Measuring the static and dynamic magneto-optical constant across the entire M-edge in a reflection geometry using polarization scanning

The off diagonal components of the dielectric permittivity tensor ($\epsilon_{xy}$) provide a critical link between the microscopic band structure of a ferromagnetic material and its measured magneto-optical response. However, access to the full $\epsilon_{xy}$ of a material in the extreme ultraviolet (EUV) region spanning the M shell absorption edges has remained limited due to the difficulty in analyzing the polarization of EUV light. In this work, we present a new all-optical EUV technique that allows us to measure the $\epsilon_{xy}$ tensor across the M shell absorption edges of a ferromagnet using a table-top high harmonic EUV system. When combined with recent advances in laser-driven high harmonic sources, this technique is also capable of capturing the dynamically-changing $\epsilon_{xy}$, and thus the evolving far from equilibrium band structure across the entire M-shell absorption edge of a material, with femtosecond time resolution[1]. [1]Nature Comm. 7, 12902 (2016)