JP4425286B2 - Magnetic recording medium and recording / reproducing apparatus thereof - Google Patents

Description

  The present invention relates to a magnetic recording medium or the like that enables high-density recording, and more particularly to a magnetic recording medium or the like called patterned media in which fine particles of a single magnetic domain are arranged in an array.

  A large amount of information can be recorded on the magnetic recording medium. For this reason, magnetic recording media, particularly magnetic disks, continue to develop as one of the key devices that support the information society.

  As a recording method for a magnetic disk, two methods of a horizontal magnetic recording method and a perpendicular magnetic recording method are currently used. Both methods have a problem that noise increases as the recording density increases. In both recording methods, a polycrystalline ferromagnetic continuous film in which a ferromagnetic polycrystal is uniformly spread is used as a recording film. This polycrystalline ferromagnetic continuous film is composed of crystal grains whose size and shape change irregularly, and the boundary thereof has an irregular shape. This irregularity causes noise in the reproduced signal. Therefore, in order to reduce noise, it is necessary to make the ferromagnetic particles of the recording film fine so that a linear bit boundary can be obtained.

  By the way, when the bit interval is narrowed in order to improve the recording density of the recording film, the ferromagnetic particles become relatively large with respect to the bit interval. Therefore, if the bit interval is narrowed in order to increase the recording density, noise will increase. Thus, in order to improve the recording density without increasing the noise, it is necessary to further refine the ferromagnetic particles so that the bit boundaries do not become zigzag.

  However, if the ferromagnetic particles are made too fine, the recorded magnetization tends to disappear due to thermal fluctuation. For this reason, there is a limit to miniaturization of ferromagnetic particles. Therefore, when the recording density is improved, the limit of the inevitable increase in noise is eventually reached.

  Patterned media is expected as a new recording medium that solves this problem. This is the ultimate recording medium in which single-domain ferromagnetic particles separated by a non-ferromagnetic material are aligned and 1-bit information is recorded on each magnetic particle. FIG. 21 shows the concept of patterned media. Single-domain ferromagnetic particles 2 are aligned on a substrate 1, and a space between them is filled with a non-ferromagnetic material 3 to separate the ferromagnetic particles 2. One bit of information is recorded on each of the two separated ferromagnetic particles. Since the ferromagnetic particles 2 are separated by the non-ferromagnetic material 3, the boundary of the magnetic field is clear and no noise problem occurs.

  Patterned media can be formed by using a method such as electron beam lithography or photolithography to embed holes in a non-ferromagnetic material and embed the ferromagnetic material. Similarly, after patterning the ferromagnetic material, the non-magnetic material is embedded. In addition to the flattening method, there is a method of embedding a ferromagnetic material in fine holes (alumina nanoholes) opened in alumina formed by anodic oxidation (Patent Document 1).

  FIG. 22 is a plan view of the alumina nanohole patterned media formed by the final method. The upper part of FIG. 22 represents the whole image, and the lower part is an enlarged part thereof. As shown in FIG. 22, the alumina film 5 is formed on the substrate 1, and the ferromagnetic material 2 is embedded in the alumina nanoholes aligned on the concentric circles 4. Therefore, the track essential for the magnetic disk is pre-built.

  Such alumina nanoholes arranged on concentric circles are selectively formed in shallow grooves 6 formed by pressing a mold (mold material) on an aluminum thin film. FIG. 23 shows a manufacturing process of the alumina nanohole patterned media shown in FIG.

  The left side of FIG. 23 is an enlarged plan view of a part of the alumina nanohole patterned media. The right side is a view of the cross section taken along the line AA ′ as seen from the direction of the arrow.

  First, an aluminum film (hereinafter referred to as an Al film) 7 is deposited on the substrate 1 (FIG. 23A). Next, a mold 10 having concentric protrusions formed on the Al film 7 is pressed to form a shallow groove 8 (FIG. 23B). In the plan view shown on the left side of FIG. 23B, the mold 10 is omitted. Next, when the Al film 7 is anodized under predetermined conditions, alumina nanoholes 9 are selectively formed in the groove 8 at regular intervals (FIG. 23C). This interval (pitch) can be controlled in the range of 10 to several tens of nm depending on the conditions of anodization. Finally, the ferromagnet 2 is embedded in the alumina nanohole (FIG. 23D).

The depth of the alumina nanohole is about 100 nm and the diameter is about 10 nm. Therefore, a large shape magnetic anisotropy is imparted to the embedded ferromagnetic material. For this reason, a large coercive force is given to the ferromagnetic material 2 in the alumina nanohole 9. This large coercive force increases the thermal stability of the ferromagnetic body 2. As described above, the alumina nanohole / patterned media has an advantage of high thermal fluctuation resistance in addition to the advantages of high density and low noise. The easy axis of magnetization of the ferromagnetic material 2 in the alumina nanohole 9 is a direction perpendicular to the substrate 1.
JP 2005-305634 A

  As described above, concentric tracks are formed in advance in the patterned media. However, servo information such as track numbers and sector numbers must be written later. However, for patterned media, as described below, the method of writing servo information to the recording layer later, which has been used as a method of recording servo information on a hard magnetic disk, cannot be applied. .

  As a method of writing servo information to the recording layer, there is a method of writing a magnetic field generated by a magnetic head of a magnetic recording device to a magnetic film. However, when such a method is used for a large-capacity recording medium such as a perpendicular magnetic recording medium or a patterned medium, the writing time becomes enormous and inefficient. For this reason, a magnetic transfer method is generally used as a method for writing servo information on a large-capacity magnetic recording medium such as a perpendicular magnetic recording medium.

  FIG. 24 is a conceptual diagram illustrating the magnetic transfer method. First, a template 12 is prepared by replacing the magnetic material pattern corresponding to the servo information with the pattern of the soft magnetic material 11. This template is covered with a hard magnetic disk 13 having the ferromagnetic film 14 as a recording layer. In this state, when a magnetic field 15 perpendicular to the hard magnetic disk is applied, the magnetic field concentrates on the soft magnetic material 11 disposed in the non-magnetic material 16 and the ferromagnetic film 14 positioned immediately below is magnetized. Therefore, the magnetic pattern formed in the template is transferred to the hard magnetic disk. According to this method, servo information can be collectively written on the hard magnetic disk, so that the working efficiency is extremely high.

  However, it is extremely difficult to apply this method to patterned media. In the conventional hard magnetic disk, the recording layer is composed of a continuous ferromagnetic film. Therefore, the ferromagnetic film 14 always exists under the soft magnetic body 11 of the template 12. However, in patterned media in which ferromagnetic particles (ferromagnetic material 2) are discretely distributed, the ferromagnetic particles do not always come under the soft magnetic material 11. Therefore, it is necessary to precisely align the template 12 and the patterned media.

  However, the track interval of the patterned media is 100 nm or less, and the bit interval is also several tens of nm. For this reason, alignment of the template 12 and the patterned media is extremely difficult. That is, it is impossible to use the method of writing servo information on the recording layer later for the patterned medium, which has been used in the conventional large-capacity hard magnetic disk.

  Therefore, at present, there is no effective method for recording servo information on the patterned medium other than sequential writing by the magnetic head of the magnetic recording apparatus.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a patterned medium in which servo information is written in advance during the manufacturing process and does not need to be written later, a manufacturing method thereof, a mold material thereof, and a recording / reproducing apparatus thereof.

  In order to achieve the above object, a first aspect of the present invention is that a ferromagnetic material composed of a single magnetic domain separated by a nonmagnetic film formed on a circular substrate has a central portion separated from the circular substrate. Are arranged regularly on the same plurality of concentric circles, and each of the plurality of concentric circles includes a first ferromagnetic material made of the ferromagnetic material and aligned at a first pitch; A second ferromagnetic body made of the ferromagnetic body and arranged at a second pitch different from the first pitch is arranged, and the second ferromagnetic body on one concentric circle constituting the plurality of concentric circles is arranged. The one concentric circle can be distinguished from the other concentric circles by a difference between the arrangement and the arrangement of the other concentric second ferromagnetic bodies constituting the plurality of concentric circles.

  According to the first aspect of the present invention, information relating to the track is written in advance in the second ferromagnetic material array, so that enormous labor for writing servo information later by the magnetic head is not required.

  According to a second aspect of the present invention, a magnetic material composed of a single magnetic domain embedded in a nonmagnetic thin film formed on a circular substrate is regularly arranged on a spiral having the same center as that of the circular substrate. In the aligned magnetic recording medium, a first ferromagnetic body made of the magnetic material and arranged at a first pitch and a first pitch made of the magnetic body and different from the first pitch are arranged in each turn of the spiral. 2nd ferromagnets arranged at a pitch of 2 are arranged, the arrangement of the second ferromagnets on one lap constituting each of the laps, and the second ferromagnets on the other laps constituting each of the laps. The one round is distinguishable from the other round by the difference from the arrangement of the two ferromagnetic bodies.

  According to the second aspect of the present invention, information relating to the track is written in advance in the second ferromagnetic array, so that enormous labor for writing servo information later by the magnetic head is not required.

  According to a third aspect of the present invention, in the first and second aspects, the arrangement of the second ferromagnetic material is encoded.

  According to the third aspect of the present invention, the servo information can be written in advance by the arrangement of the encoded second ferromagnetic material, so that enormous labor is required for writing the servo information including the track number later by the magnetic head. Can be further omitted.

  According to a fourth aspect of the present invention, in the fourth aspect, each of the concentric circles or the laps is divided into a plurality of sections, and a second ferromagnetic body is disposed in each of the plurality of sections, and the encoding is performed. According to the arranged arrangement, one section constituting the plurality of sections can be distinguished from other sections.

  According to the fourth aspect of the present invention, the servo information including the track number and the sector number can be written in advance by the arrangement of the encoded second ferromagnetic material, so that the servo information is written later by the magnetic head. An enormous amount of labor can be further omitted.

  According to a fifth aspect of the present invention, in the first to fourth aspects, the nonmagnetic material is alumina, and the magnetic material is embedded in a hole formed in the alumina.

  According to a sixth aspect of the present invention, there is provided a flat plate-shaped mold member that is pressed against an aluminum film and identifies a position of a hole opened in an alumina formed by anodization. A mold material characterized in that linear convex portions arranged at intervals intersect each other.

  According to the sixth aspect of the present invention, it is easy to manufacture patterned media using alumina nanoholes, and it is possible to manufacture patterned media having a high tolerance for pattern eccentricity.

  A seventh aspect of the present invention is a method for manufacturing a magnetic recording medium according to the first to fifth aspects, the step of forming an aluminum film on a substrate, and the mold material of the sixth aspect is pressed against the aluminum film, Transferring the mold of the mold material to the aluminum film; anodizing the aluminum film to which the mold has been transferred; converting the aluminum film into an alumina film; and forming holes in the transferred area of the mold And forming a ferromagnetic material in the hole.

  According to an eighth aspect of the present invention, there is provided a magnetic recording / reproducing apparatus that performs one or both of recording and reproducing information on the magnetic recording medium according to the first to fifth aspects, wherein the first and second ferromagnetic materials are generated. And a servo information reading device for specifying the arrangement of the second ferromagnetic bodies from the electrical signal.

  According to the present invention, since the servo information is written in the patterned medium in advance during the manufacturing process, the enormous effort of writing the servo information later with the magnetic head is unnecessary, and the recording / reproducing of the information on the patterned medium can be performed. It becomes easy.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the technical scope of the present invention is not limited to these embodiments, but extends to the matters described in the claims and equivalents thereof.

(1) Embodiment 1
This embodiment relates to the structure of a patterned medium in which servo information is written in advance at the manufacturing stage.

  In the patterned medium in the present embodiment, the ferromagnetic particles are aligned on the track at a second pitch different from the first pitch. Servo information is recorded by an array of ferromagnetic particles aligned at the second pitch. On the other hand, data is recorded by the magnetization direction (perpendicular magnetization) of the ferromagnetic particles aligned at the first pitch.

  FIG. 1 is a plan view of the patterned medium 17 in the present embodiment. FIG. 2 is an enlarged view of the servo information recording area 18 of the patterned medium 17. However, FIG. 2 shows only one end (lower side) of the servo information recording area 18 in an enlarged manner. 3 is a cross-sectional view taken along the line AA ′ of FIG. 2 as viewed from the direction of the arrow.

  In the patterned media in the present embodiment, an alumina film 5 is disposed on a circular substrate 1 made of quartz (FIGS. 1 and 3), and ferromagnetic materials 19 made of cobalt (Co) are separated from each other by the alumina. In addition, they are regularly arranged at intervals of 50 nm on a track made up of a plurality of concentric circles 4 having the same center as the substrate 1 and a radius increasing by 60 nm (FIG. 2).

  The details of the cross-sectional structure are as shown in FIG. First, on a substrate 1 (diameter 1 inch) made of crystallized glass, an adhesion layer 20 made of Ta having a flat surface and being firmly adhered to the substrate 1 is formed to a thickness of 50 nm. Next, a base soft magnetic layer 21 made of NiFe is formed on the adhesion layer 20 to a thickness of 50 nm. Next, an oxidation stop layer 22 made of Ta is formed on the underlying soft magnetic layer 21 to a thickness of 10 nm. Next, the alumina film 5 in which the ferromagnetic material 19 is embedded is formed on the oxidation stop layer 22. Further, a protective film 23 made of a diamond-like carbon film is formed on the alumina film 5 to a thickness of 10 nm. Finally, a fluorine-based liquid lubricant 24 is applied on the protective film 23 by about 1 nm.

The substrate 1 may be an Al disk, a quartz disk, a silicon substrate, or a SiO ₂ / Si substrate obtained by thermally oxidizing the surface of a silicon substrate. Further, the adhesion layer 20 may be a Ti film or a Cr film. Further, the base soft magnetic layer 21 may be a CoZrNb film or a CoZrTi film. Further, the oxidation stop layer 22 may be a Ti film or a Ni film.

  The patterned media track 25 in the present embodiment is configured as shown in FIG. That is, on each track 25, there are two types of ferromagnetic materials 19 aligned at a first pitch 26 (50 nm) and a second pitch 27 (70 nm) different from the first pitch. In FIG. 2, ferromagnets 28 aligned at the first pitch (hereinafter referred to as first ferromagnets) are white circles, and ferromagnets 29 aligned at the second pitch (hereinafter referred to as second ferromagnets). Is called a ferromagnet). Information is recorded on or read from the first ferromagnetic material by a recording / reproducing apparatus. On the other hand, the magnetization direction of the second ferromagnetic material 29 is the same for all bits, but the arrangement is different for each track. In the track 1, there is only one second ferromagnetic material 29, and no other second ferromagnetic material 29 exists in the vicinity thereof. In the track 2, three second ferromagnetic bodies 29 exist continuously. In the track 3, a pair 30 of second ferromagnets 29 exists with the two first ferromagnets 28 interposed therebetween. Similarly, in the tracks 4 and 5, there are two pairs of second ferromagnetic bodies 29 with 5 or 8 first ferromagnetic bodies 28 interposed therebetween, respectively.

  Therefore, by reading the arrangement of the second ferromagnetic material 29, the track in the server information recording area 18 can be identified. For example, when 256 tracks are accommodated in one server information recording area, the length of the server information recording area in the radial direction is about 14 μm. This length is sufficiently wider than the pattern alignment accuracy and the eccentricity control accuracy on the order of sub-μm, so that the desired server information recording area 18 (to be precise, the track group having the server information recording area 18) can be obtained only by the stepping motor. The head can be positioned. Therefore, if the magnetic head 52 is positioned in the desired server information recording area 18 by the stepping motor and the individual tracks are identified by the arrangement of the second ferromagnetic material 29, the individual tracks are identified in the entire patterned medium. be able to. The arrow 31 shown in the figure is the traveling direction of the truck. In tracking, the position of the magnetic head 52 is controlled in the radial direction so that the output of the magnetic head 52 is maximized.

  In the example shown in FIG. 2, the track is identified by the difference in the distance between the second ferromagnetic material pairs 30. Various arrangements other than the arrangement shown in FIG. 2 are conceivable as arrangements for identifying tracks.

  FIG. 4 is an example in which different numbers of second ferromagnets 29 are alternately arranged on adjacent tracks 25. If the track interval is relatively wide and the resolution of the head positioning by the stepping motor is 2 tracks or less, individual tracks can be identified by using the head positioning information even by the arrangement as shown in FIG.

  FIG. 5 is an example of patterned media that identifies a track by encoding an array of second ferromagnetic bodies 29. In this example, “1” corresponds to the second ferromagnetic material 29, and “0” corresponds to the first ferromagnetic material 28. For example, the code “1000001000001” corresponds to the track 5. In this way, the arrangement of the second ferromagnetic particles 29 provided in each track is encoded, and each track is identified by the code attached to each track.

  FIG. 6 shows an example in which gaps 35 that indicate the beginning and end of the coding region are provided before and after the coding region. In this example, each track includes a data area 33 (for writing information) made of the first ferromagnetic material 28, and a servo information area 34 in which servo information is written by the arrangement of the second ferromagnetic material 29. The second ferromagnetic body 29 is composed of a data area 33 and a gap 35 that separates the servo information area 34. One data area 33, one servo information area 34, and a pair of gaps 35 constitute one sector 36.

  The servo information area 34 is encoded in the same manner as in FIG. 5, and the code of the uppermost track is “0000000000000”. On the other hand, the code of the lowermost track is “001111101001”. Servo information including a track number and a sector number is associated with this code.

  As described above, there are various methods for recording servo information in the array of the second ferromagnetic bodies 29, and an optimum recording method may be selected as necessary.

The patterned media in the present embodiment relates to patterned media using alumina nanoholes. However, this embodiment can also be applied to other patterned media. For example, the present invention can also be applied to patterned media of a type in which holes are formed in a nonmagnetic material by using an electron beam drawing method and a ferromagnetic material is embedded. In this case, an alumina film may be used as a nonmagnetic material, but another nonmagnetic material film such as SiO ₂ can also be used. Further, the oxidation stop layer 22 is unnecessary. The other configuration may be the same as that of the patterned medium including the arrangement of the first and second ferromagnetic materials.

  In this embodiment, the pitch of the magnetic particles is two, but the pitch may be three or more. Further, the magnetic particles are arranged on concentric tracks, but may be arranged on a spiral 55 as shown in FIG. In this case, each turn is distinguished from the other turn by the arrangement of the second ferromagnetic material. Here, the term “circulation” refers to a section 57 that passes through one point 56 on the spiral while making one revolution on the spiral. That is, one round corresponds to one track. In the following description, only patterned media having concentric tracks will be described. However, if “concentric” is read as “spiral” and “concentric” is read as “circular”, magnetic particles are arranged on the spiral. Explains the patterned media.

(2) Embodiment 2
The present embodiment relates to the patterned media recording / reproducing apparatus described in the first embodiment.

  FIG. 8 is a block diagram of the recording / reproducing apparatus in the present embodiment. FIG. 9 shows signals of the recording / reproducing apparatus shown in FIG.

  The recording / reproducing apparatus according to the present embodiment includes a hard disk assembly (hereinafter referred to as HDA) 58 and a signal processing apparatus 69. The HDA 58 includes a spindle motor, a voice coil motor, magnetism, a head amplifier, and the like. On the other hand, the signal processing device 69 includes a first synchronization signal extraction circuit 60 (hereinafter referred to as PLL1) to which an HDA output 59 obtained by converting the magnetization direction of magnetic particles into an electric signal is input, and an HDA output 59 An input second synchronous signal extraction circuit (hereinafter referred to as PLL2), a first synchronous detection circuit 62 for synchronously detecting the output 59 of the HDA in synchronization with the first clock signal output from the PLL1, A second synchronous detection circuit 63 for synchronously detecting the output 59 of the HDA in synchronization with the second clock signal output from the PLL 2; a decoder, an encoder, and a signal to which the outputs of the first and second synchronous detection circuits are input; The signal processing circuit (not shown) includes a waveform shaping circuit, a memory, a microcomputer, a motor driver, and the like.

  The first synchronization signal extraction circuit 60 is composed of a phase synchronization circuit (PLL) or the like, and outputs a first clock signal synchronized with the phase of the signal generated by the first ferromagnetic material. The second synchronization signal extraction circuit 61 includes a phase synchronization circuit (PLL) and the like, and outputs a second clock signal synchronized with the phase of the signal generated by the second ferromagnetic material.

  The first synchronous detection circuit 62 receives the HDA output 59 and receives the first switch 64 that opens and closes in synchronization with the first clock signal output from the PLL 1 and the first switch 64 outputs the first switch 64. 1 low-pass filter 65. The second synchronous detection circuit 63 receives the HDA output 59 and receives the second switch 66 that opens and closes in synchronization with the second clock signal output from the PLL 2 and the first switch 66 output. 2 low-pass filters 67.

  Here, the first low-pass filter 65 passes the frequency corresponding to the period in which the first ferromagnetic material passes through the magnetic head, and blocks higher frequencies. The second low-pass filter 67 passes the frequency corresponding to the period in which the second ferromagnetic material passes through the magnetic head, and blocks higher frequencies.

  Therefore, the first synchronous detection circuit can selectively extract a signal generated by the first ferromagnetic body. The second synchronous detection circuit can selectively extract a signal generated by the second ferromagnetic material.

  Outputs of the first and second synchronous detection circuits are input to a signal processing circuit (not shown), and a signal recorded on the patterned medium mounted on the HDA is reproduced.

  On the other hand, when recording a signal on the patterned medium, a signal processing device (not shown) acquires servo information from the output of the second synchronous detection circuit 67, and outputs the control signal and data 68 to the HDA to record the information. To do.

  Next, an operation in which the recording / reproducing apparatus of the present embodiment acquires servo information from the patterned medium will be described.

  First, the magnetic head of the HDA 58 converts the magnetic flux change produced by the rotating ferromagnetic particles of the patterned media into an electrical signal. The electrical signal 59 includes a data signal generated by the first ferromagnet and a servo information signal generated by the second ferromagnet. The second synchronization signal extraction circuit 61 (PLL2) extracts the second clock signal 70 phase-synchronized with the servo information signal from the output 59 of the hard disk assembly.

  The second synchronous detection circuit 63 opens and closes the switch 66 in synchronization with the second clock signal output from the PLL 2, and smoothes the output by the second low-pass filter 67 to extract only the servo information signal. That is, the second synchronization signal extraction circuit 61 and the second synchronization detection circuit 63 constitute a servo information reading device.

  FIG. 9 shows the outputs of the second second synchronous signal extraction circuit 61 and the second synchronous detection circuit 63 for the patterned medium having the gap and the servo information area as shown in FIG.

  The first curve 70 shows the output of the second synchronization signal extraction circuit 61. The first to sixth curves 71 are outputs of the second synchronous detection circuit 63 from different tracks. The horizontal axis is time, and the vertical axis is signal intensity.

  As shown by the first curve 70, the second synchronization signal extraction circuit 61 generates a clock signal having a constant period. Then, as indicated by the first to sixth curves 71, the second synchronous detection circuit 63 generates a signal corresponding to the arrangement of the second ferromagnetic material. That is, a signal having a constant period is generated in a period 72 corresponding to the gap 35, a signal corresponding to a track number or a sector number is generated in a period 73 corresponding to the servo information area 34, and a period 74 corresponding to the data area 33 is generated. Does not generate a signal. In addition, the broken line shown in the figure is a threshold value for determining the presence or absence of a signal by the subsequent signal processing circuit. The signal from the first ferromagnet is lower than this threshold, and the signal from the second ferromagnet is higher than this threshold. That is, a signal having a threshold value of 75 or more is distinguished from a signal from the second ferromagnetic material, and a signal having a threshold value of 75 or less is distinguished from a signal from the first ferromagnetic material. Similarly, data is also extracted by the first synchronous signal extraction circuit 60 and the first synchronous detection circuit 62.

  Based on the servo signals and data signals obtained as described above, the signal processing device 69 controls the hard disk assembly 58 to write and read data.

(3) Embodiment 3
The present embodiment relates to the method for manufacturing the patterned medium described in the first embodiment.

  FIGS. 10-12 show the manufacturing method of the patterned media in this Embodiment by principal part sectional drawing.

  First, as shown in FIG. 10 (a), a disc-shaped disk substrate 1 made of crystallized glass, an adhesion layer 20 made of Ta having a thickness of 50 nm, and an underlying soft magnetic layer 21 made of NiFe having a thickness of 50 nm, Then, an oxidation stop layer 22 made of Ta with a thickness of 10 nm and an Al film 7 with a thickness of 100 nm are formed by sputtering. The film forming method is not limited to the sputtering method, and may be another film forming method such as vapor deposition or CVD.

  Here, the adhesion layer 20 is for preventing a film formed by stress in subsequent processes from peeling off. The underlying soft magnetic layer 21 is intended to facilitate perpendicular magnetic recording. The oxidation stop layer 22 is for preventing the underlying soft magnetic layer 21 from being corroded or peeled off during the anodic oxidation of the Al film 7. Accordingly, these layers are not essential components, but are preferably not omitted.

  Next, an imprint resist 36 (polymethyl methacrylate (PMMA), polycarbonate (PC), etc.) is formed on the Al film 7 to a thickness of 50 nm by spin coating (FIG. 10B). ). In addition, it is necessary to adjust the film thickness of a resist suitably according to the height of the unevenness | corrugation of the imprint mold used at the next process.

Next, a mold 37 having a pattern corresponding to a groove for aligning alumina nanoholes is prepared. The mold 37 is pressed against the resist film 36 to imprint the pattern (FIG. 10C). The conditions for imprinting vary depending on the resist material. For example, when PMMA having a glass transition temperature of 120 ° C. is used, the pressure is 500 kg / cm ² , the temperature is 150 ° C., and the holding time is 5 minutes.

  In the present embodiment, the mold pattern is transferred to the resist 36 by a thermal imprint method, but an optical imprint method may be used. Alternatively, the groove pattern may be formed directly on the resist 36 by an electron beam drawing method, a photolithography method, or the like.

  FIG. 13 is a plan view of the mold 37 used in the present embodiment. The upper half of the figure shows the entire mold, and the lower half shows an enlarged view of the portion corresponding to the servo information recording area. FIG. 14 is a cross-sectional view taken along the line AA ′ of FIG. 13 as seen from the direction of the arrow. As shown in FIG. 14, a so-called line and space (hereinafter referred to as “L / S”) pattern 39 in which irregularities of a certain width are periodically repeated is engraved on the mold 37. Here, the recess depth 38 is 50 nm, and the pitch 40 of the L / S pattern is 60 nm (the width of the recess is 30 nm, and the width of the protrusion is also 30 nm). This L / S pattern is for track formation, and the pitch corresponds to the track pitch of the patterned medium in the present embodiment.

  Another L / S pattern is also engraved in the servo information recording area so as to be orthogonal to the L / S pattern. The pitch 41 of this L / S pattern is 70 nm, and alumina nanoholes are selectively formed at the positions where the intersections of the two L / S patterns are transferred, and ferromagnetic particles for recording servo information are embedded. . The depth of the servo information recording area L / S pattern is the same as that of the track L / S pattern, and the width of the concave portion and the width of the convex portion are each 35 nm.

Next, the resist 36 to which the mold 37 has been transferred is subjected to an ashing process using an O ₂ plasma asher (PF power 50 W, processing time 20 s), and the resist residue remaining at the bottom of the recess is removed. Thereafter, the Al film 7 is etched by about 10 nm by chlorine-based RIE. The RIE etching conditions are a pressure of 0.2 pa, a Cl ₂ flow rate of 45 sccm, an Ar flow rate of 5 sccm, and an RF power of 200 W. The RIE etching time is 1 minute (FIG. 11 (d)).

  Next, the resist film 7 is subjected to an ashing process (PF power 50 W, treatment time 60 s), and further immersed in acetone for 1 minute to peel the resist 36 from the AL film 7. When the resist 36 is peeled, irregularities to which the pattern of the mold 37 is transferred appear on the surface of the AL film 7 (FIG. 11E).

  Next, using the AL film 7 as an anode and a separately prepared Al plate as a cathode, these electrodes are immersed in an electrolytic solution made of 0.3 M dilute sulfuric acid, and a voltage of 20 V is applied for 5 minutes. Then, the AL film 7 is anodized to become the alumina film 5, a row of 50 nm pitch alumina nanoholes 9 is formed in the data area in the track, and a 70 nm pitch alumina nanohole row is formed in the servo information area and gap area. The

  The anodic oxidation conditions are for forming alumina nanohole arrays with a pitch of 50 nm in concentric recesses. Therefore, an alumina nanohole array having a pitch of 50 nm is formed in the data area in which only the concave portions are formed on the concentric circles (FIG. 11 (f)).

  By the way, the alumina nanohole has a property of being selectively formed at the intersection where two grooves intersect. Accordingly, alumina nanoholes are selectively formed at positions (concave portions) where the track L / S pattern 39 and the servo information recording area L / S pattern 42 intersect. Since the pitch of the servo information recording area L / S pattern is 70 nm, an alumina nanohole array having a pitch of 70 nm is formed in the servo information area.

Next, the substrate 1 on which the alumina nanoholes are formed is immersed in a plating solution (CoSO ₄ : 50 g / l, boric acid: 20 g / l) made of a cobalt sulfate (CoSo ₄ ) aqueous solution and a boric acid aqueous solution and kept at 50 ° C. In this state, an AC voltage of 12 V is applied between the oxidation stop layer 22 on the substrate 1 and a separately prepared electrode, and the ferromagnetic Co is filled in the alumina nanoholes and plated until the surface of the alumina film is covered. (FIG. 12 (g)).

  Next, Co on the surface is polished by a CMP (chemical mechanical polishing) method to flatten the surface. A slurry mainly composed of silica particles is used as the polishing agent, and the surface of the alumina film 5 is also polished by about 10 nm (FIG. 12H).

  Next, a protective film 23 is formed by depositing DLC (diamond-like carbon) with a thickness of 3 nm on the surface of the planarized alumina film 5 by sputtering. Next, about 1 nm of a fluorine-based liquid lubricant is applied to the surface of the protective film 23 by a dipping method (FIG. 12 (i)).

  Finally, a perpendicular magnetic field is applied to the substrate in which the ferromagnetic material is embedded in the alumina nanoholes to magnetize the entire ferromagnetic particle in one direction.

  Through the above steps, the patterned media as shown in FIGS. 1 to 6 having the servo information area can be manufactured.

The method for producing patterned media in the present embodiment relates to patterned media using alumina nanoholes. In order to manufacture a patterned media of a type in which holes are made in a non-magnetic material and a ferromagnetic material is embedded using an electron beam drawing method, the following may be performed. First, in the process of FIG. 10A, the formation of the oxidation stop film layer 22 is omitted, and for example, a SiO ₂ film is deposited to a thickness of 100 nm by the CVD method instead of the Al film 7. Next, in the step of FIG. 10B, a resist for electron beam drawing is spin-coated by 50 nm instead of the imprint resist. Next, instead of the steps of FIGS. 10 (c) and (d), all the positions (data area, servo information area and gap) where the alumina nanoholes are to be formed are irradiated with an electron beam, and the same as the alumina nanoholes. Draw a circle with a diameter of about 10 nm. Thereafter, the resist is developed to form a pattern having a large number of holes corresponding to alumina nanoholes. Next, a hole penetrating the base soft magnetic film is formed in the SiO ₂ film by chlorine-based RIE. The subsequent steps are the same as the patterned media manufacturing method using the alumina nanoholes.

(4) Embodiment 4
Next, the mold 37 for manufacturing patterned media in the present embodiment will be described.

  As shown in FIG. 13, the mold 37 according to the present embodiment includes a concentric track L / S pattern 39 and a servo information recording area L / S pattern 42 intersecting therewith. As will be described below, this pattern is drawn on a resist film by an electron beam drawing apparatus and copied onto a thick metal film.

  The pattern of the mold for forming the alumina nanoholes is not necessarily a pattern made of L / S as shown in FIG. 13, but may be a pattern in which a large number of points are aligned. However, the use of a pattern made of L / S makes it extremely easy to produce a mold.

  When the Al film in which the dot-like recesses are formed is anodized, alumina nanoholes are selectively formed in the dot-like recesses. Accordingly, the pattern of the mold may be a pattern in which dot-like protrusions are provided one by one at a position where an alumina nanohole is to be formed as shown in FIG. 16 (FIG. 16 shows protrusions for three tracks. is there.). However, if an attempt is made to draw such a pattern with an electron beam drawing device, the electron beam irradiation position must be moved to the next drawing position after blocking (blanking) the electron beam every time a convex part is drawn. Don't be. This method is therefore very inefficient. In contrast to this method, the method using the L / S pattern is extremely efficient because the resist surface only needs to be continuously scanned with an electron beam having a constant current.

  Further, as another pattern of the mold, as shown in FIG. 17, a bump 46 in which the width of the L / S pattern (convex portion) 45 is expanded at the position of the alumina nanohole that carries servo information may be provided. In order to form such a bump, an L / S pattern for a track is first drawn by electron beam drawing, and then a circle slightly wider than the L / S width is drawn at a position where the bump 46 is to be formed.

  This work itself is inefficient because it has to draw a circle one by one. Moreover, if such a pattern is to be drawn, a circle must be drawn so as to overlap the track L / S pattern formed at a track pitch of 60 nm. For such drawing, it is necessary to align the drawing position with an accuracy of several tens of nm. Such highly accurate alignment is extremely difficult, and it is practically impossible to form a pattern as shown in FIG.

  On the other hand, in the pattern (FIG. 13) according to the present embodiment, the servo information recording area L / S pattern 42 is drawn longer than the pitch of the track L / S pattern 39. Therefore, as shown in FIG. The L / S pattern 39 for servo and the L / S pattern 42 for servo information recording area always intersect. That is, in order to draw the servo information recording area L / S pattern 42 in the present embodiment, high-precision alignment is not necessary. Therefore, a mold having a pattern as shown in FIG. 13 can be easily produced. In FIG. 15, the L / S pattern is represented by a straight line, but the width of L (line) and S (space) is actually 1: 1.

  18 and 19 illustrate a manufacturing method of the mold shown in FIG. The right half of the figure is a plan view of a mold or the like that is being created, and the left half is a cross-sectional view taken along the line AA ′ of the plan view as seen from the direction of the arrow.

  First, a resist 48 for electron beam drawing is spin-coated on the silicon substrate 47. The thickness of the resist 48 is about 50 nm (FIG. 18A). As the substrate, a flat disk with a surface made of SiN, glass or the like can be used.

  Next, the substrate 47 coated with the resist 48 is loaded into an r-θ type electron beam drawing apparatus, and a concentric L / S pattern 49 is drawn on the resist 48 at a pitch of 60 nm (FIG. 18B). .

  Next, a straight line group 50 intersecting the concentric L / S pattern 49 is drawn at a pitch of 70 nm in an area corresponding to the servo information recording area (FIG. 18C).

  Next, the resist 48 exposed with the electron beam is developed. FIG. 18D is an enlarged cross-sectional view of a portion where the L / S pattern is formed on the resist 48 by the development process. Hereinafter, FIG. 18F is an enlarged cross-sectional view.

  Next, a Ni film having a thickness of about 50 nm is deposited on the substrate 47 on which the L / S pattern is formed using an electron beam deposition apparatus (FIG. 19E). Using this Ni film as an electrode, Ni is electroformed using an aqueous solution of Ni sulfamate to form a Ni plate 54 having a thickness of 300 μm (FIG. 19F).

  Finally, when the substrate 47 is peeled off and then back surface polishing and outer diameter processing are performed, a mold as shown in FIG. 13 is completed (FIG. 19G).

  The L / S patterns in FIGS. 18B and 18C are drawn by an r-θ type electron beam drawing apparatus in which a sample stage on which a substrate is placed can rotate. However, the concentric L / S pattern in FIG. 18B is drawn by the r-θ type electron beam drawing apparatus, and the short straight line group 50 in FIG. 18C is drawn in the drawing field (scanning direction of the electron beam, that is, XY). If the drawing is performed by an XY type electron beam drawing apparatus whose coordinates can be rotated, the processing speed is further improved.

  In this case, since the substrate must be removed from the r-θ type electron beam drawing apparatus and mounted again on the XY type electron beam drawing apparatus, the center of the concentric L / S pattern 49 is drawn when the straight line group 50 is drawn. It becomes difficult to specify accurately. However, in the present embodiment, servo information is written by intersecting the straight line group 50 with the concentric L / S 49, so that even if there is a slight eccentricity or misalignment, it is easily corrected by information processing during tracking. be able to.

  That is, since some servo information is written in each track (or sector), it is possible to identify each track (or sector) based on that information.

  FIG. 20 is an electron beam drawing pattern for forming the servo information recording area shown in FIG. 2 and FIGS. In the figure, ferromagnetic particles 28 (first ferromagnet) aligned at a pitch of 60 nm and ferromagnetic particles 29 (second ferromagnet) aligned at a pitch of 70 nm are also described. Although the drawing pattern is drawn with a thin line 51, the drawing pattern is actually as wide as the diameter of the ferromagnetic particles 29.

  The patterns shown in FIGS. 20A to 20D are for forming the servo information recording areas shown in FIGS. 2 and 4 to 6, respectively.

  The above embodiment is summarized as follows.

(Appendix 1)
A magnetic recording medium in which a ferromagnetic material composed of a single magnetic domain separated by a nonmagnetic film formed on a circular substrate is regularly aligned on a plurality of concentric circles having the same center as that of the circular substrate. In
Each of the plurality of concentric circles is arranged with a first ferromagnetic material made of the ferromagnetic material and arranged at a first pitch, and with a second pitch made of the ferromagnetic material and different from the first pitch. A second ferromagnet is disposed,
Due to the difference between the arrangement of the second ferromagnetic bodies on one concentric circle constituting the plurality of concentric circles and the arrangement of the other concentric second ferromagnetic bodies constituting the plurality of concentric circles, A magnetic recording medium characterized in that a concentric circle is distinguishable from the other concentric circles.

(Appendix 2)
In a magnetic recording medium in which a magnetic material composed of a single magnetic domain embedded in a nonmagnetic thin film formed on a circular substrate is regularly aligned on the same spiral as the circular substrate,
A first ferromagnetic body made of the magnetic material and aligned at a first pitch and a second ferromagnetic material made of the magnetic material and aligned at a second pitch different from the first pitch are arranged around each of the spirals. Of ferromagnetic material,
Due to the difference between the arrangement of the second ferromagnets on one round constituting each round and the arrangement of the second ferromagnets on the other round constituting each round, the one round A magnetic recording medium characterized in that it can be distinguished from the other rounds.

(Appendix 3)
The magnetic recording medium according to appendix 1 or 2, wherein the array of the second ferromagnetic material is encoded.

(Appendix 4)
Each of the concentric circles or the rounds is divided into a plurality of sections;
A second ferromagnetic body is disposed in each of the plurality of compartments;
The magnetic recording medium according to appendix 3, wherein one of the plurality of sections is distinguishable from another section by the encoded arrangement.

(Appendix 5)
The non-magnetic material is alumina;
The magnetic recording medium according to any one of appendices 1 to 4, wherein the ferromagnetic material is embedded in a hole formed in the alumina.

(Appendix 6)
In the plate-shaped mold material that directly presses against the surface of the aluminum film and identifies the position of the hole opened in the alumina formed by anodization,
A mold material, characterized in that linear convex portions arranged at predetermined intervals intersect with concentric or spiral convex portions.

(Appendix 7)
A method of manufacturing a magnetic recording medium according to appendixes 1 to 5,
Forming an aluminum film on the substrate;
Pressing the mold material according to appendix 6 directly onto the surface of the aluminum film to transfer the mold of the mold material to the aluminum film;
Anodizing the aluminum film to which the mold has been transferred, converting the aluminum film to an alumina film, and forming a hole in the transferred area of the mold;
A method of manufacturing a magnetic recording medium comprising a step of embedding a ferromagnetic material in the hole.

(Appendix 8)
A magnetic recording / reproducing apparatus that performs one or both of recording and reproducing information on the magnetic recording medium according to appendixes 1 to 5,
A recording / reproducing apparatus for a magnetic recording medium, comprising: a servo information reading device that identifies the arrangement of the second ferromagnetic materials from electrical signals generated by the first and second ferromagnetic materials.

  The present invention can be used in the magnetic recording device manufacturing industry.

3 is a plan view of the patterned medium in the first embodiment. FIG. 3 is an enlarged view of a servo information recording area of the patterned medium in Embodiment 1. FIG. It is the figure which looked at the fault in the AA 'line of FIG. 2 from the direction of the arrow. It is the other example 1 of the servo information recording area in Embodiment 1. FIG. 6 is another example 2 of the servo information recording area in the first embodiment. 10 is another example 3 of the servo information recording area in the first embodiment. 6 is another example of patterned media in the first embodiment. FIG. 10 is a block diagram of a recording / reproducing apparatus in a second embodiment. 6 is a diagram illustrating a signal of a recording / reproducing device in Embodiment 2. FIG. It is a 1st figure which shows the manufacturing method of the patterned media in this Embodiment 3. FIG. It is a 2nd figure which shows the manufacturing method of the patterned media in this Embodiment 3. FIG. It is a 3rd figure which shows the manufacturing method of the patterned media in this Embodiment 3. FIG. It is a top view of the mold in which the type | mold for forming the shallow groove | channel which aligns an alumina nanohole in this Embodiment 4 in the Al film | membrane 7 was engraved. It is the figure which looked at the cross section in the AA 'line of FIG. 13 from the direction of the arrow. It is a figure explaining alignment of the L / S pattern for tracks, and the L / S pattern for servo information recording areas. It is a mold pattern in which dot-like convex portions are provided one by one at a position where an alumina nanohole is formed. It is a mold pattern in which a knob is provided at a position where an alumina nanohole is formed. It is a 1st figure which shows the manufacturing method of the mold for alumina nanohole formation in this Embodiment 5. FIG. It is a 2nd figure which shows the manufacturing method of the mold for alumina nanohole formation in this Embodiment 5. FIG. 7 is an electron beam drawing pattern for forming the servo information recording area shown in FIG. 2 and FIGS. It is a conceptual diagram which shows the cross section of patterned media. It is a top view of an alumina nanohole patterned media. It is a manufacturing process of alumina nanohole patterned media. It is a conceptual diagram which shows the magnetic transfer in a magnetic transfer method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Substrate 2 Ferromagnetic particle 3 Nonmagnetic material 4 Concentric circle 5 Alumina film 7 Al film 8 Shallow groove 9 Alumina nanohole 10 Mold 11 Soft magnetic material 12 Model 13 Hard magnetic disk 14 Ferromagnetic film 15 Magnetic field 16 Nonmagnetic material 17 Patterned Media 18 Servo information recording area 19 Ferromagnetic material 20 Adhesion layer 21 Underlayer soft magnetic layer 22 Oxidation stop layer 23 Protective film 24 Liquid lubricant 25 Track 26 First pitch 27 Second pitch 28 Aligned at the first pitch Ferromagnetic material (first ferromagnetic material)
29 Ferromagnetic materials aligned at the second pitch (second ferromagnetic material)
30 Pair of second ferromagnets 31 Traveling direction of track 32 Gap indicating start and end of encoding area 33 Data area 34 Servo information area 35 Gap 36 Resist 37 Mold 38 Mold depth of mold 39 L / L of mold S pattern (for trucks)
40 Mold L / S pattern pitch (track pitch)
41 Pitch of mold L / S pattern (for servo information recording area) 42 L / S pattern of mold (for servo information recording area)
43 Co
44 dot 45 L / S pattern 46 knob 47 silicon substrate 48 resist for drawing electric wire 49 concentric L / S pattern
50 A group of straight lines intersecting the concentric L / S pattern 51 A line indicating a drawing pattern 52 Magnetic head 53 Ni film
54 Ni plate 55 Spiral 56 Point on spiral 57 Circulation 58 Hard disk assembly 59 Output of hard disk assembly 60 First synchronization signal extraction circuit 61 Second synchronization signal extraction circuit 62 First synchronous detection circuit 63 Second synchronization Detection circuit 64 First switch 65 First low-pass filter 66 Second switch 67 Second low-pass filter 68 Control signal and data 69 Signal processing device 70 First curve 71 First to sixth curves 72 Period corresponding to the gap 73 Period corresponding to the servo information area 74 Period corresponding to the data area 75 Threshold

Claims (6)

A magnetic recording medium in which a ferromagnetic material composed of a single magnetic domain separated by a nonmagnetic film formed on a circular substrate is regularly aligned on a plurality of concentric circles having the same center as that of the circular substrate. In
Each of the plurality of concentric circles is arranged with a first ferromagnetic material made of the ferromagnetic material and arranged at a first pitch, and with a second pitch made of the ferromagnetic material and different from the first pitch. A second ferromagnet is disposed,
Due to the difference between the arrangement of the second ferromagnetic bodies on one concentric circle constituting the plurality of concentric circles and the arrangement of the other concentric second ferromagnetic bodies constituting the plurality of concentric circles, A magnetic recording medium characterized in that a concentric circle is distinguishable from the other concentric circles. In a magnetic recording medium in which a magnetic material composed of a single magnetic domain embedded in a nonmagnetic thin film formed on a circular substrate is regularly aligned on the same spiral as the circular substrate,
A first ferromagnetic body made of the magnetic material and aligned at a first pitch and a second ferromagnetic material made of the magnetic material and aligned at a second pitch different from the first pitch are arranged around each of the spirals. Of ferromagnetic material,
Due to the difference between the arrangement of the second ferromagnets on one round constituting each round and the arrangement of the second ferromagnets on the other round constituting each round, the one round A magnetic recording medium characterized in that it can be distinguished from the other rounds.   3. The magnetic recording medium according to claim 1, wherein the second ferromagnetic material array is encoded. Each of the concentric circles or the rounds is divided into a plurality of sections;
A second ferromagnetic body is disposed in each of the plurality of compartments;
The magnetic recording medium according to claim 3, wherein one section constituting the plurality of sections is distinguishable from other sections by the encoded arrangement. The non-magnetic material is alumina;
The magnetic recording medium according to claim 1, wherein the ferromagnetic material is embedded in a hole formed in the alumina. A magnetic recording / reproducing apparatus that performs one or both of recording and reproducing information on the magnetic recording medium according to claim 1,
A recording / reproducing apparatus for a magnetic recording medium, comprising: a servo information reading device that identifies the arrangement of the second ferromagnetic materials from electrical signals generated by the first and second ferromagnetic materials.

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