Abstract:
The first and second side surfaces of either a bottom spin valve sensor or a top spin valve sensor are notched so as to enable a reduction in the magnetoresistive coefficient of side portions of the sensor beyond the track width region thereby minimizing side reading by the sensor. The first and second notches of the spin valve sensor are then filled with layers in various embodiments of the invention to complete the spin valve sensor.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to an overlaid lead giant magnetoresistive head with side reading reduction and, more particularly, to such a head wherein first and second side surfaces of a spin valve sensor are notched and replaced with refill layers for minimizing a magnetoresistive coefficient of the spin valve sensor in side regions beyond a track width of the read head.  
           [0003]    2. Description of the Related Art  
           [0004]    The heart of a computer is a magnetic disk drive which includes a rotating magnetic disk, a slider that has read and write heads, a suspension arm above the rotating disk and an actuator arm that swings the suspension arm to place the read and write heads over selected circular tracks on the rotating disk. The suspension arm urges 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 adjacent an air bearing surface (ABS) of the slider causing the slider to ride on an air bearing a slight distance from the surface of 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 signal fields 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.  
           [0005]    An exemplary high performance giant magnetoresistive (GMR) read head employs a spin valve sensor for sensing the magnetic field signals from the rotating magnetic disk. The sensor includes a nonmagnetic electrically conductive first spacer layer sandwiched between a ferromagnetic pinned layer structure and a ferromagnetic free layer structure. An antiferromagnetic pinning layer interfaces the pinned layer structure for pinning a magnetic moment of the pinned layer structure 90° to an air bearing surface (ABS) wherein the ABS is an exposed surface of the sensor that faces the magnetic disk. First and second leads are connected to the spin valve sensor for conducting a sense current therethrough. A magnetic moment of the free layer structure is free to rotate upwardly and downwardly with respect to the ABS from a quiescent or zero bias point position in response to positive and negative magnetic field signals from a rotating magnetic disk. The quiescent position, which is parallel to the ABS, is the position of the magnetic moment of the free layer structure when the sense current is conducted through the sensor in the absence of field signals.  
           [0006]    The thickness of the spacer layer is chosen so that shunting of the sense current and a magnetic coupling between the free and pinned layer structures are minimized. This thickness is typically less than the mean free path of electrons conducted through the sensor. With this arrangement, a portion of the conduction electrons are scattered at the interfaces of the spacer layer with the pinned and free layer structures. When the magnetic moments of the pinned and free layer structures are parallel with respect to one another scattering is minimal and when their magnetic moments are antiparallel scattering is maximized. Changes in scattering changes the resistance of the spin valve sensor as a function of cos θ, where θ is the angle between the magnetic moments of the pinned and free layer structures. The sensitivity of the sensor is quantified as magnetoresistive coefficient dr/R where dr is the change in the resistance of the sensor as the magnetic moment of the free layer structure rotates from a position parallel with respect to the magnetic moment of the pinned layer structure to an antiparallel position with respect thereto and R is the resistance of the sensor when the magnetic moments are parallel.  
           [0007]    In addition to the spin valve sensor the GMR read head includes nonmagnetic electrically nonconductive first and second read gap layers and ferromagnetic first and second shield layers. The spin valve sensor is located between the first and second read gap layers and the first and second read gap layers are located between the first and second shield layers. In the construction of the read head the first shield layer is formed first followed by formation of the first read gap layer, the spin valve sensor, the second read gap layer and the second shield layer. Spin valve sensors are classified as a top or a bottom spin valve sensor depending upon whether the pinning layer is located near the bottom of the sensor close to the first read gap layer or near the top of the sensor close to the second read gap layer. Spin valve sensors are further classified as simple pinned or antiparallel pinned depending upon whether the pinned layer structure is one or more ferromagnetic layers with a unidirectional magnetic moment or a pair of ferromagnetic layers that are separated by a coupling layer with magnetic moments of the ferromagnetic layers being antiparallel respectively. Spin valve sensors are still further classified as single or dual wherein a single spin valve sensor employs only one pinned layer and a dual spin valve sensor employs two pinned layers with the free layer structure located therebetween.  
           [0008]    In a prior art spin valve sensor first and second hard bias and lead layers interface first and second side surfaces of the spin valve sensor wherein the first and second side surfaces intersect the ABS. This type of sensor is referred to in the art as a contiguous junction type of sensor and is fully described in U.S. Pat. No. 5,018,037. Each of the first and second hard bias layers is a strong magnet which longitudinally biases the free layer so that it is magnetically stable in a single domain state. Unfortunately, a magnetic moment in each of the first and second side portions of the free layer are pinned by the first and second hard bias layers so that they do not rotate (respond) to field signals from the rotating magnetic disk. As the sensor track width dimensions grow narrower the pinned regions, which are also referred to as dead layer regions, become a larger fraction of the sensor track width. Consequently, less of the free layer in the sensor track width region is available to read the field signal.  
           [0009]    In order to overcome the problem with the prior art contiguous junction type of sensor the contiguous junctions of the first and second hard bias layers are moved further away from the track width region and first and second conducting leads overlap the first and second hard bias layers and first and second top portions of the sensor with the spacing between the leads defining the track width of the sensor. A problem with this design is that a small portion of the sense current will still pass through the sensor layers below the conducting leads, even though the conducting leads have a much lower resistance than the spin valve sensor layers. Unfortunately, this causes the spin valve layer portions below the first and second conducting leads to be slightly active so as to have some response to field signals from the rotating magnetic disk. Since these field signals are outside the track to be read the sensor is sensing field signals from adjacent tracks which is referred to as side reading. There is a strong-felt need to overcome this side reading problem in the continuous type (overlapping leads) spin valve sensor.  
         SUMMARY OF THE INVENTION  
         [0010]    The present invention minimizes the side reading problem by notching the first and second side surfaces of the spin valve sensor and disposing first and second ferromagnetic refill layers in the notches wherein the ferromagnetic refill layers magnetically couple the first and second hard bias layers to first and second side edges of the free layer. The first and second conducting leads overlap the first and second hard bias layers and the first and second ferromagnetic refill layers. The notches in the side surfaces of the spin valve sensor are sized so as to reduce the magnetoresistive coefficient dr/R of the spin valve sensor portions below the first and second conducting leads. In a first embodiment of the invention a cap layer at the top of a bottom spin valve sensor is provided with first and second recessed side surfaces which, in turn, provide the first and second notches. The first and second ferromagnetic refill layers are disposed within the notches and interface the free layer so that the free layer is thicker in the regions below the first and second leads. The magnetoresistive coefficient dr/R is lowered with the increasing free layer thickness below the conducting leads and the thicker regions are further more resistant to demagnetization.  
           [0011]    In a second embodiment the first and second side surfaces of each of the cap layer and the free layer are recessed to provide the first and second notches. First and second copper refill layers interface first and second top surfaces of the spacer layer and the first and second ferromagnetic refill layers overlay the first and second copper refill layers. Because of the increased thickness of the spacer layer in the regions below the first and second leads the magnetoresistive coefficient dr/R has been decreased. Because of the thinness of the first and second copper refill layers the first and second ferromagnetic refill layers are still magnetically coupled to the first and second hard bias layers for longitudinally biasing the free layer.  
           [0012]    In a third embodiment of the invention the first and second side surfaces of the cap and free layers are recessed and a portion of the first and second side surfaces of the spacer layer are recessed to provide the first and second notches. First and second ferromagnetic refill layers are disposed in the first and second notches with the first and second ferromagnetic layers being directly magnetically coupled to the first and second hard bias layers and the free layer. With this embodiment the spacer layer has first and second thin portions below the first and second leads which causes a ferromagnetic coupling field between the pinned and free layers in these regions. This pins the magnetic moment of the free layer in these regions so that it will not respond to field signals from the rotating magnetic disk.  
           [0013]    In a fourth embodiment of the invention the first and second side surfaces of each of the cap layer, free layer and spacer layer are recessed so as to provide the first and second notches. The first and second ferromagnetic refill layers are disposed within the first and second notches and are magnetically coupled between the first and second hard bias layers and the free layer. The first and second ferromagnetic refill layers interface first and second top surface portions of the pinned layer and effectively increase its thickness in the regions below the first and second leads. The extra thick pinned layer portions in these regions cannot effectively be pinned by the pinning layer therebelow so that the magnetoresistive coefficient dr/R is minimized.  
           [0014]    In a fifth embodiment of the present invention first and second side surfaces of the cap layer and first and second side surfaces of the pinning layer are recessed in a top spin valve sensor so as to provide the first and second notches and the first and second conductive leads are disposed within the first and second notches and overlay the first and second hard bias layers. In this embodiment the first and second ferromagnetic refill layers are not required since the first and second hard bias layers interface the first and second side surfaces of the free layer for stabilizing the free layer. In this embodiment first and second side portions of the pinned layer are no longer pinned and the magnetoresistive coefficient dr/R of the regions of the sensor below the first and second leads is minimized.  
           [0015]    An object of the present invention is to minimize the magnetoresistive coefficient dr/R of side regions of a continuous junction spin valve sensor which are below first and second conducting leads.  
           [0016]    Another object is to provide an overlaid lead GMR head wherein a spin valve sensor has reduced side reading.  
           [0017]    A further object is to provide a method of making the aforementioned spin valve sensors.  
           [0018]    Other objects and attendant advantages of the invention will be appreciated upon reading the following description taken together with the accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]    [0019]FIG. 1 is a plan view of an exemplary magnetic disk drive;  
         [0020]    [0020]FIG. 2 is an end view of a slider with a magnetic head of the disk drive as seen in plane  2 - 2  of FIG. 1;  
         [0021]    [0021]FIG. 3 is an elevation view of the magnetic disk drive wherein multiple disks and magnetic heads are employed;  
         [0022]    [0022]FIG. 4 is an isometric illustration of an exemplary suspension system for supporting the slider and magnetic head;  
         [0023]    [0023]FIG. 5 is an ABS view of the magnetic head taken along plane  5 - 5  of FIG. 2;  
         [0024]    [0024]FIG. 6 is a partial view of the slider and a merged magnetic head as seen in plane  6 - 6  of FIG. 2;  
         [0025]    [0025]FIG. 7 is a partial ABS view of the slider taken along plane  7 - 7  of FIG. 6 to show the read and write elements of the magnetic head;  
         [0026]    [0026]FIG. 8 is a view taken along plane  8 - 8  of FIG. 6 with all material above the coil layer and leads removed;  
         [0027]    [0027]FIG. 9 is an enlarged isometric ABS illustration of a prior art read head with a contiguous junction type spin valve sensor;  
         [0028]    [0028]FIG. 10 is an enlarged isometric ABS illustration of a prior art read head with a continuous junction type spin valve sensor;  
         [0029]    [0029]FIG. 11 is an ABS illustration of the present spin valve sensor before forming first and second overlaid leads;  
         [0030]    [0030]FIG. 12A is an ABS view of the first embodiment of the present spin valve sensor after ion milling first and second notches and forming first and second refill layers and first and second conductive leads in the notches;  
         [0031]    [0031]FIG. 12B is the same as FIG. 12A except a bilayer photoresist layer has been removed;  
         [0032]    [0032]FIG. 13A is an ABS illustration of a second embodiment of the present spin valve sensor wherein first and second notches have been formed and first and second copper layers, first and second ferromagnetic layers and first and second leads have been formed in the notches;  
         [0033]    [0033]FIG. 13B is the same as FIG. 1A except a bilayer photoresist layer has been removed;  
         [0034]    [0034]FIG. 14A is an ABS illustration of a third embodiment of the present spin valve sensor after ion milling first and second notches and forming first and second ferromagnetic layers and first and second leads in the notches;  
         [0035]    [0035]FIG. 14B is the same as FIG. 14A except a bilayer photoresist layer has been e Fi removed;  
         [0036]    [0036]FIG. 15A is an ABS illustration of a fourth embodiment of the present spin valve sensor after ion milling first and second notches and forming first and second ferromagnetic layers and first and second leads in the notches;  
         [0037]    [0037]FIG. 15B is the same as FIG. 15A except a bilayer photoresist layer has been removed;  
         [0038]    [0038]FIG. 16 is an ABS illustration of a top spin valve sensor which has been partially completed;  
         [0039]    [0039]FIG. 17A is and ABS illustration of a firth embodiment of the present spin valve sensor after ion milling first and second notches and depositing first and second conductive leads in the notches; and  
         [0040]    [0040]FIG. 17B is the same as FIG. 17A except a bilayer photoresist layer has been removed.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     Magnetic Disk Drive  
       [0041]    Referring now to the drawings wherein like reference numerals designate like or similar parts throughout the several views, FIGS.  1 - 3  illustrate a magnetic disk drive  30 . The drive  30  includes a spindle  32  that supports and rotates a magnetic disk  34 . The spindle  32  is rotated by a spindle motor  36  that is controlled by a motor controller  38 . A slider  42  has a combined read and write magnetic head  40  and is supported by a suspension  44  and actuator arm  46  that is rotatably positioned by an actuator  47 . A plurality of disks, sliders and suspensions may be employed in a large capacity direct access storage device (DASD) as shown in FIG. 3. The suspension  44  and actuator arm  46  are moved by the actuator  47  to position the slider  42  so that the magnetic head  40  is in a transducing relationship with a surface of the magnetic disk  34 . When the disk  34  is rotated by the spindle motor  36  the slider is supported on a thin (typically, 0.05 μm) cushion of air (air bearing) between the surface of the disk  34  and the air bearing surface (ABS)  48 . The magnetic head  40  may then be employed for writing information to multiple circular tracks on the surface of the disk  34 , as well as for reading information therefrom. Processing circuitry  50  exchanges signals, representing such information, with the head  40 , provides spindle motor drive signals for rotating the magnetic disk  34 , and provides control signals to the actuator for moving the slider to various tracks. In FIG. 4 the slider  42  is shown mounted to a suspension  44 . The components described hereinabove may be mounted on a frame  54  of a housing  55 , as shown in FIG. 3.  
         [0042]    [0042]FIG. 5 is an ABS view of the slider  42  and the magnetic head  40 . The slider has a center rail  56  that supports the magnetic head  40 , and side rails  58  and  60 . The rails  56 ,  58  and  60  extend from a cross rail  62 . With respect to rotation of the magnetic disk  34 , the cross rail  62  is at a leading edge  64  of the slider and the magnetic head  40  is at a trailing edge  66  of the slider.  
         [0043]    [0043]FIG. 6 is a side cross-sectional elevation view of a merged magnetic head  40 , which includes a write head portion  70  and a read head portion  72 , the read head portion employing a spin valve sensor  74  of the present invention. FIG. 7 is an ABS view of FIG. 6. The spin valve sensor  74  is sandwiched between nonmagnetic electrically nonconductive first and second read gap layers  76  and  78 , and the read gap layers are sandwiched between ferromagnetic first and second shield layers  80  and  82 . In response to external magnetic fields, the resistance of the spin valve sensor  74  changes. A sense current I S  conducted through the sensor causes these resistance changes to be manifested as potential changes. These potential changes are then processed as readback signals by the processing circuitry  50  shown in FIG. 3.  
         [0044]    The write head portion  70  of the magnetic head  40  includes a coil layer  84  sandwiched between first and second insulation layers  86  and  88 . A third insulation layer  90  may be employed for planarizing the head to eliminate ripples in the second insulation layer caused by the coil layer  84 . The first, second and third insulation layers are referred to in the art as an “insulation stack”. The coil layer  84  and the first, second and third insulation layers  86 ,  88  and  90  are sandwiched between first and second pole piece layers  92  and  94 . The first and second pole piece layers  92  and  94  are magnetically coupled at a back gap  96  and have first and second pole tips  98  and  100  which are separated by a write gap layer  102  at the ABS. Since the second shield layer  82  and the first pole piece layer  92  are a common layer this head is known as a merged head. In a piggyback head (not shown) the second shield layer and the first pole piece layer are separate layers which are separated by a nonmagnetic layer. As shown in FIGS. 2 and 4, first and second solder connections  104  and  106  connect leads from the spin valve sensor  74  to leads  112  and  114  on the suspension  44 , and third and fourth solder connections  116  and  118  connect leads  120  and  122  from the coil  84  (see FIG. 8) to leads  124  and  126  on the suspension.  
         [0045]    [0045]FIG. 9 is an enlarged ABS illustration of a portion of the prior art read head  40  within the spin valve sensor  74  shown in FIG. 6. First and second hard bias and lead layers  134  and  136  are connected to first and second side surfaces  138  and  140  of the spin valve sensor  74 . This connection is known in the art as a contiguous junction and is fully described in commonly assigned U.S. Pat. No. 5,018,037. The first hard bias and lead layers  134  include a first hard bias layer  142  and a first lead layer  144  and the second hard bias and lead layers  136  include a second hard bias layer  146  and a second lead layer  148 . The hard bias layers  142  and  146  cause magnetic fields to extend longitudinally through the spin valve sensor  74  for stabilizing the free layer in a single domain state. The spin valve sensor  74  and the first and second hard bias and lead layers  134  and  136  are located between the first and second read gap layers  76  and  78  and the first and second read gap layers  76  and  78  are located between the ferromagnetic first and second shield layers  80  and  82  as shown in FIG. 7.  
         [0046]    The spin valve sensor  74  includes a nonmagnetic electrically conductive spacer layer (S)  150  which is located between a ferromagnetic free layer structure (F)  152  and a ferromagnetic pinned layer structure (P)  154 . The free layer structure  152  may be a single ferromagnetic layer, such as nickel iron, or a combined nickel iron layer and a cobalt iron layer wherein the cobalt iron layer interfaces the spacer layer  150 . The pinned layer structure  154  may be a single ferromagnetic layer, as shown, such as cobalt iron, or an AP pinned layer structure, as described hereinabove, with first and second cobalt iron pinned layers. An antiferromagnetic (AFM) pinning layer  156  is exchange coupled to the pinned layer  154  for pinning a magnetic moment  158  of the pinned layer perpendicular to the ABS in a direction out of the sensor or into the sensor, as shown in FIG. 9. A cap layer  160 , which may be tantalum, is located on top of the free layer  152  for protecting the spin valve sensor from subsequent processing steps. The free layer has a magnetic moment  161  which is oriented parallel to the ABS and to the major planes of the spin valve layers in a direction from right to left or from left to right, as shown in FIG. 9. When a field signal from the rotating magnetic disk rotates the magnetic moment  161  into the head the magnetic moments  161  and  158  become more parallel which decreases the resistance of the spin valve sensor to a sense current I S  and when the field signal from the rotating magnetic disk rotates the magnetic moment  161  out of the head the magnetic moments  161  and  158  become more antiparallel which increases the resistance of the spin valve sensor to the sense current I S . These resistance changes are processed as playback signals by the processing circuitry  50  in FIG. 3. The spin valve sensor has a track width (TW) which is defined by the distance between midpoints of first and second side surfaces of the free layer  152 .  
         [0047]    It is desirable that the track width of the spin valve sensor  74  be as narrow as possible for increasing the track width density of the read head. The track width density is quantified as tracks per inch (TPI) along a radius of the rotating magnetic disk. The linear bit density of the read head is defined by the distance between the first and second shield layers  80  and  82 , as seen in FIG. 7. Linear bit density is quantified as bits per inch along a track of the rotating magnetic disk. A product of the tracks per inch and the bits per inch is referred to in the art as the areal density. Past efforts increasing the areal density has increased the storage capability of computers from kilobytes to megabytes to gigabytes.  
         [0048]    As discussed hereinabove, the first and second hard bias layers  142  and  146  longitudinally bias the free layer  152  so as to stabilize the magnetic moment  162  of the free layer in a single magnetic domain state. Unfortunately, the first and second hard bias layers  142  and  146  pin magnetic moment portions in first and second side portions  162  and  164  of the free layer which prevents the magnetic moments in these side portions from rotating in response to field signals from the rotating magnetic disk. As the track width of the spin valve sensor is made more narrow the first and second side regions become a larger fraction of the sensor track width. The result is less of the free layer in the sensor track width area is available to sense the field signals from the rotating magnetic disk.  
         [0049]    The aforementioned problem with the contiguous junction type spin valve sensor in FIG. 9 has been alleviated with a read head  200  that has a continuous type spin valve sensor  201 , as shown in FIG. 10. The spin valve sensor  201  in FIG. 10 is the same as the spin valve sensor  74  in FIG. 9 except the layers of the spin valve sensor have been widened so that the first and second side surfaces  138  and  140  are laterally further away from the track width, the addition of first and second cap layer portions  202  and  204  which overlay the first and second hard bias layers  142  and  146  and electrically conductive first and second lead layers  206  and  208  which overlay the first and second cap layer portions  202  and  204  and first and second top surface portions of the cap layer  160 . This type of sensor is also referred to in the art as an overlaid lead type of sensor. The distance between the leads  206  and  208  define the track width (TW) of the read head. It can now be seen that the pinned or dead regions  162  and  164  of the free layer are now outside of the track width so that they do not constitute a portion of the track width. Accordingly, the magnetic moment within the entire track width of the free layer is now more responsive to field signals from the rotating magnetic disk. Unfortunately, first and second portions  210  and  212  of the free layer structure between the track width portion of the free layer and the first and second pinned portions  162  and  164  have magnetic moments which respond to field signals from a rotating magnetic disk. Even though the first and second leads  206  and  208  have considerably lower resistance a small amount of the sense current I S  is conducted through the portions  210  and  212  so that the magnetic moments of the first and second free layer portions  210  and  212  respond to field signals from tracks on the rotating magnetic disk that are adjacent to the track being read by the track width portion of the free layer. This contributes to what is known in the art as side reading which is unacceptable performance for a spin valve sensor. It is this problem that the present invention addresses.  
       The Invention  
       [0050]    Six embodiments of the present invention are described herein. The first five embodiments embody the partially fabricated read head  300  and spin valve sensor  301  in FIG. 11. FIG. 11 is the same as FIG. 10 except the first and second lead layers  206  and  208  are omitted. The spin valve sensor  301  in FIG. 11 is referred to as a bottom spin valve sensor since the pinning layer  156  is at the bottom of the sensor closer to the first read gap layer  76  than to the second read gap layer  78  shown in FIG. 6. It should be noted that each of the layers of the spin valve sensor  301  have first and second side surfaces which, in combination, form the first and second side surfaces  138  and  140  described hereinabove. In a broad concept of one aspect of the invention the first and second side surfaces of the layers of the spin valve sensor are selectively notched in order to reduce the magnetoresistive coefficient dr/R of side regions of the sensor beyond the track width so as minimize side reading by the sensor.  
         [0051]    A partial fabrication of a first embodiment of the read head  400  with the present spin valve sensor  401  is shown in FIG. 12A. A bilayer photoresist  402  is formed on top of the cap layer  160  for defining the track width (TW) of the read head. In a step of a method of the invention ion milling is implemented which removes side portions of the cap layer  160  down to the free layer  152 . The removal of the Ta layer can also be done with a reactive ion etching (RIE) process for better selectivity. The original locations of the layers that have been removed are shown in phantom. The result is that first and second side surfaces  404  and  406  of the cap layer are recessed relative to the first and second side surfaces of the layers therebelow. This forms the spin valve sensor with first and second notches  408  and  410 . Next, in the method of the invention ferromagnetic first and second refill layers  412  and  414 , which may be nickel iron (NiFe), are disposed in the first and second notches  408  and  410  interfacing first and second top surface portions  416  and  418  of the free layer structure and overlaying the first and second hard bias layers  142  and  146 . First and second lead layers  420  and  422  are deposited on top of the refill layers  412  and  414  and on top of top surface portions  424  and  426  of the cap layer. In this embodiment the first and second refill layers  412  and  414  have essentially increased the magnetic thickness of the free layer portions  210  and  212 . The increase in thickness of each of the portions  210  and  212  decreases the magnetoresistive coefficient dr/R of these portions so that the capability of these portions to side read adjacent tracks has been minimized. Further, the thicker portions  210  and  212  render the free layer more resistant to demagnetization. FIG. 12B is the same as FIG. 12A except the bilayer photoresist  402  has been lifted off of the sensor by dissolving the lower portion of the bilayer resist leaving the track width (TW).  
         [0052]    [0052]FIG. 13A illustrates a second embodiment of the present read head  500  and sensor  501  which is the same as the first embodiment shown in FIG. 12A except for ion milling of the layers and the refill layers. In this embodiment ion milling (IM) is implemented to mill away first and second side portions of the cap layer  160  and first and second side portions of the free layer  152  down to first and second top surface portions  502  and  504  of the spacer layer  150 . This forms the cap layer  160  with first and second side surfaces  404  and  406  and the free layer  152  with first and second side surfaces  506  and  508  which are recessed relative to the side surfaces of the layers therebelow which, in turn, provides the spin valve sensor  501  with first and second notches  510  and  512 . The original locations of the layers before ion milling are shown in phantom. Nonmagnetic electrically conductive first and second refill layers  514  and  516 , which are preferably copper (Cu), are then deposited into the notches  510  and  512  on top of the top surface portions  502  and  504  and on top of the first and second hard bias layers  142  and  146 . Ferromagnetic third and fourth refill layers  518  and  520 , which are preferably nickel iron (NiFe), are then deposited on top of the first and second refill layers  514  and  516 . Finally, first and second lead layers  522  and  524  are deposited on top of the third and fourth refill layers  518  and  520  and on top of first and second top surface portions  526  and  528  of the cap layer. In FIG. 13B the bilayer photoresist  402  is lifted off, as discussed hereinabove. By increasing the thickness of the side portions of the spacer layer  150  on top of the top surfaces  502  and  504  the magnetoresistive coefficient dr/R of the spin valve sensor portions between the track width (TW) and the hard bias layers  142  and  146  is significantly decreased. Again this will minimize side reading of adjacent tracks to the track being read by the sensor.  
         [0053]    [0053]FIG. 14A illustrates a third embodiment of the present read head  600  and spin valve sensor  601  which is the same as the embodiment in FIG. 13A except for the ion milling step and the refill layers. Ion milling (IM) is implemented to remove first and second side portions of the cap layer  160 , first and second side portions of the free layer  152  and portions of first and second side portions of the spacer layer  150 . This provides the cap layer with first and second side surfaces  404  and  406 , the free layer with first and second side surfaces  506  and  508  and the spacer layer with first and second side surfaces  602  and  604 . The side surfaces  404 ,  406 ,  506 ,  508 ,  602  and  604  are recessed relative to the side surfaces of the layers therebelow. This provides the spin valve sensor with first and second notches  606  and  608 . The original locations of the layers ion milled are shown in phantom. The ion milling also provides the first and second side portions of the spacer layer with first and second top surfaces  610  and  612 . Ferromagnetic first and second refill layers  614  and  616 , which are preferably nickel iron (NiFe), are then deposited into the notches  606  and  608  on top of the first and second hard bias layers  142  and  146 . In this embodiment the first and second side portions of the spacer layer below the top surfaces  610  and  612  have been reduced in thickness so that a coupling field between the pinned layer  154  and extended portions of the free layer due to deposition of the first and second refill layers  614  and  616  pin magnetic moments of the extended portions of the free layer so as to minimize the magnetoresistive coefficient dr/R beyond the track width (TW) of the sensor. In FIG. 14B the bilayer photoresist  402  has been removed to provide the track width (TW) as discussed hereinabove.  
         [0054]    [0054]FIG. 15A is a partially completed fourth embodiment of the present read head  700  and sensor  701  which is the same as the embodiment in FIG. 14A except for the ion milling and the refill layers. Ion milling is implemented to remove first and second side portions of the cap layer  160 , first and second side portions of the free layer  152  and first and second side portions of the spacer layer  150  down to first and second top portions  702  and  704  of the pinned layer. This provides the cap layer with first and second side surfaces  404  and  406 , the free layer structure with first and second side surfaces  506  and  508  and the spacer layer with first and second side Hi surfaces  706  and  708  which are recessed relative to the side surfaces of the layers therebelow which form first and second notches  710  and  712 . Ferromagnetic first and second refill layers  714  and  716 , which are preferably nickel iron (NiFe), are then deposited in the notches  710  and  712  on top of the top surfaces  702  and  704  and on top of the first and second hard bias layers  142  and  146 . First and second lead layers  718  and  720  are then deposited on top of the first and second refill layers  714  and  716  and on top of first and second top surface portions  722  and  724  of the cap layer. In FIG. 15B the bilayer photoresist  402  is removed as discussed hereinabove. The pinning strength of the pinning layer  156  is inversely proportional to the thickness of the pinned layer  154 . Accordingly, the thicker first and second side portions of the pinned layer due to the deposition of the first and second refill layers  714  and  716  effectively reduces the pinning of the magnetic moment of these portions of the pinned layer so as to minimize the magnetoresistive coefficient dr/R outside of the track width. This then minimizes side reading by the spin valve sensor.  
         [0055]    The partially completed read head  800  and spin valve sensor  801  in FIG. 16 is the same as the read head and spin valve sensor in FIG. 11 except the free layer  152 , the spacer layer  150 , the pinned layer  154  and the pinning layer  156  have been inverted and one or more seed layers (SL)  802  are provided below the free layer  152 . FIG. 17A is a fifth embodiment of the present read head  900  and sensor  901  is the same as the partially completed read head  800  and sensor  801  in FIG. 16 except for ion milling steps and deposition of certain layers. The bilayer photoresist  402  is located on top of the cap layer  160  as discussed hereinabove. Ion milling (IM) is implemented to mill away first and second side portions of the cap layer  160 , first and second side portions of the pinning layer  156  and optionally portions of first and second side portions of the pinned layer  154  (overmilling) to form first and second side portions of the pinned layer with first and second top surface portions  903  and  904 . This provides the cap layer with first and second side surfaces  404  and  406 , the pinning layer with first and second side surfaces  906  and  908  and optionally the pinned layer with first and second side surfaces  910  and  912  which are recessed relative to the side surfaces of the layers therebelow. This provides the spin valve sensor with first and second notches  914  and  916 . First and second lead layers  918  and  920  are then deposited into the notches  914  and  916  on top of the top surfaces  903  and  904  and on top of the first and second hard bias layers  142  and  146 . In FIG. 17B the bilayer photoresist  402  is removed as discussed hereinabove. In this embodiment the side portions or remaining side portions of the pinned layer  154  beyond the track width are no longer pinned by the pinning layer  156 . Therefore the magnetoresistive coefficient dr/R in the side portions of the read head beyond the track width has been eliminated or at least reduced to eliminate or at least minimize side reading.  
       Discussion  
       [0056]    It should be noted that after the ion milling in FIG. 12A the first and second hard bias layers  142  and  144  engage the first and second side surfaces of the free layer  152  for longitudinally biasing the free layer. In FIG. 13A the first and second copper refill layers  514  and  516  are sufficiently thin so that there is a magnetic coupling between the first and second hard bias layers  142  and  146  and the first and second ferromagnetic refill layers  518  and  520  so that the ferromagnetic refill layers  518  and  520  longitudinally bias the free layer  152 . In FIG. 14A the first and second ferromagnetic refill layers  614  and  616  interface the first and second hard bias layers  142  and  146  as well as the first and second side surfaces  506  and  508  of the free layer structure so that the free layer structure is longitudinally biased. In FIG. 15A the first and second ferromagnetic refill layers  714  and  716  interface the first and second hard bias layers  142  and  146  as well as the first and second side surfaces  506  and  508  of the free layer structure so that the free layer structure is longitudinally biased. After ion milling in FIG. 17A the first and second hard bias layers  142  and  146  continue to be in engagement with first and second side surfaces of the free layer  152  so as to longitudinally bias the free layer.  
         [0057]    While a preferred material for the ferromagnetic refill layers is nickel iron (NiFe), it should be understood that other ferromagnetic materials may be employed, such as cobalt iron (CoFe), cobalt (Co) or iron nitride (FeN). An exemplary material for the first and second hard bias layers  142  and  146  is cobalt platinum chromium (CoPtCr) and an exemplary material for the pinning layer  156  is platinum manganese (PtMn). In order to provide a sufficient pinning strength the thickness of the platinum manganese should be approximately 150 Å. The layers formed in the various embodiments may be accomplished by well-known sputter deposition techniques. The bilayer photoresist has a thinner lower layer portion which is not closed off during sputtering of the layers. Accordingly, the bilayer photoresist can be lifted off by immersing it in a solvent which dissolves the lower layer portion according to well-known techniques.  
         [0058]    Clearly, other embodiments and modifications of this invention will occur readily to those of ordinary skill in the art in view of these teachings. Therefore, this invention is to be limited only by the following claims, which include all such embodiments and modifications when viewed in conjunction with the above specification and accompanying drawings.