Photon correlation spectroscopy with heterodyne mixing based on soft x-ray magnetic circular dichroism

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