Electronic structure and magnetothermal properties of strongly-correlated compound NpB2 via first-principles and Monte Carlo study

Abstract

The electronic structure and magnetic properties of strongly-correlated compound neptunium boride (NpB2) were investigated by first-principles calculation together with Monte Carlo simulations. Our results showed that NpB2 can exist stably in terms of mechanical stability and thermodynamic stability. From the band structure and spin magnetic moment, it can be judged that the material exhibits obvious metallic properties, and the magnetism is mainly caused by the 5f orbitals of Np. We also provide a more detailed distribution of electrons by electron localization function. Through Monte Carlo simulation, we not only obtain the magnetic moment and magnetic susceptibility of NpB2 at different temperatures, but also found the competitive relationship between the crystal field (D) and magnetic field (h) in affecting the magnetothermal properties, where the critical temperature (TC = 116 K) is in good agreement with the experimental data. In addition, the magnetocrystalline anisotropy energy of NpB2 is calculated and the contributions of different orbitals to spin–orbit coupling (SOC) effect are provided. For relatively complex f orbitals, fx3 and fy3x2 orbitals are coupled to the greatest degree in the direction of the inner layer, while other f orbitals (such as fzx2 and fy3x2, fyz2 and fzx2, fxz2 and fz3) show a considerable degree of coupling outside the plane. Our work not only helps to understand the internal physical mechanism of NpB2, but also helps to explore the potential applications of such magnetic materials.