The electron paramagnetic resonance spectra of Cu2+ ions (2D5/2) located at 2 structurally non-equivalent positions Cu1 and Cu2 in crystals of lithium heptagermanate Li2Ge7O15 were recorded. The angular dependences of the electron paramagnetic resonance spectrum were measured in the paraelectric phase of the Li2Ge7O15 compound (300K). The components of the g-factor and the hyperfine interaction tensor A were determined, and the orientation of the magnetic axes with respect to the crystallographic basis was established. The electron paramagnetic resonance spectra were recorded in the temperature range in the vicinity of the temperature TC = 283K of the transition from the paraelectric phase to the ferroelectric phase. The position symmetry of the Cu1 and Cu2 centers was determined at temperatures above and below the phase transition temperature TC . The localization of paramagnetic centers in the structure was considered. An analysis of the results obtained demonstrated that the Cu1 and Cu2 centers in the Li2Ge7O15 crystal lattice replace Li ions located at two structurally non-equivalent positions with the symmetries described at temperatures above TC by the triclinic Ci and monoclinic C2 point groups, respectively.

EPR Study of Copper Ions in Li2Ge7O15 Crystals. M.P.Trubitsyn, M.D.Volnyanskiĭ, A.N.Dolinchuk: Physics of the Solid State, 2008, 50[8], 1427-32