The elastic shear constant and the internal friction of three mixed crystals ${\left(\mathrm{KBr}\right)}_{1-x}{\left(\mathrm{KCN}\right)}_x$ have been determined from the resonance of a torsion pendulum in the ${10}^2$-Hz range. Two glass-forming samples ($x=0.20,0.50\mathrm{}$) and one sample ($x=0.75\mathrm{}$) which orders ferroelastically have been investigated. Two regimes of loss have been observed; the primary one is related to domain-wall motion, the secondary one to dipolar reorientations.

• Received 31 March 1986

DOI:https://doi.org/10.1103/PhysRevLett.57.2544