Abstract:
A read sensor for use in a magnetic read head includes a magnetoresistive stack having a plurality of layers, and first and second shield regions positioned adjacent to the magnetoresistive stack. Each of the shield regions includes a first soft magnetic layer for shunting flux from an adjacent track to the shield region instead of the magnetoresistive stack.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    The present invention relates generally to a magnetoresistive sensor for use in a magnetic read head. In particular, the present invention relates to a magnetoresistive read sensor having reduced side-reading.  
           [0002]    Magnetoresistive read sensors, such as giant magnetoresistive (GMR) read sensors, are used in magnetic data storage systems to detect magnetically-encoded information stored on a magnetic data storage medium such as a magnetic disc. A time-dependent magnetic field from a magnetic medium directly modulates the resistivity of the GMR read sensor. A change in resistance of the GMR read sensor can be detected by passing a sense current through the GMR read sensor and measuring the voltage across the GMR read sensor. The resulting signal can be used to recover the encoded information from the magnetic medium.  
           [0003]    A typical GMR read sensor configuration is the GMR spin valve, in which the GMR read sensor is a multi-layered structure formed of a nonmagnetic spacer layer positioned between a ferromagnetic pinned layer and a ferromagnetic free layer. The magnetization of the pinned layer is fixed in a predetermined direction, typically normal to an air bearing surface of the GMR read sensor, while the magnetization of the free layer rotates freely in response to an external magnetic field. The resistance of the GMR read sensor varies as a function of an angle formed between the magnetization direction of the free layer and the magnetization direction of the pinned layer. This multi-layered spin valve configuration allows for a more pronounced magnetoresistive effect, i.e. greater sensitivity and higher total change in resistance, than is possible with anisotropic magnetoresistive (AMR) read sensors, which generally consist of a single ferromagnetic layer.  
           [0004]    GMR spin valves are configured to operate in either a current-in-plane (CIP) mode or a current-perpendicular-to-plane (CPP) mode. In CIP mode, the sense current is passed through in a direction parallel to the layers of the read sensor. In CPP mode, the sense current is passed through in a direction perpendicular to the layers of the read sensor.  
           [0005]    A tunneling magnetoresistive (TMR) read sensor is similar in structure to a GMR spin valve configured in CPP mode, but the physics of the device are different. For a TMR read sensor, rather than using a spacer layer, a barrier layer is positioned between the free layer and the pinned layer. Electrons must tunnel through the barrier layer. A sense current flowing perpendicularly to the plane of the layers of the TMR read sensor experiences a resistance which is proportional to the cosine of an angle formed between the magnetization direction of the free layer and the magnetization direction of the pinned layer.  
           [0006]    One principal concern in the performance of magnetoresistive read sensors is the side-reading effect of the sensor. Current read sensors not only sense magnetic flux from a track located directly beneath the read sensor on the magnetic medium, but they also typically sense magnetic flux from adjacent tracks located up to 3 μ-inches outside the edge of the read sensor. This is known as the side-reading effect and results in an effective increase of up to 6 μ-inches in reader width. This magnetic flux leakage from adjacent tracks limits the read sensor&#39;s ability to accurately sense magnetic flux from the track located directly beneath it. In addition, the effective increase in reader width of the read sensor limits the density of tracks (and thus data) on a magnetic medium.  
           [0007]    The present invention addresses these and other needs, and offers other advantages over current devices.  
         BRIEF SUMMARY OF THE INVENTION  
         [0008]    The present invention is a read sensor for use in a magnetic read head. The read sensor includes a magnetoresistive stack having a plurality of layers, and first and second shield regions positioned adjacent to the magnetoresistive stack. Each of the shield regions includes a first soft magnetic layer for shunting flux from an adjacent track to the shield region instead of the magnetoresistive stack. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIG. 1 is a layer diagram of a first embodiment of a read sensor of the present invention.  
         [0010]    [0010]FIG. 1A is a layer diagram of a second embodiment of a read sensor of the present invention.  
         [0011]    [0011]FIG. 2 is a layer diagram of a third embodiment of a read sensor of the present invention.  
         [0012]    [0012]FIG. 3 is a layer diagram of a fourth embodiment of a read sensor of the present invention.  
         [0013]    [0013]FIG. 4 is a layer diagram of a fifth embodiment of a read sensor of the present invention.  
         [0014]    [0014]FIG. 5 is a layer diagram of a sixth embodiment of a read sensor of the present invention.  
         [0015]    [0015]FIG. 6 is a layer diagram of a seventh embodiment of a read sensor of the present invention.  
         [0016]    [0016]FIG. 7 is a layer diagram of an eighth embodiment of a read sensor of the present invention.  
         [0017]    [0017]FIG. 8 is a layer diagram of a ninth embodiment of a read sensor of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0018]    [0018]FIG. 1 is a layer diagram of a first embodiment of a read sensor  10  of the present invention. Read sensor  10  includes a magnetoresistive stack  11 , shield regions  12 A and  12 B, and contacts  14 A and  14 B. Magnetoresistive stack  11  is a giant magnetoresistive (GMR) stack configured to operate in a current-in-plane (CIP) mode wherein a sense current flows substantially parallel to the layers of the stack. Shield region  12 A is positioned adjacent to a side surface of GMR stack  11 , and includes a permanent magnet layer  16 A, a seed layer  18 A, and a ferromagnetic layer  20 A. Seed layer  18 A is positioned between permanent magnet layer  16 A and ferromagnetic layer  20 A. Shield region  12 B is positioned adjacent to a side surface of GMR stack  11  opposite to shield region  12 A, and includes a permanent magnet layer  16 B, a seed layer  18 B, and a ferromagnetic layer  20 B. Seed layer  18 B is positioned between permanent magnet layer  16 B and ferromagnetic layer  20 B. Contact  14 A is positioned adjacent to ferromagnetic layer  20 A, and contact  14 B is positioned adjacent to ferromagnetic layer  20 B.  
         [0019]    Contacts  14 A and  14 B provide a sense current through GMR stack  11 . The GMR signal produced by GMR stack  11  is generated by the sense current flowing parallel to the layers of GMR stack  11 . Permanent magnet layers  16 A and  16 B are preferably selected from the group consisting of CoPt, CoCrPt and SmCo, and preferably have a thickness in the range of about 100 Å to about 300 Å. Seed layers  18 A and  18 B are preferably selected from the group consisting of Ti, Rh, Ta, Cu, Au and Ru, and preferably have a thickness in the range of about 30 Å to about 50 Å. Ferromagnetic layers  20 A and  20 B are preferably selected from the group consisting of NiFe, CoFe, CoZrNb, CoZrTi and NiFeX, where X is selected from the group consisting of Co, Cr, Rh, Re, Nb, Ta, Ti, V, Hf, W and Ru, and preferably have a thickness in the range of about 15 Å to about 60 Å. Ferromagnetic layers  20 A and  20 B shunt flux from an adjacent track to shield regions  12 A and  12 B, respectively, instead of GMR stack  11 . This reduces the side-reading effect of read sensor  10 , and causes an effective decrease in reader width of read sensor  10 . Seed layers  18 A and  18 B decouple the exchange between permanent magnet layers  16 A and  16 B and ferromagnetic layers  20 A and  20 B, respectively. Contacts  14 A and  14 B overlap ferromagnetic layers  20 A and  20 B, respectively, and effectively eliminate a magnetoresistive effect from ferromagnetic layers  20 A and  20 B.  
         [0020]    [0020]FIG. 1A is a layer diagram of a second embodiment of a read sensor  10 ′ of the present invention. Read sensor  10 ′ is similar to read sensor  10  of FIG. 1. Magnetoresistive stack  11 ′, however, differs from magnetoresistive stack II of FIG. 1 in that magnetoresistive stack  11 ′ is either a GMR stack or a tunneling magnetoresistive (TMR) stack configured to operate in a current-perpendicular-to-plane (CPP) mode wherein a sense current flows substantially perpendicular to the layers of the stack. Contact  14 A′ is positioned adjacent to a top surface of magnetoresistive stack  11 ′, and contact  14 B′ is positioned adjacent to a bottom surface of magnetoresistive stack  11 ′ opposite to contact  14 A′. In addition, an oxide insulation layer  22 A is positioned between magnetoresistive stack  11 ′ and shield region  12 A, and an oxide insulation layer  22 B is positioned between magnetoresistive stack  11 ′ and shield region  12 B.  
         [0021]    [0021]FIG. 2 is a layer diagram of a third embodiment of a read sensor  10 ″ of the present invention. Read sensor  10 ″ is similar to read sensor  10  of FIG. 1. Shield regions  12 A′ and  12 B′, however, differ from shield regions  12 A and  12 B of FIG. 1 in that permanent magnet layer  16 A′ includes an antiferromagnetic layer  24 A and a ferromagnetic layer  26 A, and permanent magnet layer  16 B′ includes an antiferromagnetic layer  24 B and a ferromagnetic layer  26 B. Antiferromagnetic layer  24 A is exchange coupled to ferromagnetic layer  26 A to fix the magnetization of ferromagnetic layer  26 A, and together function as a permanent magnet layer. Similarly, antiferromagnetic layer  24 B is exchange coupled to ferromagnetic layer  26 B to fix the magnetization of ferromagnetic layer  26 B, and together function as a permanent magnet layer.  
         [0022]    [0022]FIG. 3 is a layer diagram of a fourth embodiment of a read sensor  30  of the present invention. Read sensor  30  includes a magnetoresistive stack  31 , shield regions  32 A and  32 B, and contacts  34 A and  34 B. Magnetoresistive stack  31  is a giant magnetoresistive (GMR) stack configured to operate in a current-in-plane (CIP) mode wherein a sense current flows substantially parallel to the layers of the stack. Shield region  32 A is positioned adjacent to a side surface of GMR stack  31 , and includes a ferromagnetic layer  36 A, a seed layer  38 A, and a permanent magnet layer  40 A. Seed layer  38 A is positioned between ferromagnetic layer  36 A and permanent magnet layer  40 A. Shield region  32 B is positioned adjacent to a side surface of GMR stack  31  opposite to shield region  32 A, and includes a ferromagnetic layer  36 B, a seed layer  38 B, and a permanent magnet layer  40 B. Seed layer  38 B is positioned between ferromagnetic layer  36 B and permanent magnet layer  40 B. Contact  34 A is positioned adjacent to permanent magnet layer  40 A, and contact  34 B is positioned adjacent to permanent magnet layer  40 B.  
         [0023]    Contacts  34 A and  34 B provide a sense current through GMR stack  31 . The GMR signal produced by GMR stack  31  is generated by the sense current flowing parallel to the layers of GMR stack  31 . Ferromagnetic layers  36 A and  36 B are preferably selected from the group consisting of NiFe, CoFe, CoZrNb, CoZrTi and NiFeX, where X is selected from the group consisting of Co, Cr, Rh, Re, Nb, Ta, Ti, V, Hf, W and Ru, and preferably have a thickness in the range of about 15 Å to about 60 Å. Seed layers  38 A and  38 B are preferably selected from the group consisting of Ti, Rh, Ta, Cu, Au and Ru, and preferably have a thickness in the range of about 30 Å to about 50 Å. Permanent magnet layers  40 A and  40 B are preferably selected from the group consisting of CoPt, CoCrPt and SmCo, and preferably have a thickness in the range of about 100 Å to about 300 Å. Ferromagnetic layers  36 A and  36 B shunt flux from an adjacent track to shield regions  32 A and  32 B, respectively, instead of GMR stack  31 . This reduces the side-reading effect of read sensor  30 , and causes an effective decrease in reader width of read sensor  30 . Seed layers  38 A and  38 B decouple the exchange between ferromagnetic layers  36 A and  36 B and permanent magnet layers  40 A and  40 B, respectively.  
         [0024]    In view of FIG. 1A, read sensor  30  would also function similarly if magnetoresistive stack  31  were either a GMR stack or a tunneling magnetoresistive (TMR) stack configured to operate in a current-perpendicular-to-plane (CPP) mode wherein a sense current flows substantially perpendicular to the layers of the stack. In both instances, contact  34 A would be positioned adjacent to a top surface of magnetoresistive stack  31 , and contact  34 B would be positioned adjacent to a bottom surface of magnetoresistive stack  31  opposite to contact  34 A. In addition, a layer of oxide insulation would be positioned between magnetoresistive stack  31  and each of shield regions  32 A and  32 B.  
         [0025]    [0025]FIG. 4 is a layer diagram of a fifth embodiment of a read sensor  30 ′ of the present invention. Read sensor  30 ′ is similar to read sensor  30  of FIG. 3. Shield regions  32 A′ and  32 B′, however, differ from shield regions  32 A and  32 B of FIG. 3 in that permanent magnet layer  40 A′ includes an antiferromagnetic layer  42 A and a ferromagnetic layer  44 A, and permanent magnet layer  40 B′ includes an antiferromagnetic layer  42 B and a ferromagnetic layer  44 B. Antiferromagnetic layer  42 A is exchange coupled to ferromagnetic layer  44 A to fix the magnetization of ferromagnetic layer  44 A, and together function as a permanent magnet layer. Similarly, antiferromagnetic layer  42 B is exchange coupled to ferromagnetic layer  44 B to fix the magnetization of ferromagnetic layer  44 B, and together function as a permanent magnet layer.  
         [0026]    [0026]FIG. 5 is a layer diagram of a sixth embodiment of a read sensor  50  of the present invention. Read sensor  50  includes a magnetoresistive stack  51 , shield regions  52 A and  52 B, and contacts  54 A and  54 B. Magnetoresistive stack  51  is a giant magnetoresistive (GMR) stack configured to operate in a current-in-plane (CIP) mode wherein a sense current flows substantially parallel to the layers of the stack. Shield region  52 A is positioned adjacent to a side surface of GMR stack  51 , and includes a first ferromagnetic layer  56 A, a first seed layer  58 A, a permanent magnet layer  60 A, a second seed layer  62 A, and a second ferromagnetic layer  64 A. First seed layer  58 A is positioned between first ferromagnetic layer  56 A and permanent magnet layer  60 A, and second seed layer  62 A is positioned between permanent magnet layer  60 A and second ferromagnetic layer  64 A. Shield region  52 B is positioned adjacent to a side surface of GMR stack  51  opposite to shield region  52 B, and includes a first ferromagnetic layer  56 B, a first seed layer  58 B, a permanent magnet layer  60 B, a second seed layer  62 B, and a second ferromagnetic layer  64 B. First seed layer  58 B is positioned between first ferromagnetic layer  56 B and permanent magnet layer  60 B, and second seed layer  62 B is positioned between permanent magnet layer  60 B and second ferromagnetic layer  64 B. Contact  54 A is positioned adjacent to second ferromagnetic layer  64 A, and contact  54 B is positioned adjacent to second ferromagnetic layer  64 B.  
         [0027]    Contacts  54 A and  54 B provide a sense current through GMR stack  51 . The GMR signal produced by GMR stack  51  is generated by the sense current flowing parallel to the layers of GMR stack  51 . Ferromagnetic layers  56 A,  56 B,  64 A and  64 B are preferably selected from the group consisting of NiFe, CoFe, CoZrNb, CoZrTi and NiFeX, where X is selected from the group consisting of Co, Cr, Rh, Re, Nb, Ta, Ti, V, Hf, W and Ru, and preferably have a thickness in the range of about 15 Å to about 60 Å. Seed layers  58 A,  58 B,  62 A and  62 B are preferably selected from the group consisting of Ti, Rh, Ta, Cu, Au and Ru, and preferably have a thickness in the range of about 30 Å to about 50 Å. Permanent magnet layers  60 A and  60 B are preferably selected from the group consisting of CoPt, CoCrPt and SmCo, and preferably have a thickness in the range of about 100 Å to about 300 Å. Ferromagnetic layers  56 A,  56 B,  64 A and  64 B shunt flux from an adjacent track to shield regions  52 A and  52 B instead of GMR stack  51 . This reduces the side-reading effect of read sensor  50 , and causes an effective decrease in reader width of read sensor  50 . First seed layers  58 A and  58 B decouple the exchange between first ferromagnetic layers  56 A and  56 B and permanent magnet layers  60 A and  60 B, respectively. Second seed layers  62 A and  62 B decouple the exchange between permanent magnet layers  60 A and  60 B and second ferromagnetic layers  64 A and  64 B, respectively. Contacts  54 A and  54 B overlap second ferromagnetic layers  64 A and  64 B, respectively, and effectively eliminate a magnetoresistive effect from second ferromagnetic layers  64 A and  64 B.  
         [0028]    In view of FIG. 1A, read sensor  50  would also function similarly if magnetoresistive stack  51  were either a GMR stack or a tunneling magnetoresistive (TMR) stack configured to operate in a current-perpendicular-to-plane (CPP) mode wherein a sense current flows substantially perpendicular to the layers of the stack. In both instances, contact  54 A would be positioned adjacent to a top surface of magnetoresistive stack  51 , and contact  54 B would be positioned adjacent to a bottom surface of magnetoresistive stack  51  opposite to contact  54 A. In addition, a layer of oxide insulation would be positioned between magnetoresistive stack  51  and each of shield regions  52 A and  52 B.  
         [0029]    [0029]FIG. 6 is a layer diagram of a seventh embodiment of a read sensor  70  of the present invention. Read sensor  70  includes a magnetoresistive stack  71 , shield regions  72 A and  72 B, and contacts  74 A and  74 B. Magnetoresistive stack  71  is a giant magnetoresistive (GMR) stack configured to operate in a current-in-plane (CIP) mode wherein a sense current flows substantially parallel to the layers of the stack. Shield region  72 A is positioned adjacent to a side surface of GMR stack  71 , and includes a first ferromagnetic layer  76 A, a first seed layer  78 A, a first permanent magnet layer  80 A, a second seed layer  82 A, a second ferromagnetic layer  84 A, a third seed layer  86 A, a second permanent magnet layer  88 A, a fourth seed layer  90 A, and a third ferromagnetic layer  92 A. First seed layer  78 A is positioned between first ferromagnetic layer  76 A and first permanent magnet layer  80 A, second seed layer  82 A is positioned between first permanent magnet layer  80 A and second ferromagnetic layer  84 A, third seed layer  86 A is positioned between second ferromagnetic layer  84 A and second permanent magnet layer  88 A, and fourth seed layer  90 A is positioned between second permanent magnet layer  88 A and third ferromagnetic layer  92 A. Shield region  72 B is positioned adjacent to a side surface of GMR stack  71  opposite to shield region  72 A, and includes a first ferromagnetic layer  76 B, a first seed layer  78 B, a first permanent magnet layer  80 B, a second seed layer  82 B, a second ferromagnetic layer  84 B, a third seed layer  86 B, a second permanent magnet layer  88 B, a fourth seed layer  90 B, and a third ferromagnetic layer  92 B. First seed layer  78 B is positioned between first ferromagnetic layer  76 B and first permanent magnet layer  80 B, second seed layer  82 B is positioned between first permanent magnet layer  80 B and second ferromagnetic layer  84 B, third seed layer  86 B is positioned between second ferromagnetic layer  84 B and second permanent magnet layer  88 B, and fourth seed layer  90 B is positioned between second permanent magnet layer  88 B and third ferromagnetic layer  92 B. Contact  74 A is positioned adjacent to third ferromagnetic layer  92 A, and contact  74 B is positioned adjacent to third ferromagnetic layer  92 B.  
         [0030]    Contacts  74 A and  74 B provide a sense current through GMR stack  71 . The GMR signal produced by GMR stack  71  is generated by the sense current flowing parallel to the layers of GMR stack  71 . Ferromagnetic layers  76 A,  76 B,  84 A,  84 B,  92 A and  92 B are preferably selected from the group consisting of NiFe, CoFe, CoZrNb, CoZrTi and NiFeX, where X is selected from the group consisting of Co, Cr, Rh, Re, Nb, Ta, Ti, V, Hf, W and Ru, and preferably have a thickness in the range of about 15 Å to about 60 Å. Seed layers  78 A,  78 B,  82 A,  82 B,  86 A,  86 B,  90 A and  90 B are preferably selected from the group consisting of Ti, Rh, Ta, Cu, Au and Ru, and preferably have a thickness in the range of about 30 Å to about 50 Å. Permanent magnet layers  80 A,  80 B,  88 A and  88 B are preferably selected from the group consisting of CoPt, CoCrPt and SmCo, and preferably have a thickness in the range of about 100 Å to about 300 Å. Ferromagnetic layers  76 A,  76 B,  84 A,  84 B,  92 A and  92 B shunt flux from an adjacent track to shield regions  72 A and  72 B instead of GMR stack  71 . This reduces the side-reading effect of read sensor  70 , and causes an effective decrease in reader width of read sensor  70 . First seed layers  78 A and  78 B decouple the exchange between first ferromagnetic layers  76 A and  76 B and first permanent magnet layers  80 A and  80 B, respectively. Second seed layers  82 A and  82 B decouple the exchange between first permanent magnet layers  80 A and  80 B and second ferromagnetic layers  84 A and  84 B, respectively. Third seed layers  86 A and  86 B decouple the exchange between second ferromagnetic layers  84 A and  84 B and second permanent magnet layers  88 A and  88 B, respectively. Fourth seed layers  90 A and  90 B decouple the exchange between second permanent magnet layers  88 A and  88 B and third ferromagnetic layers  92 A and  92 B, respectively. Contacts  74 A and  74 B overlap third ferromagnetic layers  92 A and  92 B, respectively, and effectively eliminate a magnetoresistive effect from third ferromagnetic layers  92 A and  92 B.  
         [0031]    In view of FIG. 1A, read sensor  70  would also function similarly if magnetoresistive stack  71  were either a GMR stack or a tunneling magnetoresistive (TMR) stack configured to operate in a current-perpendicular-to-plane (CPP) mode wherein a sense current flows substantially perpendicular to the layers of the stack. In both instances, contact  74 A would be positioned adjacent to a top surface of magnetoresistive stack  71 , and contact  74 B would be positioned adjacent to a bottom surface of magnetoresistive stack  71  opposite to contact  74 A. In addition, a layer of oxide insulation would be positioned between magnetoresistive stack  71  and each of shield regions  72 A and  72 B.  
         [0032]    [0032]FIG. 7 is a layer diagram of an eighth embodiment of a read sensor  100  of the present invention. Read sensor  100  includes a magnetoresistive stack  101 , shield regions  102 A and  102 B, and contacts  104 A and  104 B. Magnetoresistive stack  101  is a giant magnetoresistive (GMR) stack configured to operate in a current-in-plane (CIP) mode wherein a sense current flows substantially parallel to the layers of the stack. Shield region  102 A is positioned adjacent to a side surface of GMR stack  101 , and includes a ferromagnetic layer  106 A, a seed layer  108 A, and a permanent magnet layer  110 A. Ferromagnetic layer  106 A is positioned adjacent to GMR stack  101  and along a bottom surface of shield region  102 A. Seed layer  108 A is positioned between ferromagnetic layer  106 A and permanent magnet layer  110 A. Shield region  102 B is positioned adjacent to a side surface of GMR stack  101  opposite to shield region  102 A, and includes a ferromagnetic layer  106 B, a seed layer  108 B, and a permanent magnet layer  10 B. Ferromagnetic layer  106 B is positioned adjacent to GMR stack  101  and along a bottom surface of shield region  102 B. Seed layer  108 B is positioned between ferromagnetic layer  106 B and permanent magnet layer  110 B. Contact  104 A is positioned adjacent to permanent magnet layer  110 A, and contact  104 B is positioned adjacent to permanent magnet layer  110 B.  
         [0033]    Contacts  104 A and  104 B provide a sense current through GMR stack  101 . The GMR signal produced by GMR stack  101  is generated by the sense current flowing parallel to the layers of GMR stack  101 . Ferromagnetic layers  106 A and  106 B are preferably selected from the group consisting of NiFe, CoFe, CoZrNb, CoZrTi and NiFeX, where X is selected from the group consisting of Co, Cr, Rh, Re, Nb, Ta, Ti, V, Hf, W and Ru, and preferably have a thickness in the range of about 15 Å to about 60 Å. Seed layers  108 A and  108 B are preferably selected from the group consisting of Ti, Rh, Ta, Cu, Au and Ru, and preferably have a thickness in the range of about 30 Å to about 50 Å. Permanent magnet layers  110 A and  110 B are preferably selected from the group consisting of CoPt, CoCrPt and SmCo, and preferably have a thickness in the range of about 100 Å to about 300 Å. Ferromagnetic layers  106 A and  106 B shunt flux from an adjacent track to shield regions  102 A and  102 B, respectively, instead of GMR stack  101 . This reduces the side-reading effect of read sensor  100 , and causes an effective decrease in reader width of read sensor  100 . Seed layers  108 A and  108 B decouple the exchange between ferromagnetic layers  106 A and  106 B and permanent magnet layers  110 A and  110 B, respectively.  
         [0034]    [0034]FIG. 8 is a layer diagram of a ninth embodiment of a read sensor  100 ′ of the present invention. Read sensor  100 ′ is similar to read sensor  100  of FIG. 7. Magnetoresistive stack  101 ′, however, differs from magnetoresistive stack  101  of FIG. 7 in that magnetoresistive stack  101 ′ is either a GMR stack or a tunneling magnetoresistive (TMR) stack configured to operate in a current-perpendicular-to-plane (CPP) mode wherein a sense current flows substantially perpendicular to the layers of the stack. Contact  104 A′ is positioned adjacent to a top surface of magnetoresistive stack  101 ′, and contact  104 B′ is positioned adjacent to a bottom surface of magnetoresistive stack  101 ′ opposite to contact  14 A′. In addition, an oxide insulation layer  112 A is positioned between magnetoresistive stack  101 ′ and shield region  102 A, as well as adjacent to a bottom surface of shield region  102 A. Similarly, an oxide insulation layer  112 B is positioned between magnetoresistive stack  101 ′ and shield region  102 B, as well as adjacent to a bottom surface of shield region  102 B.  
         [0035]    Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.