Theory of nonlinearities and pulse asymmetry in high density tape recording

The mechanisms of pulse asymmetry and nonlinearities in dibit recording have been analyzed by numerical simulation. Well-oriented longitudinal tape media were modeled by 2D discretization and subsequent iteration including distributions in particle orientations and intrinsic switching fields. Typical head-medium spacing was included as well as imaging of the demagnetization fields by the record head. Isolated transitions and dibits were recorded utilizing head fields typical of high-density recording. Characteristic isolated pulse asymmetry is shown to be due predominantly to the demagnetization fields during the write process which substantially shifts the phase of magnetization transitions with depth into the medium. In dibit recording with optimum or greater record currents, the second transition is shown to yield a larger playback voltage than that predicted by linear superposition