Baseline popping noise of giant magnetoresistive head

Baseline popping noise (BLPN) is characterized by the spurious popping of b aseline between readback pulses from magnetoresistive/giant MR (MR/GMR) hea ds. This article focuses on experimental investigation of BLPN from hard-ma gnet-biased GMR head. It is found that BLPN is sensitive to read bias curre nt in both magnitude and polarity. Also, we found that BLPN is very sensiti ve to head offset across a written track as a result of interaction between localized BLPN active slice and written track edge. Full-track and microtr ack profiling of BLPN is used to substantiate these behaviors. A close-fit model is proposed to further explain the BLPN mechanism. With this model, G MR BLPN is explained by longitudinal hard bias insufficiency on a free laye r. When hard bias is not strong enough, due to the demagnetization field, m agnetization around edge area rotates either up or down. This skewed magnet ization is not stable, a small field will make it flip up and down, which r esults in jumps in transfer curve and eventually instability in track avera ge amplitude. (C) 2000 American Institute of Physics. [S0021-8979(00)72708- 3].