Abstract
We use neutron scattering to study the spin and lattice structure of single-crystal , the parent compound of the FeAs-based superconductor . We find that exhibits an abrupt structural phase transition at 220 K, where the structure changes from tetragonal with lattice parameters to orthorhombic with . At almost the same temperature, Fe spins develop a collinear antiferromagnetic structure along the orthorhombic axis with spin direction parallel to this axis. These results are consistent with earlier work on the ( earth) families of materials and on , and therefore suggest that static antiferromagnetic order is ubiquitous for the parent compounds of these FeAs-based high-transition temperature superconductors.
- Received 7 July 2008
DOI:https://doi.org/10.1103/PhysRevB.78.140504
©2008 American Physical Society