A physical mechanism for the freezing of polar nanoregions (PNRs) in relaxor ferroelectrics is presented. Assuming that the activation energy for the reorientation of a cluster of PNRs scales with the mean volume of the cluster, the characteristic relaxation time τ is found to diverge as the cluster volume reaches the percolation limit. Applying the mean field theory of continuum percolation, the familiar Vogel-Fulcher equation for the temperature dependence of τ is derived.
Cite
@article{arxiv.0705.3732,
title = {Vogel-Fulcher freezing in relaxor ferroelectrics},
author = {R. Pirc and R. Blinc},
journal= {arXiv preprint arXiv:0705.3732},
year = {2009}
}