Soft X-ray nanospectroscopy for quantification of X-ray linear dichroism on powders,Journal of Synchrotron Radiation

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Soft X-ray nanospectroscopy for quantification of X-ray linear dichroism on powders
Journal of Synchrotron Radiation ( IF 2.4 ) Pub Date : 2021-05-19 , DOI: 10.1107/s1600577521004021
Selwin Hageraats ₁ , Mathieu Thoury ₂ , Stefan Stanescu ₃ , Katrien Keune ₁

Affiliation

X-ray linear dichroism (XLD) is a fundamental property of many ordered materials that can for instance provide information on the origin of magnetic properties and the existence of differently ordered domains. Conventionally, measurements of XLD are performed on single crystals, crystalline thin films, or highly ordered nanostructure arrays. Here, it is demonstrated how quantitative measurements of XLD can be performed on powders, relying on the random orientation of many particles instead of the controlled orientation of a single ordered structure. The technique is based on a scanning X-ray transmission microscope operated in the soft X-ray regime. The use of a Fresnel zone plate allows X-ray absorption features to be probed at ∼40 nm lateral resolution – a scale small enough to probe the individual crystallites in most powders. Quantitative XLD parameters were then retrieved by determining the intensity distributions of certain diagnostic dichroic absorption features, estimating the angle between their transition dipole moments, and fitting the distributions with four-parameter dichroic models. Analysis of several differently produced ZnO powders shows that the experimentally obtained distributions indeed follow the theoretical model for XLD. Making use of Monte Carlo simulations to estimate uncertainties in the calculated dichroic model parameters, it was established that longer X-ray exposure times lead to a decrease in the amplitude of the XLD effect of ZnO.

中文翻译：

用于定量粉末 X 射线线性二色性的软 X 射线纳米光谱

X 射线线性二色性 (XLD) 是许多有序材料的基本特性，例如可以提供有关磁特性起源和不同有序域是否存在的信息。传统上，XLD 的测量是在单晶、晶体薄膜或高度有序的纳米结构阵列上进行的。在这里，演示了如何依赖许多颗粒的随机方向而不是单一有序结构的受控方向对粉末进行 XLD 的定量测量。该技术基于在软 X 射线范围内操作的扫描 X 射线透射显微镜。使用菲涅尔波带板可以以约 40 nm 的横向分辨率探测 X 射线吸收特征，该分辨率足够小，可以探测大多数粉末中的单个微晶。然后通过确定某些诊断二向色吸收特征的强度分布、估计其跃迁偶极矩之间的角度以及用四参数二向色模型拟合分布来检索定量 XLD 参数。对几种不同生产的 ZnO 粉末的分析表明，实验获得的分布确实遵循 XLD 的理论模型。利用蒙特卡罗模拟来估计计算的二向色模型参数的不确定性，确定较长的 X 射线曝光时间会导致 ZnO 的 XLD 效应幅度减小。

更新日期：2021-07-24

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