Structural and magnetic evolution of FeCoNiAlMn thin films under varying Mn content and annealing temperatures

This study focuses on FeCoNiAl films with varying concentrations of Mn added, deposited using the DC sputtering technique. All films were fabricated with a uniform thickness of approximately 100 nm. Four series of FeCoNiAl-Mnx films were prepared at room temperature and subsequently annealed at different temperatures: 400°C, 600°C, and 800°C. The annealing was carried out in a furnace under an argon atmosphere, with a heating rate of 2°C/min for a duration of 1 h. The X-ray diffraction (XRD) analysis reveals that the crystal structure changes as a function of both Mn concentration and annealing temperature. The structure transitions from face-centred cubic (FCC) in FeCoNi to body-centred cubic (BCC) upon the addition of Al and Mn, and eventually to an amorphous phase at higher AlMn concentrations. The magnetic properties also exhibit significant changes upon annealing at 400°C. For the Fe1.2CoNiAl1.4Mn2.5 film, the saturation magnetization increases by approximately 35-fold. Similarly, the Fe1.1CoNiAl1.5Mn5.3 film demonstrates a tenfold increase in saturation magnetization, accompanied by marked reductions in coercivity and remanence, by factors of roughly 29 and 43, respectively.