Temperature Variation of Saturation Magnetization of Gamma-Ferric Oxide

The temperature variation of the saturation magnetization of a γ-ferric oxide sample has been interpreted by use of Néel's molecular-field model, with neglect of A-A and B-B interactions. The parameters assumed are: j of the Brillouin function= 52; a net moment of 1.25 Bohr magnetons per iron atom; ratio of the number of atoms on A sites to the number on B sites, 8/(40/3)=3/5. From these parameters the function M/M∞=G(T/θ) was calculated numerically; M=magnetization at temperature T, M∞=magnetization at T=0, θ=Curie temperature. The data fit the theoretical curve very well if θ is assigned the value 1020°K.