Phonon contribution to the hyperfine coupling constant

Abstract

The temperature dependence of the hyperfine coupling constant A ( T ) of Mn2+ in MgO is analysed by means of the generalized phonon theory, obtained by treating the phonon wavelength without approximation over the entire phonon spectrum. A comparison is also made of the results obtained with both the generalized and the long-wavelength models as applied to A ( T) for Mn2+ and Eu2+ in the alkaline earth fluoride crystals. This comparison suggests that local mode effects and not covalency may be the dominant mechanism required to improve the theoretical fit to the data. Contributions from optical phonons to A ( T) of Mn2+ and Eu2+ in MgO, CaFz , SrF, , and BaF, crystals are also tabulated and discussed.