Relaxation process in the incommensurate phase of NaNO₂

Abstract

The time evolution of the dielectric constant ϵ of NaNO₂ after a stepwise temperature change in the incommensurate (IC) phase consists of a quick response occurring at the instant of the temperature change, and a slow relaxation which proceeds taking a few hundred seconds. Also, in the IC phase, the response of ϵ to a 1 Hz ac temperature oscillation disagrees with what is expected from the temperature dependence of the thermal equilibrium value of ϵ. These results are discussed with a phenomenological theory developed by A. P. Levanyuk and the present authors. The theory explains the observed data well, if we ascribe the slow relaxation to that of IC modulation wavevector.