ToF Inelastic Neutron Scattering Studies on Quantum Spin Systems (CuCl)LaB2O7 (B=Nb, Ta)
ToF Inelastic Neutron Scattering Studies on Quantum Spin Systems (CuCl)LaB2O7 (B=Nb, Ta)
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量子自旋系统 (CuCl)LaB2O7 (B=Nb, Ta) 的 ToF 非弹性中子散射研究
DOI：
10.1088/1742-6596/320/1/012037
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
et al
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文献类型：
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作者：
S.Ohira-Kawamura;et al
利用飞行时间(ToF)非弹性中子散射技术研究了量子自旋体系(CuCl) LaB 2 O 7 (B= Nb, Ta)中的磁激发。(CuCl) LaNb 2 O 7 表现出自旋单线基态，激发间隙为ΔE∼ 2.3 meV，而(CuCl) LaTa 2 O 7 表现出低于T的反铁磁(AFM)有序性。 N= 7 K。在(CuCl) LaNb 2 O 7 中，在ΔE～2 meV处观察到能量宽度为～1 meV的带状激发。该系统的散射矢量 Q 的大小与 ΔE∼2 meV 附近的磁激发积分强度的相关性很好地再现了三轴光谱仪观察到的情况，表明具有自旋单峰特征。激发光谱显示了沿 Q 方向激发强度和 ΔE 峰值位置的调制，这表明形成单线态的自旋对不是简单地孤立的，而是具有一定的相互作用。使用孤立的二聚体模型以及之前的研究，调制的特征是长度~ 8.7 Å，对应于第四邻域距离。AFM 状态下的(CuCl) LaTa 2 O 7 在激发光谱中也显示出调制行为。然而，积分强度表现出不同的 Q 依赖性，反映了不同的基态。
Magnetic excitations in quantum spin system (CuCl) LaB 2 O 7 (B= Nb, Ta) have been studied by the time-of-flight (ToF) inelastic neutron scattering technique.(CuCl) LaNb 2 O 7 exhibits a spin-singlet ground state with an excitation gap of ΔE∼ 2.3 meV, while (CuCl) LaTa 2 O 7 exhibits an antiferromagnetic (AFM) ordering below T N= 7 K. In (CuCl) LaNb 2 O 7, a band-like excitation with an energy width of∼ 1 meV was observed at ΔE∼ 2 meV. The magnitude of scattering vector Q dependence of the integrated intensity of the magnetic excitation around ΔE∼ 2 meV for this system well reproduces that observed by a triple-axis spectrometer, indicating a spin-singlet feature. The excitation spectra show modulations for both the intensity of excitation and the peak position in ΔE along the Q direction, which indicates that spin pairs forming a singlet state are not simply isolated but have some interaction. Using the isolated dimer model as well as the previous study, the modulation is characterized by a length∼ 8.7 Å, which corresponds to the fourth-neighbor distance.(CuCl) LaTa 2 O 7 in the AFM state also shows modulating behaviour in the excitation spectra. However, the integrated intensity exhibits a different Q dependence, reflecting a different ground state.