 mounted so as to cover the top and bottom surfaces of the package 210 as an example, but the arrangement of the magnetic shield 3 is not limited to this. For example, the magnetic shield 3 may be mounted so as to cover a part of the package 210 that surrounds the magnetic nanowire medium area 2, or the magnetic shield 3 may be mounted so as to cover the entire surface (e.g., 6 surfaces) of the package 210. Alternatively, a magnetic shield package made of magnetic shield material may be prepared, and the write-once magnetic nanowire memory may be stored inside the magnetic shield package.

[0066] Although the write-once type magnetic nanowire memory according to each embodiment of the present invention has been described above, the spirit of the present invention is not limited to these descriptions and should be interpreted broadly based on the claims. Furthermore, it goes without saying that various modifications and alterations based on these descriptions are also included in the spirit of the present invention. For example, the eighth embodiment may be implemented in combination with other combineable embodiments (the second to seventh embodiments).

[0067] Furthermore, the write-once magnetic nanowire memory 1G can also be configured to prevent data loss due to data playback instead of write-back operation. In this case, the magnetic nanowire 10, which in Figure 8 had a data storage area to the left of the read area directly below the detection element 50, will also have a buffer (register) area to the right of the read area in Figure 8, having a length similar to that of the data storage area. In addition, the pulse current source 120 connected to the magnetic nanowire 10 will be configured to supply current in the reverse direction. Even with this configuration, data playback can be repeatedly performed after finalization. [Explanation of symbols]

[0068] 1,1B,1C,1D,1E,1F,1G,1H Write-once magnetic nanowire memory 2 Magnetic thin wire media area 3. Magnetic shielding 10 Magnetic thin wire 15 Conductor Wiring 20, 20B, 20D recording elements 21,22 recording elements 31 fuses 32 Stenosis 50 detection elements 60 Second recording element 110, 110E Control Unit 120 pulse current source 130 Recording System Control Unit 140 Regeneration System Control Unit 150 Input section 160 Output section 170 Writeback control unit 200,210 packages 201 Partial break-off section 202 Folding line

Claims

1. Multiple magnetic nanowires, One or two recording elements are arranged orthogonally to a plurality of magnetic nanowires and write data to the magnetic nanowires by a current magnetic field generated when a writing current is supplied during normal recording. A plurality of detection elements provided for each of the magnetic nanowires for detecting data written on the magnetic nanowire, A write-once magnetic nanowire memory characterized by comprising means for erasing the recording function of the recording element when it is finalized.

2. The means for disabling the recording function of the recording element is a fuse connected to the recording element, which, when melted, renders the data storage state of the magnetic nanowire unrewritable. The write-once type magnetic nanowire memory according to claim 1, characterized in that the fuse does not melt at the magnitude of the recording current that flows through the recording element during normal recording.

3. The means for disabling the recording function of the recording element is a constricted section in which a portion of the conductor constituting the recording element is narrowed. The constricted portion does not melt with the magnitude of the recording current flowing through the recording element during normal recording, and when it melts, it makes the data storage state of the magnetic nanowire unrewritable, as described in claim 1.

4. Multiple magnetic nanowires, One or two recording elements are arranged orthogonally to a plurality of magnetic nanowires and write data to the magnetic nanowires by a current magnetic field generated when a writing current is supplied during normal recording. A plurality of detection elements provided for each of the magnetic nanowires for detecting data written on the magnetic nanowire, A control unit having a circuit that oversees the entire data recording and playback process, A pulsed current source that supplies pulsed current to the magnetic nanowire, A recording system control unit having a circuit for controlling the recording current flowing through the recording element, A playback system control unit having a circuit for controlling the playback of data detected by the detection element, A write-once magnetic nanowire memory characterized by comprising means for erasing the recording function of the recording element when it is finalized.

5. The means for disabling the recording function of the recording element is: This is a means for automatically stopping the function of the recording system control unit itself when an external command to stop the function is input to the recording system control unit. The write-once type magnetic nanowire memory according to claim 4, characterized in that the data storage state of the magnetic nanowire becomes unrewritable when the aforementioned function stop command is input to the recording system control unit.

6. The means for disabling the recording function of the recording element is: This is a means for severing the path from the central control unit to the recording system control unit when an external command to stop a function is input to the central control unit. The write-once type magnetic nanowire memory according to claim 4, characterized in that the data storage state of the magnetic nanowire becomes unrewritable when the aforementioned function stop command is input to the central control unit.

7. The plurality of magnetic nanowires, the recording element, the plurality of detection elements, the pulse current source, the recording system control unit, the playback system control unit, and the overall control unit are packaged together. The means for disabling the recording function of the recording element is: A portion of the outer perimeter of the package that corresponds to a location where the circuit of the recording control unit itself inside the package can be broken, or This is a partial break-off portion on the outer perimeter of the package, corresponding to a point where the path from the main control unit to the recording system control unit can be broken. The write-once type magnetic nanowire memory according to claim 4, characterized in that the data storage state of the magnetic nanowire becomes unrewritable by folding off the portion of the outer periphery of the package.

8. The means for disabling the recording function of the recording element is: The write-once type magnetic nanowire memory according to claim 4, characterized in that the means for mechanically or electrically disconnecting the power supplied to the recording system control unit is such that the data storage state of the magnetic nanowire becomes unrewritable when the power supplied to the recording system control unit is disconnected.

9. A second recording element is arranged orthogonally to a plurality of magnetic nanowires and writes data detected by the detection element onto the magnetic nanowires by an electric magnetic field, The write-once type magnetic nanowire memory according to any one of claims 1 to 8, further comprising a write-back control unit having a circuit for controlling the recording current flowing through the second recording element.

10. Multiple arrangement surfaces of the multiple magnetic nanowires arranged in a planar manner are stacked, and the recording element and the multiple detection elements are packaged together. The write-once magnetic nanowire memory according to any one of claims 1 to 8, further comprising a magnetic shield covering at least a portion of the package.

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