From mesoscopic to global polar order in the uniaxial relaxor ferroelectric Sr0.8Ba0.2Nb2O6

In the relaxor ferroelectric Sr0.8Ba0.2Nb2O6 (SBN80) the relaxation of polar nanoregions (PNRs) reveals an anisotropic breathing mode when approaching the transition temperature, T-C approximate to 289 K, on cooling. Two distinct dispersion steps and peaks, respectively, of the complex susceptibility components in the milli- and megahertz frequency range reflect their large length-to-width aspect ratio. Below T-C power-law frequency dispersion characterizes the creep motion of the emerging ferroelectric domain walls and the fractal dimension D approximate to 2 of their contour lines. Piezoforce micrographs reveal nanometric jagged domains in accordance with the large disorder and random field magnitude in the extreme relaxor SBN80. (C) 2012 American Institute of Physics. [doi:10.1063/1.3680599]