Carr, Scott V.Zhang, ChenglinSong, YuTan, GuotaiLi, YuAbernathy, D.L.Stone, M.B.Granroth, G.E.Perring, T.G.Dai, Pengcheng2017-08-212017-08-212016Carr, Scott V., Zhang, Chenglin, Song, Yu, et al.. "Electron doping evolution of the magnetic excitations in NaFe1−xCoxAs." <i>Physical Review B,</i> 93, no. 21 (2016) American Physical Society: https://doi.org/10.1103/PhysRevB.93.214506.https://hdl.handle.net/1911/97370We use time-of-flight (TOF) inelastic-neutron-scattering (INS) spectroscopy to investigate the doping dependence of magnetic excitations across the phase diagram of NaFe 1 − x Co x As with x = 0 , 0.0175, 0.0215, 0.05, and 0.11 . The effect of electron doping by partially substituting Fe by Co is to form resonances that couple with superconductivity, broaden, and suppress low-energy ( E ≤ 80 meV) spin excitations compared with spin waves in undoped NaFeAs. However, high-energy ( E > 80 meV) spin excitations are weakly Co-doping-dependent. Integration of the local spin dynamic susceptibility χ ' ' ( ω ) of NaFe 1 − x Co x As reveals a total fluctuating moment of 3.6 μ 2 B /Fe and a small but systematic reduction with electron doping. The presence of a large spin gap in Co-overdoped nonsuperconducting NaFe 0.89 Co 0.11 As suggests that Fermi surface nesting is responsible for low-energy spin excitations. These results parallel the Ni-doping evolution of spin excitations in BaFe 2 − x Ni x As 2 in spite of the differences in crystal structures and Fermi surface evolution in these two families of iron pnictides, thus confirming the notion that low-energy spin excitations coupling with itinerant electrons are important for superconductivity, while weakly doping-dependent high-energy spin excitations result from localized moments.engArticle is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.Journal articleElectron_doping_evolutionhttps://doi.org/10.1103/PhysRevB.93.214506