Neutron Diffraction Determination of Antiferromagnetism in Face-Centered Cubic (γ) Iron

Microcrystalline particles of γ iron of nearly identical orientation in a single-crystal copper matrix give a neutron diffraction pattern, in the liquid helium temperature range, consistent with the development of antiferromagnetism. The spin structure resembles that of γ manganese, but with the spin vectors inclined at about 19^∘{} from the normal to the ferromagnetic sheets. The spin directions in alternate sheets are antiparallel. The moment per iron atom is about 0.7 μB and the N\'eel temperature, estimated from the Brillouin function temperature dependence of the magnetic intensities, is about 8^∘{}K.