College Park, Maryland June 6 - 10 , 2004
M3-C3 (2:15 PM): Neutron Diffuse Scattering from Relaxor Ferroelectrics
P. M. Gehring (National Institute of Standards and Technology), K. Ohwada (Japan Atomic Energy Research Institute, Synchrotron Radiation Research Center (at SPring 8)), H. Hiraka (Tohoku University, Institute for Materials Research; Physics Department, Brookhaven National Laboratory), G. Y. Xu (Physics Department, Brookhaven National Laboratory), S. H. Lee (National Institute of Standards and Technology), G. Shirane (Physics Department, Brookhaven National Laboratory)
We report measurements of the neutron diffuse scattering from a single crystal of the relaxor ferroelectric PbZn1/3Nb2/3O3 doped with 8% PbTiO3 (PZN-8%PT) for temperatures 100 K < T < 530 K and electric fields 0 kV/cm < E < 10 kV/cm. The diffuse scattering transverse to the (003) Bragg peak is strongly suppressed in the tetragonal phase at 400K for E = 2 kV/cm applied along the  direction. Surprisingly, no change is observed in the diffuse scattering measured transverse to (300), even for field strengths up to 10 kV/cm. Thus the application of an external electric field in the tetragonal (ferroelectric) phase of PZN-8%PT does not produce a uniformly polarized state. This result can be understood within the context of the Hirota model of displaced or phase-shifted polar nanoregions. We also report cold neutron measurements of the diffuse scattering in PbMg1/3Nb2/3O3 the small-q region near the (110) Brillouin zone center between 100 K and the Burns temperature Td (~ 620 K). A strong quasielastic component of the diffuse scattering cross section is seen near 400 K. The reciprocal space geometry of the diffuse scattering cross section measured near (100) and (110) at 100 K changes dramatically at higher temperatures, which we believe reflects the underlying chemical short range order present above Td.
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