Magnetic ordering in RPtBi topological insulators from DFT+U calculations

We report on the detailed electronic properties of half Heusler compounds RPtBi (R=La, Gd, Lu). LDA+U predict an anti-ferromagnetic GdPtBi and nonmagnetic RPtBi (R=La, Lu) ground states, which are in agreement with the experiment. In this work, we also present a comparison between the electronic and magnetic properties provided by DFT and those computed by DFT+U in the Local Density Approximation (LDA), the Generalized Gradient Approximation (GGA) and the Modiffed Becke-Johnson functional (MBJ). In addition, we discuss our calculated band structures and show that the use of a Hubbard U parameter and the spin-orbit coupling (SOC) are critical to the accuracy of different properties of these half Heusler involving rare earth atoms. Since accurate determination of orbitals order, in particular, Γ6, Γ7, Γ8, is still a challenge, the theoretical approach (MBJ+U) presented here is certainly of a great help to predict the correct band sequence.