KR20140014016A - Heat assisted magnetic recording device with pre-heated write element - Google Patents

Abstract

The apparatus includes a writing element configured to apply a magnetic field to write data to a portion of the heating magnetic recording medium in response to an activation current. The energy source is configured to heat the portion of the medium magnetized by the writing element. The preheat activation current is applied to the write element for an interval before writing data to the portion of the medium. The preheat activation current prevents data from being written to the medium and induces at least one of the write element and the driver circuit to thermal equilibrium prior to writing the data to the portion.

Description

 HEAT ASSISTED MAGNETIC RECORDING DEVICE WITH PRE-HEATED WRITE ELEMENT}

This application is a partial continuing application of US Patent Application No. 13 / 687,282, filed November 28, 2012 and further discloses 35 U.S.C. Provisions are made to Provisional Patent Application Serial No. 61 / 676,835, filed on July 27, 2012, in which priority is claimed under ζ19 (e), the entire contents of which are hereby incorporated by reference in their entirety. .

Examples disclosed herein relate to a heat-assisted magnetic recording device. In one embodiment, the apparatus includes a write element configured to apply a magnetic field to write data on a portion of the heating magnetic recording medium in response to an energizing current. The energy source is configured to heat a portion of the medium magnetized by the writing element. A preheat activation current is applied to the write element for an interval before writing data to the portion of the medium. The preheating activation current prevents data from being written to the medium, causing at least one of the write element and driver circuitry to be in thermal equilibrium before writing data to a portion thereof.

In yet another embodiment, the methods and apparatuses facilitate determining that data will be written to a portion of the heated magnetic recording medium. A preheat activation current is applied to the write element for a period of time before writing data to a portion of the medium. The write element applies a magnetic field to the medium in response to the preheat activation current. The preheating activation current prevents other data from being written to the medium and causes at least one of the write element and driver circuit to be thermally balanced before writing data to a portion thereof. After the interval, the energy source is configured to heat a portion of the activated medium, and an activation current is applied to the write element to write data to the portion of the medium.

In yet another embodiment, the heat applied from the writing head to the recording media is removed while writing to the heating magnetic recording medium is not made. The columns facilitate writing to the recording medium. Power is applied to the writing coil of the writing head to control the spacing between the writing head and the recording medium when the recording medium is not being written.

These and other features and aspects of various embodiments will be understood in light of the following detailed discussion and the accompanying drawings.

A discussion is made below with reference to the following figures, wherein like reference numerals may be used to identify similar / identical components in multiple figures.
1 is a side view of a slider according to an exemplary embodiment;
2 is a timing diagram illustrating preheating of a slider in accordance with example embodiments;
3 is a block diagram of an apparatus according to an exemplary embodiment;
4 is a flow chart illustrating a procedure according to an example embodiment;
5 is a flowchart illustrating a process in accordance with various embodiments;
6 is a cross-sectional view of a write head in accordance with an exemplary embodiment;
7 is a graph illustrating protrusions directed to a writing coil, in accordance with an exemplary embodiment; And
8 is a flow chart illustrating a procedure according to an example embodiment.

This disclosure relates to the use of preheating associated circuitry and write elements (eg, write coils) to achieve thermal equilibrium in a heated magnetic recording (HAMR) device. In one embodiment, preheating the writer coil and driver circuit is controlled externally, for example via a system controller. The same result can also be implemented in the preamplifier via firmware controlled registers that affect internal preamplifier circuits. Other permutations of control are also possible. A writer coil current is applied prior to the actual write operation, thereby simplifying the control of the fly-height for the writer protrusion during the active write operation.

In HAMR devices, also sometimes called thermal-assisted magnetic recording (TAMR) devices, thermal energy is used with magnetic fields applied to a magnetic recording medium (e.g., hard drive disk), typically It overcomes the superparamagnetic effects that limit the data plane density of magnetic media. In a HAMR recording device, information bits are written to the storage layer at elevated temperatures. The heating area in the storage layer determines the data bit dimension, and the linear write density is determined by magnetic transitions between the data bits.

To achieve the desired data density, HAMR recording heads (e.g. sliders) are optical components that direct, concentrate and convert light energy from an energy source, such as a laser diode, for heating on the recording medium. Include them. HAMR media hotspots may need to be smaller than the half wavelength of light available from economical sources (eg, laser diodes). Due to what is known as the diffraction limit, optical components cannot focus light at this scale. One way to achieve tiny limited hot spots is to use an optical near field transducer (NFT), such as a plasmonic optical antenna. NFTs are designed to have surface plasmon resonance at the designed light wavelength. At resonance, a high electric field surrounds the NFT due to the collective oscillation of electrons in the metal. Part of the field is tunneled and absorbed into the storage medium, raising the temperature of the medium locally above the Curie point for recording. Without the presence of thermal energy, the medium will be below the Curie point, and even if there is a magnetic field from the writer, no efficient erase or re-magnetization will occur. However, it is inherently understood that magnetic transitions are limited (magnetically freeze) at temperatures below the Curie temperature.

HAMR drives can use lasers and near field transducers to heat the media to assist in the recording process. Due to the inefficiency of the optical transmission path, the laser and near field transducer also heat the head / slider. Heating may originate from the NFT, from light delivery optics and / or from the laser itself. The energy absorbed by these components can be converted into heat that is conducted to surrounding materials. This heating may result in the writer element protruding (ie flying closer to the disc) through slider thermal expansion or by changing the shape of the slider and changing air bearing properties (head-media spacing (HMS)). Can lead to changes. This example is shown in FIG. 1, which illustrates a side view of the slider 102 in accordance with an exemplary embodiment.

In some HAMR drive embodiments, a technique known as pulsing is used to control the laser. Pulsing flashes the laser in synchronization with the magnetic transitions from the writer coil. The timing of pulsing on the transitions can affect the bit error rate of the writing system. The timing of these transitions is affected by electrical delays through the preamplifier driver circuit, which may be affected by the temperature of the circuit. One additional consequence of the early and / or continuous application of the writer coil current is to induce the driver circuit to thermal equilibrium to minimize timing delay shifts.

Slider 102 is connected to an arm (not shown) by suspension 104, which is attached to gimbal 106 to allow some relative movement between slider 102 and suspension 104. . The slider 102 includes read / write transducers 108 at a trailing edge held near the surface 110 of the magnetic recording medium, for example the disk 111. When the slider 102 is positioned above the surface 110 of the disc 111, the flight height 112 is maintained between the slider 102 and the surface 110 by the downward force of the suspension 104. do. This downward force is counterbalanced by an air cushion that deviates between the air bearing surface (ABS) 103 and the surface 110 of the slider 102 as the disk 111 rotates.

It is desirable to maintain a predetermined spacing between the writer and reader elements and the media 112 over a range of cylindrical disk locations during both read and write operations to ensure consistent performance. The region 114 is the “closest point” of the slider 102, which is generally understood to be the closest point of contact between the slider 102 and the magnetic recording medium 111 and generally defines the HMS 113. Heating from the HAMR optical components can affect the HMS 113.

Heating from the writer coil current can affect the HMS 113. In this example, geometrical changes, in whole or in part, can be induced by the temperature rise or fall of the region 114 due to the different thermal expansion properties of the respective materials surrounding the region. This is shown by the dotted lines in FIG. 1 indicating the geometrical change of the region 114. Exemplary HAMR components that can induce such temperature variations include a top mounted laser 119, waveguide 121 and NFT 123. To control the spacing, many write heads further include one or more internal heaters (not shown) for intentionally adding heat. In one exemplary embodiment, the slider 102 includes two heaters. The first additional heater is very close to the reader element and is called a reader-heater. The second heater is very close to the writer element and is called the writer-heater.

Slider 102 may include a temperature resistant sensor 120. This sensor 120 has a temperature coefficient of resistance (TCR) that enables high accuracy temperature (or temperature change) measurements in the region 114 and is therefore sometimes referred to as a TCR sensor. The TCR sensor 120 is coupled to the control circuit 122. The control circuit 122 communicates with the sensor 120 as well as with other electrical components of the slider 102. Two or more TCR sensors 120 may be used, for example located at locations physically separated from each other. Multiple sensors 120 may be wired separately or together (eg, in series or in parallel) with each other to reduce the number of connections required for slider 102.

In the HAMR recording device, four projections each having different time constants in the ABS during writing: a writer-heater projection (˜100 ms); Writer coil protrusion (˜100 ms); NFT protrusions (˜1 ms following ˜100 ms); And laser heating (˜1000 ms) of the slider may need to be managed. Conventional HAMR preamplifiers turn the writer coil on simultaneously with a laser. This causes interaction between the writer-coil and the NFT guide protrusions. Due to the high coercive force of the HAMR medium, the head cannot write to the medium unless the laser is active. This means that the writer-coil and writer-heater currents can be enabled before writing, which causes them to reach thermal equilibrium over the time that writing occurs. This means that only the thermal protrusion dynamics from the laser need to be considered after all the rest is in thermal equilibrium.

Thus, the preamplifier according to an exemplary embodiment may be modified to apply a current through the writer prior to the sector (s) being written. In such a configuration, the writer coil current can be kept on or switched off during these times as long as the laser is off during sector gaps and servo gates (SG). It may be desirable to turn the writer current off during SG to avoid coupling to the read head and impact on the servo system.

The pre-heat current applied to the writer coil may be alternating current (AC) or direct current (DC). The AC signal may avoid any pitfalls caused by DC magnetic fields, but a DC signal may be required if the writer-coil current is left on during SG to reduce electrical noise. For example, US Pat. No. 7,088,537 to Cronch et al. Describes a degauss mode in a disk drive preamp. The degauss mode circuit of the preamplifier (or the like) can be used as a control source for AC current for this purpose. The AC signal may be generated internally within the preamplifier and / or externally by a system read channel (SRC) that is part of a system controller, such as the main controller application specific integrated circuit (ASIC) of the hard drive. Either approach is acceptable, both of which are presented herein.

Referring now to FIG. 2, a timing diagram shows an example of how the recording head can be preheated in accordance with an exemplary embodiment. This figure is divided into four types of signals: timing control 202, laser and channel writer control 204, firmware control 206, and physical currents 208.

As shown by trace 216, the firmware writes to the preamplifier registers at time 201 to set the current for the laser bias and writer coil prior to the write operation. The firmware enables preheating with sufficient time for the writer-heater current 238 and the writer-coil current 228 to allow components affected by them to reach thermal equilibrium. The preheating time for the writer-coil is indicated by interval 203 in FIG.

The firmware may optionally enable a new preamplifier feature that uses an internally generated AC or DC signal to transfer current to the writer coils. This example is observed in FIG. 3, which is a block diagram of an apparatus 300 according to an exemplary embodiment. The device 300 includes a system controller 317 that can include one or more logic circuits that control the functions of the device 300. System controller 317 receives commands via host interface 303. In response to the write commands from the host interface 303, the system controller 317 causes the write preamplifier assembly 301 to write data to the magnetic data storage medium 305.

Preamplifier assembly 301 includes a writer-coil driver circuit 302 that drives one or more write coils 304 included in write head 318. The write coil 304 generates a magnetic field in response to the current being applied. The preamplifier 301 is controlled by combining the write data signals WDATA +/- 309 and 310 and the write enable line 308 through the multiplexer 306, among other control signals not shown. The apparatus includes, along with the system controller 317, firmware 315 that causes the preamplifier 301 to transmit current to the writer coil 304 using internally generated AC or DC signals. The AC signal may be generated by an internal oscillator 320 such as used for degaussing operations. This alleviates the need to control the write data signals (WDATA +/−) 309, 310 to perform preheating signaling. The writer-coil preheating is performed during servo (eg, during period 205 of FIG. 2) to minimize cross talk between writer and reader lines on a flex on suspension (FOS). Can be turned off.

The device 300 further includes an energy source 316 (eg, concentrated laser diode output) that heats a portion of the medium 305 currently magnetized by the write coil 304. Energy source 316 is enabled through system controller 317 (eg, laser enable line 224 of FIG. 2) to heat a portion of medium 305 during recording. For the purposes of this discussion, a "part of the medium" may comprise an area larger than the signal bits of the data being written. For example, the portion may comprise a plurality of hard drive sectors, and writing may be stopped and resumed during writing of the portion, for example when the traversing servo is marking.

As described herein, activation of the write coil 304 when the energy source 316 is not activated generally prevents other data from being written to the medium 305 (eg, at local magnetic orientation in the medium). No significant change) will ensure that any existing data is not deleted. It is noteworthy that in some designs that utilize a semiconductor laser diode as an energy source, it is still desirable to have a small current flowing through the laser diode while not writing. For the purposes of this disclosure, even if there is a small bias current, the laser is still inactive unless the laser is sufficiently lasered to raise the media temperature near or above its Curie point. It can be thought of as. As such, in some cases, the write coil 304 thermally balances the write element (eg, write coil 304, write pole and associated components) without writing other data to the medium 305 during activation. It can be activated by the activation current to move to the thermal equilibrium. To accomplish this, the energy source 316 and the write coil 304 can be controlled via separate signals.

Referring again to FIG. 2, signals 214, 224, and 234 are generally considered to be part of the writer and laser controls of the read channel of the system controller. The channel controls the write data lines (signal 214) and the laser enable line (signal 224) as well as the write-enable (W / Rn) line (signal 234). The channel enables the laser whenever he wants to write data to the disc. When writing of consecutive sectors is not necessary, the laser enable line is not the same as W / Rn because it may be necessary to prevent such writing. Separating these lines also allows the ability for pulsing control and writer preheating. In continuous write mode, laser control is a logical signal. For pulse writes, the logic gate can be replaced by high bandwidth laser data.

Signals 218, 228, and 238 are the physical currents that are output to the laser, writer coil, and heater, respectively. Laser current 218 as shown is for a pulsed laser. If this is a CW implementation, the laser current will switch on at the start of the sector and be in standby for the duration. Only when the laser current 218 is sufficient for lasing is data written to the disc. In the case of no or reduced laser current 218, the field from the head is insufficient to mark the disk. However, in the absence of any write current 228, the laser will still erase the disc.

In FIG. 4, a flowchart illustrates a procedure for preheating a write element according to an example embodiment. It is determined 410 that the data will be written to a portion of the HAMR media (eg, by the system controller). The preliminary heating activation current is applied to the write element during the interval before writing data to the portion of the media (420). The preheated activation current prevents data from being written to the media and moves the writer to thermal equilibrium (which is understood to include maintaining the existing thermal equilibrium) before writing the data to the portion. After the interval, an energy source (eg, a laser diode) is activated (430). The energy source is configured to heat a portion of the media, and an activation current is applied to the write element to write data to the heated portion of the media.

According to various implementations, HAMR can be used in combination with recording on Bit Patterned Media (BPM). BPM formats may include various fields such as timing recovery and servo fields embedded within the data area of the media. According to various implementations, timing fields embedded within the data regions of the media are read while ongoing write operations are stopped. The write coil current is turned on when the write pole traverses these fields to eliminate the format overhead associated with non-zero times it takes to turn off the write current and turn it back on during the reading of the timing field. It may be advantageous to keep on).

Additionally, Bit Patterned Media implementations may require precise timing of magnetic field transitions and / or laser pulsing synchronized with the bits on the media. The timing of these transitions is affected by electrical delay through the preamplifier driver circuit and these delay times can be affected by the temperature of the circuit. One additional consequence of the preceding and / or sequential application of the writer coil current is to cause the driver circuit to be thermally balanced to minimize timing delay shifts.

According to various implementations, the writer turn-on / turn-off overhead is reduced by turning on the DC write current while reading timing fields. For example, when timing fields are patterned such that unipolar magnetization can be used, the write transition overhead is by writing a DC of the same polarity as the write pole traverses the unipolar field with the laser off or on state. Can be removed. In some cases, however, unipolar-filled fields, such as runout correction values, may be corrupted by DC writing. Therefore, in some cases, it may be useful to turn off the laser when reading timing fields to prevent data corruption and / or overwrite.

It may be useful to achieve faster thermal balance and eliminate writer turn-on / turn-off overhead by leaving the DC write current and laser on while on a unipolar BPM servo field. However, in some cases, there may be bipolar-filled information fields (such as runout correction values) that are altered by DC write, in contact with or within these servo fields. Thus it would be advantageous in a HAMR + BPM system to turn off the laser during unipolar fields to enable keeping the write current on without risking altering the bipolar information fields.

In FIG. 5, a flow chart illustrates a process of preheating a write element in accordance with embodiments described herein. It is determined 510 that the data will be written to the portion of the HAMR media. Writing operation of data to heat-assisted magnetic recording media is initiated (520). The write operation is suspended during the interval (530). According to various implementations, various fields (eg, timing or servo fields) are read during the interval. A preheat activating current is applied to the write element (540), causing the writer to be in thermal equilibrium, which write element applies a magnetic field to the medium in response to the preheat activating current and the preheat activating current does not cause data to be written to the mediums. . After the interval, the energy source (eg, laser diode) is activated 550. In some cases, the write operation resumes upon completion of the interval and the light source is reactivated. Resuming the write operation can include activating the light source.

Referring now to FIG. 6, a cross-sectional view illustrates components of read / write transducer 600 in accordance with an example embodiment. This figure shows the portion of the slider near the close-point zone 601. In this respect, the x-direction is down-track relative to the medium and the z-direction (perpendicular to the face of the page) is the cross-track direction. The read sensor 602 is located near the ABS 607. The read sensor may include a magnetoresistive stack and a shield. Reader heater 604 may be implemented to adjust the local space between read sensor 602 and media surface 603.

The write pole 606 may include a ferromagnetic structure that extends to the ABS 607. The write coil 608 is activated to generate a magnetic field in the write pole 606 extending to the media surface 603. The slider can be configured for vertical recording, with the magnetic orientation perpendicular to the media surface 603 (oriented along the y-direction in this respect). Thus, the slider may include one or more return poles 610, 612 that facilitate the vertical orientation of the magnetic fields of the recorded data, along the particular arrangement of the layers in the medium 605. Spacer 614 may be disposed between the read and write portions of the slider.

To write to the HAMR medium 605, the slider includes a waveguide 616 extending towards the ABS 607. Waveguide 616 transmits light to near-field transducer (NFT) 618 located in ABS 607 near the tip of writing pole 606. NFT 618 facilitates directing a beam of electromagnetic energy to media surface 603 during write operations. The energy creates a small hot spot on the media surface 603 with lower magnetic coercivity, making it possible for the magnetic field generated from the write pole 606 to affect the magnetic orientation in the hot spot.

In some configurations, the spacer 614 (or some other area near the write poles 606 and / or return poles 610, 612) is also independent of the write sensor 602 of the write pole 606. A heater may be included to adjust the head-to-media space. However, in this example, the slider does not include a separate heater. Instead, the write coil 608 can be activated to provide heat that can normally be provided by a separate heater. Any magnetic fields generated by this activation of the coil 608 will not change the data on the medium 605 unless the light source is activated to heat the medium surface 603.

The illustrated example shows a reader heater 604 used with the write coil 608 to independently control the head-to-media clearances of the read and / or write portions of the transducer. In one example, the reader heater 604 controls the head-medium space of the read sensor 602, and the write coil 608 alone or in combination with the reader heater 604, the head-medium space of the write pole 606. To control. In another example, a different heater (eg, located near the writing portions of the transducer 600) may be used to control the head-medium space of the writing pole 606, and the writing coil 608 Is used to adjust the head-medium space of the read sensor 602 (alone or with a different heater), so that activation of the write coil 608 causes little or no interface with the read sensor 602. It is assumed to be.

Referring now to FIG. 7, graph 700 illustrates an example of ABS protrusions of a HAMR slider in accordance with an exemplary embodiment. In this graph 700, the profiles of the ABS are represented as the spacing / clearance between the ABS and the medium along the vertical axis and as the downtrack position along the horizontal axis. Downtrack zone 702 represents the close point (eg, near the read or write transducer) of the ABS. Trace 704 represents the profile of the ambient temperature, where no power is applied to either the heater or the recording coil. Trace 706 is a profile when the heater is powered alone; Trace 708 represents the profile when the heater and recording coil are energized; Trace 710 then represents a profile when the heater, recording coil, and laser are all energized.

As the difference between traces 706 and 708 illustrates, the write coil alone can generate as much heat as necessary to cause sufficient protrusion. In addition, the recording coil may be used in conjunction with one or more co-operating heaters (instead of dual heaters operating separately), such that the recording and reading portions of the magnetic head at different times and / or states of the slide. Both desired clearances can be achieved. For example, the write coil current can be set to a value that maximizes performance (at a constant head-medium interval), and at the same time, a dedicated heater can be used to drive the clearance to the desired value. This may be useful during write operations, where the write coil activation to write will result in some predictable amount of protrusion and the dedicated heater may fine tune the clearances.

The various features of the read / write head can be designed in a way that takes full advantage of the writer protrusion as a mechanism for controlling the head-medium spacing. For example, the resistance of the recording coil can be increased to induce higher temperatures for purposes that affect the head-medium spacing. The recording coils and / or peripheral regions can be designed using higher coefficients of thermal expansion to increase protrusion. In another example, features designed to cool the recording coil can be designed in a manner that reduces cooling in the coil and adjacent areas, eg, using materials of lower thermal conductivity.

Referring now to FIG. 8, a flowchart illustrates a procedure according to an example embodiment. In this procedure, the first path 802 is taken if no heat-assisted magnetic recording medium is being recorded. In such a case, heat from the recording head to the recording medium is removed 804. This may include turning off or removing a device that provides heat (eg, a laser, an optical path). Power is applied to the recording coil of the recording head 806 to control the distance between the recording head and the recording medium when the medium is not being recorded. The spacing may comprise a spacing between reading and / or writing elements of the recording head. Optionally, power may be applied 807 to a dedicated heater for controlling the gap at the same time as the application of power to the recording coil 806.

Path 808 represents head-to-disk clearance operations that occur when the recording medium is written where at least one source of heat (eg, laser light) is applied to the recording medium. Heat is applied from the writing head to the recording medium (810). One or both of the operations 812 and 814 may be performed to adjust the clearance (eg, clearance between the medium and the read head and / or write pole) while the medium is being written. Operation 812 involves applying power to the write coil to write data and control the space between the write head and the medium. Operation 814 involves applying power to a dedicated heater to control the gap between the write head and the medium. This may be the same dedicated heater used at block 807.

The apparatus includes: a writing element configured to magnetize a portion of a heat-supporting magnetic recording medium in response to an activation current during a writing operation; And an energy source configured to heat a portion of the medium magnetized by the writing element; The activation current is applied to the write element during the interval during which the write operation is suspended and the energy source is deactivated, applying the activation current to the write element does not induce other data to be written to the medium and the activation current is The write element and / or driver circuit is placed in thermal equilibrium prior to writing data to the portion. The energy source may comprise a laser diode. The write operation may resume upon completion of the interval. Resuming a write operation may involve activating an energy source. The apparatus may be configured to read the timing fields during the interval.

The previous description of exemplary embodiments has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the embodiments to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. Any or all of the features of the disclosed embodiments may be applied individually or in any combination, and are meant to be purely illustrative and not restrictive. It is intended that the scope of the invention should not be limited to this detailed description, but may be determined by the claims appended hereto.

Claims (20)

As an apparatus,
A writing element configured to apply a magnetic field to write data on a portion of a heat-assisted magnetic recording medium in response to an energizing current; And
An energy source configured to heat a portion of the medium magnetized by the writing element
Wherein a preheating activation current is applied to the writing element for an interval prior to writing data to a portion of the medium, the preheating activation current such that no other data is written to the medium. And cause at least one of the write element and driver circuit to be thermally balanced prior to writing the data to the portion. The method of claim 1,
The energy source comprises a laser diode and the energy source is not activated during the interval. The method of claim 1,
Wherein the preheating activation current comprises an alternating current. The method of claim 3, wherein
Wherein the alternating current is controlled by a system controller. The method of claim 3, wherein
The alternating current is controlled by a preamp driving the write element. The method of claim 1,
Wherein the preheat activation current comprises a direct current. The method of claim 1,
And the medium comprises a bit patterned medium. The method of claim 7, wherein
During the interval a unipolar field is traversed, the activation current is direct current, and the energy source is activated during the interval. The method of claim 7, wherein
The bipolar field is traversed during the interval and the energy source is not activated during the interval. As a method,
Determining that data will be written to a portion of the heated magnetic recording medium;
Applying a preheat activation current to a write element for an interval before the data is written to a portion of the medium, wherein the preheat activation current prevents other data from being written to the medium and Bring the write element and / or driver circuit into thermal equilibrium prior to writing data;
After the interval, energizing an energy source configured to heat a portion of the medium and applying an activation current to the write element to write data to the portion of the medium.
/ RTI > 11. The method of claim 10,
And de-energizing the energy source during the interval. 11. The method of claim 10,
And the preheating activation current comprises alternating current. 13. The method of claim 12,
Controlling the alternating current through a system controller. 13. The method of claim 12,
Controlling the alternating current in a preamplifier driving the write element. As the write head,
A device configured to apply heat to a heated magnetic recording medium to facilitate writing to the recording medium;
Fill coil
Wherein the write coil is configured to apply a magnetic field to the magnetic medium in response to the application of power to the write coil, the write coil to the write coil, at least when heat is removed from the recording medium. And control the space between the write head and the magnetic medium in response to the application of power to the device. The method of claim 15,
And the device comprises a near field transducer, the apparatus further comprising an optical device configured to apply energy to the near field transducer. The method of claim 15,
Application of power to the recording coil causes a heat-induced protrusion of the write head that changes the space between the write head and the recording medium. The method of claim 15,
The application of power to the write coil is used in place of a dedicated heater to control the space for the transducer of the write head. The method of claim 15,
The writing coil is further configured for both writing data to the magnetic medium and controlling the space between the writing head and the recording medium during writing to the recording medium. The method of claim 15,
The magnetic field does not write data to the recording medium when heat is removed from the recording medium.

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