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

Abstract

The 360° domain wall loops were studied using a magnetic force microscope (MFM) in a glass/Ta(10 nm)/NiFe(12 nm)/NiO(6 nm)/Ta(5 nm) multilayered film fabricated by magnetron sputtering. The film had an enhanced coercivity 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° domain wall, and this interaction was used to probe the structure and dynamics of the wall. The repeated scanning action of the tip causes the transformation from a 360° wall loop into a 180° wall loop. The magnetization 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 analysis. The study of the transformation process provided a better understanding of the structures of the 360° walls. This work suggests that the tip–sample interaction could be a useful tool for studying the domain wall structures.