Amorphous bilayered CoFeCrSiB ribbons: microstructure and magnetism

This work is devoted to the complex structural and magnetic investigations of the soft magnetic amorphous bilayered Co69Fe2Cr7Si8B14/Co59Fe12Cr7Si8B14 (Co/Co) ribbons. Their surface, bulk, and interface properties are compared with the properties of corresponding single-layered ribbons and the CoSiB/FeSiB (Co/Fe) bilayered ribbons analyzed in the previous work. All samples were prepared by rapid solidification of a melt using planar flow casting method. It is shown that the bulk microstructural and magnetic properties of the bilayered ribbons in both initial and thermally treated states are more outstanding influenced by the chemical composition of the side which is during ribbon processing in contact with air atmosphere. Analysis of thin interface (thickness lower than 1~µm) newly comprehends a method for observation of magnetic domains using the magneto-optical Kerr microscopy. Relaxation of the sample properties is checked by annealing at temperature 423 K for different times. Long-time annealing contributes to an improvement of the soft magnetic properties but simultaneously initializes the nucleation of crystallites on the surface of the Co/Co ribbons.