Nanoengineering room temperature ferroelectricity into orthorhombic SmMnO<sub>3</sub> films.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 32371855.
- Also identified by DOI 10.1038/s41467-020-16101-2 and PMC identifier 7200746.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
Orthorhombic RMnO<sub>3</sub> (R = rare-earth cation) compounds are type-II multiferroics induced by inversion-symmetry-breaking of spin order. They hold promise for magneto-electric devices. However, no spontaneous room-temperature ferroic property has been observed to date in orthorhombic RMnO<sub>3</sub>. Here, using 3D straining in nanocomposite films of (SmMnO<sub>3</sub>)<sub>0.5</sub>((Bi,Sm)<sub>2</sub>O<sub>3</sub>)<sub>0.5</sub>, we demonstrate room temperature ferroelectricity and ferromagnetism with T<sub>C,FM</sub> ~ 90 K, matching exactly with theoretical predictions for the induced strain levels. Large in-plane compressive and out-of-plane tensile strains (-3.6% and +4.9%, respectively) were induced by the stiff (Bi,Sm)<sub>2</sub>O<sub>3</sub> nanopillars embedded. The room temperature electric polarization is comparable to other spin-driven ferroelectric RMnO<sub>3</sub> films. Also, while bulk SmMnO<sub>3</sub> is antiferromagnetic, ferromagnetism was induced in the composite films. The Mn-O bond angles and lengths determined from density functional theory explain the origin of the ferroelectricity, i.e. modification of the exchange coupling. Our structural tuning method gives a route to designing multiferroics.