Fig. 3

Neutron diffraction and neutron Larmor diffraction studies of Ni-doping dependence of the orthorhombic distortion in NaFe_1−xNi_xAs. Temperature dependence of the orthorhombic distortion δ for NaFe_1−xNi_xAs with (a) x = 0.01, (b) x = 0.012, (c) x = 0.013, (d) x = 0.015, (e) x = 0.017, and (f) x = 0.02. Data in (b) are obtained from high-resolution neutron diffraction, whereas all the other panels are obtained from neutron Larmor diffraction measurements. Solid lines are guides to the eye. δ is obtained by assuming that it is 0 at T = 50 K, and broadening at lower temperatures are fit with two split peaks, with widths of the single peak at T = 50 K. Open symbols correspond to measurements where a splitting is definitively observed, and solid symbols represent measurements that only resolve a broadening due to experimental limitations (Methods section and Supplementary Fig. 4). All vertical error bars in the figure represent least-square fits to the raw data with errors of 1 s.d