Abstract
Specific heat measurements and phonon spectroscopy have been performed on some dysprosium-doped CaF2 crystals in order to evaluate the cubic crystal-field parameters, which have previously been determined from electron paramagnetic resonance (EPR) and luminescence results but not precisely enough to give the overall crystal-field effects. Specific heat results show a Schottky anomaly from which the authors determine W=1.32+or-0.14 cm-1; this parameter is very imprecise and higher than the other values because the anomaly is masked by spin-spin interactions and broadened and shifted by additional anomalies at low temperatures. Phonon spectroscopy results are however very precise and three absorption lines are observed: the high-frequency line is attributed to the cubic crystal-field transition of Dy3+ which gives W=0.975+or-0.048 cm-1, but the low-frequency lines have not yet been identified.