Transition position shift in double layered perpendicular recording media with soft underlayer

Abstract

In perpendicular recording, double layered media with soft underlayer (SUL) are outstanding in view of increasing writing head field and the head field gradient. However, the SUL could serve as various noise sources. In order to investigate the effect of SUL on noise, writing and reading processes in a perpendicular system including a single pole head and a recording medium with the SUL were performed by micromagnetic simulation. It was found that when an abrupt head field is applied, the SNR of the double layered medium shows much lower SNR compared with the single layered medium. The higher noise in the double layered medium is not associated with transition jitter but with transition position shift. The transition position shift is associated with change of magnetization pattern of the SUL with time during writing process. In the present paper, we discuss the change of magnetization patterns of the SUL with time, for two different head sizes. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.