Strongly anisotropic spin dynamics in magnetic topological insulators

Abstract

The recent discovery of magnetic topological insulators has opened new avenues to explore exotic states of matter that can emerge from the interplay between topological electronic states and magnetic degrees of freedom, be it ordered or strongly fluctuating. Motivated by the effects that the dynamics of the magnetic moments can have on the topological surface states, we investigate the magnetic fluctuations across the (MnBi${}_{\text{2}}$Te${}_{\text{4}}$)(Bi${}_{\text{2}}$Te${}_{\text{3}}$)${}_{\text{n}}$ family. Our paramagnetic electron spin resonance experiments reveal contrasting Mn spin dynamics in different compounds, which manifests in a strongly anisotropic Mn spin relaxation in MnBi${}_{\text{2}}$Te${}_{\text{4}}$ while being almost isotropic in MnBi${}_{\text{4}}$Te${}_{\text{7}}$. Our density-functional calculations explain these striking observations in terms of the sensitivity of the local electronic structure to the Mn spin-orientation, and indicate that the anisotropy of the magnetic fluctuations can be controlled by the carrier density, which may directly affect the electronic topological surface states.

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• Topological Hall Effect Driven by Short-Range Magnetic Orders in EuZn${}_2$As${}_2$
• Magnetic field tuning of the spin dynamics in the magnetic topological insulators (MnBi${}_2$Te${}_4$)(Bi${}_2$Te${}_3$)${}_n$
• Intrinsic magnetic topological insulators of the MnBi${}_2$Te${}_4$ family
• Low-energy excitations and magnetic anisotropy of the layered van der Waals antiferromagnet Ni${}_2$P${}_2$S${}_6$
• Magnetic warping in topological insulators
• Electron Spin Resonance Spectroscopy on Magnetic Van der Waals Compounds
• Room temperature spin-orbit torque efficiency in sputtered low-temperature superconductor delta-TaN
• Evolution of the spin dynamics in the van der Waals system $M_{\text{2}}$P${}_{\text{2}}$S${}_{\text{6}}$ (${\mathbf{M}}_{\text{2}}$ = Mn${}_{\text{2}}$, MnNi, Ni${}_{\text{2}}$) series probed by electron spin resonance spectroscopy
• Defect Engineering for Stabilizing Magnetic and Topological Properties in Mn(Bi1-xSbx)2Te4
• Fate of surface gaps in magnetic topological insulators