Classifications

• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
  • G11B5/74—Record carriers characterised by the form, e.g. sheet shaped to wrap around a drum
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B82—NANOTECHNOLOGY
  • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
  • B82Y10/00—Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
  • G11B5/74—Record carriers characterised by the form, e.g. sheet shaped to wrap around a drum
  • G11B5/743—Patterned record carriers, wherein the magnetic recording layer is patterned into magnetic isolated data islands, e.g. discrete tracks
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
  • G11B5/74—Record carriers characterised by the form, e.g. sheet shaped to wrap around a drum
  • G11B5/82—Disk carriers
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
  • G11B5/86—Re-recording, i.e. transcribing information from one magnetisable record carrier on to one or more similar or dissimilar record carriers
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
  • G11B5/02—Recording, reproducing, or erasing methods; Read, write or erase circuits therefor
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
  • G11B5/02—Recording, reproducing, or erasing methods; Read, write or erase circuits therefor
  • G11B5/09—Digital recording

Definitions

• the invention relates to data storage media and, more particularly, patterned magnetic media formed with surface variations.
• Magnetic media generally function according to ferromagnetic principles.
• the surface of a magnetic medium may be coated with one or more magnetic layers, e.g., in the form of a multi-layered magnetic stack or a magnetic alloy.
• the local magnetization of magnetic domains defined on the magnetic layers can be selectively oriented to encode data.
• the local magnetizations can then be detected and interpreted in order to read the recorded data.
• a hysteresis curve typically defines how the magnetic domains can be oriented or reoriented in response to application and removal, of magnetic fields.
• a number of techniques have been developed to increase storage densities and improve quality and reliability of magnetic media. For example, new and improved coatings have been developed in an effort to improve quality and performance of magnetic media.
• Magnetic media can also be categorized as longitudinal or perpendicular. Most conventional magnetic media are longitudinal. In longitudinal media, magnetic anisotropy lies parallel to the plane of the medium. In other words, in longitudinal media, the magnetic orientation of individual magnetic domains is generally parallel to the surface of the medium.
• perpendicular media In perpendicular media, on the other hand, magnetic anisotropy is perpendicular to the plane of the medium. In other words, in perpendicular media, the magnetic orientation of individual magnetic domains is perpendicular to the medium surface. Pe ⁇ endicular media generally allow for higher storage densities than can be achieved in longitudinal media.
• the invention is directed to patterned magnetic media for use in magnetic recording and data storage, and various conditioning techniques that can be used to magnetically condition the patterns.
• a medium can be formed to exhibit a pattern of surface variatipns defined by patterned areas and non-patterned areas.
• the patterned areas may comprise bumps and the non-patterned areas may comprise the regions between the bumps.
• the patterned areas may comprise pits and the non- patterned areas may comprise the regions, between the pits.
• the bumps or pits may be used as units of information storage, e.g., in a pre-defined ROM format, or may comprise servo markings used for tracking purposes.
• the invention provides a magnetic recording medium comprising a substrate, and a magnetic recording layer exhibiting pe ⁇ endicular magnetic anisotropy formed over the substrate.
• the magnetic recording layer may also exhibit a pattern of surface variations defined by patterned areas and non-patterned areas, wherein the patterned areas are magnetized differently than the non-patterned areas. At least some of the patterned areas may define a width less than approximately 5.0 ⁇ m, or less than approximately 1.0 ⁇ m.
• the invention provides a method comprising receiving a patterned magnetic medium having pe ⁇ endicular magnetic anisotropy and exhibiting a pattern of surface variations defined by patterned areas and non- patterned areas, and applying a DC magnetic field to the medium to magnetize the patterned areas differently than the non-patterned areas.
• the invention provides a method comprising receiving a patterned magnetic medium having pe ⁇ endicular magnetic anisotropy and exhibiting a pattern of surface variations defined by patterned areas and non- patterned areas, wherein at least some of the patterned areas define a width less than approximately 5.0 ⁇ m.
• the method may further include applying a first DC magnetic field to the medium to similarly magnetize the patterned areas and the non-patterned areas, and applying a second DC magnetic field to the medium to magnetize the patterned areas differently than the non-patterned areas.
• the invention may be directed to a magnetic storage device such as a magnetic tape drive, a magnetic disk drive, a hard disk drive, a floppy disk drive, a magnetic tape cartridge drive, or the like.
• the magnetic storage device may include a magnetic storage medium, a head to detect magnetic domains on the medium, a controller that controls a position of the head relative to the medium, and a signal processor that inte ⁇ rets detected magnetic domains.
• the magnetic storage medium may include a substrate, a substantially continuous magnetic recording layer exhibiting pe ⁇ endicular magnetic anisotropy formed over the substrate.
• the magnetic recording layer may exhibit a pattern of surface variations defined by patterned areas and non- patterned areas, wherein the patterned areas are magnetized differently than the non-patterned areas.
• the head may comprise a longitudinal read/write head even though the medium exhibits pe ⁇ endicular magnetic anisotropy.
• the invention may be capable of providing one or more advantages.
• the invention may enable increased data storage densities and/or improve tracking capabilities.
• the invention may improve data integrity by allowing corrupted media to be reconditioned such that data can once again be magnetically detected following corruption.
• the invention may allow for ON/OFF magnetic switching of patterned features, as well as simple polarization reversals, if desired.
• FIG. 1 is a conceptual top view of an exemplary magnetic recording medium.
• FIGS. 2-8 are conceptual enlarged cross-sectional side views of an exemplary magnetic recording media according to embodiments of the invention.
• FIG 9 is a conceptual cross-sectional view of an exemplary data storage medium being conditioned by a read/write head in accordance with an embodiment of the invention.
• FIGS. 10A and 10B are additional conceptual cross-sectional views of an exemplary data storage medium being conditioned by a read/write head in accordance with another embodiment of the invention.
• FIG. 11 is a flow diagram according to an embodiment of the invention.
• FIGS. 12 and 13 are block diagrams of exemplary magnetic storage devices that may be used to read or record data on media described herein.
• the invention is directed to patterned magnetic media and conditioning techniques for the patterned magnetic media.
• patterned magnetic media refers to magnetic media formed with surface variations which are used for information storage, servo tracking pu ⁇ oses, or the like.
• the patterned magnetic media may be formed with patterned surface variations such as bumps, pits, ridges, rails, channels, grooves, or other types of protrusions or depressions.
• conditioning refers to magnetically orienting a medium to define desired local magnetic states on the medium.
• the patterned media is described as pe ⁇ endicular magnetic media.
• pe ⁇ endicular magnetic media refers to magnetic media in which magnetic anisotropy is pe ⁇ endicular to the surface of the medium.
• longitudinal magnetic media refers to magnetic media in which magnetic anisotropy is generally parallel to the surface of the medium.
• Pe ⁇ endicular media allows for much higher storage densities than can be achieved in longitudinal media.
• a patterned, pe ⁇ endicular magnetic medium is described that is conditioned for magnetic detection of the patterned features. The conditioning techniques are also described.
• FIG. 1 is a conceptual top view of an exemplary magnetic recording medium 10.
• Medium 10 is illustrated as a disk, but the invention is not limited in that respect.
• medium 10 could alternatively take the form of a card- shaped medium, magnetic tape, or other media types.
• medium 10 is formed with a pattern of surface variations 12.
• the pattern of surface variations 12 comprises surface bumps that protrude a small distance from the surface of medium 10.
• the pattern of surface variations 12 may comprise pits, ridges, rails, channels, grooves, or other types of protrusions or depressions that protrude from or extend into the surface of medium 10.
• Surface variations 12 may comprise pre-embossed features used for data storage or servo tracking pu ⁇ oses.
• surface variations 12 may be embossed, etched, molded, ablated, or the like, e.g., on a polymer material that forms an underlayer of medium 12, or possibly on the substrate of medium 10.
• surface variations 12 may be arranged as data patterns defined by bumps.
• the surface variations may define servo patterns used for tracking pu ⁇ oses.
• the surface variations may provide a microscopic roughness or texture to the surface of medium 10.
• the different surface variations may have similar shapes to one another, or may assume different shapes, as illustrated in FIG. 1.
• surface variations 12 may contain servo patterns for tracking pu ⁇ oses, and in some embodiments the surface variations may represent encoded data, e.g., in a read-only format. Regardless of content, however, the surface variations 12 may be pre-written at relatively low cost, e.g., by processes such as stamping, embossing, molding, ablation, or the like.
• Mechanically formed surface variations 12 may be sized smaller than conventional magnetic domains, and thus may provide the ability to achieve higher storage densities on medium 10 than can be achieved with conventional magnetic media that does not include surface variations. For example, in some cases, individual surface variations may have at least one lateral dimension less than one ⁇ m.
• surface variations 12 are depressions, such as pits or grooves, the variations may be 20 nm to 150 nm deep. If surface variations 12 project from medium 10, they may project a height less than a fly height (in the case of flyable media), ensuring that medium 10 maintains a flyable surface by avoiding head-to- medium collisions.
• surface variations 12 include a plurality of oval shaped bumps, some having a surface area less than 40,000 nm 2 . Again, these data bumps may project from medium 10 to a height less than the fly height, e.g., in the case of flyable media.
• a medium designed to fly at a height of 25 nm may have bumps that project from the medium to a height less than 20 nm. Bumps of this size may allow significant areal density of read-only data (>1 Gigabit/cm 2 ) while still ensuring that the medium maintains a flyable surface for a read head.
• patterned areas of medium 12 can be magnetized differently than non-patterned areas of medium 10.
• surface variations 12 can be magnetized differently than the areas between the respective surface variations 12.
• patterned areas refers to areas corresponding to topographical features such as bumps, pits, ridges, rails, channels, grooves, or other types of protrusions or depressions.
• non- patterned areas refer to the generally flat and co-planer regions between the patterned areas.
• Magnetic conditioning can improve the detectability of surface variations, e.g., allowing a magnetic head to magnetically detect the presence or absence of individual surface variations with greater ease. Accordingly, format information or data may be encoded in medium 10 by the creation of surface variations 12, and then conditioned for magnetic detection. In some cases, the magnetic conditioning of surface variations 12 can be used to effectively turn the pattern ON or OFF magnetically. Also, if medium 10 becomes demagnetized, data recovery can be performed by reconditioning surface variations 12 for magnetic detection.
• FIG. 2 is a conceptual enlarged cross-sectional side view of an exemplary magnetic recording medium 10B according to an embodiment of the invention.
• magnetic recording medium 10B includes a substrate 20, and a magnetic recording layer 22 formed over substrate 10. Additional layers may optionally be added between substrate 20 and a magnetic recording layer 22 such as seed layers to facilitate growth of recording layer 22 or a polymer layer used to define patterned areas 25 in recording layer 22. Also, additional layers may be added over magnetic recording layer 22, such as a lube layer or hard coat. In any case, magnetic recording layer 22 exhibits a pattern of surface variations defined by patterned areas 25 and non-patterned areas 26.
• magnetic recording layer 22 comprises a magnetic alloy formed of a number of materials.
• magnetic recording layer 22 may include a number of sub-layers, e.g., arranged as a multi-layered magnetic stack.
• Magnetic recording layer 22 is typically formed by a deposition process in which the material or materials of recording layer 22 are sputtered onto substrate 20, or sputtered onto one or more other layers formed over substrate 20 prior to the deposition of recording layer 22.
• etching or selective removal of portions of magnetic recording layer to magnetically distinguish the patterned areas 25 from non-patterned areas 26 may be avoided, in favor of conditioning techniques described herein.
• magnetic recording layer 22 may be a substantially continuous layer that does not include areas having the recording material selectively removed.
• Magnetic recoding layer 22 may comprise a pe ⁇ endicular recording layer in which the magnetic anisotropy of layer 22 is pe ⁇ endicular to the plane of medium 10B. In other words, the magnetic orientation of individual magnetic domains is pe ⁇ endicular to the medium surface. Pe ⁇ endicular media generally allow for a much higher storage density than can be achieved in longitudinal media.
• patterned areas 25 are magnetized differently than the non-patterned areas 26 via conditioning techniques that enable the ability to magnetically detect patterned areas 25 using conventional longitudinal read heads.
• a DC magnetic field selected to have the appropriate field strength can be used to magnetize patterned areas 25 substantially the same (as indicated by the similar pe ⁇ endicular orientation of the arrows) without substantially affecting the magnetization of non-patterned areas 26.
• a conventional longitudinal read head can be used to detect individual features of patterned areas 25. In this manner, the ability to magnetically detect the individual features of patterned areas storing data, tracking information, or the like, can be improved.
• patterned areas 25 may have a width (W) less than approximately 5.0 ⁇ m, and, more preferably, less than approximately 1.0 ⁇ m.
• the height (H) of patterned areas (or depth if depressions are used rather than protrusions) may be in the range of 5-100 nm, and more preferably approximately 20-50 nm.
• the use of a magnetic recording layer 22 exhibiting pe ⁇ endicular magnetic anisotropy is a feature that enables effective conditioning to occur, as described herein, specifically when the widths W of patterned areas are less than approximately 5.0 ⁇ m, and more specifically less than approximately 1.0 ⁇ m.
• medium 10C includes magnetic recording layer 32 defining patterned areas 35 that are magnetized substantially the same, albeit differently than non-patterned areas 36.
• the polarization of the magnetization of patterned areas 35 is reversed relative to patterned areas 25 illustrated in FIG. 2.
• One advantage of the conditioning techniques described herein is the ability to easily perform such a polarization reversal as described in greater detail below.
• at least some of patterned areas 35 may have a width (W) less than approximately 5.0 ⁇ m, and more preferably, less than approximately 1.0 ⁇ m, and a height (H) or depth in the range of approximately 5-100 nm.
• FIG. 4 is a conceptual enlarged cross-sectional side view of an exemplary magnetic recording medium 10D illustrating one exemplary method for forming patterned areas 45.
• patterned areas 45 are formed by replicating features 47 into substrate 40.
• features 47 may be defined during a mastering and stamping process in which a stamper is created from a master and then used in an injection molding process to injection mold substrate 40 to exhibit features 47.
• features 47 may be etched, embossed, ablated, or the like, into substrate 40 after substrate is molded.
• a substantially continuous magnetic recording layer 42 can be deposited over substrate such that recording layer 42 substantially conforms to features 47.
• patterned areas 45 can be defined by features 47 formed in substrate 40.
• at least some of patterned areas 45 may have a width (W) less than approximately 5.0 ⁇ m, and more preferably, less than approximately 1.0 ⁇ m, and a height (H) or depth in the range of approximately 5-100 nm.
• an additional layer may be added over a substantially flat substrate prior to the deposition of the recording layer. In that case, the additional layer may be replicated, ablated, embossed, or the like, to form features similar to features 47 (FIG. 4).
• patterned areas may be formed directly in a substantially continuous recording layer, such as via a calendaring process using an embossing calendar drum that replicates such features directly into the recording material.
• the invention is generally not limited to the methods or manner in which patterned areas and non-patterned areas are formed in the recording layer. Rather, a wide variety of techniques may be used to define the patterned areas, including replication, embossing, ablation, calendaring, or the like.
• FIG. 6 illustrates medium 10F that is similar to medium 10E of FIG. 5. However, the polarization of the magnetization of patterned areas 65 are reversed relative to patterned areas 55 illustrated in FIG. 5.
• one advantage of the conditioning techniques described herein is the ability to easily perform such a polarization reversal. For example, after orienting the patterned areas in a first direction using a first DC pass of a head over the medium as described below, a second DC pass of opposite polarity can be performed to orient the patterned areas opposite the first orientation.
• an erase pass followed by a write pass of the head may be used to condition the medium as outlined below.
• a first erase pass and a first write pass to orient the patterned areas, and a second erase pass and a second write pass may reorient the patterned areas in a reversed fashion.
• the patterned areas may be unmagnetized and the non-patterned areas may be magnetized with substantially the same polarization. Such a configuration may be particularly useful if pits are used as the surface variations rather than bumps as illustrated in FIGS. 5 and 6.
• FIG. 7 and 8 illustrate media 10G and 10H, respectively, in which patterned areas 75, 85 are magnetized in one polarization and non-patterned areas 76, 86 are magnetized in the opposite polarization. Such opposing polarizations in the patterned areas 75, 85 relative to the respective non-patterned areas 76, 86 can even further enhance the ability to magnetically detect individual patterned features.
• an additional conditioning step can be performed as outlined in greater detail below.
• FIG. 9 is a conceptual cross-sectional view of exemplary data storage medium 101 being conditioned by a read/write head 90 in accordance with an embodiment of the invention.
• head 90 passes over medium 101, applying a DC magnetic field 94 to the surface of medium 101.
• an electrical direct current (DC) is applied to head 90 causing the head to produce a non-oscillating field 94.
• the strength of DC magnetic field 94 is strong enough to magnetize patterned areas 95, but too weak to substantially magnetize non-patterned areas 96.
• the conditioning pass of head 90 (as illustrated by the lateral arrows) conditions patterned areas 95 such that patterned areas 95 are magnetized substantially the same and differently from non-patterned areas 96.
• the same concept may be applied to surface variations in the form of pits in which the DC magnetic field is strong enough to magnetize non- patterned areas, but too weak to magnetize patterned areas.
• magnetic recording layer 92 may exhibit pe ⁇ endicular magnetic anisotropy.
• head 90 may comprise a conventional longitudinal read/write head, such as the Seagate Apollo Certifier Head, commercially available from Seagate Technology of Scotts Valley
• head 90 can be used to apply an appropriately selected DC magnetic field sufficient to magnetize patterned areas 95, but insufficient to magnetize non-patterned areas 96 (or vice versa). Selective magnetization of the patterned areas vs. non-patterned areas may occur because of the different magnetic flux intensities associated with the slight changes in head to medium spacing caused by the existence or absence of a patterned feature directly below head 90 at any given instance.
• the DC magnetic field needed to selectively magnetize non-patterned areas 96, or in the case of pits, to selectively magnetize non-patterned areas may depend on the composition of recording layer 92, as well as the distance from head 90 to medium.
• effective conditioning occurred by applying approximately a 15 mA current (or -15 mA current) to head 90 and passing head 90 over medium 101 at a head-to-medium spacing of less than approximately 25 nm.
• the head 90 may move over medium 101 at a speed in a range of 1800-15000 revolutions per minute (RPM), such as a speed of approximately 3600 RPM or greater.
• RPM revolutions per minute
• field 114 may be created by applying approximately a -15 mA current (or 15 mA current) to head 90 and passing head 90 over medium 10J at a head-to-medium spacing of less than approximately 25 nm and a head speed of approximately 3600 RPM.
• the erase pass (FIG. 10 A) uses a positive current
• the write pass (FIG. 10B) should use a negative current.
• the erase pass (FIG. 10 A) uses a negative current
• the write pass (FIG. 10B) should use a positive current.
• the use of an erase pass, followed by a write pass may improve performance of medium 10J in terms of the read-back signal strength and ability to detect the magnetically enabled surface patterns.
• a bulk erase process could also be used instead of an erase pass.
• the same effect of the erase pass may be achieved by subjecting the medium to a large magnetic field that commonly orients all the magnetic domains of the medium.
• the techniques described herein can realize several other advantages, including the ability to easily reverse the polarization of patterned areas relative to non-patterned areas, or vice versa.
• the techniques may be used to magnetically turn surface patterns ON or OFF by respectively performing a write pass or an erase pass.
• the selective magnetic ON/OFF switching of patterned areas may be used for security pu ⁇ oses.
• the write pass or an erase pass followed by a write pass, may be used to recondition media, e.g., following corruption or demagnetization of the media. Accordingly, the techniques described herein may improve the integrity of stored data in the sense that corruption of a medium can be easily corrected by effective reconditioning.
• FIG. 11 is a flow diagram illustrating a conditioning technique according to an embodiment of the invention.
• a patterned medium is formed (111), such as by replicating a pattern of surface variations in a substrate or a layer formed over the substrate, and then depositing a magnetic recording layer so that it substantially conforms to the surface variations.
• the patterned medium can be formed by etching, embossing, calendaring, or the like.
• the patterned areas may have widths less than approximately 5.0 ⁇ m, and more specifically less than approximately 1.0 ⁇ m.
• the deposited magnetic recording layer may exhibit pe ⁇ endicular magnetic anisotropy to ensure that conditioning of the patterned areas will be effective.
• the medium can be conditioned by applying DC magnetic field(s) to the medium (113).
• DC magnetic field(s) For example, a single write pass with the read head may be performed as illustrated in FIG. 9, or more preferably, an erase pass followed by a write pass of the head may be performed as illustrated in FIG. 10.'
• appropriately selected DC magnetic fields can cause the magnetic orientation of patterned areas to differ from the orientation of the non- patterned areas.
• this orientation is generally pe ⁇ endicular to the surface of the medium, which allows effective conditioning to occur even when widths associated with the patterned features are less than approximately 5.0 ⁇ m, or less than approximately 1.0 ⁇ m.
• the medium can be read in a magnetic drive (115) because the conditioning magnetically distinguishes the patterned areas from the non-patterned areas. Moreover, if the medium later becomes corrupted, e.g., by demagnetization, (yes branch of 117), conditioning can be performed again to uncorrupt the medium (113). Specifically, the bumps or pits can be conditioned, following corruption, to restore the desirable magnetic orientations of the pattern.
• the magnetic drive can be programmed to perform a conditioning algorithm in response to detection of corruption. In any case, the invention may provide improved data integrity by allowing a corrupted medium to be reconditioned in a simple and effective manner.
• Another advantage of the techniques described herein is that they allow for polarization reversal.
• the magnetization of the patterned areas relative to the non-patterned areas can be reversed.
• the magnetization can be reversed by applying a -15 mA field.
• the magnetizations can be reversed by later performing an erase pass at - 50 mA, and a write pass at 15 mA. In this manner, the polarization of the patterned features of medium can be easily reversed.
• magnetic storage device 130 of FIG. 13 may be coupled to a computer 138 via an interface 139.
• computer 138 may comprise a central processing unit for any of a variety of computer devices, including, for example, a PC, a Macintosh, a computer workstation, a hand-held data terminal, a palm computer, a cell phone, digital paper, a digital television, a wireless device, a personal digital assistant, a laptop computer!, a desktop computer, a digital camera, a digital recording device, or the like.
• the invention may be capable of providing a number of advantages.
• pe ⁇ endicular magnetic media according to the invention may achieve higher storage densities than conventional longitudinal media.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Nanotechnology (AREA)
• Physics & Mathematics (AREA)
• Mathematical Physics (AREA)
• Theoretical Computer Science (AREA)
• Crystallography & Structural Chemistry (AREA)
• Magnetic Record Carriers (AREA)
• Recording Or Reproducing By Magnetic Means (AREA)
• Manufacturing Of Magnetic Record Carriers (AREA)

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• 2002
  • 2002-10-29 US US10/283,401 patent/US6999279B2/en not_active Expired - Lifetime
• 2003
  • 2003-10-16 AU AU2003277386A patent/AU2003277386A1/en not_active Abandoned
  • 2003-10-16 DE DE10393593T patent/DE10393593T5/de not_active Withdrawn
  • 2003-10-16 WO PCT/US2003/032594 patent/WO2004040559A2/en not_active Ceased
  • 2003-10-16 JP JP2004548381A patent/JP2006505091A/ja active Pending
  • 2003-10-16 CN CNA2003801025218A patent/CN1708788A/zh active Pending

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