title: A strong ferroelectric ferromagnet created by means of spin-lattice coupling.
abstract: Ferroelectric ferromagnets are exceedingly rare, fundamentally interesting multiferroic materials that could give rise to new technologies in which the low power and high speed of field-effect electronics are combined with the permanence and routability of voltage-controlled ferromagnetism. Furthermore, the properties of the few compounds that simultaneously exhibit these phenomena are insignificant in comparison with those of useful ferroelectrics or ferromagnets: their spontaneous polarizations or magnetizations are smaller by a factor of 1,000 or more. The same holds for magnetic- or electric-field-induced multiferroics. Owing to the weak properties of single-phase multiferroics, composite and multilayer approaches involving strain-coupled piezoelectric and magnetostrictive components are the closest to application today. Recently, however, a new route to ferroelectric ferromagnets was proposed by which magnetically ordered insulators that are neither ferroelectric nor ferromagnetic are transformed into ferroelectric ferromagnets using a single control parameter, strain. The system targeted, EuTiO(3), was predicted to exhibit strong ferromagnetism (spontaneous magnetization, approximately 7 Bohr magnetons per Eu) and strong ferroelectricity (spontaneous polarization, approximately 10 microC cm(-2)) simultaneously under large biaxial compressive strain. These values are orders of magnitude higher than those of any known ferroelectric ferromagnet and rival the best materials that are solely ferroelectric or ferromagnetic. Hindered by the absence of an appropriate substrate to provide the desired compression we turned to tensile strain. Here we show both experimentally and theoretically the emergence of a multiferroic state under biaxial tension with the unexpected benefit that even lower strains are required, thereby allowing thicker high-quality crystalline films. This realization of a strong ferromagnetic ferroelectric points the way to high-temperature manifestations of this spin-lattice coupling mechanism. Our work demonstrates that a single experimental parameter, strain, simultaneously controls multiple order parameters and is a viable alternative tuning parameter to composition for creating multiferroics.
authors: Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14853-1501, USA.
authors: June Hyuk
authors: JH
authors: Lee
authors: Lei
authors: L
authors: Fang
authors: Eftihia
authors: E
authors: Vlahos
authors: Xianglin
authors: X
authors: Ke
authors: Young Woo
authors: YW
authors: Jung
authors: Lena Fitting
authors: LF
authors: Kourkoutis
authors: Jong-Woo
authors: JW
authors: Kim
authors: Philip J
authors: PJ
authors: Ryan
authors: Tassilo
authors: T
authors: Heeg
authors: Martin
authors: M
authors: Roeckerath
authors: Veronica
authors: V
authors: Goian
authors: Margitta
authors: M
authors: Bernhagen
authors: Reinhard
authors: R
authors: Uecker
authors: P Chris
authors: PC
authors: Hammel
authors: Karin M
authors: KM
authors: Rabe
authors: Stanislav
authors: S
authors: Kamba
authors: Jürgen
authors: J
authors: Schubert
authors: John W
authors: JW
authors: Freeland
authors: David A
authors: DA
authors: Muller
authors: Craig J
authors: CJ
authors: Fennie
authors: Peter
authors: P
authors: Schiffer
authors: Venkatraman
authors: V
authors: Gopalan
authors: Ezekiel
authors: E
authors: Johnston-Halperin
authors: Darrell G
authors: DG
authors: Schlom
mesh_terms: D025802:Electric Capacitance; D004560:Electricity; D005063:Europium / Q000737:chemistry*; D008280:Magnetics; D017348:Microscopy, Electron, Scanning Transmission; D010087:Oxides / Q000737:chemistry*; D013696:Temperature; D014025:Titanium / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D010087:Oxides; C552630:europium titanium trioxide; D005063:Europium; D014025:Titanium