Headway Technologies, Incorporated

Western Digital Technologies, Inc.

Yaw Shing Tang

Hung Liang Hu

Lijie Guan

Kochan Ju

John Thomas Contreras

Joey Martin Poss

Ian Robson McFadyen

Cliff C Zhang

Sergey G Muchiyev

Liji Guan

A data storage device is disclosed comprising a storage medium and a head configured to access the storage medium, wherein the head comprises a first write assist element (WA1) comprising a first terminal and a second terminal and a second write assist element (WA2) comprising a first terminal and a second terminal. The second terminal of the WA1 and the second terminal of the WA2 are coupled together to form a common node. A first bias signal is applied to the first terminal of the WA1, a second bias signal is applied to the first terminal of the WA2, and a common mode voltage is applied to the common node.

Disk drive biasing two write assist elements using three terminal control circuitry

Measurement circuitry is disclosed that is configured to be coupled to a load through a transmission line. A first AC signal having a frequency &#x3c9;is applied to the transmission line and a first input impedance of the transmission line is measured. A second AC signal having a frequency &#x3c9;is applied to the transmission line and a second input impedance of the transmission line is measured, wherein the frequency &#x3c9;is different than the frequency &#x3c9;. A third AC signal having a frequency &#x3c9; is applied to the transmission line and a third input impedance of the transmission line is measured, wherein the frequency &#x3c9; is different than the frequency &#x3c9;and different than the frequency &#x3c9;. A resistance of the load is measured based on the measured first input impedance, the measured second input impedance, and the measured third input impedance.

Measuring a load resistance coupled to a transmission line

Prior art designs of single pole writers have been limited by premature saturation at the tip. This limits the head field that can be achieved without simultaneously widening the write profile. This problem has bee solved by means of a vertical main pole whose thickness has its conventional value a short distance from the tip but that tapers down to a significantly reduced value as it approaches the tip. A process for manufacturing this tapered tip design is also presented.

Process to manufacture a magnetic write head

The traditional single pole perpendicular writer has two major problems&#x2014;insufficient field gradient in the down track direction and adjacent track erasure (ATE) caused by side fringing fields. These problems have been overcome by tapering the main pole and then shielding it on all four sides.

Four sided shield structure for a perpendicular write head

Prior art designs of single pole writers have been limited by premature saturation at the tip. This limits the head field that can be achieved without simultaneously widening the write profile. This problem has been solved by means of a vertical main pole whose thickness has its conventional value a short distance from the tip but that tapers down to a significantly reduced value as it approaches the tip. A process for manufacturing this tapered tip design is also presented.

Perpendicular write head with tapered main pole

A process for reducing fringe field effects of a main write pole by shielding it on all four sides, with the regular return pole also serving as the leading edge shield, is described. The main pole may also be tapered and the leading edge and side shields may be magnetically connected to each other.

Process of manufacturing a four-sided shield structure for a perpendicular write head

In a single vertical pole magnetic writer, flux passing through the return pole can sometimes be strong enough to erase previously recorded data. This problem has been overcome by the addition of a second return pole that is magnetically connected to the conventional return pole for the purpose of collecting leaked flux, thereby preventing it from reaching the underlayer.

Return pole field reduction for perpendicular write head

Conventional perpendicular writers that utilize an extended return pole are subject to large undershoot fields. This problem has been reduced by replacing the prior art extended return pole by one whose magnetic potential has been increased relative to both the main and return poles. In a first embodiment, a second non-magnetic gap is inserted between the extended return pole and the return pole. In a second embodiment, the extended return pole is made very thin, thereby increasing its reluctance, while a third embodiment combines both reluctance-increasing features in a single design.

Perpendicular magnetic writer with magnetic potential control shield

Conventional perpendicular writers that utilize an extended return pole are subject to large flux leakage. This problem has been reduced in the prior art by adding a downstream shield. This still leaves significant upstream leakage. This has now been eliminated by adding an upstream shield and then connecting the up and downstream shields by using side shields. The latter need not extend all the way from the downstream to the upstream shield in which case their thickness is increased relative to the full side shields.

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Saratoga, CA, United States of America

Yaw Shing Tang