Investigation of orbital and spin moments with atomic resolution using momentum-resolved EELS
Gatan instruments used
GIF Continuum® K3® and ω-Q-Slit
Background
Investigating the magnetic properties of materials requires an understanding of how the contributions of orbital and spin angular momentum vary at the atomic level. Traditional techniques like x-ray magnetic circular dichroism (XMCD) and scanning probe microscopy offer limited spatial resolution or are only sensitive to changes at the surface. While electron holography and differential phase contrast techniques can achieve atomic resolution, they are mostly limited to specific antiferromagnetic materials and requires a highly specialized transmission electron microscope (TEM). Electron magnetic circular dichroism (EMCD), an electron-based analogue of XMCD, uses diffraction from the crystal lattice to separate dichroic effects in momentum space. By using a rectangular-shaped aperture (ω-Q-Slit), the change in the energy loss spectra along a specific crystallographic direction (momentum) is observed, which can then be used for the study of EMCD. Combined with aberration-corrected STEM, Ali et. al. demonstrate that quantitative EMCD mapping of individual atomic planes can be used to study the sub-atomic origins of a material’s magnetic properties.