Rare earth chalcospinels, electronic structure, intermediate-valent, and heavy-fermion character

Abstract

Rare earth ARE2X4 (A = Cd, Mg; RE = Ho, Er, Tm, Yb, Lu; X = S, Se) spinels were studied with quantum DFT calculations to investigate the electronic structure of these systems, primarily those related to Intermediate-Valence and Heavy-Fermion behavior. The ARE2X4 compounds have narrow 4f peaks; therefore, if these RE:4f peaks are close to the Fermi level, they could exhibit Intermediate-Valent and Heavy-Fermion character. With RE = Ho, Er, Tm, Lu, the compounds resulted in insulators, while RE = Yb presented metallicity, an Intermediate-Valent and Heavy-Fermion characters. When electron-doped, the ATm2X4 and AEr2X4 spinels were found to have a Heavy-Fermion character.