Many magnetic equilibrium states and phase transitions are characterized by fluctuations. Such magnetic fluctuation can, in principle, be detected with scattering-based x-ray photon correlation spectroscopy (XPCS). However, in the established approach of XPCS, the magnetic scattering signal is quadratic in the magnetic scattering cross section, which results not only in often prohibitively small signals but also in a fundamental inability to detect negative correlations (anticorrelations). Here, we propose to exploit the possibility of heterodyne mixing of the magnetic signal with static charge scattering to reconstruct the first-order (linear) magnetic correlation function. We show that the first-order magnetic scattering signal reconstructed from heterodyne scattering now directly represents the underlying magnetization texture. Moreover, we suggest a practical implementation based on an absorption mask rigidly connected to the sample, which not only produces a static charge scattering signal but also eliminates the problem of drift-induced artificial decay of the correlation functions. Our method thereby significantly broadens the range of scientific questions accessible by magnetic x-ray photon correlation spectroscopy.

中文翻译：

---

基于软X射线磁圆二色性的外差混合光子相关光谱

许多磁平衡状态和相变都以波动为特征。这种磁波动原则上可以用基于散射的 X 射线光子相关光谱 (XPCS) 来检测。然而，在 XPCS 的既定方法中，磁散射信号在磁散射截面中是二次的，这不仅导致通常非常小的信号，而且还导致根本无法检测到负相关（反相关）。在这里，我们建议利用磁信号与静电荷散射的外差混合的可能性来重建一阶（线性）磁相关函数。我们表明，从外差散射重建的一阶磁散射信号现在直接代表了潜在的磁化纹理。而且，我们建议一种基于与样品刚性连接的吸收掩模的实际实施方案，它不仅产生静电荷散射信号，而且消除了漂移引起的相关函数人为衰减的问题。因此，我们的方法显着拓宽了可通过磁 X 射线光子相关光谱分析的科学问题的范围。