Simulation of the paramagnetic susceptibility in rare earth oxychlorides

The average magnetic susceptibilities of polycrystalline rare earth oxychlo rides (REOCl; RE = Ce, Pr, Nd, Sm, Tb, Dy and Ho) were measured between 2 a nd 300 K. The susceptibility of most REOCl samples follows the paramagnetic Curie-Weiss behaviour down to low temperatures (<20 K). However, TbOCl, Sm OCl, and DyOCl show additional antiferromagnetic ordering at 4, 8, and 11 K , respectively. The experimental paramagnetic susceptibilities were simulat ed with the aid of the van Vleck formalism based on the wave functions and energy level values obtained from a previous phenomenological simulations o f spectroscopic data. The deviation of the magnetic susceptibilities of sev eral REOCl from the Curie-Weiss behaviour at low temperatures can be explai ned by the gradual population of the crystal field (c.f.) components of the ground L-2s+1(J) level. At high temperatures the difference between the ca lculated and experimental data is due to the modification of the c.f. effec t as a result of the lattice expansion. The strong preferred orientation of the REOCl crystallites may affect the experimental data because of the str ong anisotropy of the paramagnetic susceptibility. (C) 2000 Elsevier Scienc e S.A. All rights reserved.