A collaborative research team led by the High Magnetic Field Laboratory at the Hefei Institutes of Physical Science, Chinese Academy of Sciences, together with Anhui University, Forschungszentrum Jülich in Germany, and Wuhan University of Technology, has developed an atomic-column-resolved electron magnetic circular dichroism (EMCD) method capable of imaging antiferromagnetic order at the atomic scale.
Their findings were recently published in Nature Nanotechnology.
Antiferromagnetic materials, with antiparallel atomic spins and zero net magnetization, are fast and resistant to external magnetic interference, making them ideal for high-speed, high-density spintronic devices. However, their zero net magnetization makes conventional imaging difficult, as neutron- or synchrotron-based methods have limited resolution and cannot easily probe microscopic regions or interfaces.
In this study, the team developed an EMCD technique using aberration-corrected transmission electron microscopy. The key breakthrough lies in detecting chiral reversal signals from opposite sides of a magnetic atomic column via electron energy loss spectroscopy , enabling extraction of magnetic information from individual atomic columns. Optimizing the diffraction geometry and signal acquisition scheme further enhanced the signal strength by an order of magnitude.
The method was demonstrated in two representative antiferromagnets, G-type DyFeO3 and C-type α-Fe2O3, successfully revealing atomic-scale magnetic order. At the DyScO3/SmFeO3 interface, it further captured a magnetic dead layer only one unit cell thick, showing significant suppression of magnetic order near the interface. These results provide crucial experimental evidence for understanding interfacial magnetic coupling and guiding interface engineering in spintronic devices.
This atomic-resolution imaging method overcomes long-standing limits in magnetic characterization, providing a powerful tool to study microscopic magnetic structures.
Atomic spin model of SmFeO3 (left), atomic-resolution elemental distribution (middle), and atomic-resolution magnetic signal (right). (Image by LIU Yizhou)