Effects of annealing on phase structure and magnetic characteristics of sputter deposited Ni2FeGa/Si (100) thin films

Abstract

This paper investigates the effects of post-deposition annealing on the evolution of phase structure and magnetic properties of magnetron sputtered Ni2FeGa/Si (001) thin films. The results revealed that the as-deposited film was partially crystallized in an fcc structure, i.e. [Formula: see text] phase. Crystallization of the amorphous structure into the [Formula: see text] phase was greatly encouraged following annealing at 723 K for 1 h. Annealing at higher temperatures for the same period triggered the formation of the bcc austenitic phase, which competed with the [Formula: see text] phase simultaneously for crystallization and grain growth. The evolution of phase structure and grain size also influenced the nanomechanical properties of the films according to the nanoindentation measurement. The film annealed at 873 K for 1 h showed high hardness and elastic modulus values of 11.1 GPa and 156 GPa. The [Formula: see text] phase showed stronger ferromagnetic characteristics relative to the bcc austenite due to the richer Fe content. This leads to the saturation magnetization to be maximized at 80 emu/g when annealed at 773 K for 1 h attributed to the enhanced film crystallinity and dominant volume fraction of [Formula: see text] phase in the thin film.