Extraction of the response function of GMR head for spin-stand imaging

In this paper, an advanced extraction technique of the response function of giant-magnetoresistive (GMR) head for use in spin-stand imaging is presented. The essence of this technique is the spatial averaging of readback signals of many identically written "point-like" charges resulted from dc-trimmed transitions. As a result of the averaging, the noise generated by random fluctuations of medium properties is filtered out. This extraction technique also restores the symmetry of the head response function by employing a nonstandard dc-trimming procedure and a modified bias condition for the read process. By using the extracted head response function, we were able to reconstruct magnetization images of overwritten data with a misregistration of 50 nm.