Abstract:
A magnetic write head provides a significant write field and minimal adjacent track erasure, and lends itself to improved manufacturability. The write head includes a pedestal throat height that defines a bottom pole, P 1 , and that is substantially recessed from the air bearing surface. The write head further includes a top pole, P 2 , that defines a nose that is closer to the air bearing surface than the pedestal zero throat. This design achieves a relatively high ratio of the off-track to on-track field. As an example, a 1:4 ratio could be achieved to significantly mitigate the erasure problem of the adjacent tracks resulting from magnetic flux saturation.

Description:
FIELD OF THE 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 relates to an enhanced design of a thin film, inductive type write head, also known as Pedestal Defined Zero Throat (PDZT) write head, with a substantial recession of the pedestal point (throat height) away from the air bearing surface (ABS) and a substantial extension of the top-pole flare point or nose toward the ABS. 
     BACKGROUND OF THE INVENTION 
     In a conventional magnetic storage system, a thin film magnetic head includes an inductive 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. 
     An exemplary magnetic head is illustrated in  FIGS. 1A ,  1 B,  2 A, and  2 B, and includes a thin film write head with a bottom pole (P 1 ) and a top pole (P 2 ). The bottom pole P 1  presents a pole tip height (also referred to as pole tip length) dimension commonly referred to as throat height (“TH”). In a finished write head, the throat height is measured between an air bearing surface (“ABS”), formed by lapping and polishing the pole tip, and a zero throat (“ZT”) level where the pole tip of the write head transitions to a back region. 
     The pole tip region is defined as the region between the ABS and the zero throat level. This pole tip region is also known as a pedestal, which is an extension of the bottom pole P 1 . 
     Similarly, the top pole P 2  has a pole tip height dimension commonly referred to as “nose length”. Typically in a conventional design, the nose length ranges from 1.5 to 3 μm. In a finished write head, the nose is defined as the region of the top pole P 2  between the ABS and a “flare position” where the pole tip transitions to a back region. 
     Each of the bottom pole P 1  and top pole P 2  has a pole tip located in its respective pole tip region. The tip regions of the poles P 1  and P 2  are separated by a magnetic write (or recording) gap, which is a thin layer of nonmagnetic material. In a conventional design, the nose of the top pole P 2  typically extends to an aft position relative to the throat height from the ABS, which ranges from 0.5 to 1.5 μm. Whereas the width of the pole tip of the top pole P 2  is defined by the track width of a typical magnetic storage medium, the width of the pedestal region can span several tracks. 
     The current trend in magnetic storage industries has been toward a high track density design of magnetic storage media. This increase in track density enables a larger storage capacity than that of the prior design. In order to maintain the industry standard interface, magnetic storage devices increasingly rely on reducing track width as a means to increase the track density without significantly altering the geometry of the storage media. 
     A significant concern with the current design of magnetic write heads is the ability to write digital data to the target track without adversely affecting the data quality of the adjacent tracks that are in close proximity due to the high track density design of the magnetic storage media. 
     This task has been particularly difficult to accomplish with the current magnetic write head design. In particular, during a write operation, significant magnetic flux leakage from the top pole P 2  enters the bottom pole P 1  through the pedestal region, thereby causing a magnetic saturation in the pedestal. This flux leakage is a consequence of the longer nose of the top pole P 2  relative to the throat height of the bottom pole P 1 . 
     With further reference to  FIGS. 2A and 2B , the magnetic saturation in the pedestal region concentrates predominantly in sloped areas of the pedestal referred to as E 1  and E 2 , that are positioned on either side of a platform of the pedestal and parallel to the ABS. 
     Since areas E 1  and E 2  cover a number of data tracks contiguous to a target track, there is a tendency for the data in these adjacent tracks to be disturbed by the magnetic flux saturation in the surrounding region. In some instances, up to 6 adjacent tracks on either side of the target track can be adversely affected. In a worst case scenario, the data disturbances can result in a total erasure of data in the adjacent tracks after several repetitive write operations. 
     The ratio of the adjacent or off-track field to the target or on-track field in this instance is approximately about 1:3 for a typical conventional magnetic write head design. It would therefore be desirable for this ratio to be increased in order to minimize the magnetic flux saturation in the adjacent tracks. 
     SUMMARY OF THE INVENTION 
     It is a feature of the present invention to provide a magnetic write head architecture for a larger write field and less adjacent track erasure than a conventional write head design. The simplicity in the present architecture lends itself to improved manufacturability, while effectively reducing the magnetic flux saturation problem. 
     Among other new features, the present write head architecture incorporates the following two novel design elements:
         1. The pedestal point or throat height of the bottom pole P 1  is substantially recessed from the ABS; and   2. The nose length of the top pole P 2  is substantially reduced so as to cause the flare point of the top pole P 2  to move closer to the ABS.       

     In order to achieve these two design features, a new geometry of the pedestal region is conceived for the new write head architecture of the present invention, to achieve a relatively high ratio of the off-track to on-track field. Specifically, a desirable ratio of 1:4 is possible with this design, thereby significantly mitigating the erasure problem of the adjacent tracks resulting from magnetic flux saturation. 
    
    
     
       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. 1A  is a cross-sectional, side elevational view of a conventional write head; 
         FIG. 1B  is top plan view of the write head of  FIG. 1A ; 
         FIG. 2A  is an enlarged, partial, perspective view of a pedestal region of the write head of  FIGS. 1A and 1B ; 
         FIG. 2B  is a side elevational view of the pedestal region of  FIG. 2A ; 
         FIG. 3  is a fragmentary perspective view of a data storage system utilizing a read/write head according to the present invention; 
         FIG. 4  is a perspective view of a head gimbal assembly comprised of a suspension, and a slider to which the read/write head of  FIG. 3  is secured, for use in a head stack assembly; 
         FIG. 5  is an enlarged perspective view of a thin film read/write element, forming part of the read/write head of  FIGS. 3 and 4 , and made according to the present invention; 
         FIG. 6A  is a cross-sectional view of the write head of  FIG. 5 , with the read element not shown, taken along line  6 - 6 ; 
         FIG. 6B  is top plan view of the write head of  FIG. 6A ; 
         FIG. 7A  is an enlarged, partial, perspective view of a pedestal region and a pole tip regions of a bottom pole P 1  and top pole P 2  of the write head of  FIGS. 5 ,  6 A, and  6 B; 
         FIG. 7B  is a side elevational view of the pedestal and pole tip regions of  FIG. 7A ; 
         FIG. 7C  is a front view of the pedestal and pole tip regions of  FIGS. 7A and 7B ; 
         FIG. 7D  is a top plan view of the pedestal region of the bottom pole P 1 ; 
         FIG. 7E  is an enlarged, partial, perspective view of the pedestal region of  FIGS. 7A through 7D ; and 
         FIG. 8  is an ABS view of the read/write head of the present invention. 
     
    
    
     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 THE PREFERRED EMBODIMENTS 
       FIGS. 3 through 8  illustrate the main features of the present invention.  FIG. 3  illustrates a disk drive  10  comprised of a head stack assembly  12  and a stack of spaced apart magnetic data storage disks or 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. 4 , 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 a slider  47  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 slider  47  can be any conventional or available slider. 
     In the exemplary embodiment of  FIG. 4 , 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 of the slider  47 . In another embodiment according to the present invention more than one read/write element  50  can be secured to the trailing edge  55  or other side(s) of the slider  47 . 
     With reference to  FIG. 5 , the read/write element  50  integrates a write section  60  and a read section  61 . The read section  61  is formed of a first shield layer (Shield  1 )  80  preferably made of a material that is both magnetically soft and thermally conductive. An insulating layer  82  is formed over substantially the entire surface of the first shield layer  80  to define a non-magnetic, transducing read gap  87 . The read section  61  is also comprised of a read sensor  83  formed within the insulation layer  82 . The read sensor  83  can be any suitable sensor, including but not limited to a magnetoresistive (MR) element, a giant magnetoresistive (GMR) element, a spin valve, or a Current In the Plane mode (CIP) sensor. 
     The read section  61  is also comprised of a second shield layer (Shield  2 )  85  that is made of a magnetically soft and thermally conductive material, which may be similar or equivalent to that of the first shield layer  80 . The second shield layer  85  is formed over substantially the entire surface of the insulating layer  82 . 
     The write head  60  is comprised of a first pole layer or bottom pole P 1  (also referenced by the numeral  90 ) that extends from the ABS to a back gap  91  behind the last turn  92  of a write coil  94 . The bottom pole P 1  or  90  is made of magnetically soft material, and may be for example purpose only, similar or equivalent to that of the first shield layer  80 . In the exemplary embodiment of  FIG. 5 , the second shield layer  85  and the first pole layer P 1 ,  90  are illustrated as being the same layer. It should however be clear that according to another embodiment of the present invention, the second shield layer  85  and the first pole layer P 1 ,  90  can be independently formed and separated by an insulation layer therebetween. 
     With further reference to  FIGS. 6A ,  6 B, and  7 A through  7 E, a pedestal  120  is formed on the first pole layer  90 , from the ABS to a back face  125  that defines a zero throat level with extreme accuracy. The pedestal  120  is surrounded by a pedestal region. The zero throat level lies in a well defined plane that is generally parallel to the plane of the ABS, which in turn is co-planar with the forward face  140  of the pedestal  120 . In a preferred embodiment, the pedestal  120  extends only to the zero throat  125  with a pedestal height (“ph”) ranging from approximately 1.55 to approximately 3 μm. The pedestal height is also referred to herein as “the throat height.” 
     The write coil  94  includes a plurality of multi-turn conductive coil elements (or conductors)  94 A, only a few of which are illustrated also form part of the write section  60 . The coil elements  94 A are formed within an insulating layer  95 . The write coil  94  can have two, four or more turns as required, typically 6 to 12 turns, to generate the desired write field. According to another embodiment of the present invention, the write coil  94  may have a multi-layer design, with typically 1, 2, or more layers. 
     A second pole layer or top pole P 2  (also referenced by the numeral  96 ) is made of a magnetically soft material that can be similar or equivalent to that of the first shield layer  80  and the first pole layer  85 . The second pole layer  96  is formed over, and is separated from the pedestal  120 , to define a write gap  98  therewith. The thickness of the second pole layer  96  can be substantially the same as, or similar to that of the first shield layer  80 . The write gap  98  can be filled with a material similar or equivalent to that of the insulating layer  82 . 
     With further reference to  FIG. 5 , a write circuit (not shown) is connected to the write coil  94 , and, during a write mode, it sends an electrical current I W  to induce a flux flow through the write gap  98 . Changes in the flux flow across the write gap  98  produce the alternating magnetic orientations of magnetized regions or domains in the disk  14  during a write operation. 
     With reference to  FIG. 6B , the second pole layer  96  includes an angled (or sloped) back edge or flare  115  along which the second pole layer  96  is connected to a top (or upper) yoke  104  ( FIG. 7C ). The portion of the second pole layer  96  from the ABS to a forwardmost edge  130  of the flare  115  is referred to as a nose  135 . The forwardmost edge  130  is also known as the flare position. 
     In a preferred embodiment, the nose length (“NL”) typically ranges between approximately 0.6 and approximately 1.3 μm. The width of the nose (“nw”) is preferably made to be precisely equal to the desired track width. One feature of the present invention is that the nose length NL is shorter than the length of the nose in the conventional design of  FIG. 1B . 
     According to the present invention, the nose length NL is approximately less than half the zero throat height (“ZTH”) also referred to as zero pedestal height, where in a finished write head, the zero throat height is measured between the ABS and the back face  125  that defines the zero throat level. This relationship can be expressed by the following equation: 
     
       
         
           
             
               
                 N 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 L 
               
               
                 Z 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 T 
                 ⁢ 
                 
                     
                 
                 ⁢ 
                 H 
               
             
             ≺ 
             
               1 
               / 
               2. 
             
           
         
       
     
     Referring to the conventional design illustrated in  FIGS. 1A and 1B , the typical nose length (“TNL”) is more than the length of the throat height TH of the pedestal. This relationship can be expressed by the following equation: 
                 T   ⁢           ⁢   N   ⁢           ⁢   L       T   ⁢           ⁢   H       ≻     1   /   2.           
It is this change in ratio that simultaneously allows for an increased on-track field, and a reduced adjacent-track field.
 
     Another important feature of the present invention is that the zero throat  125  of the pedestal  120  is substantially made distally farther from the ABS than that of the conventional design illustrated in  FIGS. 1A and 1B . This feature is significant in that while increasing the zero throat height ZTH could cause a reduction in both the off-track and on-track fields, moving the flare position  130  closer to the ABS substantially improves the on-track field that more than adequately compensates for the reduced on-track field from the increased zero throat height, without affecting the reduced off-track field. With this arrangement, a ratio of off-track to on-track field of 1:4 can thus be attained, effectuating a significant reduction in the magnetic flux saturation problem that could otherwise result in incidental erasure or loss of data in the adjacent tracks. 
     Referring now to  FIGS. 7A ,  7 B,  7 C,  7 D, and  7 E, the pedestal  120  is formed as a multi-faceted block situated on top of the first pole layer  90 . The height of the pedestal  120  (“PH”) is substantially greater than the typical pedestal height (“TPH”) of the conventional design of  FIGS. 2A and 2B . This feature moves the back of the pedestal  120  farther from the ABS, for allowing the magnetic saturation region to help reduce the magnetic flux leakage entering from the second pole layer  96 . 
     The upper facet or surface pedestal  120  includes two similar, rectangular, flat faces  155 ,  160  that are generally parallel to the first pole layer  90 . Each of these flat faces  155 ,  160  extends integrally into a corresponding upwardly sloping faces  165 ,  170 . In the embodiment illustrated in  FIGS. 7A through 7E  and  8 , the flat face  155  extends into the sloping face  165 , while the flat face  160  extends into the sloping face  170 . 
     The two sloping faces  165 ,  170  extend into a raised platform  200  that is specially shaped according to the present invention. The platform  200  is peripherally bounded by the forward face  140 ; two vertical side walls  210 ,  240  ( FIG. 7D ) that extend into two angled side walls  220 ,  230 , respectively; a top face  250 ; and the back face  125 . 
     The forward face  140  is typically coplanar with the ABS and is generally parallel to the back face  125 . The top face  250  is flat, and lies in a plane that is normal to the ABS. 
     The two vertical side walls  210 ,  240  are generally similar in shape. Each of the two vertical side walls  210  and  240  lies in a plane that is normal to the ABS and to the top face  250 . The side wall  210  extends integrally into the angled side wall  220 , and forms an angle α therewith. Similarly, the side wall  240  extends integrally into the angle side wall  230  and forms an angle α therewith. The angle α can range between approximately 10 to 45 degrees. In a preferred embodiment, the angle α is approximately 35 degrees. The height (“ph”) of the platform  200  ( FIG. 7E ), that is the height of the side wall  210  can range between approximately 0.15 μm and approximately 0.45 μm. 
     The platform  200  is generally coaligned with the nose  135 , so that the width (“pw”) of the platform  200  corresponds to the width (“nw”) of the nose  135  and also to the desired track width. 
     Having described the various sides of the platform  200 , it can be said to be comprised of two sections: a forward section  300  and a rearward section  350  ( FIG. 7E ). The forward section  300  is defined by the forward face  140 , the top face  250 , and the two side walls  210  and  240 . The forward section  300  has a generally rectangular cross-section along the plane of the top face  250 . 
     The rearward section  350  ( FIG. 7E ) is defined by the two angled side walls  220 ,  230 , the top face  250 , and the back face  125 . The rearward section, which is also referred to herein as a flared section, is generally trapezoidally shaped along the plane of the top face  250 . 
     The rearward positioning of the flared section  350  relative to the ABS presents a significant feature of the present invention in that the flared section  350  diverts the magnetic flux leakage entering from the second pole layer  96  away from the pedestal region, thereby abating the magnetic saturation problem in the edge areas  145  and  150 . The two angled side walls  220 ,  230  conform to (i.e., coplanar with the corresponding sides of) the flare  115  ( FIG. 6B ), in order to minimize the magnetic flux interference effect. 
     The pedestal structure  120  of the present invention and its location relative to the flare position  130  of the second pole layer  96  allows the magnetization to move back from the pole tip region of the write head  60 , thereby reducing the concentration of the off-track field on the edge areas  145  and  150  while enhancing the on-track field. 
     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.