Structural, electronic and magnetic properties of Ti1+xFeSb Heusler alloys

Density functional theory calculations based on full potential linearized augmented plane-wave (FP-LAPW) plus local orbital method in the framework of GGA-PBE, as embodied in the WIEN2k code, is used to investigate the structural, electronic and magnetic properties of intermetallic Ti1+xFeSb Heusler compounds, where (x=−0.75,−0.50,−0.25,0.0,0.25,0.50,0.75,1.0). Moreover, the Tran-Blaha parameterized of the modified Becke-Johnson (TB-mBJ) exchange potential, as a semi-local method, is employed to predict the bandgap more precisely. The physical characteristic of these systems are found to be mostly determined by the crystal structure and the electron concentration or the number of valence electrons. We examined the site preference of the parent compound TiFeSb and varied the electron concentration by doping or removing a Ti atom and we found that the variation plays a crucial role in the physical properties of these material systems. Alloys with x≤0 are found to exhibit a ferrimagnetic phase, and the alloy with x=0.25 exhibits non-magnetic properties, whereas the rest have shown ferromagnetic phase. The band-structure analysis of Ti1.75FeSb and Ti2FeSb (CuHg2Ti-type) alloys suggested that they could be ferromagnetic half-metallic candidates with bandgaps 0.350 and 0.468 eV, respectively. We found that Ti rich Ti1+xFeSb alloys have high spin polarization.