  Use of electron vortex beams (EVB), that is convergent electron beams
carrying an orbital angular momentum (OAM), is a novel development in the field
of transmission electron microscopy. They should allow measurement of
element-specific magnetic properties of thin crystals using electron magnetic
circular dichroism (EMCD)---a phenomenon similar to the x-ray magnetic circular
dichroism. Recently it has been shown computationally that EVBs can detect
magnetic signal in a scanning mode only at atomic resolution. In this follow-up
work we explore in detail the elastic and inelastic scattering properties of
EVBs on crystals, as a function of beam diameter, initial OAM, acceleration
voltage and beam displacement from an atomic column. We suggest that for a 10
nm layer of bcc iron oriented along (001) zone axis an optimal configuration
for a detection of EMCD is an EVB with OAM of $1\hbar$ and a diameter of 1.6
\AA, acceleration voltage 200 keV and an annular detector with inner and outer
diameters of $G$ and $5G$, respectively, where $\mathbf{G}=(100)$.
