Theoretical Prediction of Multiferroicity in SmBaMn2O6

By means of symmetry analysis and density-functional calculations, both the crystal structure and the sizable ferroelectric polarization are predicted in A-site ordered half-doped manganite SmBaMn2O6. It is shown that the ferroelectricity is determined by apical oxygen displacement, which involves MnO6 octahedral tilt mode. Furthermore, an analysis of the link between the ferroelectricity and the rare earth ionic size in the manganite series is carried out, in the aim of clarifying the chemical trend. The computational result quantitatively shows that the relatively small rare earth ion with respect to Ba ion enhances the ferroelectric polarization up to order of several mu C/cm(2).