Single crystal neutron diffraction is used to investigate the magnetic and structural phase diagram of the electron doped superconductor Ba(Fe1−xCox)2As2. Heat capacity and resistivity measurements have demonstrated that Co doping this system splits the combined antiferromagnetic and structural transition present in BaFe2As2 into two distinct transitions. For x=0.025, we find that the upper transition is between the high-temperature tetragonal and low-temperature orthorhombic structures with (TTO=99±0.5 K) and the antiferromagnetic transition occurs at TAF=93±0.5 K. We find that doping rapidly suppresses the antiferromagnetism, with antiferromagnetic order disappearing at x≈0.055. However, there is a region of co-existence of antiferromagnetism and superconductivity. The effect of the antiferromagnetic transition can be seen in the temperature dependence of the structural Bragg peaks from both neutron scattering and x-ray diffraction. We infer from this that there is strong coupling between the antiferromagnetism and the crystal lattice.
@article{arxiv.0903.3560,
title = {A neutron scattering study of the interplay between structure and magnetism in Ba(Fe$_{1-x}$Co$_{x}$)$_2$As$_2$},
author = {C. Lester and Jiun-Haw Chu and J. G. Analytis and S. Capelli and A. S. Erickson and C. L. Condron and M. F. Toney and I. R. Fisher and S. M. Hayden},
journal= {arXiv preprint arXiv:0903.3560},
year = {2009}
}