ANOMALOUS BEHAVIOR OF THE ZENER RELAXATION IN CU-AU

Measurements of the Zener relaxation in single crystals of Cu-18at.%Au and Cu3Au are presented. In the 18at.% alloy only one internal fricti on peak is observed at low frequencies (of the order of 1 Hz). This pe ak is only slightly wider than a Debye's peak. An additional hump appe ars at intermediate frequencies (of the order of 60 Hz). The Zener pea k in the Cu3Au alloy is accompanied by an additional maximum produced by the order-disorder transition. A measurement of the derivative of t he damping with respect to the frequency through the use of a pendulum with variable moment of inertia shows that non-linear effects are pre sent in the Zener relaxation in both alloys.