First-principles study of electronic structure and magnetic properties of orthorhombic CrGa2Sb2 and MnGa2Sb2

Abstract

By the first-principles calculations, we present the results of electronic structure and magnetic properties on bulk CrGa2Sb2 and MnGa2Sb2 in an orthorhombic structure with the linear chains of transition-metal Cr and Mn atoms, using four different exchange correlation potentials: the local density approximation (LDA), the generalized gradient approximation (GGA), GGA + U, and the Tran-Blaha modified Becke-Johnson functional (mBJ). The electronic structure calculations from four exchange correlation potentials show that CrGa2Sb2 is a pseudogap (negative gap) material with very small density of states (DOS) at the Fermi level, while MnGa2Sb2 has notably higher DOS at the Fermi level compared to CrGa2Sb2, exhibiting stronger metallic conductivity, although the mBJ potential obtains lower DOS at the Fermi level than LDA and GGA for both CrGa2Sb2 and MnGa2Sb2. The GGA + U method with a small value (1 eV) of the on-site Coulomb interaction parameter U obtains lower DOS at the Fermi level compared to the large value of U. In agreement with the measurement data, the total energy calculations reveal that both CrGa2Sb2 and MnGa2Sb2 have a stable ferromagnetic ground state with lower energies relative to antiferromagnetic state. Based on the Heisenberg model, the magnetic exchange constants between the nearest-neighbor Cr–Cr and Mn–Mn along transition-metal linear chains are calculated to be 48.6 meV and 27.5 meV for CrGa2Sb2 and MnGa2Sb2, respectively. By the mean-field approximation method, we calculated the Curie temperature of two compounds to be above room-temperature.