Non-linear interactions in a series of transitions [magnetic recording]

A theoretical model and experimental measurements are presented that demonstrate that when a series of transitions is written on the magnetic medium, each transition in series has different value of Non-Linear Transition Shift (NLTS). NLTS values oscillate between larger and smaller levels and gradually settle to a steady value. The oscillations of NLTS explain the observed differences between the values of NLTS measured by spectral elimination and by the pseudo-random methods. Experimental data supports the theoretical prediction that NLTS levels measured by spectral elimination method are 10-20% larger than those measured by pseudo-random techniques. When the magnetic medium has initial magnetization, NLTS interacts with hard transition shift and NLTS oscillations do not settle. These oscillations have been experimentally demonstrated for inductive and MR heads. Experimental studies of PRML system performance demonstrate that interactions of NLTS with hard transition shift degrade error rate of PRML systems and limit effectiveness of NLTS precompensation.