The doping of nonmagnetic topological insulators with magnetic transition metal elements exhibits less desired strongly inhomogeneous magnetic and electronic properties, which restricts the observation of important effects to very low temperatures. Well ordered intrinsic magnetic topological insulators can be the solution to those problems as they show higher magnetic phase transition temperatures as theoretically predicted and experimentally confirmed for the antiferromagnetic (AFM) topological insulator MnBi2Te4. Here, we report about the ab initio results and calculated magnetic properties of this prediction. MnBi2Te4 forms septuple-layer blocks including a Mn layer. A three-dimensional AFM order establishes below the Néel temperature of 25.4 K obtained by Monte Carlo simulations. This AFM order causes the different Mn layer to align their moments antiparallel due to weak out-of-plane magnetic exchange coupling constants, while the intralayer magnetic order is ferromagnetic.
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