EPR study of clusters of rare-earth ions in mixed fluoride crystals

Abstract

The EPR spectra of the (BaF2)1 − x(CeF3)x system are studied for the concentrations x = 0, 0.001, 0.002, 0.005, 0.01, and 0.02. The appearance of new tetragonal centers is detected beginning from x = 0.002, the intensity of these centers being maximal at x = 0.01. The (CaF2)1 − x − y(CeF3)x(YF3)y double solutions with x = 0.001 and y from 0 to 0.02 are also studied. In addition to the ordinary tetragonal center, beginning from y = 0.001, a new tetragonal center appears with the same structure as in the previously studied mixed crystals based on BaF2—namely, the Ce3+-□-R3+ chain elongated along the fourfold axis substitutes the Ca2+-Ca2+-Ca2+ and Ba2+-Ba2+-Ba2+ chains in regular CaF2 and BaF2 crystals (□ is the cation vacancy, and R3+ is the Ce3+, La3+, or Y3+ trivalent ion).