Abstract: In a lead overlay (LOL) type of read head first and second insulation layers are employed with the first insulation layer being located between a top surface of a first hard bias layer and a first lead layer and the second insulation layer is located between the top surface of a second hard bias layer and a second lead layer for minimizing a shunting of a sense current through the hard bias layers into a read sensor.

Abstract: A method for decoding Low Density Parity Check (LDPC) codes comprises executing a sum product algorithm to recover a set of information bits from an LDPC code represented as a bipartite graph of symbol nodes and check nodes, the sum product algorithm being responsive to input log likelihood ratios associated with the symbol nodes.

Abstract: A method and apparatus for efficiently executing a read request issued from a host computer when write requests are cached in a cache memory.

Abstract: A magnetic tunnel junction (MTJ) memory array having a magnetically stable free layer that can be switched from one memory state to another with a minimum of energy input. The memory array includes a MTJ cell having an antiparallel coupled free layer. An electrically conductive word line passes through the free layer such that current passed through the electrically conductive word line induces a magnetic field that acts on antiparallel coupled layers of the free layer causing their magnetizations to rotate while remaining antiparallel to one another.

Abstract: A new method of performing the write operation on the MRAM bit cell with improved switching selectivity and lower write current requirements is achieved utilizing oscillating word write currents at frequency near the ferromagnetic resonance frequency of the free layer, combined with the shift in said frequency due to the magnetic field produced by the current in the bit line. Operation is implemented in a conventional magnetic random access memory having a plurality of magnetoresisitive cells formed by an intersection of a grid of word and bit lines, wherein an individual cell within the grid can be selected and switched from one magnetic state to another by the magnetic fields produced by the currents in the word and bit lines.

Abstract: A method for managing storage reclamation on a tape management system is provided. The method allows the calculation of the optimum reclamation threshold value for a given system, thereby increasing the performance of the system drastically.

Abstract: An improved design for a high density thin film inductive write head assembly is provided. A pedestal and back flux closure of ferromagnetic material are formed on opposite ends of a planarized first pole piece. A plurality of coils of conductive material are deposited on top of the first pole piece between the pedestal and back flux closure. The coils comprise a plurality of loops or turns having voids between the coil loops. A photo resist material is deposited in the voids between the coils and the back flux closure, which is hard baked. A layer of alumina is deposited over the coils and hard baked photo resist material. The pedestal, back gap, coils, photo resist, and alumina are planarized by using a chemical mechanical polishing process. The thickness of the photo resist material relative to the coils is reduced using an O2 reactive ion etching process. A hard carbon or alumina filler is applied to fill the gaps between the coils and the photo resist.

Abstract: A hard disk drive actuator includes a plurality of arms for holding the heads over the disks. Each arm has one or more contaminant collectors for collecting contaminants, such as airborne particles, humidity, and/or organic gasses during operation. The contaminant collectors can take a variety of forms, including air porous filters mounted within existing cutouts within the plurality of arms. In this instance, the plurality of arms may be aerodynamically shaped to create a pressure differential between the top and bottom surfaces of the arms, causing an increased airflow through the filters. In another instance, the contaminant collector is a material applied to the top and bottom surfaces of the plurality of arms which attracts and/or captures airborne particles during normal operation.

Abstract: A magnetoresistance sensor structure is fabricated by providing a substrate structure, depositing a magnetic pinning structure on the substrate structure, and depositing an oxidized copper spacer layer overlying the magnetic pinning structure. The deposition of the oxidized copper spacer layer includes depositing a first copper sublayer, oxidizing the first copper sublayer, depositing a second copper sublayer, and oxidizing the second copper sublayer. More deposition and oxidation steps may be used as necessary. A sensing structure is deposited overlying the oxidized copper spacer layer.

Abstract: A ferromagnetic pinned layer (1) kept at a fixed magnetic orientation by a pinning layer (4) is separated from a ferromagnetic free layer (3) by a Mott insulator coupling layer (2). A controllable voltage source (5) is connected between the pinned layer (1) and the free layer (3). A sublayer of the coupling layer (2) whose width (d) increases with the voltage is converted to an electrically conducting and magnetically coupling metallic state. The magnetic exchange field acting on the free layer (3) which is controlled by the applied voltage via the width (d) of the electrically conducting sublayer of the coupling layer (2) can be used to switch the free layer (3) between states of parallel and antiparallel orientations with respect to the magnetic orientation of the pinned layer (1). This is used in memory cells and in a write head.

Abstract: A secondary servo actuator system for use in disk drives comprising a controller and two PZT transducers mounted on each suspension load beam in an arm assembly. When a seek operation is initiated the acceleration of the arms generates vibration modes. The PZT transducers on a suspension adjacent to the target head/suspension sense the vibration motion and provide output signals to the controller. The controller filters the signal and generates a control signal for the PZTs mounted on the target arm/suspension. The deformation of the PZTs in turn rotates the arm load beam and thereby adjusts the position of the target head to compensate for arm motion caused by the vibration modes. The secondary actuator system can be used during the deceleration trajectory of a target head to suppress lower order arm sway frequencies.

Abstract: Method and apparatus to correct an error of read-out data from a data storage medium, particularly a bit shift error, is described. The correction apparatus includes a gray bit detection circuit which flags bits with a phase shift exceeding a threshold and determines whether the previous or next bit cell has a smaller phase error. An RLL error detection circuit and a table containing valid bit combinations may be used in combination with the gray bit detector to correct errors on-the-fly without degrading performance. An advantage of the invention is that it allows correction of errors without regard to conventional ECC and its maximum number of errors.

Abstract: A sensor for measuring magnetostriction of and/or magnetic thin film is constructed by depositing a thin film nonferromagnetic electrically insulating layer followed by a thin film layer of a sensor material which is piezoresistive and nonferromagnetic. The insulating and the piezoresistive film can be etched into an appropriate pattern and orientation to provide sensitivity to strain in the magnetic film. The magnetostrictive strain in the magnetic film is induced by a known magnetic field which produces a corresponding strain in the piezoresistive film which can be measured as a change in the electrical resistance which can be detected by external probes or other measuring means. The measurement of the magnetostriction can be performed as a part of the manufacturing process for wafers with a plurality of thin film magnetic heads thereon and does not require that the wafers be removed to a laboratory.

Abstract: A high throughput method for producing the narrow track width inductive head is also provided, whereby the heads may be manufactured in substantial volumes. The new head may be merged or piggy-backed MR or GMR heads, comprising a first pole piece, P1, and a second pole piece, P2, and is distinctly characterized by write track width is significantly reduced by a preliminary ion milling process before P1 notching is performed. The preliminary step utilizes an ion milling process to trim the write track width, P2B, at an angle between 45 to 85 degrees from the wafer normal. The MR head may then undergo conventional P1 notching.

Abstract: Method and apparatus are described for recovery from temporary errors in a disk drive resulting from excessive temperature or the like. After a first error recovery procedure has been executed and failed, a waiting time is selected after which a second error recovery procedure will be performed. The length of the waiting time can be determined by the measured temperature if a sensor is included in the drive. If the error still cannot be recovered after the waiting period, the location where the error had occurred is temporarily registered as defective. Subsequently the drive will retest the failing location and remove the temporary defect registration if the error has been removed by, for example, the temperature having gone down.

Abstract: A method, devices, and an article of manufacture for reducing magnetic instability in a magnetoresistive read head of a combined read-write head after writing data onto a magnetic storage medium. The last write pulse polarity that results in the least amount of magnetic instability in the read head is determined, and is referred to as the designated polarity. Then, after a set of write pulses is written, it is determined whether the last write pulse has the designated polarity. If the last write pulse does not have the designated polarity, then an additional write pulse with the designated polarity is written. Thus, the last write pulse before a read always has the designated polarity, thereby reducing the magnetic instability of the read head, and consequently improving read head performance.

Abstract: A disk drive with the capability to prevent off-track writing with reduced false triggering is described. An improved method of predicting the position of a head is used to determine whether the head is on or off-track. A position error signal at an nth servo position Pn and a velocity Vn at the nth servo position (Vn=Pn−Pn−1) are calculated using values read at the nth and n−1 head positions. Based on these Pn and Vn and on the output of the servo controller at the nth servo position Un, the predicted PESn+1 is calculated as: Predicted PESn+1=Pn+Vn+kUn where k is a constant.

Abstract: A method and apparatus for recovering from operation errors arising in an information recording and reproducing unit using a head with a GMR sensor is described. The read and write operations of the unit comprise executing a first error recovery procedure for recovering the operation error, executing a first GMR evaluation procedure for evaluating the performance of the GMR sensor when the operation error cannot be recovered by the first error recovery procedure, and applying a resetting pulse to the GMR sensor in accordance with the first GMR evaluation procedure.

Abstract: A drive unit which recovers from write instability by heating the magnetic head prior to performing a dummy write operation is described. In the preferred embodiments, once write instability has been detected the head may be heated by friction with the rotating disk or by an external heater. In the friction method the head is moved to a safe area of the disk such as a textured landing zone while the disk rotation is continued. In drives using unload ramps, a heater is preferably placed at the the ramp so that the head can be heated while parked on the ramp. In each of these embodiments dummy write operations are performed while the head is in a thermally excited state due to the heating. The combination of heating and the dummy write operation aids in restoring write stability.

Abstract: An apparatus and method for decoding data encoded in a linear cyclic code with less hardware than the prior art decoding apparatus without sacrificing the processing speed are described. The polynomial arithmetic part 14 derives polynomials &sgr;(x), &ohgr;(x) by repeating calculation of the following Qi(x), exchange of polynomials between the register U_reg 180 and the register X_reg 184, and exchange of polynomials between the register Y_reg 182 and the register Z_reg 186 until the degree (deg Xreg) of the polynomial in the register X_reg 184 becomes smaller than [(d−h+1)/2] to solve the following recursive formula.