Unusual magnetoresistance in a topological insulator with a single ferromagnetic barrier

Tunneling surface current through a thin ferromagnetic barrier on a three-dimensional topological insulator is shown to possess an extraordinary response to the orientation of barrier magnetization. In contrast to conventional magnetoresistance devices that are sensitive to the relative alignment of two magnetic layers, a drastic change in the transmission current is achieved by a single layer when its magnetization rotates by 90 degrees. Numerical estimations predict a giant magnetoresistance as large as 800% at room temperature with the proximate exchange energy of 40 meV at the barrier interface. When coupled with electrical control of magnetization direction, this phenomenon may be used to enhance the gating function with potentially sharp turn-on/off for low power applications. (C) 2011 American Institute of Physics. [doi:10.1063/1.3600330]