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.

• Received 21 May 1954

DOI:https://doi.org/10.1103/PhysRev.95.1161