Anomaly of the Internal Friction in the Helium Crystals Grown in the Burst-like Growth Mode

The internal friction in the crystals grown in two modes, namely, slow and anomalously fast (burst-like growth) modes, is measured in the temperature range 0.49-0.75K at a frequency of about 75kHz. An additional contribution to the damping decrement and softening of the dynamic modulus are detected, and their relaxation to equilibrium values at a time constant of about 3ms is observed. Possible origins of this effect are discussed.