Atomic resolution energy-loss magnetic chiral dichroism measurements enabled by patterned apertures

Hasan Ali,Devendra Negi,Jan Rusz,Klaus Leifer,Björgvin Hjörvarsson,Tobias Warnatz

doi:10.1103/physrevresearch.2.023330

Abstract

We give an experimental demonstration of two types of recently proposed ventilator apertures which can be used to acquire electron magnetic circular dichroic (EMCD) signals in zone axis orientation with high spatial resolution. To simplify the experimental procedures, we propose a third type of aperture and experimentally demonstrate the use of this modified ventilator aperture for the case of multiple symmetries in the diffraction patterns. To show the feasibility of the atomic resolution EMCD, EMCD signals are acquired for a range of beam convergence angles. High quality EMCD signals with convergence angles corresponding to atomic resolution electron probes are obtained.

Highlights

If one were to build an instrument for investigating spatial dependence of quantum effects at interfaces, one of the determining design criteria would be the obtained spatial resolution
We propose and experimentally demonstrate a simplified version of the ventilator aperture which has the freedom to be used in multiple crystal symmetries keeping a zone axis orientation
To verify the simulations shown in Ref. [18], we designed two single signal eight-hole (SS8) apertures, called ventilator apertures, for the [001] zone axis (ZA) of bcc Fe

Summary

INTRODUCTION

If one were to build an instrument for investigating spatial dependence of quantum effects at interfaces, one of the determining design criteria would be the obtained spatial resolution. One of the difficulties of the EMCD technique operating at subnanometer to atomic resolution is that high convergence angles of the focused electron probe are needed which have the drawback that the electron beam diffraction disks start to overlap in the diffraction plane making the q selection needed to obtain the EMCD signal difficult. We propose and experimentally demonstrate a simplified version of the ventilator aperture which has the freedom to be used in multiple crystal symmetries keeping a zone axis orientation Using this modified aperture we obtain a clear EMCD signal with α = 10 mrad

EXPERIMENTAL DETAILS

RESULTS AND DISCUSSION

CONCLUSIONS