Interplay of electronic structure and magnetism in Fe2 - and Rh2 -based Heusler alloys

Abstract

In this work, we present a comparative study of the structural, elastic, electronic, magnetic, and transport properties of Heusler alloys ${\mathrm{Fe}}_{2}\mathrm{Rh}Z$ and ${\mathrm{Rh}}_{2}\mathrm{Fe}Z$ with $Z=\mathrm{Al}$, Si, Ga, Ge, In, Sn using the density functional theory. The strongly constrained and appropriately normed functional is considered for the exchange-correlation functional. The newly Heusler T-type pseudocubic structures, ${\mathrm{T}}^{p}$ and ${\mathrm{T}}^{c}$, with alternating layers and columns of Fe and Rh along the [001] direction being $\ensuremath{\approx}26$ meV/atom lower in energy than the inverse XA structure are predicted as ground states for the ${\mathrm{Fe}}_{2}\mathrm{Rh}Z$ family. According to the convex hull analysis, all the considered alloys are thermodynamically and mechanically stable or meta-stable. Hybridization schemes and their role in the formation of half-metallicity depending on the weak tetragonal distortion are discussed. XA-${\mathrm{Fe}}_{2}\mathrm{RhSi}$ is only predicted to be half-metallic in the minority channel with $100%$ spin polarization and integer magnetic moment of $5{\ensuremath{\mu}}_{B}$, while the ground state T structure with layered ordering of Fe and Rh is characterized by the $73%$ polarization due to a pseudogap around Fermi level. Additionally, a large Seebeck coefficient and figure of merit for the spin-down channel of XA-${\mathrm{Fe}}_{2}\mathrm{RhSi}$ is predicted.