Abstract:
A magnetic write head for magnetic data recording that incorporates a novel magnetic oscillation generator stricture that sets up a magnetic oscillation in the magnetic media for improving writing and that also narrows the write width and reduces adjacent track interference by suppressing writing in regions outside of the desired data track. The magnetic oscillation generating structure includes a centrally disposed magnetic assist element that generates an oscillating magnetic field that oscillates in a direction that will assist the write pole in writing to the magnetic medium. The magnetic oscillation generating structure also includes first and second magnetic non-assist elements at either side of the assist element. The non-assist elements generate a magnetic field that oscillates in a second direction that is opposite to the first direction, which counteracts the magnetic write assist from the centrally disposed magnetic assist element and acts to suppress writing in these side regions.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to magnetic data recording, and more particularly to a magnetic recording head that uses a novel magnetic microwave element for both write assist and also suppression of adjacent track interference. 
       BACKGROUND OF THE INVENTION 
       [0002]    The heart of a computer&#39;s long term memory is an assembly that is referred to as a magnetic disk drive. The magnetic disk drive includes a rotating magnetic disk, write and read heads that are suspended by a suspension arm adjacent to a surface of the rotating magnetic disk and an actuator that swings the suspension arm to place the read and write heads over selected circular tracks on the rotating disk. The read and write heads are directly located on a slider that has an air bearing surface (ABS). The suspension arm biases the slider toward the surface of the disk, and when the disk rotates, air adjacent to the disk moves along with the surface of the disk. The slider flies over the surface of the disk on a cushion of this moving air. When the slider rides on the air bearing, the write and read heads are employed for writing magnetic transitions to and reading magnetic transitions from the rotating disk. The read and write heads are connected to processing circuitry that operates according to a computer program to implement the writing and reading functions. 
         [0003]    The write head can include a magnetic write pole and a magnetic return pole, the write pole having a much smaller cross section at the ABS than the return pole. The magnetic write pole and return pole are magnetically connected with one another at a region removed from the ABS. An electrically conductive write coil induces a magnetic flux through the write coil. This results in a magnetic write field being emitted toward the adjacent magnetic medium, the write field being substantially perpendicular to the surface of the medium (although it can be canted somewhat, such as by a trailing shield located near the write pole). The magnetic write field locally magnetizes the medium and then travels through the medium and returns to the write head at the location of the return pole where it is sufficiently spread out and weak that it does not erase previously recorded bits of data. 
         [0004]    A magnetoresistive sensor such as a GMR or TMR sensor can be employed for sensing magnetic fields from the rotating magnetic disk. The sensor includes a nonmagnetic conductive layer, or barrier layer, sandwiched between first and second ferromagnetic layers, referred to as a pinned layer and a free layer. First and second leads are connected to the sensor for conducting a sense current therethrough. The magnetization of the pinned layer is pinned perpendicular to the air bearing surface (ABS) and the magnetic moment of the free layer is located parallel to the ABS, but free to rotate in response to external magnetic fields. The magnetization of the pinned layer is typically pinned by exchange coupling with an antiferromagnetic layer. 
         [0005]    When the magnetizations of the pinned and free layers are parallel with respect to one another, scattering is minimal and when the magnetizations of the pinned and free layer are antiparallel, scattering is maximized. Changes in scattering alter the resistance of the spin valve sensor in proportion to cos θ, where θ is the angle between the magnetizations of the pinned and free layers. In a read mode the resistance of the spin valve sensor changes proportionally to the magnitudes of the magnetic fields from the rotating disk. When a sense current is conducted through the spin valve sensor, resistance changes cause potential changes that are detected and processed as playback signals. 
         [0006]    At very small bit size and high data density it becomes ever more difficult to write a stable magnetic bit on the magnetic media while also avoiding adjacent track interference. In order for the recorded magnetic bit to remain stable at very small bit sizes the magnetic coercivity of the media must be increased. However, this increased magnetic coercivity of the magnetic medium also requires a corresponding increase in field strength to record to the medium. However, as the size of the write pole shrinks (to generate the necessarily small recording bit) it becomes even harder to produce a strong enough field to record to the media. One method that has been proposed to overcome this obstacle has been to locally heat the media near the write pole, thereby temporarily lowering the coercivity of the media. This method has been referred to as thermally assisted recording. However, when locally heating the media sufficiently to allow recording of the bit, other adjacent tracks are inadvertently heated as well, which can lead to the erasure of or interference with adjacent data tracks, a problem that is especially problematic when the spacing between the data tracks in decreased in order to increase data density. Therefore, there remains a need for a technique for improving writeability at high data density, while also suppressing adjacent track interference. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention provides a magnetic write head for magnetic data recording that includes, a magnetic write pole having first and second sides and having a width defined by a distance between the first and second sides and a magnetic oscillation generator adjacent to the magnetic write pole. The magnetic oscillation generator further comprises, a centrally disposed magnetic assist element configured to generate an oscillating magnetic field that assists with magnetic data writing; and first and second magnetic non-assist elements each configured to generate an oscillating magnetic field that does not assist with magnetic data writing, the centrally disposed magnetic assist element being located between the first and second magnetic non-assist elements. 
         [0008]    A magnetic oscillation from a magnetic oscillation generator can assist in writing to a magnetic media by setting up a magnetic resonance in the magnetic media that temporarily reduces the magnetic resonance of the magnetic media, making it easier for a magnetic write field from the write pole to magnetically switch the media. However, increasing the ability to write to the media is not the only concern in a magnetic data recording system. It is also important that the adjacent track not be inadvertently affected by the write head. 
         [0009]    The present invention advantageously improves writing in a desired narrow write region while also suppressing writing in regions outside of this narrow region. The centrally disposed assist element sets up a magnetization in a first direction that is designed to assist writing. The non-assist elements on either side of the assist element generate an oscillation in an opposite direction that counteracts the oscillation from the assist element in the side regions to suppress the oscillation assist in the side regions, thereby preventing adjacent track interference and effectively narrowing the track width and increasing data density. 
         [0010]    These and other features and advantages of the invention will be apparent upon reading of the following detailed description of preferred embodiments taken in conjunction with the Figures in which like reference numerals indicate like elements throughout. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    For a fuller understanding of the nature and advantages of this invention, as well as the preferred mode of use, reference should be made to the following detailed description read in conjunction with the accompanying drawings which are not to scale. 
           [0012]      FIG. 1  is a schematic illustration of a disk drive system in which the invention might be embodied; 
           [0013]      FIG. 2  is an ABS view of a slider, taken from line  2 - 2  of  FIG. 1 , illustrating the location of a magnetic head thereon; 
           [0014]      FIG. 3  is a side view of a magnetic head, taken from line  3 - 3  of  FIG. 2  and rotated 90 degrees counterclockwise, of a magnetic head according to an embodiment of the present invention; 
           [0015]      FIG. 4  is an enlarged side view of a portion of the write head of  FIG. 3  shown rotated 90 counterclockwise; 
           [0016]      FIG. 5  is an ABS view of the portion of the write head shown in  FIG. 4 ; and 
           [0017]      FIGS. 6   a  and  6   b  are schematic ABS views of a magnetic write head according to an alternate embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0018]    The following description is of the best embodiments presently contemplated for carrying out this invention. This description is made for the purpose of illustrating the general principles of this invention and is not meant to limit the inventive concepts claimed herein. 
         [0019]    Referring now to  FIG. 1 , there is shown a disk drive  100  embodying this invention. As shown in  FIG. 1 , at least one rotatable magnetic disk  112  is supported on a spindle  114  and rotated by a disk drive motor  118 . The magnetic recording on each disk is in the form of annular patterns of concentric data tracks (not shown) on the magnetic disk  112 . 
         [0020]    At least one slider  113  is positioned near the magnetic disk  112 , each slider  113  supporting one or more magnetic head assemblies  121 . As the magnetic disk rotates, slider  113  moves radially in and out over the disk surface  122  so that the magnetic head assembly  121  may access different tracks of the magnetic disk where desired data are written. Each slider  113  is attached to an actuator arm  119  by way of a suspension  115 . The suspension  115  provides a slight spring force which biases slider  113  against the disk surface  122 . Each actuator arm  119  is attached to an actuator means  127 . The actuator means  127  as shown in  FIG. 1  may be a voice coil motor (VCM). The VCM comprises a coil movable within a fixed magnetic field, the direction and speed of the coil movements being controlled by the motor current signals supplied by controller  129 . 
         [0021]    During operation of the disk storage system, the rotation of the magnetic disk  112  generates an air bearing between the slider  113  and the disk surface  122  which exerts an upward force or lift on the slider. The air bearing thus counter-balances the slight spring force of suspension  115  and supports slider  113  off and slightly above the disk surface by a small, substantially constant spacing during normal operation. 
         [0022]    The various components of the disk storage system are controlled in operation by control signals generated by control unit  129 , such as access control signals and internal clock signals. Typically, the control unit  129  comprises logic control circuits, storage means and a microprocessor. The control unit  129  generates control signals to control various system operations such as drive motor control signals on line  123  and head position and seek control signals on line  128 . The control signals on line  128  provide the desired current profiles to optimally move and position slider  113  to the desired data track on disk  112 . Write and read signals are communicated to and from write and read heads  121  by way of recording channel  125 . 
         [0023]    With reference to  FIG. 2 , the orientation of the magnetic head  121  in a slider  113  can be seen in more detail.  FIG. 2  is an ABS view of the slider  113 , and as can be seen the magnetic head including an inductive write head and a read sensor, is located at a trailing edge of the slider. The above description of a typical magnetic disk storage system, and the accompanying illustration of  FIG. 1  are for representation purposes only. It should be apparent that disk storage systems may contain a large number of disks and actuators, and each actuator may support a number of sliders. 
         [0024]      FIG. 3  is a side cross sectional view of a magnetic write head  300  that can be constructed by a method of the present invention. The write head  300  includes a magnetic write pole  302  and a magnetic return pole  304 . The magnetic write pole  302  can be connected with a magnetic shaping layer  306  that helps to conduct magnetic flux to the tip of the write pole  302 . The write pole  302  and shaping layer  306  can be connected with the magnetic return pole  304  by a magnetic back gap structure  308 . A non-magnetic, electrically conductive write coil  310  passes between the return pole  304  and the write pole and shaping layer  302 ,  306 , and may also pass above the write pole and shaping layer  302 ,  306 . The write coil  310  can be encased in a non-magnetic, electrically insulating material  312 , which can be a material such as alumina and/or hard baked photoresist. When an electrical current flows through the write coil  310 , a magnetic field is induced around the coil  310  that results in a magnetic flux flowing through the return pole  304 , back gap layer  308 , shaping layer  306  and write pole  302 . This results in a write field being emitted from the tip of the write pole  302 . This strong, highly concentrated write field locally magnetizes a magnetic top layer  314  of the magnetic media  112 . The magnetic field then travels through a soft magnetic under-layer  316  of the magnetic media before returning to the return pole  304 , where it is sufficiently spread out and weak that it does not erase the previously recorded bit of data. The write head  300  can also include a magnetic pedestal  305 , at the ABS that acts as a shield to prevent stray fields, such as those from the write coil  310  from reaching the magnetic medium  112 . 
         [0025]    The write head  300  also includes a trailing magnetic shield  318 , located at the air bearing surface (ABS) and separated from the write pole  302  by a magnetic oscillation generator  320  that provides a magnetic oscillation for improved writing as will be described in greater detail herein below. A non-magnetic gap layer  321  is also provided to ensure that the trailing magnetic shield  318  is magnetically separated from the write pole  302 . The non-magnetic trailing gap layer  321  can be constructed of a material such as alumina. The trailing magnetic shield  318  can be connected with the other magnetic structures at the back of the write head  300  by a trailing magnetic pole  322 . The trailing shield  318  increases the write field gradient for improved writing. 
         [0026]    One way to increase data density is to increase the number of data tracks per inch (TPI), also referred to as track pitch, which requires narrowing the magnetic recording width. TO narrow the magnetic recording width, the width of the write pole  302  must be reduced, but this also results in a reduced magnetic write field, making such a reduction in width (or increase in TPI) difficult. In addition, since the main pole has a complex structure, a reduced magnetic write pole width leads to increased fabrication errors and increases the number of scrapped heads that do not have the desired small width. 
         [0027]    One way to improve writeability is to use an oscillating magnetic field generator within the write head that can excite a magnetic resonance, and induce the magnetization reversal of the magnetic recording medium. Such an oscillating magnetic field temporarily reduces the magnetic anisotropy of the magnetic medium, allowing for easier writing, even with a smaller write pole and reduces write field. Such a system can be referred to as micro-wave assisted writing, because the frequency of oscillation of the assisting oscillating magnetic field is preferably in the microwave range. However, a problem that arises with the use of such systems the width of the magnetic field from the write pole is large compared to the assist width and adjacent tracks of data can be erased. 
         [0028]    The present invention however overcomes this, providing a microwave assisted recording system that advantageously reduces track width while improving writeabilty and also decreasing adjacent track interference.  FIG. 4  shows an enlarged view of the pole tip portion of the structure of  FIG. 3 , the view being rotated 90 counterclockwise from that of  FIG. 3 .  FIG. 3  shows a portion of the write pole  302  and trailing shield  318  and the magnetic oscillation generator  320  sandwiched there-between. The magnetic oscillation generator uses a spin torque oscillation effect to generate a magnetic field  402  that oscillates in a precessional manner as shown. In order to produce this oscillating magnetic field  402 , the oscillation generator  320  includes a magnetic spin rectifying layer  404 , a field generation layer  406  and a magnetic zone control layer  408 . The spin rectifying layer  404  and the magnetic zone control layer  408  each have magnetizations  410 ,  412  that are pinned in a desired direction as shown in  FIG. 4 . This pinning can be a current induced pinning or could be generated by exchange coupling with a layer of antiferromagnetic material (not shown). A magnetic interlayer  414  is sandwiched between the spin rectifying layer  404  and the field generating layer  406 . 
         [0029]    Electrically conductive leads  416 ,  418  are also provided at either end of the oscillation generator  320  to provide an electrical current to flow through the generator  320  to induce the magnetic oscillation  402 . In addition, electrically insulating layers  420 ,  422  separate the rest of the magnetic oscillation generator  320  from the write pole  302  and shield  318 . When an electrical current flows through the oscillation generator  320 , electrons passing through the magnetically pinned spin rectifying layer  404  and the magnetic interlayer  414  they become polarized. These polarized electrons interact with the magnetic material of the field generation layer  406  to generate the magnetic oscillation  402  when in the presence of an external magnetic field such as from the write pole  302 . 
         [0030]      FIG. 5  shows a view of a portion of the head  300  as seen from the ABS. In this ABS view it can be seen that the magnetic oscillation generator includes a plurality of elements. At the center is an assist element  502 . At right and left sides of the assist element, are first and second non-assist elements  504 ,  506 , which are separated from the center element  502  by insulation layers  501 ,  503 . The central assist element  502  is configured so as to generate an oscillating magnetic field that assists writing to the magnetic medium  112  ( FIG. 4 ). Whereas the first and second non-assist elements  504 ,  506  are configured to generate an oscillating magnetic field that is oscillates in a direction opposite to that of the assist element  502 . This is achieved by configuring the elements  502 ,  504 ,  506  such that current flowing through the outer elements  506 ,  504  flows in an opposite direction to that of the inner element  502 . By way of example, as shown schematically in  FIG. 5 , a power source  508  is connected with leads  416   a,    418   a  of element  506 . Leads  514   a,    514   b,    514   c,    514   d  connect the elements  506 ,  502 ,  504  in such a manner as to cause a current flow  512   a,    512   c  through the elements  506 ,  504  that is opposite to the current flow  512   b  through the center element  502 . 
         [0031]    As seen in  FIG. 5 , the outer elements  504 ,  506  preferably extend laterally slightly beyond the edges of the write pole  302 , whereas the center element  502  has a width that is significantly smaller than the width of the write pole  302 . By reversing the polarity of the current (or voltage) across the elements  506 ,  504  relative to that of the element  504 , the rotation of the magnetic oscillation (e.g. clockwise vs. counter-clockwise) is also reversed. In this way, the outer elements  504 ,  506  counteract the writing assistance from the center element  502 , thereby greatly reducing the write width and preventing adjacent track interference. This allows the writing assistance of the magnetic oscillations to be employed while also preventing adjacent track interference. 
         [0032]    With reference now to  FIGS. 6   a  and  6   b , another embodiment of the invention allows the center of writing of a write pole to be shifted relative to a write pole center. This can be useful in compensating for skew when the slider on which the write head is formed is at an extreme inner or outer location on a write head. For example,  FIG. 6   a  shows a head portion that has a plurality of magnetic oscillation generator elements  604   a - f  (greater than three elements). The detailed structures of the elements  604   a - f  are not shown in  FIGS. 6   a  and  6   b  for purposes of clarity, but it should be understood that the elements  604   a - f  can include the various layers similar to the elements  502 ,  504 ,  506  of  FIG. 5  or similar to the oscillation generator  320  of  FIG. 4 . For purposes of illustration six elements  604  are shown. However, this is by way of example as some other number of elements greater than three could be used. 
         [0033]    As with the previously described embodiment, the magnetic oscillation generators are preferably located adjacent to the trailing edge of the write pole  302 . The elements  604  are connected with circuitry  606  that is configured to deliver a voltage or current to the elements  604   a - f  in such a manner that the direction of current flow through each element can be switched relative to the others. For example in the structure of  FIG. 6   a  the circuitry applies a voltage or current to the elements such that elements  604   c,    604   d  have a current flow  608  in a first direction that will result in the elements  604   c,    604   d  generating a magnetic writing assisting oscillation. On the other hand, the circuitry  604  is supplying a current or power to the elements  604   a,    604   b,    604   e,    604   f  so that these elements have a current flow  610  that flows in an opposite direction that does not assist writing. In the embodiment shown in  FIG. 6   a  the assisting elements  604   c,    604   d  are centrally located over the write pole  302 . Therefore, the magnetic writing will be focused on center of the write pole  302 . This is represented graphically in  FIG. 6   a , where the curve  6 . 12  represents the field strength as measured along a radial of the disk and the dashed line  614  represents the center of the write pole  302 . 
         [0034]    As those skilled in the art will appreciate however, as the slider moves to extreme inner or outer portions of the disk the slider (and write head) will be at an as a result of skew. This skew angle can affect writing, and it would be desirable to adjust the center of focus of the writing, relative to the write pole  302  in order to compensate for this skew. The present invention allows for such compensation as can be seen in  FIG. 6   b . In  FIG. 6   b , the elements  604   d  and  604   e  have their currents  608  flowing in a direction that is oriented to cause the elements  604   d  and  604   e  to generate an oscillating magnetic field that is oriented to assist writing. Elements  604   a,    604   b,    604   c  and  604   f  have their currents flowing in an opposite direction (indicated by arrows  610 ) so that the generated oscillating magnetic fields from these elements do no assist recording. As can be seen then, the assist is offset from center. This can be seen in the graph at the right of  FIG. 6   b  where the curve  616  is offset from the center of the write pole  302 , which is represented by dashed line  614 . 
         [0035]    While various embodiments have been described, it should be understood that they have been presented by way of example only, and not limitation. Other embodiments falling within the scope of the invention may also become apparent to those skilled in the art. Thus, the breadth and scope of the invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.