Magnetic Switching with Topological Insulator and Compensated Ferrimagnet*

New materials and physics mechanisms are required to realize next generation spintronic devices with fast speed and low power consumption. In this talk, I will focus on two novel material systems which can provide superior performances for magnetic switching. First of all, it is known that with the application of surface charge current, one can generate spin accumulation on topological insulators, which can be further utilized to manipulate magnetic moments via the spin-orbit torques. Through experiments, we show that magnetic switchings can be realized in a topological insulator/magnet bilayer at room temperature. This represents a major advance compared with previous works where flipping of magnetic moments was only realized at liquid helium temperature. The large effective spin Hall angle provide a definitive proof on the high spin-orbit torque efficiency from topological insulators. The large reduction in switching energy makes topological insulators outstanding candidates to realize high-efficiency magnetic switching devices . Secondly, antiferromagnetically coupled material can exhibit fast dynamics as well as robust protection against external magnetic fields, which can enable spintronic devices with fast speed and high density. In this talk, I will discuss our recent study on rare earth based ferrimagnetic alloys which has antiferromagnetically coupled sublattices, net zero magnetic moment and electrically controllable magnetic state. Particularly, I will show that the spin orbit torque provides an efficient writing mechanism for these materials even at the compesnation point. Moreover, to illustrate the speed advantage, we further carry out current induced domain wall motion experiment, where the highest domain wall mobility is obtained in samples with compensated angular momentum.