Multiferroic Iron Oxide Thin Films at Room-Temperature

TL;DR

This paper reports the stabilization of epsilon-Fe2O3 thin films that exhibit both ferrimagnetism and ferroelectricity at room temperature, making it a promising single-phase multiferroic material for device applications.

Contribution

It introduces a method to stabilize epsilon-Fe2O3 in thin film form and demonstrates its dual ferroic properties at room temperature, a novel achievement.

Findings

Epsilon-Fe2O3 thin films are ferrimagnetic and ferroelectric at 300 K.

The films have a remanent polarization of 1 microC/cm2.

The polarization can be switched with small voltages.

Abstract

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.