Optical absorption spectra of doped in yttrium pyrogermanate crystal

This paper reports the low temperature absorption and Zeeman spectra of doped in yttrium pyrogermanate (YPG), which were studied for the first time. In this compound the site symmetry of , or the crystal field (CF) symmetry, was found to be , as present in other rare earth pyrogermanates, and not . The spectral results were analysed by diagonalizing the total Hamiltonian consisting of the atomic (electrostatic, spin-orbit and configuration interactions) and the CF interactions, in a basis of states spanning the entire ground configuration of in the intermediate coupling formalism, including J-mixing under CF. The best fitted free ion and CF parameters obtained were and (all in ). Using these parameters the thermal characteristics of molar magnetic susceptibilities , their anisotropy and the Schottky specific heat of in YPG were calculated. It was found that the calculated values of between 300 and 152 K but on cooling further was observed, i.e. the sign of was reversed below . The calculated values of exhibited a sharp peak at 24 K and a broad maximum at 156 K. These characteristics were similar to other compounds studied earlier.