Reduced iron ordered moment and negative T<Subscript>C</Subscript>-pressure coefficient in iron-arsenide superconductors

The striped antiferromagnetic phase of iron-arsenides is investigated by the density functional calculations including Coulomb repulsion. Two low moment solutions with m ≈ 0.4 μ <Subscript> B </Subscript> and m ≈ 1.0 μ <Subscript> B </Subscript> have been found from calculations. The electronic structures indicate that the low moment states originate in the strong orbital hybridization between antiferromagnetic Fe neighbors. Therefore, the geometry of FeAs<Subscript>4</Subscript> tetrahedron, which is characterized by a parameter of h <Subscript>As</Subscript>/a, is crucial to the low moment states. We show that the puzzling negative T <Subscript> C </Subscript>-pressure coefficient of iron-arsenides can be consistently explained by the obtained low moment states. Copyright EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg 2015