Lattice and Magnetic structures of PrFeAsO, PrFeAsO0.85F0.15 and   PrFeAsO0.85
  We use powder neutron diffraction to study the spin and lattice structures of polycrystalline samples of nonsuperconducting PrFeAsO and superconducting PrFeAsO0.85F0.15 and PrFeAsO0.85. We find that PrFeAsO exhibits an abrupt structural phase transitions at 153 K, followed by static long range antiferromagnetic order at 127 K. Both the structural distortion and magnetic order are identical to other rare-earth oxypnictides. Electron-doping the system with either Fluorine or oxygen deficiency suppresses the structural distortion and static long range antiferromagnetic order, therefore placing these materials into the same class of FeAs-based superconductors. 
Jun Zhao, Q. Huang, Clarina de la Cruz, J. W. Lynn, M. D. Lumsden, Z.   A. Ren, Jie Yang, Xiaolin Shen, Xiaoli Dong, Zhongxi...