Heat assisted magnetic recording (HAMR) head with main pole with narrow plasma recesses

Abstract

A heat assisted magnetic recording (HAMR) head has a slider having a gas bearing surface (GBS). The slider supports a near field sensor (NFT) having an output tip at the GBS and a main pole having a recess containing a plasmon material in a surface facing the NFT. The plasmon recess has a leading edge at the GBS, the leading edge having a cross-track width equal to or less than a cross-track width of a widest portion of the NFT output tip, and a trailing edge recessed from the GBS. A thermal diverter is located between the NFT and the main pole to allow heat transfer away from a spot of light generated by the NFT output tip and in contact with a region of the plasmon recess proximate the trailing edge.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of the entire contents of U.S. non-provisional patent application No. 17 / 821,166, filed on August 20, 2022, entitled “HEAT-ASSISTED MAGNETIC RECORDING (HAMR) HEAD WITH MAIN POLE HAVING NARROW PLASMONIC RECESS” and hereby incorporates such contents by reference for all purposes. Technical Field

[0003] The present invention relates generally to heat-assisted magnetic recording (HAMR) disk drives in which data is written while a magnetic recording layer on the disk is at an elevated temperature, and more particularly to an improved HAMR head. Background Art

[0004] In conventional magnetic recording, thermal instability of the magnetization stored in the recording medium can lead to loss of recorded data. To avoid this, a material with high magnetocrystalline anisotropy (K u ) medium. However, increasing K u It also increases the coercivity of the media, which can exceed the write field capability of the write head. Since the coercivity of the magnetic material of the recording layer is known to be temperature dependent, one proposed solution to the thermal stability problem is heat-assisted magnetic recording (HAMR), where high K u The magnetic recording material is locally heated during writing via the main pole to reduce the coercivity sufficient for writing, but where the coercivity / anisotropy is high enough to achieve thermal stability of the recorded bits at the ambient temperature of the disk drive (i.e., normal operating temperature or "room temperature" of about 15°C-30°C). In some proposed HAMR systems, the magnetic recording material is heated to near or above its Curie temperature. The recorded data is then read back at ambient temperature by a conventional magnetoresistive read head. HAMR disk drives have been proposed for conventional continuous media, in which the magnetic recording material is a continuous layer on the disk, and for bit patterned media (BPM), in which the magnetic recording material is patterned into discrete data islands or "bits."

[0005] One type of proposed HAMR disk drive uses a laser source and an optical waveguide coupled to a near-field transducer (NFT) for heating a recording layer on the disk. A "near-field" transducer refers to "near-field optics" in which light is passed through an element having sub-wavelength characteristics, and the light is coupled to a second element (such as a substrate such as a magnetic recording layer) positioned at a sub-wavelength distance from the first element to produce a heated light spot on the recording layer. The NFT is typically positioned at a gas bearing surface (GBS) of a gas bearing slider that also supports a read head and a write head and rides or "files" above the disk surface. The write head includes a main pole having a tip at the GBS near the NFT that directs a magnetic field to the recording layer as the NFT heats the recording layer. A heat shunt of high thermal conductivity material is positioned between the NFT and the main pole to allow heat to be transferred away from the light spot to a heat sink material located on the cross-track side of the main pole.

[0006] An NFT with a generally triangular or trapezoidal output tip is described in US 8,705,327 B2, assigned to the same assignee as the present patent application. In this NFT, evanescent waves generated at the surface of the waveguide couple to surface plasmons excited on the surface of the NFT and generate a strong optical near field at the vertex of the output tip. Summary of the invention

[0007] Importantly, HAMR disks have a high thermal gradient in the recording layer, which means that there is a sharp temperature drop at the edge of the bit being recorded. It has been proposed to add a full film layer of plasmonic material on the main pole and facing the NFT to increase the thermal gradient, as described in US10,121,496B1. However, this plasmonic layer increases the gap between the NFT and the main pole, thereby reducing the magnetic field strength at the recording layer. In addition, the addition of the plasmonic layer increases the temperature of the NFT.

[0008] In an embodiment of the present invention, the main pole has a recess containing plasmon material in its surface facing the NFT, rather than a full film under the main pole, but a significant portion of the surface of the main pole facing the NFT remains facing the NFT layer, so there is no gap between that portion of the main pole and the NFT. The plasmon material includes a plasmon tip at the output end of the main pole at the GBS, which is aligned with the NFT in the along-track direction and has a cross-track width equal to or less than the cross-track width of the NFT tip. By reducing the width of the plasmon tip at the GBS, the NFT temperature can be reduced.

[0009] The plasmon material in the recess may extend from the plasmon tip at the GBS to part or all of the height of the main pole, and may have a cross-track width that increases or decreases in a direction away from the plasmon tip. In embodiments where the cross-track width of the plasmon material increases in a direction away from the GBS, the plasmon material may exhibit an opening angle having a curved shape. The along-track thickness of the plasmon material in an area away from the GBS may be the same as, less than, or greater than, the along-track thickness of the plasmon tip at the GBS. An optional layer of dielectric material may be located in the recess between the plasmon material and the main pole. The gap material between the plasmon tip and the NFT may be a waveguide cladding material or a material selected from a wide selection of other materials.

[0010] For a more complete understanding of the nature and advantages of the present invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a top view of a heat-assisted magnetic recording (HAMR) disk drive according to an embodiment of the present invention.

[0012] 2 is a side cross-sectional view of a portion of a HAMR disk and a gas bearing slider used in a HAMR disk drive according to the prior art, the side cross-sectional view not being drawn to scale due to the difficulty in illustrating very small features.

[0013] 3A is a side cross-sectional view of the layers of material making up the main and primary poles, near field transducer (NFT), and waveguide according to the prior art and shown relative to a recording layer on a disk.

[0014] 3B is a perspective view of a main pole, primary pole, NFT, waveguide, and heat sink material on the cross-track side of the main pole according to the prior art.

[0015] 4A is a cross-sectional view of a HAMR head having a prior art full-film plasmon layer on the NFT-facing surface of the main pole.

[0016] 4B and 4C are views of sections BB and CC of FIG. 4A , respectively.

[0017] Figure 5A is a cross-sectional view of a HAMR head according to one embodiment of the present invention.

[0018] Figure 5B and Figure 5C They are Figure 5A View of sections BB and CC.

[0019] Figure 5D yes Figure 5A View of the gas bearing surface (GBS).

[0020] Fig. 6A is a view of the NFT-facing surface of the main pole of one embodiment of the present invention, wherein the plasmon recess has a height that does not extend to the rear end facing the NFT surface.

[0021] Figure 6B is a view of the NFT-facing surface of the main pole of one embodiment of the present invention showing a plasmon recess with a trailing edge having a cross-track width that is less than the cross-track width at the GBS.

[0022] Figure 6C is a view of the NFT-facing surface of the main pole of one embodiment of the present invention showing the plasmon recess with a flared cross-track side.

[0023] Fig. 7A is a GBS view of an embodiment of the present invention, in which the cross-track width of the plasmon pit increases in the along-track direction.

[0024] Figure 7B is a GBS view of an embodiment of the present invention, where the plasmon wells have different shapes along the track direction and have an optional layer of dielectric material.

[0025] Figure 7C is a GBS view of one embodiment of the present invention showing the gap material between the plasmon tip and the NFT.

[0026] Figure 8 is a side cross-sectional view of one embodiment of the present invention showing a plasmon recess having different thicknesses in the along-track direction. DETAILED DESCRIPTION

[0027] Figure 1 1 is a top view of a heat assisted recording (HAMR) disk drive 100 according to an embodiment of the present invention. Figure 1 , a HAMR disk drive 100 is depicted as having a disk 150 having a magnetic recording layer 31 of a conventional continuous magnetic recording material arranged in radially spaced circular tracks 118. Only a few representative tracks 118 are shown near the inner and outer diameters of the disk 150. However, the recording layer may be a bit patterned media (BPM) layer having discrete data islands rather than a conventional continuous magnetic recording layer.

[0028] The drive 100 has a housing or base 112 that supports an actuator 130 and a drive motor for rotating a magnetic recording disk 150. The actuator 130 may be a voice coil motor (VCM) rotary actuator having a rigid arm 131 and rotating about a pivot 132 (as shown by arrow 133). The head suspension assembly includes a suspension 135 and a head carrier such as a gas bearing slider 120, which has one end attached to the end of the actuator arm 131 and is attached to the other end of the suspension 135. The suspension 135 allows the slider 120 to remain very close to the surface of the disk 150 and enables it to "tilt" and "roll" on a gas (usually air or helium) bearing generated by the disk as the disk 150 rotates in the direction of arrow 20. The slider 120 supports a HAMR head (not shown) that includes a magnetoresistive read head, an inductive write head, a near field transducer (NFT), and an optical waveguide. A semiconductor laser 88 having a wavelength of 780 nm to 980 nm may be used as a HAMR light source and is depicted as being supported on top of a slider 120. Alternatively, the laser may be positioned on a suspension 135 and coupled to the slider 120 through an optical channel. Movement of the actuator 130 allows the HAMR head on the slider 120 to access different data tracks 118 on the disk 150 as the disk 150 rotates in the direction of arrow 20. The slider 120 is typically formed of a composite material such as a composite of aluminum oxide / titanium carbide (Al2O3 / TiC). Figure 1 Only one disk surface with an associated slider and read / write head is shown in FIG, but typically multiple disks are stacked on a hub rotated by a spindle motor, with a separate slider and HAMR head associated with each surface of each disk.

[0029] In the following figures, the X-axis represents the axis perpendicular to the gas bearing surface (GBS) of the slider, the Y-axis represents the track width or cross-track axis, and the Z-axis represents the along-track axis. FIG. 2 is a schematic cross-sectional view showing an example of a configuration of a HAMR head according to the prior art. In FIG. 2 , a magnetic disk 150 is depicted as having a recording layer 31, which is a conventional continuous magnetic recording layer of a magnetizable material having magnetized regions or “bits” 34. The gas bearing slider 120 is supported by a suspension 135 and has a GBS facing the magnetic disk 150 and supporting a magnetic write head 50, a read head 60, and magnetically permeable read head shields S1 and S2. The recording magnetic field is generated by a write head 50, which is composed of a coil 56, a primary pole 53 for transmitting the flux generated by the coil 56, a main pole 52 connected to the primary pole 53, and a return pole 54 coupled to the primary pole 53 and the main pole 52. The magnetic field generated by the coil 56 is transmitted via the primary pole 53 to the main pole 52 arranged near the optical near field transducer (NFT) 74. FIG. 2 shows a write head 50 with a known "flat" coil 56, in which the coil segments lie in substantially the same plane. However, as an alternative, the coil may be a known "spiral" coil, in which the coil is wound around the primary magnetic pole 53. At the moment of recording, the recording layer 31 of the disk 150 is heated by the optical near field generated by the NFT 74, and at the same time, the area or "bit" 34 is magnetized and thus written to the recording layer 31 by applying the recording magnetic field generated by the main pole 52.

[0030] The semiconductor laser 88 is mounted to the top surface of the slider 120. An optical waveguide 73 for guiding light from the laser 88 to the NFT 74 is formed in the slider 120. A material that ensures that the refractive index of the core material of the waveguide 73 is greater than the refractive index of the surrounding cladding material (not shown) can be used for the waveguide 73. For example, Al2O3 can be used as the cladding material, and TiO2, T2O5, and SiOxN y Can be used as core material. Alternatively, SiO2 can be used as cladding material, and Ta2O5, TiO2, Nb2O5, SiOxN y Or Ge-doped SiO2 is used as the core material. The waveguide 73 that transmits light to the NFT 74 is preferably a single-mode waveguide.

[0031] FIG3A is a side cross-sectional view of a prior art HAMR head and shows the material layers that make up the primary pole 53, the main pole 52, the NFT 74, and the waveguide 73, and is shown relative to a disk 150 having a recording layer 31. The main pole 52 is typically a layer of high magnetic moment material (such as FeCo) and has a pole tip 52a located at the GBS and a surface 52b facing the NFT 74. The waveguide 73 is a core material layer that is generally parallel to the main pole 52 layer, has a length that is orthogonal to the GBS, and a waveguide end 73d is located at the GBS. The waveguide 73 has a surrounding cladding material 77 and a generally flat surface 73c facing and parallel to the NFT 74 layer. The NFT 74 layer is a conductive low-loss metal (preferably Au, but may also be Ag, Al, Cu, Rh, Ir, or alloys thereof), is generally parallel to the waveguide 73 layer and the main pole 52 layer, and is positioned between and spaced apart from the waveguide 73 layer and the main pole 52 layer. The NFT 74 layer has a surface 74a facing the waveguide surface 73c and spaced apart from the waveguide surface. The NFT 74 layer has an output tip 80 substantially at the GBS. When light is introduced into the waveguide 73, an evanescent wave is generated at the surface 73c and coupled to the surface plasmon excited on the surface 74a of the NFT 74. Arrow 23 shows the propagation direction of the light in the waveguide 73, and arrow 24 shows the polarization direction of the light. The surface plasmon propagates to the output tip 80. The output tip 80 has a vertex 80a facing the main pole tip 52a and a rear edge 80b facing the waveguide surface 73c. ​​At the vertex 80a, an optical near-field point is generated in the space between the output tip vertex 80a and the main pole tip 52a at the GBS. The main pole tip 52a applies a magnetic field at the light point. A heat shunt 90 of a material with high thermal conductivity such as Au, Ag or Cu may be positioned between the NFT 74 and the main pole 52 to allow heat to transfer from the optical point to a heat sink material located on the cross-track side of the main pole 52. Heat shunts are described in US 8,619,516 B1, assigned to the same assignee as the present application.

[0032] 3B is a perspective view of a prior art HAMR head, and shows a heat sink material 92 in contact with the heat shunt 90, as well as the main pole 53, the main pole 52, the NFT output tip 80, and the waveguide end 73d. The heat sink material 92 is positioned on the cross-track side of the main pole 52 and connected to the heat shunt 90. If the heat sink material 92 contains an element that can diffuse into the magnetic material of the main pole 52, such as Au or Cu, a diffusion barrier layer (not shown) is positioned between the main pole 52 and the heat sink material 92. The material of the diffusion layer can be, for example, Rh, Ru, In, Co, W, Rh oxide, Ru oxide, indium oxide, or TiN, and its thickness is preferably in the range of 5nm to 10nm. If the heat sink material 92 is selected from a material that is unlikely to diffuse into the main pole 52, such as Ru or Rh, a diffusion layer is not required.

[0033] A HAMR head may include a full film layer of plasmonic material located below the main pole and facing the NFT, which has been proposed to increase the thermal gradient. However, adding a full film plasmonic layer also increases the temperature of the NFT. One definition of a plasmonic material is a metal or metal alloy whose extinction coefficient k is at least twice as large as the refractive index n at the wavelength of interest. Plasmonic materials provide excellent optical coupling to the NFT, which results in a limited heat source in the recording layer. Au, Ag, and Cu are examples of plasmonic materials.

[0034] FIG4A is a cross-sectional view of a HAMR head, and FIG4B and FIG4C are views of sections AA and BB, respectively, of a prior art full-film layer for illustrating plasmon materials. A full-film plasmon layer 95 is positioned on the NFT-facing surface 52b of the main pole 52 and extends from the front edge at the GBS to the rear edge 95a recessed from the GBS. As shown in FIG4A , the plasmon layer 95 increases the spacing between the entire main pole 52 and the NFT 74 in the along-track direction (Z axis), thereby reducing the magnetic field strength at the recording layer. As shown in FIG4C , because the plasmon layer is a full film that substantially covers the NFT-facing surface of the main pole, the cross-track width (Y direction) of the plasmon layer 95 is the same as the cross-track width of the main pole 52.

[0035] In an embodiment of the present invention, the surface of the main pole facing the NFT has a recess containing a plasmon material, which has a tip aligned with the NFT output tip in the along-track direction. When the plasmon material is added between the NFT and the main pole and the direction of light polarization is along the track direction (Z axis), due to the interaction between the charge at the top of the NFT and the image charge, an image charge is induced in the plasmon material in the recess, which generates a local optical near field between the NFT and the main pole. Because the optical near field is located in the gap between the plasmon tip and the NFT output tip, the thermal gradient in the recording layer can be increased. The non-recessed surface of the main pole facing the NFT is in contact with the thermal shunt, and the thermal shunt is also in contact with the plasmon material in the recess. Therefore, the spacing between the NFT and most of the main pole is not increased. The cross-track width of the plasmon tip at the GBS is equal to or less than the cross-track width of the widest part of the NFT at the GBS, which heats the temperature of the NFT to be smaller than the plasmon tip, which has the same cross-track width as the main pole output tip.

[0036] Figure 5A is a cross-sectional view of a HAMR head according to an embodiment of the present invention, Figure 5B and Figure 5C are views of cross sections BB and CC, respectively, of the HAMR head. Figure 5D Is from Figure 5A7 and shows the NFT output tip 80, the waveguide core end 73d and the surrounding cladding material 77. Figure 5D As shown, the surface 152b of the main pole 152 facing the NFT has a recess 195 ( FIG. 5B to FIG. 5C ), the recess contains plasmon material with tip 195a at the GBS. The distance between the main pole 152 and the NFT output tip 80 in the Z direction is larger at the recess 195, but the distance can be smaller at the sides of the recess because the recess 195 has a narrow cross-track width (Y direction). This results in a magnetic field that is larger than that of a full-film plasmon layer. Figure 5D In the embodiment, the cross-track width W1 of the tip 195a at the GBS is substantially smaller than the cross-track width W of the main pole at the GBS. MP .W MP Typically between about 150 nm and 250 nm. The widest width of NFT output tip 80, generally at GBS, is W at the portion farthest from plasmon recess tip 195a in the Z direction. NFT .W NFT Typically in the range of 50nm to 150nm. The narrowest width of NFT output tip 80, generally at GBS, is W closest to plasmon recess tip 195a in the Z direction. TOP . W1 is less than or equal to W NFT , but can also be less than or equal to W TOP The recorded track width is given by W TOP It is determined that it has a typical width between about 20nm and 40nm. Figure 5C As shown, plasmon recess 195 may extend from rear edge 193 to the entire height facing the NFT surface and have a height H substantially equal to the main pole. MP The height H1 (X direction) can also be selected to be smaller or larger than H MP The width W1 is substantially constant at this height.

[0037] like Figure 5A and Figure 5C As shown, if the plasmon material is Au or another material that can diffuse into the material of the main pole 152 (which is typically CoFe or a CoFeNi alloy), a thin diffusion barrier layer 140 is required between the main pole 152 and the plasmon material in the recess 195. Figure 5A As shown, diffusion barrier layer 140 may also be positioned between the plasmon material in recess 195 and heat shunt 190 to prevent diffusion of materials between these layers if different materials are used. Figure 5BAs shown, an optional thin diffusion barrier layer 140 may be located between the heat shunt 190 and the heat sink material 92. If the heat sink material is the same as the material of the heat shunt or the plasmon material, then no diffusion barrier layer is needed at those interfaces.

[0038] Plasmon recess 195 may be formed of the same material as that which may be used for the thermal shunt, such as Au, Ag, Rh, Ir, Cu, Al, Be, Mo, and W, or alloys thereof, and may thus be connected to the material of thermal shunt 190. This is preferred for ease of manufacture, but the plasmon recess may be formed of a different material than the thermal shunt. Materials that may be used for the plasmon recess include one or more of Au, Rh, Ir, Cu, Ag, Al, Ru, Cr, Pt, Ti, Fe, Co, Ni, Pd, Be, Mo, W, and AlN and TiN alloys.

[0039] Fig. 6A is similar to Figure 5C 1 and shows an embodiment in which the plasmon recess 195 with the tip 195a has a height H1 in the X direction that is less than the full height of the surface facing the NFT and less than the height H1 of the main pole. MP By keeping H1 smaller than H MP , the surface area of ​​the surface 152b facing the NFT increases, which increases the magnetic field strength.

[0040] Figure 6B is similar to Fig. 6A , but for ease of illustration, diffusion barrier layer 140 is not shown, and an embodiment is shown in which rear edge 193 of plasmon recess 195 has a cross-track width W2 that is less than W1, which can further increase the magnetic field strength. If desired, W2 can also be greater than W1.

[0041] Figure 6C is similar to Fig. 6A 1, but for ease of illustration, diffusion barrier layer 140 is not shown, and plasmon recess 195 is shown with flared cross-track side 195b, which causes the cross-track width to increase with distance from GBS. By increasing the cross-track width with distance from GBS, the heat shunt ( Figure 5A The heat of 190) to the heat sink material 92 is increased, and the temperature of the NFT can be reduced. Figure 6C As shown, the shape of the open side 195b can be a continuous curve. Alternatively, the shape of the open side 195b can be a series of straight lines or a straight line followed by a curve. The shape of the open plasmon recess can also be selected to match the shape of the NFT 74 ( Figure 5A ).

[0042] Fig. 7A is similar to Figure 5D GBS view of FIG. 1 and shows an embodiment where the cross-track width of the recess, and therefore the plasmon tip 195a, increases in the along-track direction (Z-axis) away from the NFT output tip 80, as shown by D being greater than W1. By gradually increasing the cross-track width in this direction, computer modeling shows that the thermal gradient can be increased. The plasmon recess can also be shaped in this direction so that D is less than W1.

[0043] Figure 7B is similar to Figure 5D GBS view of FIG. 1 , and shows an embodiment in which the plasmon recess may have a different shape in the along-track direction (Z-axis) away from the NFT output tip 80, such as a circular shape of the plasmon tip 195a. Figure 7B Also shown is an optional dielectric material layer 160, such as SiO2, that may be present between the plasmon material and the diffusion layer 140. The dielectric layer 160 reduces the amount of heat from the NFT output tip 80 to the main pole, which will reduce the likelihood of oxidation of the main pole.

[0044] Figure 7C is similar to Figure 5D GBS view of FIG. 1 and showing an embodiment in which a gap material 85 between a plasmon tip 195 a and an NFT output tip 80 is formed of a material different from the cladding material 77. The gap material 85 is shown as having a cross-track width substantially the same as the cross-track width of the narrowest portion of the NFT output tip 80, but it may have a cross-track width greater than the cross-track width of the gap or plasmon tip 195 a. Materials that can be used for the gap material 85 include TiO2, Ta2O5, Al2O3, Y2O3, MgF2, MgO, SiN, SiC, and AlN. Lower refractive index materials such as MgF2 can improve optical efficiency and reduce laser power and NFT temperature. Higher refractive index materials such as TiO2 or Ta2O5 can reduce the reflectivity of the NFT, which can reduce mode hopping of the laser. Materials with higher thermal conductivity such as AlN can reduce NFT temperature.

[0045] like Figure 8 As shown, the plasmon recess 195 may also be formed with different thicknesses along the track direction (Z axis). Figure 8 In the embodiment, the thickness gradually increases and is basically a linear change from T2 at the rear edge 193 to T1 at the GBS. Plasmon concave portions with different thicknesses can be designed so that T1 is greater or less than T2. ​​By changing the thickness at the rear edge or GBS, the magnetic field strength at the recording point can be adjusted.

[0046] Although the present invention has been specifically shown and described with reference to preferred embodiments, it will be appreciated by those skilled in the art that various changes may be made in form and detail without departing from the spirit and scope of the present invention. Therefore, the present invention disclosed is considered to be illustrative only and is limited in scope to the scope specified in the appended claims.

Claims

1. A heat-assisted magnetic recording (HAMR) head for writing to a magnetic recording layer, the HAMR head comprising: a head carrier having a surface facing the recording layer, an along-track axis, and a cross-track axis substantially orthogonal to the along-track axis; a near field transducer (NFT) layer located on the head carrier, the NFT layer located on a surface substantially normal to the recording layer facing surface and having an NFT tip located substantially at the recording layer facing surface having a cross-track width; a main pole located on the head carrier, the main pole having a recording layer facing surface with an output end and an NFT facing surface substantially orthogonal to the recording layer facing surface and having a height from the recording layer facing surface, the NFT facing surface having a recess containing a plasmon material, the plasmon material including a plasmon tip at the main pole output end, the plasmon tip being aligned with the NFT tip in the along-track direction and having a cross-track width equal to or less than the cross-track width of the NFT tip; and An optical waveguide is located on the head carrier and optically coupled to the NFT layer. 2 . The HAMR head according to claim 1 , wherein a height of the plasmon recess in a direction orthogonal to the recording layer-facing surface is substantially equal to or smaller than a height of the NFT-facing surface. 3 . The HAMR head of claim 2 , wherein a cross-track width of the plasmon recess is substantially constant along its height. 4 . The HAMR head of claim 1 , wherein the cross-track width of the plasmon recess in a region away from the plasmon tip is smaller than or larger than the cross-track width of the plasmon tip.

5. The HAMR head of claim 1 , wherein the cross-track width of the plasmon recess in a region away from the plasmon tip is greater than the cross-track width of the plasmon tip, and flares from the plasmon tip to the region away from the plasmon tip. 6 . The HAMR head of claim 1 , wherein the cross-track width of the plasmon tip increases or decreases from a region close to the NFT tip to a region far from the NFT tip in the along-track direction.

7. The HAMR head of claim 1, wherein the plasmonic material comprises one or more of Au, Rh, Ir, Cu, Ag, Al, Ru, Cr, Pt, Ti, Fe, Co, Ni, Pd, Be, Mo, W, AlN alloy, and TiN alloy. 8 . The HAMR head of claim 1 , further comprising a diffusion barrier layer between the main pole and the plasmon material in the recess. 9 . The HAMR head of claim 1 , further comprising a dielectric material layer between the main pole and the plasmon material in the recess.

10. The HAMR head of claim 1, further comprising a gap material layer between the plasmon tip and the NFT, the gap material being selected from the group consisting of TiO2, Ta2O5, Al2O3, Y2O3, MgF2, MgO, SiN, SiC, and AlN.

11. The HAMR head of claim 1 , further comprising a heat shunt interposed between the NFT layer and a surface of the main pole facing the NFT, wherein the heat shunt is in contact with the plasmonic material.

12. The HAMR head of claim 10, wherein the heat shunt is formed of the same material as the plasmonic material.

13. A heat assisted recording (HAMR) disk drive, the HAMR disk drive include: The HAMR head of claim 1, further comprising a magnetoresistive read head on the head carrier; a laser for directing light into the waveguide; and A magnetic recording disk having a magnetic recording layer.

14. A heat-assisted magnetic recording (HAMR) head for writing to a magnetic recording layer, the HAMR head comprising: a gas bearing slider having a gas bearing surface (GBS), an along-track axis, and a cross-track axis substantially orthogonal to the along-track axis; a near field transducer (NFT) layer on the slider, the NFT layer being located on a surface substantially normal to the GBS and having an output tip substantially located at the GBS; a main pole on the slider, the main pole having an NFT-facing surface substantially parallel to the NFT layer and an output end at the GBS aligned with the NFT output tip in the along-track direction, the NFT-facing surface having a recess containing a plasmonic material, the plasmonic recess having a leading edge at the GBS and a trailing edge away from the GBS, wherein the plasmonic recess leading edge has a cross-track width equal to or less than the cross-track width of the NFT output tip; a heat shunt interposed between the NFT layer and the NFT-facing surface of the main pole, wherein the heat shunt contacts a rear portion of the plasmon recess near the rear edge; and An optical waveguide is located on the slider and optically coupled to the NFT layer. 15 . The HAMR head of claim 14 , wherein a height of the plasmon recess from the front edge to the rear edge is substantially equal to or less than a height of the NFT-facing surface.

16. The HAMR head of claim 14, wherein the cross-track width of the plasmon recess is substantially constant along its height from the leading edge to the trailing edge.

17. The HAMR head of claim 14, wherein the cross-track width of the plasmon material in a region away from a front edge of the plasmon recess is smaller than or larger than the cross-track width of the front edge of the plasmon recess.

18. The HAMR head of claim 14, wherein the cross-track width of the plasmon recess in a region away from a front edge of the plasmon recess is greater than the cross-track width of the front edge, and flares from the front edge to the region away from the front edge. 19 . The HAMR head of claim 14 , wherein the cross-track width of the front edge of the plasmon recess increases or decreases from a region close to the NFT tip to a region far from the NFT tip in the along-track direction.

20. The HAMR head of claim 14, wherein the along-track thickness of the plasmon recess in a region away from a front edge of the plasmon recess is less than or greater than the along-track thickness of a front edge of the plasmon recess.

21. The HAMR head of claim 14, wherein the plasmonic material comprises one or more of Au, Rh, Ir, Cu, Ag, Al, Ru, Cr, Pt, Ti, Fe, Co, Ni, Pd, Be, Mo, W, AlN alloy, and TiN alloy.

22. The HAMR head of claim 14, further comprising a diffusion barrier layer between the main pole and the plasmon material in the recess.

23. The HAMR head of claim 14, further comprising a layer of dielectric material between the main pole and the plasmon material in the recess.

24. The HAMR head of claim 14, further comprising a gap material layer between the plasmon tip and the NFT, the gap material being selected from the group consisting of TiO2, Ta2O5, A12O3, Y2O3, MgF2, MgO, SiN, SiC, and AlN.

25. The HAMR head of claim 14, wherein the thermal shunt is formed of the same material as the plasmonic material.

26. A heat assisted recording (HAMR) disk drive, the HAMR disk drive comprising: The HAMR head of claim 14, further comprising a magnetoresistive read head on the head carrier; a laser for directing light into the waveguide; and A magnetic recording disk having a magnetic recording layer.

Images