The anomalous Hall effect was discovered more than 130 years ago in ferromagnetic materials,
in which a Hall resistance exists even in the absence of external magnetic field. The quantized version of the anomalous Hall effect has attracted much interest since the discovery of quantum Hall effect in the 1980s. A few years ago, it was proposed that quantum anomalous Hall effect may occur in magnetically doped topological insulators, but the experimental realization has been elusive. In this talk we will report transport studies of topological insulator thin films grown by molecular beam epitaxy. The main focus will be on the tuning of the electronic structure, magnetic ordering, and bulk band topology, which led to the experimental realization of the quantum anomalous Hall effect, i.e., the quantum Hall effect in zero magnetic field.

Reference:
http://www.sciencemag.org/content/early/2013/03/13/science.1234414