Medium noise properties of Co/Pd multilayer films for perpendicular magnetic recording

Co/Pd multilayer media showing different medium noise properties were investigated through the observations of the recorded patterns using a magnetic force microscopy (MFM). For the Co/Pd multilayer medium sputter-deposited at 1 Pa, no reversed magnetic domains were observed between transitions, while the transitions were quite irregular, suggesting a transition noise in this medium. On the other hand, for the Co/Pd multilayer media prepared with an evaporation-deposition method, although locally reversed magnetic domains were observed, the transition lines were straight. Thus, the medium noise in this case appeared to be a white noise caused by the locally reversed magnetic domains between the transitions. Patterns of signals only up to 200 kFRPI were observed for the Co/Pd multilayer medium sputter-deposited at 1 Pa, which exhibited a strong magnetic exchange interaction. However, a signal of 400 kFRPI was recognized for the Co/Pd multilayer medium with a reduced magnetic exchange interaction, which was prepared by evaporation-deposition with the introduction of a small amount of air. (C) 1999 Elsevier Science B.V. All rights reserved.