First-principles investigations of Zr-based quaternary Heusler alloys for spintronic and thermoelectric applications

Quaternary Heusler Alloys (QHAs) have become increasingly attractive as thermoelectric and spintronic mate-rials. Density functional theory (DFT) calculations are utilized to investigate the structural, dynamic, elastic, thermodynamic, electronic, magnetic, thermoelectric properties are studied for the new ZrTiRhZ (Z = Ge, Sn) QHAs. Based on the energy minimization, these two new alloys are stable in Type-III structure. The two QHAs are found to be half-metallic with a semiconducting behavior in minority-spin channel and a spin-polarization of 100%. In addition, they show a total magnetic moment of 3 mu B obeying the Slater Pauling rule (Mtot = (Ztot-21) mu B). The semi-classical Boltzmann theory are used to calculate the transport coefficients (Seebeck coefficient (S), electrical conductivity (a), electronic conductivity (kappa e) and power factor (PF), whereas the lattice thermal conductivity (kappa L) is calculated by using the Slack model. The highest values of the figure-of-merit (ZT) are 0.51 and 2.92 for ZrTiRhSn and ZrTiRhGe QHAs, respectively. The half-metallic behavior and high figure-of-merit values of ZrTiRhZ (Z = Ge, Sn) QHAs are promising for applications in spintronic and thermoelectric devices.