Tuning the magnetic character and exchange interaction of intrinsic magnetic topological insulators

The recent prediction and experimental confirmation of intrinsic magnetism in the van der Waals (vdW) layered MnBi2Te4 family of topological insulators (TIs) has attracted great attention in the condensed matter community. The interest arises from the interplay between magnetism and topology, which is a key ingredient for the observation of exotic phenomena such as the quantum anomalous Hall effect (QAHE). However, MnBi2Te4 is antiferromagnetic and tends to be n-doped, which is detrimental for transport experiment and zero-magnetic field observation of the QAHE. On the other hand, MnSbi2Te4 is ferromagnetic and p-doped, although there is still debate whether it is topologically trivial or not. We propose to perform a systematic and detailed study of the magnetic interactions and anisotropy in Mn(Bi1-xSbx)2Te4 thin films, grown by molecular beam epitaxy, as a function of Sb concentration (x) using x-ray absorption spectroscopy (XAS). The element and crystal-site selectivity nature of XAS, x-ray magnetic circular dichroism and x-ray magnetic linear dichroism techniques will allow us to extract unparalleled magnetic information that is fundamental for the understanding of the topological properties of this unexplored family of vdW materials. This study will provide a map of their magnetic phase diagram, which, together with magneto-transport measurements, will be a step forward towards the demonstration of the QAHE in intrinsic magnetic TIs that incorporate Sb, have ferromagnetic order and are charge neutral.