Abstract:
A current-perpendicular-to-plane (CPP) spin valve (SV) sensor and fabrication method with a contiguous junction type geometry that increases sensor resistance by up to two orders of magnitude over conventional CPP GMR geometry for a particular track read-width. The superior CPP GMR coefficient (δr/R) is implemented at an increased sensor resistance by using two small self-aligned SV stacks disposed with the sense current flowing perpendicular thereto when also flowing parallel to the free layer deposition plane. With the CPP geometry of this invention, thicker conductive spacer layers may be used without unacceptable sense current shunting, so the two self-aligned SV stacks may be completed following the free-layer track-mill step. The two SV stacks may be connected in parallel or back-to-back in series to provide different sense voltages.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates generally to giant magnetoresistive (GMR) spin valve (SV) sensors and more particularly to a high-sensitivity self-aligned lateral current-perpendicular-to-plane (CPP) dual-SV sensor geometry and fabrication method. 
     2. Description of the Related Art 
     Computers often include auxiliary memory storage devices having media on which data can be written and from which data can be read. A direct access storage device (DASD) or disk drive incorporating rotating magnetic disks is commonly used for storing data in magnetic form in concentric, radially-spaced tracks on the disk surfaces. Magnetic heads including read sensors are then used to read data from the tracks on the disk surfaces. 
     In high capacity disk drives, magnetoresistive (MR) read sensors (MR heads) are preferred in the art because of their capability to read data at greater track and linear densities than earlier thin film inductive heads. An MR sensor detects the magnetic data on a disk surface through changes in the MR sensing layer resistance, which are responsive to changes in the magnetic flux sensed by the MR layer. 
     The early MR sensors rely on the anisotropic MR (AMR) effect in which an MR element resistance varies as the square of the cosine of the angle between the magnetic moment of the MR element and the direction of sense current flowing through the MR element. Recorded data can be read from a magnetic medium because the external magnetic field from the recorded magnetic medium (the signal field) changes the moment direction in the MR element, thereby changing the MR element resistance and the sense current or voltage. 
     The later giant magnetoresistance (GMR) sensor relies on the spin-scattering effect. The chief source of the GMR effect is “spin-dependent” scattering of electrons. In GMR sensors, the resistance varies as a function of the spin-dependent scattering of the conduction electrons across two magnetic layers separated by a non-magnetic spacer layer. The spin-dependent scattering occurs at the interface of the magnetic and nonmagnetic layers and within the magnetic layers. Electrical resistance is affected by scattering of electrons moving through a material. Depending on the direction of its magnetic moment, a single-domain magnetic material scatters electrons with “up” or “down” spin differently. When the free and pinned magnetic layers in a GMR structure are aligned anti-parallel, the resistance is high because “up” electrons that are not scattered in one layer may be scattered in the other. When the layers are aligned in parallel, scattering is reduced for all of the “up” electrons, regardless of which layer they pass through, yielding a lower resistance. GMR sensors using only two layers of ferromagnetic (FM) material separated by a thin layer of non-magnetic conductive material (e.g., copper) are generally referred to in the art as spin valve (SV) sensors. 
     The sense current-in-plane (CIP) SV sensor is well-known in the art and includes a nonmagnetic electrically conductive spacer layer sandwiched between a FM pinned layer structure and a FM free layer structure. An antiferromagnetic (AF) pinning layer interfaces the pinned layer structure for pinning a magnetic moment of the pinned layer structure  90 E to an air bearing surface (ABS), which is an exposed surface of the sensor that faces the magnetic disk. Two sense current lead conductors are connected on each side of the layered SV structure to conduct sense current in the plane of the several layers. The magnetic moment of the free layer structure is free to rotate upwardly and downwardly with respect to the ABS from a quiescent position or bias point in response to positive and negative magnetic field signals present on the surface of an adjacent rotating magnetic disk. The quiescent position, which is preferably parallel to the ABS, is the position of the magnetic moment of the free layer structure with the operating-bias sense current conducted through the sensor in the absence of external magnetic fields. 
     The spacer layer thickness is chosen to minimize the shunting of the CIP sense current and the magnetic coupling between the free and pinned layer structures. 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 conductive spacer layer interfaces with the pinned and free layer structures. Such scattering is minimal when the pinned and free layer magnetic moments are parallel with one another, and increases substantially when the magnetic moments are antiparallel. Because changes in scattering affects the SV sensor resistance, the sensor resistance varies as a weighted function of cos θ, where θ is the relative angle between the magnetic moments of the pinned and free layer structures. SV sensor sensitivity is quantified in terms of the MR coefficient, δr/R, where R is the sensor resistance when the magnetic moments are parallel and δr is the change in the sensor resistance arising from shifting the moments into an antiparallel position. 
     The sensitivity of a SV sensor depends upon the response of the free layer to external magnetic field signals from the surface of a rotating magnetic disk. The magnetic moment of the free layer depends upon the material or materials employed for the free layer. The responsiveness of the free layer decreases as the magnetic moment of the free layer increases. Reduced responsiveness means the free layer magnetic moment cannot rotate as far from its parallel position to the ABS for a given external magnetic field level, which reduces sensor signal output. Also, improved isolation of the free layer structure from the pinned layer structure usually requires a thicker intermediate conductive layer, which shunts sense current away from the FM layers, thereby reducing sensor resistance and sensitivity. 
     For example,  FIG. 1  shows an ABS view (disposed for vertical relative medium motion) of a typical CIP SV sensor  20  from the prior art that is stabilized using the hard magnetic (HM) layers  22  formed by a lift-off process. SV sensor  20  is usually fabricated using thin-film deposition techniques known in the art. For example, a first shield (S 1 ) layer  24  of a conductive material is formed on a substrate (not shown) and an insulating layer  26  of alumina, or the like, is deposited over S 1  layer  24 . The SV layers are then deposited in sequence over insulating layer  26 . For example, the AFM pinning layer  28  is deposited followed by the FM pinned layer  30  to form a pinned layer structure. Next, the conductive spacer layer  32  of copper, or the like, is deposited followed by the FM free layer  34 . Finally, a photoresist layer (not shown) is formed over the entire assembly and is processed in the usual manner to permit all material outside of the central (read-width) region  36  to be removed by etching down to insulating layer  26  (the “track-mill” step). After etching, a HM material is deposited over the exposed portions of insulating layer  26  and also over the remaining photoresist layer (not shown) in central region  36  and, before removing the photoresist layer covering central region  36 , a conductive lead layer  38  is deposited over everything. The photoresist layer is then finally dissolved away, which “lifts off” the unwanted portions (not shown) of the HM layer  22  and lead layer  26  within central region  36 , in a well-known manner. Because of this lift-off deposition procedure, the later layers are tapered to a very slight thickness at the junction with central region  36 . The sense current (not shown) flows parallel to the plane of layers  28 – 34  from one side of lead layer  38  to the other, so the (fixed) conductivity of conductive spacer layer  32  reduces the GMR effect of scatter-dependent conductivity of MR layers  30  and  34 . 
     As an alternative to the CIP structure, the sense current lead conductors may be arranged so that the sensing current passes through the sensor perpendicular to the plane of the layers, which is known in the art as current-perpendicular-to-plane (CPP) geometry. In an early paper, [AA New Design for an Ultra-High Density Magnetic Recording Head Using a GMR Sensor In the CPP Mode,” Rottmayer, R. and Zhu, J.;  IEEE Transactions on Magnetics , Vol. 31, No. 6, November 1995], Rottmayer et al. propose a GMR multilayer read element within a write head gap that operates in the CPP mode and is biased by an exchange coupled soft film acting like a permanent magnet while distinguishing conventional MR and SV head designs. Their read element has a repeated multilayer structure (to increase GMR sensitivity) that is quite different from the GMR SV stack later introduced in the art. 
     For example,  FIG. 2  shows a partial ABS view (disposed for vertical relative medium motion) of a typical CPP SV sensor  40  from the prior art. Sensor  40  includes a substrate  42  with an overlying underlayer  44 . In turn, an insulating gap layer  46  overlies underlayer  44 . A first magnetic shield (S 1 ) layer  48  overlies gap layer  46  substantially as shown. An optional gap layer  50 , which may include aluminum-oxide (Al 2 O 3 ) or silicon-dioxide(SiO 2 ), may be formed upon first magnetic shield (S 1 ) layer  48 . The S 1  &amp; S 2  shield layers may include nickel iron (NiFe), cobalt-zirconium-tantalum (CoZrTa), iron-nitride (FeN) or any other useful soft magnetic materials or their alloys, and may be about 2 microns or less in thickness. Gap layer  50  may be from about 10 to about 100 nanometers in thickness. A first lead (L 1 ) layer  52  is formed on top of gap layer  50 . First lead (L 1 ) layer  52  may include between 10 and 100 nanometers in thickness of rhodium (Rh), aluminum (Al), gold (Au), tantalum (Ta) or silver (Ag) or their alloys. A FM free layer  54  overlies first lead (L 1 ) layer  52 . A non-magnetic conductive spacer layer  56 , usually copper (Cu), overlies free layer  54  and a pinned layer  58  is formed on top of spacer layer  56 . A pinning layer  60  overlies pinned layer  58  and a second lead (L 2 ) layer  62 , of material similar to that used to produce first lead layer  52 , is formed thereon. First and second lead layers  52 ,  62  in conjunction with free layer  54 , spacer layer  56 , pinned layer  58  and pinning layer  60  together make up the SV stack  64 , substantially as shown. An optional gap layer  66  may overly second lead (L 2 ) layer  62  to isolate therefrom the second magnetic shield (S 2 )  68 . A dielectric gap material  70  surrounds SV stack  64  and portions of first (L 1 ) and second (L 2 ) lead layers  52 ,  62  substantially as shown. The sense current (not shown) flows perpendicular to the plane of layers  94 – 100  from one to the other of lead layers  52 ,  62 . The inverted SV structure wherein pinning layer  60  and pinned FM layer  58  underlie active FM layer  54 , may be used instead of the more conventional arrangement of active and pinned layers shown. 
     By passing the sense current through SV stack  64  perpendicularly to the plane of layers  54 – 60 , the spin-dependent scattering effect may be exploited while eliminating the effect of the in-plane current usually shunted through the non-magnetic layers such as conductive spacer layer  56 . It has been demonstrated that the CPP GMR coefficient (δr/R) is accordingly larger than the CIP GMR coefficient. However, because the film layers  54 – 60  are quite thin, they have a low resistance perpendicular to their plane (even with modem read-width and throat-height dimensions of about 500 nm) and the series resistance of first (L 1 ) and second (L 2 ) lead layers  52 ,  62  significantly reduces the sensitivity of the CPP SV sensor over what could otherwise be available. This is true with read-width (RW) and throat-height (TH) dimensions of about 500 nm each and is likely to remain so until these dimensions are reduced by an order of magnitude. 
     Practitioners in the art have proposed various useful solutions to the CPP SV resistance problem; some proposing to reduce the lead resistance and others proposing to increase the effective CPP SV stack resistance. For example, in U.S. Pat. No. 6,134,089, Ronald Barr et al. disclose a technique for reducing sense lead conductor resistance to better exploit the little resistance available in the CPP GMR stack. In U.S. Pat. No, 6,198,609, Ronald Barr et al. disclose a fabrication technique for increasing stack resistance by preventing sense current shunting at the edges of the CPP GMR stack, thereby improving sensitivity. In U.S. Pat. 5,668,688, John Dykes et al. propose increasing stack resistance by using two SV stacks in series to provide an enhanced δr/R response said to be twice that seen for CIP SV geometries. Moreover, in U.S. Pat. No. 6,233,125, Kenneth Knapp et al. disclose a CPP MR read sensor that is formed in a groove between two conductors by a method results in the sense current passing twice through the MR thickness, thereby doubling the sensor CPP SV stack resistance. Although these proposals do improve exploitation of the inherently better CPP GMR sensitivity by enhancing CPP resistance in different ways, most of these proposed solutions require much more elaborate fabrication procedures than do the simpler CIP SV sensor. 
     Thus, the larger CPP GMR effect (δr/R) does not readily result in the expected improvement in GMR sensor signal amplitude over CIP SV geometries because the CPP SV resistances are so much lower than the corresponding CIP SV sensor resistances, leading to lower voltage drops for given sense current amplitudes. These unresolved problems and deficiencies are clearly felt in the art and are solved by this invention in the manner described below. 
     SUMMARY OF THE INVENTION 
     This invention solves the above problem with a current-perpendicular-to-plane (CPP) spin valve (SV) sensor and fabrication method using a contiguous junction type geometry that increases sensor resistance by up to two orders of magnitude over conventional CPP GMR geometry for a particular track read-width. 
     It is a purpose of this invention to exploit the superior CPP GMR coefficient (δr/R) at an increased sensor resistance by using at least two small self-aligned SV stacks disposed with the sense current flowing perpendicular thereto when also flowing parallel to the free layer deposition plane. It is an advantage of the sensor fabrication method of this invention that a thicker conductive spacer layer may be used without unacceptable sense current shunting so the self-aligned SV stacks may be completed following the free-layer track-mill step. 
     In one aspect, the invention is a method of making a sense CPP SV sensor for sensing changes in an external magnetic field at an air bearing surface (ABS), including the steps of forming a ferromagnetic (FM) free layer having a center region disposed at the ABS, removing the free layer on two sides to leave the center region between two edges, forming a nonmagnetic conductive spacer layer on each side of the free layer center region over the free layer edges, forming a FM pinned layer structure having a magnetic moment on each side of the free layer center region over the nonmagnetic conductive spacer layer, forming an antiferromagnetic (AF) pinning layer on each side of the free layer center region exchange-coupled to the pinned layer structure for pinning the magnetic moment thereof and forming a first conductive lead layer on each side of the free layer center region over and in conductive contact with the pinned layer structure. 
     In another aspect, the invention is a method of making magnetic head assembly that has an ABS, including the steps of making a write head by forming FM first and second pole piece layers in pole tip, yoke and back gap regions wherein the yoke region is located between the pole tip and back gap regions, forming a nonmagnetic nonconductive write gap layer between the first and second pole piece layers in the pole tip region, forming an insulation stack with at least one coil layer embedded therein between the first and second pole piece layers in the yoke region, and connecting the first and pole piece layers at the back gap region; and making a read head by forming nonmagnetic nonconductive first and second read gap layers between the first shield layer and the first pole piece layer and forming a sense CPP SV sensor between the first and second read gap layers by forming a FM free layer having a center region disposed at the ABS, removing the free layer on two sides to leave the center region between two edges, forming a nonmagnetic conductive spacer layer on each side of the free layer center region over the free layer edges, forming a FM pinned layer structure having a magnetic moment on each side of the free layer center region over the nonmagnetic conductive spacer layer, forming an AF pinning layer on each side of the free layer center region exchange-coupled to the pinned layer structure for pinning the magnetic moment thereof, and forming a first conductive lead layer on each side of the free layer center region over and in conductive contact with the pinned layer structure. 
     In an exemplary embodiment, the invention is a magnetic read head for reading changes in an external magnetic field at an ABS, including a sense CPP SV sensor with a FM free layer having a center region disposed at the ABS to couple responsively to the external magnetic field, a first conductive lead layer disposed on each side of the center region for conducting the sense current, a FM pinned layer structure having a magnetic moment disposed at the ABS between the first conductive lead layer and the free layer on each side of the center region, a nonmagnetic conductive spacer layer disposed at the ABS between the pinned layer structure and the free layer on each side of the center region, and an AF pinning layer exchange-coupled to the pinned layer structure for pinning the magnetic moment thereof. 
     In yet another aspect, the invention is a magnetic head assembly having an ABS, with a write head including FM first and second pole piece layers that have a yoke portion located between a pole tip portion and a back gap portion, the first and second pole piece layers being connected at their back gap portions, a nonmagnetic write gap layer located between the pole tip portions of the first and second pole piece layers, and an insulation stack with at least one coil layer embedded therein located between the yoke portions of the first and second pole piece layers; and a read head including a FM first shield layer, nonmagnetic nonconductive first and second read gap layers disposed between the first shield layer and the first pole piece layer, and a CPP SV sensor disposed at the ABS between the first and second read gap layers, having a FM free layer with a center region disposed at the ABS to couple responsively to the external magnetic field, a first conductive lead layer disposed on each side of the center region for conducting the sense current, a FM pinned layer structure having a magnetic moment disposed at the ABS between the first conductive lead layer and the free layer on each side of the center region, a nonmagnetic conductive spacer layer disposed at the ABS between the pinned layer structure and the free layer on each side of the center region, and an AF pinning layer exchange-coupled to the pinned layer structure for pinning the magnetic moment thereof. 
     The foregoing, together with other objects, features and advantages of this invention, can be better appreciated with reference to the following specification, claims and the accompanying drawing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a more complete understanding of this invention, reference is now made to the following detailed description of the embodiments as illustrated in the accompanying drawing, in which like reference designations represent like features throughout the several views and wherein: 
         FIG. 1  is a schematic diagram illustrating part of the air-bearing surface (ABS) of a typical current-in-plane (CIP) spin valve (SV) sensor embodiment from the prior art; 
         FIG. 2  is a schematic diagram illustrating part of the ABS view of a typical current perpendicular-to-the-plane (CPP) SV sensor embodiment from the prior art; 
         FIG. 3  is a schematic diagram illustrating part of the ABS view of a basic embodiment of the CPP SV sensor of this invention; 
         FIG. 4  is a schematic diagram illustrating part of the ABS view of an alternative stabilized embodiment of the CPP SV sensor of this invention; 
         FIG. 5  is a schematic diagram illustrating part of the ABS view of an alternative self-stabilized embodiment of the CPP SV sensor of this invention; 
         FIG. 6  is a block diagram of a flow chart illustrating an embodiment of the CPP SV sensor fabrication method of this invention; 
         FIG. 7  is a plan view of an exemplary magnetic disk drive; 
         FIG. 8  is an end view of a slider with a magnetic head of the disk drive as seen in plane  8 — 8 ; 
         FIG. 9  is an elevation view of the magnetic disk drive wherein multiple disks and magnetic heads are employed; 
         FIG. 10  is an isometric illustration of an exemplary suspension system for supporting the slider and magnetic head; 
         FIG. 11  is an ABS view of the magnetic head taken along plane  11 — 11  of  FIG. 8 ; 
         FIG. 12  is a partial view of the slider and magnetic head as seen in plane  12 — 12  of  FIG. 8 ; 
         FIG. 13  is a partial ABS view of the slider taken along plane  13 — 13  of  FIG. 12  to show the read and write elements of the magnetic head; and 
         FIG. 14  is a view taken along plane  14 — 14  of  FIG. 12  with all material above the second pole piece removed. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings wherein like reference numerals designate like or similar parts throughout the several views,  FIG. 3  shows a basic embodiment  72  of the current-perpendicular-to-plane (CPP) spin valve (SV) sensor of this invention viewed from the air bearing surface (ABS) and oriented so that in operation the data storage medium moves vertically in the plane of  FIG. 3  with respect to sensor  72 . After forming the ferromagnetic (FM) shield (S 1 ) layer  74  and the nonmagnetic nonconductive read gap layer  76 , instead of the usual SV stack (see, for example, SV stack  64  in  FIG. 2 ), only the ferromagnetic (FM) free layer  78  is formed before performing the track-width mill step to define the center region  80 , which represents the read-width (RW) of sensor  72 , disposed between the free-layer edges  82  &amp;  84 . To do the track-width mill, a photoresist pattern (not shown) is deposited over center region  80  to protect free layer  78  while the unwanted material is etched away from the areas outside of center region  80 . 
     After the track-width mill, a self-aligned structure is deposited to form two SV stacks at each free-layer edge  82  &amp;  84  by virtue of the same photoresist pattern used for the track-width mill. First, a thin nonmagnetic conductive spacer layer  86  is deposited to cover free-layer edges  82  &amp;  84 , using copper (Cu) or other similar material. Although control of the thickness of spacer layer  86  is crucial for minimizing unwanted shunt current in the current-in-plane (CIP) SV stack ( FIG. 1 ), spacer layer  86  thickness is relatively unimportant here. For this reason, the ex-situ deposition of two acceptable-quality SV stacks at free-layer edges  82  &amp;  84  is easily managed using well-known deposition techniques. After depositing spacer layer  86 , the FM pinned layer and pinning layer structures  88  may be deposited using the same track-width mill photoresist pattern. Any useful pinned-pinning layer structure may be used for the CPP SV sensor of this invention. For example, in commonly-assigned U.S. Pat. No. 5,880,913, Gill discloses a SV stack that uses a multiple antiparallel (AP) pinned-layer structure suitable for use with the sensor of this invention. For example, the AP pinned layer structure may include two FM AP pinned layers with the first AP pinned layer interfacing the pinning layer and the second AP pinned layer interfacing the spacer layer and an AP coupling layer located between and interfacing the first and second AP pinned layers. Finally, using the same alignment pattern, the first sense current conductor layer is deposited to form a first lead conductor (L 1 ) layer  90  and a second lead conductor (L 2 ) layer  92 . The photoresist pattern is then lifted off and an insulation layer (not shown) is deposited over the entire structure, unless a second shunt conductor layer  94  is desired. 
     Shunt conductor layer  94  is not necessary to this invention but is preferred for several reasons. It may be easily formed by first patterning and depositing a self-aligned insulating layer  96  on top of lead conductor (L 1  &amp; L 2 ) layers  90  &amp;  92  to isolate them from shunt lead conductor (L 3 ) layer  94 . Shunt lead conductor (L 3 ) layer  94  helps to limit the parasitic resistance arising from center region  80  of free layer  78 , which is contributing very little to the sensor GMR coefficient (δr/R). Shunt lead conductor (L 3 ) layer  94  also helps to reduce joule heating arising from larger sense currents, thereby permitting operation with larger sense voltages. 
     In operation, it may be readily appreciated from the above description of  FIG. 3  that the cross-sectional areas (and resistances) of each SV stack at free-layer edges  82  &amp;  84  are proportional to the product of the stripe height (SH) (along the dimension oriented into the page) and the thickness of free layer  78 . This compares with the cross-sectional area (and resistance) of conventional CPP SV stack  64  in  FIG. 2 , which is proportional to the product of SH and RW. Clearly, the thickness of free layer  78  may be fabricated to be one or more orders of magnitude less than the RW. Thus, the CPP resistance of each SV stack at free-layer edges  82  &amp;  84  can be orders of magnitude more than the CPP resistance of conventional CPP SV stack  64  in  FIG. 2 . This is an important advantage of the sensor of this invention. Furthermore, because sensor  72  provides two SV stacks (at free-layer edges  82  &amp;  84 ) in a single fabrication process, connecting the SV stacks in series doubles the sensor resistance when sense current is conducted from lead conductor (L 1 ) layer  90  to lead conductor (L 2 ) layer  92 . The two SV stacks (at free-layer edges  82  &amp;  84 ) may also be connected in parallel by shorting lead conductor (L 1 ) layer  90  to lead conductor (L 2 ) layer  92  and conducting sense current therefrom to shunt lead conductor (L 3 ) layer  94 , but this configuration reduces sensor resistance by a factor of four. The advantage to parallel SV stack operation is the opportunity to short lead conductor (L 1 /L 2 ) layers  90  &amp;  92  to the shield (S 1 ) layer  74  and to short shunt lead conductor (L 3 ) layer  94  to the upper shield (S 2 ) layer (not shown), provided that the bottom of free layer  78  remains isolated. Such an arrangement permits improved thermal sinking, increased sense current level and eliminates the gap insulation problem known in the art. 
     The CPP SV sensor of this invention may be longitudinally stabilized to suppress Barkhausen noise by using any useful stabilization technique known in the art. For example, in  FIG. 4 , a hard-stabilized CPP SV sensor  98  is illustrated. After forming insulating layer  96 , a hard-magnetic (HM) stabilizing layer  100  is formed in contact with free layer  78  using a geometry typical of the prior art. The remainder of sensor  98  may be appreciated with reference to the above discussion of sensor  72  ( FIG. 3 ). 
     The CPP SV sensor of this invention may also be longitudinally stabilized to suppress Barkhausen noise by using a self-stabilized SV sensor geometry in which a layer of high-resistance hard magnetic (HM) material is deposited under or over a SV stack to longitudinally bias the free layer through indirect coupling at the edges of the stack. For example, in  FIG. 5 , a self-stabilized CPP SV sensor  102  is illustrated. After forming insulating read gap layer  76 , a HM layer  104  is formed. A very thin nonmagnetic nonconductive spacer layer  106  is then formed to provide the separation needed to avoid direct magnetic coupling (exchange or Neel) of HM layer  104  to free layer  78 . Free layer  78  is then deposited. The track-width milling step is now used to define the width of both free layer  78  and HM layer  104  by over-milling down into insulating read gap layer  76 . Magnetostatic forces, analogous to the forces exerted by the pinned layer moment transversely on the free layer, act to longitudinally stabilize the free layer antiparallel to the HM moment. The self-stabilized sensor has an efficient geometry because the critical dimensions are milled in a single step, providing a consistent structure from device to device and from wafer to wafer to optimize the balance of SV stability and sensitivity. After overmilling, an insulating spacer layer  108  is deposited to prevent any contact between HM layer  104  and conductive spacer layer  86 , which is next deposited. The remainder of sensor  102  may be appreciated with reference to the above discussion of sensor  72  ( FIG. 3 ). 
       FIG. 6  is a block diagram of a flow chart illustrating the fabrication method of this invention and may be appreciated with reference to CPP SV sensor  72  in  FIG. 3  and the following description. In step  109 , the surface of a substrate is prepared for the deposition of ferromagnetic (FM) shield (S 1 ) layer  74  in step  110 . In step  112 , nonmagnetic nonconductive read gap layer  76  is formed over shield (S 1 ) layer  74  and may be covered in a seed layer (not shown) before ferromagnetic (FM) free layer  78  is formed in step  114 . Step  114  may also include preliminary steps (not shown) such as formation of self-stabilizing HM layer  106  ( FIG. 5 ). In step  116 , a photoresist pattern is formed over center region  80  to define the track-width and the track-width etch is done in step  118 . In step  120 , a self-aligned nonmagnetic conductive spacer layer  86  is deposited on each side of center region  80  in contact with the free-layer edges  82  &amp;  84 . Self-aligned FM pinned layer and pinning layer structures  88  are formed in steps  122  and  124 , respectively, each of which may include several layers of different materials. Finally, in step  126 , self-aligned first and second lead conductor (L 1  &amp; L 2 ) layers  90  &amp;  92  are formed before the photoresist is lifted off in step  128 . If desired, a new photoresist pattern is formed in step  130  to prepare for deposition of self-aligned insulating layer  96  in step  132 . This photoresist is lifted off in step  134  and second shunt conductor layer  94  formed in the final step  136 . Such additional processing step as may be required to fabricate a completed read sensor can be readily appreciated by practitioners familiar with the art. 
       FIGS. 7–9  illustrate a magnetic disk drive  138 . The drive  138  includes a spindle  140  that supports and rotates a magnetic disk  142 . Spindle  140  is rotated by a motor  144  that is controlled by a motor controller  146 . A slider  148  with a combined read and write magnetic head  150  is supported by a suspension  152  and actuator arm  154 . A plurality of disks, sliders and suspensions may be employed in a large capacity direct access storage device (DASD)  156  as shown in  FIG. 9 . Suspension  152  and actuator arm  154  position slider  148  so that magnetic head  150  is in a transducing relationship with a surface of magnetic disk  142 . When disk  142  is rotated by motor  144 , slider  148  is supported on a thin (typically, 50 nm) cushion of air (air bearing) between the surface of disk  142  and the air bearing surface (ABS)  158 . Magnetic head  150  may then be employed for writing information to multiple circular tracks on the surface of disk  142 , as well as for reading information therefrom. The processing circuitry  160  exchanges signals, representing such information, with the head  150 , provides motor drive signals for rotating the magnetic disk  142 , and provides control signals for moving slider  148  to various tracks. In  FIG. 10 , slider  148  is shown mounted to suspension  152 . The components described hereinabove may be mounted on a frame  162  of a housing, as shown in  FIG. 9 . 
       FIG. 11  is an ABS view of slider  148  and magnetic head  150 . The slider has a center rail  164  that supports the magnetic head  150 , and side rails  166  and  168 . Rails  164 ,  166  and  168  extend from a cross rail  170 . With respect to rotation of magnetic disk  142 , cross rail  170  is at a leading edge  172  of slider  148  and magnetic head  150  is at a trailing edge  174  of slider  148 . 
       FIG. 12  is a side cross-sectional elevation view of the merged MR head  150 , which includes a write head portion  176  and a read head portion  178  employing the SV sensor  180  of this invention ( FIGS. 3–5 ).  FIG. 13  is an ABS view of  FIG. 12 . SV sensor  180  is sandwiched between first and second gap layers  182  and  184 , and gap layers  182  and  184  are sandwiched between the first (S 1 ) and second (S 2 ) shield layers  186  and  188 . The resistance of SV sensor  180  changes in response to changes in external magnetic fields. A sense current I S  conducted through sensor  180  causes these resistance changes to be manifested as voltage potential changes. These potential changes are then processed as readback signals by processing circuitry  160  ( FIG. 9 ). 
     The write head portion of the merged MR head includes a coil layer  190  sandwiched between the first and second insulation layers  192  and  194 . A third insulation layer  196  may be employed for planarizing the head to eliminate ripples in the second insulation layer caused by the coil layer  190 . First, second and third insulation layers  192 – 196  are referred to in the art as an “insulation stack.” Coil layer  190  and first, second and third insulation layers  192 ,  194  and  196  are sandwiched between the first (P 1 ) and second (P 2 ) pole piece layers  198  and  200 . First and second pole piece layers  198  and  200  are magnetically coupled at a back gap  202  and have first and second pole tips  204  and  206  that are separated by a write gap layer  208  at the ABS. As shown in  FIGS. 8 and 10 , the first and second solder connections  210  and  212  connect leads from SV sensor  180  to leads  214  and  216  on the suspension  152 , and the third and fourth solder connections  218  and  220  connect leads  222  and  224  from coil  190  (see  FIG. 14 ) to leads  226  and  228  on suspension  152 . Although  FIG. 13  shows second shield (S 2 ) layer  188  to be merged with first pole piece (P 1 ) layer  198 , these elements may be embodied as two distinct MR layers separated by a nonmagnetic isolation layer (not shown) similar to insulation layers  192 – 196 . 
     Clearly, other embodiments and modifications of this invention may 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 drawing.