Effect of Ti addition on the microstructural, mechanical, magnetic, and Mössbauer spectroscopic properties of Ni–Fe–Ga Heusler alloys

Abstract Although Ni–Fe–Ga-based alloys have been widely studied for their functional properties, previous works have primarily focused on stoichiometric or near-stoichiometric compositions, particularly in the form of ribbons, thin films, or rapidly solidified materials. Ti addition to these alloys has been explored only rarely and with a limited focus on their properties. In this study, we investigated the effect of Ti addition on the microstructure, mechanical, and magnetic properties of the alloys, as well as their Mössbauer spectroscopic behavior, which is reported here for the first time to the best of our knowledge. Hardness, elastic modulus, and ultimate compressive strength initially increased with the addition of 0.2 at% Ti to the base Ni–Fe–Ga alloy, and then decreased with 0.8 at% Ti addition. However, ductility improved by approximately 50% at this Ti content. Magnetization measurements under an external magnetic field revealed successive hysteresis loops with increasing Ti content. A very low coercivity value of 3.87 Oe was obtained for the base alloy, which further decreased with increasing Ti content. Mössbauer spectra of all alloys exhibited a sextet and two doublet components. The sextet, with a hyperfine magnetic field of approximately 33 T, was attributed to magnetically ordered Fe environments originating from different crystallographic or chemically distinct local surroundings. The paramagnetic contribution corresponding to the observed doublets was considered to arise from Fe atoms occupying Ga sites. Overall, the results demonstrate that Ti addition plays a crucial role in tailoring the structural, mechanical, and magnetic responses of Ni–Fe–Ga alloys, and provide new insight into their local atomic and magnetic environments through Mössbauer spectroscopy.