A promising thermoelectric response of fully compensated ferrimagnetic spin gapless semiconducting Heusler alloy Zr2MnAl at high temperature: DFT study

Abstract

In recent times, Heusler compounds have emerged as potential candidates for spintronics and thermoelectric materials owing to their interesting properties such as gapless semiconducting nature with fully compensated ferrimagnetic behavior, 100% spin polarization with high mobility of charge carriers and better thermoelectric figure of merit. Motivated by this fact, we have carried out a systematic theoretical investigation of structural, electronic, magnetic, thermoelectric and lattice dynamical properties of spin gapless Heusler alloy Zr2MnAl within the frame work of density functional theory based first principle calculation. Our ground state total energy calculations confirms the structural stability of antiferromagnetic phase of Zr2MnAl over ferromagnetic phase, which is in agreement with previous study. The positive value for Cauchy’s pressure (C12–C44) predicts ductile nature of the material. The band structure calculation reveals indirect band gap in spin down channel and zero band gap in spin up channel of valence and conduction bands confirming the spin gapless semiconducting nature of the compound. The real frequency of phonon modes throughout the Brillouin zone confirms the structural and dynamical stability of antiferromagnetic phase of Zr2MnAl, which is reported for the first time as per our knowledge. Calculated Seebeck coefficient in spin up and spin down channel reveals that the Zr2MnAl behaves as both n and p type thermoelectric materials with better output efficiency. The calculated thermoelectric figure of merit of 1.4 at 800 K, favors use of an alloy in recovery of waste heat at higher temperature and thermoelectric spin generators. The comprehensive analysis of various chemical potential dependent thermoelectric coefficients for enhancing thermoelectric performance for the material has been carried out. The obtained results propose Zr2MnAl as a potential candidate for high temperature thermoelectric devices. Higher optical gap in the phonon dispersive curve is responsible for decrease in lattice thermal conductivity with temperature, resulting in enhancement in thermoelectric figure of merit.