Low-temperature acoustic properties of single-crystal hafnium

Five independent adiabatic elastic tensor components c ij of single-crystal Hf (0.3% Zr) have been precisely measured in the range 78–300 (c 11 and c 33) or 78–160 K (c 12, c 13, and c 44) at 50 MHz using an ultrasonic pulse technique. The corresponding linear absorption coefficients α ij (T) have been measured in the same temperature ranges. The c ij data have been used to determine adiabatic compressibilities β∥ and β⊥, and Young’s moduli E ∥ and E ⊥ along and across the c axis, respectively. Near 140 K, we have revealed an anomaly in c 33(T) due to changes in the phonon spectrum of single-crystal α-Hf. The observed anomalies in temperature-dependent α11 and α33 are tentatively attributed to grown-in dislocations.