Magnetic properties and amorphous-to-nanocrystalline transformation by thermal treatments in Fe_84.3Si₄P₃B₈Cu_0.7 amorphous thin films

Highlights: • High-BS alloy, prepared in thin films form. • As-prepared films display low coercivity, comparable to rapidly quenched ribbons. • Furnace annealed films show even lower coercivity while retaining a high saturation. • On annealing, a fully nanocrystalline state is achieved in thin films. - Abstract: Thin films of nominal composition Fe_84.3Si₄P₃B₈Cu_0.7 have been prepared by sputtering from ribbons of the same alloy. Their microstructure has been studied by means of X-ray diffraction, differential scanning calorimetry and transmission electron microscopy, and reveals a partly amorphous state in the as-prepared samples. Their magnetic properties are soft and comparable to those measured on rapidly quenched ribbons. After annealing in furnace at temperatures up to 400 °C, their soft magnetic properties are improved thanks to the development of a fully nanocrystalline state. Annealing at higher temperature causes the coarsening of the α-Fe like grains, the development of hard magnetic phases and an increase of the coercive field