Event

Layered antiferromagnets with topological band structure are promising platforms to host many interesting topological phenomena. Thus, it is imperative to visualize domains or domain walls in these topological antiferromagnets. Despite many decades’ efforts, it remains a grand challenge to visualize antiferromagnetic domains or domain walls in magnetic field. In this talk I will present our recent efforts on magnetic imaging of domains and domain walls in antiferromagnetic topological insulator MnBi₂Te₄ family using cryogenic magnetic force microscopy (MFM). Our MFM studies reveal enhanced magnetic susceptibility inside the domain walls due to the winding of the antiferromagnetic order parameter. In addition, our MFM data confirms that the A-type antiferromagnetic order persists to the surface of MnBi₂Te₄ and MnBi₄Te₇, which shed new light on the mystery of gapless topological surface states observed by high resolution angle-resolved photoemission spectroscopy.  The robust A-type order is further corroborated by the surprising discovery of the long-sought surface metamagnetic transitions. Our results pave the way for exploration of domain walls or surface magnetism in topological antiferromagnets using magnetic imaging.