Broadband phase retardation with palladium-coated mirrors for M-edge XMCD in the 40-70  eV range

We demonstrate palladium (Pd)-coated mirrors as superior broadband phase retarders for magnetic circular dichroism (MCD) spectroscopy targeting transition metal M-edges in the 40-70 eV range than those coated with molybdenum/boron carbide (Mo/B₄C), which are current standard materials. Pd mirrors maintain smaller deviation of phase retardation across the entire range, enabling simultaneous investigation of Cr, Mn, Fe, Co, and Ni within a single setup. Despite having lower transmittance than Mo/B₄C, the oxidation resistance of Pd eliminates the need for protective capping, simplifying optical design. These results establish Pd as the preferred material for broadband MCD studies of magnetic materials.