Sn*

Recently, non-collinear antiferromagnets have attracted immense interest owning to their topologically protected band structure, non-collinear magnetic order, and spontaneous time-reversal symmetry breaking. As a prominent material candidate of this family, Mn₃Sn has been the subject of intensive research, showing rich fundamental physics as well as enormous technological promise for practical applications. Here, we report quantum imaging of magnetic domains in noncollinear antiferromagnet Mn₃Sn and visualize their microscopic response to external magnetic field and spin-orbit torques at the nanoscale. Our results ascertain the advantages of NV quantum metrology in both spatial and field sensitivity for studying nanomagnetism hosted by emergent condensed matter systems. We highlight that the presented NV measurement platform could be extended naturally to a broad range of quantum materials, opening new opportunities for studying the interplay between topology and magnetism.