Itinerant Nature of Magnetism in Iron Pnictides: A first principles study*

The magnetic properties of LaFe$Pn$O, BaFe$_2Pn_2$ and LiFe$Pn$ ($Pn$ = As, Sb) are investigated by using {\it ab initio} molecular dynamics based on an all-electron projector-augmented wave basis. We find that stripe-type antiferromagnetic orderings are always enhanced when As is substituted by Sb. Our calculated Pauli susceptibility strongly points towards an itinerant picture of magnetism. Furthermore, we study the lattice properties of LaFe$Pn$O ($Pn$=P, As, Sb, Bi) as well as ScFePO, ScFeAsO and YFePO and argue that LaFeSbO would be a candidate for a superconductor with highest transition temperature among the investigated compounds.