Abstract:
A test system and method determining performance of a merged magnetoresistive read-write head based upon operating the write inductive head of the merged read-write head, measuring the resistance of the read head under certain read current bias conditions and finding which read heads have been damaged by ESD.

Description:
TECHNICAL FIELD  
         [0001]    This invention relates to magnetic performance measurement of a merged type magnetoresistive head during the read process in a disk drive, including at least any of the collection comprising AMR (Anisotropic Magneto-resistive), GMR (Giant Magnetoresistive), and TMR (Tunneling Magneto-resistive) read-write head.  
         BACKGROUND ART  
         [0002]    Disk drives are an important data storage technology, based on several crucial components. These components include the read-write heads, which directly communicate with a disk surface containing the data storage medium. This invention involves magnetic performance measurement of the read-write heads inductively using the write heads.  
           [0003]    [0003]FIG. 1A illustrates a typical prior art high capacity disk drive  10  including actuator arm  30  with voice coil  32 , actuator axis  40 , suspension or head arms  50 - 58  with slider/head unit  60  placed among the disks.  
           [0004]    [0004]FIG. 1B illustrates a typical prior art high capacity disk drive  10  with actuator  20  including actuator arm  30  with voice coil  32 , actuator axis  40 , head arms  50 - 56  and slider/head units  60 - 66  with the disks removed.  
           [0005]    Since the 1980&#39;s, high capacity disk drives  10  have used voice coil actuators  20 - 66  to position their read-write heads over specific tracks. The heads are mounted on head sliders  60 - 66 , which float a small distance off the disk drive surface when in operation. Often there is one head per head slider for a given disk drive surface. There are usually multiple heads in a single disk drive, but for economic reasons, usually only one voice coil actuator.  
           [0006]    Voice coil actuators are further composed of a fixed magnet actuator  20  interacting with a time varying electromagnetic field induced by voice coil  32  to provide a lever action via actuator axis  40 . The lever action acts to move head arms  50 - 56  positioning head slider units  60 - 66  over specific tracks with speed and accuracy. Actuator arms  30  are often considered to include voice coil  32 , actuator axis  40 , head arms  50 - 56  and head sliders  60 - 66 . Note that actuator arms  30  may have as few as a single head arm  50 . Note also that a single head arm  52  may connect with two head sliders  62  and  64 .  
           [0007]    Merged type heads possess different components for reading and writing, because the magneto-resistive effect only occurs during reading. A merged type head typically includes a thin film head and a spin valve sensor. The primary use of the thin film head is in the write process. The spin valve sensor is used for reading.  
           [0008]    MR heads have several advantages over earlier approaches, using a single component, for both read and write. Earlier read-write heads were a study in tradeoffs. The single component, often a ferrite core, can increase read sensitivity with additional windings around the core. However, these added windings make the ferrite core write less efficiently.  
           [0009]    Introduced in the 1990&#39;s, merged heads brought significant increases in areal density. A merged type head reads the disk surface using a spin valve, containing a conductive thin film, whose resistance changes in the presence of a magnetic field. By separating the functions of writing and reading, each function can be optimized further than would be possible for the older read-write heads. For all the improvement that merged heads bring, their control to date creates problems. However, before discussing these problems, consider first how and what controls these devices in contemporary disk drives.  
           [0010]    [0010]FIG. 2A illustrates a simplified schematic of a disk drive controller  1000  controlling an analog read-write interface  220 , the read differential signal pair (r+ and r−) and write differential signal pair (w+ and w−) communicating the resistivity found in the spin valve within MR read-write head  200  of the prior art.  
           [0011]    [0011]FIG. 2B illustrates a suspended head slider  60  containing the MR read-write head  200  of the prior art.  
           [0012]    [0012]FIG. 2C illustrates a perspective view of merged read-write head  200  from FIG. 2B including write inductive head  202  and magnetoresistive read head (or spin valve)  204  of the prior art.  
           [0013]    [0013]FIG. 2D illustrates a simplified cross section view of spin valve  204  of FIG. 2C of the prior art.  
           [0014]    [0014]FIGS. 3A and 3B illustrate the magnetic flux direction related to the charging of the write differential signal pair connecting to P 1  and P 2  of the prior art.  
           [0015]    [0015]FIG. 3A illustrates the field flowing from P 1  to P 2 , when there is a positive write current asserted on the write differential signal pair under normal conditions in the prior art.  
           [0016]    [0016]FIG. 3B illustrates the field flowing from P 2  to P 1 , when there is a negative write current asserted on the write differential signal pair under normal conditions in the prior art.  
           [0017]    Electro-Static Discharge (ESD) can diminish or damage these flows by pinning part of the spin valve head  204  in a weakened or reversed magnetic condition. Such conditions damage or destroy the ability of the spin valve  204 , thus the MR read-write head  200  to function.  
           [0018]    [0018]FIG. 4A depicts the voltage amplitude measured across the read differential signal pair sensing a written pulse on a disk drive surface in the prior art.  
           [0019]    As used in the prior art, the amplitude is defined as v + +v − . Asymmetry is defined as v + −v − . The quality measure for spin valves is asymmetry vs. amplitude, or  
           (v + −v − )/(v + +v − ).  
           [0020]    The ideal situation would have a quality measure of 0%, but acceptable ranges are often 5% to 10%, with 7% being typical for a spin valve. Note that ESD damage is indicated by increases in the quality measure.  
           [0021]    Typically, either a quasi-static tester or R(H) tester is used to test the spin valve for ESD damage. Both forms of testers require external magnets, often generating at least 1,000 Oesteds. The external magnets further require power supplies, and a mechanical infrastructure to accurately position the magnet with respect to these very small components. All of this adds to the cost of testing and therefore manufacturing MR read-write heads, as well as the products containing these read-write heads, including head sliders, actuator arms, voice coil actuators and disk drives.  
           [0022]    Another alternative is the use of a disk media based tester such as manufactured by Guzik. While somewhere in the process of making a voice coil actuator, testing must be done using disk media, this is even more expensive than quasi-static or R(H) testing.  
           [0023]    To summarize, what is needed are test circuits and methods reducing the cost of testing and manufacturing MR read-write heads, and products containing these read-write heads (head sliders, actuator arms, voice coil actuators and disk drives).  
         SUMMARY OF THE INVENTION  
         [0024]    The invention includes a test system and method determining performance of a merged magnetoresistive read-write head based upon operating the write inductive head and measuring the resistance of the read head under certain read current bias conditions selecting read heads undamaged by ESD.  
           [0025]    The invention removes the requirement for an external magnet or disk memory media surface to determine whether a merged magnetoresistive read-write head has been damaged by Electro-Static Discharge(ESD).  
           [0026]    The system and method can be applied at the wafer fabrication manufacturing stage to the read-write heads, as well as the assembly stages for head sliders, actuator arms, and voice coil actuators. The invention includes the products of these manufacturing stages using the method, as well as disk drives assembled from these components.  
           [0027]    This invention significantly reduces production cost of testing for ESD damage.  
           [0028]    Note that the inventive method can be implemented at least in part by the operation and control provided by one or more of the following: a computer, a finite state machine, a neural network and/or a human operator. While the following discussion is focused on computer operations, this has been done strictly to clarify the discussion and is not meant to limit the scope of the claims.  
           [0029]    These and other advantages of the present invention will become apparent upon reading the following detailed descriptions and studying the various figures of the drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0030]    [0030]FIG. 1A illustrates a typical prior art high capacity disk drive  10  including actuator arm  30  with voice coil  32 , actuator axis  40 , suspension or head arms  50 - 58  with slider/head unit  60  placed among the disks;  
         [0031]    [0031]FIG. 1B illustrates a typical prior art high capacity disk drive  10  with actuator  20  including actuator arm  30  with voice coil  32 , actuator axis  40 , head arms  50 - 56  and slider/head units  60 - 66  with the disks removed;  
         [0032]    [0032]FIG. 2A illustrates a simplified schematic of a disk drive controller  1000  controlling an analog read/write interface  220 , the read differential signal pair (r+ and r−) and write differential signal pair (w+ and w−) communicating the resistivity found in the spin valve within MR read/write head  200  of the prior art;  
         [0033]    [0033]FIG. 2B illustrates a suspended head slider  60  containing the MR read-write head  200  of the prior art;  
         [0034]    [0034]FIG. 2C illustrates a perspective view of merged read-write head  200  from FIG. 2B including write inductive head  202  and magnetoresistive read head (or spin valve)  204  of the prior art;  
         [0035]    [0035]FIG. 2D illustrates a simplified cross section view of spin valve  204  of FIG. 2C of the prior art;  
         [0036]    [0036]FIGS. 3A and 3B illustrate the magnetic flux direction related to the charging of the write differential signal pair connecting to P 1  and P 2  of the prior art;  
         [0037]    [0037]FIG. 4A depicts the voltage amplitude measured across the read differential signal pair sensing a written pulse on a disk drive surface in the prior art;  
         [0038]    [0038]FIG. 4B illustrates a system determining performance of a merged magnetoresistive read-write head  200  to select a passed read-write head;  
         [0039]    [0039]FIG. 5A illustrates the voltage measurements in mV versus the write current level in mA as found with a test system as in FIG. 4B;  
         [0040]    [0040]FIG. 5B illustrates a variation on the circuit of FIG. 4B with regards to the read head  204  and read differential signal pair r+ and r− additionally containing a Double Pole Double Throw (DPDT) switch;  
         [0041]    [0041]FIG. 6A illustrates a comparison of experimental results obtained by the inventors between the differential MRR in milli-ohms along the horizontal axis and voltage measurements by a Quasi-static tester in micro-volts along the vertical axis;  
         [0042]    [0042]FIG. 6B illustrates a comparison between the normal state and the pin reversed state of an SV head  204  such as found after damage by an ESD event;  
         [0043]    [0043]FIG. 7 illustrates a refinement of FIGS. 4B and 5B wherein computer  2000  can perform and control all steps of the testing method from program system  2500 ;  
         [0044]    [0044]FIG. 8 illustrates a detail flowchart of program system  2500  of FIGS. 7 and 4B for determining performance of merged magnetoresistive read-write head  200  to select the passed read-write head;  
         [0045]    [0045]FIG. 9A illustrates a detail flowchart of operation  3052  of FIG. 8 for creating the second MRR;  
         [0046]    [0046]FIG. 9B illustrates a detail flowchart of operation  3072  of FIG. 8 for evaluating the merged magnetoresistive read-write head;  
         [0047]    [0047]FIG. 10A illustrates a detail flowchart of operation  3112  of FIG. 9A for the write current source driving at the second write current level to create the second MRR;  
         [0048]    [0048]FIG. 10B illustrates a detail flowchart of operation  3122  of FIG. 9A for the read current source driving at the second read current level to create the second MRR;  
         [0049]    [0049]FIG. 11A illustrates a method  2600  for making a head slider;  
         [0050]    [0050]FIG. 11B illustrates a method  2630  for making an actuator arm;  
         [0051]    [0051]FIG. 12A illustrates a method  2700  for making a voice coil actuator; and  
         [0052]    [0052]FIG. 12B illustrates a method  2800  for making a disk drive. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0053]    [0053]FIG. 4B illustrates a system determining performance of a merged magnetoresistive read-write head  200  to select a passed read-write head.  
         [0054]    Write current source  2050  drives write differential signal pair w+ and w− of merged magnetoresistive read-write head  200  at a first write current level.  
         [0055]    Read current source  2080  drives a read differential signal pair of merged magnetoresistive read-write head  200  at a first read current level.  
         [0056]    Volt meter  2030  measures across the read differential signal pair r+ and r− to create a first voltage reading.  
         [0057]    ESD protection circuit  2020  couples across the read differential signal pair r+ and r− protecting merged magnetoresistive read-write head  200  from ESD. Note that it is preferable with today&#39;s technology to use a dual diode circuit as shown herein, but ESD protection may be provided by other approaches, which may include integration of ESD protection into volt meter  2030  and/or read current source  2080 .  
         [0058]    Computer  2000  may provide a means for determining a first MRR as essentially the first voltage reading divided by the first read current level.  
         [0059]    Note that as used herein, the phrase “essentially as” will be used to denote the approximate nature of some or many of the calculations in the system and method of the invention. By way of example, it may be preferable to compute division based upon fixed-point numeric representations of the first voltage reading and the first read current level. Alternatively, division of floating point numeric representations may be used, or conceivably, the logarithms of the absolute values of the numbers involved may be taken, subtracted, and then exponentiated to approximate the first MRR. In at least each of these cases, the resulting number is essentially the first MRR.  
         [0060]    A second MRR is created by control of at least one member of the current source collection comprising the read current source  2080  and the write current source  2050 .  
         [0061]    A differential MRR is essentially the first MRR minus the second MRR.  
         [0062]    The merged magnetoresistive read-write head  200  is evaluated based upon the differential MRR to select the passed read-write head. This may be implemented as passing merged magnetoresistive read-write head  200  based upon when the differential MRR is essentially non-positive.  
         [0063]    The second MRR may be created by at least one of the following: the write current source  2050  driving at a second write current level to create the second MRR and read current source  2080  driving at a second read current level to create the second MRR.  
         [0064]    The method of testing may be implemented as a program system  2500  composed of program steps residing in memory  2010 , which is accessibly coupled  2002  to computer  2000 .  
         [0065]    [0065]FIG. 5A illustrates the voltage measurements in mV versus the write current level in mA as found with a test system as in FIG. 4B.  
         [0066]    [0066]FIG. 5B illustrates a variation on the circuit of FIG. 4B with regards to the read head  204  and read differential signal pair r+ and r− additionally containing a Double Pole Double Throw (DPDT) switch.  
         [0067]    The DPDT switch controls the polarity coupling of read current source  2080  with regards the read differential signal pair. Note that DPDT switch may be implemented as two multiplexors  2070  and  2072 .  
         [0068]    Circuits such as those shown in FIG. 5B are capable of generating a second MRR by controlling read current source  2080  at a second read current level, which is essentially the negative of the first read current level. Volt meter  2030  measures a second voltage reading across the read differential signal pair to create a second voltage reading. The second MRR is essentially the second voltage reading divided by the second current level.  
         [0069]    [0069]FIG. 6A illustrates a comparison of experimental results obtained by the inventors between the differential MRR in milli-ohms along the horizontal axis and voltage measurements by a Quasi-static tester in micro-volts along the vertical axis.  
         [0070]    R is the correlation factor and is essentially 74%. Note that R is derived from experimental data. The inventors find this is a high enough correlation to replace quasi-static testing.  
         [0071]    [0071]FIG. 6B illustrates a comparison between the normal state and the pin reversed state of an SV head  204  such as found after damage by an ESD event for a platinum-magnesium GMR read-write head (PTMn GMR Head).  
         [0072]    The right hand vertical axis shows the amplitude in microvolts observed by a quasi-static tester. The left hand vertical axis shows the differential MRR measured in milli-ohms. The horizontal axis shows four test conditions based upon Human Body Model (HBM) ESD events on the read differential signal pair.  
         [0073]    There are four bar clusters, each associated with separate and successive ESD events. The two filled bars in each bar cluster represent readings from the quasi-static tester with read bias currents of +5 mA and −5 mA. The unfilled bar shows the differential MRR value obtained from first and second read current levels of 1 mA and −1 mA, respectively.  
         [0074]    The first bar cluster is associated with a normal, undamaged read-write head. The second bar cluster shows the effect of an ESD event of +35 HBM Volts, which induces a pinned layer magnetization reversal, damaging the read-write head. The third bar cluster shows the effect of a second ESD event of −35 HBM Volts, which approximately recovers the magnetization of the pinned layer of the read-write head. The fourth bar cluster shows the effect of a third ESD event of +35 HBM Volts, again damaging the read-write head by reversing the magnetization of the pinned layer.  
         [0075]    [0075]FIG. 7 illustrates a refinement of FIGS. 4B and 5B wherein computer  2000  can perform and control all steps of the testing method from program system  2500 .  
         [0076]    [0076]FIG. 8 illustrates a detail flowchart of program system  2500  of FIGS. 7 and 4B for determining performance of merged magnetoresistive read-write head  200  to select the passed read-write head.  
         [0077]    Arrow  3010  directs the flow of execution from starting operation  2500  to operation  3012 . Operation  3012  performs a write current source driving a write differential signal pair of the merged magnetoresistive read-write head at a first write current level. Arrow  3014  directs execution from operation  3012  to operation  3016 . Operation  3016  terminates the operations of this flowchart.  
         [0078]    Arrow  3020  directs the flow of execution from starting operation  2500  to operation  3022 . Operation  3022  performs a read current source driving a read differential signal pair of the merged magnetoresistive read-write head at a first read current level. Arrow  3024  directs execution from operation  3022  to operation  3016 . Operation  3016  terminates the operations of this flowchart.  
         [0079]    Arrow  3030  directs the flow of execution from starting operation  2500  to operation  3032 . Operation  3032  performs a volt meter measuring across the read differential signal pair to create a first voltage reading. Arrow  3034  directs execution from operation  3032  to operation  3016 . Operation  3016  terminates the operations of this flowchart.  
         [0080]    Arrow  3040  directs the flow of execution from starting operation  2500  to operation  3042 . Operation  3042  performs determining a first MRR as essentially the first voltage reading divided by the first read current level. Arrow  3044  directs execution from operation  3042  to operation  3016 . Operation  3016  terminates the operations of this flowchart.  
         [0081]    Arrow  3050  directs the flow of execution from starting operation  2500  to operation  3052 . Operation  3052  performs creating a second MRR by control of at least one member of the current source collection. The current source collection comprises the read current source and the write current source. Arrow  3054  directs execution from operation  3052  to operation  3016 . Operation  3016  terminates the operations of this flowchart.  
         [0082]    Arrow  3060  directs the flow of execution from starting operation  2500  to operation  3062 . Operation  3062  performs calculating a differential MRR as the first MRR minus the second MRR. Arrow  3064  directs execution from operation  3062  to operation  3016 . Operation  3016  terminates the operations of this flowchart.  
         [0083]    Arrow  3070  directs the flow of execution from starting operation  2500  to operation  3072 . Operation  3072  performs evaluating the merged magnetoresistive read-write head based upon the differential MRR to select the passed read-write head. Arrow  3074  directs execution from operation  3072  to operation  3016 . Operation  3016  terminates the operations of this flowchart.  
         [0084]    [0084]FIG. 9A illustrates a detail flowchart of operation  3052  of FIG. 8 for creating the second MRR.  
         [0085]    Arrow  3110  directs the flow of execution from starting operation  3052  to operation  3112 . Operation  3112  performs the write current source driving at a second write current level to create the second MRR. Arrow  3114  directs execution from operation  3112  to operation  3116 . Operation  3116  terminates the operations of this flowchart.  
         [0086]    Arrow  3120  directs the flow of execution from starting operation  3052  to operation  3122 . Operation  3122  performs the read current source driving at a second read current level to create the second MRR. Arrow  3124  directs execution from operation  3122  to operation  3116 . Operation  3116  terminates the operations of this flowchart.  
         [0087]    [0087]FIG. 9B illustrates a detail flowchart of operation  3072  of FIG. 8 for evaluating the merged magnetoresistive read-write head.  
         [0088]    Arrow  3150  directs the flow of execution from starting operation  3072  to operation  3152 . Operation  3152  performs passing the merged magnetoresistive read-write head based upon when the differential MRR is essentially non-positive to select the passed merged read-write head. Arrow  3154  directs execution from operation  3152  to operation  3156 . Operation  3156  terminates the operations of this flowchart.  
         [0089]    [0089]FIG. 10A illustrates a detail flowchart of operation  3112  of FIG. 9A for the write current source driving at the second write current level to create the second MRR.  
         [0090]    Arrow  3170  directs the flow of execution from starting operation  3112  to operation  3172 . Operation  3172  performs the write current source driving the write differential signal pair at the second write current level. Arrow  3174  directs execution from operation  3172  to operation  3176 . Operation  3176  terminates the operations of this flowchart.  
         [0091]    Arrow  3180  directs the flow of execution from starting operation  3112  to operation  3182 . Operation  3182  performs the volt meter measuring across the read differential signal pair to create the second voltage reading. Arrow  3184  directs execution from operation  3182  to operation  3176 . Operation  3176  terminates the operations of this flowchart.  
         [0092]    Arrow  3190  directs the flow of execution from starting operation  3112  to operation  3192 . Operation  3192  performs determining the second MRR as essentially the second voltage reading divided by the first read current level. Arrow  3194  directs execution from operation  3192  to operation  3176 . Operation  3176  terminates the operations of this flowchart.  
         [0093]    Note that the second write current level may be within a first tolerance of the negative of the first write current level. The first tolerance may indicate a least significant bit, possibly belonging to the tolerance collection comprising the fractions: {fraction (1/16)}, {fraction (1/32)}, {fraction (1/64)}, {fraction (1/128)}, {fraction (1/256)}, {fraction (1/512)}, {fraction (1/1024)}, {fraction (1/2048)}, {fraction (1/4096)}, {fraction (1/8192)}, {fraction (1/16384)}, and 1/32768.  
         [0094]    [0094]FIG. 10B illustrates a detail flowchart of operation  3122  of FIG. 9A for the read current source driving at the second read current level to create the second MRR.  
         [0095]    Arrow  3230  directs the flow of execution from starting operation  3122  to operation  3232 . Operation  3232  performs the read current source driving the read differential signal pair at the second read current level. Arrow  3234  directs execution from operation  3232  to operation  3236 . Operation  3236  terminates the operations of this flowchart.  
         [0096]    Arrow  3240  directs the flow of execution from starting operation  3122  to operation  3242 . Operation  3242  performs the volt meter measuring across the read differential signal pair to create a third voltage reading. Arrow  3244  directs execution from operation  3242  to operation  3236 . Operation  3236  terminates the operations of this flowchart.  
         [0097]    Arrow  3250  directs the flow of execution from starting operation  3122  to operation  3252 . Operation  3252  performs determining the second MRR as essentially the third voltage reading divided by the second read current level. Arrow  3254  directs execution from operation  3252  to operation  3236 . Operation  3236  terminates the operations of this flowchart.  
         [0098]    Note that the second read current level may be within a second tolerance of the negative of the first read current level. The second tolerance may also be a member of the tolerance collection.  
         [0099]    [0099]FIG. 11A illustrates a method  2600  for making a head slider, comprising at least one of the following operations.  
         [0100]    Arrow  2610  directs the flow of execution from starting operation  2600  to operation  2612 . Operation  2612  performs using the passed read-write head of FIG. 8 to create the head slider containing the passed read-write head. Arrow  2614  directs execution from operation  2612  to operation  2616 . Operation  2616  terminates the operations of this flowchart.  
         [0101]    Arrow  2620  directs the flow of execution from starting operation  2600  to operation  2622 . Operation  2622  performs applying the method  2500  to at least one merged magnetoresistive read-write head contained in the head slider to select the passed read-write head. Arrow  2624  directs execution from operation  2622  to operation  2616 . Operation  2616  terminates the operations of this flowchart.  
         [0102]    [0102]FIG. 11B illustrates a method  2630  for making an actuator arm, comprising at least one of the following operations.  
         [0103]    Arrow  2640  directs the flow of execution from starting operation  2630  to operation  2642 . Operation  2642  performs using the head slider of method  2600  to create the actuator arm containing the passed read-write head. Arrow  2644  directs execution from operation  2642  to operation  2646 . Operation  2646  terminates the operations of this flowchart.  
         [0104]    Arrow  2650  directs the flow of execution from starting operation  2630  to operation  2652 . Operation  2652  performs applying the method  2500  to at least one merged magnetoresistive read-write head contained in the actuator arm to select the passed read-write head. Arrow  2654  directs execution from operation  2652  to operation  2646 . Operation  2646  terminates the operations of this flowchart.  
         [0105]    [0105]FIG. 12A illustrates a method of making  2700  a voice coil actuator comprising at least one of the following operations.  
         [0106]    Arrow  2710  directs the flow of execution from starting operation  2700  to operation  2712 . Operation  2712  performs using the actuator arm of method  2630  to create the voice coil actuator containing the passed read-write head. Arrow  2714  directs execution from operation  2712  to operation  2716 . Operation  2716  terminates the operations of this flowchart.  
         [0107]    Arrow  2720  directs the flow of execution from starting operation  2700  to operation  2722 . Operation  2722  performs applying the method  2500  to at least one merged magnetoresistive read-write head contained in the voice coil actuator to select the passed read-write head. Arrow  2724  directs execution from operation  2722  to operation  2716 . Operation  2716  terminates the operations of this flowchart.  
         [0108]    [0108]FIG. 12B illustrates a method  2800  of making a disk drive comprising at least one of the following operations.  
         [0109]    Arrow  2810  directs the flow of execution from starting operation  2800  to operation  2812 . Operation  2812  performs using the voice coil actuator of method  2700  to create the disk drive containing the passed read-write head. Arrow  2814  directs execution from operation  2812  to operation  2816 . Operation  2816  terminates the operations of this flowchart.  
         [0110]    Arrow  2820  directs the flow of execution from starting operation  2800  to operation  2822 . Operation  2822  performs applying the method  2500  to at least one merged read-write magnetoresistive read-write head contained in the disk drive to select the passed read-write head. Arrow  2824  directs execution from operation  2822  to operation  2816 . Operation  2816  terminates the operations of this flowchart.  
         [0111]    The preceding embodiments have been provided by way of example and are not meant to constrain the scope of the following claims.