Current-induced Out-of-plane Spin Accumulation on the (001) Surface of the IrMn3 Antiferromagnet

Noncollinear antiferromagnetic materials have been known to generate large spin currents, and thus manipulate the magnetization efficiently. In this work, we spatially image the current-induced spin accumulation in the (001)- and (111)-oriented IrMn3 antiferromagnets upon injecting currents along different crystallographic directions by scanning photovoltage microscopy. In contrast to the conventional spin Hall effect, in which the spins lie in-plane at the top surface of devices, we observe significant out-of-plane spin accumulation on the device surface in IrMn3(001), whereas the out-of-plane spin accumulation is negligible in IrMn3(111). In addition, the spin accumulation in IrMn3(001) depends strongly on the current flow in different crystallographic directions, which is not the case for IrMn3(111), in line with the calculated spin Hall conductivity. The maximum spin Hall angle of IrMn3(001) and IrMn3 (111) are determined to be approximately 0.083 and 0.018, respectively. Our results pave the way for a better understanding of the current-induced spin accumulations in antiferromagnetic materials as well as the proposed field-free switching mechanisms in an antiferromagnet-ferromagnet system.