Abstract: A magnetoresistive sensor (10) having permanent magnet stabilization includes a magnetoresistive layer (12), at least one permanent magnet (14a or 14b), and first and second current contacts (16a and 16b). The magnetoresistive layer (12) has an active sensing region (18) having a first thickness, and at least one under layer region (26a or 26b), with each under layer region (26a or 26b) having a second thickness that is less than the first thickness. Each permanent magnet (14a or 14b) is formed upon an under layer region (26a or 26b) of the magnetoresistive layer (12), and the first and second contacts (16a and 16b) are electrically coupled to the active region (18).

Abstract: An improved magnetoresistive head design including a front curved sense contact, a back curved sense contact and a lip extension forming an elliptical sensor region is disclosed. Current flows perpendicularly to the contact edges and intersects the MR element's magnetization vector at 45 degrees. A symmetrical read sensitivity function is the result of constant magnetic flux associated with an elliptical sense region.

Abstract: A wafer level test structure and method detects multiple magnetic domains and magnetic domain instability in a test magnetic element. The apparatus comprises a first MR sensor designed to be held in a single magnetic domain by shape anisotropy and a second MR sensor having a permanent magnet to hold the element in a single magnetic domain. A circuit connects the first and second MR sensors to detect differences between the changes in resistance between the first and second sensors in the presence of a magnetic field or differences in resistance after the application and release of a magnetic field. The circuit is preferably a balance circuit in which imbalance in the presence of a magnetic field indicates the presence of multiple magnetic domains in at least one of the test sensors.

Abstract: A magnetoresistive transducer design for cross-talk supression and increased Neel temperature is disclosed. The transducer is formed by fabricating on a suitable substrate an antiferromagnetic material layer above and below the permalloy layer. The additional antiferromagnetic layer between the substrate and the permalloy increases the exchange coupling biasing of the magnetoresistive transducer thereby providing increased cross-talk supression and greater longitudinal bias. The location of the additional antiferromagnetic layer beneath the permalloy also increases the Neel temperature of the transducer. A permanent magnetic material can also be substituted for the antiferromagnetic material with the result that the longitudinal bias is increased by coupling to the upper and lower surfaces of the permalloy layer thereby doubling the effect.

Abstract: A vertically recording write probe and read ring head. A ring pole is mounted adjacent a vertical recording probe pole. The ring pole tip is made thin such that it saturates on write and does not affect performance of the probe pole. The ring pole tip is separated from the probe tip by a small read gap. The probe pole and ring pole are connected in a back gap region so that the combination reads like a conventional read head.

Abstract: A magnetoresistive sensor element having bottleneck shaped ends. The sensor element has a highly stable, single domain central region, which eliminates Barkhausen noise.

Abstract: A magnetic read head has a first embodiment comprising an elongated magnetoresistive element having a central region and distant ends. The central region has equipotential strips disposed intermediate to its ends, and detection circuitry is electrically connected to these intermediate equipotential strips to sense the changing resistance of the central region in the presence of data magnetically recorded on a medium. In a second embodiment, the magnetoresistive element is folded into a picture frame shape and has its ends joined. The element is vertically arranged so that one of the legs of the element is positioned in proximity to a selected track of a recording medium. A pair of equipotential strips are disposed at opposite ends of the leg to define a sensing region therebetween. Detection circuitry is connected to these equipotential strips to detect the changing resistance of the sensing region in the presence of the magnetic fields of the medium.

Abstract: A magnetic read head has a first embodiment comprising an elongated magnetoresistive element having a central region and distant ends. The central region has equipotential strips disposed intermediate to its ends, and detection circuitry is electrically connected to these intermediate equipotential strips to sense the changing resistance of the central region in the presence of data magnetically recorded on a medium. In a second embodiment, the magnetoresistive element is folded into a picture frame shape and has its ends joined. The element is vertically arranged so that one of the legs of the element is positioned in proximity to a selected track of a recording medium. A pair of equipotential strips are disposed at opposite ends of the leg to define a sensing region therebetween. Detection circuitry is connected to these equipotential strips to detect the changing resistance of the sensing region in the presence of the magnetic fields of the medium.

Abstract: A field-access bubble memory chip has a plurality of permalloy elements overlying an insulating layer. The permalloy elements are configured and positioned to define a plurality of paths for propagating magnetic bubbles under the influence of a Z bias magnetic field and a rotating XY magnetic drive field. A first portion of the paths are located in control function areas of the chip and a second portion of the paths are located in a storage area of the chip. The period of the permalloy elements in the control function areas is substantially greater then the period of the permalloy elements in the storage area. The thickness of the insulating layer immediately beneath the permalloy elements is less in the storage area than in the control function areas. This difference in thickness is sufficient so that the propagation margins for magnetic bubbles in the control function areas and in the storage area are substantially equal.

Abstract: A bubble memory chip includes a plurality of data loops, some of which may be defective, for storing magnetic bubbles representative of data therein. A serial-parallel input propagation path and a parallel-serial output propagation path are provided for propagating bubbles to and from the data loops. A plurality of spaced apart permalloy disk elements are provided, each adapted for having a single bubble circulated thereabout in the presence of an in-plane rotating magnetic drive field. A stream of bubbles representative of an error map indicating which of the data loops are defective is loaded onto and read from the disk elements to initialize the memory. A plurality of gates permit the bubbles of the error map to be transferred between an error map propagation path and the disk elements in parallel fashion upon pulsing of an adjacent control conductor. The potential for data scrambling in the error map is eliminated.

Abstract: In a bubble memory, propagation elements are configured so that shorts between adjacent elements as a result of fabrication inaccuracies do not destroy their poles and create barriers to bubble propagation. In designing the bubble memory, the gaps can thus approach the resolution limit of the photolithography, resulting in a higher storage density and a reduced operating drive field. In one embodiment permalloy chevrons which overlie a garnet film have opposing side edges defining a gap therebetween which increases in width moving in a direction away from the poles.

Abstract: In a field-access magnetic bubble memory X and Y coils encircle the chip for providing the rotating XY magnetic drive field when conventional drive signals are applied thereto. At least one of the coils is non-uniformly wound to provide a first predetermined magnitude of the drive field in first predetermined chip areas and a second lesser predetermined magnitude of the drive field in a second chip area. In the embodiment disclosed the chip has a dual-block replicate architecture with gates and bubble detectors requiring a relatively high drive field located in peripheral edge areas at the bottom and top of the chip. A plurality of data storage loops requiring a relatively low drive field are located in the medial portion of the chip. The outer layer of the Y coil is non-uniformly wound to provide a gap in registration with the medial area of the chip.

Abstract: The invention is directed to continuous (gapless) propagation structures for use with magnetic bubble domain devices. The gapless structures are arranged so that magnetic bubbles will propagate therealong without a significant change in size or diameter of the bubble. In addition, the structures are configured so that the bubbles will propagate in a preferred direction without ambiguity.

Abstract: Disclosed is a magnetic bubble memory that includes a plurality of minor loops for storing bubbles representative of data therein, and a pair of minor loops for storing bubbles representative of an error map therein. The error map is selectively written into and read from only one loop of the pair. The other loop is redundant and improves chip yield. A serial-parallel bubble propagation path connects all of the loops to a bubble generator. This path includes a predetermined number of bubble propagation elements between the transfer-in gates for the pair of loops. Proper choice of the number of propagation elements enables the error map to be selectively written into/read from only one loop of the pair with only a single control line.

Abstract: There is provided a switch which is useful in magnetic bubble domain devices. The switch can be used to replicate, transfer or annihilate any bubble domains in a magnetic bubble domain system. The switch comprises a "BOOMERANG" shaped element which is disposed adjacent to two juxtaposed magnetic bubble domain propagation paths. A re-entrant current path conductor is integrally connected to the boomerang shaped element and associated with at least one of the propagation paths whereby magnetic bubble domains can be stretched, cut, annihilated or the like in response to a control current signal. Optional bar shaped elements are associated with various components of the switch in order to improve the operating characteristics of the switch.

Abstract: There is provided a switch which is useful in magnetic bubble domain devices. This switch can be used to replicate, transfer or annihilate bubble domains in a magnetic bubble domain memory system. The switch comprises a half-disk (or pick-axe) shaped element which is disposed adjacent to two juxtaposed magnetic bubble domain propagation paths.A re-entrant current path conductor is integrally connected to the half-disk element and associated with at least one of the propagation paths whereby magnetic bubble domains can be stretched, cut, annihilated or the like in response to a control current signal.Optional bar elements are associated with the half disk elements of the switch to improve the operating characteristics thereof.

Abstract: There is provided a memory system, for example, a magnetic bubble domain memory, which includes an exchange stack buffer memory between a main storage area and other portions of a bubble domain chip organization. The buffer memory includes a plurality of magnetic areas, such as discs, arranged in an ordered array between the main storage area and the remainder of the chip organization. Control conductors are arranged to interconnect each row of magnetic areas with an adjacent row of similar areas, or with portions of the main storage area, or with the remainder of the chip organization circuit. Means are provided to supply signals to the control conductors to selectively transfer information from a row of magnetic areas to one of the adjacent areas.

Abstract: There is described a bubble domain field access device component for providing continuous generation of a stream of bubble domains. The device is in the nature of a passive generator which is preferably constructed using one-level processing. The device uses multiple chevrons (chevron columns) which have the advantages of inherent redundancy, reduced gap tolerances and wide propagation margin. The structure comprises, generally, a rectangular seed plate arranged as a 90.degree., multiple-chevron, corner portion.

Abstract: There is disclosed an improved circuit element or structure for use in propagation of magnetic bubble domains. The improved circuit element permits a more desirable gap-to-period ratio than conventional element patterns. The improved circuit element provides portions thereof which are substantially parallel to similar portions of adjacent, similar circuit elements. As a consequence, the magnetic poles developed in the adjacent circuit elements by the application of the in-plane magnetic field are substantially identical at a given time thus facilitating interelement transfer.The circuit element structures are arranged in various propagation paths and operational components. Propagation paths and inter-propagation path elements are described.

Abstract: A plurality of stretcher detector segments are connected in series whereby detector signals generated when a bubble passes thereby are added together. Each of the stretcher detector segments is disposed an identical propagation distance away from passive replicators wherein bubbles are replicated from a propagation path and applied, simultaneously, to the stretcher detector segments. The stretcher detector segments are arranged to include both dummy and active portions thereof which are arranged to permit the geometry of both the dummy and active portions of the segment to be substantially matched.