Bias study on seed-layered DSMR head

Abstract

Bias profile of a DSMR head with conductive seed layers is studied by utilizing a transmission-line model. A closed-form analytical formula has been obtained as a function of head geometry and current shunting. It is found that if the two magnetic sensing elements are still symmetrically located between shields as before, the first MR element bias angle would be reduced while the second MR element bias angle would be increased by the same amount which is proportional to the shunting current if no saturation occurs at middle of bias profile. Studies also suggest that keeping the same total read gap length the bias angle difference is smaller when the two MR elements are designed to be closer to each other. Shifting both the two MR elements toward the top shield with a certain small distance is found to be more effective to compensate bias angle difference through introducing asymmetric image current fields.