  Electrical currents in a magnetic insulator/heavy metal heterostructure can
induce two simultaneous effects, namely, spin Hall magnetoresistance (SMR) on
the heavy metal side and spin-orbit torques (SOTs) on the magnetic insulator
side. Within the framework of the pure spin current model based on the bulk
spin Hall effect (SHE), the ratio of the spin Hall-induced anomalous Hall
effect (SH-AHE) to SMR should be equal to the ratio of the field-like torque
(FLT) to damping-like torque (DLT). We perform a quantitative study of SMR,
SH-AHE, and SOTs in a series of thulium iron garnet/platinum or Tm3Fe5O12/Pt
heterostructures with different Tm3Fe5O12 thicknesses, where Tm3Fe5O12 is a
ferrimagnetic insulator with perpendicular magnetic anisotropy. We find the
ratio between measured effective fields of FLT and DLT is at least 2 times
larger than the ratio of the SH-AHE to SMR. In addition, the bulk SHE model
grossly underestimates the spin torque efficiency of FLT. Our results reveal
deficiencies of the bulk SHE model and also address the importance of
interfacial effects such as the Rashba and magnetic proximity effects in
magnetic insulator/heavy metal heterostructures.

Materials Science