Heat assisted magnetic recording (HAMR) head with main pole with narrow pole tip and plasma layer

Abstract

A heat assisted magnetic recording (HAMR) head has a slider having a gas bearing surface (GBS). The slider supports a near field transducer (NFT) having an output tip at the GBS and a main pole having a pole tip at the GBS. The pole tip has a narrow cross-track width that may be substantially the same as the cross-track width of the NFT output tip. A plasmon layer is positioned between the main pole and the NFT and has a tip at the GBS between the main pole tip and the NFT output tip. The plasmon layer may also be positioned on the cross-track side of the main pole and the main pole tip.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of the entire contents of U.S. non-provisional application No. 18 / 322,171, filed on May 23, 2023, entitled "HEAT-ASSISTED MAGNETIC RECORDING (HAMR) HEAD WITH MAINPOLE HAVING NARROW POLE TIP WITH PLASMONIC LAYER" and is hereby incorporated by reference for all purposes, which U.S. non-provisional application claims the benefit of U.S. Provisional Patent Application No. 63 / 425,262, filed on November 14, 2022. Background Art 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.

[0004] Description of Related Art

[0005] 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."

[0006] 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 (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 transfer from the light spot to a heat sink material located on the cross-track side of the main pole.

[0007] 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 apex of the output tip. Summary of the invention

[0008] 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 layer of plasmonic material on the main pole and facing the NFT to increase the thermal gradient, as described in US 10,121,496 B1. However, adding a plasmonic layer may increase the temperature of the NFT to unacceptable levels. Another problem in HAMR is adjacent track interference, that is, writing on a track adjacent to the track intended to be written.

[0009] In an embodiment of the present invention, the cross-track width of the main pole tip located at the GBS is very narrow and can be substantially the same as the cross-track width of the NFT output tip. This narrow main pole tip greatly reduces the possibility of interference between adjacent tracks. An embodiment of the present invention also includes a plasmon layer having a tip located at the GBS between the main pole tip and the NFT output tip, the tip having a narrow cross-track width. When a plasmon material is added between the main pole tip and the NFT output tip and the direction of light polarization is in the along-track direction, an image charge is induced in the plasmon material, thereby generating a local optical near field between the main pole tip and the NFT output tip due to the interaction between the charge at the top of the NFT and the image charge. 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 narrow plasmon tip heats the NFT output tip less than the wider plasmon tip.

[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] Thus, a detailed understanding of the manner in which the above-described features of the present disclosure are understood, a more particular description of the present disclosure, the above brief overview, may be obtained by reference to the embodiments, some of which are illustrated in the accompanying drawings. It should be noted, however, that the drawings illustrate only typical embodiments of the present disclosure and are therefore not to be considered limiting of its scope, as the present disclosure may admit to other equally effective embodiments.

[0012] Figure 1 is a top view of a heat-assisted magnetic recording (HAMR) disk drive according to an embodiment of the present invention.

[0013] Figure 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 showing very small features.

[0014] Figure 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 the recording layers on a disk.

[0015] Figure 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.

[0016] Figure 4A is a view from the gas bearing surface (GBS) of the HAMR head, and Figure 4B yes Figure 4A A view of section BB is shown to illustrate the full film layer of plasmonic material.

[0017] Figure 5A is a cross-sectional view of a HAMR head according to an embodiment of the present invention, and Figure 5B and Figure 5C They are Figure 5A View of sections BB and CC.

[0018] Figure 5D is for an implementation scheme similar to Figure 5B and 5C , in this embodiment, the cross-track width of the plasmon layer is narrower than the cross-track width of the main pole in the direction recessed from the GBS.

[0019] Figure 5E is for an implementation scheme similar to Figure 5B and 5C , in which the cross-track width of the plasmon layer is wider than the cross-track width of the main pole in the direction recessed from the GBS.

[0020] Fig. 5F is a cross-sectional view of an embodiment, and Figure 5G yes Fig. 5F A view of section GG where the heat shunt extends to the plasmon layer and the plasmon layer is truncated in a direction concave from the GBS.

[0021] Fig. 6A is a cross-sectional view of a HAMR head according to another embodiment of the present invention, and Figure 6B yes Fig. 6A A view of a cross section BB.

[0022] Fig. 7A is a cross-sectional view of a HAMR head according to still another embodiment of the present invention, and Figure 7B yes Fig. 7A A view of a cross section BB.

[0023] Figure 8 is similar to Figure 5A GBS view of FIG. 1 , and shows an embodiment in which the gap material between the plasmon tip and the NFT output tip is formed of a material different from the cladding material.

[0024] To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one embodiment may be beneficially utilized on other embodiments without specific recitation. DETAILED DESCRIPTION

[0025] Hereinafter, reference is made to the embodiments of the present disclosure. However, it should be understood that the present disclosure is not limited to the embodiments specifically described. On the contrary, any combination of the following features and elements (whether or not related to different embodiments) is considered to realize and practice the present disclosure. In addition, although the embodiments of the present disclosure can achieve advantages that are superior to other possible solutions and / or superior to the prior art, whether a specific advantage is achieved by a given embodiment is not a limitation to the present disclosure. Therefore, the following aspects, features, embodiments and advantages are merely illustrative, and are not considered to be elements or limitations of the appended claims, unless explicitly stated in the claims. Similarly, reference to "the present disclosure" should not be interpreted as a summary of any inventive subject matter disclosed herein, and should not be considered to be elements or limitations of the appended claims, unless explicitly stated in the claims.

[0026] 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 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.

[0027] 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 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.

[0028] In the following drawings, the X-axis represents the axis perpendicular to the gas bearing surface (GBS) of the slider, the Y-axis represents the track width or the cross-track axis, and the Z-axis represents the along-track axis. Figure 2 is a schematic cross-sectional view showing a configuration example of a HAMR head according to the prior art. Figure 2 , a 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. A gas bearing slider 120 is supported by a suspension 135 and has a GBS facing the 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 the 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 through the primary pole 53 to the main pole 52 disposed near an optical near field transducer (NFT) 74. Figure 2A write head 50 is shown with a known "flat" coil 56, where the coil segments lie in substantially the same plane. Alternatively, however, the coil may be a known "spiral" coil, where the coil is wound around a 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 a recording magnetic field generated by the main pole 52.

[0029] 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 SiO x N y Alternatively, SiO2 can be used as a cladding material, and Ta2O5, TiO2, Nb2O5, SiO x N 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.

[0030] Figure 3A1 is a side cross-sectional view of a prior art HAMR head, and shows the material layers constituting the primary pole 53, the main pole 52, the NFT 74 and the waveguide 73, and is shown relative to the disk 150 having the recording layer 31. The main pole 52 is typically a layer of high magnetic moment material (such as FeCo), and has an output end 52a located at the GBS and a surface 52b facing the NFT 74. The waveguide 73 is a core material layer generally parallel to the main pole 52 layer, with a length orthogonal to the GBS, and a waveguide end 73d 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 can also be Ag, Al, Cu, Rh, Ir or alloys thereof), 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 located 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 output end 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 output end 52a at the GBS. The main pole output end 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.

[0031] Figure 3Bis a perspective view of a prior art HAMR head, and shows a heat sink material 92 in contact with a heat shunt 90, as well as a main pole 53, a main pole 52, an NFT output tip 80, and a 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.

[0032] The 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. 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 confined heat source in the recording layer. Au, Ag, and Cu are examples of plasmonic materials.

[0033] Figure 4A is the view from the GBS of the HAMR head, and Figure 4B BB is a view of section BB for illustrating the full film layer of plasmon material. The full film plasmon layer 95 is positioned on the NFT-facing surface 52b of the main pole 52 and extends from the front edge 95a at the GBS to the rear edge 95b recessed from the GBS. Figure 4B As shown in FIG. 1 , because the plasmon layer is a full film that substantially covers the surface of the main pole 52 facing the NFT, the cross-track width (Y direction) of the plasmon layer 95 is substantially the same as the cross-track width W of the main pole 52 at the GBS. MP The main electrode has a height H MP (in the X direction) and plasmon layer 95 has height H1.

[0034] In an embodiment of the present invention, the cross-track width of the main pole tip located at the GBS is very narrow and can be substantially the same as the cross-track width of the NFT output tip. This narrow main pole tip greatly reduces the possibility of adjacent track interference, that is, writing on a track adjacent to the track intended to be written. The plasmon layer has a tip located between the main pole tip and the NFT output tip at the GBS. When a plasmon material is added between the NFT output tip and the main pole tip and the direction of light polarization is in the along-track direction (Z direction), an image charge is induced in the plasmon material, thereby generating a local optical near field between the NFT output tip and the main pole tip due to the interaction between the charge at the top of the NFT and the image charge. 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 cross-track width of the plasmon tip at the GBS can be substantially equal to, greater than, or less than the cross-track width of the widest part of the NFT output tip at the GBS. A narrow plasmon tip heats the NFT output tip less than a wider plasmon tip.

[0035] Figure 5A is a cross-sectional view of a HAMR head according to an embodiment of the present invention, and Figure 5B and Figure 5C These are views of sections BB and CC respectively. Figure 5A is a view from the GBS and shows the NFT output tip 80, the waveguide core end 73d and the surrounding cladding material 77. Figure 5A As shown, the main pole output end 152a at the GBS has a tip 152c facing the NFT 80 and aligned with it in the along-track direction (Z direction). The plasmon material having a tip 195a located at the GBS is positioned on the main pole 152 and the main pole tip 152c and between the main pole tip 152c and the NFT 80. In this embodiment, the cross-track width W1 of the plasmon tip 195a at the GBS and the width W1 of the main pole tip 152c are equal to the width W2 of the main pole tip 152c. PT are substantially equal to or less than the widest width W of the NFT output tip 80 at the GBS NFT The cross-track width. W NFT is the width at the portion farthest from plasmon tip 195a in the Z direction, and W TOP W is the narrowest width and is closest to plasmon tip 195a in the Z direction. NFT Typically in the range of 50nm to 150nm. 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 was determined to have a typical width between about 20nm-40nm.

[0036] Figure 5B yes Figure 5A BB and shows the shape of the main pole 152 having a pointed end 152c. Figure 5C yes Figure 5A and shows a cross section CC located at the main pole 152 and the tip 152c (which is positioned behind the plasmon layer 195 in the Z direction and is therefore not in Figure 5C In this embodiment, the plasmon layer 195 having a tip 195a located at the GBS and a rear edge 195b recessed from the GBS covers the entire main pole 152 and the tip 152c, and thus has substantially the same shape as the main pole 152 and the tip 152c. The main pole 152 has a height H MP (in the X direction)( Figure 5B ) and the plasmon layer 95 has a height H1 ( Figure 5C ). H1 can be equal to or less than H MP If H1 is smaller than H MP , then part of the main pole is directly aligned with the NFT layer in the Z direction, which increases the magnetic field strength at the recording layer. Figure 5C As shown, in the region away from the plasmon tip 195a, the cross-track width of the plasmon layer 195 in the direction orthogonal to the GBS (X direction) is greater than the cross-track width of the plasmon tip 195a. Figure 5A and 5B As shown, if the plasmon layer 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 cladding material 77 and between the heat sink material 92 and the plasmon layer 195.

[0037] As shown by the shape of the main electrode 152 ( Figure 5B ) and the shape of the plasmon layer 195 ( Figure 5C ), the plasmon layer 195 is located on the entire main pole 152, and they have substantially the same shape. However, in the direction concave from the GBS (X direction), the cross-track width of the plasmon layer can be narrower than the cross-track width of the main pole 152 (as shown in FIG. Figure 5D ) or width (as shown in the plasmon layer 295 in Figure 5E 395 in the plasmon layer).

[0038] The plasmon layer may extend to a thermal shunt. A thermal shunt is a high thermal conductivity material (such as Au, Ag, or Cu) positioned between the NFT and the main pole to allow heat to transfer from the optical point to a heat sink material positioned on the cross-track side of the main pole. Figure 3AThe heat shunt 90 between the NFT 74 and the main pole 52 is shown in FIG. In one embodiment of the present invention, as Fig. 5F The cross-sectional view and Figure 5G As shown in the cross-sectional view of , heat shunt 190 extends to plasmon layer 495 and plasmon layer 495 is truncated in the X direction, where it is connected to heat shunt 190 at its rear edge 495 b.

[0039] Fig. 6A is a cross-sectional view of a HAMR head according to another embodiment of the present invention, and Figure 6B is a view of section BB. In this embodiment, heat sink material 92 is also positioned on both cross-track sides of main pole 152 .

[0040] Fig. 7A is a cross-sectional view of a HAMR head according to still another embodiment of the present invention, and Figure 7B BB is a view of section BB. In this embodiment, plasmon layer 195 has plasmon tip 195a located between main pole tip 152c and NFT 80, and side portion 195c located on the cross-track side of main pole 152 and pole tip 152c. In this embodiment, the cross-track width W1 of plasmon tip 195a may be greater than the cross-track width W1 of NFT 80. NFT .

[0041] The plasmon layer 195 may be formed of 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.

[0042] Figure 8 is similar to Figure 5A 1 and 10 are GBS views of the NFT output tip 80 and illustrate an embodiment in which gap material 85 between plasmon tip 195a and NFT output tip 80 is formed of a different material than cladding material 77. Gap material 85 is shown to have a cross-track width (W) of the narrowest portion of NFT output tip 80. TOP ) substantially the same cross-track width as the plasmon tip 195a, but its cross-track width can be greater than the cross-track width of the plasmon tip 195a. Materials that can be used for 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.

[0043] 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 on the head carrier, the NFT layer being located on a surface substantially normal to the recording layer facing surface and having an NFT output tip having a cross-track width located substantially at the recording layer facing surface; a main pole located on the head carrier, the main pole facing the NFT layer and having a pole tip, the pole tip being located substantially at the recording layer facing surface and aligned with the NFT output tip in a along-track direction, the cross-track width of the pole tip being substantially equal to or less than the cross-track width of the NFT output tip; a layer of plasmon material located on the main pole between the main pole and the NFT layer, the plasmon layer including a plasmon tip located on the pole tip and aligned with the NFT output tip in the along-track direction; 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 layer in a direction orthogonal to the surface facing the recording layer is substantially equal to or smaller than a height of the main pole in a direction orthogonal to the surface facing the recording layer. 3 . The HAMR head of claim 1 , wherein a cross-track width of the plasmon layer in a direction orthogonal to the surface facing the recording layer in a region away from the plasmon tip is greater than a cross-track width of the plasmon tip. The HAMR head according to claim 1 , wherein the plasmon layer is located on the entire main pole. 5 . The HAMR head of claim 1 , wherein the plasmon layer is located on a cross-track side of the main pole and a cross-track side of the pole tip. 6 . The HAMR head according to claim 1 , wherein a cross-track width of the plasmon layer is smaller than a cross-track width of the main pole in a region recessed from the recording layer-facing surface. 7 . The HAMR head according to claim 1 , wherein a cross-track width of the plasmon layer is larger than a cross-track width of the main pole in a region recessed from the recording layer-facing surface.

8. The HAMR head of claim 1, further comprising a heat shunt in contact with the plasmon layer. 9 . The HAMR head of claim 8 , wherein the plasmon layer has a rear edge that is recessed from the recording layer-facing surface and is in contact with the heat shunt.

10. 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. 11 . The HAMR head of claim 1 , further comprising a diffusion barrier layer between the main pole and the plasmon layer.

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

13. The HAMR head of claim 1 further comprising a heat sink material on a cross-track side of the main pole.

14. The HAMR head of claim 13, wherein the heat sink material is positioned on a cross-track side of the main pole tip at the recording layer-facing surface.

15. 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.

16. 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 having a cross-track width located substantially at the GBS; a main pole on the slider, the main pole facing the NFT layer and having a pole tip, the pole tip being substantially located at the GBS and aligned with the NFT output tip in a along-track direction, the cross-track width of the pole tip being substantially equal to or less than the cross-track width of the NFT output tip; a plasmon material layer on the main pole, the plasmon material layer being interposed between the main pole and the NFT layer and being located on the cross-track side of the main pole and the cross-track side of the pole tip, the plasmon layer including a plasmon tip, the plasmon tip being located on the pole tip and aligned with the NFT output tip in the along-track direction; and An optical waveguide is located on the head carrier and optically coupled to the NFT layer. 17 . The HAMR head of claim 16 , wherein a height of the plasmon layer in a direction orthogonal to the GBS is substantially equal to or smaller than a height of the main pole in the direction orthogonal to the GBS. 18 . The HAMR head of claim 16 , wherein a cross-track width of the plasmon layer in a direction orthogonal to the GBS in a region away from the plasmon tip is greater than a cross-track width of the plasmon tip. 19 . The HAMR head of claim 16 , wherein a cross-track width of the plasmon layer in a region recessed from the GBS is smaller than or larger than a cross-track width of the main pole in a region recessed from the GBS.

20. The HAMR head of claim 16, further comprising a thermal shunt between the NFT and the main pole, and wherein the plasmon layer has a rear edge that is recessed from the GBS and in contact with the thermal shunt.

21. The HAMR head of claim 16, 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 16, further comprising a diffusion barrier layer between the main pole and the plasmon layer.

23. The HAMR head of claim 16, further comprising a gap material layer between the plasmon tip and the NFT output tip, the gap material being selected from the group consisting of TiO2, Ta2O5, Al2O3, Y2O3, MgF2, MgO, SiN, SiC, and AlN.

24. A heat assisted recording (HAMR) disk drive, the HAMR disk drive comprising: The HAMR head of claim 16, further comprising a magnetoresistive read head on the slider; a laser for directing light into the waveguide; and A magnetic recording disk having a magnetic recording layer.

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