Origin of ferroelectricity in multiferroic ErFeO3

Highlights: • In ErFeO₃ the local crystal anisotropy developed due to the exchange interaction between Fe ions, is the origin of ferroelectric polarization. • A canted antiferromagnetic nature is observed within the temperature range 620K (T_m1) and 894K (T_m2). • To clearly observe a linear magnetoelectric coupling in ErFeO3 NPs, we do find evidence for a higher order magnetoelectric ME interaction through α_ME measurement. • M″ is fitted by using KWW function and the stretched exponent is found to be 0.3• The conduction mechanism to follow the correlated barrier hopping (CBH) model. 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 (D_i. S_i x S_j) is attributed to the weak FM component between adjacent spins and introduced spin-orbit interaction. As a result an electric polarization P ~ e_ij x (S_i x S_j) 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 0.33 is followed CBH model.