Narrow-track differential head: performance on longitudinal and perpendicular disk media

This paper describes experimental spin-stand tests of a narrow-track differential head, reading back square-wave patterns on longitudinal and perpendicular recording media. The low linear density response of the transducer to recording signals of longitudinal and perpendicular media consisted of bipolar and unipolar pulses, respectively. The paper also presents the head responses to dibits and magnetic patterns recorded in longitudinal media. The head attained the highest linear resolution with a longitudinal thin-film medium, having an areal magnetic moment of M_rδ=0.5 memu/cm² and a coercivity of H_c=3.0 kOe. The nominal full dynamic range of the transducer was tested with a longitudinal medium having M _rδ=1 memu/cm², but at the expense of a lower linear resolution. The transducer showed a considerably lower linear resolution, when reading back magnetic patterns of a dual-layer perpendicular medium. The experimental time-domain and spectral responses of the dual magnetoresistive head agreed well with those predicted by theory