Just like the cuprate superconductors, they are formed by doping a layered parent material, and there is strong evidence that magnetism has a central role in the mechanism responsible for the superconductivity. There are, however, many differences, and researchers are using a gamut of experimental probes to unravel the origins of the superconductivity in these materials.

Experiments performed at ISIS are making a significant impact. Muon measurements from SmFeAsO_1-xF_x showed enhanced magnetic fluctuations near the superconducting transition, and have revealed a region of coexisting superconductivity and iron magnetism. The existence of a magnetic resonance that appears only in the superconducting phase of Ba_0.6K_0.4Fe₂As₂, one of another family of iron pnictides, and which is strongly reminiscent of the cuprate superconductors, was discovered on Merlin. The bandwidth of the spin fluctuations of parent materials BaFe₂As₂ and CaFe₂As₂ have been measured on Merlin and Maps, revealing excitations that extend to almost 200 meV. Such measurements help in enabling a detailed model of the magnetic behaviour to be produced. Finally, examples of structural studies are those on the oxygen-free iron pnictides LiFeAs and NaFeAs, which show superconductivity without doping.

​Research date: September 2009

Further Information

Further reading: A Christianson et al., Nature 456 (2008) 930; RA Ewings et al., Phys Rev B 78 (2008) 220501(R); J Zhao et al., Nature Physics 5 (2009) 555; S Diallo et al., Phys Rev Lett 102 (2009) 187206; AJ Drew et al., Nature Materials 8 (2009) 310; MJ Pitcher et al., Chem Comm. 2008 5918; DR Parker et al., Chem Comm (2009) 2189