It was argued that a factor-of-2 discrepancy, between the values obtained by using differing types of measurement of the critical exponent which described the temperature evolution of the order parameter in such relaxors, arose from the fact that such ferro-electric systems (assumed to be 3-dimensional random-field Ising models by Kleemann et al. 2002), were not in thermal equilibrium. This was illustrated mainly for Ce-doped SrxBa1-xNb2O6, with x = 0.61 and about 0.7%Ce. The Levanyuk-Sigov model for defect-dominated dynamics was used. The apparent dimensionality of the domain walls was also considered, and the possibility of a d = 5/2 universality class controlled by domain dimensionality was considered to be an alternative to defect dynamics. Inter alia, 4 sets of d = 5/2 exponents (with β = 1/2, 1/3 and 1/4) were found to satisfy all known scaling and hyper-scaling equalities. The present results supported the skepticism, concerning Nb2(Sr,Ba)O6 critical exponents, which had been expressed (Chao et al., 2005).

Absence of True Critical Exponents in Relaxor Ferroelectrics - the Case for Defect Dynamics. J.F.Scott: Journal of Physics - Condensed Matter, 2006, 18[31] 7123-34