Room‐Temperature Magnetic Order in Topological Insulator Coupled with Highly Resistive Ferromagnet

Abstract Inducing long‐range magnetic order in topological insulators (TIs), thereby breaking the time‐reversal symmetry, is essential for constructing exotic new phases such as the quantum anomalous Hall effect or the axion insulator state. The magnetic proximity effect is regarded as a promising strategy to induce uniform magnetization to the topological surface states from ferromagnetic insulators. However, existing ferromagnetic insulators are difficult to introduce robust magnetic order into TIs at room temperature. This work designs a novel highly resistive ferromagnet by assembling Ni 80 Fe 20 clusters, and magnetic order is introduced into Bi 2 Te 3 via the magnetic proximity effect. The Ni 80 Fe 20 /Bi 2 Te 3 heterojunction exhibits a large anomalous Hall effect (AHE) at room temperature and can be effectively controlled by the cluster size. This indicates that the strong magnetic order has been induced into TIs, and the strength of proximity coupling is easily controllable. Theoretical analysis demonstrates that the proximity‐induced magnetism at the point contact interface cooperating with the strong spin‐orbit coupling in the TI effectively enhances the skew scattering mechanism, thereby dominating the AHE over the entire temperature range. The work provides a promising strategy for achieving room‐temperature magnetic order in TIs, and reveals its potential in manipulating topological surface states.