Magnetic and electric behaviour of some lead-borate glasses with manganeseions

Magnetic susceptibility and electric resistivity measurements have been per formed on xMnO.(100 - x)(2B(2)O(3). PbO] glasses with 0 < x < 80 mol%. Magn etic data suggest that for x > 30 mol% the manganese ions experience negati ve magnetic superexchange interactions. Prom Curie constant values we have established that in these glasses both Mn2+ and Mn3+ ions are present, whic h explains their magnetic and electric behaviour. The conductivity increase s while the conductivity activation energy decreases with the MnO content. In order to analyse the conductivity data, we have considered in all glasse s a polaronic model for conduction.