Near-field transducer of heat-assisted recording head having bottom and middle disks with different recessions from media-facing surface

A near field transducer has a bottom disc with a first surface facing a write pole of a recording head. The bottom disc is recessed from a media-facing surface of the recording head by a distance R. An anchor layer is stacked on the first surface of the bottom disc and has an enlarged part with a peripheral shape corresponding to that of the bottom disc. The anchor layer further has a peg that extends from an end of the enlarged part towards the media facing surface, the end of the enlarged part recessed from the media facing surface by the distance R. A middle disc is on a second surface of the anchor layer. The middle disc is recessed from the media-facing surface a distance MDSCR that is greater than the distance R. A heat sink is stacked on a third surface of the middle disc. The heat sink is recessed from the media-facing surface by at least a distance TPH that is greater than the distance MDSCR.

SUMMARY

The present disclosure is directed to a near-field transducer of heat-assisted recording head having bottom and middle disks with different recessions from media-facing surface. In one embodiment, a near field transducer has a bottom disc formed of a first material and has a first surface facing a write pole of a recording head. The bottom disc is recessed from a media-facing surface of the recording head by a distance R. An anchor layer is stacked on the first surface of the bottom disc and has an enlarged part with a peripheral shape corresponding to that of the bottom disc. The anchor layer further has a peg that extends from an end of the enlarged part towards the media facing surface. The anchor layer is formed of a second material that is more mechanically robust and less optically efficient than the first material. The anchor layer has a second surface that faces the write pole, the end of the enlarged part recessed from the media facing surface by the distance R. A middle disc is on the second surface of the anchor layer. The middle disc is recessed from the media-facing surface a distance MDSCR that is greater than the distance R. The middle disc has a third surface that faces the write pole. A heat sink is stacked on the third surface of the middle disc. The heat sink is recessed from the media-facing surface by at least a distance TPH that is greater than the distance MDSCR. The heat sink is thermally coupled to the write pole.

DETAILED DESCRIPTION

The present disclosure is generally related to heat-assisted magnetic recording (HAMR), also referred to as energy-assisted magnetic recording (EAMR), thermally-assisted recording (TAR), thermally-assisted magnetic recording (TAMR), etc. In a HAMR device, a source of optical energy (e.g., a laser diode) is integrated with a recording head and couples optical energy to a waveguide or other light transmission path. The waveguide delivers the optical energy to a near-field transducer (NFT). The NFT concentrates the optical energy into a tiny optical spot in a recording layer, which raises the media temperature locally, reducing the writing magnetic field required for high-density recording.

Generally, the NFT is formed by depositing thin-film of a plasmonic material such as gold, silver, copper, etc., at or near an integrated optics waveguide or some other delivery system. When exposed to laser light that is delivered via the waveguide, the light generates a surface plasmon field on the NFT. The NFT is shaped such that the surface plasmons are directed out of a surface of the write head onto a magnetic recording medium.

A magnetic write pole tip is located near the NFT and generates the magnetic field used in recording the data to the recording medium. A coil encompasses a write pole structure away from the NFT, and applying a current to the coil induces the magnetic field at the tip. When the recording medium is heated by the optical energy, the coercivity in the hotspot is lowered such that the magnetic field can change the magnetic orientation within the hotspot, not affecting the recording medium outside the hotspot. Because the hotspot is much smaller than the area affected by the magnetic field, HAMR allows recording much smaller bits than would be possible using the write pole alone.

The use of an optical NFT and magnetic pole in close proximity can make it difficult to optimize performance of one or both devices. For example, the size, shape and materials of the write pole can affect efficient plasmonic resonance of the NFT. Similarly, the need to have an NFT and other devices near the media-facing surface can limit the size and shape of the write pole tip, which can affect the strength and orientation of the magnetic field generated at the tip. In this disclosure, various features of an NFT and write pole are described that can aid in optimizing performance of both the write pole and NFT.

In reference now toFIG. 1, a perspective view shows a read/write head100according to an example embodiment. The read/write head100may be used in a magnetic data storage device, e.g., HAMR hard disk drive. The read/write head100may also be referred to herein interchangeably as a slider, head, write head, read head, recording head, etc. The read/write head100has a slider body102with read/write transducers108at a trailing edge104that are held proximate to a surface of a magnetic recording medium (not shown), e.g., a magnetic disk.

The illustrated read/write head100is configured as a HAMR device, and so includes additional components that form a hot spot on the recording medium near the read/write transducers108. These HAMR components include an energy source106(e.g., laser diode) and a waveguide110. The waveguide110delivers electromagnetic energy from the energy source106to a near-field transducer (NFT) that is part of the read/write transducers108. The NFT achieves surface plasmon resonance and directs the energy out of a media-facing surface112to create a small hot spot in the recording medium.

InFIG. 2, a cross-sectional views show details of a slider body102according to an example embodiment. The waveguide110includes a core200, top cladding layer202, side cladding layer204, and bottom cladding206. A waveguide input coupler201at a top surface203of the slider body102couples light from the light source106to the waveguide110. The waveguide input coupler201receives light from the light source106and transfers the light to the core200. The waveguide core200is made of dielectric materials of high index of refraction. The cladding layers202,204,206are each formed of a dielectric material having a refractive index lower than the core200.

The core200delivers light to an NFT208that is located within the side cladding layer204at the media-facing surface112. A write pole210(which is a distal part of a magnetic write transducer) is located near the NFT208. The magnetic write transducer may also include a yoke, magnetic coil, return pole, etc. (not shown). A heat sink212thermally couples the NFT208to the write pole210. The magnetic coil induces a magnetic field through the write pole210in response to an applied current. During recording, an enlarged portion208a(e.g., a rounded disk) of the NFT208achieves surface plasmon resonance in response to light delivered from the core, and the plasmons are tunneled via a peg208bout the media-facing surface112. The energy delivered from the NFT208forms a hotspot220within a recording layer of a moving recording medium222. The write pole210sets a magnetic orientation in the hotspot220, thereby writing data to the recording medium.

InFIGS. 3 and 4, perspective and side cross-sectional views show details of the NFT300according to an example embodiment. The NFT208includes a bottom disc300formed of a first material (e.g., gold) and having a first surface300afacing the write pole210. The bottom disc300is recessed from the media-facing surface112by a distance R (seeFIG. 4). An anchor layer302is stacked on the first surface300aof the bottom disc300and has an enlarged part302awith a peripheral shape corresponding to that of the bottom disc300.

The peg208bis part of the anchor layer302and extends from an end302aa(seeFIG. 4) of the enlarged part302aof the anchor layer302towards the media facing surface112. The anchor layer302formed of a second material (e.g., rhodium) that is more mechanically robust (although possibly less optically efficient than) the first material. The anchor layer302has a second surface302bthat faces the write pole210. The end302aaof the enlarged part302aof the anchor layer302is also recessed from the media facing surface112by the distance R.

A middle disc304is stacked on the second surface302bof the anchor layer302. The middle disc304is recessed from the media-facing surface112a distance MDSCR (seeFIG. 4) that is greater than the distance R. The middle disc has a third surface304athat faces the write pole210. The heat sink212is stacked on the third surface304aof the middle disc. The heat sink212is recessed from the media-facing surface by at least a distance TPH (seeFIG. 4) that is greater than the distance MDSCR. The heat sink212is thermally coupled to the write pole210.

In this example, a pole coating306is shown located between the heat sink212and the write pole210. The pole coating306extends towards the media-facing surface112such that it also separates the middle disc304from the write pole210. The pole coating308is formed of a material (e.g., Ir) that inhibits material diffusion between the write pole210and the NFT208. Because of the pole coating308, the heat sink212is recessed from the media-facing surface112by the distance TPH plus a thickness of the pole coating308.

The write pole210has a side210aextending from the media-facing surface112the distance TPH. Due to this geometry, a part of the middle disc304partially fills in a gap312between the anchor layer208band the side of the write pole210a. Also seen in this example is a heat diffuser310that is located in a recess of the write pole210away from the media-facing surface112. The heat diffuser310helps carry heat from the heat sink212away from the media-facing surface112.

InFIG. 5, a top cutaway view shows additional details of the NFT208according to an example embodiment. Generally, the middle disc304, anchor layer302and bottom disc300collectively form the enlarged part208aof the NFT208. The enlarged part208aachieves surface plasmon resonance in response to being illuminated by a waveguide and has a peripheral shape that directs the surface plasmons to the peg208b. The enlarged part208ais a stadium peripheral shape in this example, although other shapes may be used, including circular, rectangular, or a combination thereof (e.g., curved on one end facing the media-facing surface and flat on an end facing away from the media-facing surface). The enlarged part302aof the anchor layer302in this example has a peripheral shape that corresponds to a full periphery of the bottom disc300, such that the bottom disc300is completely covered by the anchor layer302in the substrate-parallel plane (the xz-plane).

InFIG. 6, a top cutaway view shows additional details of the NFT208according to another example embodiment. An alternatively configured anchor layer602includes the peg208bas in previously described embodiments joined with an enlarged part602a. In this example, the alternatively configured enlarged part602ahas a peripheral shape that only partly corresponds to that of the bottom disc300. Both the bottom edges of disc300and the anchor layer602have the same peripheral shape along a bottom edge208aaof the enlarged part208aof the NFT208. A top edge602aaof the enlarged anchor layer part602ais flat, although may have other shapes, e.g., convex or concave curves, convex or concave piecewise linear, etc. The top edge602aamay be located anywhere relative to the bottom disc300, e.g., below or above middle604of the NFT208.

By configuring the NFT and write pole with separate MDSC recess distances and TPH distances, the performance of the NFT and the write pole can be separately optimized. The MDSCR distance will define optical performance (thermal gradient, NFT temperature) without significantly impacting magnetic performance of the write pole. The TPH distance will define magnetic performance without significantly impacting optical performance of the NMFT. The purpose of MDSCR is to separate optics from magnetics while changing TPH. It is estimated that a 10-20% magnetic field increase can be had with a 100˜200 nm long TPH. In Table 1 below, various other performance measures of a HAMR head are shown based on simulations of the NFT and pole design described herein with 65 nm MDSC. Note that the diffuser recess shown in Table 1 corresponds to the DR dimension shown inFIG. 4. The other columns in Table 1 are, in order from left to right, downtrack thermal gradient (DT-TG), crosstrack TG (CT-TG), adjacent track erasure (ATE), and delta temperature for the NFT peg, NFT enlarged part, and write pole.

This analysis shows small changes in thermal gradient with relatively large values of TPH. The NFT and write pole temperatures increase5-10K with relatively large values of TPH. InFIGS. 7-11, graphs show the simulation results for different values of MSCDR, with TPH=155 nm. Generally, a value of MSCDR=65 nm is optimal for the values used in this simulation.