Magnetic and magneto-optical quenching in (Mn2+, Sr2+) metaphosphate glasses

Transition metal ions such as Mn2+, Fe2+, or Co2+ provide an interesting alternative to rare earth dopants in optically active glasses. In terms of their magneto-optical properties, they are not yet very well exploited. Here, we report on the effect of Mn2+ on Faraday rotation in a metaphosphate glass matrix along the join MnxSr1-x(PO3)2 with x = 0...1. Mn2+ shows small optical extinction in the visible spectral range and, compared to other transition metal ions, a high effective magnetic moment. At high Mn- levels, however, the magneto-optical activity of Mn2+ is strongly quenched due to ionic clustering. The magnetic properties of the heavily Mn2+-loaded phosphate matrix are dominated by a superexchange interaction in the Mn2+-O-Mn2+ bridge with antiparallel spin alignment between Mn2+ and O2- species. The apparent paramagnetic potential of Mn2+ species can therefore not be exploited at room temperature.