Spin-Hall magnetoresistance in Ta/Cr/YIG trilayers with different Cr thicknesses

We report an investigation of spin-Hall magnetoresistance (SMR) in Ta/Cr/Y₃Fe₅O₁₂ (Ta/Cr/YIG) trilayers with different thicknesses of the Cr inserted layer. The Ta/Cr/YIG film with a 1-nm-thick Cr layer shows a maximum SMR of 4.2×10^-4 at 100 K, which is an order of magnitude larger than that previously reported in the Ta/YIG or Cr/YIG systems. The enhancement of SMR in the Ta/Cr/YIG is ascribed to the strong spin–orbit coupling (SOC) effect of both Ta and Cr and the anti-oxidation protection by the Ta coating. A negative SMR different from the conventional SMR is found for the Ta/Cr/YIG with the Cr thicknesses of 3 and 6 nm at the temperature below 100 and 260 K, respectively, which suggests the occurrence of the spin-flop coupling between the antiferromagnetic Cr and ferromagnetic YIG moments. Both the anisotropic magnetoresistance (AMR) and the anomalous-Hall resistance (AHR) indicate an induced ferromagnetism of Cr which is likely due to the spin-flop transition or the uncompensated magnetic moments. Our results suggest that the 3d transition metal Cr can be used as a spin current generator, and the antiferromagnetic structure of Cr can be employed to regulate the transport of spin current.