Anomalous Hall effect in Pt/La<sub>0.67</sub>Sr<sub>0.33</sub>MnO<sub>3</sub> heterojunctions

Many emergent and novel phenomena occur in nonmagnetic/ferromagnet heterostructures. In particular, Pt/ferromagnet heterostructures where the Pt has strong spin-orbit coupling and thus can convert spin current into charge current has attracted a great attention recently. The anomalous Hall effect (AHE) have been found in many Pt/ferromagnet heterostructures. However, the underline physics remains elusive, so it is necessary to find more heterostructure in order to provide more experimental basis. In this paper, we report an investigation of anomalous Hall resistance (AHR) in Pt thin films sputtered on epitaxial La_0.67Sr_0.33MnO₃ (LSMO) ferromagnetic films. High-quality Pt/LSMO heterojunctions were fabricated by pulsed laser deposition and RF-magnetron sputtering. The physical properties of LSMO films were characterized by the measurements of magnetic and transport properties. The AHR mainly contributed by Pt in the Pt/LSMO heterojunction increases sharply with decreasing temperature and changes its sign below 40 K. Furthermore, the AHR decreases sharply with increasing Pt thickness. There facts suggest that the ferromagnetism of Pt originates from interface due to magnetic proximity effect. Interestingly, this heterojunction can exhibit possible signal of topological Hall effect under low applied magnetic field. The above results provide an experimental basis for further understanding of electron spin and charge transport coupling in nonmagnetic/ferromagnetic heterostructures.