Effects of transition metal substitutions on the incommensurability and spin fluctuations in BaFe2As2 by elastic and inelastic neutron scattering

摘要

The spin fluctuation spectra from nonsuperconducting Cu-substituted, andsuperconducting Co-substituted, BaFe2As2 are compared quantitatively byinelastic neutron scattering measurements and are found to be indis-tinguishable. Whereas diffraction studies show the appearance of incommensuratespin-density wave order in Co and Ni substituted samples, the magnetic phasediagram for Cu substitution does not display incommensu- rate order,demonstrating that simple electron counting based on rigid-band concepts isinvalid. These results, supported by theoretical calculations, suggest thatsubstitutional impurity effects in the Fe plane play a signifi- cant role incontrolling magnetism and the appearance of superconductivity, with Cudistinguished by enhanced impurity scattering and split-band behavior.