Structure and crystal fields of PrBr3 and PrCl3: A neutron study

Abstract

The crystal structures of PrX3 (X=Br, Cl) and particularly the detailed coordination of the halides X have been studied by neutron diffraction on polycrystalline samples in the temperature range between 4.2 and 293 K. Furthermore, the crystalline electric fields (CEF) in the two compounds have been investigated by inelastic neutron scattering experiments on single-crystal samples. The observed CEF transitions have been identified according to the transition matrix elements and the polarization factor in the neutron cross section, which allowed an unambiguous determination of the four CEF parameters for hexagonal symmetry. The energetic ordering of the CEF levels in PrBr3 and PrCl3 are considerably different which can be understood in terms of the different geometric coordination of the halides determined from the diffraction results.