Formation of reversed magnetic domains by recording in a Co/Pd multilayer film with perpendicular magnetic anisotropy

A Co/Pd multilayer film with perpendicular coercivity of 2.2 kOe and remane nce ratio (SQ) of unity was prepared by electron beam evaporation in vacuum . In the MFM im- age of signal patterns of 4 kFRPI recorded using a ring-ty pe MIG head, many reversed domains were observed. However, when the film wa s magnetized along the film normal direction using an electromagnet (H = -1 3 kOe), only few reversed magnetic domains were observed, which was consist ent with SQ = 1. Therefore, the reversed domains in the signal patterns wer e induced in the recording process. de erasing was also studied with the ma gnetic field inclined to the film normal. The domain structures were almost the same when the perpendicular component of the field was kept constant w hile the in-plane component was varied, implying that the in-plane field co mponent did not contribute to the formation of the reversed domains. It was found that reversed magnetic domains were easily induced even by a weak re versing magnetic field applied along the film normal. Hence, although the p ossibility of an insufficient recording head field was not excluded, it see med more likely that the reversed magnetic domains in the signal patterns w ere caused by some erasing effect of the ring-type MIG head. Fora Co/Pd mul tilayer medium with a negative nucleation field in the perpendicular M-H lo op, a stronger reversing field was needed to induce the reversed magnetic d omains. No reversed magnetic domains were observed in the MFM image for sig nal patterns of 4 kFRPI in this medium, indicating that a negative nucleati on field was effective to suppress the formation of reversed magnetic domai ns.