Apparatuses and methods for absorbing optical energy

Provided herein is an apparatus including a substrate and a magnetic recording layer over the substrate. In addition, a thermochromic layer is over the substrate, wherein the thermochromic layer includes a first optical absorbance at a first temperature and a second optical absorbance at a second temperature.

BACKGROUND

Heat-assisted magnetic-recording (“HAMR”) media absorbs incoming light energy during write operations. The light energy may be absorbed by one or more layers, for example including the topmost overcoat layer and/or the recording layer. Absorption of the light energy creates a temporal Gaussian thermal spot on the media. The magnitude of an applied optical power and a cross-track width of the spot used during the write operations are a function of the material composition of the media layers. For example, overcoat materials that absorb a significant amount of the light energy leave a smaller magnitude of energy for write operations.

SUMMARY

Provided herein is an apparatus including a substrate and a magnetic recording layer over the substrate. In addition, a thermochromic layer is disposed over the substrate, wherein the thermochromic layer includes a first optical absorbance at a first temperature and a second optical absorbance at a second temperature. These and other features and advantages will be apparent from a reading of the following detailed description.

DESCRIPTION

Before various embodiments are described in greater detail, it should be understood that the embodiments are not limiting, as elements in such embodiments may vary. It should likewise be understood that a particular embodiment described and/or illustrated herein has elements which may be readily separated from the particular embodiment and optionally combined with any of several other embodiments or substituted for elements in any of several other embodiments described herein.

It should also be understood that the terminology used herein is for the purpose of describing the certain concepts, and the terminology is not intended to be limiting. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood in the art to which the embodiments pertain.

Heat-assisted magnetic-recording (“HAMR”) media absorbs incoming light energy into several layers during write operations. Absorption of the light energy creates a temporal Gaussian thermal spot in the media. The magnitude of an applied optical power and a width of the spot are a function of the material composition of the media layers. Thus, for example, an overcoat layer may include materials that absorb a significant amount of the light energy. As a result, a smaller amount of light energy is used for recording functions (e.g. switching magnetizations) in the media, thereby saving power. However, the thermal spot created in such media may spread quickly, resulting in a deleterious thermal bloom. Such a thermal bloom may quickly grow, spreading heat into undesired areas of the media and resulting in decreased signal-to-noise (“SNR”) ratio and recording problems.

As a result of the foregoing, embodiments described herein use a thermochromic material deposited within the media layers. The thermochromic material has a relatively low optical heat absorbance and low thermal conductivity at room temperature, thereby acting as an insulator. However when heated, the thermochromic material switches to a relatively high optical heat absorbance within a thermal spot, thereby acting as a conductor. Although the thermal spot has a high optical heat absorbance, a low (e.g. room temperature) thermal conductivity is maintained outside of the thermal spot.

Referring now toFIG. 1, a HAMR media stack100including a thermochromic layer above a granular magnetic recording layer is shown according to one aspect of the present embodiments. A substrate102is provided. In various embodiments, the substrate102may be disc shaped and may include a non-magnetic metal, alloy, or non-metal. For example, the substrate102may comprise aluminum, an aluminum alloy, glass, ceramic, glass-ceramic, polymeric material, a laminate composite, or any other suitable non-magnetic material.

Overlying the substrate102are one or more layers of a layer stack104. The layer stack104may include, for example, a soft magnetic underlayer (“SUL”). For example, the SUL104may be a 10 to 2000 Å thick layer including a soft magnetic material such as Ni, NiFe, Co, CoZr, CoZrCr, CoZrNb, CoCrTaB, CoCrB, CoCrTa, CoFe, Fe, FeN, FeSiAl, FeSiAlN, FeCoC, etc. In some embodiments, the SUL may include multiple layers, and the multiple SUL layers may be separated by one or more layers (e.g. Ru layers). In addition, the layer stack104may include one or more seed layers and intermediate layers to promote growth and fix orientations (e.g. face-centered cubic (“fcc”) structure in (111) orientation, hexagonal close-packed (“hcp”) structure in (0002) orientation, or others). It is understood that the above are non-limiting examples of layers in the layer stack104. The layer stack104may include any number or combinations of layers used in magnetic recording media.

Also overlying the substrate102may be a heat sink layer106. In the illustrated embodiment, the heat sink layer106also overlies the layer stack104and is under a recording layer107. However, it is understood that one or more heat sink layers may be positioned anywhere within the HAMR media stack100, including within the recording layer107. In various non-limiting embodiments, the thickness of the heat sink layer106may be, for example, 5 to 50 nm. In addition, the heat sink layer106may include one or more materials having high thermal conductivity to dissipate heat (e.g. Cu, Ag, Al, Au, CuZr, etc.).

Overlying the heat sink layer106is the recording layer107, which may also be referred to as a magnetic recording layer. The recording layer107includes granular columns108for magnetically storing information. The granular columns108may include one or more magnetic and non-magnetic layers (not shown) that are stacked together for magnetically storing information. For example, the granular columns108may include various magnetic layers that are ferromagnetically and/or antiferromagnetically coupled together, and which may be separated by one or more non-magnetic layers. The granular columns108are separated by non-magnetic spacers110. The non-magnetic spacers110are a segregant for physically separating the granular columns108and therefore magnetically decoupling the granular columns108from each other. Various embodiments may include the recording layer107in various positions within the HAMR media stack100. Furthermore, various embodiments may include more than one of the recording layer107.

In embodiments described herein, heat is locally applied (e.g. a thermal spot) to the HAMR media stack100during write operations in order to lower the magnetic anisotropy of a predetermined regions of the recording layer107. A magnetic field is then applied in order to adjust the magnetization of the of the granular columns108. While the granular columns are heated, a lower magnetic field is needed as compared to cooler granular columns.

In the illustrated embodiment ofFIG. 1, a thermochromic layer112overlies the recording layer107. The thermochromic layer112includes thermochromic materials that switch between a nominal optical absorbance at room temperature to a relatively high optical absorbance at certain transition temperatures. At the transition temperature of the material, the optical absorbance increases very rapidly. As such, the thermochromic layer112helps to prevent thermal bloom (e.g. the rapid spread of heat) by confining higher temperatures to predetermined regions of the HAMR media stack100and reducing the lateral spread of heat. Outside of predetermined heated regions (e.g. a thermal spot), the thermochromic layer112maintains a low thermal conductivity and remains at temperatures below the magnetization switching temperature, for example room temperature (e.g. 15° C. to 22° C.).

In various embodiments, the thermochromic layer112may be about 1 nm to about 25 nm thick and may be deposited, for example with deposition methods used in the art (e.g. sputter deposition, etc.). As previously discussed, the thermochromic layer112maintains a low thermal conductivity in areas (e.g. outside of the thermal spot) at temperatures below the transition temperature or magnetization switching temperature. By utilizing thermochromic materials with a high magnetization switching temperature, the thermal spot in the HAMR media may be narrowed while enhancing the absorbance. Some non-limiting examples of materials exhibiting the foregoing properties include, for example:

MaterialTransition TemperatureVO2~60° C.Ag/O290° C.Ge20Te80~70° C.Ti2O3~230° C.NbO2800° C.V2O5257° C.SmNiO3~130° C.EuNiO3~220° C.GdNiO3~235° C.YiNiO3~300° C.
Transition temperatures are the approximate switching temperatures between the low absorbance state and the high absorbance state. As such, the optical absorbance increases rapidly with temperature. Therefore, the thermochromic layer112includes a first optical absorbance at a first temperature below the switching temperature, and a second optical absorbance at a second temperature above the switching temperature, wherein the second optical absorbance is higher than the first optical absorbance.

In various embodiments, a protective overcoat114overlies the thermochromic layer112. The protective overcoat114is a protective layer including, for example, a carbon overcoat, diamond-like carbon, silicon nitride, or other protective material including the properties of corrosion protection and/or mechanical protection. In various embodiments, the protective overcoat114may also perform other functions and may be more than one layer.

In various embodiments, a lubricant layer116overlies the protective overcoat114. The lubricant layer116may be, for example, a perfluoropolyether material or other lubricant material. It is understood that embodiments may include lubricant layers with various compositions. In some embodiments, the lubricant layer116may be omitted, included in the protective overcoat114, or may be more than one layer.

It is understood that any of the aforementioned layers in the embodiments described above may be rearranged in any order. For example, the heat sink layer106may overlie the recording layer107. In addition, any of the aforementioned layers in the embodiments described above may be in overlying contact (e.g. direct contact) with each other in various arrangements. For example, the heat sink layer106may be in overlying contact with the layer stack104or the substrate102. Alternatively, the heat sink layer106may overlie the layer stack104or the substrate102with intervening layers in-between.

Referring now toFIG. 2, a figurative illustration of temperature and thermal spot width of media with a thermochromic layer and media without a thermochromic layer is shown according to one aspect of the present embodiments. As discussed above, a thermal spot may be used with HAMR media to locally heat a region in order to lower the magnetic anisotropy of the recording layer107. As a result, magnetizations in the recording layer107are easier to switch and less writing power is needed.

As figuratively illustrated, a media stack200without the thermochromic layer112has a Gaussian thermal spot232with a width of230. On the other hand, the HAMR media stack100with the thermochromic layer107has a Gaussian thermal spot236with a width of234, also figuratively illustrated. As can be seen, the Gaussian thermal spot236of the HAMR media stack100is much narrower than the Gaussian thermal spot232of the media stack200. The narrower Gaussian thermal spot236of the HAMR media is a result of the thermochromic layer112. Therefore, the thermochromic layer112helps to confine the thermal region to a narrower predetermined location on the HAMR media stack100, thereby preventing thermal bloom.

Referring now toFIG. 3, a HAMR media stack300including a thermochromic layer above an overcoat layer is shown according to one aspect of the present embodiments. A substrate302is provided. A layer stack304, a heat sink layer306, and a recording layer307all overlie the substrate302. The recording layer307includes granular columns308that are separated by non-magnetic spacers310. An overcoat layer314overlies the recording layer307, and a lubricant layer316overlies the overcoat layer314. In the present embodiment, a thermochromic layer312is between the overcoat layer314and the lubricant layer316. In various embodiments the thermochromic layer312may be in overlying contact with the overcoat layer314, and/or the lubricant layer316may be in overlying contact with the thermochromic layer312. As such, the overcoat layer314is a protective layer under the thermochromic layer312.

Referring now toFIG. 4a HAMR media stack400including a thermochromic layer under a granular magnetic recording layer is shown according to one aspect of the present embodiments. A substrate402is provided. A layer stack404, a heat sink layer406, and a recording layer407all overlie the substrate402. The recording layer407includes granular columns408that are separated by non-magnetic spacers410. An overcoat layer414overlies the recording layer407, and a lubricant layer416overlies the overcoat layer414. In the present embodiment, a thermochromic layer412is between the heat sink layer406and the recording layer407. In various embodiments the thermochromic layer412may be in overlying contact with the heat sink layer406, and/or the recording layer407may be in overlying contact with the thermochromic layer412.

Referring now toFIG. 5, a HAMR media stack500including a thermochromic layer above a heat sink is shown according to one aspect of the present embodiments. A substrate502is provided. A layer stack504, a heat sink layer506, and a recording layer507all overlie the substrate502. The recording layer507includes granular columns508that are separated by non-magnetic spacers510. An overcoat layer514overlies the recording layer507, and a lubricant layer516overlies the overcoat layer514. In the present embodiment, a thermochromic layer512is between the heat sink layer506and the layer stack504. In various embodiments the thermochromic layer512may be in overlying contact with the layer stack504, and/or the heat sink layer506may be in overlying contact with the thermochromic layer512.

Referring now toFIG. 6, a HAMR media stack600including a thermochromic layer below a heat sink layer is shown according to one aspect of the present embodiments. A substrate602is provided. A layer stack604, a heat sink layer606, and a recording layer607all overlie the substrate602. The recording layer607includes granular columns608that are separated by non-magnetic spacers610. An overcoat layer614overlies the recording layer607, and a lubricant layer616overlies the overcoat layer614. In the present embodiment, a thermochromic layer612is between the layer stack604and the substrate602. In various embodiments the thermochromic layer612may be in overlying contact with the substrate602, and/or the layer stack604may be in overlying contact with the thermochromic layer612.

Referring now toFIG. 7, a HAMR media stack700including a thermochromic layer as a segregant within a granular magnetic recording layer is shown according to one aspect of the present embodiments. A substrate702is provided. A layer stack704, a heat sink layer706, and a recording layer707all overlie the substrate702. An overcoat layer714overlies the recording layer707, and a lubricant layer716overlies the overcoat layer714. In the present embodiment, the recording layer707includes granular columns708that are separated by a thermochromic layer712. In addition to the functionality described above, the thermochromic layer712in the present embodiment functions as a segregant, thereby separating the granular columns708as described above in other embodiments and functions as non-magnetic spacers that were described above inFIGS. 1-6. Therefore, it is understood that the recording layer707includes the granular columns708and the thermochromic layer712, which are each within the same horizontal plane, and the horizontal plane is with respect to the other layers of the HAMR media stack700, for example the heat sink layer706. In various embodiments the thermochromic layer712may be in overlying contact with the heat sink layer706, and/or the overcoat layer714may be in overlying contact with the thermochromic layer712.

Referring now toFIG. 8, a HAMR media stack800including a thermochromic layer as a segregant within a granular magnetic recording layer and another thermochromic layer over the granular recording layer is shown according to one aspect of the present embodiments. A substrate802is provided. A layer stack804, a heat sink layer806, and a recording layer807all overlie the substrate802. An overcoat layer814overlies the recording layer807, and a lubricant layer816overlies the overcoat layer814. In the present embodiment, the recording layer807includes granular columns808that are separated by a thermochromic layer813. In addition to the functionality described above, the thermochromic layer813in the present embodiment functions as a segregant, thereby separating the granular columns808as described above in other embodiments. In various embodiments the thermochromic layer813may be in overlying contact with the heat sink layer806.

In addition, the present embodiment includes another thermochromic layer812located between the recording layer807and the overcoat layer814. In various embodiments the thermochromic layer812may be in overlying contact with the recording layer807, and/or the overcoat layer814may be in overlying contact with the thermochromic layer812. As such, the thermochromic layer813within the recording layer807may include a first optical absorbance at a first temperature and a second optical absorbance at a second temperature, as described above. In addition, the thermochromic layer812overlying the recording layer807may include a third optical absorbance at a third temperature and a fourth optical absorbance at a fourth temperature. It is understood that the thermochromic layers (812,813) may include the same material(s) or different material(s) which will affect their properties described above. It is further understood that the position of the thermochromic layer812is not limited to the present embodiment, and other embodiments may position the thermochromic layer812anywhere within the HAMR media stack800.

Referring now toFIG. 9, a HAMR media stack900including two thermochromic layers is shown according to one aspect of the present embodiments. A substrate902is provided. A layer stack904, a heat sink layer906, and a recording layer907all overlie the substrate902. The recording layer907includes granular columns908that are separated by non-magnetic spacers910. An overcoat layer914overlies the recording layer907, and a lubricant layer916overlies the overcoat layer914. In the present embodiment, a thermochromic layer912is between the recording layer907and the overcoat layer914. In various embodiments the thermochromic layer912may be in overlying contact with the recording layer907, and/or the overcoat layer914may be in overlying contact with the thermochromic layer912.

In addition, the present embodiment includes another thermochromic layer918located between the overcoat layer914and the lubricant layer916. In various embodiments the thermochromic layer918may be in overlying contact with the overcoat layer914, and/or the lubricant layer916may be in overlying contact with the thermochromic layer918. As such, the thermochromic layer912may include a first optical absorbance at a first temperature and a second optical absorbance at a second temperature, as described above. In addition, the thermochromic layer918overlying the overcoat layer914may include a third optical absorbance at a third temperature and a fourth optical absorbance at a fourth temperature.

In some embodiments, the thermochromic layer912, closest to the recording layer907, may have a higher transition temperature than the thermochromic layer918, further away from the recording layer907and closer to the surface of the HAMR media stack900. However, it is understood that the thermochromic layers (912,918) may include the same material(s) or different material(s) which will affect their properties described above, and therefore further embodiments may include different combinations of switching temperatures for the thermochromic layers (912,918) (e.g. same switching temperature, higher switching temperature on top, lower switching temperature on top, etc.). It is further understood that the positions of the thermochromic layers (912,918) are not limited to the present embodiment, and other embodiments may position the thermochromic layers (912,918) anywhere within the HAMR media stack900, including in overlying contact with each other. Further embodiments may also include more than two thermochromic layers.

While the embodiments have been described and/or illustrated by means of particular examples, and while these embodiments and/or examples have been described in considerable detail, it is not the intention of the Applicants to restrict or in any way limit the scope of the embodiments to such detail. Additional adaptations and/or modifications of the embodiments may readily appear, and, in its broader aspects, the embodiments may encompass these adaptations and/or modifications. Accordingly, departures may be made from the foregoing embodiments and/or examples without departing from the scope of the concepts described herein. The implementations described above and other implementations are within the scope of the following claims.