Write Current Rise Time in Perpendicular Recording: An Experimental Study

Write current rise time effects in perpendicular recording are studied using a write driver with a variable rise time. The basic recording requirement that the write current steady state should be reached before the next transition can be written is verified experimentally. It is demonstrated that, as long as this requirement is met, the transition recording is surprisingly insensitive to the write current rise time. The experimental dependencies of magnetization switching time on write current rise time, amplitude, and shape are explained by the dynamics of write bubble expansion during recording process. The effects of media velocity and write current overshoot on switching time are also studied. Our results indicate that the intrinsic media switching time currently does not limit the recording process and is probably below 100 ps. The intrinsic head reversal time is the main factor limiting the achievable data rate. For a set of "healthy" recording components (well-saturated media, sufficient head field, high head field gradient), the recording process is virtually insensitive to the write current rise time as long as the write field waveform reaches its steady state before the next transition