Tuning superconductivity and magnetism by structure manipulation in intermetallic iron-pnictides
Johnpierre Paglione, MarylandCenter for Nanophysics and Advanced Materials, Department of Physics, University of Maryland
The relationship between superconductivity, magnetism and
crystallographic structure remains as one of the intriguing properties
of the new family of iron-based superconducting materials. A well
established requirement for high-temperature superconductivity in these
systems is a substructure of iron ions tetrahedrally coordinated with
either pnictogen or chalcogen anions stacked together to form a
layered material, suggesting that both tetrahedral geometry and
quasi-two-dimensionality are key ingredients. Through an investigation
of solid solutions of (Ba,Sr,Ca)Fe2As2 series of parent compounds, we
present a study of the importance of internal tetrahedral structure in
stabilizing both magnetic and superconducting ground states in these
materials, revealing an intimate relationship between the energy scale
that dictates magnetic order and the internal structure of the FeAs4
tetrahedra even far above the magnetic ordering temperature. In
addition, inter-layer coupling is investigated by exploiting the
"collapse" of the tetragonal unit cell of CaFe2As2 under pressure,
where inter-layer pnictogen-pnictogen bonding changes dramatically. We
investigate the effect of this collapse on superconductivity via
chemical substitution, demonstrating an intriguing interplay of
structure, magnetic and superconducting properties.