Molecular control of Spin Hall and Unidirectional Magnetoresistance in YIG/PtMn

Molecular engineering at metal interfaces has opened new avenues to design functional structures by manipulating charge transfer and hybridization effects. ^1–9 While earlier studies have mainly focused on controlling the ferromagnetic order, ^10–17 the tuning of antiferromagnetic (AF) properties remains largely unexplored. Here, we investigate an enhanced spin Hall effect in Y ₃ Fe ₅ O ₁₂ (YIG)/PtMn with a C ₆₀ overlayer. Our findings demonstrate a charge transfer from the antiferromagnetic PtMn to C ₆₀ , leading to a canted Mn ²⁺ -AF ordering at the PtMn/C ₆₀ interface. This charge transfer lowers the Fermi energy level of PtMn, a feature that is responsible for the enhanced spin Hall conductivity in YIG/PtMn/C ₆₀ . The interplay between the Mn ²⁺ -AF order at the molecular interface and the Néel vector of PtMn results in changes to the exchange bias, magnetic blocking of the YIG spins underneath, and the emergence of a highly sought-after unidirectional magnetoresistance (UMR). This UMR exhibits a sign change with the magnetic field polarity, providing insights into non-reciprocal magnetoresistance phenomena in high spin-orbit coupling systems. These results pave the way for developing tunable AF spintronic applications in rectification, low-power electronics, and beyond.