Scanning SQUID Microscopy of the Quantum Anomalous Hall Effect*

We report magnetic imaging of Cr-doped (Bi,Sb)₂Te₃ heterostructures in the quantum anomalous hall regime. We use a scanning superconducting quantum interference device (SQUID) microscope with micrometer scale spatial resolution to image the magnetic fields above current biased devices. Using these images, we reconstruct the current density, allowing us to visualize where current flows in the devices. We also use top and back gates to study how magnetization is affected by electrostatic gating. By performing these measurements as a function of current bias, gate voltage and magnetization direction, we construct a comprehensive picture of electronic transport in our devices.