Deuteron magnetic resonance and relaxation study of the pseudo-one-dimensional ferroelectric transition in CsD2PO4

The deuteron quadrupole coupling tensors and spin-lattice relaxation rates $T_1^{-1\mathrm{}}$ have been determined as a function of temperature both in the paraelectric and in the ferroelectric phase of Cs${\mathrm{D}}_2$P${\mathrm{O}}_4$. The results demonstrate the order-disorder nature of the transition and show the presence of dynamic short-range ordered clusters along the O-H(2) · · · O chains, which are responsible for the H(2) deuteron $T_1^{-1\mathrm{}}$. The noninteracting H(2) deuteron intrabond jump time equals 0.9 × ${10}^{-12\mathrm{}}$ s, and is of the same order as in K${\mathrm{D}}_2$P${\mathrm{O}}_4$. The anomalously short values of both the H(1) and the H(2) deuteron $T_1$ are the result of an "anisotropy slowing down" of the order-parameter fluctuations due to the pseudo-one-dimensional nature of the transition.