A Co/Pd multilayer film with a perpendicular coercivity of 2.2 kOe and SQ of unity was prepared by electron beam evaporation in vacuum. In the MFM image for signal patterns of 4 kFRPI recorded using a ring type MIG head, many reversed domains were observed. However, when the film was magnetized along the film normal using an electromagnet(H=13 kOe), few reversed magnetic domains were observed, which was consistent with SQ=1. Therefore, the reversed domains in the signal patterns occurred in recording process. The dc erasing was also studied with the magnetic field inclined to the film normal. The domain structures were almost the same when the perpendicular components of the field were kept constant while the in-plane components were varied, implying that the in-plane field component did not contribute to the formation of the reversed domains. Reversed magnetic domains were easily induced even when a weak reversing magnetic field was applied along the film normal. Hence, the reversed magnetic domains in the signal patterns were considered to be caused by some erasing effect of the ring type MIG head. A large negative nucleation field in the perpendicular M-H loop is effective to suppress the reversed magnetic domains.