Effect of head field rise time in perpendicular recording

An analytic recording model for the transition parameter and the nonlinear transition shift (NLTS) with the rise-time effect has been developed. In this model, the Schwartz-Christoffel transformation is used to calculate the combined image field from the single-pole writer and the soft underlayer. It is shown that both medium velocity and finite head-field rise-time increase the transition parameter. The NLTS for a dibit pattern increases with linear density, but decreases with medium velocity. A large transition parameter arises because a finite rise time reduces the record field-gradient as the bit time is reduced. For a dibit, the demagnetizing field from the first bit increases the transition interval of the dibit, while the write-time difference of the second bit and the reference bit decreases the interval.