Imaging Flux Vortices in MgB2 using Transmission Electron Microscopy

TL;DR

This study demonstrates the direct imaging of magnetic flux vortices in MgB2 using transmission electron microscopy, revealing how sample preparation artifacts influence vortex patterns and pinning behavior.

Contribution

It introduces a method for imaging flux vortices in MgB2 with TEM and analyzes the effects of sample thinning artifacts on vortex pinning and arrangement.

Findings

Thinned MgB2 samples show vortex patterns affected by thickness undulations.

Thickness undulations act as pinning sites for vortices.

Vortex arrangements are significantly influenced by sample preparation artifacts.

Abstract

We report the successful imaging of flux vortices in single crystal MgB2 using transmission electron microscopy. The specimen was thinned to electron transparency (350 nm thickness) by focussed ion beam milling. An artefact of the thinning process was the production of longitudinal thickness undulations of height 1-2 nm in the sample which acted as pinning sites due to the energy required for the vortices to cross them. These had a profound effect on the patterns of vortex order observed which we examine here. Supplementary information can be downloaded from http://www-hrem.msm.cam.ac.uk/people/loudon/#publications