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 $T_c$ and are effectively frozen in at one of the two possible sites below $T_c$ . 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 $T_c$ , but cannot distinguish between a pure relaxational and an overdamped resonant mode.