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arXiv 1003.1666cond-mat.str-elcond-mat.mtrl-sci
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KCuF3中动态Dzyaloshinsky-Moriya相互作用:反铁畸变晶格不稳定性的Raman证据

Dynamical Dzyaloshinsky-Moriya interaction in KCuF3: Raman evidence for an antiferrodistortive lattice instability

V. Gnezdilov, J. Deisenhofer, P. Lemmens, D. Wulferding, O. Afanasiev, P. Ghigna, A. Loidl, A. Yeremenko

摘要:

在轨道有序的准一维Heisenberg反铁磁体KCuF_3中,低能Eg和B1 g声子模在室温至特征温度T_S = 50 K之间出现反常软化(25%和13%)。在此温度范围内,F离子动态位移的冻结建议发生。此外,在260 cm ~(-1)附近的Eg模在T_S以下明显分裂. T_S以上的声子线宽度遵循激活行为,激活能约为50 K。我们的观察清楚地证明了在T_S以下结构对称性的降低,并表明当T>T_S时晶格和自旋涨落的强耦合。

英文摘要:

In the orbitally ordered, quasi-one dimensional Heisenberg antiferromagnet KCuF3 the low-energy Eg and B1g phonon modes show an anomalous softening (25% and 13%) between room temperature and the characteristic temperature T_S = 50 K. In this temperature range a freezing-in of F ion dynamic displacements is proposed to occur. In addition, the Eg mode at about 260 cm-1 clearly splits below T_S. The width of the phonon lines above T_S follows an activated behavior with an activation energy of about 50 K. Our observations clearly evidence a reduction of the structural symmetry below T_S and indicate a strong coupling of lattice and spin fluctuations for T>T_S.

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