Transport and tunneling studies of ferromagnetic Mn(Bi,Sb)₆Te₁₀

Two-dimensional van der Waals magnets with topological phases can host novel quantum states. For example, combining a topological insulator, Bi₂Te₃, with magnetism into a single crystal provides a tunable platform to study the quantum anomalous Hall effect and the axion insulator state. In this work, we synthesize Mn(Bi,Sb)₆Te₁₀ crystals with a ferromagnetic ground state and study exfoliated sheets of several tens of nm in thickness using Hall bar and tunnel junction structures prepared inside a glovebox. In transport, we observed a clear Curie temperature of ~ 11 K and a coercive field of ~ 0.02 T at 2 K, in agreement with bulk measurements. We build vertical tunnel junctions of Mn(Bi_0.88,Sb_0.18)₆Te₁₀ using a graphite electrode, a thin h-BN barrier and the dry transfer method to probe the density of states of the sample surface. We observe suppressed differential tunneling conductance in a small range of biases (~ 15 mV) near V_dc = 0, which disappears at elevated temperatures. This is reminiscent of a magnetic exchange gap observed in ARPES measurements (Yan et al, axiv:2107.08137v1). The tunneling spectra evolve with a perpendicular magnetic field, showing a number of intriguing features. We discuss possible interpretations and the implications on the band structure and magnetism in Mn(Bi,Sb)₆Te₁₀.