(Invited) Towards Topological Antiferromagnetic Spintronics

Abstract

Magnetic topological insulators in the tetradymite family, such as Cr/V doped Bi2Se3, Bi2Te3, Sb2Te3, and their ternary compounds, provide a new route for realizing the novel time-reversal symmetry-breaking physics [1, 2]. To effectively manipulate these versatile quantum states, various heterostructures are demonstrated by utilizing the unique Néel order in an antiferromagnet CrSb and the topological order in a magnetic topological insulator Cr-doped (Bi,Sb)2Te3 [3-5] grown by molecular beam epitaxy. It is shown that emergent interfacial magnetic interactions can be tailored through deliberate artificial structural engineering. By investigating bilayers, trilayers, and superlattices made of these two components, interfacial exchange coupling and antiferromagnetic exchange coupling were shown to affect the topological magnetism as mediated by the massive Dirac fermions. The relationship of magnetic spin textures of the antiferromagnet to that of the magnetic topological insulator was further explored through polarized neutron reflectometry/diffraction, magneto-electrical transport measurements as well as the control of the mass of Dirac fermions by using different Cr doping concentrations. From these studies, the antiferromagnet is shown to be an efficient interfacial- and interlayer- exchange coupling layer for the massive Dirac fermions of the magnetic topological insulator, which additionally gives rise to a giant enhancement in magnetic ordering. This work provides a new framework for new topological antiferromagnetic spintronics. *The work was in part supported by the SHINES Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences under Award # S000686, National Science Foundation, Army Research Office program under contract 15-1-10561, TANMS, FAME Center, and a Semiconductor Research Corporation program sponsored by MARCO and DARPA.