MegaOhm Extraordinary Hall effect in oxidized CoFeB
  We report on development of controllably oxidized CoFeB ferromagnetic films demonstrating the extraordinary Hall effect (EHE) resistivity exceeding 1 Ohmcm and magnetic field sensitivity up to 10^6 Ohm/T. Such EHE resistivity is four orders of magnitude higher than previously observed in ferromagnetic materials, while sensitivity is two orders larger than the best of semiconductors 
G. Kopnov and A. Gerber
cond-mat.str-el cond-mat.mes-hall