Band structure, quantum confinement, and exchange splitting in ${\mathrm{Sc}}_{1\mathrm{-}\mathit{x}}$${\mathrm{Er}}_{\mathit{x}}$As epitaxial layers buried in GaAs

Magnetotransport measurements have been used to explore the band structure of thin (20 nm) rare-earth monoarsenide (${\mathrm{Sc}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Er}}_{\mathit{x}}$As, x=0.57 and 0.68) epitaxial films buried in GaAs. The Hall resistance and transverse magnetoresistance were measured in magnetic fields from 0 to 9 T and temperatures from 1.5 to 300 K. The results are successfully projected on a model of the band structure that predicts that the rare-earth monoarsenides are semimetals with holes at the zone center and pockets of electrons on the zone boundary at the X point. Below 20 K, Shubnikov–de Haas oscillations are assigned to the zone-boundary electrons. Remarkably, the angular dependence of the quantum oscillations is best understood by assuming that the electrons are quantum confined and experience only the normal component of the applied magnetic field. A large splitting of the zone-boundary electronic band structure is observed and attributed to the exchange interaction with the 4f moments localized on the Er ions.