Anomalous Hall Effect due to Topological Magnetic Charge Correlation in Permalloy Honeycomb Lattice.

Two-dimensional artificial honeycomb lattice of connected ferromagnetic elements undergoes temperature dependent evolution of magnetic phases and provides a facile platform for exploring novel electric and magnetic properties. Hall probe measurements on a honeycomb lattice of connecting permalloy elements, with a typical length of 12 nm, suggest that as temperature decreases, the system undergoes a magnetic phase transition that renders the Hall resistance from the anomalous Hall effect (AHE) type to an unusual oscillatory type at low temperature. Magnetic measurements in a perpendicular magnetic field of the same system also reveal quantized magnetization, characterized by two field-induced jumps in the magnetization. The oscillatory behavior in Hall resistance and the quantized magnetization provide evidence to the emergence of topologically nontrivial chiral magnetic vortex loops in the novel spin solid state at low temperature. The experimental observation is supplemented by first-principle theoretical calculations. Finally, we will discuss the implication of the Hall probe results in a broader perspective of condensed matter physics research on 2D materials.