Dielectric relaxation in pseudo-one-dimensional ferroelectric CsD2PO4

Dielectric dispersion in pseudo-one-dimensional hydrogen-bonded ferroelectric Cs${\mathrm{D}}_2$P${\mathrm{O}}_4$ was measured in the frequency range from 100 kHz to 2 GHz for temperatures between -13 and 30°C. The observed relaxation is monodispersive in the paraelectric phase, except in the vicinity of the transition. The static dielectric constant ${\epsilon }_s$ shows classical critical behavior, with the critical coefficient $\gamma =1\mathrm{}$. The relaxation frequency $f_{\epsilon }$ is much lower than in corresponding three-dimensional systems and exhibits a pronounced critical slowing down with a nonclassical exponent of 1.3. Outside the critical region in the paraelectric phase, $\epsilon$ and $f_{\epsilon }$ can be described reasonably well by a pseudo-one-dimensional Ising model, treating the interchain interactions in the mean-field approximation. The intrachain and interchain interactions obtained agree well with previously determined values. The noninteracting deuteron intrabond-jump time is much smaller than in K${\mathrm{D}}_2$P${\mathrm{O}}_4$ but has the same activation energy.