Influence of charge transfer on the crystal field in rare-earth chalcogenides and pnictides

Abstract

Crystal field parameters and pressure dependent susceptibility and Knight shift data for tri-valent rare-earth pnictide and chalcogenide compounds are analyzed. The three rare-earth valence electrons are assumed to distribute themselves amongst the anion p bands and rare-earth 5d bands. It is argued that under pressure, the charge transfer from the rare-earth to the anion p band is modified and that this process dominates in producing the observed pressure dependence of the crystalline electric field parameters. The rate of transfer of p electrons back to the rare-earth 5d band under pressure is found to be approximately one order of magnitude less for the chalcogenides than for the pnictides and it is suggested that this is due to smaller d-p overlap arising from the position of the chalcogenide p band with respect to the Fermi level and the d band level.