Studies of nonlinear bit shift and partial erasure using pseudo-random sequence

A pseudo-random sequence method to identify nonlinear effects has been utilized at high recording densities. This method is extended to distinguish two different nonlinear effects: nonlinear bit shift and partial erasure. Following the nonlinear bit shift echo derivation in the pseudo-random sequence method, it is shown that partial erasure also produces an echo that is only 1/2 bit cell apart from the echo for nonlinear bit-shift. A numerical simulation of writing 31 bit long pseudo-random sequences is utilized to study this phenomenon. The magnetization instead of the waveform is analyzed to obtain higher spatial numerical resolution. The two nonlinear effects are identified from their echoes and their response to the writing precompensation is studied. It is found that partial erasure is not reduced efficiently by precompensation