Emergent Topological Hall Effect at a Charge-Transfer Interface

Abstract

Exploring exotic interface magnetism due to charge transfer and strong spin-orbit coupling has profound application in the future development of spintronic memory. Here, the emergence and tuning of topological Hall effect (THE) from a CaMnO3/CaIrO3/CaMnO3 trilayer structure are studied in detail, which suggests the presence of magnetic Skyrmion-like bubbles. First, by tilting the magnetic field direction, the evolution of the Hall signal suggests a transformation of Skyrmions into topologically-trivial stripe domains, consistent with behaviors predicted by micromagnetic simulations. Second, by varying the thickness of CaMnO3, the optimal thicknesses for the THE signal emergence are found, which allow identification of the source of Dzyaloshinskii–Moriya interaction (DMI) and its competition with antiferromagnetic superexchange. Employing high-resolution transmission electron microscopy, randomly distributed stacking faults are identified only at the bottom interface and may avoid mutual cancellation of DMI. Last, a spin-transfer torque experiment also reveals a low threshold current density of ≈109 A m−2 for initiating the bubbles’ motion. This discovery sheds light on a possible strategy for integrating Skyrmions with antiferromagnetic spintronics.