Metastable MnBi${}_2$Te${}_4$ enabled by magnetic-field-assisted synthesis

Abstract

Magnetic topological insulators provide a unique platform to explore the interplay between magnetism and topology. MnBi${}_2$Te${}_4$, known for its A-type antiferromagnetic (AFM) ground state, undergoes a striking transformation when single crystals are grown in an applied magnetic field. Despite retaining the same crystal structure, field-grown MnBi${}_2$Te${}_4$ exhibits a ferromagnetic (FM) ground state with a Curie temperature of $\sim$ 12.5 K, confirmed by magnetization, magnetic torque, electrical resistivity, and specific heat measurements. First-principles calculations support these findings, revealing that magnetic-field-assisted synthesis can effectively reconfigure the ground-state spin order and thereby modify the material's electronic properties, as reflected in the de Haas-van Alphen oscillation seen in the magnetic torque.