Diffuse scattering studies on polar-nanoregions in PMN-xPT relaxor ferroelectrics

PZN-xPT and PMN-xPT relaxor ferroelectric materials have been studied extensively due to their extraordinary piezoelectric and electromechanical responses. One of the key issues in these materials is the role of polar nano-regions (PNR), or, in other words, how the short-range orders coexist with long-range polar order and influence the bulk property. We have performed neutron scattering measurements on single crystal PZN-xPT and PMN-xPT samples. With elastic diffuse scattering measurements carried out under external field along different directions, we were able to monitor how the dominant part of the diffuse scattering - the "butterfly diffuse" that extends along <110> directions - change with field. Our observation was a complete redistribution (of the diffuse scattering intensities) under [111] field, a partial redistribution under [110] field, and no major change under [001] field. Our results suggest that the polar nano-regions are robust local orders that are locked in within the surrounding polar environment below Tc, and also strongly interact with acoustic phonon modes that induces instability in these systems.