Abstract:
A perpendicular recording head for use with magnetic recording medium has an improved structure permitting an unusually narrow trackwidth to be defined by a simple, cost-efficient manufacturing process. The main pole and opposing pole of the recording head are deposited on the side of the slider, so that the trackwidth is controlled by the thickness of material deposited to form the main pole. The dimension of the main pole along the direction of the track is not critical for permitting a recording head of the present invention to record at high densities. The opposing pole may be located in front of, to the side of, or behind the main pole.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application No. 60/167,936 and No. 60/167,952, both filed Nov. 29, 1999. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This application relates to perpendicular recording heads for use with magnetic recording media. More specifically, the invention relates to a perpendicular recording head wherein the layers of material comprising the recording head&#39;s components are deposited perpendicular to the recording medium&#39;s direction of travel. 
     2. Description of the Related Art 
     Perpendicular recording heads for use with magnetic recording media have been proposed to overcome the storage density limitations of longitudinal recording heads. Perpendicular recording heads typically include a pair of magnetically coupled poles, with the main pole having a significantly smaller surface area than the opposing pole. A coil is located adjacent to the main pole for inducing a magnetic field in the main pole. Magnetic recording media used with perpendicular recording heads typically includes an upper layer having alternating magnetically hard tracks and nonmagnetized transitions. A magnetically soft lower layer will typically be located adjacent to the recording layer, opposite the recording head. Due to the difference in surface area between the main pole and opposing pole, and the magnetic flux passing through the soft underlayer between the two poles, the orientation of magnetic flux within the recording tracks will be oriented perpendicular to the recording medium, and parallel to the magnetic flux within the main pole. 
     The recording density is inversely proportional to the width of the magnetically hard recording tracks. The width of these tracks is a function of the width of the recording heads main pole. Presently available main poles are currently produced through lithographic processes. The width of the main pole is therefore limited by the resolution of these lithographic processes. 
     Therefore, there is a need for an improved perpendicular recording head having a main pole with a narrow width. Further, there is a need for a perpendicular recording head having a main pole capable of being produced by processes having better resolution than lithography. Additionally, there is a need for a method of manufacturing a perpendicular recording head capable of producing main poles for use with narrow trackwidths. 
     SUMMARY OF THE INVENTION 
     The present invention is a perpendicular recording head for use with magnetic recording media. Although not limited to such use, such a recording head is particularly useful for fixed or hard drives for computers. 
     A perpendicular recording head of the present invention includes a main pole magnetically coupled to an opposing pole. The bottom surface of the opposing pole has a significantly greater surface area than the bottom surface of the main pole. An electrically conductive coil passes adjacent to the main pole for inducing magnetic flux within the main pole. The direction of magnetic flux within the main pole may be reversed by reversing the direction of current flow through the coil. 
     A preferred and suggested method of making a perpendicular recording head of the present invention involves depositing the material to form the main pole and opposing pole on the side of a slider. The material is thereby deposited perpendicular to the recording medium&#39;s direction of travel, and parallel to the recording medium&#39;s trackwidth. Therefore, the trackwidth is a function of the amount of material deposited on the side of the slider to form the main pole. The increased area of the opposing pole relative to the main pole may be achieved by depositing the opposing pole over a longer portion of the slider, or by depositing a thicker layer of material to form the opposing pole. 
     Alternatively, the perpendicular recording head may be manufactured by first depositing the opposing pole on the side of the slider, followed by depositing a magnetically permeable joint between the main and opposing poles, a coil, and lastly, a main pole. As before, the trackwidth is defined by the thickness of material deposited to form the main pole. The opposing pole may be given a greater bottom surface area than the main pole by either increasing the length of the slider on which the opposing pole is deposited, or by increasing the thickness of material deposited to form the opposing pole. 
     A typical magnetic recording medium for use in conjunction with a perpendicular recording head includes an upper layer having a plurality of magnetically permeable tracks separated by nonmagnetized transitions, and a magnetically permeable lower level. The lower level is magnetically soft relative to the tracks. 
     The recording head is separated from the magnetic recording medium by a distance known as the flying height. The magnetic recording medium is moved past the recording head so that the recording head follows the tracks of the magnetic recording medium, with the main pole oriented parallel to the tracks and perpendicular to the trackwidth. Current is passed through the coil to create magnetic flux within the main pole. The magnetic flux will pass from the main pole through the track, into the lower layer, and across to the opposite pole. The flux will thereby cause the magnetic fields in the tracks to align with the magnetic flux of the main pole. Changing the direction of electric current changes the direction of the flux created by the recording head and therefore the magnetic fields within the magnetic recording medium. Because the surface area of the opposing pole is significantly greater than the surface area of the main pole, the magnetic flux density passing through the opposing pole will be significantly lower than the magnetic flux density passing through the main pole. Therefore, only the magnetic flux immediately adjacent to the bottom surface of the main pole will affect the orientation of the magnetic fields within the tracks. A binary “zero” is recorded by maintaining a constant direction of magnetic flux through the main pole, and a binary “one” is recorded by changing the direction of magnetic flux through the main pole. 
     When writing to a magnetic recording medium, the rate of decrease of magnetic field strength with increasing distance from the trailing edge of the main pole determines the recording density possible within a given track. This decrease in magnetic field strength determines the ability of the main pole to effect the orientation of magnetic flux within that portion of the track directly below the main pole, without effecting the orientation of magnetic flux in the track sector immediately behind the sector for which a write operation is being performed. Therefore, the dimension of the main pole parallel to the track does not effect recording density, and is only critical for ensuring that the surface area of the main pole&#39;s bottom is significantly less than the area of the opposing pole&#39;s bottom surface. Because the only critical dimension of the main pole is controlled by the thickness of material deposited to form the main pole, the method of producing such a perpendicular recording head is particularly simple and efficient. Additionally, because magnetic flux immediately adjacent to the opposing pole&#39;s bottom surface is not sufficiently strong to effect the orientation of magnetic flux within the magnetic recording medium, the position of the opposing pole relative to the main pole is limited only by the need to maintain a flow of magnetic flux between the main and opposing poles of the perpendicular recording head, and the soft underlayer of the magnetic recording medium. The opposing pole may therefore be located in front of, to the side of, or behind the main pole. 
     It is therefore an aspect of the present invention to provide a perpendicular recording head for use with magnetic recording media having a narrower main pole than can be produced by presently used lithography methods. 
     It is another aspect of the present invention to provide a perpendicular recording head wherein the width of the main pole is determined by the process of depositing the material forming the main pole to the appropriate thickness. 
     It is a further aspect of the present invention to provide a perpendicular recording head wherein the width of the main pole is the only critical dimension for maximizing recording density. 
     It is another aspect of the present invention to provide a perpendicular recording head wherein the main pole and opposing pole are deposited directly onto a side of a slider. 
     It is a further aspect of the present invention to provide a perpendicular recording head wherein changing the direction of current through the coil causes the orientation of magnetic flux within the opposing pole&#39;s end joint between the opposing poles to rotate from one orientation, through its default orientation, and to the opposing orientation, instead of flipping from one orientation to the other. 
     It is a further aspect of the present invention to provide a method of manufacturing a perpendicular recording head that is simpler and less expensive than presently used manufacturing methods. 
     These and other aspects of the present invention will become more apparent through the following description and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a top view of a typical hard disc drive for a computer for which the present invention may be used, illustrating the disc drive with its upper housing portion removed. 
     FIG. 2 is a partially sectioned, partially schematic, perspective view of an embodiment of a perpendicular recording head according to the present invention. 
     FIG. 3 is a partially schematic, perspective view of another embodiment of a perpendicular recording head according to the present invention. 
     FIG. 4 is a partially schematic, perspective view of an alternative embodiment of a perpendicular recording head of the present invention. 
     FIG. 5 is a graph representing magnetic field strength as a function of distance from the center of the main pole in the direction parallel to the trackwidth. 
     FIG. 6 is a graph indicating magnetic field strength as a function of distance from the trailing end of the main pole in the direction parallel to the tracks. 
     Like reference numbers denote like elements throughout the drawings. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The preferred embodiments of the present invention are perpendicular recording heads for use with magnetic recording media. As will be explained in detail below, the trackwidth of the recording media used with these recording heads is defined by the thickness of the material deposited to form the main pole. Perpendicular recording head main poles typically have thickness measured in a direction parallel to the tracks of the magnetic recording media, and a width defined perpendicular to the tracks of the magnetic recording medium. Deposited materials typically have a thickness measured from the surface of the substrate to the surface of the deposited material. Therefore, the width of the main pole corresponds to the thickness of the desired material. As used herein, recording head is defined as a head adapted for read and/or write operations, although the present invention is specifically directed towards the write portion of the recording head. 
     The invention will most commonly be used within a fixed disc drive  10  for computers, one of which is illustrated in FIG.  1 . The fixed disc drive  10  includes a housing  12  (with the upper portion removed and the lower portion visible in this view for maximum clarity) dimensioned and configured to contain and locate the various components of the disc drive  10 . The disc drive  10  includes a spindle motor  14  for rotating at least one magnetic storage medium  16  within the housing, in this case a magnetic disc. At least one arm  18  is contained within the housing  12 , with each arm  18  having a first end  20  with a perpendicular recording head or slider  22 , and a second end  24  pivotally mounted to a bearing  26 . An actuator motor  28 , such as a movable coil DC motor, is located at the arm&#39;s second end  24 , pivoting the arm  18  to position the head  22  over a desired sector of the disc  16 . The actuator motor  28  is regulated by controller which is not shown and which is well known. 
     The features of the write portion of a perpendicular recording head  22  and corresponding magnetic storage disc  16  are best illustrated in FIGS. 2-4. The perpendicular recording head  22  includes means for concentrating magnetic flux onto a small surface area of magnetic recording medium, here a magnetically permeable main pole  30 , oriented substantially perpendicular to the magnetic recording medium  16 , and having a tip  32 . The tip  32  includes a bottom surface  34 . The top  36  of the main pole  30  is preferably magnetically coupled to a joint  38 . An opposing pole  40  is also magnetically coupled to the joint  38 , opposite the main pole  30 . The opposing pole  40  includes a bottom surface  42 , having a surface area significantly larger than the surface are of the bottom surface  34  of the main pole  30 . An electrically conductive coil  44  is located adjacent to the main pole  30 , and is dimensioned and configured to induce a magnetic flux in the main pole  30 . The main pole  30  and opposing pole  40  of the present invention are secured to the side  46  of a slider  48  within the head  22 . The slider  48  is well-known in the art of hard or fixed disks to be that portion of the perpendicular recording head  22  being dimensioned and configured to utilize airflow created by the rotating disk  16  to maintain a flying height A above the surface of the disk  16 . For purposes of this description, the side  46  of the slider  48  is defined as any surface on a slider  48  substantially parallel to the direction of travel of the magnetic recording medium  16 . A side  46  may therefore include a surface located between other layers of the perpendicular recording head  22 , or any substrate that may be secured between the slider  48  and the poles  30 , 40 . 
     One preferred embodiment of the recording head  22  is illustrated in FIG.  2 . This embodiment of the recording head  22  includes a main pole  30  and opposing pole  40  which are both deposited directly on the side  46  of the substrate  48 . In this embodiment, the thickness A of the main pole  30  may be substantially equal to the thickness B of the opposing pole  40 . The surface area of the bottom  42  of opposing pole  40  is made larger than the surface area of the bottom  34  of the main pole  30  by making the opposing pole&#39;s length D significantly greater than the main pole&#39;s length C. 
     An alternative preferred embodiment is illustrated in FIG.  3 . Like the embodiment of FIG. 2, this perpendicular recording head  22  is also made by plating both the main pole  30  and opposing pole  40  directly on the side  46  of the slider  48 . However, the thickness B of the opposing pole  40  and the thickness E of the joint  38  are both significantly larger than the thickness A of the main pole  30 . This difference in thickness is accomplished by merely depositing additional material to form the joint  38  and/or opposing pole  40 . 
     A second alternative preferred embodiment of the perpendicular recording head  22  is illustrated in FIG.  4 . This embodiment of the recording head  22  is made by first depositing the opposing pole  40  onto the side  46  of slider  48 . Next, the joint  38  is deposited onto the opposing pole  40 . Lastly, the main pole  30  is deposited onto the joint  38 . Within this embodiment, the length D of the opposing pole  40  and length C of the main pole  30  may be substantially identical. The surface area of the bottom surface  42  of opposing pole  40  is preferably made larger than the surface area of the bottom surface  34  of the main pole  30  by making the opposing pole&#39;s thickness B significantly larger than the main pole&#39;s thickness A. Although this embodiment is illustrated with the opposing pole  40  directly secured to the side  46 , a perpendicular recording head of this embodiment could easily be reversed. Explained differently, the main pole  30  may be directly deposited on the side  46 , with the joint  38  deposited on the main pole  30 , followed by depositing opposing pole  40  on the joint  38 . As long as a first pole (either the main pole  30  or opposing pole  40 ) is secured to the side  46 , and a second pole (the remaining pole from among main pole  30  and opposing pole  40 ) is provided, the width A of main pole  30  will be substantially parallel to the width of track  52  (described below). 
     Referring back to FIG. 2, a magnetic storage medium  16 , here a magnetic disc, for use with a perpendicular recording head  22  is illustrated. The disc  16  includes an upper layer  50  having a plurality of magnetically permeable tracks  52 , which are divided into sectors, with each sector having several different magnetic fields within the magnetically permeable material (not shown and well understood). The tracks  52  are separated by nonmagnetized transitions  54 . The disc  16  also includes a magnetically permeable lower layer  56 , which is magnetically soft relative to the tracks  52 . In use, the disc  16  will be separated from the tip  32  of the main pole  30  by a flying height F. The flying height F is sufficiently small so that a high concentration of flux from the main pole  30  will pass through the track  52 , but sufficiently large to prevent damage to disc  16  from contact with the recording head  22 . 
     Recording is accomplished by rotating the disc  16  relative to the recording head  22  so that the recording head  22  is located above the appropriate sectors of the tracks  52 . As recording progresses, the disc  16  will move past the recording head  22  in the direction of the arrow G. Current will be supplied to the coil  44 , thereby inducing a magnetic field within the main pole  30 . The greatest concentration of flux from this magnetic field will pass from the tip  32  of the main pole  30  through the track  52  directly under the main pole  30  on which recording is being carried out, the lower layer  56 , through a different sector of a track  52  directly under the opposing pole  40 , through the opposing pole  40  and joint  38 , and finally forming a complete loop back through the top  36  of the main pole  30 . A a portion of a sector of the track  52  passes under the main pole  30 , the orientation of its magnetic field will correspond to the orientation of the magnetic field of the main pole  30 , which will be perpendicular to the disc  16 . As the main pole passes over the disc  16 , the direction of current passing through the coil  44  will remain constant when a binary “0” is being recording, thereby creating consistent orientation of the magnetic field within the track  52 . The current passing through the coil  46  will reverse directions when a binary “1” is being recorded, thereby changing the orientation of a magnetic field within the track  52 . The opposing pole  40  does not affect the magnetic fields within the upper layer  50  because the large surface area of the bottom surface  42  of the opposing pole  40  relative to the small surface area of the bottom surface  34  of the main pole  30  results in a significantly lower flux concentration through the opposing pole  40  than through the main pole  30 . 
     The recording density possible with a perpendicular recording head is primarily dependent upon the main pole&#39;s width A. With a perpendicular recording head  22  of the present invention, the width A corresponds to the thickness of magnetically permeable material deposited to form the main pole  30 . Therefore, the width A, and resulting trackwidth of the magnetic recording medium, is controlled by a material deposition process. When presently available perpendicular recording heads are made, the width A is typically controlled by a lithography process. A main pole made by lithography typically cannot be made narrower than 300 nm. By controlling the width A using a material deposition process such as sputtering instead of lithography, the width A can be made significantly narrower. 
     FIG. 5 illustrates how a main pole  30  of the present invention permits a narrow trackwidth to be used. FIG. 5 illustrates the magnetic field as a function of distance from the center of the main pole  30  in the direction parallel to the trackwidth. Distance from the center of the main pole  30  in the direction parallel to the trackwidth is shown on the X axis of the graph, as reference number  60 . Field strength is illustrated on the Y axis  62 . This graph illustrates that a main pole  30  having a width A of 50 nm at a height 30 nm above the lower layer  56  will produce a strong magnetic field within that portion of a sector of a track  52  directly underneath the main pole  30 . At the same time, the magnetic field strength drops off rapidly with increasing distance from the main pole  30 , preventing the main pole  30  from influencing the magnetic fields within neighboring tracks. This rapid drop off and magnetic field strength is illustrated at reference number  64 . For this reason, a main pole  30  of the present invention permits the use of trackwidth significantly narrower than those possible with presently available perpendicular recording heads. 
     The length C of the main pole  30  does not have an effect on the recording density permitted by a recording head  22  of the present invention. The main pole  30  works on the principle of “trailing edge” writing. The recording density permitted within any given track is therefore a function of the decrease in magnetic field strength from the main pole  30  with increasing distance along the track from the trailing edge  58  of main pole  30 . An increase in the rate of decrease of field strength as a function of distance from the trailing edge  58  permits the sectors within the track  52  to be closer together, without the risk of a write operation performed on one sector affecting the orientation of the magnetic field in the immediately preceding sector. FIG. 6 illustrates magnetic field strength as a function of distance from the trailing edge  58  of main pole  30 . Distance from the trailing edge of main pole  30  is indicated on the X axis by reference number  66 . Field strength is indicated on the Y axis by reference number  68 . Because the orientation of magnetic flux within the main pole  30  as the trailing edge  58  (the last portion of the main pole  30  that the sector will pass underneath) is what will ultimately determine the orientation of magnetic flux within that sector, the rapid decrease in magnetic field strength with increasing distance from the trailing edge  58 , as indicated at reference number  70 , illustrates that a high recording density within each track  52  can be used. 
     Referring back to FIGS. 2-4, an additional advantage of the specific embodiment of FIG. 4 is illustrated. The magnetically permeable material forming the main pole  30 , joint  38 , and opposing pole  40  will typically be given a default magnetic polarization parallel to the magnetic recording medium during manufacture. A typical direction for this default polarization is illustrated by arrow H. When current is applied to the coil  44 , magnetic flux within the joint  38  will be oriented in either the direction of arrow I or the direction of arrow J, depending on the direction of current through the coil  44 . In the embodiments of the perpendicular recording head illustrated in FIGS. 2 and 3, given the opposing pole  40  and main pole  30  a default magnetic polarization H, parallel to the magnetic recording medium  16  requires that the orientation of the default magnetic polarization H be parallel with one possible flux orientation during write operations, an anti-parallel to the other possible flux orientation during write operations. Therefore, when the direction of current through the coil  44  changes, the orientation of magnetic flux within the joint  38  must “flip” from the orientation of arrow I to the orientation of arrow J, or vise versa. Within the perpendicular recording head of FIG. 4, however, the default magnetic polarization H may be oriented in a direction which is both parallel to the magnetic recording medium  16 , and perpendicular to the possible magnetic flux orientations I and J when current flows through the coil  44 . Therefore, when the current direction within the coil  44  changes, the orientation of magnetic flux through the joint  38  will not “flip” from the orientation of arrow I to the orientation of arrow J, or vise versa. Instead, the orientation of magnetic flux through the joint  38  will “rotate” from the orientation of arrow I, through the orientation of arrow H, to the orientation of arrow J, or vise versa. This is believed to prevent electromagnetic “noise”. 
     While a specific embodiment of the invention has been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the appended claims and any and all equivalence thereof.