Absence of true critical exponents in relaxor ferroelectrics: the case for defect dynamics

Scott, J. F. (2006) Absence of true critical exponents in relaxor ferroelectrics: the case for defect dynamics. Journal of Physics-Condensed Matter, 18 (31). pp. 7123-7134. DOI 10.1088/0953-8984/18/31/007

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Abstract

It is argued that the large discrepancy (× 2 in strontium barium niobate SBN) between experimental values from different kinds of experiment for the critical exponent β describing the temperature evolution of the order parameter in relaxors such as SBN arises from the fact that such ferroelectric systems, assumed to be [3D] random field Ising models by Kleemann et al (2002 Europhys. Lett. 57 14), are not in thermal equilibrium. These arguments are illustrated primarily in SBN61—SrxBa1−xNb2O6:Ce with x = 0.61 and Ce = ca. 0.7%. An alternative model of Levanyuk and Sigov for defect-dominated dynamics is invoked. The inferred dimensionality of domain walls is also addressed, and the possibility of a d = 5/2 universality class controlled by domain dimensionality is considered as an alternative to defect dynamics; inter alia, four sets of d = 5/2 exponents (with β = 1/2, 1/3, and 1/4) satisfy all known scaling and hyperscaling equalities. The present results support the scepticism about SBN critical exponents emphasized by Chao et al (2005 Phys. Rev. B 72 134105).

Item Type:	Article
Uncontrolled Keywords:	2006 AREP IA52 2006 P
Subjects:	03 - Mineral Sciences
Divisions:	03 - Mineral Sciences
Journal or Publication Title:	Journal of Physics-Condensed Matter
Volume:	18
Page Range:	pp. 7123-7134
Identification Number:	10.1088/0953-8984/18/31/007
Depositing User:	Sarah Humbert
Date Deposited:	16 Feb 2009 13:03
Last Modified:	23 Jul 2013 10:08
URI:	http://eprints.esc.cam.ac.uk/id/eprint/665

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