Crystal field study of Gd~(3+)-doped La_xRE_(1-x)F_3 (RE = Ce, Pr, Nd) single crystals

摘要

The mixed La_xRE_(1-x)F_3 (RE = Ce, Pr, Nd) single crystals doped with Gd~(3+) (0.1 mol%) were grown by a modified Bridgmann-Stockbarger method. The crystal field was investigated using electron paramagnetic resonance technique. The angular dependencies of Gd~(3+) (~8S_(7/2), f~7) line positions with magnetic field oriented in (001) plane were measured in the temperature range 4.2 - 295 K. The surroundings of Gd~(3+) ions were investigated analyzing spin-hamiltonian parameters in the light of the superposition model. The small distortion of the D_(3d)~4 trigonal symmetry has been observed in LaF_3, La_(0.9)Ce_(0.1)F_3 and La_(0.9)Nd_(0.1)F_3 below 150 K. The local structure deformation of the site symmetry of Gd~(3+) ions induced by temperature starts at about 150 K becoming larger at 4.2 K. In PrF_3 the distortion was not observed in the temperature range 4.2 - 295 K. The results were compared with those of Gd~(3+)-doped LiYF_4 crystals.