Credit: Image courtesy of Argonne National Laboratory
Neutron diffraction data of barium iron arsenide with sodium ions substituted onto 24 percent of the barium sites (doping) showed evidence for a new magnetic phase in iron-based superconductors. The atomic and magnetic structures of the material are temperature-dependent. Upon cooling, the structures exhibit three distinct structural states: high temperature disordered – top right; magnetic nematic phase – middle right; magnetic four-fold phase – bottom right. In the schematic illustration (right side), the blue spheres represent iron atoms and the red arrows show the direction of their magnetic moments.