Coincidence of Superparamagnetism and perfect quantization in the Quantum Anomalous Hall state

TL;DR

This paper investigates the coexistence of superparamagnetism and perfect quantum anomalous Hall quantization in doped topological insulators, revealing potential inhomogeneities and percolation effects affecting magnetic and transport properties.

Contribution

It provides experimental evidence linking superparamagnetic behavior with robust quantum anomalous Hall effects in materials of low crystalline quality.

Findings

Perfect quantum anomalous Hall quantization observed

Transport data suggest inhomogeneities and magnetic inhomogeneity

Possible relevance of percolation path interpretation across magnetic field range

Abstract

Topological insulators doped with transition metals have recently been found to host a strong ferromagnetic state with perpendicular to plane anisotropy as well as support a quantum Hall state with edge channel transport, even in the absence of an external magnetic field. It remains unclear however why a robust magnetic state should emerge in materials of relatively low crystalline quality and dilute magnetic doping. Indeed, recent experiments suggest that the ferromagnetism exhibits at least some superparamagnetic character. We report on transport measurements in a sample that shows perfect quantum anomalous Hall quantization, while at the same time exhibits traits in its transport data which suggest inhomogeneities. We speculate that this may be evidence that the percolation path interpretation used to explain the transport during the magnetic reversal may actually have relevance over the entire field range.