L10 phase formation in FePd thin films induced by H2 during annealing

Equiatomic FePd thin films with a thickness of 5 nm were deposited at room temperature by magnetron sputtering on the thermally oxidized silicon substrates. Annealing in vacuum and in hydrogen atmosphere was used to transform the chemically disordered A1 FePd films into the chemically ordered L1(0) FePd phase. The influence of annealing atmosphere, annealing temperature, and annealing time on the ordering process of the films was studied. Annealing in hydrogen atmosphere at 650 degrees C accelerates the ordering process and leads to the L1(0) FePd phase. However, the incorporation of H also influences the electronic structure and thus the magnetic properties. A further increase in annealing time or temperature (over 650 degrees C) accelerates the L1(0) ordering process but also alters drastically the film morphology forming a fine grainy structure, which appears X-ray amorphous rares. The latter even results in a most likely superparamagnetic state.