Bias Point Shift in the TMR Sensor Under the Media Field

The read sensor bias point plays an important role in the presence of media field as the aspect ratio of the sensor is scaled down. The change in the bias point also affects the asymmetry of the read sensor. The bias point shift is studied experimentally in a spin stand by measuring the change in tunneling magnetoresistive (TMR) resistance in the presence of the media field. The change in the TMR resistance depends on the direction of the media field and the rotation of the free-layer magnetization with respect to the media field. The bias point shift and the associated change in asymmetry in the presence of the media field are calculated from the TMR resistance, and a test based on the bias point shift is proposed to screen the unstable read sensors.