Site-Selective Electronic Structure and Dynamical Softness in the Metallic Antiferromagnet Mn₃CuN

Here, we combine element-specific X-ray spectroscopy, temperature-dependent X-ray absorption spectroscopy, X-ray magnetic circular dichroism, electrical transport measurements, and first-principles calculations to investigate the site-selective electronic structure of epitaxial metallic antiferromagnetic Mn₃CuN thin films.

We reveal an anomalous charge distribution characterized by effective low-valent Mn and subvalent Cu states stabilized by covalent Mn–N–Cu interactions. While the Mn sublattice forms a robust noncollinear antiferromagnetic framework below ∼120 K, the electronically distinct Cu sites remain magnetically inactive yet exhibit pronounced temperature-dependent local structural evolution. Despite the onset of magnetic ordering, Mn₃CuN retains metallic transport with a near-zero temperature coefficient of resistivity (NZ-TCR), indicating minimal coupling between magnetic ordering and charge transport.