DYNAMIC ORBIT-LATTICE INTERACTIONS FOR PBF2-GD3+ SINGLE-CRYSTALS

Temperature dependence of the second-order spin-lattice coefficients for PbF2:Gd3+ is reported. It is shown that the thermal expansion of the crystal lattice contributes only in about 14% to the observed dependence and the rest should be ascribed to a dynamic coupling between the 4f7 electrons and lattice vibrations. The results are parametrized in both the Einstein and the Debye models and it is shown that the phenomenological parameters obtained from such parametrization can be made to coincide in both models if a specific value of the Einstein frequency omega-E is properly chosen. Both models of parameterization show that the GAMMA-3g vibrating mode couples to the 4f7 electrons much weaker than the GAMMA-5g one.