Computer simulation of nonlinear bit shift in perpendicular recording

A computer simulation model has been applied to study inter-transition interaction in perpendicular recording. A "11011011" pattern was simulated for different head-medium spacings. In contrast to longitudinal recording, the effective inter-transition interaction between the center "11" bits is repulsive. The position displacement of the transition peak due to this effective interaction and the peak shift of the reproduce voltage are calculated. For contact recording, due to the large head field gradient, the displacement is small and the bit shift is almost the same as result of linear superposition. For out of contact recording, both the displacement and the nonlinear portion Of the bit shift are significant and the overall bit shift is approximately spacing-independent at the D50density.