R. A. Ewings

Nature of magnetic excitations in superconducting BaFe1.9Ni0.1As2

An outstanding question about the iron-based superconductors has been whether or not their magnetic characteristics are dominated by itinerant or localized magnetic moments. Absolute measurements and calculations of the magnetic response of undoped and Ni-doped BaFe2As2 indicate the latter.

Antiferromagnetic spin fluctuations in LiFeAs observed by neutron scattering

We report neutron inelastic scattering measurements on the stoichiometric iron-based superconductor LiFeAs. We find evidence for (i) magnetic scattering consistent with strong antiferromagnetic fluctuations, and (ii) an increase in intensity in the superconducting state at low energies, similar to the resonant magnetic excitation observed in other iron-based superconductors. The results do not support a recent theoretical prediction of spin-triplet p-wave superconductivity in LiFeAs, and instead suggest that the mechanism of superconductivity is similar to that in the other iron-based superconductors.

Itinerant spin excitations in SrFe2As2measured by inelastic neutron scattering

We report inelastic neutron scattering measurements of the magnetic excitations in SrFe2As2, the parent of a family of iron-based superconductors. The data extend throughout the Brillouin zone and up to energies of ~260meV. An analysis with the local-moment J_1-J2 model implies very different in-plane nearest-neighbor exchange parameters along the

Strong ( π , 0 ) spin fluctuations in β − FeSe observed by neutron spectroscopy

a

High-energy spin excitations in BaFe 2 As 2 observed by inelastic neutron scattering

and

Sample environment issues relevant to the acquisition of inelastic neutron scattering measurements of heterogeneous catalyst samples

b

Spin excitations used to probe the nature of exchange coupling in the magnetically ordered ground state of Pr 0.5 Ca 0.5 MnO 3

directions, both in the orthorhombic and tetragonal phases. However, the spectrum calculated from the J1-J2 model deviates significantly from our data. We show that the qualitative features that cannot be described by the J1-J2 model are readily explained by calculations from a 5-band itinerant mean-field model.

Spin resonance in the superconducting state ofLi1−xFexODFe1−ySeobserved by neutron spectroscopy

We have performed powder inelastic neutron scattering measurements on the unconventional superconductor

Magnetic excitation spectrum of LuFe2O4 measured with inelastic neutron scattering

\beta

The application of inelastic neutron scattering to explore the significance of a magnetic transition in an iron based Fischer-Tropsch catalyst that is active for the hydrogenation of CO

-FeSe (