A note on the magnetic anisotropy of Fe3O4

Abstract Effect of the low temperature transition of Fe 3 O 4 on its magnetocrystalline anisotropy is discussed. Above the transition point, T v , it is argued that the short-range order of ions or atomic displacements, which becomes long range below T v , changes with the direction of the magnetization because of the magnetic anisotropy energy. To explain the extraordinary part of the cubic anisotropy above T v , the principal axis of the unit of the ordering must be If such a unit is not only magnetically but also elastically anisotropic, anomalies are expected in the magnetostriction and the elastic constants in the cubic phase. Experimental results on these are consistently interpreted on an assumption that the principal axes of the unit are, e.g., [001], [110] and [1 1 0].