JP2016219506A - Magnetic thin line device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic thin line device which makes it possible to reduce an amount of applied current required for a shift movement of a magnetic domain while efficiently enabling formation of the magnetic domain.SOLUTION: In a magnetic thin line 11, a magnetic film is formed in a thin line shape, and a magnetic domain D having a magnetization direction different from that of the other portion is formed in a part of the longitudinal direction. A magnetic recording head 30 is provided at a predetermined position on the magnetic thin line 11 and forms the magnetic domain D in the magnetic thin line 11. Electrons for shifting and moving the magnetic domain D in the magnetic thin line 11 are supplied by a pulse current source 20 using a pulse current. Then, a ground layer 16 is provided under the magnetic thin line 11 and at least a part thereof is formed of ferrite.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a magnetic wire device.

  Recording and playback in a hard disk drive device is performed along a track (in the circumferential direction of the disk) by rotating the disk with a spindle motor and moving the magnetic head or laser beam irradiation spot only in the radial direction of the disk. Magnetize (record) in the direction or detect (reproduce) magnetism. In order to increase the speed of recording and reproduction in such a disc, firstly, increasing the rotational speed of the disc is mentioned. However, there is a limit to increasing the rotational speed due to problems such as the time required for track magnetization during recording, the time required for magnetic detection during reproduction, and malfunctions due to disk vibration.

  Therefore, as a technique for moving the recorded data without driving the recording medium, a magnetic wire in which a magnetic film is formed in a thin line shape is formed in an annular shape or the like, and a magnetic field that shifts and moves a magnetic domain formed in the magnetic thin line Recording devices are known. This is because when a magnetic material is formed in a thin line shape and a magnetic field is applied, magnetic domains are generated in the length direction, and when electrons (current) are further supplied in the length direction, the magnetic domains are generated to be separated from each other. This utilizes the characteristic of performing a shift movement so that all the domain walls are moved at an equal distance in the length direction of the magnetic wire. That is, in such a magnetic recording apparatus, each recording and reproducing magnetic head is fixed at a predetermined position on a track (magnetic wire) to record and reproduce the magnetic domain, and the current is reversible from both ends of the track. The desired magnetic domain sandwiched between the domain walls is shifted in the length direction of the magnetic wire (see Patent Document 1 and the like above).

A device that achieves the intended purpose by shifting the magnetic domain using magnetic thin wires, such as this magnetic recording device, will be referred to as a “magnetic thin wire device”.
In a magnetic wire device such as the magnetic recording device described above, a magnetic head is used as means for forming a magnetic domain in the magnetic wire.

  On the other hand, a magnetic head is also used for data recording in a hard disk drive. In hard disk drives, soft magnetic materials are used as a high permeability underlayer for the recording layer of the disk, so that the magnetic flux from the magnetic head concentrates in the data recording area and forms a closed magnetic circuit. The magnetic domains can be formed on the disk with high density.

JP 2011-123943 A

However, in the magnetic wire apparatus, a high magnetic permeability underlayer like the hard disk drive apparatus described above has not been provided. For this reason, the magnetic flux generated by the magnetic head spreads and the magnetic domains cannot be formed efficiently.
Therefore, it is desirable to form a magnetic permeability underlayer as in a hard disk drive device in a magnetic wire device so that magnetic domains can be formed efficiently.

  However, the high magnetic permeability underlayer as used in the hard disk drive device cannot be applied to the magnetic wire device as it is. This is because in the magnetic wire apparatus, a current is passed through the magnetic wire to shift the magnetic domain. In addition, since the underlayer of high permeability used in hard disk drives is generally made of metal materials, when these materials are applied to magnetic wire devices, the current for shifting the magnetic domains is reduced. There is a problem that the current is diverted to the formation and the amount of applied current required for the shift movement of the magnetic domain increases.

  It is an object of the present invention to provide a magnetic wire device that can efficiently form a magnetic domain but requires a small amount of applied current for shifting the magnetic domain.

  In the magnetic wire device according to the present invention, a magnetic film is formed in a thin wire shape, a magnetic wire in which a magnetic domain having a different magnetization direction from other portions is formed in a part of the longitudinal direction, and a predetermined position on the magnetic wire. A magnetic recording head for forming the magnetic domain in the magnetic wire; a pulse current source for supplying electrons for shifting the magnetic domain in the magnetic wire by a pulse current; and the magnetic wire provided below the magnetic wire. And an underlayer formed of ferrite.

Ferrite provided as a base layer under the magnetic fine wire is a material having high magnetic permeability. For this reason, when a magnetic field is generated by the magnetic recording head, the magnetic flux can be concentrated by the action of the high permeability underlayer, and the magnetic domain can be formed efficiently.
In other words, the magnetic layer is formed in the path of magnetic recording head → magnetic wire → underlayer → magnetic recording head by the action of the high permeability underlayer, and a steep magnetic field gradient is formed by making the magnetic circuit small. Even with a small magnetic field, magnetic domains can be formed efficiently.
On the other hand, since the ferrite underlayer is an oxide insulator, even if a pulse current is supplied from the pulse current source to the magnetic wire, the current can be suppressed from flowing through the underlayer. Therefore, the pulse current source can use less power for the shift of the magnetic domain.

  According to the present invention, it is possible to reduce the amount of applied current required for the shift movement of the magnetic domains while efficiently forming the magnetic domains in the magnetic wire apparatus.

It is explanatory drawing explaining the magnetic recording medium of the magnetic wire apparatus which concerns on one Embodiment of this invention. It is AA sectional drawing of FIG. It is explanatory drawing explaining the pulse current source and magnetic recording head of the magnetic wire apparatus which concern on one Embodiment of this invention. It is explanatory drawing explaining the magnetic wire apparatus used as a comparative example. It is explanatory drawing of the conventional hard disk drive apparatus. It is explanatory drawing explaining the magnetic wire apparatus used as a comparative example.

  As shown in FIGS. 1 to 3, a magnetic wire device 1 according to an embodiment of the present invention includes a magnetic recording medium 10, a pulse current source 20, a magnetic recording head 30, a magnetic reproducing head, a synchronization unit 40, and the like. It has.

(Magnetic recording medium)
As shown in FIG. 1, the magnetic recording medium 10 includes a magnetic fine wire 11, a substrate 12, an insulating layer 13, a positive electrode 14, a negative electrode 15, a base layer 16 (see FIG. 2), and the like.

  As shown in FIG. 1, a magnetic thin line 11 formed by forming a magnetic film in a thin line shape on a disk (annular) substrate 12 is provided as a data recording (storage) area. As will be described later, the magnetic thin wire 11 is recorded as one of magnetizations in two directions in which binary data 0 and 1 are different (for example, upward and downward directions perpendicular to the plate surface of the substrate 2). The In the magnetic recording medium 10, the magnetic fine wires 11, 11,... Are concentrically formed on the substrate 12 with the insulating layer 13 interposed therebetween in a plan view. Specifically, one magnetic wire 11 is formed in a C-shape that lacks a part of the ring in plan view. In FIG. 1, six magnetic thin wires 11 are omitted and an intermediate portion between the outer periphery and the inner periphery is indicated by a blank, but practically, the magnetic thin wires 11 have an outer shape (a substrate 2). ) And are provided at a constant pitch. Further, the magnetic recording medium 10 is provided with a positive electrode 14 and a negative electrode 15 at one end and the other end of the magnetic wire 11, respectively.

In the magnetic recording medium 10, data is written (recorded) and reproduced (read) using a magnetic head for recording and reproduction, as in the current hard disk drive device. The magnetic recording head 30 for recording (FIG. 3) writes data in the writing area 11w of each magnetic wire 11, and the magnetic reproducing head (not shown) for reproduction uses the reproducing area of each magnetic wire 11. Data is reproduced at 11r.
As shown in FIG. 2, a base layer 16 is formed on the substrate 12, and each magnetic wire 11 is formed on the base layer 16. An insulating layer 13 is formed between adjacent magnetic fine wires. In FIG. 2, since the state in which the insulating layer 13 is not formed is illustrated, the position where the insulating layer 13 is formed is indicated by a virtual line.

(Magnetic wire)
The magnetic wire 11 is a recording area for recording data on the magnetic recording medium 10. The magnetic wire (track) 11 is made of a ferromagnetic material, and has a magnetization in a direction perpendicular to the film surface, and is preferably made of, for example, a perpendicular magnetic anisotropic material. The magnetic thin wire 11 can be specifically exemplified by being formed using a laminated film of transition metal such as Ni, Fe, Co, etc., its alloy, Pd, Pt or the like. The recording capacity of the magnetic recording medium 10 can be increased as the width and interval of the magnetic thin wire 11 are shorter, and the so-called track pitch is narrower. Further, the length in the length direction (track length) of the magnetic wire 11 is not particularly limited, but may be any length that is sufficiently long with respect to the thickness and the length in the width direction. In the magnetic recording medium 10, the magnetic fine wires 11 become longer toward the outer periphery and are not uniform. However, the magnetic recording medium 10 only needs to be sufficiently long with respect to the thickness and the length in the width direction.

  A positive electrode 14 and a negative electrode 15 are connected to both ends of the magnetic wire 11. The positive electrode 14 and the negative electrode 15 are made of a metal such as Cu, Al, Au, Pt, or Ag, or a general electrode metal material such as an alloy thereof. In FIG. 1, the positive electrode 14 and the negative electrode 15 are stacked on the magnetic wire 11 at both ends of each magnetic wire 11.

(Pulse current source)
As shown in FIG. 3, the pulse current source 20 is means for intermittently shifting the domain wall DW (magnetic domain D) by supplying current (electrons) in the longitudinal direction of the magnetic wire 11. In FIG. 3, the magnetic wire 11 is schematically shown in a straight line.

  The pulse current source 20 is connected to the positive side and the negative side of the positive electrode 14 and the negative electrode 15 at both ends of the magnetic thin wire 11 of the magnetic recording medium 10, and one of binary data (for example, “0”) is connected to the magnetic thin wire 11. ) And a domain current DW (magnetic domain D) generated between the area recorded with the other binary data (for example, “1”) is intermittently shifted. Is a means for supplying the wire in the thin wire direction (length direction) from one end of the magnetic thin wire 11 to the other end.

  By this pulse current, the area in which data is recorded moves in the magnetic wire 11 along the direction of the magnetic wire 11 (the direction opposite to the pulse current (electron movement direction)). In this example, since the pulse current flows through the magnetic wire 11 from the upper side of the drawing to the lower side of the drawing in FIG. 3, the electrons move from the lower side of the drawing to the upper side of the drawing. Shifts the magnetic thin wire 11 from the lower side to the upper side. Depending on the structure of the magnetic wire 11, the magnetic domain D may move in the same direction as the pulse current (the direction opposite to the electrons).

(Magnetic recording head)
The magnetic recording head 30 is means for recording data in the writing area 11w of the magnetic thin wire 11, and records generated data on the magnetic thin wire 11 by signal processing similar to writing in the hard disk drive device.

  That is, the magnetic recording head 30 has a magnetic thin wire 11 in a stationary state in an intermittent shift movement of the domain wall DW in the magnetic thin wire 11 in synchronization with the pulse current supplied from the pulse current source 20 in the writing region 11 w of the magnetic thin wire 11. 11 is a means for recording data in a data area reaching 11 write areas 11w. In the magnetic recording head 30, data is written by changing the state of the magnetic domain D of the magnetic wire 11 using a magnetic field generated from the recording head or spin injection magnetization reversal. Thereby, data is recorded on the magnetic wire 11, and the magnetic wire 11 becomes a recording area of the magnetic recording medium 10. In FIG. 3, the magnetic reproducing head is not shown because the configuration is omitted and the apparatus is shown.

  The data recording element of the magnetic recording head 30 is integrated with the magnetic wire 11 and has a spin structure having a CPP-GMR (Current Perpendicular to Plane-Giant MagnetoResistance) element type or a TMR (Tunneling MagnetoResistance) element type. It constitutes an injection magnetization reversal element structure and functions as a data recording element. The magnetic recording head 30 may be a known magnetic head as long as it can record (write) data.

(Synchronous part)
The synchronization unit 40 is a device for synchronizing the pulse current source 20 and the magnetic recording head 30. That is, the synchronization unit 40 synchronizes with the pulse current supplied from the pulse current source 20 in the write region 11w of the magnetic thin wire 11, and at the time of stationary in the intermittent shift movement of the domain wall DW in the magnetic thin wire 11, The pulse current source 20 and the magnetic recording head 30 are synchronized so that 30 can record data in the data area reaching the writing area 11 w of the magnetic wire 11.

(Underlayer)
The underlayer 16 is a member for efficiently forming the magnetic domain D by the magnetic recording head 30.
As described above, the underlayer 16 is formed on the substrate 12, and each magnetic wire 11 is formed on the underlayer 16.

  In the present embodiment, as the material of the underlayer 16, at least a part thereof is ferrite that is an oxide insulator, more specifically, soft ferrite. More specifically, soft ferrite materials such as Mn—Zn ferrite, Ni—Zn ferrite, Mn—Ni ferrite, and Ni—Zn—Co ferrite can be used.

(Manufacturing method of underlayer)
The underlayer 16 can be formed using an ion beam sputtering method, a reactive sputtering method, an RF sputtering method, a plating method, a spin spray method, or the like. By depositing the underlayer 16 on the substrate 12 by such means and subsequently continuously depositing the material of the magnetic wire 11, the magnetic wire structure can be formed by electron beam lithography or the like.

  (Operation of magnetic recording device)

As shown in FIG. 3, in this embodiment, ferrite, more specifically, soft ferrite is used as the underlayer 16. Soft ferrite is a material with high magnetic permeability. For this reason, when a magnetic field is generated by the magnetic recording head 30, the magnetic flux can be concentrated by the action of the high permeability underlayer 16 and the magnetic domain D can be formed efficiently.
That is, the magnetic path m1 is formed in the path of the magnetic recording head 30 → the magnetic thin wire 11 → the underlayer 16 → the magnetic recording head 30 by the action of the high permeability underlayer 16, and the magnetic circuit is made small, so that the steepness is increased. Therefore, the magnetic domain D can be formed efficiently even with a small magnetic field.

Since the underlayer 16 of soft ferrite is an oxide insulator, even if a pulse current is supplied from the pulse current source 20 to the magnetic wire 11, current can be suppressed from flowing through the underlayer 16. Therefore, the pulse current source 20 can use less power for the shift movement of the magnetic domain D.
In the example of FIG. 2, the base layer 16 is entirely formed on the substrate 12, but it may be formed only on the lower part of the magnetic wire 11.

(Comparative example)
On the other hand, in the existing magnetic wire apparatus, the underlayer 16 is not formed, and the substrate 2 or the like is formed immediately below the magnetic wire 11.
The formation of the magnetic domain D by the magnetic recording head 30 when the underlayer 16 is not formed in the magnetic wire device 1 of this embodiment will be described with reference to FIG.

  That is, as shown in FIG. 4, when the underlayer 16 is not formed as in the existing magnetic wire device, the magnetic flux m <b> 2 generated from the magnetic recording head 30 spreads without concentrating and the magnetic domain D by the magnetic recording head 30. A large magnetic field is required for recording. For this reason, the recording efficiency of the magnetic domain D by the magnetic recording head 30 is poor.

On the other hand, as shown in FIG. 5, in a magnetic disk 101 of an existing hard disk drive device, a high permeability underlayer (in-plane magnetization soft magnetic layer) 103 is formed under a track (recording layer) 102. . When a magnetic field is generated by the magnetic head 104, the magnetic flux can be concentrated by the action of the high permeability base layer 103, and the magnetic domain D1 can be efficiently formed.
This is because the magnetic path m3 is formed by the path of the magnetic head 104 → track 102 → underlayer 103 → magnetic head 104, and the magnetic circuit is made small to form a steep magnetic field gradient, and the magnetic domain D1 can be formed even with a small magnetic field. It enables it to be formed efficiently.

Therefore, in the magnetic wire device which is a magnetic wire device, in order to increase the recording efficiency of the magnetic domain D, it is conceivable to provide a member corresponding to the base layer 103 in the existing hard disk drive device as the base layer 16a.
However, the high magnetic permeability underlayer 103 used in the existing hard disk drive device uses a metal material such as Co—Zr—Nb or Co—Zr—Ta. FIG. 6 shows an example in which the underlayer 16a formed of these metal materials is applied to a magnetic wire device.

In this configuration, when the pulse current source 20 is passed through the magnetic wire 11, as shown in FIG. 6, not only the current I _NW flows through the magnetic wire 11, but also the current I _UL is applied to the underlying layer 16a made of a metal material. Will flow. As a result, of the pulse current supplied from the pulse current source 20, the current contributing to the shift movement of the magnetic domain D in the magnetic wire 11 is reduced. Therefore, the pulse current source 20 has a problem that a large amount of power must be consumed to shift the magnetic domain D. Since the amount of current increases, a problem due to heat generation may occur.
The problems of these comparative examples can be solved by using ferrite for the underlayer 16 as described above in “Operation of Magnetic Recording Device”.

DESCRIPTION OF SYMBOLS 1 Magnetic wire apparatus 11 Magnetic wire 16 Underlayer 20 Pulse current source 30 Magnetic recording head D Magnetic domain

Claims (2)

A magnetic thin film in which a magnetic film is formed in a thin line shape, and a magnetic domain having a different magnetization direction from the other part is formed in a part of the longitudinal direction;
A magnetic recording head provided at a predetermined position on the magnetic wire, and forming the magnetic domain in the magnetic wire;
A pulse current source for supplying electrons for shifting the magnetic domain in the magnetic wire by a pulse current;
A magnetic wire apparatus comprising: an underlayer provided under the magnetic wire and made of ferrite.   The magnetic wire device according to claim 1, wherein the underlayer uses soft ferrite as the ferrite.

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