论文标题
非校准和订购的RBFE $^{2+} $ fe $^{3+} $ f $ _ {6} $中的激发横向和振幅波动
Excitonic transverse and amplitude fluctuations in the noncollinear and charge-ordered RbFe$^{2+}$Fe$^{3+}$F$_{6}$
论文作者
论文摘要
rbfe $^{2+} $ fe $^{3+} $ f $ _ {6} $是抗fiferromagnet的一个示例，并具有contahedrally协调的fe $^{2+} $和fe $^{3+} $ ions的费用。除了不同的自旋值，Fe $^{2+} $（$ s = 2 $）和Fe $^{3+} $（$ s = {5 \ over2} $）具有不同的轨道基态，具有fe $^{2+} $具有有效的轨道变性，具有有效的眶角动量$ l = 1 $。所得的低温磁性结构与垂直于最近邻居的旋转对齐（S. W. kim \ textit {等} chem。sci。{\ bf {3}}，741（2012））。轨道变性和非共线自旋排列的组合引入了异常类型的激发类型的可能性，例如顺序参数的振幅模式。在本文中，我们通过应用多层次分析来模拟中子光谱数据（M. Songvilay \ textit {et al。}Phys。Phys。Rev.lett。{\ bf {121}}，087201（2018））。特别是，我们讨论了通过在Fe $^{2+} $站点上存在轨道自由度的振幅波动而观察到的动量和能量的可能起源。我们基于共线自旋结构扩展了先前的自旋轨道激子模型，以了解测得的低能激发，并预测和讨论RBFE $^{2+} $ fe $^{3+} $ f $ f $ _ {6} $中可能的振幅模式散射。
RbFe$^{2+}$Fe$^{3+}$F$_{6}$ is an example of an antiferromagnet with charge ordering of the octahedrally coordinated Fe$^{2+}$ and Fe$^{3+}$ ions. As well as different spin values, Fe$^{2+}$ ($S=2$) and Fe$^{3+}$ ($S={5\over2}$) possess differing orbital ground states with Fe$^{2+}$ having an orbital degeneracy with an effective orbital angular momentum of $l=1$. The resulting low temperature magnetic structure is non collinear with the spins aligned perpendicular to nearest neighbors (S. W. Kim \textit{et al.} Chem. Sci. {\bf{3}}, 741 (2012)). The combination of an orbital degeneracy and non collinear spin arrangements introduces the possibility for unusual types of excitations such as amplitude modes of the order parameter. In this paper we investigate this by applying a multi-level analysis to model neutron spectroscopy data (M. Songvilay \textit{et al.} Phys. Rev. Lett. {\bf{121}}, 087201 (2018)). In particular, we discuss the possible origins of the momentum and energy broadened continuum scattering observed in terms of amplitude fluctuations allowed through the presence of an orbital degree of freedom on the Fe$^{2+}$ site. We extend previous spin-orbit exciton models based on a collinear spin structure to understand the measured low-energy excitations and also to predict and discuss possible amplitude mode scattering in RbFe$^{2+}$Fe$^{3+}$F$_{6}$.
