Magnetoelectric Effect of Fe3O4 at 77 K. II. Electric Field Dependence of Magnetic Anisotropy

Anisotropy and external magnetic field dependence of the magnetoelectric effect in Fe 3 O 4 was measured at 77 K and analysed. It was concluded that a tilting of the magnetization due to a change in the magnetic anisotropy, by the application of the electric field, is a dominant mechanism, though a possibility of a non-tilting mechanism was not excluded. The main part of the magnetic anisotropy accompanied by electric polarization, which has mirror symmetry parallel to the b plane, was analysed by spherical harmonics up to the fourth order and eight constants were determined. This polarization dependent part was much smaller than the total magnetic anisotropy energy. Direction of the spontaneous electric polarization was estimated as -15° from [111] or +19° from [112] within the b plane.