Orbital Angular Momentum Correlated Charge to Spin Conversion in Metallic Antiferromagnet.

Current-induced spin-orbit torque (SOT) allows efficient electrical manipulation on magnetization in spintronic devices. Maximizing the SOT efficiency is a key goal that is pursued via increasing the net spin generation and accumulation. However, spin transport in antiferromagnets is seriously restricted due to the strong antiferromagnetic coupling, which blocks the development of antiferromagnetic-based devices. Here, a significant enhancement of SOT efficiency in Ir20Mn80 (IrMn)-based heterostructure associated with the orbital effect of naturally oxidized Cu (Cu*) bottom layer is reported. Considering the weak spin-orbit coupling of Cu*, the enhancement results from an orbital current generated from charge current at the Cu*/IrMn interface that contributes to spin current in the IrMn layer due to the strong spin-orbit coupling. The SOT efficiency variation with IrMn thickness reveals the process of orbital angular momentum (OAM) transportation and conversion. Moreover, the contribution of orbital current is verified by the critical current density decreasing of SOT-driven magnetization switching in Cu*/IrMn/[Co/Pt]3 heterostructure. This study opens a path to design high-efficient SOT-based spintronic devices combining the advantages of OAM and metallic antiferromagnets.