Enhanced Anomalous Hall Effect of Pt on an Antiferromagnetic Insulator with Fully Compensated Surface

We report a significantly enhanced anomalous Hall effect (AHE) of Pt on antiferromagnetic insulator thin film (3-unit-cell La_0.7Sr_0.3MnO_3, abbreviated as LSMO), which is one order of magnitude larger than that of Pt on other ferromagnetic (e.g. Y_3Fe_5O_12) and antiferromagnetic (e.g. Cr_2O_3) insulator thin films. Our experiments demonstrate that the antiferromagnetic La_0.7Sr_0.3MnO_3 with fully compensated surface suppresses the positive anomalous Hall resistivity induced by the magnetic proximity effect and facilitates the negative anomalous Hall resistivity induced by the spin Hall effect. By changing the substrate's temperature during Pt deposition, we observed that the diffusion of Mn atoms into Pt layer can further enhance the AHE. The anomalous Hall resistivity increases with increasing temperature and persists even well above the Neel temperature (T_\rm N) of LSMO. The Monte Carlo simulations manifest that the unusual rise of anomalous Hall resistivity above T_\rm N originates from the thermal induced magnetization in the antiferromagnetic insulator.