Control of spin current and antiferromagnetic moments via topological surface state

Antiferromagnetic materials, which have ordered but alternating magnetic moments, exhibit fast spin dynamics and produce negligible stray fields, and could be used to build high-density, high-speed memory devices with low power consumption. However, the efficient electrical detection and manipulation of antiferromagnetic moments is challenging. Here we show that the spin current and antiferromagnetic moments in the topological insulator/antiferromagnetic insulator bilayer (Bi,Sb) 2 Te 3 /α-Fe 2 O 3 can be controlled via topological surface states. In particular, the orientation of the antiferromagnetic moments in α-Fe 2 O 3 can modulate the spin current reflection at the bilayer interface. In turn, the spin current can control the moment rotation in the antiferromagnetic insulator by means of a giant spin–orbit torque generated by the topological surface state. The required threshold switching current density is 3.5 × 10 6 A cm −2 at room temperature, which is one order of magnitude smaller than that required in heavy-metal/antiferromagnetic insulator systems.