Interplay of anomalous Hall angle and magnetic anisotropy in ferromagnetic topological crystalline insulators

An interplay of conservation and breaking of local and global symmetries in topological phases of matter leads to the emergence of topological phenomena including quantum anomalous (QAH) Hall effect, topological superconductivity, and non-Abelian quantum statistics. Among the members of the family of topological materials, magnetically doped topological crystalline insulators (TCI) were foreseen to host topologically protected QAH states generating multiple dissipationless edge and surface conduction channels with Chern number C ≥1. The symmetry protected topological phase of the SnTe class of TCI is characterized by a mirror symmetry resulting in topological surface states. Theoretical and experimental studies demonstrated that four Dirac points are located at the time-reversed-invariant-momentum (TRIM) points for the (111) surface of the SnTe compounds. In this work, via low temperature magnetotransport studies, the opening of the gaps at the TRIMs is demonstrated in ferromagnetic 30 nm thick Sn1-xMnxTe (111) thin epitaxial layers grown onto BaF2(111) substrates by molecular beam epitaxy. While a spin mediated magnetoconductance is observed in layers with 𝑥 ≥ 0.03, the appearance of hysteretic magnetoconductance behaviour and square-like anomalous Hall effect indicate the onset of a hole mediated ferromagnetic ordering in epitaxial Sn1-xMnxTe (111) layers for 𝑥 ≥ 0.06. The anomalous Hall angle, 𝜃AH~0.3 estimated for Sn0.92Mn0.08Te is one of the highest recorded for magnetic topological quantum materials. The tuning of the global band topology by magnetic doping opens wide perspectives for topology driven quantum spintronic technology.