Anti-ferrodistortive Nanodomains in PMN Relaxor
arXiv:cond-mat/0303012 · doi:10.1063/1.1609938
Abstract
Temperature dependent studies of the 1/2(hk0) superlattice reflections αspots by synchrotron x-ray scattering measurements were performed in (PMN) and (PMN-xPT) with Ti doping x<0.32 single crystals. Separation of the αspots from the underlying diffuse scattering background allowed studying them as separate entities for the first time. Structure factor calculations have shown that alpha spots constitute the presence of a new kind of anti-ferrodistortive nanoregions (AFR) in the form of fluctuations produced by anti-parallel short-range correlated <110> Pb^2+ displacements. AFR appear to be different and unrelated to the chemical nanodomains (CND) and ferroelectric polar nanoregions (PNR). Simultaneous presence of AFR and PNR can explain relaxor behavior as a result of competition between randomly occurring ferroelectric and anti-ferroelectric fluctuations. Temperature dependence of the αspots in PMN showed a direct correlation with the freezing phase transition near Tf~220 K.
10 pages, 7 figures, Conference-Fundamental Physics of Ferroelectrics 2003