β-NaFeO2, a new room-temperature multiferroic material

‘Multiferroic’ materials possessing simultaneously magnetic and ferroelectric orders are scarce and most of them order at low temperatures. So far, bismuth ferrite, BiFeO3, is the only reliable room-temperature multiferroic: it is ferroelectric and antiferromagnetic. The absence of a net magnetisation in this compound is a problem when one wants to use the magneto-electric effect to address magnetic information with an electric field for potential applications in spintronic devices. We show here that β-NaFeO2 is also a multiferroic material at room-temperature but with the most interesting extra property of showing weak ferromagnetism. This makes it a potentially very promising material for applications and a model compound for fundamental studies of the interaction between ferroelectricity and magnetism.