Method and apparatus for magnetically recording data having three or more states per unit of data

Abstract

The present application discloses a method and apparatus for magnetically recording data having three or more states per unit of data. Two or more different recording currents are applied to a write coil of a recording head. A first current of the two or more currents is a positive current, and a second current of the two or more currents is a negative current. In response to the application of the two or more different recording currents, a data stream is recorded to a zone of a moving continuous magnetic recording medium such that each zone has three or more magnetic states. The three or more magnetic states can be read from the continuous magnetic recording medium via a magnetic read transducer to recover the data stream.

Description

Summary of the Invention

[0001] The present disclosure relates to a method and apparatus for magnetic recording of data having three or more data states. In one embodiment, two or more different recording currents are applied to a write coil of a recording head. A first current of the two or more currents is a positive current, and a second current of the two or more currents is a negative current. In response to the application of the two or more different recording currents, a data stream is recorded to a zone of a moving continuous magnetic recording medium such that each zone has three or more magnetic states. The three or more magnetic states are read via a magnetic read transducer from the continuous magnetic recording medium to recover the data stream.

[0002] In another embodiment, a binary data stream is converted to a data stream having three or more states per unit of data. The data stream is recorded to a zone of a moving continuous magnetic recording medium via two or more different recording currents such that each zone has three or more magnetic states. Each of the magnetic states corresponds to one of the three or more states per unit of data. The three or more magnetic states can be read via a magnetic read transducer from the continuous magnetic recording medium to recover the data stream. The recovered data stream is then converted to a binary output stream. These and other features and aspects of the various embodiments will be understood in view of the following detailed discussion and the drawings. Brief Description of the Drawings

[0003] The following discussion refers to the following drawings, where like reference numerals may be used to identify similar / same components in multiple drawings.

[0004] Figure 1 is a perspective view of a slider assembly according to an example embodiment;

[0005] Figure 2 is a diagram schematically depicting a data storage device according to an example embodiment;

[0006] Figure 3 and 4 is a graph showing a data storage signal according to an example embodiment;

[0007] Figure 5 and 6 is a hysteresis loop graph showing the performance of a recording medium according to an example embodiment;

[0008] Figure 7 、 8 and 9 are graphs showing recording signal characteristics according to an example embodiment;

[0009] Figure 10 is a graph showing an experimental read signal in a data storage device according to an example embodiment;

[0010] Figures 11 - 14 is a diagram of a recorded signal circuit according to an example embodiment;

[0011] Figure 15 is a block diagram of a device according to an example embodiment; and

[0012] Figure 16 and 17 is a flowchart of a method according to an example embodiment. DETAILED DESCRIPTION

[0013] The present disclosure generally relates to data storage devices that utilize magnetic storage media such as magnetic disks. For example, a hard disk drive (HDD) unit includes one or more magnetic disks that are written to and read from using a read / write head attached to the end of an actuator arm located above the tracks on the magnetic disk. To record data, the read / write head uses a magnetic coil to generate a magnetic field that is directed to the magnetic disk surface via a write pole. To read data, the read / write head senses changes in the magnetic field via a sensor such as a magnetoresistive stack maintained near the moving magnetic disk. Disk drives typically have multiple heads, one for each magnetic disk surface.

[0014] Disk drives that use only a write coil and a write pole to record data are sometimes referred to as conventional magnetic recording (CMR) drives. Modern CMR drives typically employ perpendicular magnetic recording (PMR), where the magnetic field is aligned perpendicular to the magnetic disk surface. This allows for a higher areal density (AD) compared to a scheme where the magnetic field is parallel to the magnetic disk surface. Some drives can employ different track writing formats to increase the AD, such as shingled magnetic recording (SMR) and interleaved magnetic recording (IMR), where adjacent tracks are laminated on top of each other during writing. Other techniques for increasing the AD include heat-assisted magnetic recording (HAMR) and microwave-assisted magnetic recording (MAMR). These techniques use additional components (e.g., a laser for HAMR and a spin torque oscillator for MAMR) to affect the size of the recorded hot spots so that smaller bits can be written to the magnetic disk compared to CMR drives.

[0015] Regardless of the technology used to record data onto a disk, it is desirable to increase the areal density (AD) such that a single disk can store an increasingly large amount of data while reducing the cost per unit of data. The advanced recording technologies described above (e.g., SMR, IMR, HAMR, MAMR) attempt to increase the AD by reducing the area in which a unit of data is stored, such as a single bit value of zero or one stored in a region having a negative or positive magnetic orientation. In the embodiments described herein, the data storage device increases the AD by increasing the amount of data that can be stored in a given region, e.g., having more than two states per recording region. The region storing a single unit of data is called a bit in binary recording, and in the present disclosure, the bit is extended such that it can store more than two states. A device capable of storing n > 2 states per region / bit can store n / 2 times more data per unit area than a binary storage device.

[0016] Reference is now made Figure 1 , a perspective view shows a read / write head 100 according to an example embodiment. The read / write head 100 can be used in a magnetic data storage device, such as a hard disk drive. The read / write head 100 may also be interchangeably referred to herein as a slider, a write head, a read head, a recording head, etc. The read / write head 100 has a slider body 102 that has a read / write transducer held near the surface of a magnetic recording medium (not shown), such as a disk, at a trailing edge 104.

[0017] The illustrated read / write head 100 can be a CMR head, or can be configured for a HAMR or MAMR device. In the latter case, the head includes additional components that assist the read / write transducer 108 during recording. These components are collectively indicated by the box 106 and can include a laser diode and a waveguide in a HAMR implementation, or a spin torque oscillator in a MAMR device.

[0018] The writer of the read / write head 100 is configured to write more than two different states onto the recording medium, which is referred to herein as multilevel recording or multilevel writing. Two or more states are discrete because the number of states is predefined and the physical characteristics of the states are at known levels or values. The reader of the read / write head 100 is configured to read back two or more states, which is referred to herein as multilevel reading. Multilevel reading and recording are enabled by a processing circuit 120 that will be discussed in further detail below. Note that in some embodiments, the read / write head 100 can be substantially similar to a binary read / write head. In other embodiments, the read / write head can have specific features that improve multilevel reading and writing performance, such as a specially tuned read transducer that is sensitive to more than two magnetic states / levels. However, those specific multilevel features of the read / write head 100 are outside the scope of the present disclosure.

[0019] In Figure 2In the figure, the schematic diagram schematically shows aspects of a data storage device according to an example embodiment. A write circuit 200 applies two or more different recording currents 206, 207 to a write pole 202 of a recording head 204. A first current 206 among the two or more currents is a positive current, and a second current 207 among the two or more currents is a negative current. Note that a third current 208, which is a zero or near-zero current, is also shown here.

[0020] For the purposes of this disclosure, a zero or near-zero current is a current that has the intended effect of a zero or neutral field applied to the recording medium, but there may be a small amount of current applied via circuit 200 to overcome electrical bias, hysteresis, etc. As will be described in more detail below, some embodiments may use only two non-zero currents, and other embodiments may use more than two non-zero currents. Similarly, some embodiments may not use a zero or near-zero current. At least one of the currents (e.g., current 206) will be at or near the maximum positive value, and another of the currents (e.g., current 207) will be at or near the maximum negative value. The magnitudes of the maximum negative current and the maximum positive current may be the same or different.

[0021] Data 210 is recorded onto regions 211, 212 of a moving continuous magnetic recording medium 214 using a write pole such that each region 211, 212 has more than three or more magnetic states corresponding to two or more recording currents 206, 207. In this example, the states are indicated by ternary values 210a-c (0, 1, 2) of the data, but other representations of the data 210 may be used (e.g., -1, 0, 1). A read transducer 216 reads three or more magnetic states 210a-c from the continuous magnetic recording medium 214 via a magnetic read transducer 216 to recover the data, as indicated by a read circuit 218 that extracts a data signal 220 that is processed by a controller 222 to recover the stored data.

[0022] From a physical perspective, one challenge in multilevel magnetic recording is how to define different magnetization levels for a single region in a magnetic recording medium. Several possible schemes for achieving this are described below, each of which is applicable to some combination of PMR, MAMR, and HAMR.

[0023] In one embodiment, the magnetization of the magnetic recording medium is controlled only by an electrical signal in a coil around the write pole, such as PMR. Two levels can be defined by applying a maximum positive current or a maximum negative current. The maximum current limit can be defined based on thermal, electromigration, or other damage to the magnetic writer or by the limit of a preamplifier used to drive the magnetic writer. Other levels associated with intermediate states can be defined by intermediate current values between these two limits, including zero or near-zero currents.

[0024] Non - limiting examples define three possible states: one state is defined by a writer current of - 60 mA, another state is defined by a writer current of + 60 mA, and the third state is defined by not applying current to the writer (0 mA, or a small bias current, e.g., < 3 mA positive or negative). In Figure 3 a similar scheme is represented by signal levels 206 - 208. Another non - limiting example would be to define four possible states using writer currents of - 60 mA, - 20 mA, + 20 mA, and + 60 mA respectively. The signal 300 in Figure 3 is shown using this scheme. Yet another non - limiting example would be to use writer currents of - 60 mA, - 30 mA, 0 mA, + 30 mA, and + 60 mA to define five possible states. The signal 400 in Figure 4 is shown using this scheme.

[0025] Note that although the foregoing examples contain equally - spaced writer currents corresponding to different states to be encoded, depending on the detailed characteristics of the write pole, coil, reader, media stack, etc., equally - spaced levels may not provide the best SNR. For example, for a magnetic recording medium with a hysteresis loop as shown in Figure 5 a four - level recording scheme can use magnetic writer currents of - 60 mA, - 15 mA, + 15 mA, and + 60 mA respectively to record four levels, thus obtaining better results.

[0026] There are several possible ways to generate currents of multiple levels to a magnetic writer. A multi - level analog writer driver can be implemented in a pre - amplifier. Alternatively, the outputs of several different drivers that generate two - level (digital) signals can be combined through additional circuitry. It should also be noted that for binary magnetic recording, a magnetic recording pole with a relatively square hysteresis loop and low coercivity is likely to be optimal. For this embodiment of multi - level magnetic recording, a narrow, skewed hysteresis loop can be used, as shown in Figure 6

[0027] In a second embodiment, a device having the features of the first embodiment incorporates additional features in the magnetic writer signal. Overshoot pulses can be applied to transitions between some or all level combinations in multi - level recording, such as the pulses used in PMR and HAMR to improve the transition quality of conventional binary data. Undershoot pulses can additionally be used to control the magnetic state of the write pole. For example, in the case of three - level recording, undershoot pulses can be used to ensure that the write pole is demagnetized when recording a zero - level mark. In Figure 7 some examples of overshoot pulses (e.g., 700, 701) and undershoot pulses (e.g., 702, 703) in the recording waveform are shown.

[0028] ​The third embodiment utilizes the feature of reliably recording zero or near-zero signals onto a recording medium. For example, in a write pole design optimized for recording binary data (but to some extent for any write pole), it may be difficult to consistently demagnetize the pole to the correct level, such as for the case of recording a zero state when an odd number of levels are recorded. This embodiment solves this difficulty by using an AC magnetic write signal with a frequency higher than the data rate to record the intermediate level.

[0029] In one non-limiting example, information is recorded in three states corresponding to two current levels. Figure 8 An exemplary waveform of the magnetic write signal used in this example is shown in the graph. For two states (1 and -1), a constant magnetic write current of, for example, ±60 mA is used (there may also be overshoot and / or undershoot pulses). For the third state, i.e., the intermediate level (0), the writer signal is a sine wave or square wave with an amplitude of 60 mA. It should be noted that in order to avoid unnecessary transition shifts that would degrade the bit error rate, the frequency of the AC erase signal used to define the zero state can be selected such that the polarity of the AC erase signal at the start of the zero-level mark matches the polarity of the previously written mark, and similarly, the polarity of the AC erase signal at the end of the zero-level mark matches the polarity of the next mark to be written.

[0030] Note that the use of the AC erase signal need not be limited to the zero state (e.g., zero magnetic field) of a recording scheme with an odd number of levels. In Figure 9 Another example shown, a four-level scheme is used, where two states (-1.5, 1.5) are defined using DC ±60 mA writer current (there may also be overshoot and / or undershoot pulses), and two intermediate states (-0.5, 0.5) are defined using an AC sine wave or square wave with an amplitude of 10 mA superimposed on the DC ±20 mA writer current.

[0031] In Figure 10 the figure shows experimental readback signals of three-state patterns recorded on a HAMR medium using different schemes. The data represented in recording track 1000 is recorded using the overshoot / undershoot scheme as shown in Figure 7 and the data represented in recording track 1002 is recorded using the high-frequency erase scheme as shown in Figure 8 Note that recording tracks 1000, 1002 are arbitrary waveform samples and do not represent the same recorded data. Note that compared to recording track 1000, the zero state is better defined via the high-frequency AC erase in recording track 1002, e.g., in regions 1008 and 1010 for the latter compared to regions 1004 and 1006 for the former.

[0032] The embodiments described above allow a recording device to record multiple states of a magnetic field in a magnetic recording medium using a magnetic write current of multiple (more than two) levels. In PMR, since the rewrite characteristics of the intermediate states may not be as good as those of the states defined by the maximum write current of either polarity, the quality of the recorded signal can be improved by first erasing the track to be written with a first alternating current (AC). For example, two-pass recording can be used, where the same head (or different heads, such as in a multi-actuator drive) first erases the track before the recording pass. In other embodiments, a second write coil located on the same head or the same head gimbal assembly can be located at a position to erase the track as the recording head writes to the track. This can be used in place of, for example Figure 8 the embodiment shown in which the erase signal is included in the recording signal.

[0033] In MAMR and HAMR, the energy assist mechanism may be sufficient to remove previously recorded data before or during writing without dedicated AC erasure. Typically, this is due to neutralizing the magnetic state of the recording medium in the heat source (HAMR) or microwave source (MAMR) and in a zero-current or near-zero-current state.

[0034] The medium itself can be tuned to better support multiple levels per bit. There are many possible examples for different recording technologies. In PMR, multiple magnetic layers with different coercivities can be used, such that the layer with low coercivity is recorded by write currents of some or all levels, while the levels with high coercivity are recorded only by large-amplitude write currents. In MAMR, the medium can be tuned such that, in combination with microwave assistance, the slope of the M-H hysteresis loop is shallower, allowing multiple levels to be recorded in a single write and a multi-level signal to be applied to the writer. The medium can comprise multiple uncoupled independent layers that can be individually addressed during different writes. In HAMR, multiple magnetic layers with similar Curie temperatures but different coercivities can be used, such that in a single write using a single constant laser power, multiple levels can be recorded using a multi-level signal applied to the magnetic writer.

[0035] Readers such as giant magnetoresistive (GMR) or tunneling magnetoresistive (TMR) readers can be used to read multi-level data from the medium in a manner similar to reading conventional binary data recorded in a hard disk drive. Figure 10 The recorded track 1000 in

[0036] The magnetic properties of the reader can also be adjusted to read multi-level data. For example, it may be advantageous to provide the reader with a shallower electrical response to an external field, which will provide a greater separation between the voltage levels in the read signal associated with the different magnetization levels recorded in the medium. New methods can also be developed to decode the recorded data from the readback signal. One method is to use a threshold detector, where for N levels per media segment, N - 1 levels are defined as the thresholds that separate these levels in the readback signal, and the information is decoded by comparing the readback voltage at a given point with this set of thresholds.

[0037] More powerful decoding techniques may perform better for multi-level data, such as those applicable decoding techniques from partial response maximum likelihood (PRML), low density parity check (LDPC), Reed - Solomon codes, Viterbi algorithm, etc. Note that since ordinary user data can initially be in binary format, additional processing can be used both before writing and after reading to convert the binary user data into the correct multi-level format for writing and then back to binary format after reading.

[0038] An analog writer driver can be implemented in the preamplifier. Alternatively, the outputs of several different drivers that produce a two-level (digital) signal can be combined through additional circuitry. In Figure 11 , the block diagram shows a circuit for generating a multi-level writer waveform and a laser signal according to an example embodiment. In this example, two writer data streams 1102, 1103 are generated from the marker output of an arbitrary waveform generator (AWG) 1100.

[0039] The write data streams 1102, 1103 are passed to two separate preamplifier integrated circuits (ICs) 1104, 1105, which output the signals to the interface 1106 of the recording head. One preamplifier 1104 is connected to the writer coil of the recording head with the same polarity, while the other preamplifier 1105 is connected with the opposite polarity. This connection scheme can use the existing preamplifiers in the driver to form the desired writer waveform. Optionally, a laser signal 1108 can also be generated from the analog output of the AWG for HAMR recording. The signal 1108 is amplified via a laser section 1110, which outputs the signal to the laser pad of the recording head interface 1106. Note that in this figure and subsequent figures, the driver section of the spin torque oscillator can replace the shown laser section, such that in addition to HAMR, these circuits can also be used for MAMR storage devices.

[0040] In Figure 12In [the figure], the block diagram shows a circuit for generating a multi-level writer waveform and a laser signal according to another exemplary embodiment. In this example, for instance, two writer data streams 1202, 1203 are provided from an encoder circuit to a preamplifier 1200. The write data streams 1202, 1203 are passed to two separate preamplifier sections 1204, 1205, which output signals to an interface 1206 of a recording head. The sections 1204, 1205 can be part of a single circuit package or separate circuit chips / packages. One preamplifier section 1204 is connected to the writer coil of the recording head with the same polarity, while the other preamplifier section 1205 is connected with the opposite polarity. This connection scheme can use the existing preamplifiers in the driver to form the desired writer waveform. The preamplifier 1200 may also include a laser amplifier 1210 for HAMR recording, which outputs a signal to a laser pad of the recording head interface 1206.

[0041] In Figure 13 [the figure], the block diagram shows a circuit for generating a multi-level writer waveform and a laser signal according to another exemplary embodiment. In this example, a single writer data stream 1302 is provided to a writer section 1304 of a preamplifier 1300. The writer section 1304 generates a multi-level writer waveform (e.g., three or more discrete analog or digital levels), which is input to a write coil via an interface 1306 of a recording head. In this example, the data stream 1302 can be multi-level, but the preamplifier 1300 can further adjust the multi-level output waveform, e.g., adding overshoot and undershoot, adding an erase signal for certain values, etc. The preamplifier 1300 may also include a laser section 1310 that outputs a signal to a laser pad of the recording head interface 1306.

[0042] In Figure 14 [the figure], the block diagram shows a circuit for generating a multi-level writer waveform without a laser according to an exemplary embodiment. In this example, a single writer data stream 1402 is provided to a writer section 1404 of a preamplifier 1400. The writer section 1404 generates a multi-level writer waveform, which is input to a write coil via an interface 1406 of a recording head. In this example, the data stream 1402 can be multi-level, but the preamplifier 1400 can further adjust the multi-level output waveform, e.g., adding overshoot and undershoot, adding an erase signal for certain values, etc. In this example, the preamplifier 1400 does not include a laser section and thus can be used with PMR data storage. In such an arrangement, high-frequency AC erasure can be used to generate a zero state as described above.

[0043] In Figure 15In [the figure], the block diagram shows a data storage device 1500 according to an example embodiment. The control logic circuit 1502 of the device 1500 includes a system controller 1504 that processes read and write commands and associated data from a host device 1506, which is coupled via a host interface 1505. The host device 1506 can include any electronic device communicatively coupled to store data and retrieve data from the data storage device, such as a computer, a storage controller card, etc. The system controller 1504 is coupled to a read / write channel 1508 that reads from and writes to the surface of a disk 1510. The disk 1510 is a continuous magnetic recording medium, such as without using fabricated patterns or structures as in patterned media.

[0044] The read / write channel 1508 generally converts data between digital signals processed by the controller 1504 and analog signals conducted by one or more read / write heads 1512 during a read operation. To facilitate the read operation, the read / write channel 1508 can include analog and digital circuitry, such as a preamplifier, a filter, a decoder, a digital-to-analog converter, a timing correction unit, etc. The read / write channel 1508 also provides servo data read from a servo wedge 1514 on the disk 1510 to a servo controller 1516. The servo controller 1516 uses these signals to provide a voice coil motor control signal 1517 to a VCM 1518. The VCM 1518 rotates a magnetic arm 1520 in response to the voice coil motor control signal 1517, and the read / write head 1512 is mounted on the magnetic arm.

[0045] The data within the servo wedge 1514 is used to detect the position of the read / write head 1512 relative to the disk 1510. The servo controller 1516 uses the servo data to move the read / write head 1512 to an addressed track 1522 and lock (seek mode) on the disk 1510 in response to a read / write command. When writing data to and / or reading data from the disk 1510, the servo data is also used to keep the read / write head 1512 aligned with the track 1522 (track following mode).

[0046] The read / write channel 1508 is a multi-level recording state channel that applies two or more different recording currents to the write coil of the head 1512 to record data into a sector / bit of the disk 1510 such that each sector / bit has three or more magnetic states. The recording currents include a negative current, a positive current, and can include one or more currents between the positive current and the negative current to include zero or near-zero current. The head 1512 also includes a read converter, and the read / write channel 1508 facilitates reading three or more magnetic states from the disk 1510 to recover the recorded data.

[0047] Since host data is typically binary, data storage device 1500 includes a multilevel encoder / decoder 1507 that converts between the binary encoding format used by data controller 1504 and host 1506. Typically, encoder / decoder 1507 converts between a binary data stream and a multilevel data stream that stores data in three or more states per unit (e.g., bit) of data. Note that servo controller 1516 can also utilize multilevel recording and reading of servo wedge 1514, and thus, servo data can also be processed by multilevel recording components 1507, 1508.

[0048] In Figure 16 the flow diagram illustrates a method according to an example embodiment. The method involves 1600 applying two or more different recording currents to a write coil of a recording head. The first current of the two or more currents is a positive current, and the second current of the two or more currents is a negative current. In response to the two or more different recording currents, 1601 records a data stream to a zone of a moving continuous magnetic recording medium such that each zone has three or more magnetic states. 1602 reads the three or more magnetic states from the continuous magnetic recording medium via a magnetic read transducer to recover the data stream.

[0049] In Figure 17 the flow diagram illustrates a method according to an example embodiment. The method involves 1700 converting a binary data stream to a data stream having three or more states per unit of data. 1701 records the data stream to a zone of a moving continuous magnetic recording medium via two or more different recording currents such that each zone has three or more magnetic states. Each of the magnetic states corresponds to one of the three or more states per unit of data. 1702 reads the three or more magnetic states from the continuous magnetic recording medium via a magnetic read transducer to recover the data stream. 1703 then converts the recovered data stream to a binary output stream.

[0050] The various embodiments described above may be implemented using circuits, firmware, and / or software modules that interact to provide a particular result. Those skilled in the art can readily implement such described functionality at a modular level or as a whole using knowledge well known in the art. For example, the flowcharts and control diagrams shown herein may be used to create computer-readable instructions / code for execution by a processor. Such instructions may be stored on a non-transitory computer-readable medium and transmitted to the processor for execution, as known in the art. The structures and programs shown above are merely representative examples of embodiments that may be used to provide the functionality described above.

[0051] Unless otherwise indicated, all numbers expressing feature sizes, amounts, and physical properties used in the specification and claims are to be understood as being modified in all instances by the term "about." Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings disclosed herein. The numerical ranges set forth by endpoints use all numbers within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5) and any range within that range.

[0052] For purposes of illustration and description, the foregoing description of example embodiments has been presented herein. It is not intended to be exhaustive or to limit the embodiments to the precise forms disclosed. Many modifications and variations are possible in light of the above teachings. Any or all features of the disclosed embodiments may be applied singly or in any combination, merely for purposes of illustration and not limitation. It is intended that the scope of the invention be defined not by this detailed description, but by the claims appended hereto.

[0053] Further examples:

[0054] Example 1. A method comprising: applying two or more different recording currents to a write coil of a recording head, a first current of the two or more currents being a positive current and a second current of the two or more currents being a negative current; in response to the application of the two or more different recording currents, recording a data stream to a zone of a moving continuous magnetic recording medium such that each zone has three or more magnetic states; and reading the three or more magnetic states from the continuous magnetic recording medium via a magnetic read transducer to recover the data stream.

[0055] Example 2. The method of Example 1, wherein the two or more currents include a negative current, a positive current, and a zero or near-zero current.

[0056] Example 3. The method of Example 2, wherein the recording of the data stream is assisted by a heat source or a microwave source that neutralizes the magnetic states corresponding to the zero or near-zero current.

[0057] Example 4. The method of Example 1, wherein the two or more different recording currents include three or more currents ranging from a maximum positive current to a maximum negative current, and wherein the three or more currents are not equally spaced within the range to account for the hysteresis of the continuous magnetic recording medium.

[0058] Example 5. The method according to Example 1, wherein the three or more magnetic states include: a positive maximum field, which corresponds to a positive maximum current; a negative maximum field, which corresponds to a negative maximum current; and an intermediate field, which is between the positive maximum field and the negative maximum field.

[0059] Example 6. The method according to Example 5, wherein the intermediate field is set via an alternating current erasure current having an erasure frequency higher than the data frequency.

[0060] Example 7. The method according to Example 1, wherein the two or more currents are generated by combining two or more two-level digital signals from two or more preamplifier circuits.

[0061] Example 8. The method according to Example 1, further comprising receiving binary data and converting the binary data into the data stream, the data stream having three or more states per unit of data, each of the three or more states corresponding to one of the three or more magnetic states.

[0062] Example 9. A data storage device, comprising: an interface circuit with a recording head, the recording head having a write coil and a magnetic read transducer; and a controller coupled to the interface circuit and configured to: apply two or more different recording currents to the write coil to record data into a zone of a moving continuous magnetic recording medium such that each zone has three or more magnetic states, a first current of the two or more currents being a positive current and a second current of the two or more currents being a negative current; and read the three or more magnetic states from the continuous magnetic recording medium via the magnetic read transducer to recover the data.

[0063] Example 10. The data storage device according to Example 9, wherein the two or more currents include a negative current, a positive current, and a zero or near-zero current.

[0064] Example 11. The data storage device according to Example 10, the recording head includes a heat source or a microwave source for assisting in recording to the recording medium, and the controller is further configured to neutralize the magnetic state corresponding to the zero or near-zero current via the heat source or the microwave source.

[0065] Example 12. The data storage device according to Example 9, wherein the two or more different recording currents include three or more currents ranging from a maximum positive current to a maximum negative current, and wherein the three or more currents are not equally spaced within the range to account for the hysteresis of the continuous magnetic recording medium.

[0066] Example 13. The data storage device according to Example 9, wherein the three or more magnetic states include: a positive maximum field, which corresponds to a positive maximum current; a negative maximum field, which corresponds to a negative maximum current; and an intermediate field, which is between the positive maximum field and the negative maximum field.

[0067] Example 14. The data storage device according to Example 13, wherein the intermediate field is set via an alternating current erasure current having an erasure frequency higher than the frequency of the data.

[0068] Example 15. The data storage device according to Example 9, further comprising two or more preamplifier circuits that output a two-level digital signal, the digital signals being combined to generate the two or more currents.

[0069] Example 16. The data storage device according to Example 9, wherein the controller is further configured to receive binary data and convert the binary data into a stream having three or more states per unit of data, each of the three or more states per unit of data corresponding to one of the three or more magnetic states.

[0070] Example 17. A method, comprising: converting a binary data stream into a data stream having three or more states per unit of data; recording the data stream onto a zone of a moving continuous magnetic recording medium via two or more different recording currents such that each zone has three or more magnetic states, each of the magnetic states corresponding to one of the three or more states per unit of data; reading the three or more magnetic states from the continuous magnetic recording medium via a magnetic read transducer to recover the data stream; and converting the recovered data stream into a binary output stream.

[0071] Example 18. The method according to Example 17, wherein the two or more different recording currents include three or more currents ranging from a maximum positive current to a maximum negative current, and wherein the three or more currents are not equally spaced within the range to account for the hysteresis of the continuous magnetic recording medium.

[0072] Example 19. The method according to Example 17, wherein the three or more magnetic states include: a positive maximum field, which corresponds to a positive maximum current; a negative maximum field, which corresponds to a negative maximum current; and an intermediate field, which is between the positive maximum field and the negative maximum field.

[0073] Example 20. The method according to Example 19, wherein the intermediate field is set via an alternating current erasure current having an erasure frequency higher than the data frequency.

Claims

1. A method, comprising: Applying two or more different recording currents to a write coil of a recording head, a first current of the two or more currents being a positive current and a second current of the two or more currents being a negative current; In response to the application of the two or more different recording currents, recording a data stream to a zone of a moving continuous magnetic recording medium such that each zone has three or more magnetic states; And Reading the three or more magnetic states from the continuous magnetic recording medium via a magnetic read transducer to recover the data stream.

2. The method according to claim 1, wherein the two or more currents include a negative current, a positive current, and a zero or near-zero current.

3. The method according to claim 2, wherein the recording of the data stream is assisted by a heat source or a microwave source that neutralizes the magnetic state corresponding to the zero or near-zero current.

4. The method according to claim 1, wherein the two or more different recording currents include three or more currents ranging from a maximum positive current to a maximum negative current, and wherein the three or more currents are not equally spaced within the range to account for hysteresis of the continuous magnetic recording medium.

5. The method according to claim 1, wherein the three or more magnetic states include: A positive maximum field, which corresponds to the positive maximum current; A negative maximum field, which corresponds to the negative maximum current; And An intermediate field, which is between the positive maximum field and the negative maximum field.

6. The method according to claim 5, wherein the intermediate field is set via an alternating current erasure current having an erasure frequency higher than the data frequency.

7. The method according to claim 1, wherein the two or more currents are generated by combining two or more two-level digital signals from two or more preamplifier circuits.

8. The method according to claim 1, further comprising receiving binary data and converting the binary data into the data stream, the data stream having three or more states per unit of data, each of the three or more states corresponding to one of the three or more magnetic states.

9. A data storage device, comprising: An interface circuit with a recording head having a write coil and a magnetic read transducer; And A controller coupled to the interface circuit and configured to: Apply two or more different recording currents to the write coil to record data to a zone of a moving continuous magnetic recording medium such that each zone has three or more magnetic states, a first current of the two or more currents being a positive current and a second current of the two or more currents being a negative current; and Read the three or more magnetic states from the continuous magnetic recording medium via the magnetic read transducer to recover the data.

10. The data storage device according to claim 9, wherein the two or more currents include a negative current, a positive current, and a zero or near-zero current.

11. The data storage device according to claim 10, wherein the recording head includes a heat source or a microwave source for assisting in recording to the recording medium, and the controller is further configured to neutralize, via the heat source or the microwave source, the magnetic states corresponding to the zero or near-zero current.

12. The data storage device according to claim 9, wherein the two or more different recording currents include three or more currents ranging from a maximum positive current to a maximum negative current, and wherein the three or more currents are not equally spaced within the range to account for the hysteresis of the continuous magnetic recording medium.

13. The data storage device according to claim 9, wherein the three or more magnetic states include: a positive maximum field, which corresponds to a positive maximum current; a negative maximum field, which corresponds to a negative maximum current; and an intermediate field, which is between the positive maximum field and the negative maximum field.

14. The data storage device according to claim 13, wherein the intermediate field is set via an alternating current erasure current having an erasure frequency higher than the frequency of the data.

15. The data storage device according to claim 9, further comprising two or more preamplifier circuits that output a two-level digital signal, the digital signals being combined to generate the two or more currents.

16. The data storage device according to claim 9, wherein the controller is further configured to receive binary data and convert the binary data into a stream having three or more states per unit of data, each of the three or more states per unit of data corresponding to one of the three or more magnetic states.

17. A method, comprising: converting a binary data stream into a data stream having three or more states per unit of data; recording the data stream to a zone of a moving continuous magnetic recording medium via two or more different recording currents such that each zone has three or more magnetic states, each of the magnetic states corresponding to one of the three or more states per unit of data; reading the three or more magnetic states from the continuous magnetic recording medium via a magnetic read transducer to recover the data stream; and converting the recovered data stream into a binary output stream.

18. The method according to claim 17, wherein the two or more different recording currents include three or more currents ranging from a maximum positive current to a maximum negative current, and wherein the three or more currents are not equally spaced within the range to account for the hysteresis of the continuous magnetic recording medium.

19. The method according to claim 17, wherein the three or more magnetic states include: a positive maximum field, which corresponds to a positive maximum current; a negative maximum field, which corresponds to a negative maximum current; and an intermediate field, which is between the positive maximum field and the negative maximum field.

20. The method according to claim 19, wherein the intermediate field is set via an alternating current erasure current having an erasure frequency higher than the data frequency.

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