Magnetic Neutron Diffraction fromFe3O4

Abstract

By neutron diffraction intensity measurements, the spin alignment structure has been studied from the room temperature to above the Curie point in an unmagnetized (random domain orientation) crystal of ${\mathrm{Fe}}_3$ ${\mathrm{O}}_4$. Intrinsic magnetization is found to follow approximately the Weiss theory and to go to zero at a sharply defined Curie point, where domain structure disappears. An additional diffuse component of the magnetic Bragg peaks is observed to be independent of external fields and indicates transient short-range ordering of spins, which reaches a sharp maximum at the Curie point but exists at both higher and lower temperatures.