Impact of increasing aluminium content on the magnetic, electrical, and structural properties of FeCoNiMnAl thin films

This paper studies the magnetic and electrical properties of adding Al and Mn to the ternary FeCoNi alloy. FeCoNi has soft magnetic properties; however, due to Co and Ni being classed as critical materials, reducing their content in the films while enhancing the magnetic and electrical properties is important for future applications. The magnetic thin films were prepared using DC sputtering, with all the films having an uniform thickness of 100 nm. The crystal structure of the films was analysed using XRD, which revealed a change from FCC for the FeCoNi film to BCC for the FeCoNiMnAl films. The composition of the films was determined using X-ray Photoelectron Spectroscopy (XPS). It was found that adding Mn to FeCoNi did not result in any noticeable magnetic improvement, but a change in morphology within the films from polycrystalline to amorphous. However, when both Al and Mn were added to FeCoNi, the coercivity and remanence decreased as the Al content increased, while the films now had a nanocrystalline BCC morphology. Additionally, the Fe1,4Co1.4Co1.2MnAl2 composition showed lower coercivity and remanence compared to FeCoNi. The saturation magnetization exhibited a significant decrease as the amount of Al and Mn in the films increased. While the electrical resistivity increased with the addition of Al and Mn. Finally, Fe1.4Co1.1Ni1.1MnAl1.3 appears to be a promising candidate for soft magnetic applications due to its reduced cost compared to FeCoNi and its improved resistivity compared to permalloy.