Patent Application
20150248901
In heat assisted magnetic recording (HAMR), information bits are recorded on data storage media at elevated temperatures. The data bit dimension can be determined by the dimensions of the heated area in the storage medium or the dimensions of an area of the storage medium that is subjected to a magnetic field. In one approach, a beam of light is condensed to a small optical spot on the storage medium to heat a portion of the medium and reduce the magnetic coercivity of the heated portion. Data is then written to the reduced coercivity region.
Typically, the beam of light is focused or condensed to a small optical spot using a near field transducer (NFT). An exemplary type of a NFT is one that has a disc and a peg that focuses the light into the optical spot. Such NFTs are designed for use with visible light and are quite sensitive to variations in manufacturing. They also are typically made of noble metals, such as gold and as such are susceptible to metal reflow. Therefore, there remains a need for NFTs of different materials.
Disclosed is an apparatus that includes a near field transducer (NFT), the NFT including, amongst other elements and materials: tantalum (Ta), niobium (Nb), molybdenum (Mo), rhodium (Rh), ruthenium (Ru), osmium (Os), titanium (Ti), zirconium (Zr), yttrium (Y), hafnium (Hf), platinum (Pt), palladium (Pd), vanadium (V), chromium (Cr), iridium (Ir), scandium (Sc), niobium (Ni), cobalt (Co), rhenium (Re), silicon (Si), geranium (Ge), alloys thereof, dispersions containing these elements, intermetallics based on these elements, admixtures thereof, or combinations thereof.
Also disclosed is an apparatus that includes a light source configured to transmit energy at a wavelength of at least about 1300 nm; a waveguide; and a near field transducer (NFT), the NFT including tantalum (Ta), niobium (Nb), molybdenum (Mo), tungsten (W), palladium (Pd), osmium (Os), rhodium (Rh), alloys thereof, dispersions containing these elements, intermetallics based on these elements, admixtures thereof, or combinations thereof, wherein the light source, waveguide and NFT are configured to transmit light from the light source to the waveguide and finally to the NFT.
Also disclosed are methods that include providing energy from an energy source, the energy having a wavelength of at least about 1300 nm; transmitting the energy from the energy source to the receiving portion of a near field transducer (NFT), wherein the NFT includes tantalum (Ta), niobium (Nb), molybdenum (Mo), rhodium (Rh), ruthenium (Ru), osmium (Os), titanium (Ti), zirconium (Zr), yttrium (Y), hafnium (Hf), platinum (Pt), palladium (Pd), vanadium (V), chromium (Cr), iridium (Ir), scandium (Sc), niobium (Ni), cobalt (Co), rhenium (Re), silicon (Si), geranium (Ge), boron (B), carbon (C), alloys thereof, dispersions containing these elements, intermetallics based on these elements, admixtures thereof, or combinations thereof; and focusing the energy in the NFT to form an optical spot on an associated magnetic recording media.
The above summary of the present disclosure is not intended to describe each disclosed embodiment or every implementation of the present disclosure. The description that follows more particularly exemplifies illustrative embodiments. In several places throughout the application, guidance is provided through lists of examples, which examples can be used in various combinations. In each instance, the recited list serves only as a representative group and should not be interpreted as an exclusive list.
The figures are not necessarily to scale. Like numbers used in the figures refer to like components. However, it will be understood that the use of a number to refer to a component in a given figure is not intended to limit the component in another figure labeled with the same number.
It is thought, but not relied upon that because of the materials utilized in the NFTs of disclosed devices, they can be utilized at wavelengths other than visible light. As such geometrical constraints can be lessened, loss of light by the NFT material can be lessened which can allow for larger NFTs, and reflow of the NFT material can be limited or even eliminated.
Disclosed herein are NFTs and devices that include such NFTs.
For heat assisted magnetic recording (HAMR), electromagnetic radiation, for example, visible, infrared or ultraviolet light is directed onto a surface of the data storage media to raise the temperature of a localized area of the media to facilitate switching of the magnetization of the area. Recent designs of HAMR recording heads include a thin film waveguide on a slider to guide light toward the storage media and a near field transducer to focus the light to a spot size smaller than the diffraction limit. While
An insulating material 62 separates the coil turns. In one example, the substrate can be AlTiC, the core layer can be Ta2O5, and the cladding layers (and other insulating layers) can be Al2O3. A top layer of insulating material 63 can be formed on the top pole. A heat sink 64 is positioned adjacent to the sloped pole piece 58. The heat sink can be comprised of a non-magnetic material, such as for example Au.
As illustrated in
The storage media 16 is positioned adjacent to or under the recording head 30. The waveguide 42 conducts light from a source 78 of electromagnetic radiation, which may be, for example, ultraviolet, infrared, or visible light. The source may be, for example, a laser diode, or other suitable laser light source for directing a light beam 80 toward the waveguide 42. Specific exemplary types of light sources 78 can include, for example laser diodes, light emitting diodes (LEDs), edge emitting laser diodes (EELs), vertical cavity surface emitting lasers (VCSELs), and surface emitting diodes. In some embodiments, the light source can produce energy of a desired wavelength. Various techniques that are known for coupling the light beam 80 into the waveguide 42 may be used. Once the light beam 80 is coupled into the waveguide 42, the light propagates through the waveguide 42 toward a truncated end of the waveguide 42 that is formed adjacent the air bearing surface (ABS) of the recording head 30. Light exits the end of the waveguide and heats a portion of the media, as the media moves relative to the recording head as shown by arrow 82. A near-field transducer (NFT) 84 is positioned in or adjacent to the waveguide and at or near the air bearing surface. The heat sink material may be chosen such that it does not interfere with the resonance of the NFT.
Although the example of
In some embodiments, disclosed NFTs may include refractory metals, such as tantalum (Ta), niobium (Nb), molybdenum (Mo), tungsten (W), and rhenium (Re) for example, as well as titanium (Ti), zirconium (Zr), hafnium (Hf), vanadium (Va), chromium (Cr), ruthenium (Ru), osmium (Os), iridium (Ir), and rhodium (Rh).
Melting points of refractory metals can generally be above 2000 K, can sometimes be above 2500 K, and can even sometimes be above 3000° K; while that of gold (Au), for example, is about 1000 K. A failure mode of NFTs is high temperature related ductile flow and creep strain. Flow and creep properties in metals and alloys is a thermal activated phenomenon. Flow and creep properties are exponentially dependent (Arrhenius dependence) on the homologous temperature, (Th) where Th=Temperature/Tmelting. Thus, for the same operating temperature, higher melting materials have an exponentially better reliability than lower melting point materials. Diffusion activated phenomenon of NFT failure are also similarly dependent on the homologous temperature. Therefore, using a refractory metal may aid in preserving the dimensional stability of the NFT, for example the peg diameter and length (in a disc and peg type NFT) and the gap width (in a gap type NFT).
The use of such materials also allows for the use of longer wavelengths of input energy. Longer wavelengths can allow the use of larger NFTs thereby allowing for better heat sinking Longer wavelengths can also allow the transposition of the plasmonic field away from the light delivery system, which can allow the magnetic pole to not be sloped away from the light delivery system. Furthermore, at longer wavelengths, materials such as silicon (Si) for example, become transparent. This can further allow for the design of channel waveguides with low loss tight bends.
In some embodiments, energy within the short wavelength infrared (SWIR) range (1.4 to 3 micrometers or 1400 nm to 3000 nm) can be utilized. In some embodiments, energy having wavelengths that are at least 1400 nm can be utilized. In some embodiments, energy having wavelengths from 1400 to 1600 nm can be utilized. Wavelengths such as those listed above can be useful with NFTs made of various materials. For example, refractory metals exhibit plasmonic behavior at the noted wavelengths.
Use of materials such as refractory metals or transition metals for NFTs may result in slightly lowered coupling efficiency, but that disadvantage may be considered compensated for by the superior reliability thereof. Shifting the operating wavelengths to higher wavelengths, such as at least within the SWIR range also allows the use of high melting, environmentally stable and reliable plasmonic materials such as oxides (transparent conductive oxides for examples) and nitrides, which have lower losses compared to metals in the near- or mid-IR ranges. This may afford more options for materials (other than simply Al, Cu, Au and Ag for example) when higher wavelengths are utilized. The materials that can be used are also more rugged and reliable. It also becomes possible to engineer the band energy of the NFT via carrier concentration manipulation, doping, and alloying (within transition metals as well as with noble metals) for operation in the near- and mid-IR range. Furthermore, unlike monolithic Au, Ag, Al, or Cu, growth and deposition conditions of the new materials can be altered to tailor the plasmonic properties.
Possible materials for use in NFTs, as disclosed herein, can be compared by comparing the absolute value of the ratio of the real (n2-k2, where n is the refractive index and k is the extinction coefficient) to the imaginary part (2nk) of the permittivity. This ratio (ε real/ε imaginary) is referred to herein as the figure of merit (“FOM”). In some embodiments, materials that can be utilized in NFTs can include those materials where n2-k2 is very negative. In some embodiments, materials that can be utilized in NFTs can include materials where n2-k2 is not greater than −50. In some embodiments, materials that can be utilized in NFTs can include materials where n2-k2 is not greater than −60. In some embodiments, materials that can be utilized in NFTs can include those materials where the imaginary part, (2nk) is very small. In some embodiments, materials can be utilized in NFTs can include those materials where the imaginary part (2nk) is not greater than 30. In some embodiments, materials can be utilized in NFTs can include those materials where the imaginary part (2nk) is not greater than 25. Table 1 below presents data on various materials.
High temperature deformation processes (e)′ are a diffusional Arrhenius phenomenon, governed by the general equation: de/dt=(d/dt) const exp (−Q/RT), where de/dt is the reaction rate of the thermally activated process (which could lead to failure), Q is the activation energy for the process leading to potential failure, R is the universal gas constant, and T is the absolute temperature in Kelvin. Thus, high temperature flow deformation and thus device failure (creep) occurs faster at higher temperatures. Also, the lower melting the metal, the higher is the temperature driven creep deformation. For high temperature (creep) reliability, the concept of a homologous temperature is thus useful. The homologous temperature is the actual temperature divided by the melting point of the material, which both being expressed in Kelvin (K). In general, creep tends to occur at a significant rate when the homologous temperature is 0.4 or higher. Thus, the higher melting point a material has, the lower is its homologous temperature and lower is its temperature-driven dimensional stability. Table 2 below presents some physical properties of some of the materials disclosed above.
Disclosed herein are NFTs that can include, for example, tantalum (Ta), niobium (Nb), molybdenum (Mo), rhodium (Rh), ruthenium (Ru), osmium (Os), titanium (Ti), zirconium (Zr), yttrium (Y), hafnium (Hf), platinum (Pt), palladium (Pd), vanadium (V), chromium (Cr), iridium (Ir), scandium (Sc), niobium (Ni), cobalt (Co), rhenium (Re), silicon carbide (SiC), silicon (Si), geranium (Ge), boron (B), carbon (C), alloys thereof, dispersions containing these elements, intermetallics based on these elements, admixtures thereof, or combinations thereof. In some embodiments, disclosed NFTs can include Ta, Nb, Mo, W, Pd, Os, Rh, cobalt-fcc, Ir, V, TaN, or TiN, for example. In some embodiments, disclosed NFTs can include Ta, Nb, Mo, or W, for example.
Also disclosed herein are NFTs that can include, for example, conducting oxides such as doped or undoped oxides of zinc (Zn), tin (Sn), indium (In), and mixtures thereof, perovskites, alloys of Group III and Group V elements.
Also disclosed herein are NFTs that can include, for example, cadmium (Cd), barium (Ba), arsenic (As), polonium (Po), ytterbium (Yb), Promethium (Pm), protactinium (Pa), alloys thereof, dispersions containing these elements, intermetallics based on these elements, admixtures thereof, or combinations thereof.
Also disclosed herein are NFTs that can include, for example, tantalum (Ta), niobium (Nb), molybdenum (Mo), rhodium (Rh), ruthenium (Ru), osmium (Os), titanium (Ti), zirconium (Zr), yttrium (Y), hafnium (Hf), platinum (Pt), palladium (Pd), vanadium (V), chromium (Cr), iridium (Ir), scandium (Sc), niobium (Nb), cobalt (Co), rhenium (Re), silicon carbide (SiC), silicon (Si), geranium (Ge), boron (B), carbon (C), tungsten (W), iron (Fe), nickel (Ni), yttrium (Y), tin (Sn), antimony (Sb), bismuth (Bi), erbium (Er), gadolinium (Gd), indium (In), manganese (Mn), lanthanides and actinides and their alloys, dispersions containing these elements, intermetallics based on these elements such as but not limited to binary and ternary silicides, aluminides, germanides, nitrides, carbides of various stoichiometry of Niobium, Tantalum, Titanium, Palladium, Tungsten, Osmium, Rhodium, Cobalt, Iron, Aluminum, Molybdenum, Nickel, Vanadium, zirconium, Hafnium, Tin, Gadolinium, Erbium, Gallium, Indium, alloys of the above with group I elements such as Li, Na, K, etc., admixtures thereof, or combinations thereof.
Also disclosed herein are NFTs that can include gold (Au), silver (Ag), aluminum (Al), copper (Cu), or alloys thereof alloyed with or mixed with any element or material listed herein. Additionally, any alloys or material can also optionally include nitrogen (N), phosphorus (P), oxygen (O), sulfur (S), beryllium (Be), calcium (Ca), cerium (Ce), zinc (Zn), arsenic (As), selenium (Se), tellurium (Te), or mixtures thereof.
Disclosed alloys can include binary, ternary, or quaternary alloys. Binary and ternary alloys, for example, based on any element or elements listed herein, as well as with nitrogen (N), phosphorus (P), Group I elements, or combinations thereof can be utilized, for example. Alloying elements and constituents can be incorporated as constituents for solute strengthening, solute-based grain boundary pinning strengthening, dispersoid strengthening, interfacial strengthening, and diffusional rate modifications in the NFT material, for example.
Additionally, any type of dispersion, or any type of admixture can be utilized in disclosed NFTs. Additionally, intermetallics can be utilized. Illustrative types of intermetallics can include, for example, binary and ternary silicides, aluminides, germanides, nitrides, or carbides of various stoichiometries can be utilized. Additionally, perovskites, conductive oxides, and silicides, for example can be utilized on their own to form a NFT. Alternatively, conductive oxides, silicides, or perovskites can be utilized in composited or layered structures with plasmonic metals, alloys, or both, for example.
The present disclosure is illustrated by the following examples. It is to be understood that the particular examples, assumptions, modeling, and procedures are to be interpreted broadly in accordance with the scope and spirit of the invention as set forth herein.
NFTs made of tantalum (Ta) and gold (Au) were modeled in order to compare their coupling efficiency (CE).
All scientific and technical terms used herein have meanings commonly used in the art unless otherwise specified. The definitions provided herein are to facilitate understanding of certain terms used frequently herein and are not meant to limit the scope of the present disclosure.
As used in this specification and the appended claims, “top” and “bottom” (or other terms like “upper” and “lower”) are utilized strictly for relative descriptions and do not imply any overall orientation of the article in which the described element is located.
As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” encompass embodiments having plural referents, unless the content clearly dictates otherwise.
As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise. The term “and/or” means one or all of the listed elements or a combination of any two or more of the listed elements.
As used herein, “have”, “having”, “include”, “including”, “comprise”, “comprising” or the like are used in their open ended sense, and generally mean “including, but not limited to”. It will be understood that “consisting essentially of”, “consisting of”, and the like are subsumed in “comprising” and the like. For example, a conductive trace that “comprises” silver may be a conductive trace that “consists of” silver or that “consists essentially of” silver.
As used herein, “consisting essentially of,” as it relates to a composition, apparatus, system, method or the like, means that the components of the composition, apparatus, system, method or the like are limited to the enumerated components and any other components that do not materially affect the basic and novel characteristic(s) of the composition, apparatus, system, method or the like.
The words “preferred” and “preferably” refer to embodiments that may afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, and is not intended to exclude other embodiments from the scope of the disclosure, including the claims.
Also herein, the recitations of numerical ranges by endpoints include all numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc. or 10 or less includes 10, 9.4, 7.6, 5, 4.3, 2.9, 1.62, 0.3, etc.). Where a range of values is “up to” a particular value, that value is included within the range.
Use of “first,” “second,” etc. in the description above and the claims that follow is not intended to necessarily indicate that the enumerated number of objects are present. For example, a “second” substrate is merely intended to differentiate from another infusion device (such as a “first” substrate). Use of “first,” “second,” etc. in the description above and the claims that follow is also not necessarily intended to indicate that one comes earlier in time than the other
Thus, embodiments of devices including near field transducers are disclosed. The implementations described above and other implementations are within the scope of the following claims. One skilled in the art will appreciate that the present disclosure can be practiced with embodiments other than those disclosed. The disclosed embodiments are presented for purposes of illustration and not limitation.
This application claims priority to U.S. Provisional Application No. 61/945,884 entitled “DEVICES INCLUDING NEAR FIELD TRANSDUCERS” filed on Feb. 28, 2014, the disclosure of which is incorporated herein by reference thereto.
| Number | Date | Country | |
|---|---|---|---|
| 61945884 | Feb 2014 | US |
