Anomaly of the internal friction in helium-4 crystals prepared with the burst-like growth method

The internal friction is measured in the ⁴He crystals prepared with the conventional and burst-like methods at temperature 0.65 K and frequency 75 kHz. It is observed that the crystals, grown too rapidly, have an excess damping and smaller dynamic elastic modulus. The magnitude of the effect enhances as the initial overpressure increases. The contribution to the excess damping vanishes at the critical overpressure 3.5 mbar separating the regions of the normal and anomalous crystal growth at the corresponding temperature. Corrections to the modulus and decrement relax with the time constant of about 3 ms. The regime of the burst-like growth may result in the crystals with the internal state different from that of equilibrium crystals.