Static Electric Susceptibility and Dielectric Relaxation Time near the Transition Points in NaNO2

Abstract

The precise temperature dependence of the ralaxation time of the polarization in NaNO 2 has been given through a new approach, in which the relaxation time is derived from the imaginary part of the complex dielectric constant in the low frequency region. On the way of this experimental procedure, it was found that the measurement of the static electric susceptibility should be made at around 1 MHz, because another dielectric dispersion occurs below this frequency. The critical index for the static susceptibility is determined as γ=1.11±0.05. Throughout the paraelectric and sinusoidal antiferroelectric phases, the temperature dependence of the relaxation time has been explained qualitatively by simple equations in molecular field approximation for the kinematical Ising model. The critical index of the kinematical slowing down is found to be positive and smaller than 0.20. This value is consistent with that expected theoretically.