Fig. 2: Neutron scattering from PrAlGe.

a PND profiles obtained at DMC from PrAlGe at base T = 1.6 K below T_c, and at 20 K above T_c. Blue ticks denote the expected positions for nuclear peaks in the I4₁md space group. The inset shows a zoom of the {101} peak. b Refinement of the profile measured at T = 1.6 K (black line). The dark grey line shows the difference between the refined model profile and the data. The blue ticks denote the expected positions for nuclear peaks, and the green ticks denote possible positions for magnetic peaks according to the magnetic structure model. In both a and b, positions due to certain scattering planes are labelled. In b, * denotes scattering planes only allowed according to magnetic symmetry, the absence of intensity at the labelled peaks implies directly that the magnetic moments are aligned along c. The good profile refinement using fixed diffraction peak profile and shape parameters (see Methods) indicates the main scattering peak profiles are close to resolution-limited. SANS patterns obtained from PrAlGe at 1.9 K in c µ₀H = 0, and d µ₀H = 0.3 T, each after ZFC. A square beamstop is placed at the centre of the reciprocal space q = 0 to protect the detector from saturation due to the unscattered beam. The [001] axis is out of the page, and the [100] axis horizontal. Contour lines are plotted in steps of 0.5 on the logarithmic intensity scale, with the highest intensity contour drawn for Log Intensity = 4.5 counts per standard monitor (Cts./per Std. Monitor). e The log-log plot of the azimuthal-averaged SANS intensity versus |q| as a function of T in µ₀H = 0. The solid lines are fits of the data according to the model described in the text and the Supplementary Note 3. f The total magnetic scattering contribution to the SANS profiles shown in e as a function of T in µ₀H = 0. The solid line is a power law fit. g A µ₀H -increasing scan of the magnetic SANS intensity at 1.9 K. In panels a, b, e, f, g, error bars indicating the statistical error are smaller than the symbol size.