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Alan I. Goldman - Iowa State University, Ames, USA

Magnetic order and magnetic fluctuations in the (122) iron-arsenides


The relationships between magnetic order, magnetic fluctuations and superconductivity
in the iron-based superconductors remain an important focus of investigations using both elastic
and inelastic neutron scattering. Detailed neutron scattering investigations of the AFe2As2 (A =
Ca, Sr, Ba) parent compounds and the A(Fe1-xTMx)2As2 (TM = Transition Metal) superconductors
have shed some light on these relationships, although many issues and questions remain to be
resolved. Some of these issues include the origin of the antiferromagnetic ordering (Fermi surface
nesting vs. localized moment vs. aspects of both), the origin and role of paramagnetic spin
fluctuations found at the stripe magnetic ordering wave vector, the role and importance of
impurity scattering effects, and the importance of electron correlations for magnetism and
superconductivity. Here I will discuss how elastic and inelastic neutron scattering measurements
on the AFe2As2, A(Fe1-xTMx)2As2, and, most recently, the closely related ACo2As2 compounds
have both enlightened us and presented some new puzzles to consider in the field of iron-based
superconductivity.