Deuteron Magnetic Resonance and Relaxation in Ferroelectric KD2PO4, KD2AsO4, and CsD2AsO4

Abstract

The temperature dependence of the quadrupole splitting of the deuteron magnetic resonance spectra of KD2AsO4 and CsD2AsO4 has been studied and the electric field gradient tensors at the deuteron sites were determined. The results show that the deuterons are—similar to those in KD2PO4—moving between the two off-center positions in the O–D···O bonds above Tc and are effectively frozen in at one of the two possible sites below Tc. The dynamics of this process was investigated by deuteron spin–lattice relaxation studies. The results show the existence of a “soft” deuteron mode which condenses at Tc, but cannot distinguish between a pure relaxational and an overdamped resonant mode.