Isotope effects in Rochelle salt

Isotope effects on deuteration both in the static and dynamical behaviour of Rochelle salt are theoretically investigated on the basis of a two-sublattice Ising model with asymmetric double-well potential. Spontaneous polarization and static dielectric constant are numerically calculated for several values of the tunnelling integral. The dynamical susceptibility is derived from a Bloch-type equation, and the shifts of the relaxation times are calculated from this equation. The notable difference in the dynamical behaviour between Rochelle salt and KDP-type ferroelectrics is also discussed.