EPR of Gd³⁺ with g≈6.0 in glasses: a reinterpretation

Gd³⁺ in glasses exhibit sharp g approximately=6.0 features in the EPR spectra. It is demonstrated that these features can be adequately accounted for by using the 'rhombic' spin Hamiltonian H=g_c beta H.S+D(S_z²-(S/3)(S+1))+E(S_x²-S_y²) in the strong crystal field case. Computer simulations of the experimental Gd³⁺ spectra in phosphate glasses result in the following estimates of mean values of D and E: mod D₀ mod approximately=1 cm^-1, mod E₀ mod approximately=0.2 cm^-1. The short-range order is rather well preserved at Gd³⁺ sites responsible for the g approximately=6.0 features.