Magnetic Reversal of the Ferroelectric Polarization in a Multiferroic Spinel Oxide

Ferroelectric transition has been detected in a ferrimagnetic spinel oxide of CoCr2O4 upon the transition to the conical spin order below 25 K. The direction 110 of the spontaneous polarization is normal to both the magnetization easy axis 001 and to the propagation axis 110 of the transverse spiral component, in accord with the prediction based on the spin-current model. The reversal of the spontaneous magnetization by a small magnetic field (approximately 0.1 T) induces the reversal of the spontaneous polarization, indicating the clamping of the ferromagnetic and ferroelectric domain walls.