Precise quantization of anomalous Hall effect near zero magnetic field
  We report a nearly ideal quantum anomalous Hall effect in a three-dimensional topological insulator thin film with ferromagnetic doping. Near zero applied magnetic field we measure exact quantization in Hall resistance to within a part per 10,000 and longitudinal resistivity under 1 ohm per square, with chiral edge transport explicitly confirmed by non-local measurements. Deviations from this behavior are found to be caused by thermally-activated carriers, which can be eliminated by taking advantage of an unexpected magnetocaloric effect. 
A. J. Bestwick, E. J. Fox, Xufeng Kou, Lei Pan, Kang L. Wang, D.   Goldhaber-Gordon
cond-mat.mes-hall