Structural and magnetic properties of lead-bismuthate oxide glasses containing S-state paramagnetic ions S. Simon a, * , R. Pop b , V. Simon a , M. Coldea a a Faculty of Physics, Babes-Bolyai University, Str. M. Kogalniceanu nr. 1 Cluj-Napoca 3400, Romania b Department of Physics, University of Civil Engineering, B-dul Lacul Tei 124, Bucharest 723051, Romania Received 16 May 2003; received in revised form 28 July 2003 Abstract Electron paramagnetic resonance and magnetic susceptibility measurements on vitreous samples of (100  x)[4Bi 2 O 3 ® PbO]xMO and (100  x)[3Bi 2 O 3 ® 2PbO]xMO systems, where MO ¼ Fe 2 O 3 , MnO or Gd 2 O 3 and x ¼ 1, 5, 10 and 20 mol%, indicate important differences regarding the surrounding, valence state and magnetic interactions of the paramagnetic ions. A tendency to cluster, favoring the devitrification of the matrix, is shown to occur in all cases with increasing MO content, while up to 5 mol% a stabilizing effect on the vitreous lead-bismuthate network is ob- served. The highest stabilizing effect is observed for gadolinium. Magnetic data suggest an antiferromagnetic interaction between the paramagnetic ions for x P 5 mol% MO. The magnetic moments of the samples indicate that iron and manganese occur in both (II) and (III) valence states. The magnetic moments measured for samples containing gad- olinium are in all cases smaller than the value corresponding to free Gd 3þ ions and decrease with increasing gadolinium content. The decrease is linear and is more pronounced in the 3Bi 2 O 3 ® 2PbO glass matrix than in the 4Bi 2 O 3 ® PbO matrix. In order to explain the lower magnetic moments per atom for Gd 3þ ions, a model considering short range interactions is proposed. The model can be considered for all glasses with high paramagnetic ions content. Ó 2003 Elsevier B.V. All rights reserved. PACS: 61.43.Fs; 75.20.Ck; 76.30.)v 1. Introduction Generally obtained by quick undercooling of melts, glasses are metastable systems in which different relaxation processes tend to decrease the frozen-in structural disorder. Structural relaxation of glasses may involve local rearrangements of atoms or, under certain conditions, may lead to a partial or complete crystallization of the glass. Glasses with a high content of heavy metals, like Bi 2 O 3 and PbO, are intensely investigated because of their properties such as high density, high re- fractive index, excellent IR transmission and high polarisability [1–5]. All of these properties are ex- ploited in applications such as thermal and me- chanical sensors [5], wave-guides in non-linear optics [6], scintillation detectors in high-energy physics [6,7]. At the same time the study of glasses containing small amounts or no classical glass * Corresponding author. Tel.: +40-264 405 300; fax: +40-264 591 906. E-mail address: simons@phys.ubbcluj.ro (S. Simon). 0022-3093/$ - see front matter Ó 2003 Elsevier B.V. All rights reserved. doi:10.1016/j.jnoncrysol.2003.08.079 Journal of Non-Crystalline Solids 331 (2003) 1–10 www.elsevier.com/locate/jnoncrysol