Chemical bonding, electronic, and magnetic properties ofR3Co4Sn13intermetallics (R=La, Ce, Sm, Gd, and Tb): Density functional calculations

Abstract

The structural, electronic, and magnetic properties in the intermetallic compounds, R3Co4Sn13 R = La, Ce, Sm, Gd, and Tb, have been investigated by performing density functional theory DFT and DFT+U calculations. The stability, bonding character, charge density, total and partial density of states, and band structure, as well as Fermi-surface feature, were analyzed. In particular, we clearly present the 4f electronic characters in these series. The antibonding states formed by Co 3d and Sn 5p play an important role in the superconductivity of La3Co4Sn13 .4 f electrons exhibit itinerancy and strongly couple with conduction electron, and these properties show strong dependence on the U parameter in the Ce compound. On the contrary, 4f electrons are fully localized at the deep energy level, and their energies do not change with the U parameter in the Gd compound. In Sm and Tb compounds, localization and itinerancy of 4f electrons coexist. In these compounds, magnetism mainly results from 4f electrons, while Co and Sn atoms hardly contribute a magnetic moment because of their sublattice structure and covalent interaction. Comparably, La compound is a nonmagnetic superconductor with the competition between superconductivity and magnetism. Ce3Co4Sn13 is a weak itinerant ferromagnetic metal with a semimetallic behavior. The antiferromagnetic ordering exists in Gd compound. Both Sm3Co4Sn13 and Tb3Co4Sn13 are ferromagnetic metals. The trivalent charge state of rare-earth ions is suggested in these compounds.