Abstract:
A slider is formed of an air bearing surface coated with a wear limiting coating that substantially limits surface wear of the air bearing surface encountered in proximity recording. The wear limiting coating is comprised of a wear inhibiting layer formed on the air bearing surface and a sacrificial layer formed on the wear inhibiting layer. The two coatings of the wear limiting coating have different mechanical properties so that the sacrificial layer is burnished, exposing the wear inhibiting layer. This design substantially limits the surface wear of the air bearing surface typically encountered in proximity recording, resulting in less debris accumulation, which could otherwise adversely affect the performance of the proximity recording head. This self-limiting burnishing action overcomes the flying height variation due to manufacturing tolerances and provides extremely small and uniform magnetic spacing, which greatly enhances the proximity recording. Moreover, the burnishing action also achieves an improved flying stability and a reduction in the altitude sensitivity.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is related to co-pending U.S. patent application Ser. No. 10/223,922, titled “Proximity Recording Air Bearing Design for a Data Storage System,” which is assigned to the same assignee as the present application, and which is incorporated herein by reference in its entirety. 
     FIELD OF INVENTION 
     The present invention relates in general to data storage systems such as disk drives, and it particularly relates to a thin film read/write head for use in such data storage systems. More specifically, the present invention provides a new sandwich layer of diamond-like carbon (DLC) overcoat for use in slider designs of proximity recording heads. The DLC layer design substantially limits the surface wear of the air bearing surface typically encountered in proximity recording, resulting in less debris accumulation which would otherwise adversely affect the performance of the proximity recording head. 
     BACKGROUND OF THE INVENTION 
     In a conventional magnetic storage system, a thin film magnetic head includes a read/write element mounted on a slider. The magnetic head is coupled to a rotary actuator magnet and a voice coil assembly by a suspension and an actuator arm positioned over a surface of a spinning magnetic disk. 
     In operation, a lift force is generated by the aerodynamic interaction between the magnetic head and the spinning magnetic disk. The lift force is opposed by equal and opposite spring forces applied by the suspension such that a predetermined flying height is maintained over a full radial stroke of the rotary actuator assembly above the surface of the spinning magnetic disk. The flying height is defined as the spacing between the surface of the spinning magnetic disk and the lowest point of the slider assembly. 
     One objective of the design of magnetic read/write heads is to obtain a very small flying height between the read/write element and the disk surface. By maintaining a flying height close to the disk, it is possible to record short wavelength or high frequency signals, thereby achieving high density and high storage data recording capacity. 
     The slider design incorporates an air bearing surface to control the aerodynamic interaction between the magnetic head and the spinning magnetic disk thereunder. Air bearing surface (ABS) sliders used in disk drives typically have a leading edge and a trailing edge. A thin film read/write element is formed at the trailing edge of the slider. 
     Generally, the sliders have tapered portions at the leading edge and longitudinal side rails that extend from the tapers to the trailing edge. The tapers may be shaped and of such length as to provide fast pressure buildup during takeoff of the slider from a rest position to a flying height relative to the disk with controlled pitch. The dimensions and shapes of the tapers and side rails are instrumental in determining the flying characteristics of the head. The side rail design determines the pressure generated at the ABS of the slider. In effect, the pressure distribution on the ABS contributes to the flying characteristics of the slider that include flying height, pitch, and roll of the read/write head relative to the rotating magnetic disk. 
     In a conventional magnetic media application, a magnetic recording disk includes a landing zone, which is defined as an annulus area of a width of about 0.2 inch located at the inner radius of the magnetic disk. The landing zone is a textured area and its sole function is to provide a surface upon which the slider comes to rest in between track seeks during a read/write operation. The surface of the landing zone typically is optimized to have a certain degree of roughness so as to prevent stiction between the slider and the disk and yet enable a fast take-off of the slider. 
     As the trend toward high capacity storage applications continues, smooth media applications have emerged to supplant conventional media applications with increasing acceptance due to a principal advantage of smooth media disks in offering a higher data storage capacity than conventional media disks. This advantage is afforded by the absence of the landing zone, which is reclaimed for increasing the data storage area of a magnetic disk. Hence, a smooth media disk is characterized by a finely polished surface in its entirety from the outer radius to the inner radius of the disk without a landing zone. 
     Accompanied with the emergence of smooth media disks, the current trend in the magnetic storage technology has also been to push the slider design toward a near zero flying height in order to reduce the magnetic spacing, thereby increasing the data recording capacity. This type of slider design is typically referred to as proximity or contact recording, which employs a contact pad concept, wherein a small pad is etched around the pole tip region. Furthermore, to attain high linear or areal density, such a slider design may include a giant magnetoresistive (GMR) read/write sensor. 
     In proximity recording, the air bearing surface (ABS) is typically designed to have high a pitch stiffness that causes the contact pad in the trailing edge region of the ABS, to which the read/write sensor is physically attached, to remain in actual contact with the highest asperities on the smooth media disk surface during the initial phase of operation. Because of this contact action, surface wear of the slider as well as the media disk takes place during this process, which is also referred to as burnishing. 
     Since the contact point is localized at the contact pad region, the pads burnishes continuously. The burnishing process gradually decelerates and eventually stops when the contact pad no longer encounters any asperities on the smooth media disk surface, thereby achieving a steady state clearance. Thereupon, the goal of the proximity recording is realized as the slider attains a near zero flying height and thereby reduce the magnetic spacing. Hence, the success of the proximity recording head depends on understanding and controlling the wear evolution of slider-disk interface. 
     Because of the surface contact with the magnetic storage disk made by the trailing edge region of the ABS, the surfaces of the magnetic storage disk and the ABS of the conventional slider experience a continual erosion or wear, thereby resulting in material loss from both the magnetic storage disk and the ABS. This material loss forms debris in the vicinity of the pole tip region of the read/write sensor. As the debris accumulates, the ability of the proximity recording head to register binary data onto the magnetic storage disk suffers a significant degradation due to an increase in spacing between the pole tip and the surface of the magnetic storage disk. The head is no longer flying, but is supported by the contamination. In general, the severity of the wear is controlled within the specified design tolerances by optimizing the tribology of the ABS material. The maximum wear is proportional to the initial interference height of the slider-disk interface. If the wear were not properly controlled, the burnishing would eventually expose the GMR read/write sensor to the ambient. Because of its susceptibility to atmospheric corrosion, the GMR read/write sensor may fail to achieve its functionality and proximity recording performance when exposed to the drive environment. 
     To address this concern in the slider design of a proximity recording head, presently an exemplified tribological design incorporates a conventional diamond-like carbon (DLC) protective pad onto the trailing edge region of the ABS wherein the read/write sensor is mounted. The conventional DLC protective pad is generally formed by a two-layer material comprising of an outer DLC layer disposed above an underlying silicon (Si) seed layer. The outer DLC layer is usually derived from ethylene as a precursor, hence also referred to as E-DLC. 
     While the conventional two-layer DLC pad may have in theory provided a satisfactory resolution of the foregoing concern, in practice it does have a serious deficiency that likely renders the goal of proximity recording unattainable. This deficiency lies in the fact that due to manufacturing tolerances, there exists a small deviation in the design flying height of the slider, which herein is referred to as sigma. The flying height sigma translates into a distribution of interference height, resulting in some sliders exposing to larger interference heights than others. Consequently, this presents a number of challenging problems to the conventional DLC pad. 
     Because the E-DLC layer of the conventional DLC pad would experience a varying degree of burnishing due to the flying height sigma, the proximity recording heads employing the conventional DLC pads thus cannot in general achieve uniform steady state clearance or magnetic spacing, thereby leading to a varying performance of such proximity recording heads. 
     Moreover, the inability to cope with the distribution of flying height sigma also increases the risk of a potential excessive wear of the E-DLC layer of the conventional contact DLC pad when the slider is flying closer to the magnetic disk surface than the average flying height. In some instances, the wear of the conventional contact DLC pad is so extensive that allows the read/write sensor to be exposed to the corrosive environment in which the proximity recording head operates. Once exposed, the read/write sensor becomes oxidized or corroded quite rapidly, thereby resulting in damage to the proximity recording head and consequently causing catastrophic failure of the magnetic disk drive. 
     In light of unresolved concerns with the conventional DLC protective pad employed in proximity recording applications, it is realized that there is an unfulfilled need for an improved DLC pad design for proximity recording that addresses the problems associated with the flying height sigma variation of the sliders in the proximity recording heads. Preferably, the improved DLC pad design should be insensitive to the flying height sigma in a manner that would allow the burnishing to achieve uniform steady state clearance and magnetic spacing in spite of the variation in the flying height. More importantly, the improved DLC pad design should be able to provide a complete protection of the read/write sensor during burnishing by limiting the wear process. These preferences, therefore, establish a goal for proximity recording that would enable the current advancement in high capacity magnetic storage applications to continue to progress. 
     SUMMARY OF THE INVENTION 
     The present invention can be regarded as a recording head comprising a read/write transducer and a slider having an air bearing surface. The air bearing surface includes a center pad and the center pad includes an aft strip that includes the read/write transducer. The aft strip also includes a protective layer. The protective layer includes a seed layer, a wear-limiting layer, and a sacrificial layer. The sacrificial layer includes diamond like carbon (DLC). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features of the present invention and the manner of attaining them, will become apparent, and the invention itself will be understood by reference to the following description and the accompanying drawings, wherein: 
         FIG. 1  is a fragmentary perspective view of a data storage system utilizing a read/write head of a conventional design or of the present invention; 
         FIG. 2  is a perspective view of a head gimbal assembly comprised of a suspension, and a slider to which the read/write head of  FIG. 1  is secured, for use in a head stack assembly; 
         FIG. 3  is a top view of the ABS of the slider of  FIG. 2  comprised of various patterned features which includes a trailing edge center pad; 
         FIG. 4  is an enlarged top view of the trailing edge center pad of the ABS of  FIG. 3  including a contact ABS pad, made according to the present invention; 
         FIG. 5  is a cross sectional view of the trailing edge center pad of  FIG. 4 ; 
         FIG. 6  is a schematic of a sandwich DLC process made according to the present invention; 
         FIG. 7  is an illustration of the relationship of the ABS slider of  FIG. 2  and the smooth media disk of  FIG. 1  before burnishing; and 
         FIG. 8  is an illustration of the relationship of the ABS slider of  FIG. 2  and the smooth media disk of  FIG. 1  after burnishing. 
     
    
    
     Similar numerals in the drawings refer to similar elements. It should be understood that the sizes of the different components in the figures might not be in exact proportion, and are shown for visual clarity and for the purpose of explanation. 
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  illustrates a disk drive  10  comprised of a head stack assembly  12  and a stack of spaced apart smooth media magnetic data storage disks or smooth media  14  that are rotatable about a common shaft  15 . The head stack assembly  12  is rotatable about an actuator axis  16  in the direction of the arrow C. The head stack assembly  12  includes a number of actuator arms, only three of which  18 A,  18 B,  18 C are illustrated, which extend into spacings between the disks  14 . 
     The head stack assembly  12  further includes an E-shaped block  19  and a magnetic rotor  20  attached to the block  19  in a position diametrically opposite to the actuator arms  18 A,  18 B,  18 C. The rotor  20  cooperates with a stator (not shown) for rotating in an arc about the actuator axis  16 . Energizing a coil of the rotor  20  with a direct current in one polarity or the reverse polarity causes the head stack assembly  12 , including the actuator arms  18 A,  18 B,  18 C, to rotate about the actuator axis  16  in a direction substantially radial to the disks  14 . 
     A head gimbal assembly (HGA)  28  is secured to each of the actuator arms, for instance  18 A. With reference to  FIG. 2 , the HGA  28  is comprised of a suspension  33  and a read/write head  35 . The suspension  33  includes a resilient load beam  36  and a flexure  40  to which the head  35  is secured. The head  35  is formed of either a slider  47  made according to the present invention secured to the free end of the load beam  36  by means of the flexure  40 , and a read/write element  50  supported by the slider  47 . The read/write element  50  is mounted at the trailing edge  55  of the slider  47  so that its forwardmost tip is generally flush with the ABS  58  of the slider. 
     With reference to  FIG. 3 , the ABS  58  of the slider  47  is generally formed of a rectangular shape bounded by an ABS leading edge  60 , an ABS trailing edge  62 , and two ABS sides  64  and  66 . 
     For convenience, two orthogonal axes are introduced in  FIG. 3  to aid the description of the slider  47 . A longitudinal axis  400  is parallel to the ABS sides  64  and  66  and bisects the ABS  58  to form a line of symmetry. A transverse axis  500  intersects with and is perpendicular to the longitudinal axis  400  at the center of the ABS  58 . 
     A patterned topology of varying width and depth is formed upon the surface of the ABS  58 . This patterned topology is designed to shape the aerodynamic pressure characteristic on the ABS  58  during proximity recording in order to achieve a desired lift force acting on the slider  47 . The patterned topology is further comprised of a number of specialized regions and features. In general, these specialized regions and features include a cavity region  68 , a patterned leading edge pad  70 , two oppositely disposed patterned side pads  72  and  74 , a plurality of supporting posts  76 , and a patterned trailing edge center pad  78 . In particular, the trailing edge center pad  78  incorporates a new sandwich DLC protective pad made according to the present invention to achieve uniform magnetic spacing and to protect the read/write element  50  by inhibiting surface wear of the ABS  58 . 
     With reference to  FIG. 3 , the cavity region  68  is comprised substantially of the surface of the ABS  58 , generally extending from the patterned leading edge pad  70  toward to ABS trailing edge  62 . The cavity region is formed by either reactive ion etching (RIE) or ion milling to a depth of 50 to 120 μin relative to the datum surface  80  of the ABS  58 . 
     With further reference to  FIG. 3 , the patterned leading edge pad  70  is further comprised of a shallow step region  82  and an ABS region  84 . The shallow step region  82  is generally formed of a polygonal shape having a plurality of sides to be described hereafter. A leading edge side  90  is formed on and extends nearly the length of the ABS leading edge  60 . Two sides  92  and  94  are disposed parallel to and slightly offset inwardly from the two ABS sides  64  and  66 . The sides  92  and  94  join with the leading edge side  90  at its two ends via small curved segments. Two angular sides  96  and  98  then join with the sides  92  and  94  at their other respective ends. A side  100  is disposed parallel to the leading edge side  90  and connects to the angular sides  96  and  98  via small curved segments to complete the polygon that defines the leading shallow step region  82  of the patterned leading edge pad  70 . 
     In a typical manufacturing sequence, the leading edge shallow step region  82  is formed by either reactive ion etching (RIE) or ion milling to a depth of approximately 4 to 10 microinches relative to the datum surface  80  of the ABS  58 . 
     With reference to  FIG. 3 , the ABS region  84  of the patterned leading edge pad  70  generally resembles a shape of the letter “C” having three identifiable areas: a center portion  110 , and two side rail portions  112  and  114 . As a reference, the surface of the ABS region  84  defines the datum surface  80  of the ABS  58 . 
     The center portion  110  of the ABS region  84  adjoins the leading edge shallow step region  82  along the two angular sides  96  and  98  and the side  100  that collectively define one side of the center portion  110 . A segmented side  116  defines the other side of the center portion  110 . Further, the segmented side  116  is generally shaped so as to form a trapezoidal notch area  118  in the center portion  110  of the ABS region  84 . 
     The two side rail portions  112  and  114  are oppositely disposed and connect to either end of the center portion  110 . The side rail portions  112  and  114  are generally formed of rectangular tabs that extend toward the ABS trailing edge  62  and are slightly offset inwardly from the ABS sides  64  and  66  of the ABS  58 . 
     The two oppositely disposed patterned side pads  72  and  74  are situated toward the trailing edge region of the ABS  58 . The patterned side pads  72  and  74  are generally of a rectangular shape with radius corners. Furthermore, the patterned side pads  72  and  74  are slightly offset inwardly from and extend parallel to the ABS sides  64  and  66  of the ABS  58 . 
     The patterned side pads  72  and  74  are further comprised of shallow step regions  140  and  142 , and ABS regions  144  and  146 , respectively. The shallow step regions  140  and  142  are generally of a trapezoidal shape with radius corners and are formed by etching. In an exemplary preferred embodiment, the shallow step regions  140  and  142  are etched to the same depth as that of the leading shallow step region  82 , though it should be understood that the shallow step regions  140  and  142  could be etched to a different depth. 
     The ABS regions  144  and  146  adjoin the shallow step regions  140  and  142 , respectively along two angular interfaces  150  and  152 . The ABS regions  144  and  146  generally feature a trapezoidal geometry with radius corners and are built up to the same height as the reference datum surface  80  of the ABS  58 . 
     A plurality of supporting posts  76  are positioned at various locations throughout the ABS  58 . With reference to  FIG. 3  of the preferred embodiment, the ABS  58  includes eight supporting posts  76 : two located in the leading edge shallow step region  82 , two in the leading edge ABS region  84 , and the remaining located in the cavity region  68 . 
     With reference to  FIG. 5  taken along the axis  400 , the supporting posts  76  are generally of a cylindrical shape that protrudes outwardly from the bottom surfaces of the leading shallow step region  82 , the leading edge ABS region  84 , and the cavity region  68 . According to a preferred embodiment, new sandwich diamond like carbon (DLC) protective pads  160  of the present invention are secured to, or formed on the tips of the supporting posts  76 . The posts  76  raise the DLC pads  160  of the present invention to a height above the reference datum surface  80  of the ABS  58 . 
     When the slider  47  is at a rest position on the smooth media disk  14 , the DLC pads  160  of the present invention come into contact with the smooth media disk  14  and provide a support to the ABS  58 , thereby preventing the ABS  58  from making contact with the surface of the disk  14  which would pose a potential damage to the read/write element  50 . Furthermore, the DLC pads  160  enable the slider  47  to take off rapidly for performing a track seek. 
     With reference to  FIGS. 3 and 4 , the trailing edge center pad  78  is generally formed of a polygonal shape and is disposed adjacent to the ABS trailing edge  62  of the ABS  58 . The trailing edge center pad  78  is further comprised of four specialized regions: a forward shallow step region  172 , a forward ABS region  174 , an aft shallow step region  176 , and a contact ABS pad  178 . In particular, the novelty of the present invention lies in the material and spatial design of the contact ABS pad  178 , which will be apparent in the subsequent description. 
     With reference to  FIG. 4 , the forward shallow step region  172  is generally a pentagon bounded by sides  180 ,  182 ,  184 ,  186 , and  188 . The sides  180  and  182  are joined by a radius corner and form an inverted V-shaped forward edge  190 . The side  188  is oppositely disposed from the inverted V-shaped forward edge  190  and defines an interface between the forward shallow step region  172  and the forward ABS region  174 . The two sides  184  and  186  are oppositely disposed about and nearly parallel to the longitudinal axis  400  of the ABS  58 . The two sides  184  and  186  join with the inverted V-shaped forward edge  190  and the interface side  188  to complete the definition of the forward shallow step region  172 . The depth of the forward step region relative to the reference datum surface  80  of the ABS  58  generally depends on various factors such as suspension gram load, rotation speed of the smooth media disk  14 , skew angle, etc. 
     The forward ABS region  174  adjoins the forward shallow step region  172  along the interface side  188  and generally is shaped as a trapezoid, which is bounded by the interface side  188 , and sides  200 ,  202 , and  204 . The sides  200  and  202  are extension of the sides  184  and  186  of the forward shallow step region  172 . The side  204  defines an interface between the forward ABS region  174  and the aft shallow step region  176 . 
     With reference to  FIG. 5  of the preferred embodiment, a new sandwich DLC pad  240  made according to the present invention is deposited onto the forward ABS region  174  to form a surface at the same level as the reference datum surface  80  of the ABS  58 . 
     With reference to  FIG. 4 , the aft shallow step region  176  of the trailing edge center pad  78  adjoins the forward ABS region  174  along the interface side  204  and is generally shaped as a trapezoid, which is bounded by the interface side  204 , two oppositely disposed angular sides  220  and  222 , and a side  224  parallel to the ABS trailing edge  62  of the ABS  58 . The side  224  also defines the interface between the aft shallow step region  176  and the contact ABS pad  178 . The depth of the aft shallow step region  176  typically ranges from 3 to 10 μin relative to the reference datum surface  80  of the ASS  58 , and the length of the aft shallow step region  176  along the axis  400  is generally about 2 to 4 mils. 
     The contact ABS pad  178  is located at the aftmost position on the ABS  58  and adjoins the aft shallow step region  176  along the interface side  224 . The contact ABS pad  178  is generally formed of a high-aspect-ratio rectangular shape, with the width along the transverse axis  500  much greater than the length along the longitudinal axis  400 . The length of the contact ABS pad  178  typically ranges from 0.5 to 1.0 mils. The rectangular shape of the thin contact ABS pad  178  is defined by the interface side  224 , two oppositely disposed sides  230  and  232 , and a side  234  that is parallel to the interface side  224 . The side  234  is slightly offset and parallel to the ABS trailing edge  62  of the ABS  58 . 
     The thin contact ABS pad  178  also contains the read/write element  50 , which is located along the longitudinal axis  400  and adjacent to the side  232 . In a preferred embodiment, a new sandwich DLC pad  240  made according to the present invention is deposited onto the ABS region  174  to embed the read/write element  50 . The top of the DLC pad  240  is formed at the same level as the reference datum surface  80  of the ABS  58 . 
     With reference to  FIG. 6 , the new sandwich DLC pads  160  on the supporting post  76 ,  240  on the forward ABS region  174 , and  240  on the contact ABS pad  178  are preferably made in accordance with a new sandwich DLC process  300  of the present invention. In a preferred embodiment, the sandwich DLC process  300  is comprised of three layers: a seed layer  302 , an intermediate cathodic-arc DLC wear inhibiting layer  304 , and an outer E-DLC sacrificial layer  306 . 
     The seed layer  302  is generally formed of silicon (Si) and is directly bonded to the underlying substrate of the slider  47 , which is typically made of alumina titanium carbide (Al 2 O 3 —TiC). The silicon seed layer  302  is typically about 10 angstroms in thickness. Due to a chemical compatibility, the presence of silicon in the seed layer  302  is necessary in order to promote the formation of the DLC material of the wear inhibiting layer  304 . 
     According to the present invention, the enabling technology of the sandwich DLC process  300  lies in the wear inhibiting layer  304  interposed between the seed layer  302  and the outer sacrificial E-DLC layer  306 . The DLC process is designed to produce a carbon graphite material that mimics the properties of diamond such as high mechanical strength and chemical inertness. The thickness of the wear inhibiting layer  304  is typically about 10 angstroms. 
     In general, the wear inhibiting layer  304  is made of a DLC material derived from a cathodic-arc process whereby an electric arc is generated to create a plasma, which discharges fine particles of carbon ions onto the seed layer  302  to form the wear inhibiting layer  304 . Owing to the cathodic-arc process, the DLC of the wear inhibiting layer possesses mechanical properties that are superior to DLC formed by other methods such as ethylene process. These superior mechanical properties afford the wear inhibiting layer  304  much greater mechanical strength and surface hardness, which are of paramount importance in controlling the surface wear of the slider  47  in the presence of the flying height sigma distribution during burnishing. 
     With reference to  FIG. 6 , the outer sacrificial layer  306  is formed on top of the wear inhibiting layer  304 . The outer sacrificial layer  306  is made of a DLC material having a thickness of about 20 angstroms. The DLC material is derived from ethylene as a precursor or other similar processes. The presence of the intermediate wear inhibiting layer  304  eliminates the need for a seed layer for the outer sacrificial layer  306 , since the material compatibility between the cathodic-arc DLC and the ethylene DLC is equivalent to that between silicon and ethylene DLC. 
     The ethylene DLC material of the outer sacrificial layer  306  generally is more compliant than the cathodic-arc DLC material of the wear inhibiting layer, as characterized by lower mechanical strength and surface hardness. Thus, during burnishing, the outer sacrificial layer  306  is allowed to wear, and also removes the asperities on the disk surface as a means to accommodate the flying height sigma distribution. 
     The functionality and advantages of the triple-layer sandwich DLC process  300  of the present invention will be further apparent as follows: 
     Referring now to  FIG. 7 , the surface of the smooth media disk  14  is characterized by three features: disk waviness  350 , disk roughness  352 , and local asperities  354 . The disk waviness  350  is an imaginary line that defines the average or mean surface of the disk  14 . Superimposed thereon is the disk roughness  352 , which is defined by the distribution of the local surface heights about the disk waviness  350 . A typical disk waviness is about 2 nm RMS (root mean squared) and a typical disk roughness is also about 2 nm RMS. The sum of the disk waviness  350  and disk roughness  352  is also called as disk avalanche. By definition, the local asperities  354  are isolated high points projected above the surface of the smooth media disk  14  that could be as high as 5 to 10 times the RMS roughness. 
     With reference to  FIG. 7 , during proximity recording, the surface of the smooth media disk  14  is spinning at a rapid rate of rotation. This rapid rotation generates a sufficient differential pressure between the top and bottom of the slider  47 , which is also the ABS  58 , to create a lift force  250  which causes the slider to tend to be airborne. A suspension gram load  252  equal to the lift force  250  is exerted downward onto the slider  47  to maintain the slider  47  in static equilibrium. Furthermore, the suspension gram load  252  and the lift force  250  are generally offset such that the suspension gram load  252  is closer to the ABS trailing edge  62  of the ABS  58  than the lift force  250 . This force offset results in a torque or moment acting in the counter clockwise direction to cause the slider  47  and hence the ABS  58  to pitch in the direction that raises the ABS leading edge  60  of the ABS  58  from the surface of the smooth media disk  14 . 
     Initially, the pitch rotation of the slider  47  causes the ABS trailing edge  62  of the ABS  58  to come into contact with the smooth media disk  14 . Due to a variation in the pitch stiffness as well as variations in the disk avalanche  356  and the local asperities  354 , the initial interference height  358  is subject to a certain statistical deviation or sigma. Thus, a portion of the sandwich DLC pad  240  of the present invention located on the contact ABS pad  178  is initially engaged with the surface of the smooth media disk  14  by a varying interference height  358 . 
     Due to the contact, both the surface of the smooth media disk  14  and the sacrificial layer  304  of the sandwich DLC pad  240  undergo a continuous burnishing, hence further reducing the surface roughness of the smooth media disk  14  and the surface of the ABS  58 . 
     With reference to  FIG. 8 , as the burnishing proceeds, the sacrificial layer  304  continues to diminish in thickness. Eventually, when the sacrificial layer  304  is completely worn through, the surface of the smooth media disk  14  then comes into contact with the wear inhibiting layer  302  of the sandwich DLC pad  240 . Owing to the high hardness of the cathodic-arc DLC material, the wear inhibiting layer  302  continues to burnish the surface of the smooth media disk  14 , while significantly resisting its own wear. Eventually, the local asperities  354  on the surface of the smooth media disk  14  are substantially reduced in size and a very small clearance  360  is consequently created, thus allowing the slider  47  to attain a uniform, near zero flying height without further burnishing the surfaces of the slider  47  and the smooth media disk  14 . The goal of achieving a uniform magnetic spacing in proximity recording is therefore realized with the introduction of the wear inhibiting layer  302  in the present invention. 
     Moreover, once the burnishing ceases, the wear inhibiting layer  302  is still retained on the surface of the sandwich DLC pad  240  in the pole tip region, thereby providing adequate corrosion protection of the read/write element  50  and increasing the reliability of the magnetic disk drive  10 . 
     It should be understood that the geometry, compositions, and dimensions of the elements described herein can be modified within the scope of the invention and are not intended to be the exclusive; rather, they can be modified within the scope of the invention. Other modifications can be made when implementing the invention for a particular environment.