MgFeGe as an isoelectronic and isostructural analog of the superconductor LiFeAs

Abstract

MgFeGe with a CeFeSi-type structure was synthesized by high-pressure method, and its electrical transport, magnetic properties, and electronic structure were investigated. It is found that MgFeGe has the smallest $c$/$a$ (1.65) ratio and the shortest in-plane Fe-Fe distance (2.75 \AA{}) among CeFeSi-type and ThCr${}_{2}$Si${}_{2}$-type rare-earth iron silicides and germanides containing square lattice of iron. Further measurements demonstrate that this compound exhibits metallic conduction and Pauli paramagnetism from room temperature down to 2 K. From density functional theory calculations it is revealed that MgFeGe favors the same antiferromagnetic ground state magnetic configuration as LiFeAs. Moreover, considerable resemblance in the band dispersion, density of state, and Fermi surface was confirmed between MgFeGe and its isoelectronic superconducting counterpart LiFeAs. The results, however, suggest that the presence of the basic structural and electronic features of iron-based superconductors in MgFeGe does not necessarily lead to superconductivity, and further investigation is therefore still deserved to understand the related mechanisms.