Strongly anisotropic spin dynamics in magnetic topological insulators

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 (MnBi2Te4)(Bi2Te3)(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 MnBi2Te4 while being almost isotropic in MnBi4Te7. 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.

Automated summary

The recent discovery of magnetic topological insulators has provided new insights into exploring exotic states of matter. By investigating magnetic fluctuations, it has been found that different compounds exhibit contrasting dynamics of Mn spins, with the anisotropy of magnetic fluctuations being controlled by carrier density and potentially impacting electronic topological surface states.