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Magnetic clusters development in (100 – x)[4Bi2O3 · PbO]xGd2O3 glasses

S. SIMON1,* , I. G. DEAC1, M. COLDEA1

Affiliation

  1. Faculty of Physics, Babes-Bolyai University, 400084 Cluj-Napoca, Romania

Abstract

Electron paramagnetic resonance(EPR) at room temperature and magnetic measurements in the temperature range 5 K-300 K at various magnetic field between 1 T and 9T for (100 – x)[4Bi2O3 · PbO] xGd2O3 glasses(x = 1; 5; 10 and 20 mol%) are reported. The magnetization curves were fitted with the phenomenological equation proposed by Gaj et al. [3], M = MS B7/2 [gBSH / kBTeff], where MS is the phenomenological saturation parameter, B7/2 is the Brillouin function for the spin S = 7/2 and Teff = T – T0 is an effective temperature, MS and T0 being treated as adjustable parameters. The negative value of T0 indicates that the magnetic interactions between the Gd ions are antiferromagnetic of short range as superexchange via oxygen ions. The values of the saturation parameters MS for all thermal untreated and treated samples are smaller than the expected value for the free Gd3+ ions. Gd3+- EPR spectra are the superposition of the well known U–type spectrum, containing prominent features with geff  5.9, 2.85 and 2.0 and of a resonance line at geff  4.8. The line width of the absorption at geff  5.9 increases with x concentration at low Gd2O3 concentration, but decreases very rapidly when approaching the concentration x= 20mol%. These results may be explained if one consider that the majority of Gd ions behave as free Gd3+ ions, while the others as antiferromagnetically coupled pairs Gd3+ - O - Gd3+ in the form of magnetic clusters whose sizes depend on the Gd2O3 concentration in the glasses..

Keywords

Magnetic clusters, Bi2O3-PbO-Gd2O3 glasses, ESR.

Submitted at: Nov. 15, 2006
Accepted at: March 15, 2007

Citation

S. SIMON, I. G. DEAC, M. COLDEA, Magnetic clusters development in (100 – x)[4Bi2O3 · PbO]xGd2O3 glasses, Journal of Optoelectronics and Advanced Materials Vol. 9, Iss. 3, pp. 583-586 (2007)