Single-pass STEM-EMCD on a zone axis using a patterned aperture: progress in experimental and data treatment methods

Abstract

Measuring magnetic moments in ferromagnetic materials at atomic resolution is theoretically possible using the electron magnetic circular dichroism (EMCD) technique in a (scanning) transmission electron microscope ((S)TEM). However, experimental and data processing hurdles currently hamper the realization of this goal. Experimentally, the sample must be tilted to a zone-axis orientation, yielding a complex distribution of magnetic scattering intensity, and the same sample region must be scanned multiple times with sub-atomic spatial registration necessary at each pass. Furthermore, the weak nature of the EMCD signal requires advanced data processing techniques to reliably detect and quantify the result. In this manuscript, we detail our experimental and data processing progress towards achieving single-pass zone-axis EMCD using a patterned aperture. First, we provide a comprehensive data acquisition and analysis strategy for this and other EMCD experiments that should scale down to atomic resolution experiments. Second, we demonstrate that, at low spatial resolution, promising EMCD candidate signals can be extracted, and that these are sensitive to both crystallographic orientation and momentum transfer.

Simultaneous mapping of EMCD signals and crystal orientations in a transmission electron microscope

“…Here, we adopted the profile matching routine recently used in Ref. 31 to sharpen the edges in the lower trace keeping the area under the edge same. After profile matching, the difference of the two spectra is taken and reported as EMCD signal in Table 1 .…”