Competing magnetic ground states in nonsuperconducting Ba(Fe _1-xCr_x)₂As₂ as seen via neutron diffraction

We present neutron diffraction measurements on single-crystal samples of nonsuperconducting Ba(Fe_1-xCr_x)₂As₂ as a function of Cr doping for 0≤x≤0.47. The average spin-density-wave moment is independent of concentration for x≤0.2 and decreases rapidly for x≥0.3. For concentrations in excess of 30% chromium, we find a new competing magnetic phase consistent with G-type antiferromagnetism which rapidly becomes the dominant magnetic ground state. Strong magnetism is observed for all concentrations measured, naturally explaining the absence of superconductivity in the Cr-doped materials.