Pulse EPR spectroscopy of Cu2+-doped inorganic glasses

Two-frequency continuous-wave and pulse EPR (electron paramagnetic resonance) spectroscopical techniques are applied to determine static and dynamic EPR parameters of Cu²⁺ ions in oxide and fluoride glasses. The investigations are focussed on the analysis of strain effects in the glassy matrices, the identification of the magnetic nuclei in the vicinity of Cu²⁺ ions as well as the determination of the dependence of the phase memory timeT _M on temperature and resonance field. The results obtained by X-band continuous-wave EPR, X- and S-band echo-detected EPR, and X- and S-band electron spin echo envelope modulation studies of Cu²⁺-doped inorganic glasses yield information on the local symmetry of the Cu²⁺ coordination polyhedra, the chemical nature of the atoms in the second and higher coordination spheres, the distribution of the parameters of the static spin Hamiltonian and the low-temperature motions of the dopant-containing structural units. Special techniques like 2-D Mims ENDOR (electron nuclear double resonance) and hyperfine-correlated ENDOR are applied for the first time to doped inorganic glasses. From the spin relaxation measurements a stronger tendency of the Cu²⁺ ions to aggregate is found for fluoride glasses in comparison to aluminosilicate and phosphate glasses.