EPR of Mn2+ and Fe3+ ions doped in bismuth-borate glasses

Experimental EPR results of 99.5%[xB(2)O(3)(1 - x)Bi2O3]0.5%MO glass samples (MO = MnO, Fe2O3 and 0.07 less than or equal to x less than or equal to 0.8) systems are presented. The resonance absorptions are centered at g approximate to 4.3 and g approximate to 2.0. For manganese-doped samples both lines show hyperfine structure for certain values of Bi/B ratio. In addition to these lines a well defined shoulder at g approximate to 9.8 is recorded from the samples doped with iron. The changes in matrix composition, corresponding to different values of x, induce changes in the surroundings of the resonance centers. Structural data obtained from the EPR measurements indicate various sites for Mn2+ and Fe3+ ions in environments characterized by different crystalline field intensities. The EPR data also provides evidence that the redox effect of bismuth-borate matrices on the doped paramagnetic ions is a function of Bi/B ratio.