An alternative ground state of MnBi2Te4 obtained by magnetic annealing

Magnetic topological insulators are extremely interesting because they combine the unique properties of topological insulators with magnetism. While as-grown MnBi2Te4 single crystals exhibit an A-type antiferromagnetic (AFM) ordering at TN≈ 24 K, annealed MnBi2Te4 under 10 T leads to the change of the magnetic properties from AFM to superparamagnetic behavior with the trend of the magnetization saturation at 2 K. Correspondingly, the magnetotransport properties change as well, revealing large positive magnetoresistance with the linear field dependence at low temperatures. Through the first-principles calculations, we provide insight into the experimental results. Our investigation demonstrates that magnetic annealing is a powerful approach for manipulating material properties due to the nearly degenerate ground states in MnBi2Te4.