Large Temperature-invariant Anomalous Nernst Effect in Non-collinear Antiferromagnet Mn₃Pt

The pursuit of next-generation spintronic devices is pivoting toward noncollinear antiferromagnets (nc-AFMs), their vanishing net magnetization and inherent ultrafast spin dynamics enable the development of faster and more energy-efficient spintronic devices with strong resilience against external magnetic fields. Most importantly, their unique electronic and spin structures give rise to significant Berry curvature, leading to a significant magnetoelectric signal, such as the anomalous Nernst effect (ANE), even in the absence of sizable magnetization. Here, we report the discovery of a giant and remarkably temperature-invariant ANE in high-quality epitaxial Mn₃Pt thin films with various compositions, which allows thermoelectric devices with a wide operating temperature window. Mn₃Pt overwhelms other nc-AFMs rivals with a significant ANE coefficient up to 0.71 µV/K at room temperature. Our combined experimental observation and theoretical calculations establish that the composition-tunable Mn-3d orbital states govern the Berry curvature landscape, responsible for this exceptional performance. This study highlights the composition tunability as a venue for applicable nc-AFM spintronic devices.