Does non-collinear ferromagnetism exist in INVAR?

Abstract Neutron scattering experiments with polarization analysis have been made on an FCC-FeNi INVAR alloy using the IN20 spectrometer at the Institut Laue-Langevin (I.L.L.), Grenoble. The magnitudes of the spin–flip cross sections and their constancy with temperature and magnetic field, over the measured Q range, mean that the magnetic moments must be collinear on atomic length scales. However, comparison with results from earlier, similar experiments on the D5 instrument at the I.L.L. suggest that non-collinear structures may exist over longer length scales.