Zinc based chalcogenides ZnMn2X4 (X = S, Se, Te) as promising spintronic and sustainable energy materials: Ab-initio DFT investigations

Abstract

To probe the applications in spintronics and sustainable energy devices of ZnMn2X4 (X=S, Se, Te) spinels, their structural, elastic, electronic and thermoelectric properties have been studied in the present work. Structural properties reveal stability of ferromagnetic (FM) phase in these spinels which is further confirmed by computing the heat of formation for these compounds. The mechanical properties of the ZnMn2X4 spinels have been investigated by computing their elastic constants, which show that all these spinels exhibit a brittle character. Moreover, electronic band structure and density of states reveal a half-metallic FM structure in all these spinels. Analysis of the band structure of these materials reveals a semiconducting nature in the spin down channel. Exchange constants (N0α and N0β) have been computed to directly probe the state splitting and our results large splitting of Mn 3d-states by N0β owing to its larger negative value as compared to N0α. The strong p-d hybridization is found to make exchange field dominant to crystal field which consequently induces ferromagnetism. In addition, the p-d hybridization reduces the magnetic moment of Mn ions by inducing traces of magnetic moments at non-magnetic sites. The observation of thermoelectric behavior within temperature range 200K–800K reveals positive Seeback coefficient indicating holes as majority charge carriers. Although the power factor is found to increase on going from ZnMn2S4 to ZnMn2Te4, our results clearly show improvement of power factor with increasing temperature.