Abstract:
A thin film, perpendicular write head for use with recording media with or without a soft under layer is disclosed. The present invention comprises an tapered auxiliary pole, situated below the main write pole and separated from the write pole by a lower non-magnetic gap. The auxiliary pole alleviates problems such as erasure after write, and cross track stray erasure fields, associated with operating conventionally designed perpendicular writes heads with media having no soft under layer.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to structures of thin film magnetic write heads. More specifically, the invention relates to perpendicular thin film write heads for recording on media with or without soft under layers. 
     2. Description of the Related Art 
     Single pole tip write heads having trailing shields or wrap around shields are currently used for perpendicular recording. The media upon which data is written (for example, the hard disk in a hard disk drive) comprises a layered structure having various, layers. The upper layers contain a hard magnetic data layer, followed by non-magnetic layers, followed by a magnetic soft under layer. For reasons concerning future media development, it is desirable to eliminate the soft under layer. For reasons of compatibility and continuity in development, it is also desirable that new head designs be operable both with and without the soft under layers. However, for prior art write heads of convention construction having, for example, wrap around shields, removing the soft under layer results in a large return flux at the wrap around shield adjacent to the write pole. In the down track direction, this results in a large negative field following the maximum positive field at the trailing edge of the pole. This may result in unwanted erasure of data being written to the media. Additionally, cross-track field profiles show an increase in stray erasure fields of adjacent tracks when no soft under layer is present. Currently, no prior art design is suitable for perpendicular recording at high density without the presence of a soft under layer. 
     What is needed is a perpendicular thin film head design that is suitable for recording on media with or without a soft under layer. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a thin film perpendicular head containing a write pole having an upper surface and a lower surface opposing the upper surface; a non-magnetic top gap in contact the said upper surface of the write pole; a non-magnetic bottom gap in contact with the lower surface of the write pole, the non-magnetic top gap having a thickness approximately equal to the thickness of the non-magnetic bottom gap; and, an auxiliary pole, having a top surface, the bottom gap in contact with the top surface of the auxiliary pole. 
     It is an object of the present invention to provide a thin film perpendicular head containing a write pole having an upper surface and a lower surface opposing the upper surface; a non-magnetic top gap in contact the said upper surface of the write pole; a non-magnetic bottom gap in contact with the lower surface of the write pole, the non-magnetic top gap having a thickness approximately equal to the thickness of the non-magnetic bottom gap; a lower return pole layer having a pedestal magnetically coupled to the lower return pole layer; and, an auxiliary pole, having a top surface and a base surface, the base surface in contact with the pedestal, the bottom gap in contact with the top surface of the auxiliary pole, the auxiliary pole situated between the write pole and the pedestal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be better understood when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings, wherein: 
         FIG. 1  (Prior Art) is a partial cross section view of a typical thin film perpendicular head structure; 
         FIG. 2  is a partial cross section view of a thin film perpendicular head, in accordance with an embodiment of the present invention; 
         FIG. 3  is a partial cross section expanded view of  FIG. 2 , in accordance with an embodiment of the present invention; 
         FIG. 4  is a partial, expanded ABS view of the embodiment of  FIG. 3 , in accordance with an embodiment of the present invention; 
         FIGS. 5   a - 5   d  are a detailed cross section views of auxiliary pole  204 , in accordance with embodiments of the present invention; 
         FIG. 6   a  is partial, ABS view of an auxiliary pole, in accordance with an alternative embodiment of the present invention; 
         FIG. 6   b  is a partial, cross section view of the embodiment of  FIG. 6   a , in accordance with an alternative embodiment of the present invention; and, 
         FIGS. 6   c ,  6   d  are partial, ABS views of auxiliary poles, in accordance with additional alternative embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  (Prior Art) is a partial, cross sectional view of a typical thin film perpendicular head  100 . The head comprises shield layers  102 ,  104 , MR read sensor  103 , shaping layer  110 , coil structures  108   a,b , main write pole  112 , lower return pole layer  106 , wrap around shield  114 , and upper return pole layer  116 . Alternatively, structure  114  may also be a trailing shield. Details of wrap around shields and trailing shields, as applied to perpendicular recording heads, can be found in, for example, US Patent Application Publications 2007/0146930, 2007/0115584, 2006/0174474, 2006/0044682, and 2007/0137027. 
       FIG. 2  is a partial cross section view  200  of a thin film perpendicular head, in accordance with an embodiment of the present invention. Notable features of this head that distinguish it from designs of the prior art are pedestal  202  and auxiliary pole  204 . Auxiliary pole  204  is magnetically coupled to pedestal  202 . Pedestal  202  is, in turn, magnetically coupled to lower return pole layer  106 . Both pedestal  202  and auxiliary pole  204  are comprised of suitable magnetic materials, similar to the composition of write pole  112 , or return pole layers  106 ,  116 , in accordance with information well known to those skilled in the art. Auxiliary pole  204  enables an additional leading edge flux return path, reducing the need for a soft under layer within the media, while maintaining the appropriate write field strength and field profile. Location of the auxiliary pole  204  at the leading edge provides a low reluctance flux return path for write pole  112 , which provides a write field of sufficient magnitude. Concentration of the return flux at the leading edge also reduces the problem of large erasure field following the write field, and cross track erasure fields that would be present in the conventional head design of  FIG. 1  (Prior Art) used with media lacking a soft under layer. An important aspect of the present invention is that it reduces the reliance of head design on media design. In the conventional head of  FIG. 1 , the distance of the write pole tip to the soft under layer is an important parameter, but this distance is dependent on head ABS to media dimensions as well as deposited film thickness dimensions of the media. As areal densities increase and dimensions are reduced, it is becoming harder to control these dimensions within acceptable tolerances. Removing or reducing the need for a soft under layer in the media reduces the importance of a variable that now can be controlled primarily by head design. 
       FIG. 3  is a partial cross section expanded view  300  of  FIG. 2 , in accordance with an embodiment of the present invention. Auxiliary pole  204  is separated from write pole  112  by lower gap layer  304 , which is comprised of a suitable non-magnetic material. Top gap  302  is the non-magnetic gap between the write pole  112  and shield  114 . Shield  114  may be a wrap around shield or trailing shield. The materials and thickness of gaps  302 ,  304  are similar. 
       FIG. 4  is a partial, expanded ABS view  400  of the embodiment of  FIG. 3 , in accordance with an embodiment of the present invention. This is a partial view of write pole  112 , auxiliary pole  204 , pedestal  202 , top gap  302 , side gaps  402 , and lower gap  304 , looking into the structure at the air bearing surface. Pedestal  204  is about as wide (in the cross track directions on either side of write pole  112 ) as shield  114  (not shown). The width of auxiliary pole  204  is approximately the same as the width of write pole  112 . As previously noted, the thickness of lower gap  304  is approximately the same as top gap  302 . Although lower gap  304  is illustrated as a continuous layer extending in the cross track direction on either side of auxiliary pole  204 , it shall be recognized that this layer may be localized to the region immediately above the auxiliary pole  204 , or that it may be comprised of non-magnetic material surrounding the auxiliary pole (and not a separate layer), in accordance with fabrication techniques well known to those in the art. What is important is that a non-magnetic gap of thickness similar to top gap  302 , be present between the top of auxiliary pole  204  and the lower boundary of write pole  112 . Auxiliary pole  204  is magnetically coupled to, pedestal  202 . This may be done through direct contact, or through a thin non-magnetic gap layer (not shown). 
       FIGS. 5   a - 5   d  are a detailed cross section views  500   a - 500   d  of auxiliary poles  204   a - 204   d , in accordance with embodiments of the present invention.  FIG. 5   a  illustrates a first embodiment of the present invention. Auxiliary pole  204   a  has a base surface of length  508 , a front surface defining the height  504 , and a tapered, trailing surface  510 . Auxiliary pole  204   a  has a top surface of length  502 , which is the portion of the boundary of auxiliary pole  204   a  in contact with lower gap layer  304 , length  502  being approximately equal to the throat height of shield  114 . The height  504  of auxiliary pole  204  is greater than two times the thickness of top gap  302 . Length  508  of the base surface is equal to the length  502  of the top surface plus height  504  divided by tan(angle  506 ). Angle  506  is between 5 and 75 degrees.  FIG. 5   b  illustrates a second embodiment  204   b  of the present invention. In this embodiment, trailing surface  512  is concave in shape. Angle  506  is determined by a line segment  510 ′ connecting the rearward boundary of the top surface with the rearward boundary of the base surface.  FIG. 5   c  illustrates a third embodiment  204   c  of the present invention, wherein trailing surface  514  is convex in shape. Angle  506  is determined by a line segment  510 ′ as described above.  FIG. 5   d  illustrates a fourth embodiment  204   d  of the present invention, wherein trailing surface  516  is stepped in shape. Angle  506  is determined by a line segment  510 ′, as previously described. All the forgoing embodiments of  FIGS. 5   a - 5   d , while having different trailing shapes, provide suitable functionality for the auxiliary pole. 
       FIG. 6   a  is partial, ABS view  600  of an auxiliary pole  610 , in accordance with an alternative embodiment of the present invention. In this embodiment, the auxiliary pole  204  of  FIGS. 2-5  is rotated about 90 degrees.  FIG. 6   b  is a partial, cross section view  601  of the embodiment of  FIG. 6   a . The thickness (or width) of auxiliary pole  610  is approximately equal to the throat height of shield  114 . Dimension  502  is approximately the width of write pole  112 . Angle  506  is as previously disclosed. 
       FIGS. 6   c ,  6   d  are partial, ABS views  602 ,  603  of auxiliary poles, in accordance with additional alternative embodiments of the present invention.  FIG. 6   c  illustrates auxiliary pole  604 , the embodiment of  FIGS. 6   a ,  6   b  rotated 180 degrees. Dimensions cited for the embodiment of  FIGS. 6   a ,  6   b  apply.  FIG. 6   d  is a further embodiment of the present invention auxiliary pole  606 , combining the geometries of the embodiments shown in  FIGS. 6   a - 6   c . Auxiliary pole  606  is symmetric about an axis perpendicular to the boundary with pedestal  202 , said axis proceeding though and bisecting write pole  112 . Angles at the base (the surface in contact with pedestal  202 ) of auxiliary pole  606  are equal, with values as disclosed for angle  506  of  FIGS. 5   a - 5   d . The top surface of auxiliary pole  606  in contact with lower gap  304  is approximately equal to the throat height of shield  114 . The two tapered, trailing surfaces may also have convex, concave, or stepped shapes as shown in embodiments of  FIGS. 5   b - d.    
     It should be noted that the embodiments of  FIGS. 6   a  and  6   c  can be rotated to any angle between the position illustrated and that of the embodiment of  FIGS. 2-4 . Although location at angles other than that shown in  FIGS. 2-4  and  6   a ,  6   c  may provide challenges for fabrication, and may be not as desirable, this does not, in anyway, detract from the fact that the function of the invention at these alternate locations is not diminished. 
     The present invention is not limited by the previous embodiments heretofore described. Rather, the scope of the present invention is to be defined by these descriptions taken together with the attached claims and their equivalents.