Abstract
We use inelastic neutron scattering (INS) spectroscopy to study the magnetic excitations spectra throughout the Brillouin zone in electron-doped iron pnictide superconductors BaFeNiAs with . While the sample is near optimal superconductivity with K and has coexisting static incommensurate magnetic order, the samples are electron overdoped with reduced of 14 and 8 K, respectively, and have no static antiferromagnetic (AF) order. In previous INS work on undoped () and electron optimally doped () samples, the effect of electron doping was found to modify spin waves in the parent compound BaFeAs below 100 meV and induce a neutron spin resonance at the commensurate AF ordering wave vector that couples with superconductivity. While the new data collected on the sample confirm the overall features of the earlier work, our careful temperature dependent study of the resonance reveals that the resonance suddenly changes its width below similar to that of the optimally hole-doped iron pnictides BaKFeAs. In addition, we establish the dispersion of the resonance and find it to change from commensurate to transversely incommensurate with increasing energy. Upon further electron doping to overdoped iron pnictides with and 0.18, the resonance becomes weaker and transversely incommensurate at all energies, while spin excitations above 100 meV are still not much affected. Our absolute spin excitation intensity measurements throughout the Brillouin zone for confirm the notion that the low-energy spin excitation coupling with itinerant electron is important for superconductivity in these materials, even though the high-energy spin excitations are weakly doping dependent.
9 More- Received 14 August 2013
DOI:https://doi.org/10.1103/PhysRevB.88.144516
©2013 American Physical Society