EPR of Gd3+ in a single crystal of thorium disulfide (ThS2)

In this paper we report the experimental angular behaviour of the EPR spectra for a single crystal of Thorium disulfide (THS2) doped with Gd3+ at very low concentration (of the order of 10 p.p.m.). The experimental data are interpreted in terms of a spin Hamiltonian which reflects the crystal field symmetry at the Th site, that is monoclinic Csub(s) and therefore shows that the doping ions enter substitutionally without lowering the site symmetry. The low symmetry and the unusually large values of the crystal field parameters b20 and b22 have made it necessary to use a numerical fitting procedure, starting from the exact numerical diagonalization of the energy matrix for any given direction of the static magnetic field. (orig.)