Magnetic and magneto-optical quenching in (Mn^2+, Sr^2+) metaphosphate glasses

Transition metal ions such as Mn[2+], Fe[2+], or Co[2+] 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 Mn[2+] on Faraday rotation in a metaphosphate glass matrix along the join Mn{x}Sr{1-x}(PO{3}){2} with x = 0...1. Mn[2+] 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 Mn[2+] is strongly quenched due to ionic clustering. The magnetic properties of the heavily Mn[2+]-loaded phosphate matrix are dominated by a superexchange interaction in the Mn[2+]-O-Mn[2+] bridge with antiparallel spin alignment between Mn[2+] and O[2-] species. The apparent paramagnetic potential of Mn[2+] species can therefore not be exploited at room temperature.