Study of 360 degrees domain walls in NiFe/NiO film by tip-sample interaction on magnetic force microscope

The 360 degrees domain wall loops were studied using a magnetic force micro scope (MFM) in a glass/Ta(10 nm)/NiFe(12 nm)/NiO(6 nm)/Ta(5 nm) multilayere d film fabricated by magnetron sputtering. The film had an enhanced coerciv ity but no M-H loop shift due to the thin NiO layer. It was found that the local magnetic field exerted by a MFM tip can strongly affect the 360 degre es domain wall, and this interaction was used to probe the structure and dy namics of the wall. The repeated scanning action of the tip causes the tran sformation from a 360 degrees wall loop into a 180 degrees wall loop. The m agnetization distributions for these domain walls were derived from the MFM images. The mechanism of the irreversible change of wall structures caused by the tip-sample interaction was investigated based on micromagnetic anal ysis. The study of the transformation process provided a better understandi ng of the structures of the 360 degrees walls. This work suggests that the tip-sample interaction could be a useful tool for studying the domain wall structures. (C) 2000 American Institute of Physics. [S0021-8979(00)80308-4] .