Pengcheng Dai, University of Tennessee, USA, and co-workers have used neutron scattering analysis to study two families of iron-based superconductors. They show that spin waves in the iron chalcogenide Fe_1.05Te display dispersions different from those in the related iron pnictide CaFe₂As₂. However, even though the nearest neighbor exchange couplings between chalcogenide and pnictide atoms are different, the next nearest neighbor exchange couplings are similar. This implies that the key magnetic exchange thought to be responsible for high temperature superconductivity may occur here rather than in adjacent atoms as predicted by first principles density functional calculations.

Iron-based superconductors have been studied since their discovery in 2008 to see if the dynamics of their high-temperature superconducting properties could help explain what was thought to be exclusive to copper-oxide-based superconductors.

• Spin Waves in the (π,0) Magnetically Ordered Iron Chalcogenide Fe_1.05Te
  O. Lipscombe, G. F. Chen, C. Fang, T. G. Perring, D. L. Abernathy, A. D. Christianson, T. Egami, N. Wang, J. Hu, P. Dai,
  Phys. Rev. Lett. 2011, 106, 057004.
  DOI: 10.1103/PhysRevLett.106.057004