Abstract:
A magnetic write head for perpendicular magnetic data recording having a write pole that is sandwiched between first and second magnetic shaping layers. The split shaping layers allow a laminated shaping layer structure allows a manufacturable laminated shaping layer to be constructed for improved data rate. One of the magnetic shaping layers can be formed as a laminated structure while that other can be a single layer of electroplated magnetic material. The shaping layers can be separated from the write pole by a thin layer of non-magnetic material to form a laminated interface between the write pole and the shaping layers. These features reduce magnetic domains and also reduce eddy currents which advantageously improves data rate.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to perpendicular magnetic recording and more particularly to a magnetic write head having a multi-layer stitched pole for decreasing eddy current and increasing data rate. 
       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 has traditionally included a coil layer embedded in first, second and third insulation layers (insulation stack), the insulation stack being sandwiched between first and second pole piece layers. A gap is formed between the first and second pole piece layers by a gap layer at an air bearing surface (ABS) of the write head and the pole piece layers are connected at a back gap. Current conducted to the coil layer induces a magnetic flux in the pole pieces which causes a magnetic field to fringe out at a write gap at the ABS for the purpose of writing the aforementioned magnetic transitions in tracks on the moving media, such as in circular tracks on the aforementioned rotating disk. 
         [0004]    In recent read head designs a spin valve sensor, also referred to as a giant magnetoresistive (GMR) sensor, has been employed for sensing magnetic fields from the rotating magnetic disk. The sensor includes a nonmagnetic conductive layer, referred to as a spacer 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 spin valve 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]    The thickness of the spacer layer is chosen to be less than the mean free path of conduction electrons through the sensor. With this arrangement, a portion of the conduction electrons is scattered by the interfaces of the spacer layer with each of the pinned and free layers. 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]    In order to meet the ever increasing demand for improved data rate and data capacity, researchers have recently been focusing their efforts on the development of perpendicular recording systems. A traditional longitudinal recording system, such as one that incorporates the write head described above, stores data as magnetic bits oriented longitudinally along a track in the plane of the surface of the magnetic disk. This longitudinal data bit is recorded by a fringing field that forms between the pair of magnetic poles separated by a write gap. 
         [0007]    A perpendicular recording system, by contrast, records data as magnetizations oriented perpendicular to the plane of the magnetic disk. The magnetic disk has a magnetically soft underlayer covered by a thin magnetically hard top layer. The perpendicular write head has a write pole with a very small cross section and a return pole having a much larger cross section. A strong, highly concentrated magnetic field emits from the write pole in a direction perpendicular to the magnetic disk surface, magnetizing the magnetically hard top layer. The resulting magnetic flux then travels through the soft underlayer, returning to the return pole where it is sufficiently spread out and weak that it will not erase the signal recorded by the write pole when it passes back through the magnetically hard top layer on its way back to the return pole. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention provides a magnetic write head designed for increased data rate recording. The write head includes a magnetic write pole that is located between first and second magnetic shaping layers. 
         [0009]    One or both of the magnetic shaping layers can be separated from the write pole by a thin, electrically insulating, non magnetic layer. The presence of this electrically insulating, non-magnetic layer forms a laminated interface between the write pole and the shaping layer that advantageously reduces magnetic domains and eddy currents. 
         [0010]    In addition, one of the magnetic shaping layers can be configured as a laminated structure with layers of magnetic material separated by thin non-magnetic layers. This structure further reduces the formation of magnetic domains and eddy currents, thereby further increasing the data rate of the write head. 
         [0011]    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  
         [0012]    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. 
           [0013]      FIG. 1  is a schematic illustration of a disk drive system in which the invention might be embodied; 
           [0014]      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; 
           [0015]      FIG. 3  is a cross sectional view, taken from line  3 - 3  of  FIG. 2  and rotated 90 degrees counterclockwise, of a magnetic write head according to an embodiment of the present invention; and 
           [0016]      FIG. 4  is an enlarged view of a write pole and first and second shaping layers of a write head according to an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0017]    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. 
         [0018]    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 . 
         [0019]    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 . 
         [0020]    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. 
         [0021]    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 . 
         [0022]    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. 
         [0023]    With reference now to  FIG. 3 , the invention can be embodied in a magnetic write head  302 . The magnetic head  302  can include a read head portion  304  and a write head portion  306 . The read head portion  304  can include a magnetoresistive sensor  308  such as a giant magnetoresistive sensor GMR, tunnel valve (TMR) etc. The magnetoresistive sensor  308  can be located between first and second magnetic shields  310 ,  312 . 
         [0024]    The write head  306  includes a write pole  314 , having an end disposed toward an air bearing surface (ABS). The write head also includes a return pole  316 , which also has an end disposed toward the ABS. The return pole  316  is magnetically connected with a magnetic back gap  318 . The write pole  314  is magnetically coupled with first and second shaping layers  320 ,  321 , which will be described in greater detail herein below. The write pole  314  and magnetic shaping layers  320 ,  321  are magnetically coupled with the return pole via the back gap layer  318 . The non-magnetic layers  402 ,  404  can extend all of the way to the front and back edges of the shaping layers  320 ,  321  as shown (in which case the magnetic coupling between the write pole  314  and the shaping layers  320 ,  321  includes magnetostatic coupling. Alternatively, the non-magnetic layers  402 ,  404  can stop short of one or both of the front or back edges of the shaping layers  320 ,  321  so that at least a portion of the write pole  314  is directly magnetically connected with the shaping layers  320 ,  321 . 
         [0025]    The write pole  320  is preferably constructed of a high magnetic moment, low coercivity magnetic material, and is more preferably constructed as a laminate of layers of magnetic material separated by thin layers of non-magnetic material. 
         [0026]    The write head  306  also includes an electrically conductive write coil  322 , shown in cross section in  FIG. 3 . The write coil can be constructed of, for example, Cu and can be a pancake coil that wraps around the back gap  318  or can be a helical coil having upper and lower leads (as shown) disposed above and below tile write pole  314  and shaping layers  320 ,  321 . The upper and lower leads of the write coil  322  can each be formed upon an insulating layer  324  and surrounded by a coil insulation layer  326 , and the upper leads can be connected with certain of the bottom leads in regions into and out of the plane of the page and, therefore, not shown in  FIG. 3 . 
         [0027]    During operation, a magnetic field from the write coil  322  causes a magnetic flux to flow through the shaping layer  320  and write pole  314 . This causes a magnetic write field  328  to emit from the write pole  314  at the ABS. This write field  328  passes through a thin magnetically hard top layer  330  of an adjacent magnetic medium  332 . The write field then travels through a magnetically soft under-layer  334  of the magnetic medium  332  before passing back to the return pole  316 . The write field emitted from the write pole  314  locally magnetizes the magnetically hard top layer  330 , thereby writing a bit of data. The return pole  316  has a cross section at the ABS that is much larger than that of the write pole  314  so that the write field  328  passing back to the return pole is sufficiently spread out that it does not erase the previously recorded bit. 
         [0028]    A magnetic pedestal  336  can be provided, and can be magnetically connected with the return pole  316  at the ABS end of the return pole  316 , extending toward, but not to the write pole  314 . The magnetic pedestal can act as a shield to prevent stray fields, such as from the write coil  332  from inadvertently writing to the magnetic medium  332 . 
         [0029]    With reference still to  FIG. 3 , the write head  306  may also include a trailing magnetic shield  338 , which is separated from the write pole  314  by a trailing gap  339 . The presence of the trailing magnetic shield  338  increases the field gradient of the write field  328 , thereby increasing the recording density with which the write head  306  can write data. The trailing shield  338  can be magnetically connected with the back portion of the write head  306  by a magnetic upper or trailing return pole  340  or could just be a floating design. 
         [0030]    With reference now to  FIG. 4 , which shows the write pole  314  and shaping layers  320 ,  321  enlarged, the relationship between the write pole  314  and shaping layers  320 ,  321  can be more clearly understood. The write pole  314  is sandwiched between first and second magnetic shaping layers  320 ,  321 . One or both of the magnetic shaping layers  320 ,  321  can be separated from the write pole  314  by a thin, non-magnetic, electrically insulating layer  402 ,  404 , so that the write pole  314  non-magnetic layers  402 ,  404  and shaping layers  320 ,  321  together form a laminated structure that has a more favorable magnetic domain formation for the faster magnetic switching of the magnetic layers  320 ,  321 ,  314  which increases the recording data rate. The eddy current loss is also reduced with the laminate structure, which increases the recording data rate as well. The non-magnetic, electrically insulating layers  402 ,  404  can be constructed of alumina or some other non-magnetic, electrically insulating material, and can each have a thickness of 5 to 100 Angstroms. 
         [0031]    The first, or lower shaping layer  320  can be constructed as a single layer of magnetic material such as CoFe or NiFe, which can be formed by electroplating into a photoresist frame structure. The second, or upper, shaping layer  321  could also be constructed as a single layer of electroplated, magnetic material such as CoFe or NiFe, but is preferably a laminated structure such as that shown. The second shaping layer  321  can, therefore, be constructed as a plurality of magnetic layers  406  separated from one another by thin, non-magnetic layers  408 . The magnetic layers  406  can be CoFe, NiFe or some other suitable magnetic material. 
         [0032]    If constructed as a laminated structure, the layers  406 ,  408  of the second shaping layer  321  can be constructed by sputter depositing the layers  406 ,  408  as full film layers, and then forming a mask structure (not shown) to cover areas where the upper shaping layer is to be. A material removal process can then be used to remove portions of the layers  406 ,  408  that are not protected by the mask structure. This process can be used to form when forming a laminated shaping layer, because the second shaping layer  321  is not constructed directly over the coils  322  ( FIG. 3 ). The thickness of the non-magnetic layers  406  is typically 5 to 100 Angstroms. Although the shaping layer  321  is shown with three magnetic layers  406  and two non-magnetic layers  408 , this is for purposes of illustration only, and some other number of layers could be used. 
         [0033]    While it would be desirable to construct the lower shaping layer  320  as a laminated structure, the construction of such a laminated structure directly over the coils  322  ( FIG. 3 ) is problematic. For example, sputter depositing a bottom shaping layer, in order to construct it with a laminated structure would require an ion milling process to remove the unwanted portions of the deposited layer, as described above with reference to the upper shaping layer  321 . If this were done to construct the lower shaping layer, then the coils  322 , below the lower shaping layer  320  would be damaged during the ion milling. Further, if the shaping layer were deposited sufficiently thick to form a laminated lower shaping layer, the mask would not be easily lifted off. A material removal process such as a CMP process would be needed to remove the mask structure, and the use of such a CMP process would make accurate control the thickness of shaping layer  320  very difficult. However, constructing the structure as a write pole  314  disposed between first and second split shaping layers, overcomes these challenges, allowing the upper shaping layer  321  to provide the benefits of a laminated structure, while allowing the lower shaping layer  320  to be constructed by electroplating to facilitate manufacturing and minimize damage to underlying layers such as the coil  322  ( FIG. 3 ). 
         [0034]    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.