Tunable Spin Hall Magnetoresistance in All-Antiferromagnetic Heterostructures

We investigate the spin Hall magnetoresistance (SMR) in all-antiferromagnetic heterostructures alpha-Fe2O3/Cr2O3 with Pt contacts. When the temperature is ultralow (< 50 K), the spin current generated in the Pt layer cannot be transmitted through Cr2O3 (t = 4 nm), and the SMR is near zero. Meanwhile, when the temperature is higher than the spin fluctuation temperature T (F) (approximate to 50 K) of Cr2O3 and lower than its Neel temperature T (N) (approximate to 300 K), the spin current goes through the Cr2O3 layer and is reflected at the alpha-Fe2O3/Cr2O3 interface; an antiferromagnetic (negative) SMR is observed. As temperature increases higher than T (N), paramagnetic (positive) SMR mainly arises from the spin current reflection at the Cr2O3/Pt interface. The transition temperatures from negative to positive SMR are enhanced with increasing Cr2O3 layer thickness, accompanied by the absence of SMR signals when t = 10 nm. Such a tunable SMR builds a bridge between spin transport and structures. It also enriches antiferromagnetic spintronics.