Continuous wave and pulsed EPR spectroscopy of paramagnetic ions in some fluoride, silicate and metaphosphate glasses

Abstract

Low concentrations of paramagnetic transition metal or rare earth ions often found in commercial glasses are ideal spin probes to explore the local structural disorder intrinsic to these materials. Investigations of the electron paramagnetic resonance (EPR) spectra of glasses have raised the question as to whether the spin Hamiltonian model provides a valid basis for interpreting spectra from disordered solids. This is because the connection between the spin Hamiltonian and its environment is subtle and indirect, the more so for the likely C1 spin-probe site symmetry in a glass. CW simulations of random network glasses is thought to require a distribution of spin Hamiltonians for C1 point symmetry sites (stochastic model) whereas powder simulations should be appropriate for micro-crystallite glasses. Present understanding concerns transitions in lightly doped glasses where individual spins are well separated; it is “bottom-up” thinking rather than “top-down” thinking normally applied to EPR simulation.