Abstract: A spin valve magnetoresistive (MR) read sensor is provided wherein the free and pinned layer magnetization are perpendicular to each other under quiescent conditions and the current flowing in the free MR layer is oriented to flow at a substantially 45 degree angle with respect to the free layer magnetization. The flow of the current at the 45 degree angle with respect to the free layer magnetization causes the AMR effect which is present in the free MR layer to be added to the spin valve sensor GMR effect and increases the overall magnetoresistive effect by about 25% to 33%.

Abstract: A disk drive system having a magnetoresistive (MR) sensor having four leads, two leads for providing sense current to an MR layer and two leads for providing current to a soft adjacent layer (SAL). The MR layer as well as the hard bias layers are electrically insulated from the SAL by an insulator. The voltages developed across the MR layer (voltages due to the presence of thermal asperities and voltages due to the presence of data fields) and the SAL (voltages due to the presence of thermal asperities) are applied to the inputs of a differential amplifier for substantial elimination of the thermal asperity signal.

Abstract: A magnetoresistive (MR) sensor having end regions separated from each other by a central region. Hard bias layers disposed in the end regions longitudinally bias an MR layer which is formed in the central region. A soft adjacent layer (SAL) is utilized to transversely bias the MR layer. The MR layer and the hard bias layers are electrically insulated from the SAL by an insulator. The SAL magnetization is fixed through exchange coupling with an antiferromagnetic layer. Separating the MR layer and the hard bias layers from the SAL by an insulator prevents the sense current from flowing in the SAL thus improving the MR effect.

Abstract: A magnetoresistive (MR) sensor comprises a dual differential spin valve structure. Each of the spin valves comprise first (free) and second (pinned) layers of ferromagnetic material separated by a thin film layer of nonmagnetic material. The magnetization direction of the pinned layers of ferromagnetic material in each spin valve is fixed, and their magnetization is set antiparallel to each other. A current flow is produced through the MR sensor, and the variations in voltage across the MR sensor are sensed due to changes in resistance of the MR sensor produced by rotation of the magnetization in the free layers of ferromagnetic material as a function of the magnetic field being sensed.

Abstract: A dual element magnetoresistive (MR) sensor is disclosed comprising two MR elements separated by a high resistivity conductive spacer material. A layer of hard bias material, which abuts one of the MR elements at each of its track edges, has a magnetization times thickness value substantially matched to that of the one MR element to bias it in one longitudinal direction. An exchange bias layer biases the other MR element by exchange coupling in an opposite longitudinal direction to achieve magnetic stabilization between the MR elements. The exchange bias layer abuts the other MR element at each of its track edges and has a magnetization times thickness value substantially matched to that of the other MR element. Alternatively, the exchange bias layer extends from one track edge to an opposite track edge in continuous underlying or overlying contact with the other MR element.

Abstract: A magnetoresistive (MR) sensor comprising a layer of ferromagnetic material forming an MR sensing element wherein the MR sensor is biased by utilizing only the MR stripe uniaxial anisotropy and the shape anisotropy of the active region of the sensing element. The active region of the MR element has a generally square geometry to provide the desired shape anisotropy. The MR sensor is biased at approximately 45 degrees by defining the magnetization at the four edges of the sense element active region utilizing its shape anisotropy and canting the magnetic easy axis at an appropriate angle during fabrication of the MR sensor. To minimize Barkhausen noise, a single magnetic domain configuration is achieved by reducing the sensor active region dimensions, i.e., stripe height and track width, to less than the characteristic domain wall thickness such that the formation of multiple magnetic domains is no longer energetically favorable.

Abstract: A method and means are disclosed in a Log Structure Array (LSA) storage subsystem for managing said subsystem without a need for an access to a complete LSA directory in a RAM. This object is achieved by maintaining (1) a subset of the LSA directory (referred to as LSA sub-directory) in a RAM where the LSA sub-directory comprises the logical track address of a predetermined number of most recently accessed logical tracks; (2) a journal of changes to the LSA directory which is maintained on a different power boundary than the LSA directory power boundary; and, (3) an array of bit maps, one bit map per segment which is used for fast garbage collection thus eliminating the need for having an access to a complete LSA directory in a RAM during garbage collection.

Abstract: According to the present grinding method, a plurality of optical markers are formed by photolithography such that the markers are embedded in a chiplet having a magnetic head. Markers are preferably in the shape of a bar having predetermined height, width and length and are spaced from each other by a predetermined distance where one end of the bars are sequentially offset from each other by a predetermined amount. During coarse grinding of the magnetic head as the magnetic head surface material is ground away, the end-face of the bars, one at a time, become visible. The closer the grinding surface approaches the desired inductive throat or MR element height, more end-faces become visible. Coarse grinding continues until a predetermined number of end-faces become visible at which point the grinding process is terminated and the magnetic head is ready for the final lapping process.

Abstract: An apparatus and method for detecting and locating up to two symbols in error or erasures in an n.times.m A(n,m,t) parity coded bit array previously recorded on a multi-track storage device where n is a prime number, m.ltoreq.n, wherein at least one non-zero syndrome of m rotated and column summed syndromes is derived. The method includes an iterative process using an incremented tracking variable and testing of the cyclic equivalence of three derived vectors to isolate the number and location of the array column or columns containing the error or errors. Each derived vector is the modulo 2 sum of a selected syndrome and a selected rotated vector. Cyclic equivalence of between a derived vector and a selected rotated one of the other derived vectors for any given iteration establishes the error or errors and their column location or locations. An extension is shown for detecting and locating up to three errors or erasures.

Abstract: To provide inline expansion universally applicable to a variety of formulas as combinations of array functions and array operations with a programming language such as APL or FORTRAN 90 having array functions, without the need to prepare individual templates or macros. In the method of the present invention, a transformational intrinsic function (TIF) formula is analyzed during compilation and a template for inline expansion is generated. The template for inline expansion is mapped to an actual array, and macro-processing is used in generating the template. According to this method, an arbitrary combination of TIFs can be inline-expanded by simply preparing one macro-template for each TIF.

Abstract: In a magnetic read/write assembly, a removable fusible-link shorts the magnetoresistive (MR) sensor element to minimize electrical current through the MR sensing element during discharge of static electricity. Other magnetic head assembly elements such as the write coil and MR magnetic shields are also shorted using fusible-links. The fusible-link is removable during the assembly process. The existing terminal pads and wires are used to remove the fusible-link.

Abstract: A magnetic storage system in which a magnetoresistive (MR) transducer utilizes a high coercivity magnetic material to produce a bias field for achieving higher signal output with low currents for narrow track width applications. Strips of high coercivity magnetic material contiguously contact opposite track-overlying edges of an MR layer. Each strip has a horizontal component of magnetization times its thickness that is at least equal to a horizontal component of magnetization of the MR layer times its thickness before the MR layer is biased by the strips, and each strip has its magnetization direction canted at an angle .phi. from its horizontal component. The MR layer is asymmetrically positioned between spaced magnetic shields and the MR layer is separated by a conductive nonmagnetic spacer layer from a shunt layer.

Abstract: In a client/server environment having a backup subsystem, a method and means for reducing the storage requirement in said backup subsystem and further reducing the load on the transmission bandwidth between the clients and the backup subsystem. This is accomplished by maintaining a copy of frequently accessed files on both the server and clients when a file is modified on the client, a delta file which is the difference between the base file and the modified version of the base file is created and transmitted to the server to be stored on a storage medium which is part of the backup subsystem. Alternatively, whenever a client modifies a file, the base version of that file is transmitted to the client from the server, a delta file is created and transmitted to the server to be stored on the storage device which is part of the backup subsystem. Alternatively, modified files are transmitted to the backup server and the differencing is carried out at the backup server.

Abstract: A thin film diode and method of fabrication having large current capability and low-turn on voltage is provided as a switching or protective device against electrostatic discharge in integrated devices such as magnetoresistive sensors and the like. A first semiconductor thin film layer of NiO.sub.x having p type properties is disposed on an arbitrary substrate, such as alumina, glass, silicon dioxide, silicon and the like. A second semiconducting layer of tin oxide or indium oxide or other transparent oxide is joined to the first layer to form a p/n junction. In one method of fabrication, the p/n junction is formed in a sputtering process under a partial oxygen pressure to control the stoichiometry of the films. Gold and Gold Indium contacts are attached to the films to provide electrical contacts. The device is enclosed in a protective coating and connected in parallel with an electronic device subject to electrostatic discharge.

Abstract: A method and means for dynamically managing access by data sets to an LRU disciplined DASD cache staging data sets. A threshold utilizes the inverse of slowly varying global hit ratios (ST) taken over a large number of data sets to control the access by individual data sets in cache as measured by their local hit ratios (DSHR). After an initial trial period, a data set is allowed access to the cache only where DSHR>ST. The method and means are self adjusting in that as I/O demand changes, ST also changes in phase such that an increase in aggregate demand for cache results in elimination of data sets whose DSHRs were marginally equal to the old ST and now less than the new ST. Utilization of a DASD Fast Write and non-volatile store (NVS) can be managed similarly if coordinated with the cache and maintenance of both a global WRITE threshold (WR), local data set write hit ratio (DSHRW), and invocation of Fast Write only where DSHRW>WT (write threshold).

Abstract: In a multinode communication or multiprocessor network, messages are communicated from one node to another using an adaptive and dynamic routing scheme. The routing scheme includes two-level multi-path routing tables at each node to ensure efficient delivery of the messages. An entry in the level-1 table identifies a group of nodes and entry in the level-2 table identifies the address for each node within that group. The routing scheme also includes a deflection counter in each message header to avoid endless rerouting of messages and an exponential backoff and retry policy to avoid deadlocks.

Abstract: A thin film magnetic head in which the width of the first and second magnetic yoke layers between the zero throat point and the yoke flare point is progressively widened to equalize the flux density over this length so that the whole length reaches saturation simultaneously at a single current. Consequently, the field at the gap at the air bearing surface increases insignificantly once saturation of this length occurs, and the write field is then constant for currents above the saturation value.

Abstract: This high-density optical data storage unit comprises a storage medium supported on a mechanically stable substrate, and a read/write arrangement employing a plurality of laser light sources and an interrogation light source. The laser light sources are designed as laser diodes attached to a substrate and optically aligned with an equal plurality of microlenses integrated in a first transparent layer. The read/write arrangement further comprises at least one second transparent layer, and an optional semitransparent conductive coating, said layer or said coating carrying a plurality of particulate protrusions which are also aligned with said diodes and said microlenses, said storage medium and said read/write arrangement being maintained in a mutually parallel alignment with a gap in between having a width of less than 100 nm. The protrusions in combination with the laser light sources produce dints in the medium which are representative of the data to be stored.

Abstract: In a magnetoresistive read transducer, a material which is inert with respect to the soft film magnetic biasing layer is formed at the surface of the substrate prior to soft film deposition. In a preferred embodiment of the present invention, a substrate surface layer of metal such as Cr or Ta is used. These metals have high resistivity due to partial oxidation when deposited on the substrate to reduce shunting of sensing current through the magnetoresistive layer, and further acts as a barrier to protect the soft film from substrate interface contamination. The surface layer also acts as a seed layer to set the soft film magnetization orientation in a well-defined direction therefore reducing magnetic instability.

Abstract: A no-ID zone-bit-recording sectored servo data recording disk drive system is described wherein track seek time is substantially reduced by storing only partial cylinder address on each servo sector of each track. According to the system and method described herein, a cylinder address is divided into high order bits, middle order bits, and low order bits. The low order bits is stored on each servo sector of each track. The high order bits is stored only on even number servo sectors and middle order bits is stored only on odd number servo sectors. During the seek operation, as the head passes over the tracks toward the desired track, the partial cylinder address stored on odd and even numbered servo sectors on each track is retrieved and stitched together to form a complete cylinder address. The completed cylinder address is then compared with the desired cylinder address to determine whether desired cylinder is reached or not.