ESR of Exchange Coupled Cr3+ Ions in Phosphate Glass

Abstract

A study of the ESR spectrum of a phosphate glass heavily doped with Cr2O3 is reported. The spectrum is attributed to exchange coupled Cr3+ ion pairs and is interpreted with reference to a spin Hamiltonian containing isotropic exchange, Zeeman, and fine structure terms. From the temperature dependence of the ESR intensity, it is inferred that the coupling is antiferromagnetic with an average coupling constant J=24±2 cm−1. The effects of fine structure interactions on the lineshape and breadth of the glass spectrum are considered, and the magnitudes of the fine structure parameters are estimated from the observed linewidths and dependence of the lineshape on microwave frequency. It is found that the fine structure constants are distributed in the range from 0.03 to 0.3 cm−1. The majority of the pairs are characterized by values near the lower end of the range, but the higher values are required to account for the absorption in the wings of the line.