Patent Publication Number: US-8526138-B2

Title: Tandem magnetic writer with independently addressable coils

Description:
RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 12/141,375 filed Jun. 18, 2008, which is herein incorporated by reference. 
    
    
     BACKGROUND 
     The present invention relates to data storage systems, and more particularly, this invention relates to writers. 
     In magnetic storage systems, data is read from and written onto magnetic recording media utilizing magnetic transducers commonly. Data is written on the magnetic recording media by moving a magnetic recording transducer to a position over the media where the data is to be stored. The magnetic recording transducer then generates a magnetic field, which encodes the data into the magnetic media. Data is read from the media by similarly positioning the magnetic read transducer and then sensing the magnetic field of the magnetic media. Read and write operations may be independently synchronized with the movement of the media to ensure that the data can be read from and written to the desired location on the media. 
     An important and continuing goal in the data storage industry is that of increasing the density of data stored on a medium. For tape storage systems, that goal has lead to increasing the track density on recording tape, and decreasing the thickness of the magnetic tape medium. However, the development of small footprint, higher performance tape drive systems has created various problems in the design of a tape head assembly for use in such systems. 
     SUMMARY 
     A magnetic head in one embodiment comprises a pole; a first write gap in the pole; a first coil for generating a magnetic flux across the first write gap; a second write gap in the pole having at least a portion thereof aligned with the first write gap in a direction parallel to a direction of media travel thereover; and a second coil for generating a magnetic flux across the second write gap, the second coil being addressable independently of the first coil. 
     A system in one embodiment comprises a first write gap; a first coil for generating a magnetic flux across the first write gap; a second write gap formed on a common substrate with the first write head and having at least a portion thereof aligned with the first write gap in a direction parallel to a direction of media travel thereover; a second coil for generating a magnetic flux across the second write gap, the second coil being addressable independently of the first coil; the first and second write gaps having about a same track width. 
     A system in yet another embodiment includes a planar tape bearing surface; 
     a first write gap positioned such that a magnetic flux emanates thereacross out of the tape bearing surface; a first coil for generating the magnetic flux across the first write gap, the first coil having portions of several turns aligned in a direction about parallel to a media facing surface; a second write gap positioned such that a magnetic flux emanates thereacross out of the tape bearing surface, the second write gap having at least a portion thereof aligned with the first write gap in a direction parallel to a direction of media travel thereover, wherein a common pole region extends from the first write gap to the second write gap and defines edges of the first and second write gaps; a second coil for generating the magnetic flux across the second write gap, the second coil being addressable independently of the first coil, the second coil having portions of several turns aligned in a direction about parallel to a media facing surface; wherein each of the write gaps is straight along an entire length thereof in a direction parallel to a media facing side thereof, the first and second write gaps being oriented at an angle relative to each other of greater than 0 degrees and less than 180 degrees. 
     A method in one embodiment includes forming a first write coil having portions of several turns aligned in a direction about parallel to a media facing surface; forming a first write gap; forming a second write gap having at least a portion thereof aligned with the first write gap in a direction parallel to a direction of media travel thereover; forming a second coil for generating a magnetic flux across the second write gap, the second coil being addressable independently of the first coil; and forming one or more write poles, wherein a contiguous region of one of the write poles that defines an edge of each of the first and second write gaps is formed concurrently. 
     Any of these embodiments may be implemented in a magnetic data storage system such as a tape drive system, which may include a magnetic head as recited above, a drive mechanism for passing a magnetic medium (e.g., recording tape) over the magnetic head, and a controller electrically coupled to the magnetic head. 
     Other aspects and embodiments of the present invention will become apparent from the following detailed description, which, when taken in conjunction with the drawings, illustrate by way of example the principles of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of a simplified tape drive system according to one embodiment. 
         FIG. 2  illustrates a side view of a flat-lapped, bi-directional, two-module magnetic tape head according to one embodiment. 
         FIG. 2A  is a tape bearing surface view taken from Line  2 A of  FIG. 2 . 
         FIG. 2B  is a detailed view taken from Circle  2 B of  FIG. 2A . 
         FIG. 2C  is a detailed view of a partial tape bearing surface of a pair of modules. 
         FIG. 3  is a partial tape bearing surface of a tandem head according to one embodiment. 
         FIG. 4  is a cross sectional view of  FIG. 3  taken along Line  4 - 4  of  FIG. 3 . 
         FIG. 5  is a partial tape bearing surface of a tandem head according to one embodiment. 
         FIG. 6A  is a cross sectional view of  FIG. 5  taken along Line  6 - 6  of  FIG. 5 . 
         FIG. 6B  is a cross sectional view of a tandem head according to one embodiment. 
         FIG. 7  is a partial tape bearing surface of a tandem head according to one embodiment. 
         FIG. 8  is a partial tape bearing surface of a tandem head according to one embodiment. 
         FIG. 9  is a partial tape bearing surface of a tandem head according to one embodiment. 
         FIG. 10  is a partial tape bearing surface of a tandem head according to one embodiment. 
         FIG. 11  is a partial tape bearing surface of a tandem head according to one embodiment. 
         FIG. 12  is a partial tape bearing surface of a tandem head according to one embodiment. 
         FIGS. 13A-C  illustrate one method for forming a writer. 
         FIGS. 14A-C  illustrate another method for forming a writer. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is made for the purpose of illustrating the general principles of the present invention and is not meant to limit the inventive concepts claimed herein. Further, particular features described herein can be used in combination with other described features in each of the various possible combinations and permutations. 
     Unless otherwise specifically defined herein, all terms are to be given their broadest possible interpretation including meanings implied from the specification as well as meanings understood by those skilled in the art and/or as defined in dictionaries, treatises, etc. 
     It must also be noted that, as used in the specification and the appended claims, the singular forms “a,” “an” and “the” include plural referents unless otherwise specified. 
     The following description discloses several preferred embodiments of tape-based storage systems, as well as operation and/or component parts thereof. 
     In one general embodiment, a magnetic head comprises a pole; a first write gap in the pole; a first coil for generating a magnetic flux across the first write gap; a second write gap in the pole having at least a portion thereof aligned with the first write gap in a direction parallel to a direction of media travel thereover; and a second coil for generating a magnetic flux across the second write gap, the second coil being addressable independently of the first coil. 
     In another general embodiment, a system comprises a first write gap; a first coil for generating a magnetic flux across the first write gap; a second write gap formed on a common substrate with the first write head and having at least a portion thereof aligned with the first write gap in a direction parallel to a direction of media travel thereover; a second coil for generating a magnetic flux across the second write gap, the second coil being addressable independently of the first coil; the first and second write gaps having about a same track width. 
     In another general embodiment, a system comprises a planar tape bearing surface; a first write gap positioned such that a magnetic flux emanates thereacross out of the tape bearing surface; a first coil for generating the magnetic flux across the first write gap; a second write gap positioned such that a magnetic flux emanates thereacross out of the tape bearing surface, the second write gap having at least a portion thereof aligned with the first write gap in a direction parallel to a direction of media travel thereover; and a second coil for generating the magnetic flux across the second write gap, the second coil being addressable independently of the first coil; the first and second write gaps being oriented at an angle relative to each other of greater than 0 degrees and less than 180 degrees. 
     In another general embodiment, a method comprises forming a first write coil; forming a first write gap; forming a second write gap having at least a portion thereof aligned with the first write gap in a direction parallel to a direction of media travel thereover; forming a second coil for generating a magnetic flux across the second write gap, the second coil being addressable independently of the first coil; and forming one or more write poles, wherein a write pole region adjacent the first and second write gaps is formed concurrently. 
       FIG. 1  illustrates a simplified tape drive  100  of a tape-based data storage system, which may be employed in the context of the present invention. While one specific implementation of a tape drive is shown in  FIG. 1 , it should be noted that the embodiments described herein may be implemented in the context of any type of tape drive system. 
     As shown, a tape supply cartridge  120  and a take-up reel  121  are provided to support a tape  122 . One or more of the reels may form part of a removable cassette and are not necessarily part of the system  100 . The tape drive, such as that illustrated in  FIG. 1 , may further include drive motor(s) to drive the tape supply cartridge  120  and the take-up reel  121  to move the tape  122  over a tape head  126  of any type. 
     Guides  125  guide the tape  122  across the tape head  126 . Such tape head  126  is in turn coupled to a controller assembly  128  via a cable  130 . The controller  128  typically controls head functions such as servo following, writing, reading, etc. The cable  130  may include read/write circuits to transmit data to the head  126  to be recorded on the tape  122  and to receive data read by the head  126  from the tape  122 . An actuator  132  controls position of the head  126  relative to the tape  122 . 
     An interface may also be provided for communication between the tape drive and a host (integral or external) to send and receive the data and for controlling the operation of the tape drive and communicating the status of the tape drive to the host, all as will be understood by those of skill in the art. 
     By way of example,  FIG. 2  illustrates a side view of a flat-lapped, bi-directional, two-module magnetic tape head  200  which may be implemented in the context of the present invention. As shown, the head includes a pair of bases  202 , each equipped with a module  204 , and fixed at a small angle α with respect to each other. The bases are typically “U-beams” that are adhesively coupled together. Each module  204  includes a substrate  204 A and a closure  204 B with a gap  206  comprising readers and/or writers situated therebetween. In use, a tape  208  is moved over the modules  204  along a media (tape) bearing surface  209  in the manner shown for reading and writing data on the tape  208  using the readers and writers. The wrap angle θ of the tape  208  at edges going onto and exiting the flat media support surfaces  209  are usually between ⅛ degree and 4½ degrees. 
     The substrates  204 A are typically constructed of a wear resistant material, such as a ceramic. The closures  204 B made of the same or similar ceramic as the substrates  204 A. 
     The readers and writers may be arranged in a piggyback configuration. The readers and writers may also be arranged in an interleaved configuration. Alternatively, each array of channels may be readers or writers only. Any of these arrays may contain one or more servo readers. 
       FIG. 2A  illustrates the tape bearing surface  209  of one of the modules  204  taken from Line  2 A of  FIG. 2 . A representative tape  208  is shown in dashed lines. The module  204  is preferably long enough to be able to support the tape as the head steps between data bands. 
     In this example, the tape  208  includes 4-22 data bands, e.g., with 16 data bands and 17 servo tracks  210 , as shown in  FIG. 2A  on a one-half inch wide tape  208 . The data bands are defined between servo tracks  210 . Each data band may include a number of data tracks, for example 96 data tracks (not shown). During read/write operations, the elements  206  are positioned within one of the data bands. Outer readers, sometimes called servo readers, read the servo tracks  210 . The servo signals are in turn used to keep the elements  206  aligned with a particular track during the read/write operations. 
       FIG. 2B  depicts a plurality of read and/or write elements  206  formed in a gap  218  on the module  204  in Circle  2 B of  FIG. 2A . As shown, the array of elements  206  includes, for example, 16 writers  214 , 16 readers  216  and two servo readers  212 , though the number of elements may vary. Illustrative embodiments include 8, 16, 32, and 64 elements per array  206 . A preferred embodiment includes 32 readers per array and/or 32 writers per array. This allows the tape to travel more slowly, thereby reducing speed-induced tracking and mechanical difficulties. While the readers and writers may be arranged in a piggyback configuration as shown in  FIG. 2B , the readers  216  and writers  214  may also be arranged in an interleaved configuration. Alternatively, each array of elements  206  may be readers or writers only, and the arrays may contain one or more servo readers  212 . As noted by considering FIGS.  2  and  2 A-B together, each module  204  may include a complementary set of elements  206  for such things as bi-directional reading and writing, read-while-write capability, backward compatibility, etc. 
       FIG. 2C  shows a partial tape bearing surface view of complimentary modules of a magnetic tape head  200  according to one embodiment. In this embodiment, each module has a plurality of read/write (R/W) pairs in a piggyback configuration formed on a common substrate  204 A and an optional electrically insulative layer  236 . The writers, exemplified by the write head  214  and the readers, exemplified by the read head  216 , are aligned parallel to a direction of travel of a tape medium thereacross to form an R/W pair, exemplified by the R/W pair  222 . 
     Several R/W pairs  222  may be present, such as 8, 16, 32 pairs, etc. The R/W pairs  222  as shown are linearly aligned in a direction generally perpendicular to a direction of tape travel thereacross. However, the pairs may also be aligned diagonally, etc. Servo readers  212  are positioned on the outside of the array of R/W pairs, the function of which is well known. 
     Generally, the magnetic tape medium moves in either a forward or reverse direction as indicated by arrow  220 . The magnetic tape medium and head assembly  200  operate in a transducing relationship in the manner well-known in the art. The piggybacked MR head assembly  200  includes two thin-film modules  224  and  226  of generally identical construction. 
     Modules  224  and  226  are joined together with a space present between closures  204 B thereof (partially shown) to form a single physical unit to provide read-while-write capability by activating the writer of the leading module and reader of the trailing module aligned with the writer of the leading module parallel to the direction of tape travel relative thereto. When a module  224 ,  226  of a piggyback head  200  is constructed, layers are formed in the gap  218  created above an electrically conductive substrate  204 A (partially shown), e.g., of AlTiC, in generally the following order for the R/W pairs  222 : an insulating layer  236 , a first shield  232  typically of an iron alloy such as NiFe (permalloy), CZT or Al—Fe—Si (Sendust), a sensor  234  for sensing a data track on a magnetic medium, a second shield  238  typically of a nickel-iron alloy (e.g., 80/20 Permalloy), first and second writer pole tips  228 ,  230 , and a coil (not shown). 
     The first and second writer poles  228 ,  230  may be fabricated from high magnetic moment materials such as 45/55 NiFe. Note that these materials are provided by way of example only, and other materials may be used. Additional layers such as insulation between the shields and/or pole tips and an insulation layer surrounding the sensor may be present. Illustrative materials for the insulation include alumina and other oxides, insulative polymers, etc. 
     In particularly preferred embodiments, a head includes two or more independently addressable write gaps, where the gaps generally lie along a line oriented parallel to a direction of tape travel thereacross. While such heads may be used for any type of recording, including data recording, the heads are especially useful for writing servo patterns to a magnetic medium such as a tape. 
     Magnetic tape uses a written servo pattern to indicate the lateral position on tape. This servo pattern is used to indicate the lateral position, on tape, of the various written tracks. The servo pattern is not perfect due to variations in tape velocity and lateral tape motion in the servo writer system during servo writing. The component of the servo pattern due to the velocity variations and lateral motion is termed the ‘written in’ component and interferes with capabilities of the track following actuator in the drive. For example, components of the ‘written in’ servo can be incorrectly interpreted by the track following actuator as lateral positioning error and so cause the head to move in response thus resulting in mistracking. Greater trackfollowing accuracy becomes more important as written tracks get narrower. Hence ‘written in’ servo noise limits the ultimate track pitch attainable in magnetic tape recording. 
     In use, some of the embodiments described herein may be used as a servo writer using methods such as those described in U.S. patent application Ser. No. 12/141,363 to Biskeborn et al., having title “Systems and Methods for Writing Servo Patterns,” filed concurrently herewith, and which is herein incorporated by reference. 
     In one general approach, tandem heads include a first write gap, a first coil for generating a magnetic flux across the first write gap, a second write gap having at least a portion thereof aligned with the first write gap in a direction parallel to a direction of media travel thereover, and a second coil for generating a magnetic flux across the second write gap, the second coil being addressable independently of the first coil; 
       FIG. 3  illustrates a tandem head  300  according to one embodiment.  FIG. 4  shows a cross section of  FIG. 3  taken along Line  4 - 4 . As shown, the tandem head  300  has a pole  305  with first and second write gaps  302 ,  304  therein, and independently addressable first and second coils  306 ,  308 . The first coil  306  is operative to cause a magnetic flux to emanate from the first gap  302 . The second coil  308  is operative to cause a magnetic flux to emanate from gap  304 . 
     As noted below, the write gaps  302 ,  304  in this and other embodiments may be concurrently formed. This has the advantage of allowing precise alignment of the write gaps. Also, the various regions of the pole  305  may be concurrently formed in this and other embodiments. 
       FIG. 5  illustrates a tandem head  300  having two write gaps  302 ,  304  and independently addressable coils  306 ,  308 . Coil  306  is operative to cause a magnetic flux to emanate from gap  302 . Coil  308  is operative to cause a magnetic flux to emanate from gap  304 . 
     As also shown in  FIG. 5 , wing portions  504  may be added to this and other embodiments to reduce the possibility of saturation at the ends of the gaps. Preferably, the angles α of the wing portion and central region  502  of the pole  305  relative to an imaginary line coaxial extending along the gap are about the same. 
       FIG. 6A  shows a cross section of  FIG. 5  taken along Line  6 - 6 , with external coil wraps shown. As shown, the tandem head  300  has first and second write gaps  302 ,  304  and independently addressable first and second coils  306 ,  308  configured in a pancake configuration. 
       FIG. 6B  shows an alternate embodiment of a tandem head  300  having first and second write gaps  302 ,  304  and independently addressable first and second coils  306 ,  308  configured in a helical configuration. Also, the top pole includes multiple layers in this embodiment. 
     In some embodiments, such as the embodiment shown in  FIG. 4 , the tape bearing surface of the head is planar. In other embodiments, the tape head may be curved, arcuate, semicylindrical, etc. 
     In some embodiments, as exemplified by  FIGS. 3-4 , tandem heads  300  may be fabricated with a space  310  separating the segments. The space may be a void or filled, e.g., formed of a nonmagnetic material, etc. Also, as shown in  FIG. 4 , the segments may be formed on some base material  312 , which may comprise a wafer and insulating layer. 
     In other embodiments, as exemplified by  FIGS. 5-6 , tandem heads  300  may share a common pole region  502 . 
     The materials used to construct the tandem writers described herein may be conventional writer materials, and/or specialty materials. In preferred approaches, the yoke portions of the writers are constructed of a high magnetic permeability material such as permalloy (80/20 NiFe), etc. The portions of the write pole regions at least near the write gaps are preferably constructed of a high magnetic saturation (e.g., high B s ) material such as alloys of iron with Ni, Co, and/or Al, etc. One illustrative material is 45/55 NiFe. 
     As exemplified in  FIG. 6A , the upper pole regions may be tapered near the write gaps. This tapering focuses the fringing fields at the write gap, improving writing efficacy. In a variation, exemplified by  FIG. 6B , the top pole may be or include a second layer. 
     As evident from  FIGS. 3 and 5 , the first and second write gaps may be oriented at an angle relative to each other of greater than 0 and less than 180 degrees. For example, the write gaps may be oriented between about 1 and about 179 degrees, between about 5 and about 175 degrees relative to each other, or any subrange between 0 and 180 degrees. Accordingly, because of the angling, controlled firing of each of the write gaps may be used to form the distinctive carat, N, M, etc. magnetic patterns in a servo or data track. See, e.g.,  FIG. 7 , showing a tandem head  300  having a first gap  304  oriented about perpendicular to the direction of tape travel and a second gap  302  oriented at an angle relative to the first gap  304  of greater than 0 and less than 180 degrees. In another illustrative approach, the first write gap is oriented at an angle of between about 2 and about 88 relative to the direction of media travel thereover, while the second write gap may also be oriented at an angle of between about 2 and about 88 (which is intended to encompass between about −2 and about −88 degrees) relative to the direction of media travel thereover. 
     In other embodiments, the gaps may be oriented for writing data, such as conventional or azimuthal data recording. In one approach (e.g., as in  FIG. 11 ), some of the write gaps may be oriented about parallel to each other and may be used for DC erasing tape. 
     In other embodiments, each segment may contain at least one write gap. For example, as exemplified by  FIG. 8 , one approach may have one write gap  302  in a first segment, and two write gaps  304 ,  802  in a second segment. Such a writer may be particularly useful where gap  302  is used to erase a data track on a tape, while gaps  304 ,  802  write a servo or data pattern. Note that each of the gaps  302 ,  304 ,  802  may be independently addressable, or some may share a coil, as discussed below. In another example, the head may have two or more write gaps in each segment. See, e.g.,  FIG. 12 , discussed below. 
     In further embodiments, more than two segments may be present, each with one or more independently addressable write gaps, oriented in any orientation. See, e.g.,  FIG. 9 , depicting a tandem head  300  with three segments, each having a write gap  302 ,  304 ,  902 . 
       FIG. 9  also illustrates that the gaps in this or any other embodiment do not need to extend to the ends of the pole. As shown, the gaps may be positioned in the face of the upper pole. Optional bulbous ends on the gaps improve the uniformity of the flux along the gap. 
     The examples of  FIGS. 5-9  show embodiments where centers of the gaps generally lie along a line oriented parallel to a direction of tape travel thereacross, e.g., are centered on the line. However, in other embodiments, exemplified by  FIGS. 10 and 11 , the write gaps  302 ,  304  have offset centers relative to the direction of tape travel thereacross. 
     In some embodiments, the first and second write gaps may have about a same track width. In further embodiments, the first and second write gaps have different track widths. See, e.g.,  FIG. 11 . 
     In further embodiments, one or more segments may include multiple write gaps that are addressed by the same coil. For example,  FIG. 12  illustrates an embodiment  300  having pairs  302  and  1202 ,  304  and  1204 , of write gaps that share a coil, where each coil, and thus each pair of write gaps, is independently addressable. See also  FIG. 8 , where gap  302  may be addressed independently of gaps  304  and  802 . 
     Note also that the gaps need not be centrally located on a given pole region. Rather, it may be desirable for asymmetric placement of a gap in some embodiments. See, e.g.,  FIG. 7 . 
       FIGS. 13A-C  illustrate one method for forming a writer. Conventional processing may be used to form the various parts. Referring to  FIG. 13A , first and second write coils  306 ,  308  are formed. First and second write gaps  302 ,  304  are also formed. Referring to  FIG. 13B , material is deposited for concurrently forming write pole regions  1202 , which may or may not be defined at this point. Referring to  FIG. 13C , the structure is planarized. 
       FIGS. 14A-C  illustrate another method for forming a writer. Again, processing may be used to form the various parts. Referring to  FIG. 14A , first and second write coils  306 ,  308  are formed. Write pole regions  1402  are also formed. Write gap material  1404  is formed over the write pole regions, as shown in  FIG. 14B . Further processing may be performed prior to formation of a common write pole region  1406  adjacent first and second write gaps  302 ,  304 , as shown in  FIG. 14C . 
     While various embodiments have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of a preferred embodiment should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.