JP2012146362A - Perpendicular magnetic recording medium, manufacturing method therefor, and magnetic recording/reproducing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To use a magnetic head having a recording element and a reproducing element which are excellent in thermal stability and a recording property and are wider than a track period of a bit pattern, even when the bit pattern is densely integrated.SOLUTION: A truncated cone-shaped recording bit includes a thermally stable layer having large perpendicular magnetic anisotropy at a lower layer, and a high output layer having large saturation magnetic flux density at an upper layer. An outer peripheral part is a thermally stable area 22 of which the high output layer is removed and thermal stability is improved, and a center part is a reproduction area 21. Also, an inversion control area 23 of which perpendicular magnetic anisotropy and saturation magnetic flux density are made small is provided between the outer peripheral part and the center part.

Description

  The present invention relates to a perpendicular magnetic recording medium and a manufacturing method thereof, and more particularly to a perpendicular magnetic recording medium having a bit pattern structure in a recording portion, a manufacturing method thereof, and a magnetic recording method and a magnetic reproducing method using the perpendicular magnetic recording medium. .

  In recent years, magnetic recording devices such as magnetic disk drives (HDD) have been strongly demanded to improve recording density with the development of the information society. As a technique for increasing the recording density, the perpendicular magnetic recording method has been widely used instead of the conventional in-plane magnetic recording method. The perpendicular magnetic recording method forms recording bits so that the magnetizations are antiparallel to each other perpendicular to the film surface. The demagnetizing field in the magnetization transition region is small, so the magnetization transition is steeper than in the in-plane magnetic recording method. The region is formed and the magnetization is stable at a high recording density. For example, Patent Documents 1 and 2 disclose conventional perpendicular magnetic recording media.

  In order to further increase the density, it is necessary to further reduce each of the recording bits and the magnetization transition region therebetween. However, in general, the stability of the recording bit is Ku · V / kT (Ku is the magnetic anisotropy constant, V is the volume of the minimum magnetization reversal unit (magnetic cluster), k is the Boltzmann constant, and T is the absolute temperature). The smaller the value is, the more unstable it is. If Ku · V / kT is not about 100, the magnetization is reversed due to thermal fluctuation and the recorded information is lost. In the conventional perpendicular magnetic recording medium, a minute magnetic cluster is formed by using a thin film having a so-called granular structure in which a nonmagnetic material is deposited around a magnetic material. From several to several hundred magnetic clusters constitute one recording bit. In order to improve the thermal stability, the number of magnetic clusters can be reduced and the volume V can be increased. However, when the number of clusters carrying one recording bit is reduced, the roughness of the interface (magnetization transition region) of the recording bit is 1. It becomes larger due to the influence of the shape of each magnetic cluster, and the S / N deterioration of the reproduction signal is caused.

  Therefore, for further higher density, the transition region itself is eliminated, each recording bit is physically isolated, and each recording bit is composed of one magnetic cluster to improve thermal stability. Improved bit pattern media are being considered. A bit pattern medium is a medium in which a recording layer is isolated in units of recording bits by microfabrication or the like, and a guard band region in which no magnetization exists between recording bits. One-to-one magnetic cluster and recording bits, eliminating the magnetization transition region, and even recording bits that are smaller and closer in space due to higher density have excellent thermal stability, and the interface shape, roughness, and position dispersion of the recording bits are reduced. By doing so, good S / N can be expected. The bit pattern medium is disclosed in, for example, Patent Documents 3 and 4.

JP 2008-135138 A JP 2010-67335 A JP 2009-129501 A JP 2004-164692 A

  As described above, even in the bit pattern medium that can be expected to improve the thermal stability, the larger the volume V of one bit, the more stable and the output is improved. That is, it is important to reduce the guard band area between the recording bits and pack the recording bits.

  First, consider the shape and arrangement of bits in the production of highly integrated bit pattern media. It is desirable that the shape of the bit viewed from the surface of the medium is circular to form a hexagonal close-packed structure. In the production of a well-known bit pattern medium, a magnetic film is physically processed by etching, ion implantation, or the like, using a resist pattern made by a lithography technique or an imprint technique. For this reason, as with semiconductor microfabrication, the miniaturization limit of processing is largely due to the width of the groove to be processed. In order to integrate as small bits as possible with high spacing and as much integration as possible, it is appropriate to set the aspect ratio viewed from the plane of the bits to 1. In addition, the rounded edges of the pattern become more apparent as the pattern becomes finer. For this reason, the shape of the bit viewed from the plane is more suitable to have a cornerless shape such as a perfect circle or an ellipse than a cornered shape such as a square or a rectangle. As a result, the easiest way to arrange the recording bits with the highest density is to arrange the circular pattern in a hexagonal close-packed structure.

  However, in general, a disk-shaped HDD recording medium is arranged in such a manner that a plurality of recording bits are arranged in one arc to form a track, and the plurality of tracks are arranged concentrically. The HDD device rotates a recording medium at a high speed, and a magnetic head including a recording element and a reproducing element floats on the recording medium, and sequentially records or reproduces one track in the circumferential direction (track direction). By moving in the radial direction (cross-track direction) of the disc and moving to another track, one side of the recording medium can be recorded / reproduced by one magnetic head. The reduction of the recording bit width in the down-track direction is achieved by reducing the magnetic cluster size of the recording medium and reducing the high-frequency noise of the recording / reproducing element, while the limit of the bit width in the cross-track direction is the recording element, Due to the miniaturization of the physical width of the reproducing element, it is difficult to reduce it. The positioning of the recording bit of the medium and the magnetic head uses signal processing using a signal whose track direction is synchronized with the rotation of the medium, whereas the cross-track direction is a position information signal (servo in the medium). Signal) is used to mechanically move the arm to which the magnetic head is attached, so the alignment accuracy is lower than the track direction. For this reason, the recording bit shape of a general HDD medium is longer in the cross-track direction than in the track direction. In other words, in a bit pattern medium, if circular recording bits are arranged with high density like a hexagonal close-packed structure, it becomes difficult to perform recording and reproduction using a magnetic head.

  For this reason, Japanese Patent Application Laid-Open No. H10-228561 proposes a structure in which recording bits are arranged in an arc to form a track, and bits of adjacent tracks are arranged shifted by half a bit in the down-track direction. As shown in FIG. 1, this shape is close to a hexagonal close-packed structure, assuming that the recording bits are sufficiently smaller than the medium and the tracks are arranged in a straight line in parallel. By the way, the element width of the magnetic head inverts the bit of the adjacent track if the element width is not smaller than the width W2 between the bits of the adjacent tracks, even in the case of ideal recording / reproduction where the head does not cause a positional shift. I will let you. Also, if the width of the reproducing element is wider than W2, the signal of the adjacent track is detected, and the S / N deteriorates. Actually, the influence of the positional deviation of the head must be considered, and an element narrower than the width W2 is required. If the recording bit diameter W1 is increased and the guard band region is reduced in order to increase the thermal stability and signal output of the recording bit, the element width W2 is reduced, and the recording magnetic flux density of the recording head and the detection sensitivity of the reproducing element are reduced. A dilemma that declines.

  On the other hand, as a method of providing a medium having excellent thermal stability, a method of producing a medium having a large magnetic anisotropy Ku instead of a volume V is conceivable. However, in a medium with a large Ku, the magnetic flux density from the recording element necessary for reversal becomes large. Patent Documents 2 and 3 propose a method of forming a soft magnetic material with a small Ku on the outer periphery of a recording bit. However, the outer periphery closest to the adjacent bit is strongly influenced by the leakage magnetic flux (demagnetizing field) from the adjacent bit. If a region with a small Ku is formed in this portion, if the surrounding bits are magnetized in the same direction, the force that the magnetization is directed to the opposite direction increases due to the demagnetizing field, and the stability is lowered. On the other hand, in Patent Document 1, the composition ratio of the ferromagnetic material in the outer peripheral portion that is close to the adjacent track is made larger than that in the central portion so that the magnetization reversal is difficult. A method for preventing magnetization reversal (side erase) due to leaking magnetic flux has been proposed. However, if the magnetic flux density at the outer peripheral part is increased, the magnetic moment at the outer peripheral part becomes larger than that at the central part, and when viewed from the reproducing element, a strong magnetic flux is detected from the outer peripheral part. The signal (crosstalk) becomes large. These problems become more apparent as the diameter W1 of the recording bit is increased.

  The present invention provides a bit pattern medium that can be recorded / reproduced using a head having an element width wider than the width W2 between bits of adjacent tracks, and a related technique.

A perpendicular magnetic recording medium according to the present invention is a magnetic recording medium in which a perpendicular magnetic recording layer is formed on a flat nonmagnetic substrate. The perpendicular magnetic recording layer is separated in units of recording bits, and a sequence of recording bits is adjacent to each other. The recording bits are arranged concentrically so as to be shifted by an interval of 1/2 bit, and the recording bits have a laminated structure in which the second magnetic layer is laminated on the first magnetic layer, A taper shape having an upper surface area smaller than the area, the outermost peripheral portion of the recording bit is formed of the first magnetic layer, the central portion includes the first magnetic layer and the second magnetic layer, and the outermost peripheral portion; An inversion control region is provided between the central portions, the saturation magnetic flux density of the second magnetic layer is Msa, the perpendicular magnetic anisotropy is Kua, the saturation magnetic flux density of the first magnetic layer is Msb, and the perpendicular magnetic anisotropy. Is Kub, the saturation magnetic flux density of the inversion control region is Msc, and the perpendicular magnetic anisotropy is Ku. When a, it satisfies the following relationship.
Msa> Msb, Kua <Kub, Msc <Msa, Kuc <Kua

  The present invention also provides a magnetic recording layer separated in units of recording bits, wherein the recording bit sequence is arranged concentrically with an interval of 1/2 bit from the adjacent sequence. A method for manufacturing a recording medium is provided. That is, the manufacturing method of the present invention includes a step of forming a first magnetic layer having a first saturation magnetic flux density and a first perpendicular magnetic anisotropy on a flat nonmagnetic substrate, Forming a second magnetic layer having a second saturation magnetic flux density larger than the first saturation magnetic flux density and a second perpendicular magnetic anisotropy smaller than the first perpendicular magnetic anisotropy; Forming a bit pattern mask having a groove width between bits in the down-track direction narrower than the groove width of the other portion on the magnetic layer, and implanting ions into the second magnetic layer using the mask, The second magnetic layer is etched by the step of forming an ion implantation part partially entering below and the etching with a large side etching effect, and the ion implantation part formed in the part other than between the bits in the down track direction is removed. Process and straightness By gastric etching, and a step of etching the second magnetic layer leaving a portion located below the mask of ion implantation portion formed between the down-track direction of the bit.

Furthermore, the present invention has a magnetic recording layer separated in units of recording bits, and a sequence of recording bits is arranged concentrically with an interval of 1/2 bit from an adjacent column. Has a laminated structure in which the second magnetic layer is laminated on the first magnetic layer, has a tapered shape in which the area of the upper surface is smaller than the area of the bottom surface, and the outermost peripheral part of the recording bit is the first outermost part. The magnetic layer is composed of a first magnetic layer and a second magnetic layer at the center, and two inversion control regions are provided between the outermost peripheral portion and the central portion on the inflow side and the outflow side of the magnetic head or magnetically. Provided at one location on the outflow side of the head, the saturation magnetic flux density of the second magnetic layer is Msa, the perpendicular magnetic anisotropy is Kua, the saturation magnetic flux density of the first magnetic layer is Msb, and the perpendicular magnetic anisotropy Is Kub, the saturation magnetic flux density of the inversion control region is Msc, and the perpendicular magnetic anisotropy is Kuc. Relationship Msa> Msb, Kua <Kub, Msc <Msa, Kuc <Kua
A method for recording / reproducing information using a magnetic head having an element width straddling two recording bit strings arranged concentrically with respect to a perpendicular magnetic recording medium satisfying the above condition is provided.

  When recording, the magnetic head is positioned at the center of the two recording bit strings, and when the magnetic head passes through the inversion control area on the recording bit outflow side, recording is performed on the recording bits. Recording is alternately performed on the bit string.

  Further, during reproduction, the magnetic head is positioned at the center of the two recording bit strings, and when the magnetic head passes the central portion of the recording bit, the information of the recording bit is read so that two recording bit strings are recorded. Are alternately read.

  The bit pattern medium of the present invention has excellent thermal stability and is less affected by leakage magnetic flux from the adjacent bit. At the time of recording, the magnetic flux density required for reversal is small, and reversal due to leakage magnetic flux that records the adjacent track is suppressed. During playback, the output from the bit center is high and the noise from adjacent bits is small.

  Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

FIG. 4 is a diagram showing the arrangement of recording bits and the recording / reproducing head width that can be used. FIG. 3 is a diagram showing an example of a reproduction area, a heat stable area, and an inversion control area in a recording bit provided in a perpendicular magnetic recording medium according to the present invention. It is the figure which showed the example of the surface structure and cross-sectional structure of a recording bit. It is process drawing which shows the example of the manufacturing method of the perpendicular magnetic recording medium by this invention. It is a plane schematic diagram of the perpendicular magnetic recording medium in the middle of manufacture. It is the plane schematic diagram and cross-sectional schematic diagram of the recording bit formed in the sample medium. It is the schematic which showed an example of the process of performing ion implantation. It is the figure which showed the relationship between recording / reproducing head width and an error rate about four types of sample media. It is the figure which showed the reproducing signal and the input signal to a recording head in the case of recording / reproducing two rows of recording bits alternately.

Hereinafter, embodiments of the present invention will be described.
In the present invention, the recording bits are circular or elliptical when viewed from the medium surface, and are arranged concentrically. The center positions of the recording bits in the adjacent column in the cross track direction are shifted in the down track direction by a length corresponding to ½ of the recording bit interval in the down track direction.

  FIG. 2 is a schematic diagram viewed from the surface of the recording bit group, and FIG. 3 is a three-side view of one recording bit. The recording bit has three types of areas when viewed from the surface of the medium, and the magnetic characteristics of the recording bits are different in the three types of areas. The central portion of the recording bit is a reproduction area 21 where the output is most output during reproduction, and has a saturation magnetic flux density Ms1, a perpendicular magnetic anisotropy Ku1 and a film thickness t1 as an average in the film thickness direction of the recording layer. On the other hand, the outer peripheral portion is a heat stable region 22, which is effective in improving the heat stability, and is a region where the magnetic influence from adjacent bits is small and the reproduction output is also small. The heat stable region 22 has a saturation magnetic flux density Ms2, a perpendicular magnetic anisotropy Ku2 and a film thickness t2 as an average in the film thickness direction of the recording layer. The reversal control region 23 is a region that creates a trigger for magnetization reversal in response to a leakage magnetic field from the recording element. The inversion control region 23 is provided at all or part of the boundary between the reproduction region 21 at the center and the heat stable region 22 at the outer periphery, and has a region of saturation magnetic flux density Ms3 and perpendicular magnetic anisotropy Ku3 in the vicinity of the surface layer. , The film thickness from the bottom surface of the recording bit is t3. The magnetic characteristics of the reproduction region 21, the heat stable region 22, and the inversion control region 23 have a relationship of Ms1> Ms2 and Ms1> Ms3, Ku2> Ku1> Ku3. Further, the heat stable region 22 is a region that forms an inclined surface of the bit side wall so that the film thickness t2 satisfies t1> t2. The inversion control region 23 is located in the vicinity of the boundary between the slope where the film thickness t3 is t1 ≧ t3 and the flat central portion.

  When the coercive forces of the reproduction area 21, the heat stable area 22, and the inversion control area 23 are Hc1, Hc2, and Hc3, respectively, when the areas are cut out from the recording bits and the magnetic characteristics are evaluated, the relationship is Hc2> Hc1> Hc3. . By controlling the magnetic characteristics of the recording bit in this way, the leakage magnetic flux density is maximized at the center and the signal intensity is also increased. On the other hand, the outer peripheral part contributes to the thermal stability of the recording bit, but the leakage magnetic flux is small. For this reason, since the correlation between adjacent bits can be reduced particularly when the guard band is narrow, a recording bit having a high filling rate can be formed. The reversal control region 23 makes the magnetic anisotropy of the surface layer portion where the magnetic field intensity from the recording head is large smaller than the central portion, and makes this portion easier to reverse by the external magnetic field than other regions. Further, by reducing only the perpendicular magnetic anisotropy Ku of the reversal control region 23 so that magnetization can be reversed by the leakage flux of the recording element, the Ku of the entire recording bit can be kept large, and the thermal stability of the recording bit can be improved. It can be improved.

  Furthermore, as shown in FIG. 2, by not providing the inversion control area 23 on the outer periphery of the bit, the influence of the leakage magnetic flux when recording the adjacent bit can be further reduced. More specifically, the inversion control region 23 is preferably provided at the boundary in the track direction between the central portion of the reproduction region 21 and the outer peripheral portion of the heat stable region 22 and not provided in the cross track direction. That is, the inversion control region 23 is formed so as to straddle the vicinity of the bit center line perpendicular to the cross track direction, and is not provided on the bit center line perpendicular to the track direction. Thus, the inversion control area 23 can be limited to a position away from the adjacent track, and the inversion control area 23 of the adjacent track can be moved away from the recording element when recording the track. Therefore, as shown in FIG. 2, it is possible to use a recording element having a wide width of about W5 that does not straddle the bit inversion control region 23 of the adjacent track. In this way, when the reversal control region 23 is limited to the vicinity of the bit center in the cross track direction, the reversal control regions 23 are formed at two locations, the side where the magnetic head flows and the side where the magnetic head flows. However, the bit is recorded by the leakage magnetic flux when the recording head flows out, and does not depend on the direction of the leakage magnetic flux from the previous head. That is, since only the reversal control area on the head outflow side is used for recording, the reversal control area may be on both the inflow and outflow sides or only on the outflow side.

  In the magnetic recording medium of the present invention, each recording bit has a region showing three kinds of magnetic characteristics when cut in the film thickness direction. The reproduction area 21, which is the reproduction area at the center, can increase the reproduction signal output due to the large saturation magnetic flux density and the thick film thickness. By increasing the output at the center of the bit, noise caused by magnetic flux leakage from the outer periphery of the bit can be reduced. Since the output at the center of the bit is increased and the noise from the bit of the adjacent track is reduced, a wide reproducing head can be used. The thermal stability region 22 in the outer peripheral portion contributes to the thermal stability of the bit due to high perpendicular magnetic anisotropy. In addition, since the outer peripheral part has a large interaction with the adjacent bit, the influence of the leakage magnetic field between the adjacent bits can be reduced by high perpendicular magnetic anisotropy, saturation magnetic flux density smaller than the central part and thin film thickness. it can. In addition, since the gap between the adjacent recording bits can be narrowed by forming the heat stable region 22, and the bit volume can be increased with the same integration density, an improvement in heat stability is achieved. Further, the reversal control area 23 can reduce the perpendicular magnetic anisotropy of the surface layer portion so that the recording bit is reversed by the leakage magnetic field from the recording head applied to the reversal control area 23. By providing the reversal control region 23, the perpendicular magnetic anisotropy can be increased so that the reproduction region 21 and the heat stable region 22 cannot be reversed by the leakage magnetic field of the recording head, and the thermal stability is improved. Further, even when the recording head is on the heat stable area 22 when recording adjacent tracks, side erasing is not required unless the recording head is on the inversion control area 23, so that a wider recording head can be used.

  The condition of the position where the recording head should be at the time of recording is that a part of the recording head is on the inversion control area 23 on the head outflow side of the bit to be recorded and not on the inversion control area 23 of the adjacent bit. . The condition of the position where the reproducing head should be at the time of reproduction is that it is on the reproducing area 21 in the center of the recording bit and not on the reproducing area 21 of the adjacent bit. That is, recording / reproduction can be performed even if the recording head and the reproducing head interfere with the heat stable region 22 of the adjacent bit. Also, since the recording position and playback position are part of the bit, it looks as if the bit has become smaller from the head. Therefore, the head alignment accuracy may be low. Even if the position of the recording bit actually created on the medium deviates from the design value, it is less affected by recording / reproducing of the adjacent bit, and the risk of recording / reproducing the adjacent bit is reduced even if the head position is deviated. Reliability is improved.

  Furthermore, since the recordable position of the recording bit or the reproduction sensitivity distribution can be limited to the recording bit inversion control area 23 or the reproduction area 21, respectively, two columns of bits shifted in phase by 1/2 bit width are alternately recorded or reproduced. can do. The center of these two rows of bits is the track center. When recording is performed by controlling the position of a recording head having a width corresponding to two columns of bits with the center of the track as a center, two columns of bits can be recorded alternately. Further, when the reproducing head having a width corresponding to two columns of bits is subjected to position control around the track and reproduced, the bits of the two columns can be alternately reproduced. This makes it possible to accumulate twice as many bits in the cross track direction even with the same head width.

  As described above, in the bit pattern medium of the present invention, the reproduction output is converged at the center of the bit, and the region where magnetization can be reversed by the magnetic flux from the recording element is limited to a part. Is loose. For this reason, it is possible to alternately record and reproduce two rows of recording bits arranged in the down track direction as one track, and a head having a wider recording element width and reproducing element width can be used. A bit pattern medium capable of higher integration can be provided.

  In forming the bit having the magnetic characteristics, a magnetic film having different magnetic characteristics at least in the upper part and the lower part is formed as a recording layer on a flat nonmagnetic substrate. Here, the upper part is defined as the high power layer and the lower part is defined as the heat stable layer. The material is set so that Msa> Msb and Kua <Kub are established between the saturation magnetic flux density Msa and perpendicular magnetic anisotropy Kua of the high output layer and the saturation magnetic flux density Msb and perpendicular magnetic anisotropy Kub of the heat stable layer. select. A method of manufacturing a magnetic recording medium according to an aspect of the present invention includes a step of forming a recording layer using at least two magnetic films on a flat nonmagnetic substrate, and a step of forming a bit pattern mask on the recording layer. And a step of implanting ions into the recording layer using a bit pattern mask, and a step of etching the recording layer by ion beam etching with at least two kinds of acceleration voltages or beam angles.

  The bit outer periphery which is the heat stable region 22 can satisfy Ms1> Ms2, t1> t2 and Ku2> Ku1 by physically etching the high output layer. Further, the inversion control region 23 is near the boundary between the bit outer periphery and the center, and the saturation magnetic flux density and the perpendicular magnetic anisotropy are reduced by injecting nonmagnetic atoms into the high output layer, so that Ms3 <Ms1 and Ku3 < It can be formed so as to satisfy Ku1.

[Perpendicular magnetic recording medium]
A perpendicular magnetic recording medium has at least a recording layer on a flat nonmagnetic substrate. The recording layer is composed of two or more magnetic layers exhibiting different magnetic characteristics, and includes a layer having a saturation magnetic flux density Msa and a perpendicular magnetic anisotropy Kua as a high output layer in the upper part, and a heat stable layer in the lower part. A layer having a saturation magnetic flux density Msb and perpendicular magnetic anisotropy Kub. Here, Msa> Msb, Kua <Kub. By doing so, the leakage flux per unit volume from the upper high-power layer is larger than the leakage flux from the lower thermal stabilization layer, and the effect of increasing the signal strength is high. On the other hand, the lower heat-stable layer has higher perpendicular magnetic anisotropy and lower saturation magnetic flux density than the upper high-power layer.

  As long as the magnetic recording layer exhibits the above properties, a perpendicular magnetization film such as a CoCrPt alloy, a CoPt alloy, a CoPd artificial lattice film, a CoPt artificial lattice film, or an FePt alloy can be used. As described above, in order to control the magnetic properties of the high-power layer and the heat-stable layer, for example, to increase the saturation magnetic flux density of the high-power layer, the composition ratio of the ferromagnetic elements Co and / or Fe of the high-power layer Is larger than that of the heat-stable layer, and in the case of an artificial lattice film, the film thickness ratio of Co or Fe is preferably larger than that of the heat-stable layer. On the other hand, in order to increase the perpendicular magnetic anisotropy of the thermally stable layer, the composition ratio of Pt and / or Pd is made larger than that of the high output layer, and in the case of an artificial lattice film, the film thickness ratio of Pt or Pd is increased. It should be larger. There is also a method for improving crystal orientation by annealing or the like. In addition, the magnetic characteristics can be changed by adding nonmagnetic elements such as C, Al, Cr, B, N, Ta, Si, and Ru. Each of the high output layer and the heat stable layer may be a single layer film or a multilayer film. Even if each of the high-power layer and the heat-stable layer has a multilayer structure having a plurality of magnetic characteristics, the average magnetic characteristics of the high-power layer and the heat-stable layer need only exhibit the above-described properties.

  The recording bits may be circular or elliptical when viewed from the medium surface, and may be arranged concentrically in the track direction as shown in FIG. The bits in the adjacent column in the cross track direction may be arranged so as to be shifted by 1/2 the bit interval in the down track direction. By doing so, the bits are arranged concentrically and the structure is close to the closest structure, and the bit density can be increased. The recording bits may be divided by a servo area or the like in both the down track direction and the cross track direction to form a block by a plurality of recording bits.

  The shape of each recording bit can be a tapered shape with a top surface area smaller than the bottom surface area as shown in FIG. 3, typically a truncated cone shape. The cross-sectional shape of one recording bit has a trapezoidal shape with side walls inclined. The central portion of the bit with the flat top surface of the truncated cone becomes the reproducing region 21 having the largest film thickness and the large saturation magnetic flux density. The outer peripheral portion of the recording bit corresponding to the inclined surface of the truncated cone has a structure in which the high-power layer is cut and the proportion of the heat-stable layer is increased or only the heat-stable layer is formed, and the heat-stable region 22 is formed. Near the edge of the top surface of the frustoconical recording bit, a nonmagnetic metal is ion-implanted into the high-power layer, for example, to reduce the composition ratio of the ferromagnetic element, so that the perpendicular magnetic field is different from the center of the recording bit. A region where the directionality and the saturation magnetic flux density are small is formed. In this way, the inversion control region 23 is formed inside the heat stable region 22 as shown in FIG. Further, as shown in FIG. 3, it is preferable to form the reversal control region 23 only at two locations in the track direction between the reproduction region 21 and the heat stable region 22 because the allowable amount of positional deviation of the recording head is increased. Further, as shown in FIG. 6B, the reversal control region 23 may be formed only at one position on the side where the head flows out in the track direction.

[Method of manufacturing perpendicular magnetic recording medium]
The perpendicular magnetic recording medium of the present invention can be manufactured by the following method. 4 (a) to 4 (g) show a cross-sectional shape of the manufacturing process of the recording medium, and are schematic views corresponding to the cross section A-B-C in FIG.

  First, as shown in FIG. 4A, a heat stable layer 131 and a high output layer 132 constituting at least a recording layer are formed on the nonmagnetic substrate 10. At this time, an adhesion layer, a soft magnetic underlayer 11, and an orientation control layer may be formed between the nonmagnetic substrate 10 and the heat stable layer 131, and protective layers and hard mask layers 141, 142 are formed on the high output layer 132. It may be formed. Next, as shown in FIG. 4B, a resist pattern is formed on the surface on which the multilayer film is formed using an imprint apparatus or the like. Next, as shown in FIG. 4C, when there is a hard mask layer, the imprint resist pattern is transferred to the hard mask layer using a reactive ion etching apparatus or the like.

  Next, as shown in FIG. 4D, a nonmagnetic element such as C, Al, Cr, B, N, Ta, Si, and Ru is ion-implanted using an imprint resist pattern or a hard mask pattern as a mask. Used to inject into the high power layer under the opening of the mask. Since ions accelerated to several keV are used for ion implantation, not only the high-power layer in a region without a mask but also a part of ions spread to a high-power layer in a masked portion. As a result, as shown in the plan view of FIG. 5A, the boundary of the high-power layer not shown in FIG.

  Next, the ion-implanted high-power layer is removed by etching using an ion milling device. When forming the recording bit shown in FIG. 3 in which the inversion control layer 23 is provided only in the track direction, as shown in FIG. 2, the distance W3 between adjacent bits in the track direction is smaller than the distance W4 between adjacent bits in the cross track direction. By doing (W4> W3), the opening width of the mask in the track direction is made narrower than the opening width of other portions. As shown in FIG. 4 (e), when the straightness of milling ions is controlled to increase the components of ions incident obliquely on the surface of the magnetic recording medium, the side etching effect increases, and a mask is formed in a portion with a wide opening width. The side walls of the mask are etched to retract the mask, and the ion-implanted region formed by diffusion under the original mask is also removed by etching. However, the ion-implanted region between adjacent bits in the track direction is not etched because it is difficult for ions with low rectilinearity to enter because the mask opening groove is narrow. When viewed from the surface, it becomes as shown in FIG. 5B, and the portion having the ion-implanted layer remaining in the track direction of the recording bit becomes the inversion control region 23.

  Further, as shown in FIG. 7, when the ion beam 71 is offset from the substrate and incident only to a part of the fan-shaped portion of the disk 73 through the slit 72 from an oblique direction, and the disk 73 is rotated, Etching can be performed with the ion beam 71 obliquely incident in the track direction on the entire surface of the disk. By this method, side etching of one of the side walls in the track direction can be suppressed, and only the ion implantation portion in the down track direction on the outflow side of the magnetic head can be left. Using this method, the recording bit structure shown in FIG. 6B can be produced. When the inversion control region 23 shown in FIG. 6A is formed concentrically between the reproduction region 21 and the heat stable region 22, this step can be omitted.

  Next, as shown in FIG. 4 (f), the ion milling device is used to irradiate ions that are more straight ahead than when the ion-implanted portion is etched, and the high-power layer and the heat under the opening of the mask. The stable layer is etched to form a groove. At this time, a taper-shaped groove whose width becomes narrower as the groove is deeper is formed, and the recording bit has a truncated cone shape.

  As described above, it is possible to form a recording bit in which the three types of magnetic characteristics of the reproduction area 21, the heat stable area 22, and the inversion control area 23 are distributed as shown in FIG. Finally, as shown in FIG. 4G, a backfill layer 161 made of a nonmagnetic material such as carbon, Si, or Cr may be formed in the groove formed between the recording bits to improve the surface flatness. In order to fly the head as a perpendicular magnetic recording medium, the mask or backfill layer is removed by etching or the like until the surface of the recording layer in the reproducing area 21 is exposed, and the surface is flattened by etching. And the lubricating layer 163 may be formed.

[Recording / reproducing method of perpendicular magnetic recording medium]
In the perpendicular magnetic recording medium of the present invention, the recording and reproducing positions of the recording bits are limited to the inversion control area 23 and the reproducing area 21 in the center of the bits in the cross track direction, respectively. Even if it is on the bit of the adjacent track, if it is on the heat stable region 22 on the outer peripheral portion, there is no problem in recording and reproduction. Therefore, it is possible to use a magnetic head having a recording element and a reproducing element that are wider in the cross track direction than the width that the bit of the adjacent track of the recording bit does not cover. Since a recording element and reproducing element wider than the width of one recording bit can be used, a recording element that generates a larger magnetic field and a highly sensitive reproducing element can be used. It is possible to use a magnetic recording medium on which a recording bit having a large directivity and excellent thermal stability is formed. Thereby, bits can be formed with a higher recording density. In addition, sufficient reproduction output and high SNR can be obtained.

  Furthermore, since the perpendicular magnetic recording medium of the present invention can limit the recording and reproducing position of the recording bit to a part of the bit, the two columns arranged in the cross track direction are regarded as one track, and adjacent columns are recorded. Recording and reproduction can be performed particularly stably by a method of alternately recording and reproducing bits arranged with a ½ bit interval width in the down-track direction. In this case, the width of the recording element and the reproducing element is a width across both bits of the two columns, and recording / reproducing is performed by aligning the center of the element with the center of the bit group of two columns. The element always flies over both bits of the two rows, but from the head, the reproduction region 21 at the reproduction position appears alternately, and the reproduction element obtains the average signal of the sensing part. Since it appears to be arranged at ½ bit intervals at the center of a track composed of two rows, the same system as that for recording / reproducing one row of bits as one track can be used. On the other hand, with respect to the recording position, in the case of the structure shown in FIG. 2, there are two inversion control areas 23 in one bit, and the inversion control area 23 on the outflow side of the magnetic head is the most adjacent bit of the adjacent track. The position in the down track direction is very close to the inversion control region 23 on the magnetic head inflow side. For this reason, two bits are simultaneously reversed by the leakage magnetic field from the recording element, but recording is performed by the leakage magnetic field from the recording element when the recording element passes through the reversal control region 23 on the side where the head finally flows out. The magnetization direction of the bit is determined. For this reason, it is preferable to use a method of continuously recording a group of recording bits (a so-called sector) on one track, instead of inverting one specific recording bit as in a general magnetic recording apparatus.

[Example]
Hereinafter, the embodiment will be specifically described.
A bit pattern type perpendicular magnetic recording medium was manufactured by the manufacturing method shown in FIGS. 4 (a) to 4 (g). 4 (a) to 4 (g) are cross-sectional views corresponding to the cross section A-B-C in FIG. It should be noted that matters described in the mode for carrying out the invention and not described in the present embodiment can be applied to the present embodiment.

As shown in FIG. 4A, a glass substrate having a diameter of 65 mm is used as the nonmagnetic substrate 10, and a soft magnetic underlayer 11, an intermediate layer 12, a heat stable layer 131, a high output layer 132, a first output layer are formed using a sputtering apparatus. A hard mask 141 and a second hard mask 142 were formed in order. The intermediate layer is 9 nm thick Ru, the heat stable layer 131 is 5 nm thick CoCr ₁₅ Pt ₁₅ alloy, the high power layer 132 is 3 nm thick CoCr ₁₈ Pt ₁₀ alloy, and the first hard mask 141 is a film. thickness 10nm of CN _x, the second hard mask 142 using SiN _x having a thickness of 2 nm. Next, as shown in FIG. 4B, an imprint resist pattern 15 was formed using an imprint apparatus. The total resist thickness was 30 nm, the bit pattern height was 25 nm, and the resist residue was 5 nm.

Next, as shown in FIG. 4C, the resist residue in the groove between the bit patterns is removed by reactive ion etching using oxygen gas by a reactive ion etching apparatus, and reactive using CF ₄ gas. The second hard mask 142 in the groove was removed by ion etching, and the first hard mask 141 in the groove was removed by reactive ion etching using CO ₂ gas. At this time, the remaining imprint resist was also removed, and the bit pattern was transferred to the first and second hard masks.

Next, as shown in FIG. 4D, nitrogen ions were implanted into the high-power layer 132 in the 5 × 10 ¹⁴ ions / cm ² groove using an ion implantation apparatus at an acceleration voltage of 3 keV. Thus, the ion implantation part 133 was formed in a part of the high output layer 132. The ion implantation part 133 is formed so that a part thereof also enters the lower region of the hard mask. Next, as shown in FIG. 4E, Ar ions were irradiated with an acceleration voltage of 500 V using an ion beam etching apparatus, and the high-power layer 132 in the groove was etched. At this time, the component of the ion beam incident obliquely with respect to the surface of the magnetic recording medium is increased, and etching with a large side etching effect is performed. As a result, it is difficult for an ion beam to enter the narrow groove of the A-B cross section, and the groove is not formed in the high output layer. On the other hand, an ion beam entered a groove having a wide B-C cross section, and a groove was formed in the high output layer while the side wall of the hard mask was retracted by side etching. The side walls of the grooves of the hard mask and the high power layer were inclined at about 50 degrees. Next, as shown in FIG. 4F, Ar ions were irradiated at an acceleration voltage of 200 V to remove the high-power layer 132 and the heat stable layer 131 in the groove. At this time, the rectilinearity of the ion beam is increased compared to the processing shown in FIG. In this process, both the narrow groove of the A-B cross section and the wide groove of the B-C cross section enter the ion beam, and both grooves are etched, and the side wall of the groove formed in this process shows an inclination of about 75 degrees. It was. Further, the hard mask was also etched during the two ion beam etchings, and only a part of the first hard mask 141 remained on the high power layer 132. At this time, the ion implantation region adjacent to the narrow groove of the A-B cross section and located under the first hard mask 141 remains without being removed and becomes an inversion control region.

  Next, as shown in FIG. 4G, carbon is formed on the surface as the backfilling layer 161, and after the unevenness is flattened, the backfilling layer 161 is removed by dry etching until the high power layer surface is exposed, Carbon was formed as the protective layer 162, and the lubricating layer 163 was formed by dipping. The perpendicular magnetic recording medium thus manufactured is designated as Sample 1.

  The size of the recorded bit is as follows. The width W1 of the recording bit shown in FIGS. 1 and 2 is 12 nm, the width W2 in the cross-track direction not covered by the bit of the adjacent track is 14 nm, and the nearest adjacent bit in the track direction. The distance W3 was 13 mm, the distance W4 between the adjacent bits adjacent in the down track direction was 14 nm, and the distance W5 between adjacent sides of the reproduction area of the adjacent track was 21 nm.

  Next, after the ion implantation was performed by the same manufacturing method as that of Sample 1, ion beam etching was performed only at an acceleration voltage of 200 V without performing ion beam etching at an acceleration voltage of 500 V. Other manufacturing processes are performed in the same manner as in Sample 1, and perpendicular magnetic recording in which a reproduction region 21, a reversal control region 23, and a heat stable region 22 are formed concentrically from the central portion while leaving the reversal control region 23 on the cross track side. A medium was made. This is designated as sample 2. A schematic diagram of the recording bits of sample 2 is shown in FIG.

  Next, after the ion implantation is performed by the same manufacturing method as that of the sample 1, the etching is performed by tilting the ion beam with respect to the substrate surface, and the inversion control region 23 is set only on the magnetic head outflow side in the down track direction. The remaining sample 3 was produced. A schematic diagram of the recording bits of sample 3 is shown in FIG.

  Next, a perpendicular magnetic recording medium in which no ion implantation was performed and the reversal control region 23 did not exist was manufactured by the same manufacturing method as Sample 1. This is designated as sample 4. A schematic diagram of the recording bits of sample 4 is shown in FIG.

  Next, in a manufacturing method similar to that of sample 1, ion implantation is not performed, and etching of the groove portion is performed by Ar ion irradiation with an acceleration voltage of 150 V, so that the side walls of the high output layer and the heat stable layer in the groove portion are vertical. A magnetic recording medium was produced. This is designated as Sample 5. A schematic diagram of the recording bits of sample 5 is shown in FIG. All the recording bits of the sample 5 are made of the reproduction area 21, and there is no heat stable area 22 and inversion control area 23.

  Next, after performing ion implantation by the same manufacturing method as that of Sample 1, etching of the groove portion is performed by Ar ion irradiation with an acceleration voltage of 150 V, so that the side walls of the high output layer and the heat stable layer are perpendicular to each other. A recording medium was produced. This is designated as sample 6. The recording bit of sample 6 has an inversion control region 23 formed at the outermost peripheral portion of the bit, the central portion is a reproduction region 21, and does not have a heat stable region 22 for heat stabilization. A schematic diagram of the recording bits of sample 6 is shown in FIG.

Next, in the same manner as in sample 1, a 5 nm thick CoCr ₁₈ Pt ₁₀ alloy is used for the heat stable layer 131, and a 3 nm thick CoCr ₁₅ Pt ₁₅ alloy is used for the high output layer 132. A patterned medium having a recording layer configuration in which the high output layer 132 has a larger Ku and a smaller Ms than the heat stable layer 131 was produced. This is designated as Sample 7.

  Next, a manufacturing method similar to that of Sample 1 was used, in which Co (film thickness: 0.3 nm) and Pd (film thickness: 0.7 nm) were alternately stacked on the heat stable layer 131 to obtain a total film thickness of 5 nm. As the output layer, Co (film thickness: 0.4 nm) and Pd (film thickness: 0.6 nm) were alternately stacked to form a patterned medium using a total film thickness of 3 nm. This is designated as Sample 8.

Next, in the same manner as in Sample 1, a patterned medium was manufactured using a Co ₇₀ Pt ₃₀ alloy of 5 nm for the heat stable layer 131 and a Co ₈₀ Pt ₂₀ alloy of 3 nm for the high output layer. This is designated as Sample 9.

Next, an Fe ₅₀ Pt ₅₀ alloy film having a thickness of 5 nm is formed on the heat stable layer 131 by the same manufacturing method as Sample 1, annealed at 500 degrees Celsius, and then a Co film having a film thickness of 3 nm as a high output layer. A patterned medium on which an ₈₀ Pt ₂₀ alloy was formed was produced. This is designated as Sample 10.

  In order to examine the magnetic characteristics of Samples 1 to 10, magnetization measurement in the direction perpendicular to the substrate was performed using a sample vibration magnetometer. Table 1 shows the reversal start magnetic field Hn, the coercive force Hc, and the saturation magnetic field Hs. The ones without temperature are measured at room temperature.

  It can be seen that the sample 1 medium has lower coercive force and saturation magnetic field than the sample 4 medium, and can record even if the magnetic field of the recording head is small. In addition, the coercive force of the media of Samples 5 and 6 is small, but the saturation magnetic field is large and recording cannot be stably performed. On the other hand, the reversal start magnetic field shows that the media of samples 1 to 4 are negative and the bit can be kept stable, but the media of samples 5 and 6 are reversed when the applied magnetic field is returned to zero. This indicates that there is a bit to end. Sample 7 has the same shape as sample 1, but the heat-stable layer does not function sufficiently, so that it can be seen that the inversion start magnetic field is particularly small and the stability of the recording bit is low. In samples 8, 9, and 10, the saturation magnetic flux density at room temperature greatly exceeds 10 kOe. However, when the temperature is raised to 150 to 200 degrees, as shown in the table, the coercive force is about 5 kOe, the saturation magnetic flux density is about 8 kOe, and the inversion start magnetic field is 2 kOe or less. Indicated.

In order to examine the actual recording characteristics of each sample medium, AC recording (0101...) And DC recording (111111...) Were performed in accordance with the recording bit period using a recording element. The head used for the evaluation is a composite having a reproducing element (reproducing head) using a giant magnetoresistance effect with a shield gap length of 20 nm and a track width of 7 to 22 nm and a writing element (single pole recording head) with a track width of 7 to 22 nm. It is a magnetic head. Recording was performed by changing the applied current of the recording element under conditions of a peripheral speed of 10 m / s, a skew angle of 0 degree, and a magnetic spacing of about 1 nm, and a signal was read by the reproducing element to calculate an error rate. When the error rate was 10 ⁻⁴ or less, the minimum current applied to the recording element capable of normal recording was examined by assuming that the recording was normally performed. The results are shown in Table 2. Since the media of samples 8, 9, and 10 have a large coercive force at room temperature and cannot be recorded by a magnetic field from the head, recording was performed by heating the sample to 150 to 200 degrees Celsius.

  While the media of Samples 1 to 3 could perform both AC recording and DC recording at a current of about 20 mA, the media of Samples 4 and 5 could not perform AC recording unless a current of about 50 mA was applied. The medium of sample 4 was able to perform DC recording when a current of 55 mA was applied, but samples 5, 6, and 7 could not be recorded with a DC magnetic field regardless of the magnitude of the recording current, that is, the applied magnetic field. Samples 8, 9, and 10 required a slightly larger recording magnetic field because the coercive force and saturation magnetic flux density at the recording temperature were larger than those of sample 1, but both AC and DC magnetic fields could be recorded stably.

  From the above results, it can be seen that DC recording and AC recording can be performed correctly with a low current if there is a reproduction area 21 at the center of the bit, a heat stable area 22 at the outer periphery, and an inversion control area 23 between them. The fact that Samples 4 and 5 require a high current for AC recording indicates that the inversion control region 23 is effective in reducing the recording current. On the other hand, the fact that Samples 5 and 6 could not perform direct current recording indicates that the formation of the heat stable region 22 in the outermost peripheral portion is effective for arranging the bits in the same direction. Moreover, the result of the sample 6 also shows that it is not good to form the inversion control region 23 on the outer peripheral portion. The result of sample 7 shows that the effect of the heat stable region 22 is that the perpendicular magnetic anisotropy of the heat stable layer is larger than the anisotropy of the high power layer, and the saturation magnetic flux density of the heat stable layer is the saturation magnetic flux density of the high power layer. It shows that it is important to make it smaller. Samples 8, 9, and 10 are samples of a material exhibiting high anisotropy assuming that recording is performed by heating (thermally assisted recording), and stable recording is achieved by forming the heat stable region 22 and the inversion control region 23. It shows that you can.

  Next, AC recording was performed over multiple tracks by changing the width of the recording element and the reproducing element in the cross-track direction, and the error rate of the reproduced signal was examined. The results are shown in FIG. Samples 1 to 3 can be recorded and reproduced with almost no error even if a recording and reproducing element having a width of about 15 nm is used. In particular, Sample 1 and Sample 3 in which the inversion control region 23 was produced only in the track direction could be recorded and reproduced without error even when an element having a width of 17 nm was used. On the other hand, Sample 6 with the inversion control region 23 on the outer periphery of the recording bit shows that a wide recording element is inverted up to the bit of the adjacent track and has a high error rate, and a wide element cannot be used. Yes. In addition, the same results as Sample 1 were obtained for Samples 8 to 10. Samples 4 and 5 could not be evaluated because the error rate was drastically decreased due to a short recording magnetic field with a narrow head. In addition, sample 7 was affected by recording on the adjacent track as in sample 6, and the error rate decreased.

  This result shows that when the structure of Samples 1, 8, 9, 10 and Sample 3, that is, the inversion control area 23 is not in the cross track direction but only in the down track direction, the bit caused by the recording of the adjacent track is inverted. This indicates that the recording element with a larger width can be used.

  Next, using a magnetic head having a width of 25 nm between the recording element and the reproducing element, recording / reproduction was attempted using two bit strings in the cross-track direction as one track as shown in FIG. Samples 8, 9, and 10 were heated at the same temperature as in the recording / reproducing experiment. The center of the two bit strings is set as the track center, and the position of the magnetic head is controlled at the track center. This tracking control can be realized using existing technology. At the time of recording, as shown in FIG. 9, the upper row and lower row bits are alternately recorded so that the magnetic field for recording is applied when the magnetic head comes to the inversion control region 23 on the outflow side. A recording signal was generated as follows. At the time of reproduction, the total reproduction signal is detected as shown in FIG. 9, but when the reproduction element comes to the center of the upper and lower row recording bits, the signal is alternately input to the reproduction element. The reproduced signals from the bits in the column are separated as shown in the figure. In actual recording / reproduction, it is not necessary to consider which column the bit is in, and recording / reproduction can be performed by considering two columns of bits as one track. Therefore, in order to verify whether the two rows of bits can be correctly recorded as one track, AC recording was performed and the error error rate was calculated. The results are shown in Table 3.

  In samples 1 and 3, since the position of the inversion control region 23 and the magnetic field from the recording element are well synchronized, almost no error occurs when recording / reproduction is performed with an appropriate recording current. On the other hand, since the reversal control area 23 is entirely around the reproduction area 21 in the sample 2, the magnetization reversal can be caused by the magnetic field applied to record the adjacent column. For this reason, it is considered that the error rate increased because a recording error occurred when the head was slightly displaced. Similarly, when the recording current is increased to 60 mA and the magnetization is reversed by applying a magnetic field to the reproducing area 21, the recording error occurs because the recording head is slightly displaced. The rate has increased. Samples 4, 5, and 7 do not have the reversal control area 23, and sample 6 has the reversal control area 23 over the entire outer periphery, so that the recording position cannot be properly controlled, and two rows can be recorded and reproduced simultaneously. Was difficult. Unlike the samples 1 and 3, the inversion control area is not provided in the cross track direction, but is provided between the reproduction area and the heat stable area in the down track direction, so that the position where each bit can be recorded can be reduced. As a result, the margin for controlling the position of the recording head can be increased, which indicates that two rows of bits can be recorded and reproduced alternately. Samples 8, 9, and 10 cannot reverse the reversal control region 23 when the recording current is 30 mA. Therefore, when the measurement was performed with the currents listed in the table, the same error rate as that of Sample 1 was obtained. On the other hand, since the playback area is not easily reversed even at a recording current of 60 mA, the error rate is smaller than that of Sample 1. This shows that this method is also effective for the heat-assisted recording method. As a result of the above examination, it was found that the medium having the bit structure shown in Samples 1, 8, 9, 10 or 3 is suitable for recording and reproduction with two bit strings in the cross track direction as one track.

10 Nonmagnetic Substrate 11 Soft Magnetic Underlayer 12 Intermediate Layer 13 Recording Layer 131 Thermal Stabilization Layer 132 High Output Layer 133 Ion Implantation Section 14 Hard Mask Layer 141 First Hard Mask Layer 142 Second Hard Mask Layer 15 Imprint Resist 161 Backfill Packing layer 162 Protective layer 163 Lubrication layer 21 Reproduction region 22 Thermal stability region 23 Inversion control region

Claims (8)

In a magnetic recording medium in which a perpendicular magnetic recording layer is formed on a flat nonmagnetic substrate,
The perpendicular magnetic recording layer is separated in units of recording bits, and the recording bit columns are arranged concentrically with an interval of ½ bit from the adjacent column,
The recording bit has a laminated structure in which a second magnetic layer is laminated on a first magnetic layer, has a tapered shape in which the area of the upper surface is smaller than the area of the bottom surface, and the outermost peripheral portion of the recording bit Is composed of the first magnetic layer, the central portion includes the first magnetic layer and the second magnetic layer, and an inversion control region is provided between the outermost peripheral portion and the central portion,
The saturation magnetic flux density of the second magnetic layer is Msa, the perpendicular magnetic anisotropy is Kua, the saturation magnetic flux density of the first magnetic layer is Msb, the perpendicular magnetic anisotropy is Kub, and the inversion control region is saturated. A perpendicular magnetic recording medium characterized by satisfying the following relationship when the magnetic flux density is Msc and the perpendicular magnetic anisotropy is Kuc.
Msa> Msb, Kua <Kub, Msc <Msa, Kuc <Kua   2. The perpendicular magnetic recording medium according to claim 1, wherein the inversion control regions are provided at two locations on the inflow side and the outflow side of the magnetic head.   2. The perpendicular magnetic recording medium according to claim 1, wherein the inversion control region is at one place on the outflow side of the magnetic head.   4. The perpendicular magnetic recording medium according to claim 1, wherein the second magnetic layer has a larger total composition ratio of Co and Fe than the first magnetic layer. Medium.   4. The perpendicular magnetic recording medium according to claim 1, wherein the inversion control region in the second magnetic layer has a total composition ratio of Co and Fe from a central portion of the second magnetic layer. A perpendicular magnetic recording medium characterized by a small amount. In a method of manufacturing a perpendicular magnetic recording medium having a magnetic recording layer separated in units of recording bits, wherein the recording bit columns are arranged concentrically at a distance of 1/2 bit from the adjacent column ,
Forming a first magnetic layer having a first saturation magnetic flux density and a first perpendicular magnetic anisotropy on a flat nonmagnetic substrate;
A second magnetism having a second saturation magnetic flux density larger than the first saturation magnetic flux density and a second perpendicular magnetic anisotropy smaller than the first perpendicular magnetic anisotropy on the first magnetic layer. Forming a layer;
Forming a bit pattern mask on the second magnetic layer in which the groove width between bits in the track direction is narrower than the groove width of other portions;
Ion-implanting into the second magnetic layer using the mask, and forming an ion-implanted portion that partially enters under the mask;
Etching the second magnetic layer by etching having a large side etching effect, and removing an ion implantation portion formed in a portion other than between the bits in the track direction;
Etching the second magnetic layer by leaving a portion located below the mask among the ion implanted portions formed between the bits in the track direction by etching with good straightness. A method for manufacturing a perpendicular magnetic recording medium. A magnetic head is provided on a perpendicular magnetic recording medium having a magnetic recording layer separated in units of recording bits and in which the recording bit columns are arranged concentrically with an interval of 1/2 bit from the adjacent column. In the magnetic recording method for recording,
The recording bit has a laminated structure in which a second magnetic layer is laminated on a first magnetic layer, has a tapered shape in which the area of the upper surface is smaller than the area of the bottom surface, and the outermost peripheral portion of the recording bit Is composed of the first magnetic layer, the central portion has the first magnetic layer and the second magnetic layer, and the inversion control region is located between the outermost peripheral portion and the central portion on the inflow side of the magnetic head. The second magnetic layer has a saturation magnetic flux density Msa and perpendicular magnetic anisotropy Kua, and is provided at two locations on the outflow side or one on the outflow side of the magnetic head. When the saturation magnetic flux density is Msb, the perpendicular magnetic anisotropy is Kub, the saturation magnetic flux density of the inversion control region is Msc, and the perpendicular magnetic anisotropy is Kuc, the following relations Msa> Msb, Kua <Kub, Msc < Msa, Kuc <Kua
The filling,
Controlling the position of a magnetic head having an element width straddling the two recording bit strings arranged concentrically at the center of the two recording bit strings;
Recording the recording bit when the magnetic head passes through the inversion control area on the outflow side of the recording bit,
2. A magnetic recording method, wherein recording is performed alternately on the two recording bit strings. A magnetic recording layer separated in units of recording bits, wherein the recording bit sequence is recorded on a perpendicular magnetic recording medium arranged concentrically at a distance of 1/2 bit from the adjacent sequence; In a magnetic reproducing method for reproducing information stored by a magnetic head,
The recording bit has a laminated structure in which a second magnetic layer is laminated on a first magnetic layer, has a tapered shape in which the area of the upper surface is smaller than the area of the bottom surface, and the outermost peripheral portion of the recording bit Is composed of the first magnetic layer, the central portion has the first magnetic layer and the second magnetic layer, and the inversion control region is located between the outermost peripheral portion and the central portion on the inflow side of the magnetic head. The second magnetic layer has a saturation magnetic flux density Msa and perpendicular magnetic anisotropy Kua, and is provided at two locations on the outflow side or one on the outflow side of the magnetic head. When the saturation magnetic flux density is Msb, the perpendicular magnetic anisotropy is Kub, the saturation magnetic flux density of the inversion control region is Msc, and the perpendicular magnetic anisotropy is Kuc, the following relations Msa> Msb, Kua <Kub, Msc < Msa, Kuc <Kua
The filling,
Controlling the position of a magnetic head having an element width straddling the two recording bit strings arranged concentrically at the center of the two recording bit strings;
Reading the information of the recording bit when the magnetic head passes through the central portion of the recording bit,
A magnetic reproducing method, wherein the two recorded bit strings are alternately read.

Images