New lens design is set to revolutionise electron microscopes
Understanding the connection between atomic structure and the magnetic structure it produces could enable designing magnetic materials and devices, like computer memory, from the atomistic scale.
In work just published in Nature Communications, an international team of researchers including Dr Scott Findlay from the Monash School of Physics and Astronomy present a new lens design that enables atomic resolution imaging in a magnetic field free environment.
Modern electron microscopes can directly image atoms in solids, but do so by putting the sample inside the magnetic lens used to magnify the atomistic details. This can change, or even destroy, magnetic and other physical structures of interest in the sample.
Dr Scott Findlay said the new instrument will allow us to see structures in magnetic materials that were previously invisible.
“Lenses in electron microscopes are made from magnetic fields,” he said.
“Powerful lenses require powerful fields. But they can also change the very thing you want to look at.”
This has prevented atomic resolution imaging of magnetic samples – a significant limitation on understanding this class of materials.
The new design overcomes this problem by using opposing lenses above and below the sample – allowing for the same magnification while cancelling the fields out at the sample.
As proof-of-principle, the paper shows atomic resolution images of an iron-silicon steel. Observing atomic-scale defects in these materials helps us understand and improve their strength.
Dr Findlay said the new lens design brings us a step closer to the tantalising prospect of probing atomic-scale magnetic fields, but that this remains challenging because the effect of these fields on the probing electron beam is very weak.
“We’re not there yet,” said Dr Findlay, “but new tools often lead to new discoveries. It’ll be exciting to see what this new instrument can achieve.”
The research was led by the University of Tokyo, and electron microscope manufacturer JEOL Ltd. Japan.
Dr Findlay, Dr Timothy Petersen and Professors David Paganin and Michael Morgan at Monash University, and Professor Naoya Shibata at the University of Tokyo, hold an Australian Research Council Discovery Project grant on nanoscale electromagnetic field mapping in materials.