Structural, thermal, and electronic properties of Fe ₂VSi _1-xAl _x

In order to access the influence of the local environment on the structural and electronic properties of Fe ₂VSi, we investigated the Fe ₂VSi _1-xAl _x series of compounds by measuring electrical resistivity (ρ), thermal conductivity (κ), Seebeck coefficient (S), as well as heat capacity (C _p) as a function of temperature. For Fe ₂VSi, all obtained quantities exhibit anomalous features near the structural transition temperature T _s ≈ 123 K. For the nonstoichiometric compounds Fe ₂VSi _1-xAl _x, these anomalies remain evident but appear to be weaker as increasing A1 concentration. The corresponding transition temperature T _s decreases with x, indicating the suppression of the low-temperature tetragonal phase via A1 doping in Fe ₂VSi. Theoretical studies with ab initio calculations were also employed to investigate the present structural and magnetic phase transition. Both theoretical results and experimental observations consistently yield a possible disappearance of the structural transition beyond a critical concentration x _c≈0.25. In addition, several aspects regarding the structural and electronic properties were compared to those of other Heusler alloys.