In this works, we study the electronic structure and magnetic properties of the Pr-Ni-Bi half-Heusler systems based on density functional theory. We use the σ GGA + U scheme to consider the effects of on-site electron-electron interactions. Results show that in contrast to the rough estimation of the total magnetic moment of the unit cell, based on the Slater-Pauling behavior in the half-Heusler systems, this system has an antiferromagnetic ground state because of the localized Pr-f electrons. By increasing the magnitude of the effective U parameter, band-inversion occurs in the band structure of this system, which shows the possibility of topological state occurrence.

First principles calculations have been performed for the Ni2Co1-xFexGa Heusler compound in order to investigate the nature of structural instability and the effect of iron doping in enhancing the magneto-structural properties. Calculations show that the origin of structural instability is based on the Jahn-Teller mechanism. Based on the obtained results, the structural instability decreases by iron doping, nevertheless, it is expected that the structural phase transition temperature be always higher than the room temperature. Also, the results show that iron doping enhances the Curie temperature by enhancing the exchange interactions in these compounds. These suggest that the iron doping improves the overall magneto-mechanical properties of the Ni2CoGa Heusler compound.

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