Neutron and x-ray diffraction study of cubic [111] field-cooled Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3}
- Department of Physics and Astronomy, Johns Hopkins University, Baltimore, Maryland 21218 (United States)
- Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973 (United States)
- NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States)
- Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201800 (China)
- Department of Materials Science and Engineering, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061 (United States)
- Physics Department, Brookhaven National Laboratory, Upton, New York 11973 (United States)
Neutron and x-ray diffraction techniques have been used to study the competing long- and short-range polar order in the relaxor ferroelectric Pb(Mg{sub 1/3}Nb{sub 2/3})O{sub 3} (PMN) under a [111] applied electric field. Despite reports of a structural transition from a cubic phase to a rhombohedral phase for fields E>1.7 kV/cm, we find that the bulk unit cell remains cubic (within a sensitivity of 90 deg. -{alpha}=0.03 deg.) for fields up to 8 kV/cm. Furthermore, we observe a structural transition confined to the near surface volume or 'skin' of the crystal where the cubic cell is transformed to a rhombohedral unit cell at T{sub c}=210 K for E>4 kV/cm, for which 90 deg. -{alpha}=0.08{+-}0.03 deg. below 50 K. While the bulk unit cell remains cubic, a suppression of the diffuse scattering and concomitant enhancement of the Bragg peak intensity is observed below T{sub c}=210 K, indicating a more ordered structure with increasing electric field yet an absence of a long-range ferroelectric ground state in the bulk. The electric field strength has little effect on the diffuse scattering above T{sub c}, however, below T{sub c} the diffuse scattering is reduced in intensity and adopts an asymmetric line shape in reciprocal space. The absence of hysteresis in our neutron measurements (on the bulk) and the presence of two distinct temperature scales suggests that the ground state of PMN is not a frozen glassy phase as suggested by some theories but is better understood in terms of random fields introduced through the presence of structural disorder. Based on these results, we also suggest that PMN represents an extreme example of the two-length scale problem, and that the presence of a distinct skin may be necessary for a relaxor ground state.
- OSTI ID:
- 21055114
- Journal Information:
- Physical Review. B, Condensed Matter and Materials Physics, Vol. 76, Issue 6; Other Information: DOI: 10.1103/PhysRevB.76.064122; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 1098-0121
- Country of Publication:
- United States
- Language:
- English
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