Detection of magnetic circular dichroism in amorphous materials utilizing a single‐crystalline overlayer

Abstract

Electron energy‐loss magnetic chiral dichroism (EMCD) in a transmission electron microscope allows the quantification of the magnetic structure of crystalline materials down to the nanometer scale [ 1‐3] . However, restricted by a confined diffraction geometry applied in EMCD experiments [4] , no experiments or theories have yet been performed to obtain EMCD signals for amorphous materials, due to their lack of long range ordering. In this work, we for the first time demonstrate it is possible to detect element‐specific magnetic signals in amorphous materials utilizing a single‐crystalline overlayer as an EMCD beam splitter. The approach is applied to a bilayer sample where a very thin amorphous magnetic FeO x layer is grown on a single‐crystalline Yttrium‐stabilized ZrO 2 substrate. We found that both experimental results and theoretical calculations lead to unprecedented EMCD signals. The quantitative orbital to spin magnetic moment ratio of Fe in amorphous FeO x layer has been acheived. Our approach allows us to break through the constraint of crystal formats in EMCD spectra measurements, providing new prospects of detecting EMCD signals from amorphous and ultrathin materials at the nanometer scale. This approach might also be extended to the magnetic quantitative analysis of other heterogeneous materials at high spatial resolution. This work may open a door to meet the challenge of exploring magnetic states and behaviors of amorphous films, and have important consequences for revealing the magnetic structures of magnetic materials in various crystal forms at the nanoscale using transmission electron microscopy.