PRESSURE-INDUCED CROSSOVER FROM LONG-TO SHORT-RANGE ORDER IN COMPOSITIONALLY DISORDERED SOFT MODE FERROELECTRICS

Results on a lanthanum-modified, lead zirconate-titanate have revealed (1) pressure-induced crossover from normal ferroelectric- (nFE-) to-r elaxer (R) behavior; (2) the continuous evolution of the dynamics of t he relaxation process; (3) a spontaneous R-to-nFE transition at a temp erature well below the dynamic glass temperature of the R phase; and ( 4) the vanishing of this transition with pressure at a critical point. These results can be understood in terms of a large decrease in the c orrelation radius among polar nanodomains-a unique property of soft fe rroelectric phonon mode systems.