Electronic structure and magnetism of layered compounds SrBO2 (B = Ni, Co, Mn): A theoretical investigation

We investigate the electronic structure and magnetic properties of layered compounds SrBO2 (B = Co, Ni, Mn) based on first principles calculations in the framework of density functional theory with GGA+U method. We compute the phonon dispersion of these compounds to probe the dynamical stability and find that all the compounds are dynamically stable. SrCoO2 and SrNiO2 are G-type antiferromagnetic insulators, and SrMnO2 is an A-type antiferromagnetic conductor. The electronic configurations of 3d orbitals are (dxz)2(dz2)2(dyz)1(dxy)1(dx2-y2)1 and (dxz)2(dyz)2(dz2)2(dxy)1(dx2-y2)1 in SrCoO2 and SrNiO2, respectively. SrCoO2 shows a Jahn-Teller distortion (a>b) because the down-spin Co 3d electron occupies the degenerate (dxz, dyz) levels. Using Monte Carlo simulations based on the Heisenberg model with exchange parameters obtained from first principles calculations, we obtain the Néel temperatures (TN) of SrCoO2 and SrNiO2, which are 249 K and 85 K, respectively.