Breaking resolution limit of electron microscopy for magnetic materials

Iron-rhodium is the metal that Prof. Dr. Christian Kübel and his colleagues are mainly working with at present. Placing it under an electron microscope, Christian Kübel of the Karlsruhe Institute of Technology explains, "At room temperatures, it’s antiferromagnetic. When you increase the temperature, it becomes ferromagnetic." The transition between these two states is a research area of great interest: how do defects in the atomic structure or stresses around precipitates influence the magnetic structure and thereby affect the magnetic properties of the metal?

Image of a microscope

The trouble is that it has been difficult so far to precisely quantify how much myelin is present. Experienced radiologists can assess brain tissue subjectively from MRI scans, where the variations in contrast allow them to draw conclusions about the state of the myelin, however they cannot determine the exact amount.

Decorative image with blue, green, pink and yellow colors

This is precisely the challenge to be tackled in this project. "We want to use a ptychographic approach to directly reconstruct the phase gradients, rather than the phase," Christian Kübel says. This involves scanning samples under an electron microscope to deliver so-called diffraction pattern data. Instead of taking the usual approach of reconstructing phase and amplitude information from this data to calculate the magnetic properties, which is subject to error, the researchers with the group of Frank Filbir of the Helmholtz Zentrum München want to develop an algorithm that computes the magnetic information directly from the data. This is an important step forward for the basic research of magnetic materials, given that the method will be useful not only for iron-rhodium but also for many other materials.