Electron knock-on damage effects on electron magnetic chiral dichroism of magnetic metals using cobalt as a model.

This article focuses on the effects of electron knock-on damage on electron magnetic chiral dichroism (EMCD), a transmission electron microscopy technique for quantitative magnetic measurements, using metallic cobalt as a model system. The study identifies three key surface damage issues—surface oxidation, amorphization, and thickness reduction—and finds that the gradual removal of the thin surface oxidation layer during electron irradiation introduces residual nonmagnetic components in EMCD spectra, leading to significant overestimation of the orbital-to-spin moment ratio (ml/ms). It recommends minimizing oxidation effects by pre-irradiating the target area before EMCD acquisition and proposes further experiments to quantify how thickness reduction impacts magnetic components in momentum-resolved electron energy-loss spectra. These findings contribute to improving the accuracy of EMCD quantification in magnetic metals.