On the incorporation of copper ions in heavy metal fluoride glasses

Cu2+ ions incorporated into (ZBLAN) fluoride glasses reflect via distributions of spin coupling parameters local randomness of the glass matrix. Cw-X-band ESR measurements at 4.2 K applying different values of the microwave power as well as computer simulations have shown that even at very low copper concentrations (<0.6 mol%) the Cu2+ ions form point defects coexisting and weakly interacting with magnetically coupled species. The tendency of Cu2+ ions to form aggregates is remarkedly higher than in oxide glasses which corresponds to a nonuniform distribution of the paramagnetic centres in the glass matrix. After cyclic heating and cooling processes, recrystallization of the matrix represented by lowering the line widths, and resolving hyperfine splittings in the g(parallel to) region could be observed.