Abstract
Coexistence of the ferroelectric polarization and spontaneous magnetization has been found in Y-type hexaferrite Ba2Mg2Fe12O22. The reversal of magnetization by a small magnetic field below ∼0.02 T accompanies an electric polarization reversal through the clamping of ferrimagnetic and ferroelectric domain walls. This behavior can be potentially used as a magnetically rewritable ferroelectric memory and an electrically rewritable magnetic memory.