Low-temperature heat capacity of alkaline-earth fluorides: SrF2, BaF2

The heat capacities of SrF 2 and BaF 2 have been measured from 1.7K to 40K. Values of 381.7+or-1.0K (SrF 2 ) and 286.6+or-1K (BaF 2 ) obtained for the limiting Debye temperature, theta 0 c , agree with values, theta 0 el , calculated from elastic stiffness moduli. The heat capacity and Debye temperature, theta (T), for both compounds are calculated as a function of temperature using measurements of the density of states of the lattice vibrational spectrum. Good agreement is obtained with theta c (T) deduced from the heat capacity measurements, showing that variations in theta c (T) may be completely accounted for by lattice dispersion.