Angstrom-Scale Mapping of the Local Magnetic Moment in Metallic Antiferromagnet Fe₂As using 4D-STEM

Antiferromagnets are a promising platform for high density spintronic devices. Techniques such as Lorentz transmission electron microscopy (LTEM) have been used to probe the arrangement of spins in topological structures such as skyrmions but cannot achieve the high spatial resolution needed to observe the local magnetic structure in antiferromagnets. In our work, we apply 4-dimensional scanning transmission electron microscopy (4D-STEM) with a fast, high dynamic range pixelated detector to investigate the magnetic structure of Fe₂As, a metallic antiferromagnet. Using a combination of quantum mechanical electron scattering simulations and experimental data, we show how the weak scattering signals from magnetism can be isolated in convergent beam electron diffraction patterns.  We apply our findings to measure the direction and magnitude of the local magnetization and obtain up to 6 Å resolution in Fe₂As.  Our results indicate new applications for 4D-STEM to study the magnetic structure of antiferromagnets.