Heterostructured material systems devoid of ferroic components are presumed not todisplay ordering associated with ferroelectricity. In heterostructures composed of transitionmetal oxides, however, the disruption introduced by an interface can affect the balance ofthe competing interactions among electronic spins, charges and orbitals. This has led to theemergence of properties absent in the original building blocks of a heterostructure, includingmetallicity, magnetism and superconductivity. Here we report the discovery of ferroelectricityin artificial tri-layer superlattices consisting solely of non-ferroelectric ndmno3/srmno3/Lamno3 layers. Ferroelectricity was observed below 40K exhibiting strong tunability bysuperlattice periodicity. Furthermore, magnetoelectric coupling resulted in 150% magneticmodulation of the polarization. Density functional calculations indicate that broken spaceinversion symmetry and mixed valency, because of cationic asymmetry and interfacial polardiscontinuity, respectively, give rise to the observed behaviour. our results demonstrate theengineering of asymmetric layered structures with emergent ferroelectric and magnetic fieldtunable functions distinct from that of normal devices, for which the components are typicallyferroelectrics.
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