Quantum sensing and imaging of a topological antiferromagnet Mn₃Sn

Antiferromagnetic (AF) spintronics shows promise for next-generation computing technologies with improved density, stability, and energy efficiency in comparison with its ferromagnetic counterpart. The AF Weyl semimetal Mn₃Sn possesses a topologically protected band structure, non-collinear magnetic order, and spontaneous time reversal symmetry breaking, enabling exceptionally large magneto-transport and magneto-thermal responses which may be exploited for a broad range of spintronics applications. Despite these potential benefits, direct access to the magnetic domains and magnetic spin behaviors in Mn₃Sn remains a formidable challenge for the current state of the art. The major challenge results from the vanishingly small net magnetic moment of the Neél vector, which is difficult to access using existing magnetometry techniques. In this work, we use nitrogen-vacancy (NV) centers, optically active point defects in diamond, to image the local spin textures in polycrystalline Mn₃Sn thin films on a sub-micron length scale. We also probe the underlying spin dynamics in Mn₃Sn using NV relaxometry. Our results highlight the unique capabilities of NV centers as functional quantum sensors for investigating the magnetic properties of emergent topological antiferromagnets.