Magnetic circular dichroism in EELS: towards 10 nm resolution.

We describe a new experimental setup for the detection of magnetic circular dichroism with fast electrons (EMCD). As compared to earlier findings the signal is an order of magnitude higher, while the probed area could be significantly reduced, allowing a spatial resolution of better than 40 nm. A simplified analysis of the experimental results is based on the decomposition of the mixed dynamic form factor S(q-->,q-->('),E) into a real part related to the scalar product and an imaginary part related to the vector product of the scattering vectors q--> and q-->('). Following the recent detection of chiral electronic transitions in the electron microscope the present experiment is a crucial demonstration of the potential of EMCD for nanoscale investigations.