Abstract
We report on the detailed electronic properties of half Heusler compounds RPtBi (R¼La, Gd, Lu). LDA+U predict an anti-ferromagnetic GdPtBi and nonmagnetic RPtBi (R¼La, 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 (MBJþU) presented here is certainly of a great help to predict the correct band sequence
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In order to describe the electronic structure of the different magnetic configurations of R ions, we have constructed the three kinds of independent spin configurations shown in Fig. 1, including AF-I, AF-II and AF-III states. In the case of FM state all R ion spins are oriented along c-axis direction. Our purpose is to address the ability of the value of the effective coulomb interaction Ueff to reproduce experimental results. First, we have studied the magnetic stability of RPtBi materials versus the effective coulomb interaction using the LDAþU approach (Fig. 2a). This approximation corrects the deficiencies of the LDA, and reproduces very well the experimental values. The anti-ferromagnetic state (AF-I) indeed yields the lowest energy for GdPtBi compared to the AF-II, AF-III and FM configurations (see Fig. 2b), and the paramagnetic state should be most appropriate to both the compounds LaPtBi and LuPtBi. Our results are in excellent agreement with experience [13,14,16].
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