Hewlett-packard Company

Hardayal S Gill

Victor W Hesterman

Thomas C Anthony

Lung T Tran

Manoj K Bhattacharyya

Steven Louis Naberhuis

James A Brug

Ralph F Simmons, Jr

Robert J Davidson

Giora J Tarnopolsky

Robert A Garcia

A head structure for reading and writing perpendicular transitions from and to a moving recording medium. The head structure comprises an auxiliary magnetic pole having a tapered edge adjacent its air bearing surface that is oriented transverse to the direction of motion of a recording medium. A magnetoresistive gradiometer employed as the read mechanism is formed within a layer of insulating material disposed on the auxiliary pole member. The gradiometer comprises two magnetoresistive members separated by dielectric material, and two shield members disposed on opposite sides of the magnetoresistive members. The shield members shield the magnetoresistive members from undesired magnetic fields and thus improve the resolution of the signals read from the medium. A coil is formed on and encapsulated within a layer of photoresist material deposited above the layer of insulating material. A primary magnetic pole is disposed on the layer of photoresist material and has a portion thereof which tapers toward the air bearing surface. The primary and auxiliary magnetic poles are adapted to write to the recording medium. A portion of the primary magnetic pole is spaced away from the auxiliary pole member at a location substantially opposite the location of the gradiometer, in order to minimize data erasure in the recording medium by increasing the reluctance of the head strcuture. This gap minimizes data erasure in the recording medium due to stray magnetic fields by enhancing the reluctance of the head structure. A layer of nonmagnetic insulating material is disposed on the primary magnetic pole to encapsulate it and complete the head structure. The geometry of the head structure minimizes its sensitivity to externally applied fields. The magnetoresistive gradiometer is positioned in the gap of the write head so that it experiences minimum fields caused by write coil excitation. Furthermore, the geometry of the gradiometer head shields results in better linear resolution than conventional head designs without shields.

Single pole write and a differential magneto-resistive read for

A a dual element magnetoresistive sensor that uses the longitudinal field produced by the sense/bias currents to initialize the elements into a stable antiparallel state. The dual element magnetoresistive sensor comprises two magnetoresistive elements having first and second conductors coupled thereto. The first and second conductors are oriented in the same direction as the magnetoresistive elements in their contact areas. A third conductor is disposed between and coupled to the two magnetoresistive elements at their opposite ends. The third conductor is oriented transverse to the directions of the first and second sensor elements, and is adapted to conduct current therethrough in a direction transverse to the currents conducted by the first and second conductors. Currents conducted by all three conductors self-initialize the magnetoresistive elements into a single domain state. Also, the current flowing in the third conductor creates an anti-parallel longitudinal field in the two sensor elements that is oriented in the same direction as closure fields present in the magnetoresistive elements. These fields ensure that a single domain state is produced in the magnetoresistive elements. An alternative design for the third conductor employs one conductor portion that provides a current distribution that initializes the sensor. This current distribution initializes the sensor. Another conductor portion is used during reading and provides a current distribution that is similar to the distribution produced by the first and second conductors. This ensures that the across-the-track response is symmetric. A small fraction of the sense current flows in the initializing conductor portion to provide stabilization during reading.

Self-initialization of short magnetoresistive sensors into a single

A magnetoresistive head structure that incorporates a thin film magnetoresistive transducer that is suitable for use in perpendicular and longitudinal recording heads. This structure includes first and second dielectrically separated magnetoresistive members that have noncontacting first ends. Sense conductors are disposed in contact with the first ends of the magnetoresistive members and are adapted to provide sense currents thereto. A bias current conductor arrangement is disposed adjacent to the magnetoresistive members and is separated therefrom by dielectric and is adapted to provide bias current thereto. A common conductor is disposed in contact with the second ends of the magnetoresistive members and is adapted to short the second ends thereof and provide a return path for the sense and bias currents. In one embodiment, the bias conductor arrangement passes between the magnetoresistive members and thus provides for longitudinal transition detection. In another embodiment, the bias conductor arrangement passes adjacent one side of the first magnetoresistive member and returns on the other side of the two magnetoresistive elements and thus provides for perpendicular transition detection. Additionally, a plurality of nonmagnetic shield members may be provided adjacent the magnetoresistive members to magnetically shield them from extraneous magnetic fields and improve resolution. Differential amplification means may also be provided for processing voltages sensed across the magnetoresistive members.

Magnetoresistive head structures for longitudinal and perpendicular

A thin film recording head which utilizes polyimide as the coil encapsulant. The polyimide encapsulant is self planarizing and lends itself to processing of the coil vias, magnetic shunt vias and apex tapers. Methods of fabricating a thin film recording head and forming coil vias, magnetic shunt vias and apex tapers are also disclosed. In general, an insulating material is deposited on a bottom magnetic yoke. A first layer of polyimide is then deposited of the insulating material. Then, a three layer photoresist structure is deposited on the first layer of polyimide, which includes a transfer layer deposited between two layers of photoresist. The top layer of photoresist is developed and the transfer layer is etched. The first layer of photoresist is then etched into the polyimide layer to form troughs therein. The coil material is then deposited into the etched troughs. The coil material comprises a layer of metal having a relatively thin passivation layer deposited thereover. The photoresist and transfer layers and unwanted coil material are then removed by ultrasonic agitation in acetone. A second layer of polyimide is then deposited over the formed coil structure to encapsulate and planarize it. The method which forms the coil vias, magnetic shunt vias and apex tapers of the recording head after formation of the encapsulated coil comprises the following steps. First, a photoresist layer is deposited on top of the second layer of polyimide. The photoresist layer is then patterned to define coil vias, magnetic shunt vias and apex taper locations. Then, this structure is heated to a temperature less than 120 degrees Celsius to round the corners of the photoresist layer at the coil via, magnetic shunt via and apex angle locations. Finally, the patterned photoresist layer and underlying polyimide layer are etched to provide the coil vias, magnetic shunt vias and apex tapers. Thereafter, the top magnetic yoke is deposited over the encapsulated structure to complete the thin film magnetic recording head.

Method of making a thin film recording head apparatus utilizing

A read/write head for a hard disk provides both a magneto-resistive read function and an inductive write function in a common gap. The inductive write function is provided by a current carrying coil which is magnetically coupled to top and bottom shields or pole tips which in turn induce the magnetic fields required for writing on the disk. Mutually biasing magneto-resistive read sensor are located between the shields, which serve to improve the resolution of the read function. During a read operation, read/write circuitry maintains a current in the coil which cancels, at least partially, magnetic fields induced by sensing and bias currents in the magneto-resistive heads which might other perturb information stored in the medium. This arrangement provides a read/write head with improved read/write resolution as required by emerging high density storage media in compact formats.

Compensated magneto-resistive read head

A sensor for reading perpendicularly recorded media includes dual magneto-resistive elements. Directionally opposed currents through respective elements each serve both sensing and bias functions. A detector differentially detects changes in the resistance of the stripes so as to presume common mode noise rejection when reading perpendicular recording media. In addition, the opposing currents offset each other's interaction with the soft magnetic underlayer of the media, which interaction could otherwise perturb the information stored on the media. Provision is made for switching the relative direction of current flow to provide for reading longitudinally recorded media.

Magneto-resistive sensor with opposing currents for reading

An improved shield for field sensing transducers used in magnetic storage devices is presented. The inventive shield provides a planar surface for the transducer to rest on, a single magnetic domain in the vicinity of the transducer, low magnetic reluctance for fields from the recording media, and stability against external magnetic fields, that is, high reluctance for external magnetic fields.

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Los Altos, CA, United States of America

Hardayal S Gill