Suppression of Anomalous Hall Effect by Post Annealing under Oxygen Atmosphere in YIG/Pt Heterostructure

The competition between magnetic-proximity-induced and spin-Hall-induced anomalous Hall effects (AHE) in Y₃Fe₅O₁₂ (111)/Pt heterostructures is an interesting topic. In this study, we systematically investigate how post-annealing in an oxygen atmosphere between 0 °C and 400 °C suppresses the AHE in YIG (111)/Pt bilayers down to low-temperature region (20 K) with magneto-transport measurement. In as-grown samples, the anomalous Hall resistivity ΔρAHE, 0.75 nΩ·cm at room temperature, decreases monotonically with decreasing temperature and reverses its sign below 100 K. We attribute this temperature dependence to the existence of two competing mechanisms of opposite signs: the magnetic-proximity-induced AHE (MPE-AHE) below 100 K and the spin-Hall-induced AHE (SH-AHE) above 100 K. With increasing post annealing temperature, we identify two distinct trends: room-temperature AHE stays unchanged up to 200°C annealing and drops significantly down to 20% of its initial value after 400°C annealing. However, the low-temperature negative AHE decreases its magnitude and eventually reverses its sign back to positive after annealing at 200°C. This observation indicates that post annealing under oxygen suppresses both AHE components with different rate: the MPE-AHE diminishes faster than the SH-AHE.