Heat assisted magnetic recording head having thermal sensor with high-TCR transparent conducting oxide

A head transducer includes a thermal sensor comprising a conducting ceramic material having a temperature coefficient of resistance. The thermal sensor can comprise a transparent conducting oxide having a temperature coefficient of resistance. The thermal sensor can be situated proximate a near-field transducer of the heat-assisted magnetic recording head transducer.

SUMMARY

Embodiments of the disclosure are directed to an apparatus which includes a head transducer and a thermal sensor at the head transducer. The thermal sensor comprises a conducting ceramic material having a temperature coefficient of resistance. In some embodiments, the thermal sensor comprises a transparent conducting oxide having a temperature coefficient of resistance.

According to some embodiments, an apparatus includes a head transducer, a near-field transducer at the head transducer, and a thermal sensor proximate the near-field transducer and configured to produce a sensor signal indicative of temperature. The thermal sensor comprises a transparent conducting oxide having a temperature coefficient of resistance.

In accordance with other embodiments, a method involves sensing a temperature proximate a near-field transducer of a head transducer using a thermal sensor comprising a conducting ceramic material having a temperature coefficient of resistance. Some embodiments are directed to a method involving sensing a temperature proximate a near-field transducer of a head transducer using a thermal sensor comprising a transparent conducting oxide having a temperature coefficient of resistance.

DETAILED DESCRIPTION

The present disclosure generally relates to magnetic recording devices used for data storage. Data storage systems may include one or more transducers that respectively write (e.g., a writer) and read (e.g., a reader) information to and from a magnetic storage medium. It is typically desirable to have a relatively small distance or separation between a transducer and its associated media. This distance or spacing is referred to herein as “head-media separation” (HMS). By reducing the head-media separation, a reader and a writer is generally better able to both write and read data to and from a medium. Reducing the head-media separation also allows for surveying of magnetic storage medium topography, such as for detecting asperities and other features of the recording medium surface.

To establish head-media separation in a storage system, head-media contact is detected. Head-media contact detection and/or head-media separation sensing technologies are important for the performance and reliability of hard disk drives. Higher contact detection repeatability enables lower active clearance, and thus higher recording density. Higher contact detection sensitivity reduces wear and improves reliability.

One approach for detecting contact involves evaluating a temperature profile for a recording head transducer before, during, and after contact between the head transducer and a surface of a magnetic recording medium. When the head transducer is actuated by a thermal actuator, the head transducer surface temperature increases with the actuation due to the heat generated by the thermal actuator. The head transducer temperature will then be higher than the temperature of the medium. As such, the medium acts as a heat sink. When the head transducer contacts the medium, the head transducer surface temperature drops due to a change in heat transfer rate resulting from the contact. The head transducer surface temperature then continues to increase due to the continued thermal actuator heating as well as the added frictional heating. The change in temperature or excursion in temperature trajectory can be used to declare head-media contact. Details concerning head-media separation and contact determinations which can be implemented in apparatuses and methods in accordance with various embodiments of the disclosure are provided in commonly owned U.S. Patent Application Publication Nos. 2012/0120519, 2012/0120522, 2012/0120527, 2012/0120982, and 2012/0113207, each of which is incorporated herein by reference.

A head transducer arrangement100for detecting sensing temperature and head-media contact in accordance with various embodiments is illustrated inFIG. 1. The head transducer arrangement100includes a recording head transducer102comprising a slider150positioned proximate a rotating magnetic medium104. The magnetic medium104is configurable for reading and/or writing data with head transducer102. The surface of head transducer102facing magnetic medium104includes an air bearing surface (ABS)160.

The head transducer102includes a reader120and a writer130proximate the ABS160for respectively reading and writing data from/to the magnetic medium104. The writer130is configured for heat assisted magnetic recording (HAMR) and is located proximate a laser arrangement including light source110(e.g., laser diode). Light source110can be mounted external, or integral, to the head transducer102. Light source110energizes a near-field transducer (NFT)140via a waveguide114proximate the ABS160and writer130respectively.

The writer130includes a corresponding heater135, and reader120also includes a corresponding heater125according to various embodiments. Each of the heaters125,135is thermally coupled to head transducer102and may be a resistive heater that generates heat as electrical current is passed through the heaters125,135. The heaters125,135are not limited to resistive heaters, and may include any type of heating source. A processor can be configured to adjust the power supplied to one or both of heaters125,135. For example, power supplied to heater135can be adjusted when NFT140and/or writer130is activated to adjust the spacing between ABS160and magnetic medium140.

At the air bearing surface160and proximate the NFT140and writer130is a thermal sensor170. Thermal sensor170is described herein as a resistance temperature sensor composed of materials having a temperature coefficient of resistance (TCR). One example of a TCR sensor is a dual-ended temperature coefficient of resistance sensor (DETCR). A TCR sensor measures temperature change by measuring the change in resistance, or rate of change in resistance, across the sensor. The thermal sensor170measures the temperature change at ABS160induced by all thermal condition changes from air pressure, clearance, head operation, and contact, among other changes.

The apparatus shown inFIG. 1also includes a processor or controller113according to various embodiments. Processor113can be configured to perform a variety of functions, including controlling power delivery to laser110and to heaters125and135. In some embodiments, processor113is configured to adjust power supplied to one or both of the laser110and writer heater135for purposes of adjusting fly height of transducer102relative to magnetic storage medium104. The processor113can be coupled to thermal sensor170and configured to measure head transducer temperature, from which head-media separation and head-media contact can be measured/detected in accordance with various embodiments.

Head-media contact detection typically involves intentional protruding of the air bearing surface of the head transducer into an air gap between the head transducer and an adjacent magnetic storage medium in response to thermal actuation by one or a combination of different heat sources at the head transducer. In heat assisted magnetic recording (HAMR), for example, the head transducer can be subjected to at least three sources of heat. One heat source is the write coil of the writer when actuated. A second source involves heating components included in the head transducer and associated with the reader and writer circuitry, which can be selectively activated to intentionally expand the air bearing surface. The heating components are controllable/programmable to vary the total amount of heat actuating the head transducer and, therefore, the magnitude of reader and/or writer protrusion. A third source is the NFT corresponding to the HAMR heat source, e.g., a laser. The NFT transforms laser energy to thermal energy in order to heat a spot on the magnetic medium during write operations.

Each of these heat sources alone, or in combination, cause the head transducer materials at the air bearing surface to expand. When the materials expand, they cause the air bearing surface to protrude into the air gap between the head transducer and the magnetic storage medium. For the highest likelihood of detecting contact, the TCR sensor is preferably located as close as possible to a maximum area of protrusion. For example, the TCR sensor may be located at or as close as possible to the close point of the transducer. Since protrusion is caused by heat generated in the head transducer, it is beneficial to locate a TCR sensor at or near the heat generation source or sources, e.g., the writer, NFT, and heater(s). A TCR sensor (e.g., a reference temperature sensor) may also be located away from these heat sources and the ABS, allowing for differential temperature measurements to be made.

In the embodiment illustrated inFIG. 1, thermal sensor170is situated near the NFT140, which is typically the component that produces the greatest amount of heat at the head transducer102. The thermal sensor170is configured to produce a signal indicative of a temperature near the NFT140. The sensed temperature at the thermal sensor location can be influenced by heat produced by writer130, heaters125and135, and other sources of heat within the magnetic recording device (e.g., hard disk drive). In some embodiments, the thermal sensor170is configured to operate in thermal environments exceeding 200° C. In other embodiments, the thermal sensor170is configured to operate in thermal environments exceeding 220° C. In further embodiments, the thermal sensor170is configured to operate in thermal environments exceeding 250° C. (e.g., up to about 400° C.).

FIGS. 2A-Cshow general protrusion progression using a simplified cross-sectional view of a writer portion of a head transducer200. InFIG. 2Ahead transducer200is in a non-thermally actuated state. In this state, the laser, writer heater, and writer coil are all off. Thus, head transducer200attains a default, non-actuated shape/state establishing a default separation between medium280and air bearing surface250of the head transducer200. This default separation is illustrated by air gap270.

FIG. 2Billustrates the transducer200with the writer coil and heater activated, but the laser inactive. Here, the writer-related components (write pole215, NFT220and thermal sensor (TS)225) expand. The write pole215; the NFT220; and the thermal sensor225expand causing the air bearing surface250to protrude into the air gap270. Thus, the air gap270and the distance between air bearing surface250and the medium280decreases. The dashed line indicates the default state/shape of air bearing surface250. As can be seen, the actuation of the two heat sources expands the writer components, and adjoining head transducer materials, to protrude beyond the default shape of the head transducer200shown inFIG. 2A.

The protrusion is further expanded by the additional actuation of the laser, as shown inFIG. 2C. The additional heat produced by the NFT220in response to the incident laser light further expands the air bearing surface250into air gap270. The stroke, or magnitude of the protrusion along the cross track direction (z-axis) of the head transducer200, changes with introduction of additional heat. It is noted that the thermal sensor225ofFIGS. 2A-2Cis shown located on the pole side of the transducer200, such that it resides between the write pole215and the NFT220. In some embodiments, the thermal sensor225is located on the non-pole side of the transducer200, such that it resides on the other side of the NFT220(right of NFT220in the illustration ofFIGS. 2A-2C) as in the configuration depicted inFIG. 4.

Referring once again toFIG. 1, the thermal sensor170is preferably implemented as a TCR sensor capable of sensing temperatures of intense heat due to being situated at or near the NFT140. In addition to being capable of sensing intense heat, thermal sensor170preferably has a high temperature coefficient of resistance which provides for high sensitivity and a high signal-to-noise (SNR) ratio when operating in thermal environments exceeding 200° C. or 250° C., for example. In some embodiments, thermal sensor170preferably has a high temperature coefficient of resistance which provides for high sensitivity and a high signal-to-noise (SNR) ratio when operating in thermal environments exceeding 300° C., 350° C., or as high as 400° C., for example.

Conventional TCR sensors used for head-media contact detection rely on common metals such as Cr or NiFe for the thermal sensing elements. Temperature coefficients of resistance (TCR) values for these materials are low, typically in the 0.1-0.3%/° C. range, which limits the sensitivity and SNR when being used in high temperature sensing applications. Moreover, many of these conventional materials are prone to high-temperature oxidation. The materials of conventional TCR sensors are unsuitable for use in thermal environments dominated by heat produced by an NFT.220. Materials having larger TCR values are desirable, including those with high TCR values in the >1%/° C. range, which are typically observed either in semiconductors, complex oxide-based systems like defected vanadium oxides or perovskite oxides with very high resistivity, or in metal systems near the percolation limit which introduces unusual, but hard-to-control electron transport effects.

According to various embodiments, a thermal sensor well suited for incorporation in a head transducer that includes an NFT and configured to operate in thermal environments exceeding 200° C., 300° C., or even 400° C., for example, comprises a conducting ceramic material having a temperature coefficient of resistance. In various embodiments, a thermal sensor well suited for incorporation in a head transducer that includes an NFT comprises a transparent conducting oxide (TCO) having a temperature coefficient of resistance. A TCR sensor comprising a transparent conducting ceramic material, such as a TCO, has substantially lower heat absorption than a metal TCR sensor, for example, resulting from light-induced heating at or near the NFT and/or waveguide. Because a TCR sensor comprising a transparent conducting ceramic material has lower heat absorption from light-induced heating at or near the NFT and/or waveguide than a metal TCR sensor, TCR sensors according to embodiments of the disclosure sink far less heat away from the thermal environment surrounding the transparent TCR sensor than do metal TCR sensors, thereby increasing temperature sensing accuracy.

As previously discussed, a TCR sensor is biased to operate at a temperature higher than the magnetic storage medium temperature. Due to various forms of heating within a magnetic storage device, the average operating temperature of a magnetic storage medium is generally well above an ambient temperature external of the magnetic storage device. For HAMR devices, for example, a TCR sensor is biased at a relatively high temperature due to the heat effects of the NFT, in particular. In order to situate a TCR sensor at or near the NFT, it can be appreciated that such a TCR sensor will be subjected to heating due to sensor biasing and the thermal condition at the NFT. Modeling data shows that a TCR sensor positioned adjacent an NFT can experience a temperature change of about 100° C. during operation. According to some embodiments, when coupled with bias current-induced heating at 100 mV of ˜60° C. and another 55° C. from top-end ambient temperature in a modeled hard disk drive, a TCR sensor can easily be exposed to temperature well in excess of 220° C., which is substantially higher than that of non-HAMR devices.

Modeling data for various HAMR heat transducers show that the temperature rise within the NFT can go up as high as 1000° C. by absorbing only 1 mW optical power (see, e.g., commonly owned US Patent Application Publication 2012/0314549, which is incorporated herein by reference). Although this temperature increase within the NFT is very large, the temperature at the head transducer external of the NFT is significantly lower due to conductive, convective, and radiation cooling effects. Notwithstanding these cooling effects, it can be appreciated that a TCR sensor situated adjacent an NFT will be exposed to temperatures appreciably higher than those associated with head transducers of non-HAMR devices. It is noted that certain transparent conducting oxides well suited for use in various TCR sensor embodiments have good inherent oxidation resistance, melting temperature above 1800° C., and reasonably good wear properties, making them well suited for high-temperature applications.

Thermal sensors in accordance with embodiments of the disclosure are preferably implemented to have (a) adequate TCR to overcome any potential loss of output due to bias current margin compression (i.e., lower bias current may be required to compensate for the increased ambient temperature and insure that overall TCR temperature stays below failure threshold), and (b) high-temperature durability to resist accelerated thermally-induced microstructural instability, interface reaction, or ABS oxidation effects from the HAMR device environment. Various embodiments are directed to thermal sensors comprising a simple, ceramic-based high-TCR material possessing good chemical stability and acceptable resistance for temperature sensing at a HAMR transducer head.

Various embodiments are directed to thermal sensors for use in high temperature head transducer environments exceeding 200° C., 250° C., 300° C., 350° C. or 400° C. for example. Embodiments are directed to thermal sensors for use in high temperature head transducer environments that have TCR values exceeding those of conventional CR and NiFe thermal sensors. In various embodiments, thermal sensors for use in high temperature head transducer environments have TCR values exceeding about 0.5%/° C. In some embodiments, thermal sensors for use in high temperature head transducer environments have TCR values exceeding about 1%/° C. In other embodiments, thermal sensors for use in high temperature head transducer environments have TCR values exceeding about 1.5%/° C. In further embodiments, thermal sensors for use in high temperature head transducer environments have TCR values exceeding about 2%/° C. In certain embodiments, thermal sensors for use in high temperature head transducer environments have TCR values exceeding about 2.5%/° C. In some embodiments, thermal sensors for use in high temperature head transducer environments have TCR values exceeding about 3%/° C. In yet other embodiments, thermal sensors for use in high temperature head transducer environments have TCR values exceeding between about 3.5 to 5%/° C. In further embodiments, thermal sensors for use in high temperature head transducer environments have TCR values exceeding about 6%/° C., such as greater than about 7%/° C., 8%/° C., 9%/° C. or 10%/° C., for example.

According to various embodiments, a TCR sensor comprises a conducting ceramic material having a temperature coefficient of resistance. In accordance with some embodiments, a TCR sensor comprises a transparent conducting ceramic material having a temperature coefficient of resistance. In some embodiments, a TCR sensor comprises a transparent conducting ceramic material having a temperature coefficient of resistance and a transmittance of at least about 60%. In other embodiments, a TCR sensor comprises a transparent conducting ceramic material having a temperature coefficient of resistance and a transmittance of at least about 70%. In further embodiments, a TCR sensor comprises a transparent conducting ceramic material having a temperature coefficient of resistance and a transmittance of at least about 75 to 85%. In other embodiments, a TCR sensor comprises a transparent conducting ceramic material having a temperature coefficient of resistance and a transmittance of at least about 80 to 90%. According to some embodiments, a TCR sensor comprises a transparent conducting oxide (TCO) having a temperature coefficient of resistance, wherein the TCO has a transmittance value or range listed above.

In accordance with various embodiments, a TCR sensor comprises a conducting ceramic material having a temperature coefficient of resistance and an electrical resistivity of less than about 10−3Ωcm. In some embodiments, a TCR sensor comprises a conducting ceramic material having a temperature coefficient of resistance and an electrical resistivity of between about 10−4Ωcm and 10−3Ωcm. In other embodiments, a TCR sensor comprises a conducting ceramic material having a temperature coefficient of resistance and an electrical resistivity of less than about 10−4Ωcm. In further embodiments, a TCR sensor comprises a conducting ceramic material having a temperature coefficient of resistance and an electrical resistivity of between about 10−5Ωcm and 10−4Ωcm.

Various embodiments incorporate impurity-doped transparent conducting oxides for high-TCR, high-temperature capable thermal sensing elements. Suitable materials include ZnO, Al-doped ZnO, or Ga-doped ZnO. For example, thermal sensors comprising pure ZnO films can have TCR values in the 1-10%/° C. range. By way of further example, experiments using 100 nm Al-doped ZnO films prepared by atomic layer deposition demonstrates that thermal sensors comprising such Al-doped ZnO films can provide for TCR values of 1%/° C. or more. It is notable that these TCR values are about 4-50 times higher than TCR values achievable using conventional TCR sensor materials.

Embodiments of the disclosure are directed to a TCR sensor comprising a ceramic material comprising AZO (Al-doped zinc oxide). According to various embodiments, a TCR sensor includes a ceramic material comprising AZO, wherein a concentration of Al in the Al-doped ZnO ranges between about 0.1 and 15 weight %. (wt %). In some embodiments, a TCR sensor includes a ceramic material comprising AZO, wherein a concentration of Al in the Al-doped ZnO ranges between about 0.1 and 8 wt %. In other embodiments, a TCR sensor includes a ceramic material comprising AZO, wherein a concentration of Al in the Al-doped ZnO ranges between about 0.1 and 4 wt %.

According to various embodiments, a TCR sensor includes a ceramic material comprising GZO (Ga-doped zinc oxide). According to various embodiments, a TCR sensor includes a ceramic material comprising GZO, wherein a concentration of Ga in the Ga-doped ZnO ranges between about 0.1 and 15 wt %. In some embodiments, a TCR sensor includes a ceramic material comprising GZO, wherein a concentration of Ga in the Ga-doped ZnO ranges between about 0.1 and 8 wt %. In other embodiments, a TCR sensor includes a ceramic material comprising GZO, wherein a concentration of Ga in the Ga-doped ZnO ranges between about 0.1 and 4 wt %.

In accordance with some embodiments, Al- and Ga-doped ZnO films having a thickness of between about 3-50 nm can be used to fabricate TCR sensors suitable for incorporation in a head transducer. According to other embodiments, Al- and Ga-doped ZnO films having a thickness of between about 5-30 nm can be used to fabricate TCR sensors suitable for incorporation in a head transducer. In further embodiments, Al- and Ga-doped ZnO films having a thickness of between about 5-20 nm can be used to fabricate TCR sensors suitable for incorporation in a head transducer.

In accordance with some embodiments, various formulations of impurity-doped ZnO films can be used in TCR sensors suitable for incorporation in a head transducer. A representative list of ZnO dopants is provided below in Table 1. The dopant content (in wt %) and resistivity (×10−4Ωcm) for each ZnO dopant is also provided in Table 1 below.

Impurity-doped ZnO films with a resistivity on the order of 10−4Ωcm can be prepared using a variety of processes, including magnetron sputtering (MSP), pulsed laser deposition (PLD), vacuum arc plasma evaporation (VAPE), metal organic molecular beam deposition (MOMBD), and metal organic chemical vapor deposition (MOCVD). For example, AZO and GZO films for TCR sensors with a resistivity on the order of 1×10−4Ωcm can be prepared using PLD and VAPE. AZO films for use in TCR sensors with a resistivity on the order of 1×10−5Ωcm can be prepared by PLD.

In accordance with other embodiments, thin films of conducting ZnO for use in various TCR sensor embodiments can be produced by a variety of techniques, including pulsed laser deposition at room temperature, atomic layer deposition between about 90 and 200° C., and reactive magnetron sputtering, all of which are well known recording head and/or microelectronic fabrication processes. The following are known examples of preparing AZO films adaptable for use in TCR sensors according to various embodiments:

Aluminum doped zinc oxide (AZO) films were prepared by radio frequency magnetron sputtering on glass or Si substrates using specifically designed ZnO targets containing different amount of Al2O3powder as the Al doping source. The structural, electrical, and optical properties of the AZO films were investigated in terms of the preparation conditions, such as the Al2O3content in the target, RF power, substrate temperature, and working pressure. The doping concentration in the film was 1.9 at. % for 1 wt % Al2O3target, 4.0 at. % for 3 wt % Al2O3target, and 6.2 at. % for 5 wt % Al2O3target. The resistivity of the AZO film prepared with the 3 wt % Al2O3target was ˜4.7×10−4Ωcm, and depends mainly on the carrier concentration. The optical transmittance of a 1500-Å-thick film at 550 nm, for example, is ˜90%.

Transparent conductive Al doped zinc oxide (ZnO: Al, AZO) thin films with a thickness of 4 nm were prepared on the Corning glass substrate by radio frequency magnetron sputtering. The properties of the AZO thin films were investigated at different substrate temperatures (from 27 to 15° C.) and sputtering power (from 15 to 25 W). The structural, optical and electrical properties of the AZO thin films were investigated. The optical transmittance of about 78% (at 415 nm)-92.5% (at 63 nm) in the visible range and the electrical resistivity of 7×10−4Ωcm (175.2 Ω/sq) were obtained.

Other TCO materials can be used in TCR sensors according to various embodiments. Examples include impurity-doped In2O3and SnO2, and multicomponent oxides composed of combinations of these binary compounds. Films of impurity-doped In2O3and SnO2provide for resistivity values on the order of 1×10−4Ωcm.

Table 2 below lists a variety of TCO materials that can be used in TCR sensors of a head transducer in accordance with various embodiments.

TABLE 2MaterialDopant or CompoundSnO2Sb, F, As, Nb, TaIn2O3Sn, Ge, Mo, F, Ti, Zr, Hf, Nb, Ta, W, TeZnOAl, Ga, B, In, Y, Sc, F, V, Si, Ge, Ti, Zr, HfZnO—SnO2Zn2SnO4, ZnSnO3ZnO—In2O3Zn2In2O5, Zn3In2O6In2O3—SnO2In4Sn3O12GaInO3, (Ga, In)2O3Sn, GeZnO—In2O3—SnO2Zn2In2O5—In4Sn3O12
According to some embodiments, a TCR sensor can comprise ZnO—In2O3films. In some embodiments, ZnO—In2O3films can be prepared at room temperature with an In content of about 75.5 and 90 at % by DC magnetron sputtering and VAPE, respectively. Such ZnO—In2O3films can exhibit a resistivity as low as 3×10−4Ωcm. In addition, ZnO—In2O3films having a thicknesses of less than 400 nm exhibit an average transmittance above 80% in the visible range. In other embodiments, a TCR sensor can comprise In4Sn3O12films. In accordance with some TCR sensor embodiments, a resistivity of 2×10−4Ωcm can be realized using In4Sn3O12films prepared with an Sn content of 50 at % on substrates at 350° C.

TCR sensors according to some embodiments can include TCO films having a structure of zinc oxide/tungsten doped indium oxide/zinc oxide (ZnO/IWO/ZnO). Such TCO films can be fabricated using a pulsed laser technique. A TCR sensor comprising ZnO/IWO/ZnO provides for low resistivity (e.g., 1.24×10−4Ω·cm) and good transmittance (e.g., >about 75-80%). Resistivity of ZnO/IWO/ZnO films, for example, can range between about 1.04×10−4Ω·cm to 8.19×10−3Ω·cm with ZnO film thickness increasing between about 0 nm to 90 nm, respectively.

Various embodiments of the disclosure are directed to TCR sensors comprising ITO (indium tin oxide) films. In some embodiments, ITO thin films have a resistivity on the order of 1×10−4Ωcm. Some ITO embodiments provide for low resistivity on the order of 1×10−5Ωcm. Such low resistivity ITO films are typically prepared with impurity-doped binary compounds. ITO films suitable for use in TCR sensors of a head transducer can be fabricated using a variety of processes. The following processes can be used to produce ITO films with low resistivity on the order of 1×10−5Ωcm:

Depending on the particular ceramic or TCO materials used in a TCR sensor, resistivities in the range of about 10−4Ωcm and 10−3Ωcm can be obtained according to various embodiments, which would result in a thermal sensor having a resistance in the 5 kΩ to 500 kΩ range. In general, a thermal sensor having a resistance in the 5 kΩ to 500 kΩ range may be considered a high-impedance sensor, which would require an appropriately designed preamplifier to drive and sense such a high-impedance thermal sensor. It is well within the skill level of amplifier designers to design a preamplifier suitable for driving and sensing a high-impedance TCR sensor according to various embodiments of the disclosure.

FIGS. 3 and 4are schematics that illustrate structures and features that may be included in the components according to embodiments ofFIG. 1.FIGS. 3 and 4are nearly the same in terms of components and configuration, but differ in the location of a thermal sensor situated at or near an air bearing surface of the head transducer.FIGS. 3 and 4show cross-sections of a head transducer300in accordance with various embodiments. The portion of head transducer300illustrated inFIGS. 3 and 4includes three heat sources; a write coil340, an NFT320, and a heater350, that cause a thermal protrusion of an air bearing surface303of the head transducer300. One or more TCR sensors can be located at or near specified locations of the air bearing surface303, particularly near heat producing components of the head transducer300.

In the embodiment shown inFIG. 3, a thermal sensor360is located on the pole side of the head transducer300, between a writer335and a waveguide330which is optically coupled to NFT320. In one configuration, at least a portion of thermal sensor360is co-extensive with a portion of the return pole315of the writer335along an axis normal to the air bearing surface. In the embodiment shown inFIG. 4, a thermal sensor460is located on the non-pole side of the head transducer300, outside of the magnetic pathway defined between the write pole310and write return pole315. InFIG. 4, thermal sensor460is situated at or near the air bearing surface303between NFT320or waveguide330and a writer heater350.

With further reference toFIGS. 3 and 4, the head transducer300may comprise a relatively thick substrate on which is disposed the multiplicity of thin layers. The layers cooperate to define the respective components of the head transducer300. The layers include a multiplicity of layers tailored to form, for example, a magnetic writer335and a magnetic reader334. The layers may also be patterned to form coils340which, when energized with an electrical current, produce a magnetic field passes through the writer335and through a portion of the writeable medium375. One end or terminus310(referred to as a write pole) of the writer335may be configured to produce a high flux density of the magnetic field. Another end or terminus315(referred to as a return pole) of the writer335, coupled to the write pole310via a yoke of the writer, may be configured to produce a lower flux density.

The layers of the head transducer300also layers tailored to form a (passive) waveguide330, an NFT320, and the thermal sensor360/460. A laser (not shown inFIGS. 3 and 4) may be formed in the head transducer layers, may be mounted on the heat transducer or may be disposed in a cavity in the head transducer and is optically coupled to the NFT320through the waveguide330.

The writeable medium375may be configured in any known way, but typically it includes a plate or substrate332on which at least a hard magnetic layer344is deposited or otherwise formed. A small portion or spot343of the layer344may be heated sufficiently to reduce the coercivity of the material enough so that the magnetic field from the magnetic write pole310is strong enough to change the magnetization direction of the recording layer344. Bits of information may then be recorded in the form of a perpendicular upward downward magnetization direction for a series of magnetic domains in the layer344.

The heating of the spot343in connection with the write procedure may be provided directly by the NFT320and indirectly by the laser. When the laser is energized, laser light is emitted from the laser is coupled into the waveguide, whether by end-fire coupling or otherwise. The laser light is conveyed to a distal end330bof the waveguide330. In some cases, the distal end may correspond to a focal point or focal region of a solid immersion mirror (SIM) or a solid immersion lens (SIL). Located at or near the distal end330bis the NFT320, which may be formed as part of the plurality of layers. The NFT320utilizes plasmons to convert the power density of the incident laser light into a high power density in a near-field region that is typically smaller than the diffraction limit for the laser light. The high power density provided by the NFT320in the near-field region is absorbed by the nearby writeable medium375to produce localized heating of the spot343. By positioning an emitting end of the NFT320close enough to the write pole310of the writer335, at least a portion of the heated spot343can be exposed to the high magnetic flux emitted by the write pole310before passing out of range (due to the relative motion of the writeable medium375) so that the magnetic field at the write pole310is capable of changing the magnetization direction of the spot343.

The heating of spot343also causes protrusion of a region of the air bearing surface303of the head300. To measure the temperature change and corresponding protrusion, one or more thermal sensors, e.g., thermal sensors360and460, can be located proximate the NFT329and/or write310or return315poles in a protrusion region of the air bearing surface303.

The NFT320may be a suitably sized pin or other structure and may be made of a metal such as gold or other suitable materials. The NFT320may have any suitable design known in the art. The NFT320is shown inFIGS. 3 and 4to be close to but separated from waveguide330, but in other embodiments the NFT320may be disposed within the waveguide330. In still other embodiments, the laser may be integrated into the head transducer and the waveguide may be omitted. In an integrated laser configuration, the NFT320may couple directly to the integrated semiconductor laser.

With reference toFIG. 5, a method of sensing temperature in a head transducer is set forth in accordance with various embodiments. The method shown inFIG. 5involves activating502one or more heat producing components of a transducer head. The heat producing components of the head transducer include an NFT, a write pole, and a writer heater, for example. The method ofFIG. 5further involves sensing504temperature at a head transducer location subject to high temperature using a high temperature TCR thermal sensor, such as those described hereinabove.

FIG. 6illustrates a method for sensing temperature in a head transducer in accordance with various embodiments. The method shown inFIG. 6involves activating602one or more heat producing components of a transducer head. The heat producing components of the head transducer include an NFT, a write pole, and a writer heater, for example. The method ofFIG. 6further involves thermally actuating604a protrusion region of the head transducer's air bearing surface by the one or more heat producing components. The method ofFIG. 6also involves sensing606temperature at the protrusion region using a high temperature TCR thermal sensor, such as those described hereinabove.

FIG. 7illustrates a method for sensing head-media separation and/or contact according to various embodiments. The method shown inFIG. 7involves activating702one or more heat producing components of a transducer head. The heat producing components of the head transducer include an NFT, a write pole, and a writer heater, for example. The method ofFIG. 7further involves producing704a signal by a high-temperature TCR sensor that varies in relation to a change in separation between the air bearing surface of the transducer head and a magnetic storage medium. The signal, e.g., resistance or rate of change of resistance, can also be indicative of contact between the air bearing surface and magnetic storage medium in proximity to the air bearing surface as discussed above.

FIG. 8illustrates a method for sensing head-media separation and/or contact according to various embodiments. The method shown inFIG. 8involves activating802one or more heat producing components of a transducer head. The heat producing components of the head transducer include an NFT, a write pole, and a writer heater, for example. The method ofFIG. 8also involves thermally actuating804a protrusion region of the head transducer's air bearing surface by the one or more heat producing components of the transducer head (e.g., NFT, write pole, writer heater). The method ofFIG. 8further involves producing806a signal by a high-temperature TCR sensor that varies in relation to a change in separation between the air bearing surface of the transducer head and a magnetic storage medium. The signal, e.g., resistance or rate of change of resistance, can also be indicative of contact between the air bearing surface and magnetic storage medium in proximity to the air bearing surface as discussed above.

In some embodiments, the TCR sensor signal can be combined with a second thermal sensor signal produced by a second thermal sensor located away from the protrusion region, such as at a transducer location not influenced by the thermal boundary condition at the close point or air bearing surface. This second TCR sensor can be, but need not be, a high-temperature TCR sensor of the kind disposed adjacent the NFT. For example, the second TCR sensor can be of a conventional design. The common mode of the two sensor signals can be subtracted or canceled, such that the resulting signal is indicative of head-media separation changes and/or head-media contact.

Various techniques can be employed for detecting head-media contact and separation according to embodiments of the disclosure, such as those disclosed in the commonly owned patent references cited hereinabove. According to one approach, a measure of the head-to-medium interface cooling condition is the rate of the temperature rise over heater power, or ΔR/ΔP. The ratio ΔR/ΔP decreases with a better cooling condition, and reaches a minimum at head-media contact. The ratio ΔR/ΔP increases again after head-media contact due to frictional heating. The head-media contact can be detected by monitoring the metric ΔR/ΔP instead of the head modulation. The metric ΔR/ΔP deviates (drops) from a linear trend first before it reaches the minimum. This signature indicates the cooling caused by initiation of the head-media contact. The minimum point of ΔR/ΔP indicates full head-media contact and that heat is generated by friction. Various methods of detecting head-media contact utilize the rate of the temperature rise in a head transducer over heater power supplied to a head transducer heater. A change in phase of the thermal sensor signal relative to a reference signal can also be used to detect head-media contact.