Pattern Dependence of TMR Sensor Noise

Noise in tunneling magnetoresistive (TMR) read heads play an important role in magnetic recording. Extensive studies were carried out in understanding thermal magnetic noise in the TMR heads. The thermal noise is mostly attributed to the synthetic antiferromagnet in the TMR sensor. In this paper, we have studied the noise generated in the TMR sensor due to instabilities in the free layer using the magnetic field generated from the media dc-pattern of different polarities, and propose a test to study the read sensor instability caused by defects in the free layer. The influence of write noise from the written tracks created by the single-pole writer on the TMR sensor reader is also studied.