Electron paramagnetic resonance determination of the local field distribution acting on Cr³⁺and Fe³⁺in transition metal fluoride glasses (TMFG)

Abstract

Cr3+ and Fe3+ ions are used as paramagnetic probes of the local order in diamagnetic transition metal fluoride glasses (TMFG). EPR observations are made at S, X, K and Q band frequencies at different temperatures. It follows from the frequency dependence of the spectra that Cr3+ and Fe3+ ions are characterized by a continuous fine-structure parameter distribution in the range 0.06-0.55 cm-1 for Cr3+ and 0.04-0.33 cm-1 for Fe3+. The simulations of these spectra are computed with a fine-structure parameter distribution P(h20, lambda ) whose expression is determined by analogy with the distribution of electric field gradient P(Vzz, eta ) developed by Czjzek considering amorphous solids with random ionic coordination. An excellent agreement between observed and calculated spectra is obtained whatever the frequency band.