102nd CEMS Colloquium

Title

Development of Magnetic-Field-Free STEM – How I Learned to Stop Worrying and Love Magnetic Materials –

Abstract

Scanning transmission electron microscopy (STEM) is a powerful technique to directly observe atomic-scale structures inside materials and devices. In the state-of-the-art STEM, a probe size of less than 0.5Å in diameter has been experimentally realized. Now, the following interesting question arises: beyond just atoms, what might become observable by using such fine electron probes? One answer to this question may be exploring new possibilities in phase contrast imaging of STEM [1]. By using elaborate detectors, we can not only image single atoms, but can also image electric field distribution inside single atoms [2]. It then becomes tempting to directly observe magnetic fields of atoms. However, atomic-resolution observation of magnetic materials is essentially very difficult because high magnetic fields (2~3T) are always exerted on samples inside the magnetic objective lens. In recent years, we have developed a new magnetic objective lens system that realizes a magnetic field free environment at the sample position [3]. Using this new objective lens system, real-space visualization of intrinsic magnetic fields of an antiferromagnet has been achieved [4]. This novel electron microscope (Magnetic-field-free Atomic Resolution STEM: MARS) is expected to be used for research and development of many magnetic materials and devices.

[1] N. Shibata et al., Nature Phys. 8, 611-615 (2012).
[2] N. Shibata et al., Nature Comm. 8, 15631 (2017).
[3] N. Shibata et al., Nature Comm. 10, 2380 (2019).
[4] Y. Kohno et al., Nature 602, 234 (2022).