Reciprocal and real space maps for EMCD experiments

TL;DR

This paper presents a method for quantitative EMCD measurements in TEM, emphasizing data treatment, normalization, and real space mapping to enhance magnetic material characterization at nanometer resolution.

Contribution

It introduces a new data processing approach and experimental setup, including telefocus mode, for improved EMCD signal detection and real space mapping in TEM.

Findings

Reliable quantitative ratio of orbital to spin magnetic moments achieved.

Real space EMCD maps demonstrated with high spatial resolution.

Enhanced signal intensity and artifact reduction using telefocus mode.

Abstract

Electron magnetic chiral dichroism (EMCD) is an emerging tool for quantitative measurements of magnetic properties using the transmission electron microscope (TEM), with the possibility of nanometer resolution. The geometrical conditions, data treatment and electron gun settings are found to influence the EMCD signal. In this article, particular care is taken to obtain a reliable quantitative measurement of the ratio of orbital to spin magnetic moment using energy filtered diffraction patterns. For this purpose, we describe a method for data treatment, normalization and selection of mirror axis. The experimental results are supported by theoretical simulations based on dynamical diffraction and density functional theory. Special settings of the electron gun, so called telefocus mode, enable a higher intensity of the electron beam, as well as a reduction of the influence from artifacts on the signal. Using these settings, we demonstrate the principle of acquiring real space maps of the EMCD signal. This enables advanced characterization of magnetic materials with superior spatial resolution.