Spin Transport Across Interfaces With the Non-Collinear Antiferromagnet Mn₃Sn

Non-collinear antiferromagnets such as ${\mathrm{Mn}}_3\mathrm{Sn}$ are promising materials for ultrafast spintronic applications due to their peculiar electronic structure and efficient spin-dependent transport phenomena. Here, we investigate magnetic ordering and ultrafast spin transport in c-axis oriented ${\mathrm{Mn}}_3\mathrm{Sn}$ thin films and ${\mathrm{Mn}}_3\mathrm{Sn}$ -based heterostructures with Pt and ${\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20}$ . Temperature-dependent magneto-optical Kerr effect measurements confirm thermally activated switching of the ${\mathrm{Mn}}_3\mathrm{Sn}$ cluster octupole moment near the Néel temperature, while preserving predominantly in-plane magnetic order. In ${\mathrm{Mn}}_3\mathrm{Sn}|\mathrm{Pt}$ heterostructures, however, pronounced room-temperature ferromagnetic signatures are observed, including enhanced Kerr rotation and out-of-plane magnetization. Systematic magnetometry studies reveal the formation of an intermixed ${\mathrm{Mn}}_2\mathrm{PtSn}$ interfacial phase upon annealing. Ultrafast transport measurements using a sample with optimized interfaces show that optical excitation of ${\mathrm{Mn}}_3\mathrm{Sn}$ generates predominantly anomalous Nernst currents, with no detectable evidence of efficient spin-current injection into Pt. In contrast, ${\mathrm{Mn}}_3\mathrm{Sn}$ exhibits a significant inverse spin Hall conversion when driven by spin currents injected from ${\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20}$ , reaching approximately $10\%$ of the efficiency of Pt-based reference structures. The conversion efficiency is found to be independent of the relative orientation between ferromagnetic magnetization and antiferromagnetic octupole moment. Our results emphasize the importance of interface engineering for spintronic devices.