Doping-dependent phase diagram of LaOMAs (M=V-Cu) and electron-type superconductivity near ferromagnetic instability

By first-principles calculations, we present a doping-dependent phase diagram of the LaOMAs (M=V-Cu) family. It is characterized as a antiferromagnetic semiconductor around the LaOMnAs side and as a ferromagnetic metal around LaOCoAs. Both LaOFeAs and LaONiAs, where superconductivity were discovered, are located at the borderline of magnetic phases. An extensive Fermi surface analysis suggests that the observed superconductivity is of electron type in its origin. We discuss possible pairing mechanisms in the context of competing ferromagnetic phases found in this work and the ferromagnetic spin fluctuations.