Breakdown of the dipole approximation in core losses.

The validity of the dipole approximations commonly used in the inelastic scattering theory for transmission electron microscopy is reviewed. Both experimental and numerical arguments are presented, emphasizing that the dipole approximations cause significant errors of the order of up to 25% even at small momentum transfer. This behavior is attributed mainly to non-linear contributions to the dynamic form factor due to the overlap of wave functions.

EMCD real space maps of Magnetospirillum magnetotacticum.

In this study we combine energy loss magnetic circular dichroism (EMCD) and energy filtered transmission electron microscopy (EFTEM) to map magnetic properties of nanoparticles. We show that it is a functional tool for investigating the magnetic behaviour of bio-mineralized magnetite crystals of Magnetospirillum magnetotacticum. We find that the spatial resolution of our experimental set-up is in the range of less than 2 nm. The results are compared with EMCD studies of abiogenic magnetite.