Incomplete switching of media magnetization in perpendicular magnetic recording

Incomplete magnetization switching may take place between two recorded transitions in perpendicular magnetic recording. These write process issues were studied with a micromagnetic model. The relatively poor effective field from the central part of the perpendicular writer is unable to reverse the media grains properly. Consequently, media dc noise will increase as the incomplete switching becomes more severe. An expression for the effective field h(eff) was proposed to easily discover those cases. The incompletely switched magnetization observed in the static footprint could also be partially transferred into the dynamic write process. The calculated media signal-to-noise ratio on a pseudorandom sequence could be reduced by as much as 3 dB (compared to the fully switched case). On the other hand, transition quality does not become worse with a smaller h(eff). This insensitivity to the transition quality was caused by the magnetostatic field from the opposite magnetization polarity on the other side of the recorded bit. (C) 2006 American Institute of Physics.