Thin films of topological insulator Bi_2Se_3 were deposited directly on insulating ferromagnetic EuS. Unusual negative magnetoresistance was observed near the zero field below the Curie temperature (T_C), resembling the weak localization effect; whereas the usual positive magnetoresistance was recovered above T_C. Such negative magnetoresistance was only observed for Bi_2Se_3 layers thinner than t~4nm, when its top and bottom surfaces are coupled. These results provide evidence for a proximity effect between a topological insulator and an insulating ferromagnet, laying the foundation for future realization of the half-integer quantized anomalous Hall effect in three-dimensional topological insulators.
@article{arxiv.1306.2038,
title = {Emerging Weak Localization Effects on Topological Insulator-Insulating Ferromagnet (Bi_2Se_3-EuS) Interface},
author = {Qi I. Yang and Merav Dolev and Li Zhang and Jinfeng Zhao and Alexander D. Fried and Elizabeth Schemm and Min Liu and Alexander Palevski and Ann F. Marshall and Subhash H. Risbud and Aharon Kapitulnik},
journal= {arXiv preprint arXiv:1306.2038},
year = {2013}
}