Transport and Magnetic Properties of MnSb₂Te₄ Ferromagnetic Layers Grown by MBE

The interaction between magnetic impurities and topological electronic states of 3D topological insulators (TIs) has attracted many studies of predicted exotic phenomena, including quantum anomalous hall effect. In the presence of magnetic dopants, time-reversal symmetry is broken and promotes a Dirac gap. Incorporation of Mn in Sb₂Te₃ results in the formation of a new crystal structure, MnSb₂Te₄, with septuple layer units rather than typical quintuple layers of the undoped TIs. However, high bulk conductivity, due largely to anti-site defects, is pervasive in these materials and limits the ability to detect the surface states and their possible applications. This led to developing new growth procedures of MnSb₂Te₄ that reduce the bulk conductivity. Here we will compare the transport properties, obtained from Hall Effect, of MnSb₂Te₄:Sb₂Te₃ grown by molecular beam epitaxy with varying Mn content, and compare them to first-principle calculations. We use first principle calculations to understand the scattering mechanisms that control the bulk conductivity in the materials, as well as the magnetic spin interactions and magnetic exchange mechanisms that promote topological phase transitions in samples with high Curie temperature values.