Patent Application
20080026255
The accompanying drawings, which are included to provide further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings:
In the following detailed description, numerous specific details are set forth to provide a full understanding of the present invention. It will be apparent, however, to one ordinarily skilled in the art that the present invention may be practiced without some of these specific details. In other instances, well-known structures and techniques have not been shown in detail to avoid unnecessarily obscuring the present invention.
Heat-assisted magnetic recording (“HAMR”) is a technology with the potential to solve a number of fundamental problems concerning thermal fluctuation and write capability in magnetic recording media with very high areal densities (e.g., higher than 400 Gbit/in2). At these high areal densities, the use of magnetic materials with a high magnetocrystalline anisotropy constant (“Ku”) (e.g., higher than conventional CoCrPt-based alloys) becomes imperative. For example, materials such as FePt, CoPt or Co5Sm may be used. Due to the high coercivity (“Hc”) of such materials, however, the write head(s) of a magnetic recording device may be unable to generate a sufficiently strong magnetic field to write to the medium.
To address this issue, in heat-assisted magnetic recording, the recording medium is heated locally during a write operation. Elevating the temperature of the recording medium decreases the coercivity thereof, thereby reducing the strength of the magnetic field required to successfully write to the medium. Accordingly, in HAMR, a highly focused laser beam with a very small spot size (e.g., in the nano-meter range) is used to heat the magnetic medium so that write operations can be performed on the high Ku magnetic data storage layer. This localized heating generates significant heat flux, which, if not dissipated efficiently, may lead to instabilities (e.g., due to the phase transformation of the materials of the different intermediate layers in the media stack as well as interdiffusion and interfacial reactions between the layers).
In accordance with various embodiments of the present invention, therefore, magnetic recording media with improved heat dissipation for use in heat-assisted magnetic recording and methods for making such media are provided.
Magnetic data storage layer 107 includes a plurality of magnetic grains 107a separated by a plurality of grain boundary phases 107b. Grain boundary phases 107b have a higher thermal conductivity than magnetic grains 107a. Similarly, the intermediate layers 104-106 each have crystalline phase grains separated by grain boundary phases. For example, underlayer 106 has crystalline phase grains 106a separated by grain boundary phases 106b, and orientation control layer 105 has crystalline phase grains 105a separated by grain boundary phases 105b. The grain boundary phases for each of the intermediate layers have a higher thermal conductivity than the crystalline phase grains of the same layer. For example, grain boundary phases 106b are more thermally conductive than crystalline phase grains 106a, and grain boundary phases 105b are similarly more thermally conductive than crystalline phase grains 105a.
With this design, the grain boundary phases in the intermediate layers provide high thermal conductivity conduits for dissipating heat generated (e.g., by a HAMR laser) in magnetic data storage layer 107 to heatsink layer 103. The dissipation of this heat prevents interdiffusion and interfacial reactions between magnetic data storage layer 107 and adjacent layers. It also prevents the materials of magnetic data storage layer 107 and other layers from undergoing phase transformation due to excessive heat flux.
According to one aspect of the present invention, by providing crystalline phase grains that are columnar and oriented substantially perpendicular (i.e., along an axis connecting the magnetic data storage layer and the heat sink layer), the heat transport from magnetic data storage layer 107 to heatsink layer 103 may be improved. According to an additional aspect of the present invention, the grain boundary phases of the intermediate layers have a higher thermal conductivity than the magnetic grains in magnetic data storage layer 107, for improving heat dissipation from magnetic data storage layer 107 to heatsink layer 103.
According to an additional aspect of the present invention, heatsink layer 103 has a greater thermal conductivity than the magnetic grains of magnetic data storage layer 107, for improving heat dissipation from magnetic data storage layer 107 to heatsink layer 103. For example, heatsink layer 103 may include materials such as copper (“Cu”), silver (“Ag”), gold (“Au”) and/or alloys thereof.
While the foregoing exemplary embodiment of a magnetic recording medium has been described as including a substrate layer, a pre-coat layer and an overcoat layer, the scope of the present invention is not limited to such an arrangement. Rather, as will be apparent to one of skill in the art, the present invention has application to magnetic recording media without any of these layers, with some of these layers, and with other layers not enumerated herein. Moreover, while the intermediate layers depicted above with reference to the present exemplary embodiment have included a miscellaneous layer, an orientation control layer and an underlayer, the scope of the present invention is not limited to such an arrangement of intermediate layers. Rather, the present invention expressly contemplates arrangements in which any number of intermediate layers, including a single intermediate layer, are disposed between the heatsink layer and the magnetic data storage layer. Moreover, these intermediate layers may or may not include any of the particular intermediate layers described herein (e.g., underlayer, orientation control layer, etc.).
According to one embodiment of the present invention, the grain boundary phases and crystalline phase grains in the different intermediate layers and in the magnetic data storage layer may vary in composition, width (i.e., cross sectional area), and/or volume fraction.
Magnetic data storage layer 207 includes a plurality of magnetic grains 207a separated by a plurality of grain boundary phases 207b. Grain boundary phases 207b have a higher thermal conductivity than magnetic grains 207a. Similarly, the intermediate layers 204-206 each have crystalline phase grains separated by grain boundary phases. The grain boundary phases (e.g., 205b, 206b) for each of the intermediate layers all have a higher thermal conductivity than that of the crystalline phase grains (e.g., 205a, 206a) of the same layer. As can be seen with reference to
Turning to
While for the sake of simplicity, the exemplary embodiment described above has been illustrated in
In step 403, one or more intermediate layers are formed over the heatsink layer. The intermediate layers may be formed by magnetron sputtering, physical vapor deposition, chemical vapor deposition, or by any other process known to those of skill in the art. The one or more intermediate layers may include one or more underlayers, orientation control layers, or any other magnetic or non-magnetic layer known to those of skill in the art. Each intermediate layer includes crystalline phase grains separated by grain boundary phases with a higher thermal conductivity than that of the crystalline phase grains. In step 404, a magnetic data storage layer is formed over the one or more intermediate layers provided in step 403. The data storage layer may likewise be formed by magnetron sputtering, physical vapor deposition, chemical vapor deposition, or by any other process known to those of skill in the art. The magnetic data storage layer includes magnetic grains separated by grain boundary phases with a higher thermal conductivity than that of the magnetic grains. In optional step 405, one or more overcoat layers are provided (e.g., by sputtering) over the magnetic data storage layer provided in step 404.
According to one aspect of the present invention, the materials of the grain boundary phases in both the magnetic data storage layer and the one or more intermediate layers have little or no (e.g., less than 10 atomic percent) solid solubility in the material constituting the grains in the same layer. Moreover, according to an additional aspect of the present invention, the material of the grain boundary phases in the one or more intermediate layers have little or no (e.g., less than 10 atomic percent) solid solubility in the material of the magnetic grains of the magnetic data storage layer.
According to one aspect of the present invention, the material of the grain boundary phases of both the magnetic data storage layer and the one or more intermediate layers may be a metallic element or alloy which is insoluble (e.g., having less than 10 atomic percent solid solubility) in the grains of the same layer. According to an alternative aspect of the present invention, the grain boundary phase material may be a ceramic (e.g., an oxide, boride, carbide, nitride, silicate, etc.) which is similarly insoluble (e.g., having less than 10 atomic percent solid solubility) in the grains of the same layer. According to yet another aspect of the present invention, the grain boundary phase material may be a combination of a ceramic and a metal or metal alloy.
Table 1, below, illustrates several exemplary materials which may be utilized in the grain boundary phases of different layers in a magnetic recording medium according to various aspects of the present invention. As can be seen with reference to Table 1, the thermal conductivity (“k”) of each potential material is higher than that of the material of the grains of the same layer (e.g., cobalt for the magnetic data storage layer, ruthenium for the underlayer, nickel for the orientation control layer).
For example, as can be seen with reference to Table 1, above, molybdenum (“Mo”) may be an appropriate material for the grain boundary phases in a nickel-based orientation control layer according to one embodiment of the present invention, as molybdenum is insoluble in nickel at room temperature, and has a higher thermal conductivity than that of nickel (i.e., 138>60.7). Molybdenum, however, may not be an appropriate choice for use in the grain boundary phases of a cobalt-based magnetic data storage layer or a ruthenium-based underlayer, as it is soluble in both cobalt and ruthenium at room temperature. For similar reasons, tungsten (“W”) may be appropriate for use in the grain boundary phases of a cobalt-based magnetic data storage layer, but not a ruthenium-based underlayer or a nickel-based orientation control layer.
While the present invention has been particularly described with reference to the various figures and embodiments, it should be understood that these are for illustration purposes only and should not be taken as limiting the scope of the invention. There may be many other ways to implement the invention. Many changes and modifications may be made to the invention, by one having ordinary skill in the art, without departing from the spirit and scope of the invention.
The present application claims the benefit of priority under 35 U.S.C. §119 from U.S. Provisional Patent Application Ser. No. 60/833,809 entitled “ALLOY AND ARCHITECTURE DESIGN FOR HEAT-ASSISTED MAGNETIC RECORDING,” filed on Jul. 28, 2006, the disclosure of which is hereby incorporated by reference in its entirety for all purposes.
| Number | Date | Country | |
|---|---|---|---|
| 60833809 | Jul 2006 | US |
