Formation of Reversed Magnetic Domains by Recording in a Co/Pd Multilayer Film with Perpendicular Magnetic Anisotropy

Lianjun WU  Naoki HONDA  Kazuhiro OUCHI  

IEICE TRANSACTIONS on Electronics   Vol.E83-C   No.9   pp.1511-1516
Publication Date: 2000/09/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Selected Papers from the 4th Asian Symposium for Information Storage Technology)
magnetic domains,  MFM observations,  Co/Pd multilayer film,  perpendicular magnetic anisotropy,  

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A Co/Pd multilayer film with perpendicular coercivity of 2.2 kOe and remanence ratio (SQ) of unity was prepared by electron beam evaporation in vacuum. In the MFM image of 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 direction using an electromagnet (H = -13 kOe), only few reversed magnetic domains were observed, which was consistent with SQ = 1. Therefore, the reversed domains in the signal patterns were induced in the recording process. dc erasing was also studied with the magnetic field inclined to the film normal. The domain structures were almost the same when the perpendicular component of the field was kept constant while the in-plane component was varied, implying that the in-plane field component did not contribute to the formation of the reversed domains. It was found that reversed magnetic domains were easily induced even by a weak reversing magnetic field applied along the film normal. Hence, although the possibility of an insufficient recording head field was not excluded, it seemed more likely that the reversed magnetic domains in the signal patterns were caused by some erasing effect of the ring-type MIG head. For a Co/Pd multilayer medium with a negative nucleation field in the perpendicular M-H loop, a stronger reversing field was needed to induce the reversed magnetic domains. No reversed magnetic domains were observed in the MFM image for signal patterns of 4 kFRPI in this medium, indicating that a negative nucleation field was effective to suppress the formation of reversed magnetic domains.