High field electron paramagnetic resonance of Gd3+-doped glasses: Line shapes and average ion distances in silicates

The average distances between Gd3+ ions in multicomponent silicate glasses doped with 0.058 to up to 4.64 wt % Gd2O3 are characterized by electron par amagnetic resonance (EPR) line broadening effects at high-field (95 GHz, W band). Increase in the EPR resonant field/frequency above that of the conve ntional X band (9.5 GHz) simplifies the Gd3+ EPR spectra and increases the sensitivity of the EPR linewidth to concentration induced broadening effect s. Least squares line shape simulations show that the broadening can be des cribed by a Lorentzian function with a width proportional to the average Gd 3+ concentration which is in good agreement with the existing theories. Ana lyses of the concentration dependence of Lorentzian line broadening indicat e an onset of clustering of Gd3+ ions at >1wt % doping levels. (C) 2001 Ame rican Institute of Physics.