title: Evidence for strain-induced ferroelectric order in epitaxial thin-film KTaO3.
abstract: In perovskite-structure epitaxial films, it has been theoretically predicted that the polarization and the coherence of polar order can increase with increasing crystallographic strain. Experimental evidence of strain-induced long-range ferroelectric order has not been obtained thus far, posing the fundamental question of whether or not strain can induce the long-range polar order. Here we demonstrate the existence of strain-induced ferroelectric order in quantum paraelectric KTaO3 by combining experimental investigations of epitaxial KTaO3 films and density-functional-theory calculations. The long-range ferroelectric order does exist under a large enough epitaxial strain. We suggest that a region of short-range polar order might appear between paraelectric and ferroelectric states in the strain-temperature phase diagrams.
authors.affiliation: Microelectronics and Materials Physics Laboratories, University of Oulu, P.O. Box 4500, FI-90014 Oulun yliopisto, Finland.
authors.forename: M
authors.initials: M
authors.lastname: Tyunina
authors.forename: J
authors.initials: J
authors.lastname: Narkilahti
authors.forename: M
authors.initials: M
authors.lastname: Plekh
authors.forename: R
authors.initials: R
authors.lastname: Oja
authors.forename: R M
authors.initials: RM
authors.lastname: Nieminen
authors.forename: A
authors.initials: A
authors.lastname: Dejneka
authors.forename: V
authors.initials: V
authors.lastname: Trepakov