Longitudinal bias structure having stability with minimal effect on output

摘要

It is necessary to stabilize the free layer of GMR or TMR devices by providing a longitudinal bias field. As read tracks become very narrow, this field can drastically reduce the strength of the output signal. This problem has been overcome by adding an additional, compensatory, bias layer. This layer is permanently magnetized in the same direction as the main bias magnet. Through control of the magnetization strength and location of the compensatory bias layer, cancellation of the field induced in the free layer, by the main bias layers, is achieved. A process for manufacturing the devices is also described.