A simulation study of voltage-assisted low-energy switching of a perpendicular anisotropy ferromagnet on a topological insulator

We present a novel memory device that consists of a thin ferromagnetic layer of Fe deposited on topological insulator thin film, \(\hbox {Bi}_{2}\hbox {Se}_{3}\). The ferromagnetic layer has perpendicular anisotropy, due to MgO deposited on its top surface. When current is passed on the surface of \(\hbox {Bi}_{2}\hbox {Se}_{3}\), the surface of the \(\hbox {Bi}_{2} \hbox {Se}_{3}\) becomes spin polarized and strong exchange interaction occurs between the d electrons in the ferromagnet and the electrons conducting the current on the surface of the \(\hbox {Bi}_{2}\hbox {Se}_{3}\). Part of the current is also shunted through the ferromagnet, which generates spin transfer torque in the ferromagnet. The exchange interaction torque along with voltage-controlled magnetic anisotropy allows ultralow-energy switching of the ferromagnet. We perform micromagnetic simulations and predict switching time of the order of 2.5 ns and switching energy of the order of 0.88fJ for a ferromagnetic bit with thermal stability of \(43\,k_\mathrm{{B}}T\). Such ultralow-energy and high-speed switching of a perpendicular anisotropy ferromagnet on a topological insulator could be utilized for energy-efficient memory design.