Abstract: A hard disk drive or other storage device comprises a storage medium, a write head configured to write data to the storage medium, and control circuitry coupled to the write head. The control circuitry comprises degauss circuitry coupled to or otherwise associated with one or more write drivers. The degauss circuitry is configured to generate an asymmetric degauss signal to be applied to the write head. The asymmetric degauss signal has a waveform with upper and lower decay envelopes that are asymmetric about a specified degauss current level, such as a substantially zero current level.

Abstract: A storage device includes a storage medium having a plurality of tracks of data. Reading apparatus for reading a current track of data that has been subject to previous encroachment to an extent from at least one adjacent track of data includes a write head that writes interfering data to the adjacent track of data while intentionally encroaching at least to that extent onto the current track of data, and circuitry that recovers data on the current track of data using the interfering data. A method for reading a current track of data, that has been subject to previous encroachment to an extent from at least one adjacent track of data, includes writing interfering data to the adjacent track of data while intentionally encroaching at least to that extent onto the current track of data, and recovering data on the current track of data using the interfering data.

Abstract: A method and system for estimating a zero gain start (ZGS) bias in a read channel is disclosed. The method may include: receiving preamble samples within a fixed-length window selected for ZGS calculation; calculating an energy associated with a 2T frequency in the preamble samples; calculating an energy associated with non-2T frequencies in the preamble samples; and calculating the ZGS bias based on the energy associated with the 2T frequency in the preamble samples and the energy associated with non-2T frequencies in the preamble samples.

Abstract: Magnetoresistive (MR) bias is dynamically controlled in a tape drive using a processor device. Median tape head amplitude is monitored during a calibration operation, as measured across all tracks of the tape head, against predetermined thresholds of the tape drive for determining if the median tape head amplitude is below the threshold value. Upon determining the median tape head amplitude is below the threshold value during the calibration operation, a reference MR bias and a MR bias range is dynamically adjusted, during the calibration operation, for increasing the median tape head amplitude.

Abstract: A hard disk drive or other storage device comprises a storage medium, a write head configured to write data to the storage medium, and control circuitry coupled to the write head. The control circuitry comprises degauss circuitry coupled to or otherwise associated with one or more write drivers. The degauss circuitry is configured to generate an asymmetric degauss signal to be applied to the write head. The asymmetric degauss signal has a waveform with upper and lower decay envelopes that are asymmetric about a specified degauss current level, such as a substantially zero current level.

Abstract: Magnetic storage tape and techniques for erasing and writing to magnetic storage tape having a perpendicular squareness greater than 50 percent and a longitudinal squareness less than 50 percent are described. In general, the magnetic tape may be biased with a remanence magnetization, or magnetic orientation, in any direction. One or two head systems may use various magnetic field patterns to create the desired remanence magnetization. Servo marks may have a remanence magnetization in an opposite magnetic orientation than that of the remaining bias on the servo track, e.g., substantially perpendicular to the magnetic tape. In some examples, a write head may alternate the direction of the magnetic field to continuously bias and write servo patterns to the magnetic tape. In addition, a symmetrical servo mark may be created in the magnetic tape with a write head having a gap width approximately equal to the length of the servo mark.

Abstract: The magnetic data eraser includes: a mounting and immobilizing tray on which a magnetic recording medium is mounted, the mounting tray being inclined at an angle of 60±10 degrees to the horizontal; a magnetizer that is encircled by a magnetizing coil, the magnetizer having a hollow portion into which the mounting and immobilizing tray is inserted; and a controller that causes an electric current to flow as an excitation current through the magnetizing coil, the excitation current generating a magnetic field that erases data stored in the magnetic recording medium.

Abstract: Magnetic storage tape and techniques for erasing and writing to magnetic storage tape having a perpendicular squareness greater than 50 percent and a longitudinal squareness less than 50 percent are described. In general, the magnetic tape may be biased with a remanence magnetization, or magnetic orientation, in any direction. One or two head systems may use various magnetic field patterns to create the desired remanence magnetization. Servo marks may have a remanence magnetization in an opposite magnetic orientation than that of the remaining bias on the servo track, e.g., substantially perpendicular to the magnetic tape. In some examples, a write head may alternate the direction of the magnetic field to continuously bias and write servo patterns to the magnetic tape. In addition, a symmetrical servo mark may be created in the magnetic tape with a write head having a gap width approximately equal to the length of the servo mark.

Abstract: Magnetic storage tape and techniques for erasing and writing to magnetic storage tape having a perpendicular squareness greater than 50 percent and a longitudinal squareness less than 50 percent are described. In general, the magnetic tape may be biased with a remanence magnetization, or magnetic orientation, in any direction. One or two head systems may use various magnetic field patterns to create the desired remanence magnetization. Servo marks may have a remanence magnetization in an opposite magnetic orientation than that of the remaining bias on the servo track, e.g., substantially perpendicular to the magnetic tape. In some examples, a write head may alternate the direction of the magnetic field to continuously bias and write servo patterns to the magnetic tape. In addition, a symmetrical servo mark may be created in the magnetic tape with a write head having a gap width approximately equal to the length of the servo mark.

Abstract: Magnetoresistive (MR) bias is dynamically controlled in a tape drive using a processor device. Upon determining head amplitude is below a threshold value, the MR bias is adjusted for increasing the head amplitude and extending the useful life span of the tape drive.

Abstract: Amplifier architectures are provided for current sensing applications. An amplifier includes a load device, an operational amplifier, a current source, and a bipolar transistor. The operational amplifier has a first input terminal connected to a first input node that receives an input current, and a second input terminal connected to a second input node that receives a reference voltage. The current source is connected to an output of the operational amplifier. The operational amplifier, the current source, and the bipolar transistor form a feedback loop that generates and maintains a bias voltage on the first input node based on the reference voltage applied to the second input node. The bipolar transistor amplifies the input current received on the first input node, and generates an amplified input current. The load device converts the amplified input current to an output voltage, wherein the output voltage is used to sense the input current.

Abstract: A system comprises a magnetic medium with a first magnetic gap adjacent a first side and a second magnetic gap adjacent a second side, opposite the first magnetic gap. The first magnetic gap generates first longitudinal and perpendicular field components. The second magnetic gap generates second longitudinal and perpendicular field components. The first and second longitudinal field components are substantially aligned along a recording layer of the magnetic medium, and the first and second perpendicular field components are substantially opposed across the recording layer of the magnetic medium.

Abstract: A hard disk drive or other disk-based storage device comprises a storage disk, a write head configured to write data to the disk, and control circuitry coupled to the write head. The control circuitry comprises a write driver and degauss circuitry associated with the write driver. The degauss circuitry is configured to generate a degauss signal to be applied to the write head by the write driver. The degauss signal has a waveform comprising a plurality of decay segments including at least one alternating current decay segment and at least one direct current decay segment. An initial decay segment of the plurality of decay segments may comprise an alternating current decay segment or a direct current decay segment, and may be immediately followed by a decay segment of the opposite type.

Abstract: An asymmetry is determined of a signal generated by a read transducer in proximity to a changing magnetic field of a magnetic media. In response to determining the asymmetry of the signal, a current flowing through a heater of the read transducer is adjusted to cause a change to a magnetic field generated by the current. The change to the magnetic field generated by the current reduces the asymmetry of the signal.

Abstract: Methods and apparatus are provided related to magnetic recording tape. Respective voltage sources are coupled to respective magnetic head components of a tape recording apparatus. Circuitry controls each voltage source independently in accordance with identity information for a magnetic tape, relative humidity within the tape recording apparatus, or other factors. Chemical migration from the tape, and/or plating or erosion of elements of the tape recording apparatus are substantially reduced or eliminated according to the present teachings.

Abstract: A method and apparatus for bipolar writing of servo marks to perpendicular and non-oriented magnetic recording medium. The method includes applying a varying current to a servo write head to alternately AC-erase and write sets of servo marks to regions of a servo track of a magnetic recording medium proximate to first and second write gaps, each servo mark of the sets of servo marks comprising first and second abutting magnetic domains of opposite magnetization directions, the magnetic recording medium moving with respect to the first and second write gaps in a recording direction, the magnetic recording medium being either (i) a perpendicular magnetic storage medium having magnetic particles with their easy axes oriented perpendicular to a top surface of the perpendicular storage medium or (ii) a non-oriented magnetic storage medium having magnetic particles with their easy axes randomly oriented relative to a top surface of the non-orientated storage medium.

Abstract: Various embodiments of the present invention provide systems and methods for data processing. As an example, a data processing circuit is disclosed that includes a data detector circuit and a bias calculation circuit. The data detector circuit is operable to apply a data detection algorithm to a first data set to yield a first series of soft decision data, and to apply the data detection algorithm to a second data set to yield a second series of soft decision data. The bias calculation circuit operable to calculate a series of bias values based at least in part on the first series of soft decision data and the second series of soft decision data. The series of bias values correspond to a conversion between the first series of soft decision data and the second series of soft decision data.

Abstract: A method to tune an oscillation layer frequency in a spin torque oscillator (STO) during a microwave assisted magnetic recording (MAMR) process is described. The STO oscillation layer (OL) has a large angle magnetization oscillation frequency that is locked to a magnetic medium bit resonance frequency f0 when the rf current has a frequency f=f0 and a threshold current density is applied. Alternatively, the OL magnetization oscillation frequency may be adjusted closer to f0 to improve the assist process. A third advantage is lowering the threshold current density when both direct current and rf current are injected into the STO during a write process. The main pole is grounded when direct current and rf current are injected into a write shield.

Abstract: Method and apparatus for detecting head disk interference (HDI). In accordance with some embodiments, a bias calibration circuit is adapted to respectively bypass or amplify a head disk interference (HDI) signal output from an HDI sensor responsive to a bias voltage adjusted according to a first control signal. A detection circuit is adapted to compare a swing range of a signal output from the bias calibration circuit and a swing range of a reference signal, and to output the first control signal responsive to said comparison.

Abstract: To manufacture a perpendicular magnetic recording-type magnetic tape having a servo signal written therein by a write head having a magnetic gap, a perpendicular direct-current erasing step in which a magnetic tape is magnetized in one direction that is one of two opposite thickness directions of the magnetic tape is performed before a signal writing step in which a servo signal is written in the magnetic tape by outputting a pulsed signal to the write head.

Abstract: Magnetoresistive (MR) bias is dynamically controlled in a tape drive using a processor device. Upon determining head amplitude is below a threshold value, the MR bias is adjusted for increasing the head amplitude and extending the useful life span of the tape drive.

Abstract: A method and a storage system are provided for implementing fragmented stream handling for persistent media including shingled disk drives (SDDs). A plurality of Exception Regions for recording stream commands is defined for disk regions. One state is maintained in each of the Exception Regions including a free Exception Region, an active Exception Region, a recovery Exception Region and a used Exception Region. TRIM commands are issued by a host to the drive to indicate deleted content.

Abstract: A method and system for estimating a zero gain start (ZGS) bias in a read channel is disclosed. The method may include: receiving preamble samples within a fixed-length window selected for ZGS calculation; calculating an energy associated with a 2T frequency in the preamble samples; calculating an energy associated with non-2T frequencies in the preamble samples; and calculating the ZGS bias based on the energy associated with the 2T frequency in the preamble samples and the energy associated with non-2T frequencies in the preamble samples.

Abstract: Systems and methods that sense or obtain environmental conditions of a tape drive and dynamically apply voltage biases to tape head assembly elements based on the sensed/obtained environmental conditions to reduce tape stain accumulation and prolong tape head performance. Detection of different first and second sets of environmental conditions (e.g., in relation to temperatures, humidity levels, tape movement directions, etc.) may result in respective first and second voltage bias level sets being applied to respective first and second head assembly element sets. For instance, different first and second voltage bias level sets may be applied to the same head assembly elements (e.g., the first and second head assembly element sets may be the same), or the first and second voltage bias level sets may be applied to different head assembly elements (e.g., the first and second head assembly element sets may be at least partially different).

Abstract: The disclosure is directed to a method for creating a remnant magnetization on a magnetic tape medium. The magnetic tape is first substantially demagnetized, e.g., erased, by an erasure unit having multiple magnetic elements of alternating polarity. The erased magnetic tape is then passed by a bias magnet that creates a remnant magnetization on the magnetic tape. The remnant magnetized magnetic tape is then passed through a servo write head that writes servo patterns to the remnant magnetized magnetic tape. The bias magnet may be housed within the erasure unit or within a bias unit, and the distance between the bias magnet and the tape path of the magnetic tape may be adjustable to create the desired remnant magnetization on the magnetic tape. The remnant magnetization created on the magnetic tape may be greater than 20 percent to reduce defects in the servo pattern written to the magnetic tape.

Abstract: A storage device includes a storage medium having a plurality of tracks of data. Reading apparatus for reading a current track of data that has been subject to previous encroachment to an extent from at least one adjacent track of data includes a write head that writes interfering data to the adjacent track of data while intentionally encroaching at least to that extent onto the current track of data, and circuitry that recovers data on the current track of data using the interfering data. A method for reading a current track of data, that has been subject to previous encroachment to an extent from at least one adjacent track of data, includes writing interfering data to the adjacent track of data while intentionally encroaching at least to that extent onto the current track of data, and recovering data on the current track of data using the interfering data.

Abstract: The magnetic data eraser includes: a mounting and immobilizing tray on which a magnetic recording medium is mounted, the mounting tray being inclined at an angle of 60±10 degrees to the horizontal; a magnetizer that is encircled by a magnetizing coil, the magnetizer having a hollow portion into which the mounting and immobilizing tray is inserted; and a controller that causes an electric current to flow as an excitation current through the magnetizing coil, the excitation current generating a magnetic field that erases data stored in the magnetic recording medium.

Abstract: A magnetic tape drive has a drive system to move a magnetic tape longitudinally; servo head(s) for reading servo band information from a magnetic tape as the magnetic tape is moved longitudinally; a magnetic tape read write head configured to read and to write the magnetic tape, having a data write width (w) greater than a normal shingled track pitch width (p) of the magnetic tape; an actuator system for positioning the read write head laterally; and a control. The magnetic tape drive stores an overwrite erase format of non-shingled track pitch longitudinal pattern(s) whose pitch is greater than the normal shingled track pitch width (p); and, the control, in response to activation of overwrite erasure of the tape drive, operates the actuator system and the magnetic tape read write head to write non-data to magnetic tape in the stored overwrite erase format.

Abstract: A method of targeted corruption of user data in a shingled magnetic recording disk includes identifying user data on a Track_N targeted for corruption; identifying a readback centerline of the Track_N; identifying a readback centerline of an adjacent track to Track_N; acquiring user data of the adjacent track; and rewriting the user data of the adjacent track with an offset write centerline to overwrite magnetic material at the readback centerlines of both Track_N and the adjacent track.

Abstract: A circuit for use with a memory storage device including a magnetic storage medium and a write head operative to subject the magnetic storage medium to a magnetic field in response to an application of current to the write head, includes a write circuit operative to generate a write current supplied to the write head. The write current is characterized by a current waveform that reverses polarity in accordance with data to be stored on the magnetic medium. The circuit for use with the memory storage device further includes a degauss circuit operative to generate a degaussing current supplied to the write head. The degaussing current is characterized by a current waveform that oscillates between opposite polarities with an amplitude and a frequency that change over time.

Abstract: A structure for erasure of magnetic media in a hard drive includes a main field pole magnet polarized in a direction toward a drive spindle motor in the hard drive. At least two quadrature magnets are disposed adjacent the main field pole magnet and polarized in a direction toward the main field pole magnet. The main field pole magnet and the at least two quadrature magnets are shaped to provide a slot for insertion of the magnetic media. At least two inverse polarity magnets are disposed on portions of the main pole and quadrature magnets forming the slot. The inverse polarity magnets are polarized in a direction opposed to the direction of the main field pole magnet.

Abstract: A control circuit to provide a control current to control an amplitude of a write current in a magnetic media drive. The control circuit has an output circuit for providing the control current with an amplitude dependent on a bias voltage. A bias current path provides the bias voltage to the output circuit, and a current diverting circuit is connected to divert current from the bias current path. A programmable ramp voltage generator operates in response to a degauss enable signal, and a voltage-to-current converter receives the programmable ramp voltage to control the current diverting circuit to divert current from the bias current path at a rate determined by the programmable ramp voltage. The bias voltage and the write current decay according to the programmable ramp voltage. The write current decay can be made linear and independent of a beginning write current amplitude.

Abstract: One embodiment of the invention includes a system for writing data onto a magnetic disk. An output driver provides a first write current through a first output transistor in a first state and provides a second write current through a second output transistor in a second state. The first and second write currents can be provided to a disk write head to store opposing binary values, respectively. A bias current generator switches a first bias current between an intermediate voltage node in the second state and a first control node in the first state, and switches a second bias current between the intermediate voltage node in the first state and a second control node in the second state. The first and second bias currents can be provided to set a bias voltage at the first and second control nodes to bias the first and second output transistors, respectively.

Abstract: Data storage systems are provided. Data storage systems illustratively include a writing element and a recording medium. In some embodiments, the writing element generates first and second magnetization fields that respectively record first and second magnetization patterns to the recording medium. In some embodiments, the writing element is de-saturated between recording the first and second magnetization patterns.

Abstract: The present invention relates providing a magnetic data eraser that is capable of performing magnetizing process for magnetizing magnetic recording medium such as a hard disk drive (HDD) is easily and with reduced electric power. The magnetic data eraser includes: holding drawer means for holding a magnetic recording medium which means has a mounting tray for mounting the magnetic recording medium, wherein the mounting tray is inclined a predetermined value of degrees of angle; and magnetizing means for magnetizing the magnetic recording medium, wherein the magnetizing means is covered by a magnetizing coil and has a hollow body portion, the holding drawer means being accommodated in the hollow body portion, and the magnetic recording medium being placed on the mounting tray of the holding drawer means.

Abstract: A method and a storage system are provided for implementing fragmented stream handling for persistent media including shingled disk drives (SDDs). A plurality of Exception Regions for recording stream commands is defined for disk regions. One state is maintained in each of the Exception Regions including a free Exception Region, an active Exception Region, a recovery Exception Region and a used Exception Region. TRIM commands are issued by a host to the drive to indicate deleted content.

Abstract: A magnetic tape drive has a drive system to move a magnetic tape longitudinally; servo head(s) for reading servo band information from a magnetic tape as the magnetic tape is moved longitudinally; a magnetic tape read write head configured to read and to write the magnetic tape, having a data write width (w) greater than a normal shingled track pitch width (p) of the magnetic tape; an actuator system for positioning the read write head laterally; and a control. The magnetic tape drive stores an overwrite erase format of non-shingled track pitch longitudinal pattern(s) whose pitch is greater than the normal shingled track pitch width (p); and, the control, in response to activation of overwrite erasure of the tape drive, operates the actuator system and the magnetic tape read write head to write non-data to magnetic tape in the stored overwrite erase format.

Abstract: A bulk erase tool to erase a perpendicular media recording (PMR) disk of a disk drive is disclosed. The bulk erase tool comprises a housing to receive a disk drive and at least one of a first pair of magnets mounted in the housing to be positioned above the received disk drive to provide a magnetic field to erase the top side of the disk and a second pair of magnets mounted in the housing to be positioned below the disk drive to provide a magnetic field to erase the bottom side of the disk.

Abstract: An image processing device comprises an image data input means 2, an image data storage means 12 for storing the image data being input, an image data processing means 6 having multiple processing modes for outputting the stored image data, and a image data erasing means for erasing the image data stored in the storage means 12. The device further comprises erase count control means 8, 14 for controlling the number of times for erasing image data capable of having the number of times of erase set arbitrarily according to the security level required for each mode, and capable of having the set number of times of erase changed in mid-flow. Confidentiality is protected by performing erase operations repeatedly to the region storing the unnecessary image data according to the security level.

Abstract: A hard disk drive includes a chassis which supports a “sealed” housing containing a data storage magnetic disk, and read/write heads and actuator. The housing also contains an erasure device which generates a magnetic or other field or emanation for erasing the disk, so that the erasing field or emanation need not penetrate the sealed housing to effectuate erasure. A backup power supply provides power to the erasing device so that erasure can occur even in the absence of external power. A bus- or network-actuated arrangement couples power to the erasure device so that many hard drives may be simultaneously erased.

Abstract: A circuit for use with a memory storage device including a magnetic storage medium and a write head operative to subject the magnetic storage medium to a magnetic field in response to an application of current to the write head, includes a write circuit operative to generate a write current supplied to the write head. The write current is characterized by a current waveform that reverses polarity in accordance with data to be stored on the magnetic medium. The circuit for use with the memory storage device further includes a degauss circuit operative to generate a degaussing current supplied to the write head. The degaussing current is characterized by a current waveform that oscillates between opposite polarities with an amplitude and a frequency that change over time.

Abstract: Method and apparatus for detecting head disk interference (HDI). In accordance with some embodiments, a bias calibration circuit is adapted to respectively bypass or amplify a head disk interference (HDI) signal output from an HDI sensor responsive to a bias voltage adjusted according to a first control signal. A detection circuit is adapted to compare a swing range of a signal output from the bias calibration circuit and a swing range of a reference signal, and to output the first control signal responsive to said comparison.

Abstract: The present invention relates providing a magnetic data eraser that is capable of performing magnetizing process for magnetizing magnetic recording medium such as a hard disk drive (HDD) is easily and with reduced electric power. The magnetic data eraser includes: holding drawer means for holding a magnetic recording medium which means has a mounting tray for mounting the magnetic recording medium, wherein the mounting tray is inclined a predetermined value of degrees of angle; and magnetizing means for magnetizing the magnetic recording medium, wherein the magnetizing means is covered by a magnetizing coil and has a hollow body portion, the holding drawer means being accommodated in the hollow body portion, and the magnetic recording medium being placed on the mounting tray of the holding drawer means.

Abstract: Approaches for inducing a magnetic bias in a magnetic recording disk. A biasing apparatus comprises a soft magnetic material member having a shape comprising two opposing recesses, denoted an upper recess and a lower recess. A first magnet is disposed within the upper recess and a second magnet disposed within the lower recess. An air gap exists between the first magnet and the second magnet. An opening in the soft magnetic material member is sized to accommodate at least a portion of the magnetic recording disk between the first magnet and the second magnet. The magnetic field produced by both the first magnetic and the second magnetic flows (a) in the same direction, and (b) perpendicular to the plane of the magnetic recording disk. Using this approach, magnetic material on the disk, such as magnetic islands of a bit pattern media, may be erased and polarized in the same direction.

Abstract: In one embodiment, a data storage system includes a magnetic head having a main magnetic pole and a wrap around shield positioned around the main magnetic pole at an ABS thereof, a magnetic medium, a drive mechanism for passing the magnetic medium over the magnetic head, and a controlling mechanism electrically coupled to the magnetic head for controlling operation of the magnetic head that initiates rewriting of information of a recording track of the magnetic medium if a recording magnetic field applied to the recording track exceeds a threshold. In another embodiment, a method includes writing data to a first track of a magnetic medium using a magnetic head, determining characteristics consistent with data degradation from tracks adjacent to the first track and far tracks away from the first track using a controlling mechanism, and rewriting data in tracks determined to be degraded due to ATI and/or FTI.

Abstract: A thermal-assisted magnetic recording (TAMR) system is described which generates laser-pulse signals from the write data line. Additionally, training signals for initial synchronization are fed to the preamp IC using the write data line during servo read cycle. This requires no increase in the number of wires going to read-write driver chip (R/W IC) (preamp). In embodiments of the invention the R/W IC also includes registers that are set using serial data from the system electronics to influence the characteristics of the drive signal to the laser.

Abstract: One embodiment of the invention includes a system for writing data onto a magnetic disk. An output driver provides a first write current through a first output transistor in a first state and provides a second write current through a second output transistor in a second state. The first and second write currents can be provided to a disk write head to store opposing binary values, respectively. A bias current generator switches a first bias current between an intermediate voltage node in the second state and the first control node in the first state, and switches a second bias current between the intermediate voltage node in the first state and the second control node in the second state. The first and second bias currents can be provided to set a bias voltage at the first and second control nodes to bias the first and second output transistors, respectively.

Abstract: A magnetic data eraser includes a holding drawer means for holding a magnetic recording medium which means has a mounting tray for mounting the magnetic recording medium, wherein the mounting tray is inclined a predetermined value of degrees of angle. The magnetic data eraser further includes a magnetizing means for magnetizing the magnetic recording medium, wherein the magnetizing means is covered by a magnetizing coil and has a hollow body portion. The holding drawer means being accommodated in the hollow body portion, and the magnetic recording medium being placed on the mounting tray of the holding drawer means.

Abstract: According to one embodiment, a magnetic disk drive comprises a write count memory, a read offset setting module and a controller. The write count memory stores a write count for each track or for each zone on a disk. The read offset setting module sets, in accordance with a write count for an adjacent track to a target track or for a zone to which the adjacent track belongs, an offset from a predetermined position on the target track in a read position in which a head is to be positioned when the head is positioned on the target track for data read. The write count is stored in the write count memory. The controller positions the head in a position shifted from the predetermined position by the set offset.

Abstract: The disclosure is directed to a method for creating a remnant magnetization on a magnetic tape medium. The magnetic tape is first substantially demagnetized, e.g., erased, by an erasure unit having multiple magnetic elements of alternating polarity. The erased magnetic tape is then passed by a bias magnet that creates a remnant magnetization on the magnetic tape. The remnant magnetized magnetic tape is then passed through a servo write head that writes servo patterns to the remnant magnetized magnetic tape. The bias magnet may be housed within the erasure unit or within a bias unit, and the distance between the bias magnet and the tape path of the magnetic tape may be adjustable to create the desired remnant magnetization on the magnetic tape. The remnant magnetization created on the magnetic tape may be greater than 20 percent to reduce defects in the servo pattern written to the magnetic tape.