Elementary magnetization processes in a low-anisotropy circular thin film disk

Domain observations during the magnetization process of small circular-shaped high-J_s multilayered thin-film elements were made using a high-resolution Kerr technique in addition to a digitally enhanced image-processing system. In order to check recent theoretical predictions, the authors determined the magnetization distribution of some typical domain patterns which can be observed during the magnetization process. In some cases the magnetization process becomes irreversible and other more complicated remanent domain patterns may occur. Domains on circular thin-film elements are found to agree in their basic behavior with theoretical predictions for zero-anisotropy elements if the ground state consists of a simple circular magnetization pattern. The formation of a c-shaped domain wall and its position as a function of an applied field agree well with theory. This is true even though the present samples have a nonvanishing uniaxial anisotropy and the circular domain pattern is favored only due to a stress-induced edge anisotropy. Complications arise during and after magnetization along the hard axis of the uniaxial anisotropy. Some of the very attractive metastable states which can be generated in this way have been analyzed in detail