Abstract:
A magnetic recording head with thermal fly height control, wherein the heating element is configured to eliminate magnetic field effects on the writing pole, which would cause otherwise cause non-symmetric writing or pole erasure. Non-symmetric writing is a phenomenon wherein magnetic writing favors one direction over another, thereby causing a timing shift in recorded data. The pole erasure is a phenomenon wherein the erasure would occur even without write current. The heating element can be formed as a plurality of electrically conductive layers separated by a non-magnetic, electrically insulating layer such as alumina. The electrically conductive layers are configured so that current flows in opposite directions through each of the electrically conductive layers such that any magnetic field generated by the current flow through one electrically conductive layer is cancelled out by a magnetic field from another electrically conductive layer.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to magnetic data recording and more particularly to a thermally assisted fly height control magnetic recording head that eliminates heating element induced magnetic field effects on the write pole, thereby reducing non-symmetric writing or data erasure. 
       BACKGROUND 
       [0002]    At the heart of a computer 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 a media facing surface (MFS). The suspension arm biases the slider into contact with the surface of the disk when the disk is not rotating, but when the disk rotates air is swirled by the rotating disk. When the slider rides on the air bearing, the write and read heads are employed for writing magnetic impressions to and reading magnetic impressions 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 includes at least one coil, a write pole and one or more return poles. When current flows through the coil, a resulting magnetic field causes a magnetic flux to flow through the coil, which results in a magnetic write field emitting from the tip of the write pole. This magnetic field is sufficiently strong that it locally magnetizes a portion of the adjacent magnetic media, thereby recording a bit of data. The write field then, travels through a magnetically soft under-layer of the magnetic medium to return to the return pole of the write head. 
         [0004]    A magnetoresistive sensor such as a Giant Magnetoresistive (GMR) sensor or a Tunnel Junction Magnetoresistive (TMR) sensor can be employed to read a magnetic signal from the magnetic media. The magnetoresistive sensor has an electrical resistance that changes in response to an external magnetic field. This change in electrical resistance can be detected by processing circuitry in order to read magnetic data from the magnetic media. 
       SUMMARY 
       [0005]    A magnetic recording head is provided that includes a magnetic write element, a magnetic read element and a thermal heating element. The thermal heating element includes a plurality of electrically conducive layers separated by an electrically insulating layer, the electrically conductive layers being configured such that electrical current flows through the electrically conductive layers in opposite directions. 
         [0006]    For example, the thermal heating element can include first and second electrically conductive layers with a layer of electrically insulating material sandwiched between them. The first and second electrically conductive layers can be electrically connected with one another at one end, for example by a connection stud. Electrical lead pads can be connected with each of the electrically conductive layers at a second end, opposite the connection stud, for providing an electrical current to the thermal heating element. 
         [0007]    At least one of the electrically conductive layers can be a material that is chosen to produce Joule heating when an electrical current passes through it. By forming the first and second electrically conductive layers such that current flows in opposite directions, any magnetomotive force produced by one electrically conductive layer will advantageously be cancelled out by a magnetomotive force from the other electrically conductive layer. 
         [0008]    These and other features and advantages of the invention will be apparent upon reading of the following detailed description of the embodiments taken in conjunction with the figures in which like reference numeral indicate like elements throughout. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    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. 
           [0010]      FIG. 1  is a schematic illustration of a disk drive system in which the invention might be embodied; 
           [0011]      FIG. 2  is a view of a media facing surface of a slider, illustrating the location of a magnetic head thereon; 
           [0012]      FIG. 3  is a side, cross-sectional view of a magnetic recording head; 
           [0013]      FIG. 4  is a top down view of a thermal heating element as seen from line  4 - 4  of  FIG. 3 ; 
           [0014]      FIG. 5  is a cross sectional view of the thermal heating element as seen from line  5 - 5  of  FIG. 4 ; and 
           [0015]      FIG. 6  is a side cross sectional view of the thermal heating element as seen from line  6 - 6  of  FIG. 4 . 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    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. 
         [0017]    Referring now to  FIG. 1 , there is shown a disk drive  100 . The disk drive  100  includes a housing  101 . 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 . 
         [0018]    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  112  rotates, slider  113  moves in and out over the disk surface  122  so that the magnetic head assembly  121  can 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 the 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 the controller  129 . 
         [0019]    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 the suspension  115  and supports the slider  113  off and slightly above the disk surface by a small, substantially constant spacing during normal operation. 
         [0020]    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 the slider  113  to the desired data track on the media  112 . Write and read signals are communicated to and from write and read heads  121  by way of recording channel  125 . 
         [0021]    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 a view of the slider  113  as seen from the media facing surface, and as can be seen, the magnetic head  121 , including an inductive write head and a read sensor, is located at a trailing edge of the slider  113 . The above description of a typical magnetic disk storage system and the accompanying illustration of  FIGS. 1 and 2  are for representation purposes only. It should be apparent that the disk storage system may contain a large number of disks and actuators, and each actuator may support a number of sliders. 
         [0022]      FIG. 3  shows a magnetic head  300  formed on a substrate  302 . The substrate  302  can be a dielectric material such as alumina formed on a body of a slider  113  ( FIG. 2 ). The magnetic head  300  includes a magnetic read element  304 , a magnetic write element  306  and a thermal heating element  308  for thermal fly height control. The heating element  308  can be embedded in a non-magnetic, electrically insulating material such as alumina  309 . The purpose and function of the thermal fly height control and specific structure of the heating element  308  will be described in greater detail herein below. A non-magnetic, dielectric layer  307  can be included to separate the magnetic read and write elements  304 ,  306 . 
         [0023]    The read element  304  can include a magnetoresistive sensor  310  sandwiched between first and second magnetic shields  312 ,  314  and can be embedded in a dielectric material  316 . The magnetoresistive sensor  310  can be giant magnetoresistive sensor (GMR) or a tunnel junction magnetoresistive sensor (TMR). 
         [0024]    The magnetic write element  306  can include a magnetic write pole  318  that extends to a media facing surface MFS, and can also include a magnetic return pole  320 , which can be magnetically connected with the write pole  318  by a magnetic back gap layer  322  located away from the media facing surface MFS and a magnetic shaping layer  324  that is magnetically connected with the write pole  318  and helps to channel magnetic flux to the write pole  318 . The write element  306  has a non-magnetic, electrically conductive coil  326  that can pass below and above the write pole  318 . The write coil  326  can be embedded in a non-magnetic dielectric layer  328 . When a current flows through the write coil  326 , a magnetic field is induced that causes a magnetic write field to flow through the write pole  318 , return pole  320 , back gap layer  322  and shaping layer  324 . This causes a magnetic write field to emit from the write pole  318  in order to write a magnetic bit onto an adjacent magnetic media  112 . The write element  306  can also include a trailing magnetic shield  330 , which may be connected with a trailing magnetic return pole  332 , and which is separated from the write pole by a non-magnetic trailing gap layer  331 . The trailing magnetic shield  330  can help to increase field gradient, thereby improving magnetic performance. 
         [0025]    Magnetic spacing between the magnetic media  112  and the read and write elements  304 ,  306  has a large impact on magnetic performance. The magnetic signal drops off exponentially with distance, so minimizing magnetic spacing is critical to providing sufficient write field to write to the media  112  as well as ensuring sufficient signal strength to read data from the media  112  by the read sensor  310 . On the other hand, the magnetic head  300  should not become so close to the media  112  that it actually contacts the media  112 . Such head disk contact can damage the sensor  310  as well as leading to data loss. 
         [0026]    One way to adjust and control the magnetic spacing for optimal performance is through active thermal fly height control. In such as system, the thermal heating element  308  can be used to heat the surrounding structure. The resulting thermal expansion of the read and write heads  304 ,  306  causes them to protrude toward the media  112  in a controllable fashion. Heating elements can be formed of an electrically conductive material having a sufficiently high electrical resistance that Joule heating will cause them to heat up when an electrical current flows through the heating element. However, a problem presented by such heating elements is that the electrical current used to heat the heating element also results in a magnetic field (magnetomotive force) being generated. This magnetic field can be mistakenly read by the read sensor  310  and can even inadvertently lead to undesirable magnetization of the magnetic media  112 , thereby resulting in signal noise. The magnetic field from the heating element  308  can inadvertently magnetize the write pole, thereby causing a magnetic field from the write pole  318  to undesirably erase data from the magnetic media, a phenomenon known as “pole erasure”. Further, magnetic fields from the heating element can cause an asymmetrical signal to be recorded to the magnetic media  112 . 
         [0027]    The present invention solves this problem through use of a novel heating element design  308  that will be further described herein below with reference to  FIGS. 4 ,  5  and  6 .  FIG. 4  shows a top down view of a possible configuration of the thermal heating element  308  as seen from line  4 - 4  of  FIG. 3 . The thermal heating element  308  can have a bent shape as shown in  FIG. 4 , but could have some other shape as well. The heating element  308  can also include first and second lead pads  402 ,  404 , and an electrically conductive connection stud  406 . 
         [0028]      FIG. 5  shows a cross sectional view of a portion of the heating element  308  as seen from line  5 - 5  of  FIG. 4 . As shown in  FIG. 5 , the heating element  308  is constructed as a multi-layer structure having first and second electrically conductive layers  502 ,  506  that are separated by an electrically insulating, dielectric material  504  such as alumina or some other suitable material. The electrically conductive layers  502 ,  506  are configured such that current flowing through one layer  502  flows in an opposite direction to that of the other layer  506 , as indicated by arrows  508 ,  510 . 
         [0029]      FIG. 6  shows a cross sectional view of the connection stud  406  as seen from line  6 - 6  of  FIG. 4  and shows how the connection stud  406  can electrically connect the electrically conductive layers  502 ,  506  at an end of the heating element  308  opposite the leads  402 ,  404  ( FIG. 4 ). This, therefore, allows the currents  508 ,  510  to be in opposite directions when a current is applied through the lead pads  402 ,  404  ( FIG. 4 ). 
         [0030]    By causing the currents  508 ,  510  to flow in opposite direction, the magnetic field emitting from the conductive layers  508 ,  510  cancel each other out. Therefore, the heating element  308  emits no (or very little) magnetic field. This, therefore, vastly decreases the signal noise resulting from the heating element  308 . 
         [0031]    In one embodiment, one of the layers (e.g.  506 ) can be a material intended to provide Joule heating. The other element  502  need not be constructed to contribute to heating, but could be constructed merely to provide a current return path. To this end, one layer (e.g.  506 ) can be a material such as NiFe, having an electrical resistance that is sufficient to provide heating. The other layer  502  can be a material such as Cu, and as shown in  FIG. 4  the layer  502  can have a greater width or cross section to facilitate current flow. 
         [0032]    Alternatively, the layers  502 ,  506  can be constructed of the same material and could be constructed such that they both contribute to Joule heating. For example, the conductive layers  502 ,  506  can both be formed of NiFe. 
         [0033]    While various embodiments have been described above, 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. For example, while the magnetic head  300  (described above) has been described with reference to use in a magnetic disk drive system, the magnetic head  300  could be used in other applications as well, such as in a magnetic tape drive system. Thus, the breadth and scope of the invention may also become apparent to those skilled in the art. The breadth and scope of the inventions 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.