Multiscale Vectorial Determination of Magnetic Order Parameters using Electron Magnetic Linear Dichroism

We demonstrate electron magnetic linear dichroism as a quantitative probe of vectorial magnetic order parameters with nanometer resolution in transmission electron microscopy. Explicit inclusion of vectorial core-level exchange splitting into mixed dynamic form factor simulations accounting for dynamical diffraction enables direct reconstruction of the magnetic spin axis from momentum-resolved electron energy-loss spectra. The resulting dichroic signal is intrinsically separable from nonmagnetic anisotropy, exhibits a well-defined dependence on the Néel vector or magnetization orientation, and remains robust down to the atomic scale. Applied to the collinear antiferromagnetic and ferromagnetic phase of cubic FeRh, this approach allows quantitative real-space mapping of the magnetic vector. These results open a pathway to nanoscale spectroscopy and imaging of antiferromagnets and altermagnets where the generalized approach to electron dichroism provides direct access to different magnetic order parameters.