Electron paramagnetic resonance and optical absorption spectra of Cr3+ ions in fluorophosphate glasses

Electron paramagnetic resonance and optical absorption studies of Cr3+ ions in fluorophosphate glasses have been carried out at room and low temperatures. The EPR spectra exhibit two resonances at g approximate to 4.67 and g approximate to 2.0. These resonances are attributed to isolated Cr3+ ions and exchange coupled Cr3+ pairs respectively. The EPR spectra were also studied at various low temperatures. The numbers of spins are found to be increasing with decreasing temperature. For the first time, the magnetic susceptibility chi was calculated from the EPR data It was also observed that as temperature decreases chi increases in accordance with Curie's law. The line width of the g approximate to 2.0 resonance was found to be decreasing with increasing temperature which confirms the pairing mechanism between Cr3+ ions. The exchange coupling constant J between Cr3+ ions was calculated from the relative intensities of g approximate to 2.0 resonance line at various temperatures. The optical absorption spectrum exhibits four bands, characteristic of Cr3+ ions in octahedral symmetry. The crystal held parameter Dq and the Racah interelectronic repulsion parameters B and C were evaluated.