Les propriétés structurales, électroniques et magnétiques des matériaux monopnictogen à base de samarium SmX (X=N, P, As, Sb et Bi)

Abstract

In this study, we conducted an in-depth investigation of the structural, magnetic, and electronic properties of SmX compounds (X = N, P, As, Sb, Bi), a class of rare-earth pnictides, using the full-potential linearized augmented plane wave (FPLAPW) method as implemented in the WIEN2k code. Our calculations show that the NaCl-type structure is the most stable phase for all compounds. The equilibrium parameters obtained using the GGA- PBEsol approximation is in good agreement with available experimental and theoretical data. The bulk modulus analysis indicates decreasing stiffness with increasing pnictogen atomic number, with SmN being the least compressible and SmBi the most. A pressure-induced phase transition from NaCl to CsCl structure was identified for all compounds, with critical transition pressures decreasing from SmP to SmBi. Additionally, all SmX compounds exhibit a ferromagnetic ground state with a magnetic moment close to 5 μB, consistent with the presence of localized 4f electrons in samarium. The electronic structure, studied using both GGA and the modified Becke-Johnson (mBJ-GGA) potential, reveals that SmN exhibits half-metallic behavior, with a larger direct band gap obtained using mBJ-GGA. SmP and SmAs also show half-metallic character with moderate indirect gaps, while SmSb and SmBi transition from semi-metallic to half-metallic behavior when using mBJ-GGA instead of GGA. The band structure and density of states analysis highlight the dominant role of samarium 4f electrons near the Fermi level, especially in the majority-spin channel, leading to half-metallicity—metallic for majority spin and semiconducting for minority spin. Furthermore, strong hybridization between the pnictogen p- states and Sm f- and d-states contributes to the complex electronic behavior of these materials.