First-principles calculations to investigate new ferromagnetic quaternary Heusler alloys FeZrTiZ(Z=Si, Sn, Pb): Compatible for spin polarized device and waste heat recovery applications

In this article, we have studied the structural, electronic, magnetic, mechanical and thermoelectric properties of new quaternary Heusler alloys FeZrTiZ (Z = Si, Sn, Pb), using ab-initio simulation methods. Our structural phase stability studies show that all these compounds stabilize in Y1-type structure and showing ferromagnetic ground state. From the calculation based on Generalized Gradient Approximation method we found that all these alloys are having half metallic behavior with the band gap value of around 1eV in one of the spin channels. The half metallic nature of these alloys is a precursor for high spin polarization. These alloys also satisfy the Slater-Pauling rule with magnetic moment of M-T = N-V -18 for half metallicity and as a result they have a total magnetic moment of 2 mu B. The calculated elastic constants convey the mechanical stability of these alloys and though they have a cubic structure they exhibit strong mechanical anisotropy with ductile behavior. The Seebeck coefficient and the thermoelectric figure of merit were calculated using semi-classical Boltzmann transport theory. The highest Seebeck coefficient value for FeZrTiZ (Z = Si, Sn, Pb) is 110.5 mu V/K, 121.8 mu V/K and 100.6 mu V/K respectively at the temperature 900 K, 600 K and 750 K and the corresponding figure of merit is 0.85, 0.9 and 0.59. The observation of half metallicity indicates that these materials can be used in spintronic devices and the observation of substantial thermoelectric figure of merit suggests that these materials can be used in waste heat recovery.