Abstract:
A slider generally comprises a substrate forming at least part of a body of the slider, a heat-assisted media recording (HAMR) read/write transducer proximate the substrate, and an end cap substantially encapsulating the HAMR read/write transducer. The end cap has a first surface proximate the substrate and a second surface as a trailing edge of the slider. The end cap has a first coefficient of thermal expansion (CTE) similar to a corresponding CTE of the substrate. At least a portion of the second surface of the end cap has a second CTE that is lower than the first CTE. A body of the end cap is intermediate to the first and second surfaces of the end cap and has a CTE intermediate of the first and second CTE.

Description:
SUMMARY 
     A slider generally comprises a substrate forming at least part of a body of the slider, a heat-assisted media recording (HAMR) read/write transducer proximate the substrate, and an end cap substantially encapsulating the HAMR read/write transducer. The end cap has a first surface proximate the substrate and a second surface as a trailing edge of the slider. The end cap has a first coefficient of thermal expansion (CTE) similar to a corresponding CTE of the substrate. At least a portion of the second surface of the end cap has a second CTE that is lower than the first CTE. A body of the end cap is intermediate to the first and second surfaces of the end cap and has a CTE intermediate of the first and second CTE. 
     The above summary is not intended to describe each embodiment or every implementation. A more complete understanding will become apparent and appreciated by referring to the following detailed description and claims in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a HAMR a slider of an example embodiment. 
         FIG. 2  is a sectional view of a trailing edge cap of an example embodiment. 
         FIG. 3  is a sectional view of a trailing edge cap of an example embodiment. 
     
    
    
     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. 
     DETAILED DESCRIPTION 
     The present disclosure is directed to apparatus, systems and methods to reduce thermal profile changes of head sliders in heat assisted magnetic recording (HAMR) drives through the use of selected materials in the trailing edge cap and/or substrate of the slider body. 
     HAMR generally refers to the concept of locally heating a recording medium with a laser to reduce the coercivity. This allows the applied magnetic writing fields to more easily direct the magnetization during temporary magnetic softening caused by the heat source. HAMR allows for the use of small grain media, with a larger magnetic anisotropy at room temperature to assure sufficient thermal stability, which is desirable for recording at increased areal densities. HAMR can be applied to any type of magnetic storage media including tilted media, longitudinal media, perpendicular media, and patterned media. By heating the media, the coercivity is reduced such that the magnetic write field is sufficient to write to the media. Once the media cools to ambient temperature, the coercivity has a sufficiently high value to assure thermal stability of the recorded information. 
     In a HAMR magnetic data storage and retrieval system, a thin film transducing head, which is also known as a slider, may include a transducer, a substrate upon which the transducer is built, and an encapsulating end cap layer at the trailing edge of the transducing head. The transducer may include a writer portion, assisted by a thin beam laser, to record magnetically encoded information on a magnetic media and a reader portion to retrieve magnetically encoded information. During operation, the slider is positioned in close proximity to the magnetic media. The distance between the slider and the media is small enough to allow for writing to and reading from the magnetic media and large enough to prevent contact between the magnetic media and the slider. 
     During HAMR write operations the laser can be subject to a high power loss which is largely converted to heat. The heat affects the various layers/elements of the slider in different ways as each of the layers/elements are made from different materials having different coefficients of thermal expansion (CTEs). For example, the substrate of the slider is may be comprised of aluminum oxide/titanium carbide (AlTiC), the end cap layer of alumina, and the transducer of many layers including metals. The CTE for TiC is 7.7×10 −6 /° C. linear while the CTE for alumina is 8.1×10 −6 /° C. linear. Metallic layers have a very high CTE. All elements of the slider are subject to expansion and deformation caused by the heat of the laser. The deformed head slider will protrude towards the disk surface causing changes in head-disk clearance, which is controlled at nanometer range, for example, ˜1.5 nm or less, and in air-bearing flyability; these changes may lead to problematic clearance control and head-disk contact. The heat may also cause the elements along the path of the laser to expand in a lateral dimension which can affect servo and read/write performances of the slider head. Thermal-fly-height (TFC) heaters are used to help control thermal expansion to achieve a low flight-height recording; however, more can be done to control thermal expansion through the optimization of materials chosen for the slider body. 
       FIG. 1  illustrates a perspective view of an example HAMR recording head slider  100  attached to suspension  102 . Slider  100  presents an air bearing surface (ABS)  104 , a leading edge  106  and a trailing edge  108 , and generally comprises a substrate  110 , an optional insulating layer  112 , and an encapsulating trailing edge cap  114 . Trailing edge cap  114  encapsulates a magnetic HAMR transducer  116 , an electromagnetic energy source, e.g., laser,  118 , and other microelectronic and associated photonic elements and circuitry, which can include, for example, shields, TFC heaters, and sensors (not shown). Transducer  116  meets the ABS  104  at media facing surface interface  119 . Trailing edge cap  114  is additionally provided with external electrical contacts  120 . 
     As explained above, the trailing edge cap alumina and AlTiC substrate of slider bodies may have significant CTEs, which make them protrude/deform heavily under the write duty cycle laser heat in HAMR drives. To improve thermal profile changes, materials of low CTEs are used in slider bodies especially in high-heat areas. In an example embodiment, the sputtered alumina of the trailing edge cap  114  is replaced with a carbide, nitride, or oxide of a very low CTE. Preferred examples of materials for the trailing edge cap  114  and their CTE values are provided in Table 1 below, with the highest CTE value being 6.9×10 −6 /° C. linear. 
     
       
         
               
             
               
               
               
             
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Coefficient of Thermal Expansion  
               
               
                 of Selected Ceramics 
               
             
          
           
               
                   
                 Ceramic 
                 CTE (×10 −6 /° C.) 
               
               
                   
                   
               
             
          
           
               
                   
                 AlN 
                 4.6 
               
               
                   
                 BN 
                 2.2 
               
               
                   
                 Si 3 N 4   
                 3.3 
               
               
                   
                 GeN 
                 5.6 
               
               
                   
                 GaN 
                 4.5 
               
               
                   
                 B 4 C 
                 5.5 
               
               
                   
                 SiC 
                 2.8 
               
               
                   
                 HfC 
                 6.6 
               
               
                   
                 ZrC 
                 6.9 
               
               
                   
                 WC 
                 4.3 
               
               
                   
                 W 2 C 
                 5.8 
               
               
                   
                 NbC 
                 6.6 
               
               
                   
                 TaC 
                 6.3 
               
               
                   
                 HfB 2   
                 5.0 
               
               
                   
                 ZrB 2   
                 5.9 
               
               
                   
                 TiB 2   
                 5.5 
               
               
                   
                 VB 2   
                 5.3 
               
               
                   
                 CrB 2   
                 5.7 
               
               
                   
                 ZnO 
                 4.0 
               
               
                   
                 SiO 2 Al 2 O 3   
                 5.1 
               
               
                   
                 SiO 2 ZrO 2   
                 4.5 
               
               
                   
                 CaOHfO 2   
                 3.3 
               
               
                   
                 Si 
                 2.6 
               
               
                   
                 SiO 2   
                 2.6 
               
               
                   
                 ZrW 2 O 8   
                 (−6) − (−9) 
               
               
                   
                 ZrMo 2 O 8   
                 −11 
               
               
                   
                 HfW 2 O 8   
                 −10 
               
               
                   
                 ZrV 2 O 7   
                   (−1) − (7.1) 
               
               
                   
                 ScW3O12 
                 −2.2 
               
               
                   
                 ReO 3   
                 (−0.5) − (−0.7) 
               
               
                   
                 LiAlSiO 4   
                 (−1) − (−6) 
               
               
                   
                 Mn 3 Cu 0.53 Ge 0.47 N 
                 −16 
               
               
                   
                 Mn 3 Zn 0.4 Sn 0.6 N 0.85 C 0.15   
                 −23 
               
               
                   
                 Mn 3 Zn 0.5 Sn 0.5 N 0.85 C 0.1 B 0.05   
                 −30 
               
               
                   
                 (HfMg)(WO 4 ) 
                 −2 
               
               
                   
                 Bi 0.95 La 0.05 NiO 3   
                 −82 
               
               
                   
                   
               
               
                   
                 Note: 
               
               
                   
                 CTE in Table 1 may vary with the structure, structure orientation, application temperature, pressure and the preparation conditions, for example, vacuum pressure, gas composition, substrate temperature and deposition technique. 
               
             
          
         
       
     
     The materials in Table 1 may be used in pure phases or as components in composite materials with tailored thermal expansion coefficients. The atomic ratio in the materials may vary slightly which may correspondingly vary the thermal expansion coefficient of the materials. For example, ZrW 2 O 8  may have varied atomic ratio which in general expressed ZrW x O y , in which the values of X and Y vary within a range. 
     Compounds belonging to the zirconium vanadate family have a general formula of AM 2 O 7 . When M=V, the A cation can be Zr and Hf. When M=As, the A cation can be Zr or Th. When M=P, the A cation can be Zr, Hf, Ti, U, Th, Pu, Ce, Mo, W, Re, Pb, Sn, Ge, or Si. The vanadate and phosphate compounds exist in a cubic structure in space group of Pa3 − . These compounds adopt a NaCl structure made up of AO 6  octahedra and M 2 O 7  units. 
     The materials of Table 1 may be prepared by vacuum deposition techniques such as chemical vapor deposition, sputtering, cathodic arc deposition, laser beam ablation, etc. While the materials of Table 1 present CTEs significantly lower than the CTE of sputtered alumina, these materials also have acceptable hardness and large optical band gaps from 3 to 6 eV, which make them wear-resistant and electrically insulating and, therefore, desirable selections for the trailing edge cap  114  to resist profile changes under the write cycle laser heat in HAMR drives. The materials for the trailing edge cap  114  are most appropriate when they also have a low intrinsic stress (compressive and tensile) relative to the transducer electronics so as to protect the electronics. Low intrinsic stress for the trailing edge cap materials of Table 1 can be obtained by regulating the substrate bias/temperature, deposition rate and gas pressure during vacuum deposition. 
     In another example embodiment, see  FIG. 2 , the trailing edge cap  114 , adjacent substrate  110 , is designed to incorporate multiple materials, such as those from Table 1. In this embodiment, the trailing edge cap is presented in a configuration where a first material  130  surrounds or encapsulates the area of highest heat, for example, around the read/write transducers (not shown) and the laser near-field transducer (not shown), is of the lowest CTE. A second material  132  surrounding or encapsulating the first material  130  may be of a slightly higher CTE, a third material  134  surrounding or encapsulating the second material may be of a still slightly higher CTS than material  132 , and so on. Any number of layers of materials may be used with the low CTE material increasing in CTE value from the area of highest heat within the slider out to the substrate  110 . The materials with a CTE approximating or greater than 7×10 −6 /° C. linear are nearest the substrate  110  while the materials of Table 1 with a CTE at or less than 5×10 −6 /° C. linear, (e.g., at or less than 3×10 −6 /° C. linear), are nearest the trailing edge  108 . 
     In another example embodiment, the material chosen for the trailing edge end cap  114  has a CTE comparable to that of the AlTiC slider body  110 , see  FIG. 3 . In this embodiment, the trailing edge end cap  114  is in a laminated configuration presenting layers, e.g.,  141 - 149 , whose CTE gradually decreases towards the extreme edge (layer  149 ). As carbides and nitrides possess good adhesion to one another, the material of the cap end layer (layer  141 ) can either be a carbide or nitride so as to bind well with the AlTiC substrate  110  of the slider body  100 ; the AlTiC substrate has ˜30 wt. % of carbide as TiC. Once again, the materials with a CTE approximating or greater than 7×10 −6 /° C. linear are nearest the substrate  110  while the materials of Table 1 with a CTE at or less than 5×10 −6 /° C. linear, e.g., at or less than 3×10 −6 /° C. linear, are nearest the trailing edge  108 . 
     In another example embodiment, represented again by  FIG. 1 , a configuration of the low CTE trailing edge cap  114 , such as those described above, is combined with a slider body substrate  110  of a low CTE. In this embodiment, the slider body substrate  110 , may include AlTiC or similar material having a significant thermal expansion tendency, is instead made of a material or materials having low CTEs so as to reach an optimal thermal compatibility with the trailing edge cap  114 . A low CTE edge cap  114  in combination with a low CTE slider body substrate  110  can altogether reduce the thermal profile changes for the whole head slider  100  under the write duty cycle laser heat in HAMR drives. Example slider body substrate  110  materials include SiC, ZrC, Si, metal oxide and carbide composites and have a CTE of 3×10 −6 /° C. linear or less. These materials also have high hardness and acceptable electrical conductivity. 
     Systems, devices or methods disclosed herein may include one or more of the features structures, methods, or combination thereof described herein. For example, a device or method may be implemented to include one or more of the features and/or processes above. It is intended that such device or method need not include all of the features and/or processes described herein, but may be implemented to include selected features and/or processes that provide useful structures and/or functionality. 
     Unless otherwise indicated, all numbers expressing feature sizes, amounts, and physical properties used in the specification and claims are to be understood as being modified in all instances by the term “about.” Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and attached claims are approximations that can vary depending upon the desired properties sought to be obtained by those skilled in the art utilizing the teachings disclosed herein. The use of numerical ranges by endpoints includes all numbers within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5) and any range within that range. 
     Various modifications and additions can be made to the disclosed embodiments discussed above. Accordingly, the scope of the present disclosure should not be limited by the particular embodiments described above, but should be defined only by the claims set forth below and equivalents thereof.