Phonon softening and dispersion in EuTiO3

Article

关键词: NEUTRON-SCATTERING;    STRONTIUM-TITANATE;    MAGNETIC-STRUCTURE;    PHASE-TRANSITION;    MODES;    BEAMLINE;    BEHAVIOR;    SRTIO3;   

DOI  :  10.1103/PhysRevB.86.220301

来源: SCIE

【 摘 要 】

We measured phonon dispersion in single-crystal EuTiO3 using inelastic x-ray scattering. Astructural transition to an antiferrodistortive phase was found at a critical temperature T-0 = 287 +/- 1K using powder and single-crystal x-ray diffraction. Clear softening of the zone boundary R-point q = (0.5 0.5 0.5) acoustic phonon shows this to be a displacive transition. The mode energy plotted against reduced temperature could be seen to nearly overlap that of SrTiO3, suggesting a universal scaling relation. Phonon dispersion was measured along Gamma-X (0 0 0) -> (0.5 0 0). Mode eigenvectors were obtained from a shell model consistent with the q dependence of intensity and energy, which also showed that the dispersion is nominally the same as in SrTiO3 at room temperature, but corrected for mass. The lowest-energy optical mode, determined to be of Slater character, softens approximately linearly with temperature until the 70-100 K range where the softening stops, and at low temperature, the mode disperses linearly near the zone center.

【 授权许可】

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