STRUCTURAL AND MAGNETIC STUDIES 
OF Fe2O3-B2O3-SrO GLASS SYSTEM

Rareş Lungu1, P.Păşcuţă2 and I.Ardelean1

 1 Faculty of Physics, Babes-Bolyai University, 400084 Cluj – Napoca
 2 Techical University of Cluj-Napoca, 400084 Cluj-Napoca, România

The glasses from xFe2O3· (100-x)[B2O3.SrO] system, with 0  x  40 mol%,  were prepared, using pure raw matrials, by undercooling method. 
	The structural properties of Fe2O3-B2O3-SrO glass system were studied by EPR       and magnetic measurements. EPR measurements show the presence of two absorption lines, one at g ≈ 4.3  for 0.5x30 mol % and another at g ≈ 2 for 3  x  40 mol% characteristic to Fe3+ ions. The signal from g ≈ 4.3 is given by the absorption of the isolated Fe3+ ions and situated in distorted octahedral symmetry (rhombic or tetragonal) subjected to effects of the strong crystalline field [1]. The resonance line from g ≈ 2 can be attributed to the isolated Fe3+ ions and/or to those that participate to the magnetic interactions, dipolar or superexchange, the last forming magnetic clusters [2-3].
        Magnetic measurements suggest that at certain concentration (x<30 mol %), the temperature dependence of the reciprocal magnetic susceptibility, follows a Curie law and over this concentration follows a Curie-Weiss law with the negative paramagnetic Curie temperature. The negative value of paramagnetic Curie temperature indicate that the magnetic superexchange interactions are of the antiferromagnetic type. The absolute value of these temperatures suggest that the intensity of the magnetic interactions is increasing with the increasing of iron ions.

REFERENCES
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[2] I.Ardelean, M.Peteanu, S.Filip, V.Simon, G.Gyorffy, Solid State Commun., 102(4), 341, (1997)
[3] S.P. Chanduri, S.K.Patra, J.Mat.Sci. 35,4735 (2000)