Electrically controlled magnetization in ferromagnet-topological insulator heterostructures

Electrostatic control of magnetic anisotropy is proposed by utilizing a hybrid structure of a topological insulator (TI) and insulating ferromagnet. The concept relies on the exchange interaction at the interface and the subsequent change in the free energy of the combined system. Calculations illustrate that the spin-momentum interlocked nature of TI surface electrons can induce the out-of-plane magnetic anisotropy of the system. Moreover, it is shown that modulation of its strength via surface chemical potential can achieve magnetization rotation between the in-plane and out-of-plane directions with a characteristic time of nanoseconds. A deterministic 180 degrees turn is further hypothesized with the aid of a small TI surface current with natural spin polarization.