Origin of ferroelectricity in multiferroic ErFeO3

ErFeO3 is a centrosymmetric Pnma/Pbnm structure with no ferroelectricity. However, most surprisingly, it shows ferroelectricity and antiferromagnetism at room temperature. Here, the Fe3+-O-Fe3+ bond angles are 143.50 and 159.280 which is deviated from 1800. This Fe3+-O-Fe3+ super-exchange interaction contributes to an AFM ordering with a weak FM component. An antisymmetric DM exchange interaction (Di. Si x Sj) is attributed to the weak FM component between adjacent spins and introduced spin-orbit interaction. As a result an electric polarization P - eij x (Si x Sj) is produced due to local crystal anisotropy. To acquire a conception involving the contribution of grain and grain boundary of ErFeO3, we have analyzed complex impedance and modulus spectra and fitted with the equivalent circuit diagram. The imaginary part of electric modulus is fitted by KWW function and the stretched exponent is found to be 0.3< 0.48. The conduction mechanism of ErFeO3 is followed CBH model.

Automated summary

ErFeO3, originally a centrosymmetric structure without ferroelectricity, unexpectedly exhibits ferroelectricity and antiferromagnetism at room temperature. The deviation of Fe3+-O-Fe3+ bond angles and the presence of super-exchange interaction contribute to this unique behavior. Complex impedance analysis and fitting with an equivalent circuit diagram reveal the conduction mechanism of ErFeO3, as well as the contribution of grain and grain boundary to its properties.