弱耦合三角自旋管 CsCrF$_4$ 中的非弹性中子散射
Inelastic Neutron Scattering in Weakly Coupled Triangular Spin Tubes CsCrF$_4$
AI总结：
本文通过非弹性中子散射实验测量了 CsCrF$_4$ 的自旋动力学，发现其自旋哈密顿量不随温度变化，揭示了其连续相变源于无序致序机制。
摘要：
我们进行了非弹性中子散射（INS）实验，以测量自旋管候选材料 CsCrF$_4$ 多晶样品的自旋动力学。该化合物表现出连续相变，从顺磁相经过具有 120$^{\circ}$ 结构的中间温度（IT）相，转变为具有另一种 120$^{\circ}$ 结构的低温（LT）相。通过将 LT 相中观察到的中子谱与计算谱进行详细比较，揭示出自旋哈密顿量可被识别为反铁磁自旋管，其中包含管间相互作用、Dzyaloshinskii-Moriya 相互作用和单离子各向异性的微扰项。经典计算了基态的相图。从 LT 相测量的 INS 谱中获得的自旋哈密顿量参数组，非常接近 IT 相 120$^{\circ}$ 结构相的边界。令人惊讶的是，在粉末平均谱水平上，IT 相中测量的 INS 谱与 LT 相中的谱相同，尽管 IT 和 LT 相中的磁结构不同。观察到了与两种不同静态结构相容的相同动力学结构。观察谱没有差异表明自旋哈密顿量不随温度变化，暗示连续相变的起源为无序致序机制。
英文摘要：
We performed inelastic neutron scattering (INS) experiments to measure spin dynamics on a polycrystalline sample of a spin tube candidate CsCrF$_{4}$. The compound exhibits a successive phase transition from a paramagnetic phase through an intermediate temperature (IT) phase of a 120$^{\circ}$ structure to a low temperature (LT) phase of another 120$^{\circ}$ structure. Elaborate comparison between observed and calculated neutron spectra in LT phase reveals that the spin Hamiltonian is identified as antiferromagnetic spin tubes including perturbative terms of intertube interaction, Dzyaloshinskii-Moriya interaction, and single ion anisotropy. A phase diagram for the ground state is classically calculated. A set of parameters in the spin Hamiltonian obtained from the INS spectra measured in LT phase is quite close to a boundary to the phase of the 120$^{\circ}$ structure of IT phase. The INS spectra measured in IT phase is, surprisingly, the same as those in LT phase in the level of powder averaged spectra, even though the magnetic structures in IT and LT phases are different. Identical dynamical structures compatible with two different static structures are observed. No difference in the observed spectra indicates no change of the spin Hamiltonian with the temperature, suggesting that the origin of the successive phase transition being order-by-disorder mechanism.
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