Opto-electrical approach to visualize magnetic nanostructures of chiral antiferromagnets

Abstract

This dissertation presents magnetic domain imaging methods based on Berry curvature-driven optical and magnetotransport responses. The goal is to investigate chiral antiferromagnetic materials ideal for spintronic applications. Major features of antiferromagnets are high-speed dynamics and negligible stray fields that allow for miniaturization. In this work, spatially resolved magnetic circular dichroism and anomalous Nernst effect (ANE) signals are measured to image magnetic domains. A manganese-based Weyl semimetal (Mn3Sn) exhibiting a noncollinear AF ordering is studied. The field-induced switching in Mn3Sn is observed with the spatially resolved ANE measurements down to the nanoscale regime. An enhanced optical near-field confined to the atomic force microscope tip is utilized to achieve nanoscale spatial resolution beyond the diffracted limited laser focal spot size of a few hundred nanometers.