Two-dimensional ferromagnetism with long-range interactions in the layered magnetic topological insulator MnBi2Te4

Abstract

MnBi2Te4(MBT) is a promising van der Waals layered antiferromagnetic (AF) topological insulator that combines a topologically non-trivial inverted Bi-Te band gap with ferromagnetic (FM) layers of Mn ions. We perform inelastic neutron scattering (INS) on co-aligned single crystals to study the magnetic interactions in MBT. Consistent with previous work, we find that the AF interlayer exchange coupling and uniaxial magnetic anisotropy have comparable strength, which supports metamagnetic transitions that allow access to different magnetic symmetries in applied fields. Modelling of the two-dimensional intralayer FM spin waves requires the introduction of long-range and competing Heisenberg FM and AF interactions, up to at least the seventh nearest-neighbor, and possess anomalous damping, especially near the Brillouin zone boundary. First-principles calculations of insulating MBT find that both interlayer and intralayer magnetic interactions are long-ranged. We discuss the potential roles that bulk $n$-type charger carriers and chemical disorder play in the magnetism of MBT.

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• Role of Magnetic Defects and Defect-engineering of Magnetic Topological Insulators
• Magnon-magnon interaction in monolayer MnBi${}_2$Te${}_4$
• Kernel Polynomial Method for Linear Spin Wave Theory
• Topological Interlayer Superconductivity in a van der Waals Heterostructure
• Tailoring Neel orders in Layered Topological Antiferromagnets
• Efficient Quantum Transduction Using Anti-Ferromagnetic Topological Insulators
• Magnetic interactions and excitations in SrMnSb${}_2$
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