The effect of antiferromagnetic order on transport of spin current in Pt/NiO/YIG heterostructures

We investigate the spin-current transport in antiferromagnetic insulator (AFMI) by means of the spin-Hall magnetoressitance (SMR), magnetization, and anomalous-Hall resistance (AHR) over a wide temperature range in Pt/NiO/Y$_3$Fe$_5$O$_{12}$ (Pt/NiO/YIG) heterostructures. By inserting AFMI NiO layer between YIG and Pt, the magnetic proximity effect (MPE) on induced Pt moments by YIG, which competes with the spin-Hall effect (SHE) in Pt, can be efficiently suppressed, and pure SMR can be derived in Pt/NiO/YIG. The dual roles of the NiO insertion including efficiently blocking the MPE and transporting the spin current between Pt and YIG layers are outstanding compared with other antiferromagnetic (AFM) metals or nonmagnetic metals (NM). However, the SMR is significantly suppressed with its sign reversal when approaching the AFM ordering temperature of NiO. The spin-current transmission is reduced rather than enhanced by the AFM order, which challenges the previous results of spin pumping or spin Seebeck.