Fitting IGM, FGM and NLS switching models to NaNO2-PVA composite transients for its microscopic parameter estimation

Abstract

Domain switching process is a complex process and is not as simple in occurrence as appears from conceptual framework. Fortunately, the theories of nucleation and crystal growth successfully applied to switching domains help in understanding switching kinetics in ferroelectric samples. Direct methods of parameter estimation can provide only the local information of the target region while the ‘universal integrating methods’ provide domain kinetic parameters with their response proportional to the fraction of the phase grown at that time. Besides being statistical, the later is much simpler and popular in delivering more credible results. In this paper, an indirect estimation of significant microscopic parameters of optimized NaNO2-PVA ferroelectric composites is made by fitting their current transients with IGM, FGM and NLS switching models The fitting of these models into the experimental switching transient helps (i) in finding dimensionalityn, characteristic timeto, nucleation rate R and domain size L and (ii) to identify whether a thin film can be considered to be an ensemble of a number of independent elementary regions switching their states independently with exponential distribution of their relaxation times. IGM model suggests that polarization switching proceeds through a continuous nucleation process. The results of FGM fitting the transients supports the points that with increase in signal-amplitude, new regions are nucleated leading to reduction of adjacent relative distance between the domains The excellent NLS fit over whole range of switching times suggests that composite film can be considered an ensemble of elementary regions individually characterized by independent relaxation times.