Neutron diffuse scattering from polar nanoregions in the relaxor Pb(Mg1/3Nb2/3)O3 -: art. no. 104105
被引:167
作者:
Hirota, K
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机构:
Brookhaven Natl Lab, Dept Phys, Upton, NY 11973 USABrookhaven Natl Lab, Dept Phys, Upton, NY 11973 USA
Hirota, K
[1
]
Ye, ZG
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机构:Brookhaven Natl Lab, Dept Phys, Upton, NY 11973 USA
Ye, ZG
Wakimoto, S
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机构:Brookhaven Natl Lab, Dept Phys, Upton, NY 11973 USA
Wakimoto, S
Gehring, PM
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机构:Brookhaven Natl Lab, Dept Phys, Upton, NY 11973 USA
Gehring, PM
Shirane, G
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机构:Brookhaven Natl Lab, Dept Phys, Upton, NY 11973 USA
Shirane, G
机构:
[1] Brookhaven Natl Lab, Dept Phys, Upton, NY 11973 USA
[2] Tohoku Univ, Dept Phys, Sendai, Miyagi 9808578, Japan
[3] Simon Fraser Univ, Dept Chem, Burnaby, BC V5A 1S6, Canada
[4] Univ Toronto, Dept Phys, Toronto, ON M5S 1A7, Canada
[5] Natl Inst Stand & Technol, Ctr Neutron Res, Gaithersburg, MD 20899 USA
来源:
PHYSICAL REVIEW B
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2002年
/
65卷
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10期
关键词:
D O I:
10.1103/PhysRevB.65.104105
中图分类号:
T [工业技术];
学科分类号:
08 ;
摘要:
We have studied the diffuse scattering in the relaxor Pb(Mg1/3Nb2/3)O-3 (PMN) using triple-axis neutron scattering techniques. The diffuse scattering first appears around the Burns temperature T(d)approximate to620 K, indicating that its origin lies within the polar nanoregions (PNR's). While the relative intensities of the diffuse scattering around (101), (200), and (300) are consistent with those previously reported by Vakhrushev et al., they are, surprisingly, entirely different from those of the lowest-energy transverse-optic (TO) phonon. This observation led Naberezhnov et al. to claim that this TO mode could not be the ferroelectric soft mode. However, a recent neutron study by Gehring et al. has unambiguously shown that the lowest-energy TO mode does soften on cooling and that the relative intensities are similar to those of PbTiO3. If the diffuse scattering in PMN originates from the condensation of a soft TO mode, then the atomic displacements of the PNR must satisfy the center-of-mass condition. But, the atomic displacements determined from diffuse scattering intensities do not fulfill this condition. To resolve this contradiction, we propose a simple model in which the total atomic displacement consists of two components delta(c.m.) and delta(shift). Here delta(c.m.) is created by the soft-mode condensation and thus satisfies the center-of-mass condition. On the other hand, delta(shift) represents a uniform displacement of the PNR's along their polar direction relative to the surrounding (unpolarized) cubic matrix. Within the framework of this model, we can successfully describe the neutron diffuse scattering intensities observed in PMN.