Intermediate anomalous Hall states induced by noncollinear spin structure in the magnetic topological insulator Mn Bi 2 Te 4

The combination of topology and magnetism is attractive to produce exotic quantum matters, such as the quantum anomalous Hall state, axion insulators, and the magnetic Weyl semimetals. $\mathrm{Mn}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{4}$, as an intrinsic magnetic topological insulator, provides a platform for the realization of various topological phases. Here we report the intermediate Hall steps in the magnetic hysteresis of $\mathrm{Mn}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{4}$, where four distinguishable magnetic memory states at zero magnetic field are revealed. The gate and temperature dependence of the magnetic intermediate states indicates the noncollinear spin structure in $\mathrm{Mn}{\mathrm{Bi}}_{2}{\mathrm{Te}}_{4}$, which can be attributed to the Dzyaloshinskii-Moriya interaction as the coexistence of strong spin-orbit coupling and local inversion symmetry breaking on the surface. Moreover, these multiple magnetic memory states can be programmatically switched among each other through applying designed pulses of magnetic field. Our results provide some insights of the influence of bulk topology on the magnetic states, and the multiple memory states should be promising for spintronic devices.