JP2000306204A - Reproducing method and magnetically recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain reproduced signal quality in which the SN ratio is high and crosstalk is small by approaching close to and performing relative movement to a magnetic recording medium and setting, along the moving direction, a magnetic flux detection area where the magnetic domain pattern of a reproduction having a length equal to or greater than the shortest record wavelength of the magnetic domains of a pair of memory layers adjacent to each other and directed oppositely to the magnetic recording medium. SOLUTION: A record magnetic domain surrounded by a pair of the arcs of a magnetic domain wall moving type recording media consists of upward magnetic domains denoted by a white circle symbol with a black point inside and downward magnetic domains denoted by a white circle symbol with a cross mark inside. A curve group 9 is an isotherm group and as an isotherm is located close to the left, it represents a higher temperature. A magnetic field detection area 8 is an area where a magnetic head can detect a magnetic field with high sensitivity, and the length of the area 8 is almost equal to the thickness Lt of a main magnetic pole. Here, the thickness Lt of the main magnetic pole is made wider than the shortest record wavelength λ occupied by a pair of record magnetic domains adjacent to each other and directed oppositely. Thus, it is possible to perform low noise magnetic domain wall moving type reproduction and to prevent the reduction of the SN ratio of a reproduced signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a reproducing means used for an information storage device. More specifically, in reproducing information recorded as a magnetic domain pattern on the magnetic layer, the recorded magnetic domain pattern is enlarged or reduced by locally heating the magnetic layer, and the change in the magnetic field leaking from the magnetic layer at that time is reduced. It relates to a reproducing means for detecting.

[0002]

2. Description of the Related Art In the field of magnetic recording, efforts are constantly being made to increase the recording density in order to meet the demand for increased storage capacity of information storage systems. However, the higher the recording density, the smaller the magnetic domain size, which is the recording unit,
Inevitably, the output of the reproduced signal is reduced, making data detection difficult.

As a means for solving this problem, a magnetic recording medium having at least two magnetic layers, that is, a memory layer in which information is recorded and held, and a reproducing layer (hereinafter referred to as a "magnetic domain fluctuation recording medium during reproduction") has been proposed. I have. When the magnetic domain change recording medium during reproduction is heated during reproduction, the recording magnetic domain of the memory layer is magnetically transferred to the reproduction layer, and the magnetic domain magnetically transferred to the reproduction layer is enlarged, reduced, or disappears. Based on these operations, a magnetic domain pattern is detected from the magnetic domain variation recording medium during reproduction, and the recorded information is reproduced.

For example, JP-A-1-14301 and JP-A-1-14302 disclose a reproducing method in which a magnetic domain is read while being enlarged or reduced.
Japanese Patent Application Laid-Open Publication No. Hei 11 (1995) discloses a method of transferring a recording magnetic domain of a memory layer to a reproducing layer and reading out the same during reproduction. Further, a reproducing method for detecting the movement of the domain wall is disclosed in Japanese Patent Application Laid-Open No. Hei 10-91938, and a reproducing magnetic domain variation recording medium and reproducing apparatus having high reproducing signal quality even in high-density recording have been proposed.

The magnetic domain fluctuation recording medium for reproduction disclosed in Japanese Patent Application Laid-Open No. 10-91938 has a switching layer and a reproduction layer laminated in this order on a memory layer for recording information. Is performed by a recording magnetic head. Further, the reproducing apparatus has a heating means such as an optical head and a reproducing magnetic head, and these are arranged on opposite sides with respect to the magnetic domain variation recording medium during reproduction. The heating means is precisely arranged so as to locally heat the position where the reproducing magnetic head hits the magnetic domain variation recording medium during reproduction.

[0006]

However, it has been found that the following problems exist when a reproducing operation is performed using the above-described magnetic recording medium and reproducing apparatus.

First, the reproducing magnetic head detects not only the magnetic flux leaking from the reproducing layer but also the magnetic flux leaking from the memory layer. Since the latter leakage magnetic flux becomes noise with respect to the former leakage magnetic flux, there is a first problem that the SN ratio of the reproduced signal is reduced.

Further, due to the non-uniformity of the recording magnetic field and the microscopic non-uniformity of the physical shape and magnetic properties of the magnetic layer, the domain wall of the recording magnetic domain becomes microscopically curved or zigzag. The unevenness of the domain wall becomes noise when detecting domain wall movement and enlargement / reduction (or further disappearance) of the magnetic domain. Therefore, there is a second problem that the SN ratio of the reproduced signal is reduced.

In the case where a plurality of recorded tracks are adjacent to each other, when reproducing one of the tracks, crosstalk from an adjacent recorded track occurs to deteriorate the quality of a reproduced signal. There was a third problem of doing so.

[0010] Further, not only the magnetic layer but also the temperature of the soft magnetic member, the magnetic shield member, the magnetic flux detecting element and the like constituting the magnetic circuit of the reproducing magnetic head are increased by the heating during reproduction. Therefore, there is a fourth problem that these characteristics are deteriorated and the reliability is lowered. The fourth problem will be remarkable when the heating means and the magnetic head are integrated on the same side with respect to the magnetic recording medium for compactness.

SUMMARY OF THE INVENTION The present invention has been made to solve such problems of the prior art, and an object of the present invention is to provide a reproducing means having a high S / N ratio and low crosstalk from an adjacent track and excellent reproduction signal quality. I do. It is another object of the present invention to obtain a highly reliable reproducing means in which the components of the magnetic head are less deteriorated.

[0012]

Means for Solving the Problems Claim 1 of the present invention
The present invention relates to reproducing means for performing relative movement close to a magnetic recording medium and setting a magnetic flux detection area with respect to the magnetic recording medium. Here, the magnetic recording medium has a memory layer holding a magnetic domain pattern, and the magnetic domain pattern of the memory layer is transferred at a temperature higher than a predetermined temperature, or the predetermined magnetic layer pattern is formed based on the magnetic domain pattern of the memory layer. A reproducing layer having at least one function of expanding, reducing, or eliminating a magnetic domain pattern generated at a temperature lower than the temperature at a temperature higher than the predetermined temperature. Then, the magnetic flux detection area detects the magnetic domain pattern of the reproducing layer, and a minimum length occupied by the magnetic domains of the pair of memory layers adjacent to each other in the direction opposite to each other along the direction of movement along the direction of movement. It extends beyond the shortest recording wavelength that is a value.

[0013] The invention according to claim 2 is as follows.
2. The reproducing means according to claim 1, further comprising a single-pole head having a thickness along the moving direction that is equal to or longer than the shortest recording wavelength.

According to a third aspect of the present invention,
3. The reproducing means according to claim 2, further comprising a magnetic body disposed on a side of the single pole head in a medium moving direction in which the magnetic recording medium moves relatively to the reproducing means.

According to a fourth aspect of the present invention,
2. The reproducing means according to claim 1, wherein: a magnetic flux sensitive element for setting the magnetic flux sensing area; and a magnetic shield disposed apart from the magnetic flux sensitive element on the opposite side to the medium moving direction by the minimum recording wavelength or more. And

According to a fifth aspect of the present invention,
2. The reproducing means according to claim 1, further comprising a ring head having a gap whose length along the moving direction is equal to or longer than the shortest recording wavelength.

According to a sixth aspect of the present invention, there is provided:
2. The reproducing means according to claim 1, wherein the magnetic flux sensitive element and a holding base for holding the magnetic flux sensitive element from a side opposite to a medium moving direction in which the magnetic recording medium moves relative to the magnetic flux sensitive element. And a table.

According to a seventh aspect of the present invention,
7. The reproducing means according to claim 1, wherein the magnetic flux detection area is a length occupied by magnetic domains of a pair of memory layers adjacent to each other in opposite directions along the direction of movement. Extend beyond the maximum value.

According to the eighth aspect of the present invention,
This is a magnetic recording method in which the magnetic recording medium is moved relatively close to the magnetic recording medium, and reproduction is performed by reproducing means for setting a magnetic flux detection area with respect to the magnetic recording medium. Here, the magnetic recording medium has a memory layer holding a recorded magnetic domain pattern, and the recorded magnetic domain pattern is transferred at a temperature higher than a predetermined temperature, or the predetermined magnetic domain pattern is transferred based on the recorded magnetic domain pattern. A reproducing layer having at least one function of expanding, reducing, or eliminating a magnetic domain pattern generated at a temperature lower than the temperature at a temperature higher than the predetermined temperature. Then, a magnetic flux detection region extending at a predetermined length along the direction of the movement and detecting the magnetic domain pattern of the reproducing layer is set for the magnetic recording medium. In addition, the minimum value of the length of the pair of magnetic domains adjacent to each other in opposite directions in the recorded magnetic domain pattern along the moving direction is set to be equal to or less than the predetermined length and recorded.

According to a ninth aspect of the present invention, there is provided:
9. The magnetic recording method according to claim 8, wherein the maximum length of the pair of adjacent magnetic domains in the recorded magnetic domain pattern along the direction of movement of the pair of adjacent magnetic domains is the predetermined length. It is set and recorded as follows.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A Background of the Invention. Before describing embodiments of the present invention in detail, a magnetic domain fluctuation recording medium during reproduction to which the present invention is applied will be described by taking a domain wall displacement type as an example.

FIG. 1 is a schematic cross-sectional view of a domain wall displacement type recording medium 50. A first magnetic layer 5 serving as a memory layer is provided on a substrate 51.
2, a second magnetic layer 53, and a third magnetic layer 54, which is a reproducing layer, are stacked upward in this order. The information to be recorded includes a magnetic domain of the first magnetic layer 52, which is magnetized vertically upward to the domain wall displacement recording medium 50 (a magnetic domain indicated by an upward arrow in the figure: hereinafter, referred to as an "upward magnetic domain"). It is held by the position of the domain wall between magnetic domains that are vertically magnetized downward (indicated by a downward arrow in the figure: hereinafter referred to as “downward magnetic domains”).

The Curie temperature Tc2 of the second magnetic layer 53 is set to be higher than room temperature (for example, a temperature at which the magnetic domain fluctuation recording medium is stored without performing recording or reproduction during reproduction). Then, the first magnetic layer 5 that determines the domain wall that carries information
The magnetization of No. 2 reaches the third magnetic layer 54 via the second magnetic layer 53 by exchange coupling. By setting the coercive force energy of the third magnetic layer 54 at room temperature to be lower than the exchange coupling force, the magnetization directions of the first magnetic layer 52, the second magnetic layer 53, and the third magnetic layer 54 are changed. At room temperature, they are aligned in the same direction by exchange coupling. However, when each magnetic layer is a ferrimagnetic material, the direction of the sublattice magnetization of each magnetic layer is aligned by exchange coupling.

At the time of the reproducing operation, the domain wall moving type recording medium 50
Is locally heated to be higher than the Curie temperature Tc2 of the second magnetic layer 53. As a result, the exchange coupling via the second magnetic layer 53 does not restrict the magnetization of the third magnetic layer 54. On the other hand, the Curie temperature Tc3 of the third magnetic layer 54 is set to be higher than the temperature at the time of the reproducing operation, and the domain wall energy becomes smaller as the temperature rises. Move fast towards the center.

Each time the magnetic domain wall in the recording magnetic section approaches the temperature rising portion, such high-speed domain wall movement occurs. Therefore, if the domain wall moving type recording medium 50 is relatively moved with respect to the reproducing means, this can be solved. By detecting the accompanying change in the magnetic flux leakage from the third magnetic layer 54, information based on the domain wall position can be reproduced in time series.

Embodiment B. Hereinafter, the reproducing means of the present invention will be described with reference to the drawings. The present invention is not limited to the following examples without departing from the gist thereof, irrespective of the specific examples in the description. A domain wall displacement type recording medium 50 will be described as an example of the magnetic domain variation recording medium during reproduction. However, a magnetic domain variation recording medium during reproduction in which the magnetic domain expands / contracts (or disappears further) can be adopted. The magnetic domain expansion type recording medium will be described later in a ninth embodiment.

(B-1) First Embodiment FIG. 2 is a schematic sectional view showing the structure of a reproducing means according to a first embodiment of the present invention. Show.

The reproducing means has a heating means 1 and a single-pole type head 2. The single-pole type head 2 has an induction coil 22.
Is wound around the main magnetic pole 21. The heating means 1 includes a semiconductor laser 11 and a lens 12. During a reproducing operation, a light beam 13 obtained from the semiconductor laser 11 is condensed by the lens 12, and heats the domain wall moving type recording medium 50 from the substrate 51 side. The light beam 13 condensed by the lens 12 is arranged so that a temperature distribution in which the temperature increases as approaching the vicinity of the main magnetic pole 21 is given to the domain wall displacement type recording medium 50.

FIG. 3 is a schematic plan view showing the movement of the domain wall moving type recording medium 50 during the reproducing operation. In the figure, a region surrounded by a pair of arcs indicates a recording magnetic domain, a magnetic domain indicated by a symbol with a black dot surrounded by a white circle indicates an upward magnetic domain, a magnetic domain indicated by a symbol surrounded by a white circle with a X indicates a downward magnetic domain, Each is shown.
The curve group 9 is a group of isotherms indicating a temperature distribution, and the temperature indicated by the isotherm is higher as being located on the left side in the figure.

The domain wall moving type recording medium 50 moves in the medium moving direction relatively to the reproducing means. Thereby, the position of the domain wall is sequentially detected. The change in the leakage magnetic flux at this time causes the induction coil 22 of the single-pole type head 2 to excite a voltage, whereby the information recorded on the track can be reproduced.

The extending direction of the track 7 on which information is recorded is parallel to the medium moving direction. In other words, the moving direction of the domain wall motion recording medium 50 during the reproducing operation is parallel to that during the recording operation.

The magnetic field detection region 8 in FIG. 3 is a region where the magnetic head can detect a magnetic field with high sensitivity. Since the domain wall displacement type recording medium 50 and the single pole head main magnetic pole 21 are close to each other during the reproducing operation, the magnetic field detection region 8 The length along the medium moving direction is the thickness of the main magnetic pole 21, that is, the domain wall moving type recording medium 5.
0 along the direction of movement relative to the playback means
It is almost equal to t.

By the way, in order to prevent the recorded information from being disturbed by the reproducing operation, that is, to perform the non-destructive reading, the domain wall of the first magnetic layer 52 is set at the third temperature even at the reproducing temperature. It must be designed so that the domain wall does not move together with the magnetic layer 54. In the above-described reproducing operation, it is necessary to increase the Curie temperature Tc2 of the second magnetic layer 53 or higher by heating with the light beam 13, so that only the Curie temperature Tc3 of the third magnetic layer 54 is required to satisfy the above requirement. However, the Curie temperature Tc1 of the first magnetic layer 52 must be set higher than the Curie temperature Tc2 of the second magnetic layer 53, and the domain wall coercive force of the first magnetic layer 52 must be larger than the domain wall coercive force of the third magnetic layer 54. Must.

Then, at the time of the reproducing operation, the domain wall of the first magnetic layer 52 also moves relatively to the main magnetic pole 21 to give a magnetic flux change, and the magnetic flux change based on the first magnetic layer 52 The change in the leakage magnetic flux from the three magnetic layers 54 becomes noise.

However, according to the present invention, a pair of magnetic domains adjacent to each other in opposite directions occupy a minimum length λ (hereinafter referred to as a “shortest recording wavelength”) along the medium moving direction.
The thickness Lt of the main magnetic pole 21 is designed widely. Therefore, even if the leakage magnetic fluxes from the individual magnetic domains of the first magnetic layer 52 flow into the main magnetic pole 21, they cancel each other out and do not become a large noise. Therefore, domain wall displacement reproduction with low noise is possible, and the first problem is solved. Similarly,
The second problem is also solved because the magnetic field change due to the minute unevenness of the moving domain wall is suppressed.

Since the shortest recording wavelength is determined by the employed coding modulation method and linear recording density, if these specifications are determined in advance, the thickness Lt of the main magnetic pole 21 is set to be equal to or longer than the shortest recording wavelength λ. Can be widely designed. In other words, the recording may be performed by setting the thickness Lt of the main pole 21 and adopting the coded modulation method and the linear recording density that can obtain the shortest recording wavelength λ shorter than this.

Since the light beam 13 is not focused on a track that is not a target of the reproducing operation, the temperature rise of the third magnetic layer 54 of the adjacent track is not large, and no domain wall movement occurs, or even if it occurs, it is insufficient. It is. The noise generated from these also cancels out each other between the magnetic domains. Therefore, crosstalk is greatly reduced, and the third problem can be solved.

The vicinity of the tip of the main magnetic pole 21 which is heated accompanying the domain wall displacement type recording medium 50 during reproduction is also close to the main magnetic pole 21.
By designing the thickness Lt to be large, the cross-sectional area increases, and the cooling efficiency by heat conduction improves. Therefore, the deterioration of the magnetic characteristics of the main pole 21 is greatly reduced, and the fourth problem is also solved.

The single-pole type head 2 may be provided with an auxiliary magnetic pole arranged as a magnetic flux return path so as to be magnetically separated from the main magnetic pole 21. When installed at a distance where magnetic interaction occurs, it functions as a ring type head rather than a single pole type head.

(B-2) Embodiment 2: When reproducing the domain wall moving type recording medium 50, the light beam 13 is focused on the domain wall moving type recording medium 50 at a position facing the main magnetic pole 21. FIG. 4 is a plan view schematically showing the positional relationship between the recording track 7 and the isotherm groups 9a and 9b. The temperature of the domain wall moving type recording medium 50 from the side where the domain wall moving type recording medium 50 moves closer to the main magnetic pole 21 (hereinafter referred to as “medium inflow side”) in the medium moving direction is indicated by a group of isothermal lines 9a. However, on the side where the magnetic domain wall moving type recording medium 50 moves farther from the main magnetic pole 21 than the position where the temperature has the maximum value (hereinafter referred to as “medium outflow side”), the magnetic domain wall moving type recording medium 50 moves toward the medium moving direction. The temperature of the recording medium 50 is a group of isothermal lines 9b.
Descend as shown in.

Accordingly, not only the domain wall existing on the medium inflow side of the domain wall displacement type recording medium 50 but also the domain wall on the medium outflow side from the highest temperature point are determined based on the temperature gradient indicated by the isotherm group 9b in the medium moving direction. And move in the opposite direction. Such movement of the domain wall occurs when the magnetic domain of the first magnetic layer 52 becomes lower than the Curie temperature Tc2 of the second magnetic layer 53 after the domain wall displacement recording medium 50 has passed the highest temperature point. This can occur when the image is transferred to the third magnetic layer 54.

The change in the leakage magnetic flux caused by such movement of the domain wall in the opposite direction becomes noise superimposed on the reproduced signal. This embodiment provides a means for solving such a problem.

FIG. 5 is a schematic sectional view showing the structure of the reproducing means according to the second embodiment of the present invention, showing the positional relationship with the domain wall moving type recording medium 50. The reproducing means according to the present embodiment has a configuration in which a magnetic substance 23 is added to the reproducing means described in the first embodiment.

The magnetic body 23 is provided on the medium outflow side with respect to the main magnetic pole 21 and at a distance G from the main magnetic pole 21.
First, the magnetic body 23 functions as a magnetic shield for the main magnetic pole 21 and blocks a magnetic field change due to the reverse movement of the domain wall. Second, the third magnetic layer 54 and the magnetic body 23 are magnetostatically coupled, and the movement of the domain wall in the opposite direction is stopped at a position facing the magnetic body 23. Either of these two functions or a combination of these two functions can effectively reduce noise due to the movement of the domain wall in the opposite direction.

For example, the focused diameter of the light beam 13 is 0.2 to
The thickness is set to about 2 μm, the thickness of the magnetic body 23 along the medium moving direction is set to 30 nm or more, and the distance G is set to 10 nm or more.

(B-3) Third Embodiment FIGS. 6 and 7 are schematic sectional views showing the structure of a reproducing means according to a third embodiment of the present invention. The positional relationship is also shown.

As the reproducing means, a heating means 1 and a magnetic flux sensitive head 4 are employed. The magnetic flux sensitive head 4 has a magnetic flux sensitive element 41 and a medium outflow side magnetic shield 42. The electric conductivity or electromotive force of the magnetic flux sensitive element 41 changes according to the magnitude of the magnetic flux flowing into the magnetic flux sensitive element 41. For example, MR (Magneto-Resisitive) element, GMR (Giant MR)
An element, a TMR (Tunnel MR) element, and a Hall element are employed. During the reproducing operation, the light beam 13 detects a change in magnetic flux due to the domain wall movement of the third magnetic layer 54 while locally heating the domain wall motion type recording medium 50 near the magnetic flux sensitive element 41.

In the present embodiment, as shown in FIG. 6, the medium inflow side magnetic shield 43 has a distance Ls to the magnetic flux sensitive element 41 along the medium moving direction set to be equal to or longer than the shortest recording wavelength λ. It is not provided as shown in FIG. As a result, the leakage magnetic fluxes input from the individual magnetic domains of the first magnetic layer 52 to the magnetic flux sensitive element 41 cancel each other out in the same manner as in the first embodiment, and a magnetic field change due to minute irregularities of the domain wall moving during domain wall movement reproduction is also detected. Not done.
Therefore, noise can be significantly reduced. Further, the leakage magnetic fluxes from the adjacent tracks cancel each other out, so that the crosstalk can be greatly reduced. Further, the medium outflow side magnetic shield 42 effectively reduces noise caused by the movement of the domain wall in the reverse direction as in the second embodiment.

Further, no magnetic substance is arranged close to the medium inflow side of the magnetic field detecting means. Even when the medium inflow side magnetic shield 43 is provided, since this is not in the vicinity of the magnetic flux sensitive element 41, a magnetostatic interaction that may occur between the medium inflow side magnetic shield 43 and the third magnetic layer 54. Does not hinder the movement of the domain wall. Therefore, when detecting using the magnetic flux sensing element 41, it is possible to detect a change in the leakage magnetic flux accompanying the domain wall movement from the initial stage when the domain wall starts to move. Therefore, a large amplitude of the reproduced signal can be obtained.

FIG. 8 is a schematic sectional view showing a modification of the third embodiment of the present invention. In the configuration shown in FIG. 7, a magnetic flux sensitive element 41 is provided on a non-magnetic holding base 61. Characteristically different. It is obvious that the same effect as the structure shown in FIG. 7 can be obtained in such a structure. Further, the following effects are added in this modification.

When the domain wall displacement type recording medium 50 is heated during the reproducing operation, the vicinity of the tip of the magnetic flux sensitive element 41 is heated by heat conduction. However, in this modification, the holding base 61
As a result, the magnetic flux sensitive element 41 dissipates heat, so that the cooling efficiency is good and the deterioration of the magnetic characteristics can be almost eliminated. A heat conductive layer having high heat conductivity may be interposed between the magnetic flux sensitive element 41 and the holding base 61.

When the magnetic flux sensitive element 41 is formed on the holding base 61, the manufacturing process is simpler than when the magnetic flux sensitive element 41 is formed alone, and the manufacturing can be performed at low cost. Further, the reproduction characteristics can be improved by controlling the magnetic characteristics of the magnetic film constituting the magnetic flux sensitive element 41, for example, the intensity and direction of the magnetic anisotropy, depending on the crystal orientation of the surface of the holding base 61 and the like. Further, since the underlayer of the magnetic flux sensitive element can be made smoother, there is an effect that the reproduction characteristics of the magnetic flux sensitive element 41 can be improved. This effect is particularly significant when a TMR element whose characteristics are greatly influenced by the smoothness of the underlayer is used as the magnetic flux sensitive element 41.

The magnetic flux sensitive element 41 may be of a type that detects a magnetic flux perpendicular to the film surface of the magnetic flux sensitive film, or a type that detects a magnetic flux parallel to the film surface.

(B-4) Fourth Embodiment: FIG. 9 is a schematic sectional view showing the structure of a reproducing means according to a fourth embodiment of the present invention. Show.

The reproducing means has a heating means 1 and a ring type head 3A. The ring type head 3A includes a ring core 31 around which an induction coil 32 is wound. The heating unit 1 can be configured in the same manner as in the first embodiment, and the light beam 13 locally heats the domain wall displacement type recording medium 50 near the gap of the ring type head 3A. Then, by detecting the leakage magnetic flux from the third magnetic layer 54 with the ring-type head 3A, the movement of the domain wall is detected and the reproducing operation is performed.

In the present embodiment, as in the first embodiment, the length of the magnetic field detection area 8 (FIG. 3) in the medium moving direction is set to be equal to or longer than the shortest recording wavelength λ. Therefore, the gap length Lg1 of the ring type head 3A is set to be equal to or longer than the shortest recording wavelength λ.

By performing the reproducing operation in the same manner as in the first embodiment, the first to third problems can be solved in the same manner as in the first embodiment. Further, since the gap length Lg1 is made wide, both of the two magnetic pole portions of the ring core 31 facing the domain wall displacement recording medium 50 can be separated from the highest temperature point of the magnetic film. Therefore, the temperature rise is small and the deterioration of the magnetic characteristics can be greatly reduced, and the fourth problem can also be solved.

Further, unlike the single pole head, it is possible to increase the thickness of the magnetic pole portion independently of the size of the magnetic field detection region 8, thereby increasing the heat radiation efficiency and further reducing the deterioration of the magnetic characteristics. be able to.

The MIG (Metal-In) is attached to the ring type head 3A.
-Gap) type head may be adopted.

(B-5) Fifth Embodiment FIG. 10 is a schematic sectional view showing the structure of a reproducing means according to a fifth embodiment of the present invention. Show.

In this embodiment, a ring-type magnetic flux sensitive head 3B is employed. The magnetic flux sensitive head 3B is provided with an upper core 33 and a lower core 34, and a magnetic flux sensitive element 35 sandwiched between the upper core 33 and the lower core 34, the electric conductivity or the electromotive force of which changes depending on the magnitude of the magnetic field. Have been. That is, the upper core 33, the lower core 34, and the magnetic flux sensitive element 35 form a ring-type magnetic circuit. The magnetic flux sensing element 35 is provided on the holding base 61, and the upper core 33
Is disposed on the medium outflow side of the lower core 34.

The heating means 1 can be configured in the same manner as in the first embodiment, and the light beam 13 locally heats the domain wall displacement type recording medium 50 near the gap of the magnetic flux sensitive head 3B. Then, by detecting the leakage magnetic flux from the third magnetic layer 54 with the magnetic flux sensitive head 3B,
The reproducing operation is performed by detecting the movement of the domain wall.

In the present embodiment, the gap length Lg2 of the magnetic flux sensitive head 3B is formed to be wider than the shortest recording wavelength λ. Thereby, the first to third problems are solved as in the first embodiment.

When the domain wall displacement type recording medium 50 is heated, the vicinity of the gap is heated by heat conduction.
Since the gap length Lg2 is formed widely, the upper core 3
3 and the lower core 34 can be separated from the highest temperature point.
Therefore, the temperature rise of the upper core 33 and the lower core 34 is small,
Deterioration of magnetic properties can be greatly reduced. Therefore, the fourth problem can be solved.

Further, since the magnetic flux sensitive element 35 is provided on the holding base 61 in contact with the holding base or via the heat conductive layer, the magnetic characteristics are deteriorated in the same manner as in the modification of the third embodiment. Can be almost eliminated, and the reproduction characteristics of the magnetic flux sensitive element 35 can be improved.

(B-6) Various Modifications: In the reproduction modes of the first to sixth embodiments described above,
In the case where an encoding modulation method that can determine not only the shortest recording wavelength λ but also the longest recording wavelength な ど such as an RLL (Run Length Limit) code is used, the thickness Lt of the main pole 21 in the single-pole type head 2 Lengths Lg1 and Lg in the ring type head 3A and the magnetic flux sensitive type head 3B
2. The distance Ls between the magnetic flux sensitive element 41 and the medium inflow side magnetic shield 43 in the magnetic flux sensitive head 4 is not only set to be equal to or longer than the shortest recording wavelength λ, but also to the length near the longest recording wavelength Λ, or If the length is longer than that, the effect of the present invention is further enhanced.

The heating means 1 can be used in combination with a light emitting source such as a semiconductor laser and a condensing element such as a lens and a condensing hologram element.

An optical waveguide having an opening toward the recording medium and a light emitting source such as a semiconductor laser and optically coupled to the light emitting source at the other end may be used. As the optical waveguide, an optical fiber having a sharpened tip can be used in addition to the planar type element. When an optical fiber is used, it is preferable to use an optical fiber in which the diameter of the opening is narrowed by extending the tip, or the diameter of the opening is extremely narrowed by sharpening the tip by chemical etching.

When an optical waveguide is used, the heating means and the magnetic field detection means may be integrated on the same side of the recording medium. As the heating means other than the light irradiation, a heater in which a heat transfer element having a sharp-edged tip attached to a heater by resistance heating may be used.

[0070]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a main magnetic pole 21, an auxiliary magnetic pole, a yoke, a magnetic body 23 arranged on the medium outflow side of the main magnetic pole, a ring core 31 of a ring type head 3A, a magnetic flux sensitive type head 3 are shown.
The upper core 33, the lower core 34, and the magnetic shields 42 and 43 of the magnetic flux sensitive head 4 are made of ferrite or FeNi.
(Permalloy), FeNiCo, FeSiAl (Sendust), CoZr
A magnetic material mainly containing Nb, FeN, FeCoB, or the like, or a material combining these can be used.

The material of the induction coils 22 and 32 is AlTa.
And a wiring material such as Cu can be adopted.

When an MR element is used as the magnetic flux sensitive elements 35 and 41, FeNi or FeNiCo can be used as the material.

The holding base 61 is made of a hard material such as glass, ceramic, alumina, silicon nitride, alumina titanium carbide, gold, silver, copper, aluminum or an alloy thereof, or a high heat conductive material containing these as a main component. It is desirable to use a metal with a low percentage or other hard metal. Further, the holding base 61 can also serve as a slider for causing the reproducing means to float on the recording medium.

When a heat conductive layer is provided between the holding base 61 and the magnetic flux sensitive element 35 (or 41), gold, silver, copper, aluminum or an alloy thereof having a thickness of 0.05 μm or more is used as the heat conductive layer. Alternatively, a material having high thermal conductivity containing these as a main component can be used.

C Specific embodiment. Hereinafter, the reproducing means of the present invention will be described more specifically.

(C-1) Example 1: This example relates to the first embodiment. FIG. 11 is a front view showing the configuration of the single-pole type head 2 viewed from the medium outflow side, and FIG.
FIG. 3 is a cross-sectional arrow view at a position AA.

First, using a ferrite material, a holding base 62 also serving as a slider for floating the reproducing means is prepared.
An auxiliary magnetic pole 24 made of permalloy was formed on the medium outflow side of the holding base 62 with a thickness of 0.05 μm. Holding base 6
2 also functions as a return path of magnetic flux together with the auxiliary magnetic pole 24. The film was formed by a sputtering method, and the pattern was formed by a method using photoresist exposure using a general adhesion mask and wet etching or ion milling. The following film formation and pattern formation can be similarly performed.

A main magnetic pole 21 was formed on the auxiliary magnetic pole 24 using permalloy, and an induction coil 22 was formed using copper. The induction coil 22 is separated from the main magnetic pole 21 and the auxiliary magnetic pole 24 by an insulating layer 26 made of alumina (not shown in FIG. 11). The induction coil 22 also serves as a recording coil.

The distance between the main magnetic pole 21 and the auxiliary magnetic pole 24 is 8 μm.
m, the width of the main pole in the track width direction was 2 μm, and the thickness in the track direction was 0.5 μm. In the heating means 1, the light beam 13 generated by the semiconductor laser 11 was a laser beam having a wavelength of 688 nm, and the lens 12 was a spherical lens having a numerical aperture of 0.55. The condensing shape of the light beam 13 on the surface of the domain wall displacement type recording medium 50 (on the side of the third magnetic layer 54) is a circular shape having a diameter of 1 μm at which the light intensity becomes 1 / square of the natural logarithm base e. Was.

The light beam 13 is adjusted so as to be condensed substantially immediately below the main magnetic pole 21, and the light beam 13 and the single-pole type head 2 are adjusted.
The heating means 1 and the single pole type head 2 were connected by a highly rigid arm so that the relative position of the heating means 1 and the single pole type head 2 did not change.

The domain wall displacement type recording medium 50 was prepared as follows. The substrate 51 has a thickness of 0.8 mm and an outer diameter of 86 m.
m chemically strengthened glass disks were used. A 3 μm-thick UV-curable resin is applied uniformly, and the master is brought into close contact with the UV-curable resin and irradiated with UV light from the back side to form a spiral 0.4 μm deep and 0.4 μm wide spiral on the UV curable resin. Guide grooves were formed at a pitch of 1 μm. A track is formed on a land portion having a width of 0.6 μm sandwiched between the guide grooves. On the substrate 51, the following three types of magnetic layers were continuously formed by sputtering.

First magnetic layer 52: material TbFeCoCr,
80 nm thick, Tc1 = 380 ° C. Second magnetic layer 53: material NdDyFeCr, thickness 30n
m, Tc2 = 110 ° C. Third magnetic layer 54: material GdFeCoTi, thickness 90n
m, Tc3 = 300 ° C. A 50 nm SiC film was provided thereon as a protective film, and a fluorine-based lubricant was further applied thereon by a spin coater to a thickness of about 3 nm. The total thickness of the magnetic film is 0.2 μm, and the tracks of the third magnetic layer 54 are magnetically weakly coupled to each other by the guide groove having a depth of 0.4 μm. Therefore, if the temperature is raised to Tc2 or more, the domain wall of the third magnetic layer 54 can be easily moved along the track without being affected by the domain wall on the side surface of the magnetic domain (plane parallel to the extending direction of the track). .

The domain wall moving type recording medium 50 prepared as described above is rotated at 4500 rpm, and a radius of 40 mm
The recording experiment was performed by floating the single-pole type head 2 of the present example at the position shown in FIG. First, while irradiating the light beam 13 with a power of 10 mW on the surface of the domain wall moving type recording medium 50 from the heating means 1 to the information track for one round, the recording magnetic domain has a single frequency of 0.16 μm. Thus, an alternating current was supplied to the induction coil 22. At this time, tracking was performed by detecting reflected light of laser light.

The recorded domain-wall-moving recording medium 50 was observed from the side of the substrate 51 with a polarization microscope using a magnetic domain. Although the width of the main pole 21 of the single-pole type head 2 in the track width direction is 2 μm, only the high temperature portion at the center of the region heated by the light beam 13 is recorded, so that only one track is recorded. It was confirmed that no information was recorded on the adjacent track.

Next, the recorded magnetic domain wall moving type recording medium 50 was rotated at 4500 rpm, and a reproduction experiment was performed by the single pole type head 2. First, the power of the light beam was reduced to 1 mW so as not to destroy the recorded information, and tracking was performed so that the light beam 13 hit the recorded track. At this stage, it is considered that the temperature of the magnetic layers 52 to 54 does not exceed Tc2 and the domain wall motion of the third magnetic layer 54 does not occur. Since the thickness of the main magnetic pole 21 was 0.5 μm, which was larger than the recording magnetic domain period of 0.16 μm, almost no reproduced signal could be obtained.

Next, when the power of the light beam 13 is increased, the reproduced signal sharply increases when the power exceeds 3 mW.
At 4.5 mW a 50 dB CN ratio (carrier to noise ratio) was obtained. It is considered that domain wall motion occurred in the third magnetic layer 54. For practical use, a CN ratio of about 43 dB to about 48 dB or more is generally required.
The N ratio was at a level sufficient for practical use.

Further, the same recording was performed not only on one track but also on 11 adjacent tracks. At this time, 1
The recording frequency is slightly changed for each track so that it is possible to determine which track is being reproduced during reproduction. 1
When the center track of one track is reproduced, C
The N ratio was almost the same as that for one track recording. Further, despite the width of the main pole 21 in the track width direction being 2 μm and being wider than the track pitch of 1 μm, the crosstalk from the adjacent track to the reproduction signal is −2.
6 dB, which is a sufficiently low level for practical use.

(C-2) Embodiment 2 This embodiment relates to the second embodiment. FIG. 13 shows a configuration of the single-pole type head 2 and is a cross-sectional view at a position corresponding to FIG. Example 1
An alumina insulating film 26 is further formed on the element having the same configuration as the single-pole type head 2 of FIG.
0.2 μm away from the magnetic material 23 to a thickness of 1 μm
Of permalloy film. The single pole type head 2 and the heating means 1 and the domain wall moving type recording medium 5 also used in the first embodiment.
0, a regeneration experiment similar to that of Example 1 was performed.

In recording and reproduction of one track, a CN ratio of 53 dB was obtained, and a noise reduction effect of 2 dB was obtained as compared with the first embodiment. In recording and reproduction of continuous tracks, a low crosstalk value of -26 dB was obtained as in the first embodiment.

(C-3) Third Embodiment: This embodiment relates to the third embodiment. FIG. 14 is a sectional view showing the configuration of the magnetic flux sensitive head 4. A magnetic flux sensitive head 4 was prepared as follows.

First, using a ferrite material, a holding base 62 also serving as a slider for floating the reproducing means is prepared.
On the medium outflow side of the holding base 62, a medium inflow side magnetic shield film 43 made of CoZrNb was formed with a thickness of 1 μm. In this case, the holding base 62 also has a role as a medium inflow side magnetic shield.

Next, an alumina insulating film 44 is formed with a thickness of 1.5 μm, and a 0.2 μm thick permalloy M
An MR element 41 having an R film was formed. Further, an alumina insulating film 45 was laminated, and a medium outlet magnetic shield 42 made of permalloy having a thickness of 1 μm was formed through the alumina insulating film 45.

Using the magnetic flux sensitive type head 4 thus manufactured, the heating means 1 used in Example 1, and the domain wall moving type recording medium 50, a reproduction experiment similar to that in Example 1 was performed. The distance between the MR element 41 and the medium inflow side magnetic shield 43 (the thickness of the insulating film 44 is 1.5 μm) is about 10 times the recording domain period. In recording and reproduction of one track, a CN ratio of 53 dB was obtained. In recording and reproduction of continuous tracks, a low crosstalk value of -27 dB was obtained.

(C-4) Embodiment 4: This embodiment also relates to the third embodiment. FIG. 15 is a sectional view showing the configuration of the magnetic flux sensitive head 4. A magnetic flux sensitive head 4 was prepared as follows.

First, using an alumina titanium carbide material (non-magnetic), a holding base 61 also serving as a slider for floating the reproducing means is prepared. The GMR element 41 was formed on the holding base 61 on the medium outflow side. GMR element 41 is CoZ
The spin-valve element was composed of an underlayer of rNb, a free layer of CoFe, a nonmagnetic layer of Cu, a pin layer of CoFe, and a bias layer of IrMn.

Further, a thickness of 0.5 μm is formed on the GMR element 41.
A m-alumina insulating layer 45 was provided, and a medium outlet magnetic shield 42 made of permalloy having a thickness of 1 μm was formed through the alumina insulating layer 45.

Using the magnetic flux sensitive type head 4 thus manufactured, the heating means 1 used in Example 1, and the domain wall moving type recording medium 50, a reproduction experiment similar to that in Example 1 was performed. 56 dB for recording and playback of one track
Was obtained. In recording and reproduction of a continuous track, a low crosstalk value of -29 dB was obtained.

Further, the medium outflow side magnetic shield 42 is GM
When the R element 41 is formed so as to cover not only the medium outflow side but also the side surface (plane parallel to the track extending direction) of the GMR element, the same CN of 56 dB is used for recording and reproduction of one track. Although the ratio was kept at a low level, a very low crosstalk value of -47 dB was obtained in recording and reproduction of continuous tracks. This indicates that the magnetic shield 42 has a high effect of magnetically shielding the GMR element 41 from the adjacent track.

(C-5) Comparative Example 1: This comparative example is to be compared with Examples 3 and 4. A magnetic flux sensitive head was manufactured in the same manner as in Example 3 except that the thickness of the alumina insulating film 44 was changed to 0.09 μm.

Using the magnetic flux sensitive head thus manufactured, the heating means 1 and the domain wall moving recording medium 50 used in Example 1, a reproduction experiment similar to that in Example 1 was performed.
In this case, the MR element 41 and the medium inflow side magnetic shield 43
(The thickness of the insulating film 44 is 0.09 μm) is shorter than the recording magnetic domain period of 0.16 μm. In recording and reproduction of one track, the CN ratio was 40 dB, which was much lower than that of Example 3. This was due to both low signal amplitude and high noise. Also, in the recording and reproduction of the continuous track, the crosstalk value of −17 dB was significantly higher than that of the third embodiment.

(C-6) Embodiment 5: This embodiment relates to the fourth embodiment. FIG. 16 is a front view showing the configuration of the ring-type head 3A as viewed from the medium outflow side, and FIG.
6 is a cross-sectional arrow view at a position BB of FIG. First, using a ferrite material, a holding base 62 also serving as a slider for floating the reproducing means is prepared. A lower core 34 made of permalloy was formed with a thickness of 1 μm on the medium outflow side of the holding base 62. In this case, since the holding base 62 also serves as a return path for the magnetic flux, it also plays the role of a ring-type magnetic circuit.

The lower core 34 has a permalloy upper core 33 on it.
And the induction coil 32 was formed using copper, respectively.
The induction coil 32 includes an insulating layer 36 made of alumina.
(Not shown in FIG. 161) and is isolated from the upper core 33 and the lower core 34. The induction coil 32 also serves as a recording coil.

The gap length between the upper core 33 and the lower core 34 was set to 0.5 μm, the width of the upper core 33 in the track width direction was 3 μm, and the thickness in the track direction was 1 μm.

Using the ring-shaped head 3A manufactured as described above, the heating means 1 used in Example 1, and the domain wall moving type recording medium 50, a reproduction experiment similar to Example 1 was performed.
When recording and reproducing one track, the CN ratio is 49.
dB. In recording and reproduction of a continuous track, a low crosstalk value of -28 dB was obtained.

(C-7) Embodiment 6: This embodiment relates to the fifth embodiment. FIG. 18 is a sectional view showing the configuration of the magnetic flux sensitive head 3B. A magnetic flux sensitive head 3B was prepared as follows.

First, using an alumina titanium carbide material, a holding base 61 also serving as a slider for floating the reproducing means is prepared. An MR having a 0.2 μm thick MR film made of FeNiCo on the medium outflow side of the holding base 61.
An element 35 was formed. Next, a lower core 34 and an upper core 33 made of permalloy having a thickness of 1 μm were formed so that the MR element 35 became a part of a magnetic circuit. Upper core 33 and lower core 34
Sandwiches an insulating layer 36 made of alumina, and has a thickness of 0.5 μm, that is, a gap length. Upper core 33,
The width of the lower core 34 in the track width direction was 3 μm.

Using the magnetic flux sensitive head 3B thus manufactured, the heating means 1 and the domain wall moving recording medium 50 used in Example 1, a reproduction experiment similar to that in Example 1 was performed. In recording and reproduction of one track, the CN ratio was 54 dB. In recording and reproduction of a continuous track, a low crosstalk value of -28 dB was obtained.

(C-8) Embodiment 7: This embodiment is also related to the fifth embodiment. FIG. 19 is a sectional view showing the configuration of the magnetic flux sensitive head 3C. A magnetic flux sensitive head 3C was prepared as follows.

First, using an alumina titanium carbide material, a holding base 61 also serving as a slider for floating the reproducing means is prepared. An auxiliary magnetic pole 24 made of permalloy is placed on the medium outlet side of the holding base 61 in the same manner as in the first embodiment.
It was formed with a thickness of 05 μm. A GaAs Hall element having a thickness of 0.1 μm was locally provided on the auxiliary magnetic pole 24, and the main magnetic pole 21 connected to the Hall element 24 was formed using permalloy. The main magnetic pole 21 and the auxiliary magnetic pole 24 were used as current input terminals of the Hall element 24, and a Hall voltage output terminal was separately provided (not shown).

On the auxiliary magnetic pole 24, the magnetic body 23 was formed of a 1 μm thick permalloy film at a distance of 0.2 μm from the main magnetic pole 21 to the side opposite to the holding base 61. However, magnetic material 2
Reference numeral 3 covers not only the medium outflow side of the main pole 21 but also the side surface of the main pole 21. Main magnetic pole 21, auxiliary magnetic pole 24, magnetic body 2
The space between 3 is filled with an alumina insulating film 26.

Using the magnetic flux sensitive head 3C thus manufactured, the heating means 1 and the domain wall moving recording medium 50 used in Example 1, a reproduction experiment similar to that in Example 1 was performed. In recording and reproduction of one track, the CN ratio was 53 dB. In recording and reproduction of continuous tracks, a low crosstalk value of -45 dB was obtained. This indicates that the magnetic substance 23 has a high effect of magnetically shielding the Hall element 24 from the adjacent track.

(C-9) Example 8 This example also corresponds to the third embodiment. FIG. 20 is a perspective view illustrating the configuration of the magnetic head 5 according to the present embodiment. In order to facilitate understanding of the configuration, each component is shown separately along the medium moving direction, but in actuality, they are in contact with each other to form the magnetic head 5. The magnetic head 5 has a magnetic flux detecting means and a heating means integrally formed, and is manufactured as follows.

First, using an alumina titanium carbide material, a holding base 61 also serving as a slider for floating the reproducing means is prepared. An MR element 41 made of permalloy and a pair of AlTa electrodes 46 sandwiching the MR element 41 in the track width direction were formed on the holding base 61 on the medium outflow side. MR
The width of the element 41 in the track width direction was 5 μm, and the thickness in the track direction was 0.06 μm. 0.2μm thick on it
A medium outflow-side magnetic shield 42 made of permalloy having a thickness of 0.8 μm was formed via the alumina insulating film 45. These constitute a magnetic flux detecting means.

Further, an optical waveguide was formed on the medium outflow side magnetic shield 42 to form a heating means. The optical waveguide includes a core 13 and a clad 14, and the clad 14 includes a first layer 14a closer to the holding base 61 and a second layer 14b farther away. The core 13 is provided on the first layer 14a using tantalum oxide having a refractive index of 2.2 so as to extend in a direction perpendicular to both the medium moving direction and the track width direction. The cross-sectional dimension of the core 13 is 1 in the track width direction.
μm, and the thickness in the track direction was 0.1 μm.

The second layer 14b, together with the first layer 14a,
3 is sandwiched, but in order to make it easy to grasp the configuration, a part of the core 13 is exposed and drawn. Clad 1
Silicon oxide having a refractive index of 1.46 was used as the material of No. 4, and its thickness was 0.3 μm as the total thickness of the first layer 14a and the second layer 14b.

The core 13 and the clad 14 were optically coupled to a laser diode having a wavelength of 635 nm via an optical fiber at the end face opposite to the opening face 15a facing the information recording medium.

The magnetic head 5 configured as described above
A reproduction experiment similar to that of the first embodiment was performed using the magnetic domain wall displacement type recording medium 50 employed in the first embodiment. When the power of the light beam at the time of reproduction was 4.7 mW, a CN ratio of 51 dB was obtained in recording and reproduction of one track. Also, in recording and reproduction of continuous tracks, the CN ratio was almost the same as in recording and reproduction of one track. Crosstalk is caused by the MR element 41
Has a track width of 5 μm and a track pitch of 1 μm
Although it was wider, it was as low as -29 dB, which was a sufficiently low level for practical use.

(C-10) Embodiment 9: In Embodiments 1 to 8, the recording / reproducing characteristics of the domain wall moving type recording medium 50 have been shown, but at least the reproducing layer and the memory layer for retaining information are provided. The magnetic domain of the memory layer is magnetically transferred to the reproducing layer by elevating the temperature of the magnetic layer at the time of reproducing, or a magnetic super-resolution type configured so that the magnetic domain magnetically transferred to the reproducing layer is enlarged or reduced or further disappears. Even with a magnetic domain expansion reproduction type medium, the same effect can be obtained in that the domain wall moves during transfer, enlargement, reduction, or disappearance. In this embodiment,
The case where a magnetic domain expansion reproduction type recording medium is used will be described.

In the magnetic domain expansion reproduction type recording medium, a memory layer / non-magnetic layer / reproduction layer is formed in order from the side closest to the substrate. In this embodiment, the first magnetic layer 5 shown in the first embodiment is used.
2 as a memory layer, SiC as a nonmagnetic layer with a thickness of 10 nm, and a GdFeCo as a reproducing layer.
Ti was provided with a thickness of 80 nm. The Curie temperature of GdFeCoTi was set to Tc3 in the same manner as in Example 1.
= 300 ° C.

The above-mentioned reproducing layer has an easy axis of magnetization in the film plane at room temperature. When the temperature is raised to about 120 ° C., the easy axis of magnetization is oriented in the normal direction of the film surface. The composition of the reproducing layer is adjusted so that the force for holding the minute magnetic domains is weaker than that of the memory layer, and no minute magnetic domains exist. The saturation magnetization of the memory layer and the reproducing layer is designed to be maximum around 120 ° C., and the magnetostatic coupling force between the memory layer and the reproducing layer becomes maximum around this temperature. As a result, when the optical power at the time of reproduction is increased to raise the temperature of the magnetic film, the magnetic domains of the memory layer are magnetically transferred to the reproduction layer, and the transferred magnetic domains are enlarged to a size that is energetically stable.

The magnetic domain expansion reproduction type recording medium and the first embodiment
A reproduction experiment similar to that of the first embodiment was performed using the recording / reproducing means employed in the first embodiment. First, the power of the light beam 13 was reduced to 1 mW so as not to destroy the recorded information, and tracking was performed so that the recorded track was irradiated with the light beam. At this stage, since the temperature of the magnetic layer has not reached 150 ° C., magnetic transfer and magnetic domain expansion have not occurred, and a reproduced signal due to magnetic flux leakage from the reproducing layer cannot be obtained. When the thickness of the main magnetic pole 21 is 0.5 μm and the recording magnetic domain period is 0.1
Since it is thicker than 6 μm, there is almost no reproduced signal due to magnetic flux leakage from the memory layer.

Next, when the power of the light beam 13 was increased, the reproduced signal sharply increased when the power exceeded 2.8 mW, and a CN ratio of 48 dB was obtained at 3.8 mW. This is presumed to be due to the occurrence of magnetic transfer and magnetic expansion.

In recording and reproduction of continuous tracks, the CN ratio was almost the same as in recording and reproduction of one track, and no crosstalk was observed.
This is presumed to be due to the fact that magnetic transfer and magnetic domain expansion did not occur in the track adjacent to the track being reproduced.

An acceleration deterioration experiment was performed by supplying an optical power higher than the optimum optical power for recording / reproducing to the reproducing means of Embodiments 1 to 9 above. Was small, and was estimated to have a practically sufficient life under normal use conditions.

Further, in Examples 3, 4, 6, and 7, since the magnetic flux sensitive element is particularly provided in contact with the holding base, the cooling efficiency of the magnetic flux sensitive element is good, and almost no characteristic deterioration is observed even after the accelerated deterioration test. I couldn't.

In the recording / reproducing experiments of the first to ninth embodiments, the experiments were performed with the linear velocity of the information recording medium fixed. However, when the linear velocity was changed, the present invention could be realized by optimizing the experimental conditions. The effect of does not change. In the above description, the case where the information recording medium is in the form of a hard disk has been described. The effect remains the same.

Although the description has been given of the case of the floating recording and the floating reproduction, the effect of the present invention is not changed even when the contact recording and the contact reproduction are performed.

In the case where an MR element is used for the magnetic field detecting means, additional components such as a magnetic domain control film are omitted from the description, but they can be provided if necessary.

[0129]

As described above, according to the reproducing means of the present invention, an excellent reproduced signal quality having a high SN ratio and a small crosstalk can be obtained. Further, according to the present invention, it is possible to obtain a highly reliable reproducing means with a simple manufacturing process, low cost, and little characteristic deterioration.

According to the reproducing means according to claim 1 of the present invention or the magnetic recording method according to claim 8, even if the leakage magnetic flux from each magnetic domain of the memory layer flows into the reproducing means, they are not affected. They do not cancel each other out and become loud noises. In addition, a change in the magnetic field due to minute irregularities of the domain wall moving in the reproducing layer is also suppressed. Accordingly, domain wall displacement reproduction with low noise is possible. In addition, noise generated from adjacent tracks also cancels each other between the magnetic domains, so that crosstalk is greatly reduced.

According to the reproducing means of the present invention, since the thickness of the single pole head is set large,
The heat radiation efficiency can be improved, and even if the temperature of the reproducing layer is increased during reproduction, deterioration of the characteristics of the single pole head is suppressed.

According to the reproducing means of claim 3 of the present invention, the temperature distribution of the reproducing layer near the single pole head is increased during reproduction, and the temperature distribution decreases near the single pole head in the medium moving direction. Occurs, the noise from the domain wall moving based on this temperature distribution is shielded by the magnetic material or the movement of the domain wall is prevented.

According to the reproducing means of the fourth aspect of the present invention, the magnetic shield for the magnetic flux sensitive element is disposed apart from the shortest recording wavelength or longer, so that the effect of the first aspect of the present invention is enhanced.

According to the reproducing means of the present invention, since the thickness of the ring head can be set to be large, the heat radiation efficiency can be improved, and even if the temperature of the reproducing layer is increased during reproduction, Deterioration of the characteristics of the head is suppressed.

According to the reproducing means of the present invention, while improving the heat radiation efficiency of the magnetic flux sensitive element, it is possible to improve the characteristics of the magnetic flux sensitive element whose characteristics are greatly affected by the smoothness of the base. Thus, even when the temperature of the reproducing layer is increased during reproduction, deterioration of the characteristics of the magnetic flux sensitive element can be suppressed.

According to the reproducing means of the present invention, the effect of the reproducing means of the present invention can be enhanced.

According to the magnetic recording method of the ninth aspect of the present invention, the effect of the magnetic recording method of the eighth aspect can be enhanced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration of a domain wall displacement type recording medium.

FIG. 2 is a cross-sectional view illustrating a configuration of a reproducing unit according to the first embodiment of the present invention.

FIG. 3 is a plan view showing a reproducing operation according to the first embodiment of the present invention.

FIG. 4 is a plan view showing a reproducing operation according to Embodiment 2 of the present invention.

FIG. 5 is a cross-sectional view illustrating a configuration of a reproducing unit according to a second embodiment of the present invention.

FIG. 6 is a cross-sectional view illustrating a configuration of a reproducing unit according to a third embodiment of the present invention.

FIG. 7 is a cross-sectional view illustrating a configuration of a reproducing unit according to a third embodiment of the present invention.

FIG. 8 is a cross-sectional view illustrating a modified configuration of the reproducing unit according to the third embodiment of the present invention.

FIG. 9 is a cross-sectional view illustrating a configuration of a reproducing unit according to a fourth embodiment of the present invention.

FIG. 10 is a sectional view showing a configuration of a reproducing unit according to a fifth embodiment of the present invention.

FIG. 11 is a front view illustrating a configuration of a reproducing unit according to the first embodiment of the present invention.

FIG. 12 is a sectional arrow view showing a configuration of a reproducing unit according to the first embodiment of the present invention.

FIG. 13 is a cross-sectional view illustrating a configuration of a reproducing unit according to a second embodiment of the present invention.

FIG. 14 is a cross-sectional view illustrating a configuration of a reproducing unit according to a third embodiment of the present invention.

FIG. 15 is a cross-sectional view illustrating a configuration of a reproducing unit according to a fourth embodiment of the present invention.

FIG. 16 is a front view illustrating a configuration of a reproducing unit according to a fifth embodiment of the present invention.

FIG. 17 is a sectional arrow view showing a configuration of a reproducing unit according to a fifth embodiment of the present invention.

FIG. 18 is a cross-sectional view illustrating a configuration of a reproducing unit according to a sixth embodiment of the present invention.

FIG. 19 is a cross-sectional view illustrating a configuration of a reproducing unit according to a seventh embodiment of the present invention.

FIG. 20 is a perspective view illustrating a configuration of a reproducing unit according to an eighth embodiment of the present invention.

[Explanation of symbols]

7 track, 8 magnetic field detection area, 11 semiconductor laser, 12 lens, 13 light beam, 21 main magnetic pole, 2
2 induction coil, 23 magnetic body, 24 auxiliary magnetic pole, 31
Ring core, 32 Induction coil, 33 Upper core, 34
Lower core, 35, 41 Flux sensitive element, 42 Medium shield magnetic shield, 43 Medium shield magnetic shield, 50
Domain wall displacement type recording medium, 52 first magnetic layer, 53 second
Magnetic layer, 54 Third magnetic layer, 61, 62 Holding base.

Continued on the front page (72) Inventor Atsushi Fujita 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation F-term (reference) 5D006 BB01 BB02 BB05 BB07 BB08 CB01 CB04 CB07 CB08 DA00 EA03 5D029 JB05 JB09 JC11 WD11 5D032 GA02 GB23 5D075 AA03 CC11 CF03 5D091 CC02 CC26 DD01 DD09 DD11 DD30

Claims (9)

[Claims] A memory layer for holding a magnetic domain pattern;
The magnetic domain pattern of the memory layer is transferred at a temperature higher than a predetermined temperature, or the magnetic domain pattern generated at the predetermined temperature or less based on the magnetic domain pattern of the memory layer is higher than the predetermined temperature. The magnetic recording medium having a reproducing layer having at least one of the functions of expanding, contracting, or disappearing at the same time performs a relative movement in close proximity to each other, and reverses each other along the moving direction. A magnetic flux detection area for detecting the magnetic domain pattern of the reproduction layer, extending over the shortest recording wavelength, which is the minimum value of the length of the magnetic domain of the pair of memory layers adjacent in the direction along the direction of movement, Reproducing means for setting the magnetic recording medium; 2. The reproducing means according to claim 1, further comprising a single-pole head having a thickness along the moving direction that is equal to or longer than the shortest recording wavelength. 3. The magnetic recording medium according to claim 2, further comprising a magnetic body disposed on a side of the single pole head in a medium moving direction in which the magnetic recording medium moves relatively to the reproducing unit.
Reproduction means as described. 4. The apparatus according to claim 1, further comprising: a magnetic flux sensitive element for setting the magnetic flux sensing area; and a magnetic shield arranged at a distance from the magnetic flux sensitive element opposite to the medium moving direction and at least the shortest recording wavelength. The reproducing means according to 1. 5. The reproducing means according to claim 1, further comprising a ring head having a gap whose length along the moving direction is equal to or longer than the shortest recording wavelength. 6. A magnetic flux sensitive element, comprising: a holding base for holding the magnetic flux sensitive element from a side opposite to a medium moving direction in which the magnetic recording medium moves relative to the magnetic flux sensitive element. Item 2. The reproducing means according to Item 1. 7. The magnetic flux sensing area extends over a maximum value of a length occupied by a magnetic domain of a pair of memory layers adjacent to each other in opposite directions along the direction of movement. 6. The reproducing means according to any one of the above items 6. 8. A memory layer for holding a recorded magnetic domain pattern, wherein the recorded magnetic domain pattern is transferred at a temperature higher than a predetermined temperature or is lower than the predetermined temperature based on the recorded magnetic domain pattern. The magnetic domain pattern that has been generated in the expansion or contraction or disappears at a temperature higher than the predetermined temperature, or a reproduction layer having at least one of the functions, a magnetic recording medium having a close proximity The magnetic recording / reproducing method in which the magnetic flux detection region for performing the proper movement and extending the predetermined length along the direction of the movement and detecting the magnetic domain pattern of the reproducing layer is set for the magnetic recording medium. The minimum value of the length occupied in the direction of movement of the pair of magnetic domains adjacent to each other in the opposite direction in the recorded magnetic domain pattern is set to be equal to or less than the predetermined length. It recorded the magnetic recording method. 9. A maximum value of a length occupied in the direction of movement of a pair of magnetic domains adjacent to each other in opposite directions in the recorded magnetic domain pattern is set and recorded to be equal to or less than the predetermined length. The magnetic recording method according to claim 8, wherein