Thermally assisted magnetic write head employing a near field transducer (NFT) having a diffusion barrier layer between the near field transducer and a magnetic lip

A thermally assisted magnetic write head having a near-field transducer, a magnetic lip and a diffusion barrier layer between the near-field transducer and the magnetic lip. The near-field transducer includes a transparent aperture constructed of a material such as SiO2 and an opaque metallic antenna constructed of a metal such as Au formed at a first edge of the aperture. A magnetic lip, connected with the write pole is formed near a second edge of the aperture with a diffusion barrier layer being disposed between the magnetic lip and the aperture. The diffusion barrier layer prevents migration of atomic between the aperture and the magnetic lip, thereby ensuring robust performance at localized high temperatures generated by the near-field transducer.

FIELD OF THE INVENTION

The present invention relates to heat assisted magnetic recording, and more particularly to a magnetic write head having a near field transducer placed proximate to the magnetic write pole lip. The magnetic write pole lip is separated from the near-field transducer by a diffusion barrier layer to prevent atomic diffusion between the magnetic lip and the aperture material.

BACKGROUND OF THE INVENTION

The heart of a computer's long term memory is an assembly that is referred to as a magnetic disk drive. The magnetic disk drive includes a rotating magnetic disk, write and read heads that are suspended by a suspension arm adjacent to a surface of the rotating magnetic disk and an actuator that swings the suspension arm to place the read and write heads over selected circular tracks on the rotating disk. The read and write heads are directly located on a slider that has an air bearing surface (ABS). The suspension arm biases the slider toward the surface of the disk, and when the disk rotates, air adjacent to the disk moves along with the surface of the disk. The slider flies over the surface of the disk on a cushion of this moving air. When the slider rides on the air bearing, the write and read heads are employed for writing magnetic transitions to and reading magnetic transitions from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions.

Magnetoresistive sensors such as GMR or TMR sensors are employed for sensing magnetic fields from the rotating magnetic disk. The sensor includes a nonmagnetic conductive layer, or barrier layer, sandwiched between first and second ferromagnetic layers, referred to as a pinned layer and a free layer. First and second leads are connected to the sensor for conducting a sense current there-through. The magnetization of the pinned layer is pinned perpendicular to the air bearing surface (ABS) and the magnetic moment of the free layer is located parallel to the ABS, but free to rotate in response to external magnetic fields. The magnetization of the pinned layer is typically pinned by exchange coupling with an antiferromagnetic layer.

The thickness of the spacer layer is chosen to be less than the mean free path of conduction electrons through the sensor. With this arrangement, a portion of the conduction electrons is scattered by the interfaces of the spacer layer with each of the pinned and free layers. When the magnetizations of the pinned and free layers are parallel with respect to one another, scattering is minimal and when the magnetizations of the pinned and free layer are antiparallel, scattering is maximized. Changes in scattering alter the resistance of the spin valve sensor in proportion to cos θ, where θ is the angle between the magnetizations of the pinned and free layers. In a read mode the resistance of the spin valve sensor changes proportionally to the magnitudes of the magnetic fields from the rotating disk. When a sense current is conducted through the spin valve sensor, resistance changes cause potential changes that are detected and processed as playback signals.

The write head can be a perpendicular magnetic recording head that records data as magnetizations oriented perpendicular to the plane of the magnetic disk. The magnetic disk has a magnetically soft underlayer covered by a thin magnetically hard top layer. The perpendicular write head has a write pole with a very small cross section and a return pole having a much larger cross section. A strong, highly concentrated magnetic field emits from the write pole in a direction perpendicular to the magnetic disk surface, magnetizing the magnetically hard top layer. The resulting magnetic flux then travels through the soft underlayer, returning to the return pole where it is sufficiently spread out and weak that it will not erase the signal recorded by the write pole when it passes back through the magnetically hard top layer on its way back to the return pole.

A heating element can be incorporated into the write head in order to allow a further decrease in bit size and therefore allow a corresponding increase in data density. In order to write ever smaller bits of data, the magnetic coercivity must be increased, in order to prevent the extremely small bit from becoming demagnetized after the data has been written. Locally heating the media during writing of data momentarily reduces the coercivity of the media allowing the data to be written to the high coercivity media.

SUMMARY OF THE INVENTION

The present invention provides a thermally assisted magnetic write head that includes a magnetic lip and a heating device. The heating device can include a near field transducer, such as a plasmonic antenna or a transparent aperture. A diffusion barrier layer is sandwiched between the near field transducer and the magnetic lip.

The heating device can be a plasmonic heating device that includes an opaque, metallic plasmonic antenna and an aperture adjacent to the plasmonic antenna. A magnetic lip structure can be disposed opposite the plasmonic antenna, such that the aperture is between the magnetic lip structure and the plasmonic antenna. A diffusion barrier layer can be sandwiched between the antenna/aperture and the magnetic lip structure.

The presence of the diffusion barrier layer between the aperture and the magnetic lip advantageously prevents the migration of atoms between the aperture and the magnetic lip during the high temperatures generated by the plasmonic heating device. This ensures robust operation and high performance of the write head in several ways. For example, preventing this interdiffusion avoids an unwanted increase in effective spacing between the writing edge of the magnetic lip and the antenna/aperture interface that generates the heat for the thermally assisted recording. In addition, preventing such interdiffusion ensures that the optical properties of the aperture are maintained.

These and other features and advantages of the invention will be apparent upon reading of the following detailed description of preferred embodiments taken in conjunction with the Figures in which like reference numerals indicate like elements throughout.

DETAILED DESCRIPTION OF THE EMBODIMENTS

During operation of the disk storage system, the rotation of the magnetic disk112generates an air bearing between the slider113and the disk surface122which exerts an upward force or lift on the slider. The air bearing thus counter-balances the slight spring force of suspension115and supports slider113off and slightly above the disk surface by a small, substantially constant spacing during normal operation.

With reference toFIG. 2, the orientation of the magnetic head121in a slider113can be seen in more detail.FIG. 2is an ABS view of the slider113, and as can be seen the magnetic head including an inductive write head and a read sensor, is located at a trailing edge of the slider. The above description of a typical magnetic disk storage system, and the accompanying illustration ofFIG. 1are for representation purposes only. It should be apparent that disk storage systems may contain a large number of disks and actuators, and each actuator may support a number of sliders.

With reference now toFIG. 3, a write head300is described, which may be incorporated into a magnetic head such as head121shown inFIG. 2. The write head300can include a write pole302that extends to an air bearing surface (ABS) and a magnetic return pole304. The return pole304has a cross section at the ABS that is larger than the cross section of the write pole302at the ABS. The write pole302can be connected with a shaping layer306in a region removed from the ABS. A magnetic back gap layer308connects the shaping layer306with the return pole304in a region removed from the ABS, thereby magnetically connecting the write pole302with the return pole304in a region removed from the ABS. The write pole302, return pole304, shaping layer306and back gap308are all constructed of a magnetic material such as NiFe or CoFe. The write pole302is also constructed of a magnetic material and is preferably constructed of a lamination of layers of high magnetic moment material such as CoFe separated by thin layers of non-magnetic material.

An electrically conductive write coil310, shown in cross section inFIG. 3, passes between the write pole302and the return pole304and may also pass beneath the write pole302. The write coil310can be constructed of a non-magnetic, electrically conductive material such as Cu and can be embedded in a non-magnetic, electrically insulating material such as alumina312.

With continued reference toFIG. 3, a heating device314can be provided adjacent to the write pole302for locally heating the magnetic media112. The heating device314can pass through an opening within the back gap layer308so that it can extend beyond the back gap layer308. The magnetic media112travels in a direction indicated by arrow316relative to the write head302. Therefore, as can be seen, the heating device314is upstream from the write pole302, or in other words is in a leading direction relative to the write pole302. The heating device314locally heats the magnetic media112in a region just upstream from the write pole302, which momentarily reduces the coercivity of the magnetic media. This greatly facilitates writing to a magnetic media which has an otherwise too high coercivity to be written to. In order for the heating device314to effectively function, it must be located as close as possible to the write pole. In addition, the heating device314must heat only a very small area on the media112in order to avoid demagnetizing adjacent tracks of data or downstream data on the same track.

One example of a heating element that is particularly suited to use as a heating device in a magnetic recording system is a plasmonic heating device.FIG. 4shows an enlarged view of a portion of a plasmonic heating device314, as seen from circle4ofFIG. 3.FIG. 5shows an ABS view of the structure shown inFIG. 4, as seen from line5-5ofFIG. 4. With reference toFIG. 4, the plasmonic heating device314includes a light waveguide402, which can be constructed of an oxide such as Tantalum oxide (Ta2O5), titanium oxide (TiO2), niobium oxide (Nb2O5), zirconium oxide (ZrO2), lanthanum oxide (La2O3), Yttrium oxide (Y2O3), scandium oxide (Sc2O3) or a binary, ternary or quaternary combination of these oxides. The wave guide402can also be constructed of oxynitrides such as silicon oxynitride (SiOxNy), tantalum oxynitride (TaOxNy), titanium oxynitride (TiOxNy) and zirconium oxynitride (ZrOxNy).

The waveguide402is surrounded by a cladding material404, which can be a material such as alumina. The plasmonic heating device314also includes an opaque metal antenna406located at the ABS. A magnetic, metallic lip408may extend from the write pole302toward an aperture410formed between the magnetic lip408and the antenna406.

The antenna406, magnetic lip408and aperture410can be seen more clearly with reference toFIG. 5, which shows an ABS view of the structure as seen from line5-5ofFIG. 4. Side portions412, at either side of the magnetic lip408can be constructed of cladding material similar to or the same as the cladding material404. Alternatively, antenna406can extend up the sides of the lip408so that the side portions412are constructed of the same material as the antenna406.

With continued reference toFIG. 5, a plasmonic antenna406is formed adjacent to the aperture410, forming an interface504there-between. The plasmonic antenna406can be constructed of a metallic material such as Au, Ag, Cu or Rh. The magnetic lip408is magnetically connected with the write pole302and functions magnetically as a part of the write pole302. The magnetic lip408is constructed of a magnetic metal such as a binary or ternary compound containing Co, Fe, Cr and or Ni (e.g. CoFe, CoFeCr, CoFeNi), and the leading most edge506functions as the writing edge of the lip408. The aperture410is constructed of a low refractive index dielectric material such as SiOx, SiOxNy, Al2O3or some other similar dielectric having a refractive index less than 1.75.

When light travels through the wave guide402(FIG. 4), a plasmonic wave is formed at the junction504between the antenna406and the aperture410. The junction504between the antenna406and the aperture410is formed with a notch508. This notch508is designed to form nodes in the plasmonic wave at desired locations.

Laser light is incident on the waveguide cross-section at the flex side of the slider and the light is carried and delivered by the waveguide402at the “E” shaped plasmonic antenna406. The light impinging at the metal-dielectric interface504has its polarization parallel to the notch and thus creates a resonant plasmonic wave. The broad “wing” regions of the “E” shaped antenna406act as charge reservoirs and hence, set up the boundary condition. The space charge concentration is increased at the sub-100 nm dimension notch508of the antenna406as compared to the rest of the antenna due to a “lightning rod” effect. This concentration of light energy at sub-wavelength dimensions leads to generation of a hot spot at the notch508. This hot spot is used to locally heat the magnetic medium112(FIG. 3) to temporarily lower the magnetic coercivity at that location. The hot spot heats the media112in an extremely focused and small area of the media, smaller and more focused than would be possible using any other heating method.

This concentration of light energy at the plasmonic antenna leads to heating up of the plasmonic antenna406, the aperture410and the magnetic lip408. In absence of the present invention, this extreme heating would cause inter-diffusion between the SiO2aperture410and the magnetic lip408. This inter-diffusion would cause degradation in the performance of the write head300. For example, the spacing between interface504of the plasmonic device and the edge506of the magnetic lip408would increase due to compromised magnetic properties of the leading edge of the magnetic lip. This would therefore lead to an increase in the distance between the magnetic writing and the heat source. Also, the optical properties of the SiO2would be changed due to the diffusion of metallic atomic into it.

The presence of a thin diffusion barrier layer502advantageously prevents this interdiffusion between the aperture material410and the lip material408without dramatically increasing the spacing between the magnetic lip and the plasmonic antenna notch. The desired characteristics of the diffusion barrier layer502is that it should have low oxygen diffusivity to prevent oxygen diffusion from the aperture410into the magnetic lip408while also preventing Co, Fe, Ni and/or Cr from migrating from the magnetic layer408into the aperture410. The diffusion barrier502should exhibit no chemical reactivity with Si, O, Co, Fe, Cr or Ni. It should also exhibit good adhesion with the SiO2of the aperture410and also with the magnetic material of the lip408even at elevated temperatures. It should also be thin enough that it does not significantly increase the spacing between the magnetic lip408and the antenna notch508.

With this in mind, the diffusion barrier layer502can be constructed as a TaN or Si3N4layer having a thickness of 5 nm or less. Alternatively, as shown in greater detail inFIG. 6the diffusion barrier layer502can be a Rh or Ru layer602with a thickness of 4 nm or less with an adhesion layer604having a thickness of 1 nm or less sandwiched between the Rh or Ru layer and the SiO2aperture410. The adhesion layer can be Ta, Cr or could be TaN. In another embodiment as shown inFIG. 7, the diffusion barrier layer502could be constructed with a layer of Rh or Ru702having a thickness of 3 nm or less sandwiched between first and second adhesion layers704,706each having a thickness of 1 nm or less. Again, the adhesion layers704,706could be Ta, Cr or could be TaN.

It should be pointed out that the above described plasmonic device separated from a magnetic lip with a diffusion barrier layer, discussed with reference toFIGS. 4 and 5are by way of example only, and the invention could be incorporated into many other configurations of devices. The NFT (antenna or aperture) is separated from the magnetic lip by the diffusion layer which is sandwiched therebetween. The NFT (whether antenna or aperture) can be of various configurations. For example, a device could be constructed having an antenna406adjacent to a magnetic lip408, with a diffusion barrier502, such as the ones discussed above, sandwiched between the antenna406and the magnetic lip408. In addition, the magnetic antenna406could have a shape other than that discussed above. For example, the antenna406could be a nano-beak design having a shape similar to a bird's beak, narrowing to a point at the air bearing surface.FIGS. 8 and 9illustrate another possible embodiment of the invention where the antenna is a nano-beak antenna. The nano-beak antenna is located within the cladding material404adjacent to and separated from the magnetic lip408by a diffusion barrier layer502, which may be constructed of a material or materials described above. The length of the nano-beak metal and the diffusion barrier layer, as measured from the ABS, is same as the length of the magnetic lip408as shown inFIG. 8. As can be seen, the antenna804has a tapered point at the ABS. The wave guide802can be separated from the upper return pole302by a non-magnetic spacer layer806. A top down view of the antenna is shown inFIG. 9, wherein it can be seen that the antenna804also narrows to a point at the ABS as viewed from the top down. Light traveling through the waveguide402is drawn to the antenna forming an extremely focused hot spot at the pointed tip of the antenna804. Again, heat from this hot stop could cause diffusion between the antenna804and the magnetic lip408. However, this diffusion is prevented by the presence of the diffusion barrier layer502there-between. Therefore, the presence of the diffusion barrier layer502provides the same advantage in this presently described embodiment as it did in the previously described embodiment.

Other antenna shapes include lollipop shape, a bow tie shape or a two-rod antenna. Similarly, the shape or configuration of the aperture410could vary as well. For example, the aperture could have a “C” shape, a triangular shape or could be configured as a ridge waveguide aperture. In addition, the NFT could be a Very Small Aperture Laser (VSAL).