  In spite of being highly relevant for the development of a new generation of
information storage devices, not many single-phase materials displaying
magnetic and ferroelectric orders above room temperature are known. Moreover,
these uncommon materials typically display insignificant values of the remanent
moment in one of the ferroic orders or are complex multicomponent oxides which
will be very challenging to integrate in devices. Here we report on the
strategy to stabilize the metastable epsilon-Fe2O3 in thin film form, and we
show that besides its already known ferrimagnetic nature, the films are also
ferroelectric at 300 K with a remanent polarization of 1 microC/cm2. The film
polarization shows long retention times and can be switched under small applied
voltages. These characteristics make of epsilon-Fe2O3 the first single-ion
transition-metal oxide which is ferro(ferri)magnetic and ferroelectric at room
temperature. The simple composition of this new multiferroic oxide and the
discovery of a robust path for its thin film growth may boost the exploitation
of epsilon-Fe2O3 in novel devices.
