Abstract:
A transducer for magnetically reading and writing information is disclosed. The present invention eases the intricate process of wafer thin film deposition and bar lapping by proposing a transducer including a first and second member, both of which perform the reading and writing function of the transducer. The present invention provides a transducer with greatly improved magnetic efficiency by probing the media magnetization directly. The structure is inherently stable due to shape anisotropy of the members and the closure of magnetic flux at the ends of each member.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention generally relates to magnetic read and write heads for high areal density recording, and in particular the present invention relates to producing one device which increases the efficiency, yield and reliability of a merged magnetic writer and reader component.  
       BACKGROUND OF THE INVENTION  
       [0002]     As the density of data tracks on magnetic discs continues to increase, increased magnetic efficiency and high manufacturability of the magnetic read/write head, or transducer, is required. Typically, the transducer consists of separate writer and reader elements. One type of writer element is a perpendicular writer. Perpendicular recording, as opposed to the more conventional longitudinal recording, is a form of magnetic recording in which magnetic moments representing bits of data are orientated perpendicularly to the surface of the recording layer of the recording medium. Perpendicular recording offers advantages over longitudinal recording, such as the ability to achieve higher linear densities, which is important to extending disc drive technology beyond current data density limitations.  
         [0003]     The reader element is made of multi-layers of magnetic and non-magnetic thin films between which there are magnetic, electrical and physical-chemical interactions. Managing the manufacturing yield and reliability of this complicated structure is becoming increasingly difficult as areal density and head to media spacing becomes smaller. Beyond manufacturing difficulties, the currently designed reader elements depend on the media magnetic flux to rotate the free layer. Consequently, the reader and the shields much be designed so that; a) the media flux reaching the free layer is maximized while b) the shield-shield spacing remains small to maintain bit density. Requirements a) and b) are often conflicting and a compromise must be reached.  
         [0004]     Transducers are produced by thin film deposition techniques. In such a process, arrays of transducers are formed on a common substrate or wafer. The wafer is inspected, and is then sliced to produce bars. The bars are then lapped at the surface that will eventually face the recording medium to obtain the desired magnetoresistive element height (also referred to as stripe height). Finally, the bars are diced to form individual sliders, each with a transducer. This conventional process can be problematic for at least two reasons. First, the thin film deposition process is expensive and time consuming. Because of the complexity of depositing multiple layers of different materials, variations can arise between processed wafers, which can result in problems in performance, reliability and predictability. Second, if the lapping process is slightly off, or produces inconsistent magnetoresistive element height, the end product will suffer in performance and in reliability. Other parameters that are considered during the lapping process are metal smearing (corrosion), shorting across the gap (surface finish), pole tip recession and protrusion. Therefore, there is a need for a transducer that can be used for high areal density that is less intricate in terms of the thin film deposition process and the lapping process.  
         [0005]     The present invention addresses these and other needs and provides advantages that will become apparent to those skilled in the art.  
       SUMMARY OF THE INVENTION  
       [0006]     The present invention provides a transducer, or magnetic head, including a first and second ferromagnetic member, wherein the first and second ferromagnetic member are electrically isolated and configured for magnetic reading and writing.  
         [0007]     In an alternative embodiment, a magnetic read and write element are formed in a body, wherein the magnetic read and write element comprise a first and second magnetic member, the first magnetic member being magnetically fixed in a first direction and the second magnetic member being magnetically fixed in a second direction opposite the first direction.  
         [0008]     Further, in another alternative embodiment, the present invention includes a magnetic read and write sensor including a first and second ferromagnetic member positioned in a body, a storing medium adjacent the body and a barrier layer positioned between the body and the storing medium.  
         [0009]     These and various other features as well as advantages which characterize the present invention should be apparent to those skilled in the art upon reading the following detailed description and review of the associated drawings.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is a perspective view of a disc drive in which the present invention is useful.  
         [0011]      FIG. 2  is a cross-sectional view of the transducer according to the present invention.  
         [0012]      FIG. 3A  is a cross-sectional view of an alternative preferred embodiment of the present invention, wherein the transducer includes a storage medium.  
         [0013]      FIG. 3B  is a cross-sectional view of an alternative preferred embodiment of the present invention, wherein the storage medium includes a lubrication layer.  
         [0014]      FIG. 3B  is a cross-sectional view of an alternative preferred embodiment of the present invention, wherein the storage medium includes a magnetic matrix layer.  
         [0015]      FIG. 4A  is a side cross-sectional view of an alternative preferred transducer of the present invention, wherein the transducer includes a current recovery pad.  
         [0016]      FIG. 4B  is a side cross-sectional view of an alternative preferred transducer of the present invention, wherein the storage medium is electrically connected to ground.  
         [0017]      FIG. 4A  is a side cross-sectional view of an alternative preferred transducer of the present invention, wherein the transducer includes a current recovery pad.  
         [0018]      FIG. 5  is a side cross-sectional view of an alternative preferred transducer of the present invention, wherein the transducer is connected to a differential preamplifier. 
     
    
     DETAILED DESCRIPTION  
       [0019]      FIG. 1  is a perspective view of a disc drive  10  including a dual-stage disc drive actuation system for positioning a head-carrying slider over a track  34  of disc (or storage medium)  30 . Disc drive  10  includes voice coil motor  12  arranged to rotate actuator arm  16  on a spindle around axis  14 . Head suspension  18  is connected to actuator arm  16  at head mounting block  20 . A slider  24  is attached to head suspension  18  by flexure  22 , which in turn carries a transducer for reading and/or writing data on concentric tracks on disc  30 . Disc  30  rotates around axis  32 , so that windage is encountered by slider  24  to keep it aloft a small distance above the surface of disc  30 . Disc drive  10  also includes board electronics  19 , which hosts various circuitry for disc drive  10 .  
         [0020]     Referring now to  FIG. 2 , the magnetic storage device  24  according to the present invention will be described. The storage device includes a body  40  (or slider), which contains a first member  42  and second member  44 . The body preferably is made of a ceramic material, or can be made up of AlTiC, alumina, or a combination of both. The first and second members are composed of a ferromagnetic material, such as NiFe. The magnetization of each member is fixed. This can be achieved by a number of techniques including, but not limited to, shape anisotropy, magneto-strictive anisotropy, crystalline anisotropy, or by using an AFM pinning layer. The first and second member are electrically isolated or insulated from each other. The cross-section of each of the first and second member defines the recording areal density, in that it will define the dimensions of the written track. A typical cross-section for an areal density of 100 Gbit/inch 2  is approximately 100 nm by 100 nm. Also, the first and second member can be configured either in a side-by-side configuration or a front-and-back configuration. In the preferred embodiment, the first and second members are shown in a front-and-back configuration.  
         [0021]     The first and second members collectively perform both the reading and writing operation. For the writing operation, a current is passed through one of the first or second members and across the head-disc interface into the media (shown in  FIGS. 3   a - c ). Current passed through a member fixed away from media will write a bit in a different direction than current passed through a member fixed toward the media. For sufficiently high current density, the injected spin dominates over local spin, thereby changing the media magnetization and achieving writing. A current to achieve spin oscillation, the beginning of spin reversal, has been reported to be approximately 3 mA for a structure that has a cross-section of 130 nm by 70 nm, which is achievable with the current preamplifier technology.  
         [0022]     For the reading operation, the first and second member each separately with the media form the two electrodes in a spin dependent tunnel junction sensor. Tunneling current from the slider is polarized along a fixed direction, whereas the media magnetization varies as each permanent magnet grain or each written bit passes below the body. Due to the tunneling magnetoresistive effect, the head-disc interface current is modulated by media magnetization, thereby achieving reading.  
         [0023]     The signal from the transducer is fed differentially into a preamplifier (shown in  FIG. 5 ). Because there are two readers (the first and second member), there are going to be two signals, called a differential read-back signal. Such an arrangement can greatly improve signal to noise ratio by rejecting common mode signals caused by head to media spacing (HMS) variation, change in lube and disc carbon properties, etc.  
         [0024]     The present invention provides a transducer comprised of two members made of essentially one material. This greatly simplifies the wafer process and makes it much less time consuming or expensive. Further, the structure will be essentially insensitive to the lapping process because the structure as presented does not require a controlled stripe height as is required in a conventional design. Also, the structure as presented will be insensitive to any wearing due to contact with the disc. The transducer of the present invention is inherently stable magnetically due to shape anisotropy of the member and due to the flux closure at the end of the tips.  
         [0025]     Since the transient electrons across the head to disc interface see only the first mono-layer of magnetic materials at the end of each member, it is advantageous to ensure the magnetization in this layer be fixed along the desired orientation. Additional measures may be taken to further increase the robustness of surface magnetization. These includes: a) reducing the spacing between the two members to improve flux closure, a typical guideline is that the spacing should be less than the member thickness. b) Use of an antiferromagnetic coupling layer, such as Ru, between the two members to strengthen the antiparallel magnetization of the two members, c) Use of antiferromagnetic material to stabilize the member magnetizations. d) Use tapered shapes at the air bearing end of the member to promote single domain structure.  
         [0026]     The discussion regarding this concept is directed towards perpendicular type writing, but the present invention may be implemented for longitudinal writing as well. Although the concept would remain the same, to implement the present invention, the magnetization in each member would have to be fixed parallel to the air bearing surface because of the nature of longitudinal recording.  
         [0027]     Traditional reader designs rely on the magnetic field emitted from the media being detected by the reader element. The chain of signal transfer is media spin polarization, media field, reader field, reader free layer rotation, and finally magnetoresistive signal. Each of these four steps of transformations involves efficiency losses. They all introduce important design constrains. By detecting the media spin directly, the present invention does not rely on magnetic field detection. As a result, three steps of transformation are removed from the middle of the chain. The media spin polarization is transformed directly into a magnetoresistive signal in the two members.  
         [0028]     The concept discussed in the present invention could be performed using one member, rather than two. If one member were used, the magnetization of the member could not be fixed, because magnetization fixed towards and away from the magnetic media are needed in order to write bits of data on the magnetic media in two directions. Therefore, the magnetization of the member would need to have the ability to be altered, likely using a coil.  
         [0029]     As mentioned above, the present invention can be utilized with magnetic media.  FIGS. 3   a ,  3   b  and  3   c  each show different embodiments of magnetic media.  FIG. 3   a  is a cross-sectional view of the present invention with media  50 . Media  50  includes an overcoat layer  52  and a magnetic storage layer  54 . In this embodiment, the overcoat layer  52  is preferably composed of a metal oxide. In this embodiment, the air between the body  40  and media  50  (also called the fly height), along with the overcoat layer  52  will perform as a barrier layer in a tunneling magnetoresistive sensor, for the reading operation. The fly height should be below 10 nm to ensure good tunneling between the members and the magnetic storage layer  54 , and to ensure a reasonably low bias voltage. An example of an acceptable metal oxide is TiOx, which has a barrier height much below 1.0 eV so that the tunneling resistance remains low when the film has sufficient thickness to protect the magnetic layers. TiOx is a dense and stable material that offers good chemical corrosion resistance and good wearability. The thickness of the overcoat layer  52  should not be greater than 5 nm to ensure proper tunneling.  
         [0030]     Another embodiment, which utilizes magnetic media with the present invention, is  FIG. 3   b . In  FIG. 3   b , an additional layer is positioned on media  50 . A lube layer  56  is added for protection of the disc, but also to provide the option for contact recording. In this embodiment, the fly height, lube layer  56  and overcoat layer  52  all will act as the barrier layer. The lube layer  56  is preferably less than 2 nm. The lube layer  56  should be electrically insulating and a material that does not scatter spins in the transmitting electrons. Perfloropolyether is widely used as lube in the recording industry. Therefore, it appears to be a good candidate for lube in the present invention.  FIG. 3   c  shows another embodiment that utilizes magnetic media with the present invention. In  FIG. 3   c , media  50  is comprised of an overcoat layer  52  and a granular permanent magnet matrix layer  90  (herein “matrix layer”). Matrix layer  90  includes a mixture of magnetic columns  95  and non-magnetic columns  96 . The column shape grain in a matrix layer helps limit the spread of the tunneling current and thus improves bit and track density.  
         [0031]     The current injected from the slider to the media should have a return path.  FIGS. 4   a  and  4   b  show embodiments that provide the injected current with such a path. In  FIG. 4   a , body  40  further includes a current recovery pad  60 . Current recovery pad  60  is composed of a non-magnetic material and preferably has a cross-section that is considerably larger than the first and second members to ensure recovery of the injected current.  FIG. 4   b  illustrates a second embodiment to recover the injected current. In this embodiment, the media  50  is grounded  70 . This can be done, for example, by electrically connecting the media  50  to the spindle  32  (spindle is shown in  FIG. 1 )  
         [0032]      FIG. 5  is a side cross-sectional view of another embodiment of the present invention, wherein the transducer is connected to a differential preamplifier  80 . As discussed above, because the first member  42  and second member  44  function as reader elements of the transducer, two signals for each bit of data will be produced. In order to unify multiple signals and to reduce noise, differential preamplifier  80  is electrically connected to each member. Differential preamplifier  80  can be positioned in or around the slider  40  (as shown in  FIG. 5 ) or can be mounted on a printed circuit board  19  (shown in  FIG. 1 .).  
         [0033]     It is to be understood that even though numerous characteristics and advantages of various embodiments of the present invention have been set forth in the foregoing description, together with details of the structure and function of various embodiments of the invention, this disclosure is illustrative only, and changes may be made in detail, especially in matters of structure and arrangement of parts within the principles of the present invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.