Electronic structure of nitrogen-vacancy doped SmN: Intermediate valence and 4f transport in a ferromagnetic semiconductor

Abstract

SmN is an intrinsic ferromagnetic semiconductor with electrical transport properties that have been of recent experimental interest. Its conductivity is largely dictated by the concentration of nitrogen vacancies that dope the crystal with electrons. Here, we present a density functional theory based study of SmN, variously doped with nitrogen vacancies. We find that the Sm ions which coordinate a nitrogen vacancy take on an intermediate $2--{3}^{+}$ valence, while the remaining Sm ions in the crystal remain trivalent. Our results show that the localized $4f$ states hybridize with the extended state Sm $5d$ and N $2p$ bands and are involved in electron transport throughout the crystal.