Intralayer ferromagnetism between S=5/2 ions in MnBi2Te4: Role of empty Bi p states

Article

关键词: TOTAL-ENERGY CALCULATIONS;    MAGNETIC-PROPERTIES;    ELECTRON;    EXCHANGE;    CRYSTAL;   

DOI  :  10.1103/PhysRevB.101.201408

来源: SCIE

【 摘 要 】

The layered magnetic topological insulator MnBi2Te4 is a promising platform to realize the quantum anomalous Hall effect because its layers possess intrinsic ferromagnetism. However, it is not well understood why the high-spin d(5) magnetic ions Mn2+ forming the Mn-Te-Mn spin exchange paths prefer ferromagnetic (FM) coupling, contrary to the prediction of the Goodenough-Kanamori rule that a TM-L-TM spin exchange where TM and L are a transition-metal magnetic cation and a main group ligand, respectively, is antiferromagnetic (AFM) even when the bond angle of the exchange path is 90 degrees. Using density functional theory calculations, we show that the presence of Bi3+ ions is essential for the FM coupling in MnBi2Te4. Then, using a tight-binding model Hamiltonian, we find that high-spin d(5) ions (S = 5/2) in TM-L-TM spin exchange paths prefer FM coupling if the empty p orbitals of a nonmagnetic cation M (e.g., Bi3+ ion) hybridize strongly with those of the bridging ligand L but AFM coupling otherwise.

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