PINNING OF DISLOCATION-MOTION IN BCE SOLID HE-3

Mr, have measured the dissipation of dislocation motion in bcc solid H e-3 using the high-Q torsional oscillator technique at 1079 Hz. We obs erved a broad maximum in the temperature dependence of the dissipation . The maximum of the dissipation can be explained by the theory of Gra nato and Lucke in which the dislocation mobility depends upon the inte ractions of dislocations with point defects. He-4 impurities tend to b ind to the dislocation lines at low temperatures and pin this dislocat ion motion. The maximum of the dissipation corresponds to the depinnin g of the dislocation motion. From the amplitude dependence of the depi nning temperature vie first obtained the activation energy of 1.03 K o f the impurity 4He atom trapped on the dislocations in bce solid 3He a t a molar volume of 24.30 cm(3)/mol. The activation energy of the impu rity atom in bce 3He was found to be larger than the value of 0.7 K in hcp He-4.