Dynamics of random-site interacting dipoles in (K-Na)TaO₃

Abstract

From ²³Na quadrupole relaxation times and dielectric dispersion measurements, insight into the dynamics of the off-center Na dipoles is obtained. Below ∼150 K, the onset of low-frequency relaxational dynamics is detected, with a wide distribution of the dipolar frequencies. The polar phase appears from an apparent freeze-out of the hopping motion of the dipoles; their hopping rates remain greater than about 1 kHz down to 4 K. The relaxation dynamics observed at 4 K is of resonant character, possibly related to a classical-quantum crossover.