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 sample s (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 appr oximate to 4.3 and g approximate to 2.0. For manganese-doped samples both l ines 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, corre sponding to different values of x, induce changes in the surroundings of th e resonance centers. Structural data obtained from the EPR measurements indicate various sites f or Mn2+ and Fe3+ ions in environments characterized by different crystallin e field intensities. The EPR data also provides evidence that the redox eff ect of bismuth-borate matrices on the doped paramagnetic ions is a function of Bi/B ratio.