Magnetoelectric Effect of Fe3O4 at 77 K. I. Crystal Symmetry

Magnetoelectric effect of the low temperature phase of magnetite was measured at 77 K. It was confirmed that the magnetic crystal symmetry at 77 K is triclinic but the breaking of the mirror symmetry parallel to the (110) plane is very small. Dispersion of the magnetoelectric effect was observed with the relaxation time of approximately 2 µs. Magnitude of magnetoelectric susceptibility depends on the direction of the applied electric field. Both phenomena were attributed to the dispersion and the anisotropy of the electric susceptibility. The structure of the low temperature phase was discussed briefly in connection with the model proposed by Mizoguchi (J. Phys. Soc. Jpn. 44 (1978) 1512).