Interplay of 4f-3d magnetism and ferroelectricity in DyFeO ₃

DyFeO3 exhibits a weak ferromagnetism (TNFe ∼ 645 K) that disappears below a spin-reorientation (Morin) transition at TSRFe ∼ 50 K. It is also known that applied magnetic field induces ferroelectricity at the magnetic ordering temperature of Dy ions (TNDy ∼ 4.5 K). Here, we show that the ferroelectricity exists in the weak ferromagnetic state (TSRFe <T <TN,C) without applying a magnetic field, indicating the crucial role of weak ferromagnetism in inducing ferroelectricity. 57Fe Mössbauer studies show that a hyperfine field (Bhf) deviates from the mean-field–like behaviour that is observed in the weak ferromagnetic state and decreases below the onset of the spin-reorientation transition (80 K), implying that the Bhf above TSR had an additional contribution from Dy ions due to the induced magnetization by the weak ferromagnetic moment of the Fe sublattice and below TSR this contribution decreases due to collinear ordering of the Fe sublattice. These results clearly demonstrate the presence of magnetic interactions between Dy(4f) and Fe(3d) and their correlation with ferroelectricity in the weak ferromagnetic state of DyFeO3.