Coexistence of ferromagnetism and topology by charge carrier engineering in the intrinsic magnetic topological insulator MnBi4Te7

Abstract

Intrinsic magnetic topological insulators (MTIs) $\mathrm{Mn}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{4}$ and $\mathrm{Mn}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{4}/{({\mathrm{Bi}}_{2}{\mathrm{Te}}_{3})}_{n}$ are expected to realize the high-temperature quantum anomalous Hall effect and dissipationless electrical transport. However, there is still a lack of ideal MTI candidates with magnetic ordering of the ferromagnetic (FM) ground state. Here, we show a MTI sample of $\mathrm{Mn}{({\mathrm{Bi}}_{0.7}{\mathrm{Sb}}_{0.3})}_{4}{\mathrm{Te}}_{7}$ which holds the coexistence of a FM behavior state and topological nontriviality. The dramatic modulation of the magnetism is induced by a charge carrier engineering process via the Sb substitution in the $\mathrm{Mn}{\mathrm{Bi}}_{4}{\mathrm{Te}}_{7}$ matrix with antiferromagnetic ordering. The evolution of magnetism in $\mathrm{Mn}{({\mathrm{Bi}}_{1\ensuremath{-}x}{\mathrm{Sb}}_{x})}_{4}{\mathrm{Te}}_{7}$ is systematically investigated by our magnetic measurements and theoretical calculations. The clear topological surface states of the FM sample of $\mathrm{Mn}{({\mathrm{Bi}}_{0.7}{\mathrm{Sb}}_{0.3})}_{4}{\mathrm{Te}}_{7}$ are further verified by angle-resolved photoemission spectroscopy. The demonstration of the intrinsic FM-MTI of $\mathrm{Mn}{({\mathrm{Bi}}_{0.7}{\mathrm{Sb}}_{0.3})}_{4}{\mathrm{Te}}_{7}$ in this paper sheds light on further material optimization of intrinsic MTIs and paves the way for further studies to clarify the relationships between topology, magnetism, and charge carriers in topological materials.