JP2014032730A - Magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic recording medium in which a magnetic fine line is defined as a track as the recording region of data, and the supply of pulse currents allows the shift movement of a magnetic domain in a direction of a fine line in the track, and which is capable of increasing recording density regardless of working accuracy.SOLUTION: A magnetic fine line 1 of a magnetic recording medium is divided into two tracks Tr1 and Tr2 in a direction of fine line thickness by a groove part 1d extended in a direction of the fine line, and a plurality of magnetic domains are continuously generated in the direction of the fine line in each of the tracks Tr1 and Tr2. In the magnetic fine line 1, the adjacent magnetic domains generated in each of the tracks Tr1 and Tr2 are prevented from being moved to the adjacent track since a magnetic wall for partitioning those magnetic domains from each other is locked by the groove part 1d, and DC pulse currents to be supplied to the magnetic fine line 1 allows the shift movement of the magnetic domains only in a direction of the fine line.

Description

  The present invention relates to a magnetic recording medium in which a track is formed of a thin linear magnetic material.

  In storage devices such as hard disk drives (HDD), with the increase in the amount of information to be handled, higher recording density and higher speed of recording and reproduction are being promoted. As the recording density is increased, the tracks of recording media such as magnetic disks used for HDDs are narrowed, and the length of one data (1 bit) in the track is shortened. In order to detect magnetism, a recording / reproducing method is a magnetic method using a magnetic head composed of a magnetoresistive effect element such as a GMR (Giant MagnetoResistance) element or a TMR (Tunnel MagnetoResistance) element, or A magneto-optical method using laser light irradiation is applied.

  Recording and reproduction on such a magnetic disk are carried out along the track (in the circumferential direction of the disk) by rotating the disk with a spindle motor and moving the magnetic head or the laser beam irradiation spot only in the radial direction of the disk. ) Magnetize (record) in a predetermined direction, or detect (reproduce) magnetism. In order to increase the speed of recording and reproduction in such a disc, firstly, the rotational speed of the disc is increased. 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 method of moving recorded data without driving the recording medium, Patent Document 1 discloses that a track is formed by forming a thin wire-like magnetic body (hereinafter appropriately magnetic thin wire) into a U-shape or the like. A memory device is disclosed. This is because when a magnetic material is formed in a thin wire shape, magnetic domains are generated in the length direction, and when a current is further supplied in the length direction, all the domain walls generated to separate the magnetic domains are the length of the magnetic wire. This utilizes the characteristic of shifting in the same distance in the direction (see Non-Patent Documents 1 and 2). That is, in the memory device described in Patent Document 1, each of the recording and reproducing magnetic heads is fixed at a predetermined position on the track (magnetic thin wire) (the U-shaped top portion in Patent Document 1). Current is reversibly supplied from both ends to move a desired magnetic domain sandwiched between the domain walls to a position facing the magnetic head.

  Patent Documents 2 to 5 disclose magnetic recording media in which a plurality of magnetic thin wires are formed concentrically like a track such as a current magnetic disk. These methods vary depending on the shape of the magnetic material (line width, etc.) and the current to be supplied, but the moving speed of the domain wall is extremely high, from several tens m / s to about 250 m / s. It is expected to exceed the playback speed by.

US Pat. No. 6,834,005 JP 2011-1000051 A JP 2011-123943 A JP 2012-84206 A JP 2012-53957 A

T. Koyama et al., “Control of Domain Wall Position by Electrical Current in Structured Co / Ni Wire with Perpendicular Magnetic Anisotropy”, Appl. Phys. Express, 2008, Volume 1, Issue 10, pp.101303 Xin Jiang et al., “Enhanced stochasticity of domain wall motion in magnetic racetracks due to dynamic pinning”, Nature Communications, 2010, Volume 1, pp.1-5

  Magnetic recording media are required to have a higher recording density, and one example is a narrower track pitch. However, the magnetic recording media that enable high-speed reproduction by magnetic domain shift movement as in Patent Documents 2 to 5 are supplied with current in order to make the magnetic wire a single track and the magnetic wire width direction as a single magnetic domain. Therefore, it is necessary to insulate the magnetic wires by providing them one by one apart. Accordingly, the track pitch of the magnetic recording medium, that is, the track (magnetic fine wire) width and the distance between the tracks is regulated by the processing accuracy in the lithography technique and the etching technique.

  The present invention was devised in view of the above problems, and provides a magnetic recording medium for shifting a magnetic domain within a track formed of magnetic thin wires, which can increase the recording density regardless of processing accuracy. Is an issue.

  In order to solve the above-mentioned problems, the inventors of the present invention form a constriction (notch) or the like to locally increase the saturation magnetization in order to prevent a shift in the magnetic domain shift movement. Thus, attention is paid to the fact that the domain wall is locked at a fixed position when the current is stopped (for example, see Patent Documents 1, 2, and 4). This is because a magnetic material with a simple shape such as a thin wire has a domain wall easily generated in a part where there is a minute deformation part such as a wrinkle or a bend, or a part where magnetic characteristics such as saturation magnetization are locally different. Also, it is easy to be locked. From this, the present inventors divided two or more tracks into one magnetic thin wire that conventionally constituted one track by dividing the magnetic fine wire in the thin wire width direction by a groove or the like along the thin wire direction. I found it to be provided.

  That is, the magnetic recording medium according to the present invention comprises one or more magnetic wires formed by forming a magnetic material on a substrate in a thin line shape, and binary data is recorded on the magnetic wires as different magnetization directions, respectively. On what is generated. In the first magnetic recording medium according to the present invention, at least one of the upper surface and the lower surface of the magnetic fine wire extends in the fine line direction at one or more boundaries of the fine wire in the fine wire width direction. A formed continuous recording area delimiter is provided. In the magnetic recording medium, a plurality of the magnetic domains are continuously generated in the thin line direction in each of the regions where the magnetic thin line is divided in the thin line width direction with the continuous recording region delimiter as a boundary, and current is supplied. Thus, in all the divided regions, the domain walls separating the magnetic domains move in the thin line direction.

  Further, in the second magnetic recording medium according to the present invention, a continuous recording area delimiter having a saturation magnetization height different from that of the other areas is provided in one or more positions where the magnetic thin line delimits in the thin line width direction. It is extended to. In the magnetic recording medium, a plurality of the magnetic domains are continuously generated in the thin line direction in each of the regions where the magnetic thin line is divided in the thin line width direction with the continuous recording region delimiter as a boundary, and current is supplied. Thus, in all the divided regions, the domain walls separating the magnetic domains move in the thin line direction.

  With this configuration, in the first and second magnetic recording media, one magnetic wire is divided into two or more regions in the thin wire width direction, and data is continuously recorded using each region as a so-called track. In addition, the number of tracks per area, that is, the recording density can be improved without using fine processing of the magnetic wire.

  Furthermore, in the first and second magnetic recording media according to the present invention, the magnetic fine wires are arranged in the fine line direction so that the magnetic walls are locked at one or more boundaries of the fine line direction when the current is stopped. There may be provided a deformed portion having a vertical cross-sectional shape different from that of another region, or a saturation magnetization variation portion having a saturation magnetization height different from that of the other region.

  With this configuration, when the current in the pulse current is stopped, the domain wall reaches the deformed portion or saturation magnetization mutated portion provided in advance on the magnetic wire and stops, so that a small amount of displacement is accumulated in the shift of the magnetic domain due to the pulse current. It is possible to prevent errors caused by

  According to the magnetic recording medium of the present invention, it is possible to increase the recording density by narrowing one track and increasing the number of mounted tracks regardless of the processing limit of the magnetic wire.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram of the magnetic recording medium which concerns on this invention, (a) is a top view, (b) is a partial step | plane view of the magnetic recording medium which concerns on 1st Embodiment, and is the AA line arrow of (a). It corresponds to a sectional view. It is a perspective view of a magnetic wire explaining the configuration of the magnetic recording medium according to the present invention. It is a schematic diagram for demonstrating the data writing in the magnetic fine wire of the magnetic recording medium based on this invention, and the movement of a magnetic domain, and is a top view. It is a fragmentary sectional view equivalent to the AA line arrow sectional view of Drawing 1 (a), (a) is a mimetic diagram concerning a modification of a 1st embodiment, and (b) is a 2nd implementation. It is a schematic diagram of the magnetic recording medium which concerns on a form. It is a fragmentary sectional view equivalent to an AA line arrow sectional view of Drawing 1 (a), (a) is a mimetic diagram of a magnetic recording medium concerning a 3rd embodiment, and (b) is a modification of a 3rd embodiment. FIG. 6C is a schematic diagram of a magnetic recording medium according to another example of the third embodiment, and FIG. It is a photograph of the sample of the magnetic fine wire of an Example, (a) is an atomic force microscope image photograph, (b) is a magnetic force microscope image photograph. It is a photograph of the sample of the magnetic fine wire of an Example, (a) is an atomic force microscope image photograph, (b) is a magnetic force microscope image photograph. It is a photograph of the sample of the magnetic fine wire in which the dot-like dent was formed, (a) is an atomic force microscope image photograph, (b) is a magnetic force microscope image photograph.

  Hereinafter, embodiments for realizing a magnetic recording medium according to the present invention will be described with reference to the drawings.

[First Embodiment]
As shown in FIG. 1A, a magnetic recording medium 10 according to the first embodiment of the present invention includes a magnetic wire 1 formed by forming a magnetic material on a disk (annular) substrate 2 in a thin line shape. Is provided as a data recording (storage) area. As will be described later, binary data, that is, “0” or “1” data is recorded on the magnetic wire 1 as either of two different directions of magnetization. In the magnetic recording medium 10, the magnetic thin wires 1, 1,... Are concentrically formed on the substrate 2 with the insulating layer 6 interposed therebetween in plan view. Specifically, the single magnetic wire 1 is formed in a C shape lacking a part of the ring in plan view. In FIG. 1 (a), the number of magnetic thin wires 1 is omitted to six, and the intermediate portion between the outer periphery and the inner periphery is indicated by a blank, but the width and interval (pitch) of the magnetic thin wire 1 is practically the outer shape. It is formed extremely small with respect to (substrate 2) and is provided at a constant pitch. Further, the magnetic recording medium 10 is provided with a positive electrode 31 and a negative electrode 32 connected to one end and the other end of the magnetic wire 1. As described above, in the present embodiment, the magnetic recording medium 10 is referred to as a magnetic disk 10 as appropriate because the outer shape of the magnetic recording medium 10 is a disk shape based on the disk-shaped substrate 2 as in the current magnetic disk. The magnetic recording medium 10 writes and reproduces (reads) data using a recording / reproducing apparatus (not shown) provided with a magnetic head for recording and reproducing, as in the case of current magnetic disks. Is called.

  As shown in FIG. 1B, the magnetic thin wire 1 has a single groove (continuous recording area dividing portion, groove portion 1d) along the length direction of the magnetic thin wire 1 (hereinafter referred to as the thin wire direction) on the upper surface. It is formed and divided into two regions Tr1 and Tr2 in the fine line width direction (the radial direction of the magnetic recording medium 10) with this groove as a boundary.

  Here, a sample of a magnetic thin wire was produced, and it was investigated that a magnetic domain could be divided and generated in the thin wire width direction according to the shape of the magnetic thin wire. A 250 nm width magnetism that forms a single magnetic domain in the direction of the fine line width of an underlayer made of Ru (3 nm) and a multilayer film (total thickness of about 40 nm) of [Co (0.3 nm) / Pd (1.2 nm)] × 21 Processed into fine wires. A diamond probe used for the nanoindentation function of the atomic force microscope (AFM) is pushed into the magnetic wire to form a plurality of dot-like recesses having a depth of about 10 nm around the center in the width direction of the upper surface. A sample was made. FIG. 8A shows an AFM image photograph of the sample, and shows a portion where a dent is formed by an arrow in the drawing. Initially, a magnetic field of 1 kG is applied upward as a sample to saturate the entire magnetization to make it upward, and then the downward direction is 0.5 kG, which is slightly smaller than the coercive force of the magnetic wire (Co / Pd multilayer film) The magnetic field was applied. The surface of this sample was imaged and observed with a magnetic force microscope (MFM). In the MFM image photograph shown in FIG. 8B, the magnetic thin wire shows white (upward) / black (downward) contrast for each magnetic domain depending on whether the magnetization direction is upward or downward.

  As shown in FIG. 8 (b), it was confirmed that the magnetic domain was divided into two in the fine line width direction in the portion where the dent was formed. In this way, even for a sufficiently narrow magnetic thin wire that generates a single magnetic domain in the width direction, a magnetic domain that is divided in the thin wire width direction is generated by providing a location for locking the domain wall by providing a location for locking the domain wall. can do. From this, by forming the groove portion 1d having the action of locking the magnetic domain wall on the magnetic wire 1, each of the two regions Tr1 and Tr2 divided in the thin wire width direction by this groove portion 1d is made of the conventional magnetic wire. Thus, a plurality of magnetic domains continuous in the thin line direction can be generated.

  In the magnetic recording medium 10, data is continuously recorded in the thin line direction in each of these two regions Tr1 and Tr2 of the magnetic thin line 1, and one data is stored in a predetermined unit length as shown in FIG. The magnetic domain is (bit length Lb). That is, the areas Tr1 and Tr2 are respectively referred to as a first track Tr1 and a second track Tr2 as appropriate because they are similar to tracks that are data recording areas of the current magnetic disk. In FIG. 2 and FIG. 3 to be described later, the magnetic fine wire 1 is represented by a straight line for the sake of simplicity. Hereinafter, each element constituting the magnetic recording medium 10 will be described in detail.

(Magnetic wire)
The magnetic wire 1 is formed by forming a magnetic body (magnetic material) into a thin wire shape that is sufficiently long with respect to the thickness and width, and the thin wire shape (plan view shape) is a straight line that is not bent, or the thickness and width. The curve should be sufficiently gentle with respect to the direction length. In the magnetic recording medium 10 whose outer shape is a disk shape as in the present embodiment, the magnetic fine wire 1 becomes a sufficiently long and gentle curve by forming a shape along the circumference of the concentric circle with the outer shape. The outer diameter of the magnetic recording medium 10 can be made longer, and the magnetic recording medium 10 can be efficiently arranged on the entire upper surface of the magnetic recording medium 10 to increase the recording density. Therefore, the magnetic wire 1 does not have to have the same wire length in the magnetic recording medium 10, and the magnetic wire 1 is made longer as it is provided closer to the outer periphery, so that the entire area of the magnetic recording medium 10 can record data (capacity). Should be increased. Further, the magnetic recording medium is not limited to a disk shape, and may be, for example, a plate having a rectangular shape in a plan view. In this case, the magnetic thin wires may be formed in straight lines parallel to each other.

  The magnetic fine wire 1 is formed of a magnetic material like the recording layer of the current magnetic disk, and a perpendicular magnetic anisotropic material suitable for miniaturization is preferably applied. As such a material, a known ferromagnetic material can be applied. Specifically, a multilayer film such as a Co / Pd multilayer film in which transition metals such as Co and any one of Pd, Pt, and Cu are alternately laminated. In addition, an alloy (RE-TM alloy) of a rare earth metal such as Tb—Fe—Co, Gd—Fe and a transition metal can be used. These materials are formed into a film by a known method such as a sputtering method, and are formed into the following fine wire shape by photolithography and etching or lift-off to form the magnetic wire 1. In the present embodiment, since the magnetic wire 1 is a perpendicular magnetic anisotropic material, it shows an upward or downward magnetization direction as shown in FIG.

  If the magnetic thin wire 1 has a thickness (film thickness) of 70 nm or less and a width of 300 nm or less, it is preferable because the magnetic domains are easily divided only in the thin wire direction. Further, the magnetic recording medium 10 can have a higher recording density as the pitch of the magnetic wire 1 is narrower, that is, the width is smaller (thin). The magnetic wire 1 is divided into two regions Tr1 and Tr2 in the width direction by the groove 1d to generate magnetic domains, respectively. However, the magnetic wire 1 is equal to or more than a conventional magnetic wire that easily forms a single magnetic domain in the width direction. It is preferable to double the recording density as a narrow width. In addition, the magnetic domain (domain wall) is moved in the direction of the fine wire by supplying current to the magnetic wire 1 in the direction of the fine wire, and the moving speed is increased in proportion to the current density per cross-sectional area. The smaller the thickness and width (cross-sectional area), the faster the magnetic domain can be moved with a smaller current. On the other hand, for data storage (magnetization retention), it is preferable that the magnetic wire 1 has a certain thickness and width. Specifically, the thickness is 5 nm or more and the width is one per track Tr1, Tr2 ( It is preferable that the thickness is 10 nm or more, that is, 20 nm or more. In addition, the thickness and width of the magnetic fine wire 1 indicate the size of the portion where the upper and lower surfaces and the side surfaces are flat, other than the deformed portion such as the groove 1d.

  As shown in FIG. 1B, the magnetic fine wire 1 has one groove (groove portion 1d) formed on the upper surface at the center in the width direction over the whole thin wire direction. As described above, a magnetic body formed in a thin line shape having a width of 300 nm or less is likely to form a single magnetic domain in the width direction. However, a domain wall is easily generated in such a portion having a small cross-sectional area. Therefore, the magnetic fine wire 1 is likely to be in a state where a magnetic domain is generated so as to be separated at a position where the groove portion 1d is formed. Therefore, the magnetic wire 1 can generate a magnetic domain in each of the two regions (tracks) Tr1 and Tr2 that are equally divided in the width direction with the groove 1d as a boundary. Hereinafter, a portion (in the vicinity of the boundary) that divides the magnetic wire in the thin wire width direction as in the groove portion 1d of the magnetic wire 1 will be appropriately referred to as a track partition portion. The number of the groove portions 1d in the magnetic thin wire 1 is not particularly limited, but if there is one, the number of tracks provided in one magnetic thin wire 1 is 2, and any of the tracks (Tr1, Tr2) includes the side end of the magnetic thin wire 1. It is provided facing the insulating layer 6. With such a configuration, as will be described later, the magnetic recording medium 10 has a magnetic head (recording head 71 in FIG. 2) for writing and reproducing data on only one of the tracks Tr1 and Tr2. , 72) can be easily opposed.

  The groove 1d is formed continuously over the entire area where data is recorded, including at least areas where data is written and reproduced (writing area 1w, reproduction area 1r). The groove 1d is preferably provided in the center of the magnetic thin wire 1 so that the widths of the tracks Tr1 and Tr2 are uniform, but at least the tracks Tr1 and Tr2 have a width corresponding to writing and reproduction. It is only necessary that the groove 1d is provided at the position. Note that the magnetic domains of the tracks Tr1 and Tr2 shift and move at the same speed even if the widths are uneven.

  In the magnetic recording medium 10 according to the present embodiment, the length (bit length Lb) in the thin line direction in which one data is recorded in the magnetic thin line 1 (tracks Tr1 and Tr2) is not particularly defined. As will be described, it can be set by the pulse width of the pulse current. However, the bit length Lb is preferably 10 nm or more in the same way as the widths of the tracks Tr1 and Tr2 in order to store data, and more than the length at which magnetism is accurately detected in the reproduction region 1r described later. It is preferable.

  Here, in general, the thickness of the domain wall (length in the direction of the thin wire) is extremely narrow (short) with respect to the magnetic domain, and the thickness of the magnetic wire 1 and the length of the magnetic domain, that is, the width of the tracks Tr1 and Tr2 (here, Although it depends on the width of magnetic thin wire 1) and the length of one data in the thin wire direction (bit length Lb), it is about 5 to 100 nm. In order to lock such a domain wall, the magnetic thin wire 1 has a thin wire width direction length of a deformed region, here, the groove width of the groove portion 1d (the thin wire width direction length at the opening of the groove portion 1d), It is preferable that the thickness is not less than the thickness of the domain wall and not more than 10 times. Specifically, the groove width of the groove portion 1d is in the range of about 10 to 100 nm, and is 1/2 or less of the width of the tracks Tr1 and Tr2 (1/4 or less of the width of the magnetic wire 1), 1 / of the bit length Lb. About 10 to 2 times is preferable. On the other hand, if the groove 1d is too wide, depending on the depth, the inclination is too gentle and the action of locking the domain wall is reduced.

  In the magnetic wire 1, the amount of change is preferably 2% or more in order to keep the domain wall suitably locked (not moved out of the groove 1 d) at the deformed portion such as the groove 1 d. . Specifically, when the thickness of the magnetic wire 1 is 50 nm, the depth of the groove 1d is preferably 1 nm or more (the thickness of the thinnest part is 49 nm or less). On the other hand, the upper limit of the depth of the groove 1d is not particularly limited, and may be any depth as long as the groove width is formed within the above-described range with a sufficient inclination to lock the domain wall. Further, the cross-sectional shape (cross section perpendicular to the thin line direction) of the groove 1d is not particularly defined, and examples thereof include a V shape (inverted triangle), a U shape, a rectangle, and an inverted trapezoid shape. However, it is preferable that the cross-sectional shape of the groove 1d substantially coincides with the entire length of the magnetic wire 1 in order to make the action of locking the domain wall in the magnetic wire 1 uniform. Such a groove portion 1d can be formed by etching a resist mask or a resin mask by nanoimprint, in which a region for forming the groove portion 1d is thinned or vacated, on the magnetic wire 1.

The write regions 1w ₁ and 1w ₂ are regions for setting the magnetism of the magnetic wire 1 to the magnetization direction corresponding to the data in order to record data on the tracks Tr1 and Tr2 of the magnetic wire 1, respectively. The length is set to a bit length Lb or more, and in this region, the structure of the magnetic fine wire 1 is adapted to the recording method as required. In FIG. 1A, an area including the write areas 1w ₁ and 1w ₂ is collectively expressed as a write area 1w. Specifically, for example, as in the current recording method on a magnetic disk, as shown in FIG. 2, a first recording head 71 and a second recording head 72 (only the main magnetic pole portion) that are magnetic heads for writing are used. When the external magnetic field is applied using the writing means as the writing means, the area including the writing areas 1w ₁ and 1w ₂ below the magnetic wire 1 (the side opposite to the side facing the recording heads 71 and 72) or magnetic The entire thin wire 1 has a laminated structure in which a soft magnetic layer is provided via a nonmagnetic layer (not shown). The soft magnetic layer forms a magnetic path for the external magnetic field from the recording heads 71 and 72 to form a perpendicular write magnetic flux on the magnetic wire 1. By adopting such a configuration, for example, in FIG. 2, the magnetic thin line 1 whose magnetization is in the downward direction in the initial state (before writing) is applied, and the upward magnetic field is applied by the first recording head 71 in the writing area 1w ₁ . Thus, the magnetization is reversed in the upward direction, and the second recording head 72 applies a downward magnetic field in the writing area 1w ₂ to make the magnetization downward.

Here, each of the first recording head 71 and the second recording head 72 includes a main magnetic pole, a sub magnetic pole, a coil, and the like, and requires a certain amount of space. Therefore, adjacent tracks Tr1, It is difficult to make the main pole face the same position in the direction of the thin line of Tr2, and the applied magnetic fields from each other will affect each other. Therefore, as shown in FIG. 2, the magnetic thin wire 1 region where the recording heads 71 and 72 are opposed, that is, the writing regions 1 w ₁ and 1 w ₂ are provided with a distance shifted in the thin wire direction. When the write areas 1w ₁ and 1w ₂ are shifted in the direction of the thin line in the magnetic thin line 1 as described above, it is preferable to shift by an integral multiple of one data (bit length Lb). Here, the write area 1w ₂ of the second track Tr2 is provided behind the write area 1w ₁ of the first track Tr1 in the direction of moving the magnetic data for 4 data (4Lb) (left side in FIG. 2) (FIG. 2). 3 (a)). As described above, the lengths of the write areas 1w ₁ and 1w _{2 in} the thin line direction and the positions on the magnetic thin lines 1 (tracks Tr1 and Tr2) may correspond to the recording method, processing accuracy, and the like.

In addition, in all the magnetic thin wires 1 of the magnetic recording medium 10, the writing areas 1w ₁ and 1w ₂ are provided at positions along one line in the thin line width direction (the radial direction of the magnetic recording medium 10). It is preferable (refer Fig.1 (a)). With such a magnetic recording medium 10, the recording / reproducing apparatus moves all the magnetic wires 1 by moving an arm (not shown) supporting the recording heads 71 and 72 only in the radial direction of the magnetic recording medium 10. Data can be written to the write area 1w (1w ₁ , 1w ₂ ).

The reproduction area 1r is an area for detecting the magnetization direction of the magnetic domain generated by writing data in the tracks Tr1 and Tr2 of the magnetic wire 1 and, as shown in FIG. 1A, the write area 1w (1w ₁ , 1 w ₂ ), it is preferable that all the magnetic wires 1 are provided on a straight line along the diameter of the magnetic recording medium 10. Although the reproduction area 1r is integrally shown in FIG. 1A, the reproduction area 1r ₁ and the second area in the first track Tr1 are the same as the writing areas 1w ₁ and 1w ₂ shown in FIG. in the reproducing area 1r ₂ in the track Tr2, is provided by shifting 4 data content (4Lb) fine line direction (see Figure 3 (a)). Each of the reproducing regions 1r ₁ and 1r ₂ of the magnetic thin wire 1 is for reproduction made of a magnetoresistive effect element such as a GMR (Giant MagnetoResistance) element or a TMR (Tunnel MagnetoResistance) element. The magnetic head is opposed to detect the magnetism. Accordingly, the magnetic thin wire 1 is provided with a distance by shifting the reproduction regions 1r ₁ and 1r ₂ in the direction of the fine line, so that the magnetic head is opposed to each of the minute reproduction regions 1r ₁ and 1r ₂ to accurately magnetize. Can be detected. Further, the magnetic wire 1 is limited to the reproduction region 1r (1r ₁ , 1r ₂ ), for example, a structure in which the magnetic domain is locally expanded as described in Patent Document 5, or the like, if necessary. It is good also as a structure corresponding to.

  The magnetic fine wire 1 is preferably laminated with a protective film (not shown) on the upper surface in order to protect the magnetic fine wire 1 from damage during manufacture of the magnetic recording medium 10. The protective film is composed of a single layer of Ta, Ru, Cu, or two layers of Cu / Ta, Cu / Ru, etc., and in the case of a two-layer structure, all have Cu inside (lower layer). Further, the magnetic fine wire 1 may be formed on a base film made of a metal thin film in order to obtain adhesion with the substrate 2 (not shown). A nonmagnetic metal material such as Ta, Ru, Cu, Al, Au, Ag, or Cr can be applied to such a base film. Each of the protective film and the base film is preferably 1 to 10 nm in thickness. If the thickness is less than 1 nm, it is difficult to form a continuous film. On the other hand, if the thickness exceeds 10 nm, the effect is not further improved. Note that this thickness is that of the protective film in the magnetic recording medium 10 (after completion), and the thickness reduction due to the subsequent process is taken into account during manufacture (during film formation).

(substrate)
The substrate 2 is a base of the magnetic recording medium 10 for forming the magnetic wire 1 and is a broad substrate. As such a substrate 2, a known substrate material can be applied. Specifically, a Si (silicon) substrate having a thermal oxide film formed on its surface, SiO ₂ (silicon oxide, glass), MgO (magnesium oxide), Sapphire, GGG (gadolinium gallium garnet), SiC (silicon carbide), Ge (germanium) single crystal substrate, or the like can be applied. If the substrate 2 is a Si substrate and an oxide film having a sufficient thickness is not formed on the surface, an insulating film is formed on the surface and the magnetic wire 1 may be formed. That is, at least the surface (surface layer) of the substrate 2 may be insulative.

(Insulating layer)
The insulating layer 6 is disposed between the magnetic wires 1 and 1 in the magnetic recording medium 10, or between the positive electrodes 31 and 31 and between the negative electrodes 32 and 32, and between the substrate 2 and the magnetic wire 1 or between the magnetic wires 1. It may be arranged on the top. The insulating layer 6 is made of a known insulating material such as SiO ₂ , Si ₃ N ₄ , or Al ₂ O ₃ , and the same material may not be applied to the entire magnetic recording medium 10.

(electrode)
The positive electrode 31 and the negative electrode 32 are terminals for supplying a current to the magnetic wire 1 in one direction as a pair of electrodes, and are connected to both ends of the magnetic wire 1 as shown in FIG. Is done. In the present embodiment, as shown in part (negative electrode 32) in FIG. 2, the electrodes 31 and 32 are both connected to the lower surface of the magnetic wire 1. However, the connection surface of the magnetic wire 1 is not limited to this. It may be connected to the upper surface. The electrodes 31 and 32 are made of a general metal electrode material such as a metal such as Cu, Al, Ta, Cr, W, Ag, Au, or Pt, or an alloy thereof, and is formed by sputtering or the like, or formed by photolithography or the like. Molded into stripes. The thicknesses, widths, and lengths in the thin line direction of the electrodes 31 and 32 are set based on the pitch (track pitch) of the magnetic thin lines 1 and 1, the material, the supplied voltage / current, and the like.

[Method of manufacturing magnetic recording medium]
The magnetic recording medium according to the present invention can be manufactured using a known method. An example of a method for manufacturing the magnetic recording medium 10 shown in FIG. 1 will be described below. An insulating film such as SiO ₂ or Al ₂ O ₃ is formed on the substrate 2 to a thickness of the magnetic wire 1 by a known method such as sputtering, and a resist mask is provided in the region where the magnetic wire 1 is provided. And the insulating film is etched. Next, a magnetic film is formed by a known method such as sputtering, the etched region of the insulating film is filled to form a magnetic thin wire, and the resist mask is removed (lift-off). As a result, flat magnetic wires are formed on the substrate 2, and the insulating layer 6 is formed in the same thickness as the magnetic wires between the magnetic wires.

  On the magnetic wire and the insulating layer 6, a resin film having a groove in the region where the groove 1d is to be formed is formed by nanoimprinting. By performing anisotropic etching by dry etching such as RIE from the top of the resin film, the groove portion of the resin film is removed, and further, the portion of the magnetic wire just below is thinned to form the groove portion 1d. The magnetic wire 1 is used. The remaining resin film is removed, and electrodes 31 and 32 connected to both ends of the magnetic wire 1 are formed with a metal electrode material to obtain the magnetic recording medium 10. By using the nanoimprint method, it is possible to form the fine groove portion 1d with high dimensional accuracy. Alternatively, first, a magnetic film may be formed on the substrate 2, the groove 1 d may be formed, and then processed into a thin wire to form the magnetic thin wire 1, and the insulating layer 6 may be embedded. Alternatively, by forming and etching a resin mask having the shape of the magnetic fine wire 1 on the magnetic film, the fine wire can be processed and the groove 1d can be simultaneously formed.

[Method of operating magnetic recording medium]
(Data writing method)
Next, a method of continuously writing (recording) binary data of “0” and “1” on the magnetic thin wire of the magnetic recording medium according to the present invention will be described with reference to FIGS. FIG. 3 shows only the vicinity of both ends including the writing regions 1w ₁ and 1w ₂ and the reproducing regions 1r ₁ and 1r ₂ of the magnetic thin wire 1, and the intermediate portion is omitted by a broken line. Moreover, although FIG. 3 is a top view, the upper and lower sides of the magnetization direction shown by the arrow shall be in the thickness direction. The data writing method in the magnetic recording medium 10 is a recording / reproducing apparatus in which the recording heads 71 and 72 of the recording / reproducing apparatus write to the write areas 1w ₁ and 1w ₂ to generate magnetic domains and are connected to the electrodes 31 and 32. The pulse current is supplied from the scanning current source 8 (see FIG. 3B) to the magnetic wire 1 to shift the magnetic domain intermittently.

The magnetic thin wire 1 shown in FIG. 2 is in a state where no current is supplied, and the first recording head 71 applies an upward magnetic field to write “0” to the first track Tr1, and “1” to the second track Tr2. The second recording head 72 applies a downward magnetic field to the opposing regions 1w ₁ and 1w ₂ to set the respective magnetization directions. In FIG. 2, the magnetic wire 1 includes a domain wall DW1 extending over the entire width so as to divide in the thin line direction, a domain wall DW2 bent in a hook shape in plan view, and a domain wall DW3 bent in a U shape in plan view in the second track Tr2. And has generated. The magnetic wire 1 shown in FIG. 2 is shown in a plan view in FIG. In FIG. 3, areas where a magnetic field is applied from the recording heads 71 and 72 are indicated by broken line frames in the writing areas 1 w ₁ and 1 w ₂ .

  Here, a sufficiently thin fine wire-like magnetic body is usually generated by dividing a magnetic domain only in the fine line direction, and becomes a single magnetic domain in the fine line width direction. However, the magnetic thin wire 1 of the magnetic recording medium 10 according to the present invention has adjacent portions of the track Tr1, because the portions of the domain wall DW2 and the domain wall DW3 along the boundary between the tracks Tr1, Tr2 are locked to the groove 1d. The state in which magnetic domains having different magnetization directions are generated between Tr2 is maintained.

The magnetic field application to the recording heads 71 and 72 is stopped, and a DC pulse current is supplied to the magnetic wire 1 from the scanning current source 8 connected to the electrodes 31 and 32 as shown in FIG. In the magnetic wire 1, electrons e ⁻ are injected from the negative electrode 32 side (left side), and the domain wall partitioned in the direction of the thin wire moves to the right. At this time, the domain wall having a portion along the fine line direction bent in a plan view like the domain walls DW2 and DW3 is moved to the positive electrode 31 side as the part delimited in the fine line direction moves, that is, the fine line. Move in the direction. Here, the portions along the thin line direction of the domain walls DW2 and DW3 are locked by the groove 1d, and the respective shapes of the magnetic domains having different magnetization directions are held across this portion. All the magnetic domains thus moved move equidistant to the right while maintaining their respective shapes. Note that the outermost magnetic domain on the negative electrode 32 side is extended by the movement distance due to the injected electrons e ⁻ .

  The magnetic thin wire 1 having a uniform shape in the direction of the thin wire moves the domain wall at a constant speed by supplying a constant current, and the moving speed depends on the current density. Accordingly, the tracks Tr1 and Tr2 in the same magnetic wire 1 have the same current density of the current supplied to the magnetic wire 1 even if the width (cross-sectional area) is non-uniform, so that the domain wall moves by the same distance. To do. By setting the pulse width of the direct current pulse current so that the movement distance of one time becomes the bit length Lb, the magnetic domain is shifted and shifted intermittently in increments of the bit length Lb while the scanning current source 8 is kept in the ON state. Can be made.

When stopping after supplying one pulse of the DC pulse current shown in FIG. 3B, writing is again performed on the writing areas 1w ₁ and 1w _{2 by the} recording heads 71 and 72 as shown in FIG. 3C. . Here, “1” is written in the writing area 1 w ₁ of the first track Tr ₁ to make the magnetization direction downward, and “0” is written in the writing area 1 w ₂ of the second track Tr 2 to make the magnetization direction upward. As a result, the second track Tr2, on the right side of the write region 1 w _2, the length of the bit length Lb, magnetization downward magnetic domains are formed. Further, in the first track Tr1, the right of the write region 1 w _1, the magnetization of the double thin lines length of the bit length Lb upward magnetic domain is generated. As described above, the magnetic recording medium 10 supplies the pulse current to the magnetic wire 1 and moves the domain wall by the distance of the bit length Lb to write the next data. Since the length can be stored in the magnetic wire 1 with the bit length Lb, the recording density can be increased.

In FIG. 3C, the magnetic field application region (inside the broken line in the drawing) of the writing region 1w ₂ of the second track Tr2 is shifted to the first track Tr1, but after the magnetic field application is stopped, Since the domain wall moves minutely so as to be locked to the groove 1d, data is recorded only on the second track Tr2. As described above, by dividing the magnetic wire 1 by the groove 1d, data can be accurately recorded on each of the tracks Tr1 and Tr2. In other words, in the magnetic thin wire in which the groove portion 1d is not formed, a magnetic domain having a magnetization direction different from that of the other can be temporarily generated in one track by applying a magnetic field or the like. When the magnetic domains are shifted, a single magnetic domain is formed in the thin line width direction, so that it is difficult to individually record data on each track. Incidentally, the magnetic field applied to the write area 1 w ₂ of the second track Tr2 may extend to the first track Tr1. This is because the first track Tr1 is rewritten in the write area 1w ₁ in front of the write area 1w ₂ .

(Data playback method)
Data stored as magnetic domains in the tracks Tr1 and Tr2 of the magnetic thin wire 1 is supplied to the reproduction regions 1r ₁ and 1r ₂ by supplying a direct current pulse current in the same manner as writing, thereby reproducing the regions 1r ₁ and 1r. _The data can be reproduced by a reproducing magnetic head of the recording / reproducing apparatus facing ₂ . For example, in FIG. 3A, since the downward magnetic domain reaches the reproduction area 1r ₁ in the first track Tr1, the data “1” is reproduced, and the upward magnetic domain exists in the reproduction area 1r ₂ in the second track Tr2. Since it has reached, data “0” is reproduced. In FIG. 3C after supplying one pulse of the DC pulse current (see FIG. 3B), data “0” is reproduced on the first track Tr1, and data “1” is reproduced on the second track Tr2. Is done. In the magnetic wire 1, the magnetic domain that has reached the end on the positive electrode 31 side by current supply disappears. Therefore, the data recorded in the magnetic recording medium 10 may be saved by writing the data reproduced in the reproduction areas 1r ₁ and 1r ₂ from the top in parallel by the recording heads 71 and 72 (for example, Patent Documents). 3).

As described above, in the magnetic recording medium 10 according to the present embodiment, two conventional magnetic wires constituting one track are connected to form an integrated magnetic wire 1 and are parallel with a common current. It can be said that it operates. In the present embodiment, the write areas 1w ₁ and 1w ₂ of the magnetic wire 1 and the reproduction areas 1r ₁ and 1r ₂ are both shifted by 4 Lb, so that the top data of each of the tracks Tr1 and Tr2 is used. You can write at the same time. On the other hand, when the deviations of the write areas 1w ₁ and 1w ₂ and the reproduction areas 1r ₁ and 1r ₂ are different from each other, the head data of the tracks Tr1 and Tr2 is written in accordance with the deviation of the reproduction areas 1r ₁ and 1r _2. Shift the timing. For example, when the write areas 1w ₁ and 1w ₂ are shifted by 4Lb and the reproduction areas 1r ₁ and 1r ₂ are shifted by 8Lb, 4 data are written only in the first track Tr1, and then the fifth data and the second track Tr2 are written. Simultaneously write the first data. As described above, the magnetic recording medium 10 according to the present invention cannot perform domain wall movement individually on the tracks Tr1 and Tr2 provided on the same magnetic wire 1, and thus performs parallel (simultaneous) reproduction and simultaneous writing. Note that when the direct current pulse current is stopped once, writing and reproduction may be sequentially performed without simultaneously performing the tracks Tr1 and Tr2. For example, in writing, by not applying a magnetic field from both the recording heads 71 and 72 simultaneously, it is possible to avoid the applied magnetic fields from affecting each other.

As for the writing method, in addition to the magnetic field application by the recording heads 71 and 72, spin injection magnetization reversal may be applied. By forming the spin-injection magnetization reversal element structure in the write regions 1w ₁ and 1w ₂ of the magnetic wire 1, these regions can be brought into a desired magnetization direction by spin-injection magnetization reversal. Specifically, an intermediate layer and a magnetization fixed layer are laminated so that the magnetic wire 1 becomes a magnetization free layer in the write regions 1w ₁ and 1w ₂ , and current is supplied to the spin-injection magnetization switching element structure in the direction perpendicular to the film surface. A pair of electrodes for flowing is connected vertically (not shown). The magnetic wire 1 preferably has a thickness of 5 to 30 nm so that magnetization can be suitably reversed as a magnetization free layer. By adopting such a configuration, even if the writing areas 1w ₁ and 1w ₂ are miniaturized, it is easy to write at an accurate position, and writing can be performed at a speed higher than the magnetic field application. Since the two spin-injection magnetization reversal element structures in the write regions 1w ₁ and 1w ₂ share the magnetization free layer with the magnetic fine wire 1, at least when writing different data, write (current supply) is performed. Do not perform at the same time.

(Modification)
In the first embodiment, the magnetic thin wire 1 has a groove 1d formed on the upper surface so that the magnetic wall is locked in the thin wire width direction. However, the track delimiter for dividing the magnetic thin wire into the tracks Tr1 and Tr2 Not limited to. In a magnetic recording medium 10A according to a modification of the first embodiment shown in FIG. 4A, a magnetic fine wire 1A is formed on a substrate 2A having a groove formed on the surface. Since the magnetic film for forming the magnetic wire 1A has a uniform film thickness, the magnetic wire 1A has a groove-like shape in which the upper surface is recessed directly above the groove of the substrate 2A along the surface shape of the substrate 2A. A groove (continuous recording area delimiter) 1f is formed. The magnetic wire 1A has a hook shape in which the lower surface of the groove 1f projects downward. The shape of the magnetic wire 1A is different from that of the magnetic wire 1 whose cross-sectional area is locally reduced by the groove 1d. However, the magnetic wall is also easily locked in the locally deformed groove 1f, which is the same as the groove 1d. The effect as a track delimiter can be obtained. The amount of change in the shape of the deforming portion 1f and the length in the thin line direction are the same as those of the groove portion 1d. Note that the amount of change of the groove portion 1f may be 2% or more of the thickness of the magnetic wire 1A on either the upper surface or the lower surface, and the shape of the groove formed on the surface of the substrate 2A may be controlled. Further, a ridge may be formed on the surface of the substrate 2A in place of the groove, and the magnetic fine wire 1A (magnetic film) may be formed thereon. In this case, the magnetic fine wire 1A has a shape in which the unevenness is inverted.

  As described above, according to the magnetic recording medium according to the first embodiment and the modification thereof, the recording density can be doubled while keeping the width and pitch of the magnetic fine wires as is.

[Second Embodiment]
In the first embodiment and the modification thereof, the shape of the magnetic wire is deformed to form a track boundary (track delimiter). However, the action of locking the domain wall in the magnetic material has magnetic characteristics in addition to the shape. Also have locally altered sites. Hereinafter, a magnetic recording medium according to the second embodiment of the present invention will be described with reference to FIG. The same elements as those in the first embodiment (see FIGS. 1 to 3) are denoted by the same reference numerals, and description thereof is omitted.

  As shown in FIG. 4B, in the magnetic recording medium 10B according to the second embodiment, magnetic thin wires 1B having flat upper and lower surfaces are formed on the substrate 2. The magnetic thin wire 1B is provided with a high Ms region (continuous recording region dividing portion) 1s having a saturation magnetization higher than that of the other regions along the thin line direction so as to be divided in the thin line width direction. The track is divided into a track Tr1 and a second track Tr2.

  In the region where the saturation magnetization has a high and low gradient, the domain wall moves toward the higher saturation magnetization. In the magnetic fine wire 1B, in the high Ms region 1s, since the saturation magnetization forms a gradient of low to high to low in the thin wire width direction, a magnetic domain is generated in each of the tracks Tr1 and Tr2 as in the first embodiment. Retained.

  The width (length in the thin line width direction) of the high Ms region 1s is the same as that of the groove portions 1d and 1f. In addition, in the magnetic thin wire 1B, the high Ms region 1s including the region where the saturation magnetization gradually increases with respect to another region where the saturation magnetization is uniform is set. The saturation magnetization of the high Ms region 1s is not particularly limited, but it should be 1.2 times or more at the highest portion with respect to the region outside the high Ms region 1s so that the domain wall is suitably locked. Is preferred. On the other hand, the saturation magnetization of the high Ms region 1s is preferably about 10 times or less so that the saturation magnetization of the region outside the high Ms region 1s, that is, the tracks Tr1 and Tr2 does not become too low. Such a change in saturation magnetization is obtained by irradiating the magnetic thin wire (or magnetic film before processing) with ions, and the saturation magnetization decreases as the irradiation amount increases. Therefore, similarly to the formation of the groove 1d in the magnetic wire 1 of the magnetic recording medium 10 according to the first embodiment, a resist mask or a resin mask by nanoimprinting may be formed and irradiated with ions. Note that the mask forms a thick region for forming the high Ms region 1s. For the ion irradiation, for example, an ion implantation apparatus applied to the manufacture of a semiconductor device can be used. Also, the amount of change (decrease) in saturation magnetization varies depending on the ion species and implantation conditions. Examples of the ion species include Ga, N, O, Ar, Kr, and Xe.

(Modification)
In the magnetic thin wire 1B, the track delimiter is a region having a relatively high saturation magnetization (high Ms region 1s), but the same effect can be obtained even in a region having a low saturation magnetization. In this case, it is preferable that the portion having the lowest saturation magnetization is 1 / 1.2 times or less the outside of the region (track delimiter). Alternatively, the saturation magnetization may be further reduced, and the track delimiter may be a nonmagnetic material. Since the saturation magnetization is reduced by the ion irradiation, the magnetic thin wire 1B can store and reproduce data as a ferromagnetic material without irradiating the main recording area other than the track delimiter (magnetic field). Detection) and the like.

[Third Embodiment]
The magnetic recording medium according to the present invention has a shape and saturation magnetization at the boundary demarcated in the direction of the thin line, similarly to the conventional magnetic thin line (see, for example, Patent Documents 2 and 4) in which one magnetic thin line constitutes one track. By providing a region in which is changed, it is possible to prevent displacement in the domain wall movement (magnetic domain shift movement) in the thin line direction. Hereinafter, a magnetic recording medium according to a third embodiment of the present invention will be described with reference to FIG. The same elements as those in the first and second embodiments (see FIGS. 1 to 4) are denoted by the same reference numerals, and the description thereof is omitted.

  As shown in FIG. 5A, a magnetic recording medium 10C according to the third embodiment is formed on a substrate 2 with a magnetic wire 1 (see FIG. 1B) of the magnetic recording medium 10 according to the first embodiment. Similarly, a magnetic fine wire 1C is provided in which one groove 1d that is divided into two in the fine wire width direction is formed on the upper surface. The magnetic thin wire 1C is further divided in the thin wire direction (circumferential direction of the outer shape of the magnetic recording medium 10C), and groove-like recesses (deformed portions) 1c extending over the entire width of the magnetic thin wire 1C are spaced at a constant interval (pitch). Here, they are formed on the upper surface at a pitch of the bit length Lb. That is, the magnetic thin wire 1C has a groove 1d and a plurality of recesses 1c perpendicular to the groove 1d formed on the upper surface.

  In the magnetic thin wire 1C, the portion of the magnetic thin wire 1C that is deformed by being divided in the thin wire direction like the concave portion 1c has a groove width (length in the thin wire direction in the opening portion of the concave portion 1c), similar to the groove portion 1d. It is preferable that the thickness is not less than 10 times. Specifically, the groove width of the recess 1c is in the range of about 10 to 100 nm, less than 1/2 of the bit length Lb, and 1/10 of the width of the tracks Tr1 and Tr2 (1/2 of the width of the magnetic wire 1C). About 2 times is preferable. Further, in order to keep the domain wall suitably locked when the pulse current to the magnetic wire 1C is stopped (base period), the amount of change in the deformed portion such as the recess 1c is the same as the groove 1d. It is preferable to set it to 2% or more. On the other hand, unlike the track delimiter such as the groove 1d, the recess 1c needs to move the locked domain wall to the outside of the recess 1c again. If the amount of change is too large, the current density is increased due to this movement. Further, as in this embodiment, when the cross-sectional area is reduced as the recess 1c, if the cross-sectional area is reduced, the resistance when supplying the pulse current to the magnetic wire 1C increases. Therefore, in the magnetic thin wire 1C, it is preferable that the amount of change in the deformed portion such as the recess 1c is 40% or less (the cross-sectional area is 60% or more outside the recess 1c). Further, the concave portion 1c has a small action of locking the domain wall if the inclination is too gentle, and lacks stability of operation. On the other hand, if it is too steep, a high current density is required to move the locked domain wall again. The groove width and the like are also designed so that the movement is suitably performed.

  Further, in the magnetic thin wire 1C, the deformed portion such as the concave portion 1c temporarily locks the domain wall (when the pulse current is stopped) in the shift movement of the magnetic domain. It is preferably smaller than the groove 1d. That is, in the magnetic thin wire 1C, the recess 1c is preferably shallower than the groove 1d, and the inclination is preferably the same as or slower than the groove 1d. Hereinafter, a portion that is provided at a boundary that divides the magnetic fine wire in the thin wire direction and temporarily locks the magnetic domain wall in the shift movement of the magnetic domain, such as the concave portion 1c of the magnetic fine wire 1C, is appropriately referred to as a domain wall locking portion.

  In FIG. 5A, the magnetic recording medium 10C is a straight line along the radial direction of the outer shape of the magnetic recording medium 10C across two or more adjacent magnetic thin wires 1C (two in FIG. 5A). A recess 1c is provided in the shape. In the disk-shaped magnetic recording medium 10C, the lengths of the magnetic thin wires 1C are different between the outer peripheral side and the inner peripheral side of the magnetic recording medium 10C, and even between the tracks Tr1 and Tr2 in one magnetic thin wire 1C. Strictly speaking, the length is different. However, since the difference between the adjacent fine magnetic wires 1C up to a certain number is very small, by providing the concave portions 1c on a straight line along the diameter in such a number, the concave portions of the respective magnetic thin wires 1C are provided. The domain wall is locked at 1c. Since there is no displacement of the magnetic domains, as shown in FIG. 1A, the write area 1w and the reproduction area 1r are provided in all the magnetic wires 1C along the diameter in plan view of the magnetic recording medium 10C. Can do. Therefore, in the magnetic recording medium 10C, the concave portions 1c, 1c,... Are provided radially across the plurality of adjacent magnetic thin wires 1C in a plan view. When the magnetic recording medium is rectangular in plan view and the magnetic thin wires are formed in straight lines parallel to each other, the recess 1c may be provided along a straight line perpendicular to the thin line direction (not shown).

  In FIG. 5A, the magnetic thin wire 1C is provided with a recess 1c for each bit length Lb, that is, to divide one data storage area. However, the present invention is not limited to this, and an integer of 2 or more of the bit length Lb is provided. You may provide the recessed part 1c for every double. Or you may provide the recessed part 1c only in the specific site | part in the magnetic fine wire 1C, such as the vicinity of the writing area | region 1w and the reproduction | regeneration area | region 1r.

  The cross-sectional shape (cross section perpendicular to the thin line width direction) of the recess 1c is not particularly defined, and examples thereof include a V shape (inverted triangle), a U shape, a rectangle, and an inverted trapezoid shape. Furthermore, as long as the recess 1c is formed in each of the tracks Tr1 and Tr2, it may not be formed over the entire width of the magnetic wire 1C. For example, a plane formed at the center in the width direction of each of the tracks Tr1 and Tr2. It may be a dent (such as a cone) in view (not shown). That is, in the tracks Tr1 and Tr2, if a part of the region through which the domain wall passes is also deformed, the domain wall can be locked. However, the concave portion 1c is preferably formed with high dimensional accuracy so that the shape of the concave portion 1c is substantially the same in the magnetic recording medium 10C in order to equalize the action of locking the domain wall. Such a recess 1c can be formed by etching the magnetic wire 1C (magnetic film) in the same manner as the groove 1d. For example, in FIG. 5A, after forming the magnetic wires 1C and 1C into a thin wire shape and further forming the insulating layer 6 therebetween, the diameter of the magnetic recording medium 10C is formed on the magnetic wires 1C and 1C and the insulating layer 6. A rectilinear groove is formed to form a recess 1c. The groove 1f may be formed in the magnetic wire 1C simultaneously with the recess 1c, or may be formed separately in another process. Moreover, if the recessed part 1c is a dotted | punctate dent, it can also be formed by pushing and protruding a projection-like tool into the upper surface of the magnetic wire 1C (magnetic film).

(Modification)
In the third embodiment, the magnetic thin wire 1C is formed with the concave portion 1c on the upper surface to form the domain wall locking portion. However, like the track partitioning portion such as the groove 1d, the magnetic fine wire 1C is not limited thereto. A magnetic recording medium 10D according to a modification of the third embodiment shown in FIG. 5B has a magnetic thin wire 1D formed on a substrate 2B on the surface of which a groove is formed along the radial direction of the magnetic recording medium 10D. The magnetic fine wire 1D is formed with a concave portion (deformed portion) 1b along the surface shape of the substrate 2B. That is, the recess 1b is formed by the same method as the groove 1f of the magnetic wire 1A of the magnetic recording medium 10A according to the modification of the first embodiment shown in FIG. In the magnetic wire 1D, a groove 1d is formed on the upper surface as a track delimiter. That is, in the magnetic recording medium 10D, only the grooves along the radial direction for forming the recesses 1b are formed on the surface of the substrate 2B, and after forming the magnetic wire 1D (magnetic film) thereon, the magnetic wire 1D is formed. A groove 1d is formed on the surface. The position of the recess 1b in the magnetic wire 1D, the amount of change in shape, and the like are the same as those of the recess 1c.

  Note that a groove 1f may be provided as a track delimiter instead of the groove 1d. In this case, grooves along the fine line direction (circumferential direction of the outer shape) and the radial direction are formed on the substrate 2B, The magnetic wire 1D (magnetic film) may be formed on the substrate. Or you may combine the groove part 1f and the recessed part 1c (illustration omitted).

Further, as described above, in the tracks Tr1 and Tr2, it is only necessary to deform even a part of the region through which the domain wall passes, so that the side surface of the magnetic wire 1E is locally recessed as shown in FIG. May be. A magnetic recording medium 10E according to a modification of the third embodiment is provided with magnetic thin wires 1E that are constricted on both sides in plan view. Such constricted portions (deformed portions) 1k ₁ and 1k ₂ of the magnetic wire 1E are, like the recesses 1c and 1b, the ratio of the amount of change with respect to the entire magnetic wire 1E, that is, the widths of the tracks Tr1 and Tr2 (magnetic wires 1). It is preferable that the confinement depth (maximum notch length in the width direction of the thin wire) with respect to ½ of the width of the width is 2% or more and 40% or less. In such a magnetic recording medium 10E, for example, a magnetic film is formed on a substrate 2A having a groove formed on the surface, and processed into a thin line shape having constricted portions 1k ₁ and 1k ₂ using a mask, thereby forming the magnetic thin line 1E. Is obtained. In the magnetic wire 1E, the groove 1f is provided as a track delimiter, but the groove 1d may be applied (not shown).

  In the magnetic recording medium according to the present embodiment, as a domain wall locking portion, a region in which the saturation magnetization height is locally changed (saturation magnetization variation portion) may be provided at the boundary demarcated in the thin line direction (not shown). ). When the saturation magnetization in such a domain wall locking portion is increased, as in the high Ms region 1s of the magnetic wire 1B of the magnetic recording medium 10B (see FIG. 4B) according to the second embodiment, the domain wall is increased. In the case of lowering 1.2 times or more and 10 times or less with respect to the outside of the engaging portion, it is preferable to set 1/10 times or more and 1 / 1.2 times or less. Furthermore, when a region where saturation magnetization is changed, such as the high Ms region 1s, is used as the track partitioning portion, the domain wall locking portion has a high height in order to make the action of locking the domain wall smaller than the track partitioning portion. The amount of change is preferably smaller than the amount of change in the Ms region 1s, that is, a saturation magnetization region having three levels of height is provided in the entire magnetic wire. Further, in the magnetic thin wire, when the track delimiter is a high Ms region 1s having a high saturation magnetization, the domain wall locking portion may be a region having a lower saturation magnetization than the other regions, or vice versa.

In the magnetic thin wire in which the domain wall engaging portion is provided with a region in which the saturation magnetization height is changed, the groove portion 1d or the groove portion 1f may be combined as a track partitioning portion. Alternatively, any _{one of} the concave portion 1c, the concave portion 1b, and the constricted portions 1k ₁ and 1k ₂ as magnetic domain wall engaging portions is provided on a magnetic thin wire provided with a region in which the saturation magnetization height is changed as the high Ms region 1s as the track delimiter portion. You may form. As described above, when combining the change in shape and the change in saturation magnetization, the shape and the like of the depth of the groove and the like so that the action of locking the domain wall is smaller in the domain wall locking part than in the track partitioning part. It is preferable to set the amount of change in saturation magnetization.

Example 1
In order to confirm the effect of the present invention, a sample simulating the magnetic thin wire (see FIGS. 1 and 2) of the magnetic recording medium according to the first embodiment was produced, and the formed magnetic domains were observed. On the Si substrate whose surface was thermally oxidized, a multilayer film of Ru (3 nm) and [Co (0.3 nm) / Pd (1.2 nm)] × 21 was formed as a base (total thickness about 40 nm), It was processed into a magnetic thin wire having a width of about 250 nm. By inserting a diamond probe used for the nanoindentation function of the atomic force microscope (AFM) into this magnetic wire and sliding it in the direction of the thin wire (scratch), the depth along the direction of the thin wire is about the center in the width direction. A sample was prepared by forming one groove of about 14 nm. FIG. 6A shows a surface shape and an AFM image photograph of the sample observed with the AFM. Since the magnetic thin wire of the produced sample was deformed by pushing a diamond probe into the upper surface and deformed, both sides of the groove were raised as shown in FIG.

  As a initialization, a magnetic field of 1 kG is applied upward to the prepared sample to saturate the entire magnetization to make it upward, and then 0.5 kG, which is slightly smaller than the coercive force of the magnetic wire (Co / Pd multilayer film). A downward magnetic field was applied to generate a plurality of magnetic domains. The surface of this sample was imaged and observed with a magnetic force microscope (MFM). In the MFM image photograph shown in FIG. 6B, the magnetic thin line shows white (upward) / black (downward) contrast for each magnetic domain depending on whether the magnetization direction is upward or downward.

  As shown in FIGS. 6 (a) and 6 (b), it is confirmed that the magnetic fine wires are divided not only in the fine wire direction but also in the fine wire width direction along the groove, thereby forming two tracks. I can say that.

(Example 2)
The same Co / Pd multilayer film as in Example 1 was processed into a magnetic thin wire having a width of about 300 nm, and two of this magnetic thin wire having a depth of 15 to 20 nm along the thin wire direction so as to be divided into approximately three equal parts in the width direction. A groove was formed in the same manner as in Example 1 to prepare a sample. FIG. 7A shows a surface shape and an AFM image photograph of the sample observed with the AFM. Further, as in Example 1, a plurality of magnetic domains were generated on the magnetic wire by applying a two-step magnetic field. An MFM image photograph of the surface of this sample is shown in FIG.

  As shown in FIGS. 7A and 7B, even when two grooves are formed in the magnetic thin wire, it is confirmed that the magnetic domains are divided along the respective grooves in the thin wire width direction. It can be said that an arbitrary number of tracks equal to or more than one can be configured.

  From the above results, even if the magnetic thin wire is narrow enough to generate a single magnetic domain in the width direction, it is possible to provide 2 portions per one by providing a portion for locking a magnetic wall such as a groove along the thin wire direction. The recording density can be increased by providing the recording area to be the above track.

  As mentioned above, although the form for implementing the magnetic recording medium based on this invention has been described, this invention is not limited to these embodiment, A various change is possible in the range shown to the claim. .

10, 10A, 10B, 10C, 10D, 10E Magnetic recording medium 1, 1A, 1B, 1C, 1D, 1E Magnetic wire 1d Groove (continuous recording area delimiter)
1f Groove (continuous recording area delimiter)
1s High Ms area (continuous recording area delimiter)
1b Concave part (deformed part)
1c Concave part (deformation part)
1k ₁ , 1k ₂ constricted part (deformed part)
2, 2A, 2B Substrate 31 Positive electrode 32 Negative electrode 6 Insulating layer

Claims (4)

A magnetic recording medium comprising one or more magnetic wires formed by forming a magnetic material on a substrate in a thin line shape, wherein binary data is recorded on the magnetic wires as different magnetization directions and magnetic domains are generated. ,
The magnetic fine wire is provided with a continuous recording area delimiter formed in either a groove shape or a bowl shape in which at least one of the upper surface and the lower surface extends in the fine line direction at one or more positions of the boundary demarcated in the thin line width direction,
The magnetic fine lines are generated by continuously generating a plurality of the magnetic domains in the thin line direction in each of the areas divided in the fine line width direction with the continuous recording area delimiter as a boundary. 2. A magnetic recording medium according to claim 1, wherein in the divided area, a domain wall separating the magnetic domains moves in a thin line direction. A magnetic recording medium comprising one or more magnetic wires formed by forming a magnetic material on a substrate in a thin line shape, wherein binary data is recorded on the magnetic wires as different magnetization directions and magnetic domains are generated. ,
The magnetic thin wire has a continuous recording region delimiter extending in the direction of the thin line at one or more boundaries demarcated in the thin line width direction and having different saturation magnetization heights from other regions,
The magnetic fine lines are generated by continuously generating a plurality of the magnetic domains in the thin line direction in each of the areas divided in the fine line width direction with the continuous recording area delimiter as a boundary. 2. A magnetic recording medium according to claim 1, wherein in the divided area, a domain wall separating the magnetic domains moves in a thin line direction.   The magnetic fine wire is provided with a deforming portion that locks the magnetic domain wall when the current is stopped, at one or more of the boundaries demarcated in the fine wire direction, the shape of the cross section perpendicular to the fine wire direction is different from other regions. The magnetic recording medium according to claim 1, wherein the magnetic recording medium is a magnetic recording medium.   The magnetic thin wire is provided with a saturation magnetization variation portion that locks the domain wall when the current is stopped at one or more of the boundaries demarcated in the thin wire direction, unlike the other regions. The magnetic recording medium according to claim 1, wherein: