Abstract:
The embodiments disclose a data storage device including a thickness gradient heat sink layer deposited over a heat sink layer deposited over a substrate, a thickness gradient non-magnetic thermal resist layer deposited over the thickness gradient heat sink layer, and a magnetic layer deposited over the thickness gradient non-magnetic thermal resist layer.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on U.S. Provisional Patent Application Ser. No. 61/778,370 filed Mar. 12, 2013, entitled “A Radially Dependent Thermal Heat Resistor Layer”, by First Named Inventor René van de Veerdonk. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a block diagram of an overview of a radially dependent thermal heat resistor layer of one embodiment. 
       FIG. 2  shows for illustrative purposes only an example of a thickness gradient heat sink layer of one embodiment. 
       FIG. 3  shows for illustrative purposes only an example of a radially dependent thermal heat resistor layer structure of one embodiment. 
       FIG. 4A  shows for illustrative purposes only an example of a thickness gradient heat sink layer deposition of one embodiment. 
       FIG. 4B  shows for illustrative purposes only an example of a non-magnetic thermal resist layer deposition of one embodiment. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In a following description, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration a specific example in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural changes may be made without departing from the scope of the present invention. 
     General Overview: 
     It should be noted that the descriptions that follow, for example, in terms of a radially dependent thermal heat resistor layer is described for illustrative purposes and the underlying system can apply to any number and multiple types sputter sources. In one embodiment of the present invention, the radially dependent thermal heat resistor layer can be configured using an intentional variation across the radial direction of media surface. The radially dependent thermal heat resistor layer can be configured to include a graded thermal resistor layer and can be configured to include a thickness and/or composition gradient across the radius of the disk using the present invention. Herein the term “graded” has a contextual meaning of an intentional variation across the radial direction of a media surface. 
     Heat Assisted Magnetic Recording (HAMR) is a novel recording technology slated for implementation in future hard-disk drives. The technology is based on heating the media to reduce its effective coercivity, and recording the information while the media cools down in an applied magnetic field. The speed of heating and cooling is critical in the recording process. This rate is controlled by the linear velocity of the recording head and the thermal time constant of the media. 
     The media layer stack is designed such that there is a thermal resistor layer directly underneath the recording layer. By tuning the properties of this layer (using thickness, composition, and/or multi-layering) the thermal time constant of the media can be matched to the requirements of the recording head. The result with this approach is that the linear velocity of the media is not a constant across the stroke of the media. For example, at a near-ID radius of 15 mm, the linear velocity will be half that of a near-OD radius of 30 mm due to tangential speeds. This means that the thermal time-constant for the media cannot be matched across the full stroke of the media surface. 
     The radially dependent thermal heat resistor layer uses a graded thermal resistor layer, where graded in this context means an intentional variation across the radial direction of media surface. Using triatron or other dedicated sputter sources, it is possible to engineer a thickness and/or composition gradient across the radius of the disk. By engineering the thermal resistor properties as a function of the radial position on the disk, the media thermal time constant profile can be matched against the linear velocity profile. This in turn will translate in an improved robustness of the HAMR recording system. 
       FIG. 1  shows a block diagram of an overview of a radially dependent thermal heat resistor layer of one embodiment.  FIG. 1  shows a radially dependent thermal heat resistor layer and heat sink layer  100 . The radially dependent thermal heat resistor layer and heat sink layer includes at least two inverse gradient layers across a radius of the device. The radially dependent thermal heat resistor layer and heat sink layer  100  includes a graded thermal resistor layer and heat sink layer, wherein graded in this context means an intentional variation across the radial direction of media surface  110 . 
     The intentional variations across the radial direction of media surface is created using a thickness and/or composition gradient structure in the graded thermal resistor layer and heat sink layer across the radius of the disk using a dedicated sputter sources  120 . The intentional variations in the gradient structure includes at least two inverse gradient layers configured to include a thickness range configured as linear, parabolic, polynomial or other forms that are adaptive according to thermal conditions and simulations  130 . The gradient structure includes a thermal heat resistor layer and heat sink layer with properties pre-determined as a function of the radial position on a disk, wherein the media thermal time constant profile can be matched against the linear velocity profile creating a robustness of the HAMR recording system  140  of one embodiment. 
     Detailed Description 
       FIG. 2  shows a block diagram of an overview flow chart of a thickness gradient heat sink layer of one embodiment.  FIG. 2  shows a substrate  200  wherein the substrate  200  is circular and includes an inner diameter, ID  210  and an outer diameter, OD  220 . The substrate  200  can include using materials including quartz, silicone and other materials. Deposited onto the substrate  200  is a continuous heat sink layer  230  with a constant thickness. The continuous heat sink layer  230  can include using materials with predetermined properties of thermal conductivity of one embodiment. 
     A thickness gradient heat sink layer  240  is deposited on the continuous heat sink layer  230 . The thickness gradient heat sink layer  240  is part of the gradient structure that compensates for recording tangential speeds with heat assisted magnetic recording  250 . The thickness gradient heat sink layer  240  can include using materials with predetermined properties of thermal conductivity.  FIG. 2  shows where from the ID  210  the thickness gradient heat sink layer  240  is diminishing in thickness as the radial distance increases toward to OD  220 . The thickness gradient of the thickness gradient heat sink layer  240  material is configured to correlate to the changes in the linear velocity of the recording head and the thermal time constant of the media of one embodiment. The fabrication process is further described in  FIG. 3 . 
       FIG. 3  shows a block diagram of an overview flow chart of a radially dependent thermal heat resistor layer structure of one embodiment.  FIG. 3  shows a continuation from  FIG. 2  that includes a non-magnetic graded thermal resist layer  300  deposited on top of the thickness gradient heat sink layer  240  on the continuous heat sink layer  230 . The non-magnetic graded thermal resist layer  300  is part of the gradient structure that compensates for recording tangential speeds with heat assisted magnetic recording  250 . The non-magnetic graded thermal resist layer  300  can include using materials including with predetermined properties of thermal conductivity of one embodiment. 
       FIG. 3  shows the thickness of the non-magnetic graded thermal resist layer  300  diminishing from the OD  220  to the ID  210  of the substrate  200 . The thickness gradient of the non-magnetic graded thermal resist layer  300  material is configured to correlate to the changes in the linear velocity of the recording head and the thermal time constant of the media of one embodiment. 
     On top of the non-magnetic graded thermal resist layer  300  magnetic features  310  are formed by deposition magnetic materials that can be patterned and used in a heat assisted magnetic recording (HAMR) mode of operation. A HAMR recording system  320  applies heat to the magnetic features  310  to facilitate the recording operation. The gradient structure including the non-magnetic graded thermal resist layer  300 , thickness gradient heat sink layer  240  and continuous heat sink layer  230  are used to control the heat level in the magnetic features  310  during a recording operation. 
     The control the heat level in the magnetic features  310  during a recording operation includes compensating graded heat dissipation  330  of the recording head heat assist  340 . The control of the heat dissipation corresponds to the linear velocity of the recording head as it changes with the movement of the recording head back and forth between the ID  210  and OD  220  of the substrate  200 . The rate of dissipation using a radially dependent thermal heat resistor layer structure  350  compensates for the thermal time constant of the media of one embodiment. 
       FIG. 4A  shows for illustrative purposes only an example of a thickness gradient heat sink layer deposition of one embodiment.  FIG. 4A  shows a dedicated sputter source  400  used to make a thickness gradient heat sink layer deposition  410  on top of the continuous heat sink layer  230 . The dedicated sputter source  400  deposits a thickness=A1  420  at the OD  220  of the substrate  200 . The dedicated sputter source  400  is configured to increase the thickness of the thickness gradient heat sink layer  240  deposition to a thickness A2&gt;A1 and ≦2×a1  430  at the ID  210  of the substrate  200 . The gradient of the graded heat sink layer across the radius of the device is configured to include a thickness range configured as linear, parabolic, polynomial or other forms that are adaptive according to thermal conditions and simulations. The gradient heat sink layer  240  includes for example a thickness range: A1: 5 to 200 nm  425  of one embodiment. 
       FIG. 4B  shows for illustrative purposes only an example of a non-magnetic thermal resist layer deposition of one embodiment.  FIG. 4B  shows a dedicated sputter source  400  used for a non-magnetic graded thermal resist layer deposition  440 . The non-magnetic graded thermal resist layer deposition  440  has a thickness=B1  450  at an inner circumference ID  210  and at the outer circumference OD  220  a thickness B2&gt;B1 and ≦2×B1  460 . The gradient of the non-magnetic graded thermal resist layer across the radius of the device is configured to include a thickness range configured as linear, parabolic, polynomial or other forms that are adaptive according to thermal conditions and simulations. The non-magnetic graded thermal resist layer deposition  440  includes for example a thickness Range: B1: 1 to 50 nm  455  of one embodiment. 
     The top surface of the non-magnetic graded thermal resist layer deposition  440  is a smooth level surface  470  parallel to the substrate  200  and of a non-coarse finish free of undulating topography. The non-magnetic graded thermal resist layer  300  is deposited on the thickness gradient heat sink layer  240 , which is on top of the heat sink layer  230  on and in contact with the substrate  200  of one embodiment. 
     The foregoing has described the principles, embodiments and modes of operation of the present invention. However, the invention should not be construed as being limited to the particular embodiments discussed. The above described embodiments should be regarded as illustrative rather than restrictive, and it should be appreciated that variations may be made in those embodiments by workers skilled in the art without departing from the scope of the present invention as defined by the following claims.