The spin-flip cross-sections of two samples each of Fe90Zr10 and Fe92Zr8 produced in two different laboratories were measured using the polarized neutron spectrometers IN20 and D7 at the Institut Laue-Langevin, Grenoble. All the samples have non-zero spin-flip cross-sections, with peaks at Q ~ 3.1Å−1, coinciding with the first maximum in the structure factor S(Q), on a diffuse Q-dependent 'background'. The features change little on cooling to 2 K and persist above the Curie temperature. The samples are therefore all non-collinear ferromagnets, with significant ferromagnetic correlations between the non-collinear components of the moments. The compositions of the samples were shown to be correct to ≤ 0.1at.% by magnetic susceptibility measurements. The 'background' was found to be significantly larger in the spin-flip cross-sections of one set of the samples. Careful examination of neutron diffraction data measured using the LAD diffractometer, Rutherford Appleton Laboratory, showed that these samples had barely detectable impurities of α-Fe. The critical re-evaluation of previous data is therefore necessary as experimental results are evidently influenced by very low levels of crystalline impurities that are difficult to detect.