Servo write head having plural spaced front blocks coupled by magnetic posts to a back bar

An assembly comprises a plurality of laterally spaced front blocks, a magnetic post coupling each of the front blocks to a common back bar, and a common front bar magnetically coupled to the back bar. A write gap spacer is positioned between the front bar and each of the plurality of front blocks, and a write gap element comprising write gaps couples the front bar to each front block across the write gap spacer. A coil is configured to generate magnetic flux in each magnetic post, and the front blocks are configured to direct the magnetic flux across the write gaps.

RELATED U.S. APPLICATION DATA

This application claims priority to U.S. provisional Application No. 61/638,806, filed Apr. 26, 2012, and incorporated herein by reference.

The subject matter of this application is also related to that of the following applications, each of which is incorporated by reference in its entirety for all purposes: U.S. non-provisional application Ser. No. 13/795,482, entitled “TAPERED POLE HEADS FOR MAGNETIC MEDIA”, filed on even date herewith, which claims priority to U.S. provisional Application No. 61/638,820, filed Apr. 26, 2012; U.S. non-provisional application Ser. No. 13/795,668, entitled “METHODS AND SYSTEMS FOR MAGNETIC MEDIA SERVO WRITING”, filed on even date herewith, which claims priority to U.S. provisional Application No. 61/638,767, filed Apr. 26, 2012; U.S. non-provisional application Ser. No. 13/79421, entitled “SYSTEMS AND METHODS FOR PROCESSING MAGNETIC MEDIA”, filed on even date herewith, which claims priority to U.S. provisional Application No. 61/638,832, filed Apr. 26, 2012; and U.S. non-provisional application Ser. No. 13/754,078, entitled “PERPENDICULAR POLE HEAD FOR SERVO WRITING MAGNETIC MEDIA”, filed Jan. 30, 2013, which claims priority to U.S. provisional Application No. 61/620,199, filed Apr. 4, 2012.

BACKGROUND

Magnetic tape-based data storage systems provide secure, reliable, cost-efficient, and scalable solutions for information processing in business, industry, and government service applications. Cartridge-based magnetic tape systems combine efficiency and ease of use in regulated bulk storage environments, and are adaptable for use with online, nearline, offline, and offsite infrastructures to relay large datasets, ensure regulatory compliance, and safeguard critical information while lowering data storage costs and service time.

Magnetic tape storage media provide high data density and capacity, with adaptable performance criteria suitable for a wide range of backup, archiving, and portable data storage needs. As storage densities and access speeds increase, however, substantial engineering demands are made on the tape cartridge and servo system, which must provide precise speed control and head positioning in order to quickly, accurately, and reliably read and write data to and from the recording medium.

To provide precision head positioning, servo tracks are recorded onto the medium during the formatting or manufacturing process. The servo control system reads the servo patterns, and uses a time-based pattern conversion to determine head position based on the servo signal. Representative servo system technologies are described in the following U.S. patent documents, each of which is incorporated by reference herein: Molstad et al., U.S. Pat. No. 6,542,325, TIME-BASED SERVO FOR MAGNETIC STORAGE MEDIA, issued Apr. 1, 2003, and assigned to Imation Corp. of Oakdale, Minn.; Molstad et al., U.S. Pat. No. 6,781,778, TIME-BASED SECTORED SERVO DATA FORMAT, issued Aug. 24, 2004, and assigned to Imation Corp. of Oakdale, Minn.; and Johnson et al., U.S. Pat. No. 6,950,269, SYSTEM AND METHODS FOR USING SERVOPOSITIONING SIGNALS, issued Sep. 17, 2005, and assigned to Imation Corp. of Oakdale, Minn.

Overall read and write performance thus depends on the servo system capabilities, and specifically on servo head design. In particular, the servo head should be adaptable to read and write a variety of different servo patterns, with increased timing response for precise head positioning and increased read and write performance for a range of high density, high data rate magnetic storage systems.

SUMMARY

Exemplary embodiments of the present disclosure include magnetic head assemblies, magnetic heads, and magnetic head systems. Assembly embodiments may comprise a plurality of laterally spaced front blocks, magnetic posts coupling each front block to a back bar, which may be a common back bar, and a front bar, which may be a common front bar, magnetically coupled to the back bar. A write gap spacer may be positioned between the front bar and each of the front blocks, and a write gap element may couple the front bar to each front block across the write gap spacer. The write gap element may comprise write gaps, and a coil may be configured to generate magnetic flux in each magnetic post, such that the front blocks direct the magnetic flux across the write gaps of each write gap element.

Magnetic head embodiments may include a plurality of laterally spaced front blocks, where each front block is magnetically coupled to a write gap element having at least two write gaps. A plurality of vias may couple the front blocks to a common back bar, and a plurality of coils may generate magnetic flux in the vias, where the laterally spaced front blocks direct the flux across the write gap elements. A front bar may magnetically couple the common back bar to each of the write gap elements, forming a return path for the magnetic flux.

System embodiments may include a magnetic medium facing a magnetic head. The magnetic head may include pluralities of write gap elements and front blocks spaced laterally across the magnetic medium, where the front blocks are coupled to the write gap elements and each write gap element has at least two write gaps. A via may couple each of the front blocks to a common back bar, and a coil may be configured to generate magnetic flux in each via. The front bar may couple each of the front blocks to the common back bar, providing a return path for the magnetic flux.

DETAILED DESCRIPTION

FIG. 1is a schematic view of system10for processing magnetic medium12, for example a tape-based data storage medium12with magnetic recording layer or coating12A on substrate12B. In this particular example, system10includes erasure or formatting head14, write head16, read head18, and one or more guides20. Depending on application, system10may also include other components including, but not limited to, tension control devices, vacuum columns, polishing and cleaning elements, and additional magnetic heads or other components for further read, write, erase, and formatting operations on magnetic medium12.

Tape guides or rollers20guide magnetic medium12through system10along media travel direction T (arrows), for example from supply reel22to take-up reel24. Erase head14provides a particular magnetic domain orientation or bias along magnetic coating12A of magnetic medium12. Write head16provides improved magnetic field and flux guiding structures to write a servo pattern or other data onto magnetic medium12, as described below. Read head18generates servo signal (or other read signal) S based on the data patterns generated by write head16.

Magnetic medium12is typically formed by binding magnetic coating12A to a substrate or base film12B, for example a polymer such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN). Suitable magnetic coatings12A include magnetic particles or a magnetic powder in a binder such as a thermoplastic resin, and may be configured for either longitudinal or perpendicular recording. Magnetic coating12A may also include a head cleaning agent (HCA) such as alumina or aluminum oxide pigment particles, abrasive grains such as silica, or both, along with other resin or binder components such as surfactants, lubricants, and hardeners. Magnetic coating12A may also include a hard magnetic film coating, such as one produced using an evaporation process, or produced using sputtering, or produced using another technique.

A back coat may be applied to substrate12B, opposite magnetic coating12A, for example silicon dioxide or carbon black pigment particles, or both, with a blend of polymer resin or nitrocellulose binders to provide stiffness, reduce friction, dissipate static charge, and maintain uniform tape wind. Alternatively, the orientation of magnetic coating12A and back coat or substrate surface12B may be reversed, or magnetic coatings may be provided on both surfaces12A and12B of magnetic medium12. It should be recognized, moreover, that the present invention may also be used with any suitable type of tape or any suitable type of media, as desired, including, but not limited to, magnetic tapes and other digital data storage media, audio and video tapes, and other magnetic media configured for analog or digital recording.

FIG. 2is a perspective view of magnetic head assembly30, for example servo write head16of processing system10, as described above, or another write head30for generating data patterns on magnetic medium12. In this particular example, magnetic head30assembly includes back bar32, front bar34, write gap spacers36, front blocks38, block spacers40, write gap elements42with gap structures44, and coil component46.

Leading and trailing portions48and50of magnetic head assembly (or magnetic head)30are defined with respect to media travel direction T of the magnetic medium (arrow). Depending on application, media travel direction T may also be reversed, without loss of generality. Leading portion48may include leading edge48A, that is, a part of leading portion48that contacts the magnetic medium12. Similarly, trailing portion50may include trailing edge50A, that is, a part of trailing portion50that contacts the magnetic medium12.

Back bar or back core32is generally formed of a soft magnetic material to create a flux return path for directing magnetic flux through head30. Suitable materials for common back bar32include high permeability, low coercivity, high saturation magnetic materials, for example ferromagnetic alloys and ferrite materials including, but not limited to, manganese zinc ferrite and nickel zinc ferrite. As shown inFIG. 2, back bar32may also be formed as a common magnetic core or back bar element, in a substantially unitary form with magnetic couplings to front bar34along leading portion48and leading edge48A of magnetic head30, and to each of front blocks38along trailing portion50and trailing edge50A of magnetic head30.

The magnetic couplings between back bar32and front blocks38are formed by magnetic posts or vias52A. Magnetic posts52A are typically formed of a soft magnetic core material, for example a material similar to or substantially the same as that of back bar32and/or front blocks38. One or more magnetic posts52A may thus be formed as an integral or unitary structure with back bar32, or with one or more front blocks38. Alternatively, one or more magnetic posts52A may be formed as a separate magnetic element, with magnetic couplings to back bar32and front blocks38at opposite ends.

Front bar or front core34may be formed of substantially the same or similar materials (e.g., soft magnetic core materials) as back bar32and/or posts52A, or other suitable magnetic materials. As shown inFIG. 2, front bar34may also be configured as a common or substantially unitary magnetic core element, with couplings to common back bar32via magnetic posts52B, and with integrated front bar pole or core portions34A for coupling to each of front blocks38, across write gap spacers36.

In a preferred embodiment, the gap structures44are formed in a very high saturation flux density high permeability magnetic film42. The magnetic film42may be composed of Fe—Ta—N, Fe—Al—N, Fe—Ni—N, Fe—N, Co—Fe, Co—Zr—Ta, Al—Fe—Si, Fe—Ni, other materials, or mixtures of these.

Magnetic posts52B are formed of substantially the same or similar materials as those of magnetic posts52A, back bar32, and front bar34. Thus, magnetic posts52B may be formed integrally or as a unitary structure with back bar32, front bar34, or both. Alternatively, one or more magnetic posts52B may be formed as discrete magnetic structures, coupling to back bar32and front bar34at opposite ends. Similarly, front bar cores34A may be integrally formed as a unitary structure with a common front bar34, or configured as separate magnetic elements with individual magnetic couplings to front bar34, opposite write gap spacers36.

Write gap spacers (or gap spacers)36are typically formed of a non-magnetic material, such as silica or silica-based glass, or another ceramic or nonmagnetic metal material. Write gap elements42couple front bar cores34A to front blocks38, across write gap spacers36.

One or more coils56are positioned about magnetic posts52A in order to generate magnetic flux. Coils56are formed of a conducting material such as copper, for example in the form of a thin film or flex circuit coil component46. Coils56can be coupled to leads56A, which can be coupled to an electronic circuit or another energy source.

In one embodiment, coils56and leads56A can be disposed on a flexible coil component46, as shown in the figure. In first alternative embodiments, coils56and leads56A may be disposed on a flexible coil component46having multiple layers with appropriate vias to reduce current and increase inductance. In second alternative embodiments, coils56may be disposed on the flexible coil component46with a relatively larger portion of one or more coils56to a side of magnetic posts52A or52B or both, with the effect of providing relatively improved heat dissipation. In third alternative embodiments, coils56may include one or more formed wire coils disposed on the flexible coil component46. In fourth alternative embodiments, coils56may be disposed around magnetic posts52A or52B or both, on opposite sides of the magnetic head30, with the effect of providing relatively improved heat dissipation and relatively reduced coupling.

Coils56are energized with electric current, such as using leads56A, to generate magnetic flux in magnetic posts52A and front blocks38. Front blocks38direct the flux across write gap spacers36through write gap elements42, in order to write servo patterns or other data to magnetic medium12at write gap structures44. Front bar cores34A direct the flux from write gap elements42to common front bar34, which is coupled to common back bar32to provide a flux return path.

In discrete coil configurations, individual coils56are separately controllable to write different data patterns across each write gap structure44. Alternatively, one or more coils56may be energized in a coordinated fashion, or replaced with a common coil component46positioned about two or more magnetic posts52A or front blocks38, in order to generate similar or substantially the same data patterns across two or more write gap structures44.

Intermediate blocks38B are laterally spaced between front blocks38by block spacers40. End blocks38C are provided at the sides or opposite lateral ends (e.g., top and bottom) of magnetic head30, with additional block spacers40to space end blocks38C from adjacent front blocks38along the opposite lateral edges of back bar32and front bar34.

Front bar cores34B, intermediate blocks38B, end cores34C, and end blocks38C are formed of soft magnetic core materials, as described above, in order to direct and contain magnetic flux. Intermediate blocks38B are coupled to front bar34via intermediate cores34B, and end blocks38C are coupled to front bar34via end cores34C. Along trailing edge portion50, intermediate blocks38B and end blocks38C may be spaced from magnetic posts or vias52A across block spacers40, so that intermediate cores34B and intermediate blocks38B are substantially decoupled from back bar32and substantially decoupled from coils56.

Thus, intermediate blocks38B and intermediate poles34B function as shield elements, in order to prevent stray magnetic flux from magnetizing the data bands between adjacent pairs of front blocks38. End blocks38C and end cores34C may perform similar shielding functions along the top and bottom edges of magnetic medium12.

In operation of magnetic head30, magnetic medium12tracks past magnetic head30at a particular fly height, or in (direct) head-medium contact, with relative motion along media travel direction T. Coils56are energized to generate magnetic flux through posts52A and front blocks38, and magnetic head30writes servo tracks or other data onto magnetic medium12by directing the magnetic flux across write gap structures44in write gap elements42.

As shown inFIG. 2, for example, five thin film write gap elements42are laterally spaced across magnetic head30, and positioned across write gap spacer36to couple five similarly spaced front blocks38to one or more front bar cores34A in common front bar34. Front blocks38and write gap structures44thus define five servo track regions or servo bands57along magnetic medium12, alternating with four data bands58. Data bands58are defined by four laterally spaced intermediate (shield) blocks38B and intermediate (shield) cores34B, so that data bands58extend along magnetic medium12between adjacent pairs of servo bands57.

Depending on manufacturing process and application, write gap spacer36may also extend across one or more of intermediate blocks (or shields)38B and end blocks38C, with coupling across write gap spacer36provided by additional thin film or other magnetic elements59, as shown inFIG. 2. Magnetic shield elements59are typically formed without write gap structures44, in order to provide additional magnetic shielding, and to prevent stray flux from biasing the magnetic coating in the data and side bands. In one embodiment, magnetic shield elements59include the same or similar material as write gap elements42. In the figure, although there are multiple magnetic shield elements59shown, there is one write gap spacer36that extends across substantially the entire common front bar34. Write gap structures44in magnetic shield elements59covering front blocks38allow writing patterns to servo bands57, while the lack of write gap structures44in magnetic shield elements59covering intermediate blocks38B and end blocks38C prevent writing patterns to data bands58. Alternatively, one or more intermediate blocks38B or end blocks38C may be coupled to a coil56, and additional write gap structures44may be provided to write data patterns onto data tracks or side bands of magnetic medium12.

This particular configuration is thus merely representative. In other examples, magnetic head30can be configured with any number of front blocks38and write gap structures44to generate five (or, in alternative embodiments, some other number) servo bands57. Alternatively, magnetic head30may be configured with additional write gap structures44to write data patterns onto any combination of servo bands57, data bands58and additional side bands, as described above. Further, the individual servo and data patterns may also take on any desired form, some of which are described below.

FIG. 3is schematic illustration of servo or data pattern60as defined along on servo band61of magnetic recording medium12. Magnetic recording medium12is shown in a top-down view, with the magnetic coating or recording surface on either the front or back side of magnetic medium12.

In the particular example ofFIG. 3, data pattern60is represented by a series of similar or substantially identical sets of pattern lines63,64, and65, forming N-shaped servo frames62along centerline L of servo band61. Width W of pattern60is defined generally perpendicularly to center line L, between lateral edges or sides S or pattern lines63,64, and65.

Data pattern60may extend continuously along substantially the entire length of magnetic medium12, or be formed in particular sectors, for example at the beginning and end of magnetic medium12, or in periodic locations along magnetic medium12. Data pattern60may also represent either a servo pattern or more generalized data, for example generic binary data written to a data band.

In formatting applications, servo or data frames62may be written to magnetic medium12during a manufacturing, formatting or reformatting process, for use as a reference to position the data heads during read and write operations on data tracks located between the servo bands. For example, individual frames62may be written at times t0, t1, t2, etc., as shown inFIG. 3, with substantially perpendicular pattern lines63and65in reference regions66and68. Diagonal pattern line64extends across servo region67at skew angle α, forming an N-shaped pattern (“|\|”) in each frame62.

Servo signal timing depends on the relative position of pattern lines63,64, and65. As magnetic medium12translates along center line L, read head18generates a corresponding series of servo transition signals, or read pulses. Based on the signal timing, perpendicular (or parallel) pattern lines63and65define reference distance dref, which is relatively constant across width W of data pattern60, and diagonal (or skew) pattern line64defines tracking distance dtrk, which varies across width W. (While a relatively constant reference distance drefcan be preferred in many embodiments, in the context of the invention there is no particular requirement for any such limitation.) The time intervals can thus be used to generate a position signal corresponding to the location of read head18, based on the ratio dtrk/dref. The servo signals are used to position read and write heads along particular data tracks, as defined between the servo bands.

Although lines63,64, and65are shown as individual pattern lines, in a preferred embodiment, each line can be recorded multiple times in parallel in each frame, such as about four or five or some other number of times. This has the effect that line63, recorded as four or five (or some other number) of lines, can be more easily recognized than a single line. Similarly, lines64and65can be recorded multiple times in parallel in each frame, with the effect that lines64and65, recorded as four for five (or some other number) of lines, can be more easily recognized than a single line.

In one embodiment, current is pulsed alternately in four pulse bursts or five pulse bursts. The pulse bursts are completed such that four or five pattern lines63are recorded on the magnetic medium12in less space than the distance between pattern lines63and pattern lines64. Similarly, the pulse bursts are completed such that four or five pattern lines64and65are recorded on the magnetic medium12in less space than the distance between pattern lines63and65(for pattern lines64) or between pattern lines64and the next data pattern60(for pattern lines65). The pulse bursts to generate the next data pattern60occur only after the magnetic medium12has moved sufficiently that pattern lines65and63do not overlap.

In particular, the ratio dtrk/drefdepends on skew angle α. Angle α may range from at least about 2 degrees to about 10 degrees or more, for example about 2-10 degrees, or about 6 degrees, within a tolerance of about ±0.5 degree or about ±0.1 degree, or between about 5 degrees and about 7 degrees. Alternatively, angle α may range above about 10 degrees, for example about 10-20 degrees, or greater than about 20 degrees. Frames62may also be reversed, forming a “|/|” or “inverted N” servo frame. Other servo and data patterns60may also be generated with different data frames62, as described below.

FIG. 4is a front or media-facing surface view of write gap element42for magnetic head30, with write gap structure44. In this particular example, write gap structure44has three individual write gaps73,74, and75, corresponding to an N-shaped servo data pattern60, as shown inFIG. 3.

Write gap element42may be formed of a thin sheet or thin film of magnetically permeable material with high saturation flux density and low coercivity, in order to guide magnetic flux across write gap spacer36to write gaps73,74, and75. Suitable materials for write gap element42include, but are not limited to, Fe—Ni, Co—Zr—Ta, Fe—Ni—N, Fe—Ta—N, Fe—Al—N, Fe—Si—N, and Co—Fe.

Write gaps73,74, and75may have a substantially symmetric configuration about center line L′ of write gap structure44, with write gap width W′ corresponding to width W across centerline L of servo data pattern60. Write gap74may also be formed at angle α with respect to generally parallel or perpendicular write gaps73and75, in order to write a diagonal or skew servo line between parallel reference lines, as described above.

To increase field strength across the full width W of write gap structure44, end features76may be provided at the lateral (top and bottom) edges of one or more write gaps73,74, and75. End features76may have a different shape, including a generally circular geometry, as shown inFIG. 4, in order to increase the width of write gaps73,74, and75, and to generate more uniform field strength across width W of write gap structure44. Alternatively, end features76may have an oblate, elliptical, square, rectangular or diamond-shaped geometry, or another shape or geometry suitable for increasing field strength and servo pattern uniformity.

FIG. 5Ais a schematic view of an alternate servo data pattern60for magnetic medium12. In this example, individual frames62of servo data pattern60are formed as an alternating series of transverse or perpendicular pattern lines82and diagonal or skew pattern lines83. Alternatively, frames62′ may be defined by alternating pairs of diagonal pattern lines83, followed by transverse pattern lines82.

Servo or data frames62are written to magnetic medium12by forming pairs of pattern lines or stripes82and83at times T0, T1, T2, etc., as described above. As shown inFIG. 5A, pattern lines82and83are substantially symmetric across centerline L, defining a servo read signal or positioning signal based on the magnetic field transitions at the beginnings and ends of transverse pattern line82and diagonal pattern line83.

The transition times define distance A between different pattern lines82and83, where distance A varies across width W of servo data pattern60. Distance B, however, is substantially constant, as defined between pairs of the same pattern lines82,82(or83,83). The transverse position of the read head is thus determined by the ratio A/B, similar to the corresponding ratio of tracking and reference distances dtrkand dref, as described above.

FIG. 5Bis a schematic view of a second alternate servo data pattern60for magnetic medium12. In this example, individual frames62each include a transverse pattern line84, followed by a chevron-shaped pattern line85. Alternate frames62′ have chevron pattern line85followed by transverse pattern line84.

Chevron pattern lines85have two legs meeting at a cusp or vertex V, for example with vertices V aligned along centerline L of servo data pattern60, as shown inFIG. 5B. Pattern lines84and85define magnetic transitions corresponding to variable distance A and fixed (reference) width B, as described above, with head positioning determined by the ratio A/B.

FIG. 5Cis a schematic view of a third alternate servo data pattern60for magnetic medium12. As shown inFIG. 5C, servo or data frames62are formed of two chevron pattern lines86and87, with opposing vertices V aligned in an outward sense along centerline L of servo data pattern60. Alternatively, frames62′ are defined by chevron pattern lines87and86, with vertices V aligned in an inward sense along centerline L.

FIG. 6Ais a schematic view of write gap element42for magnetic head30, with an alternate configuration for write gap structure44. In this particular example, write gap structure44includes a first (transverse) write gap92and a second (diagonal or skew) write gap93. Write gap92makes angle α with respect to write gap93, for example to generate pattern lines82and83for servo data pattern60ofFIG. 5A, as described above.

As shown inFIG. 6A, end features76are formed as oblate or elliptical features, with geometry selected to improve field strength at the ends of write gaps92and93, and to increase pattern uniformity across width W′ of write gap structure44. Alternatively, end features76are formed with circular, rectangular or diamond-shaped geometry, or another suitable geometry for increasing the uniformity of the servo pattern. In addition, write gaps92and93may be reversed, in order to generate a complementary servo data pattern with reversed perpendicular and skew lines.

FIG. 6Bis a schematic view of write gap element42for magnetic head30, illustrating a second alternate configuration for write gap structure44. In this example, write gap structure44includes a first linear (transverse) write gap94and a second chevron-shaped write gap95with vertex V′ oriented along centerline L′ of write gap structure44, for example to generate pattern lines84and85for servo data pattern60ofFIG. 5B.

As shown inFIG. 6B, end features76have a diamond-shaped configuration and chevron-shaped write gap95follows transverse write gap94, with vertex (or cusp) V′ oriented against or oppositely with respect to the travel direction of the magnetic medium. Alternatively, chevron write gap95may be reversed, with vertex V′ oriented along the media travel direction, and complementary servo data patterns may be formed with either linear write gap94or chevron write gap95first, followed by chevron write gap95or linear write gap94.

FIG. 6Cis a schematic view of write gap element42for magnetic head30, illustrating a third alternate configuration for write gap structure44. In this example, write gap structure44includes first and second chevron-shaped write gaps96and97forming skew angle2α, with vertices V′ oriented along centerline L′ or write gap structure44. Alternatively, chevron write gaps96and97may be reversed to generate a complementary servo data pattern60, for example to form inward or outward-facing chevron pattern lines86and87, as shown in servo data pattern60ofFIG. 5C.

In each of the various examples, configuration and embodiments described here, the particular features of magnetic head30, write gap structure44and servo data pattern60are merely representative. In particular, different combinations of these features are contemplated, for example using gap structures44with any two, three or more write gaps73-75and92-97, in any order, in order to generate corresponding servo data patterns60with any combination of pattern lines63-65and82-87. Any of the various end features76may also be used, and write gaps73-75and92-97may also take on other forms, for example with curved or arcuate segments configured to generate pattern lines63-65or82-87with corresponding curvature.