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

TL;DR

This paper reports progress in developing a single-pass EMCD technique on a zone axis using a patterned aperture, aiming to enable atomic resolution magnetic measurements in ferromagnetic materials.

Contribution

The authors introduce a comprehensive data acquisition and analysis strategy for EMCD experiments and demonstrate initial promising signals at low spatial resolution.

Findings

Potential to extract EMCD signals sensitive to crystallography and momentum transfer

Progress towards single-pass zone-axis EMCD with patterned aperture

Methodology scalable to atomic resolution experiments

Abstract

Measuring magnetic moments in ferromagnetic materials with atomic column 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.