Artificially imposed hexagonal ferroelectricity in canted antiferromagnetic YFeO3 epitaxial thin films

Abstract

Antiferromagnetic YFeO3, belonging to a family of centrosymmetric orthoferrites (space group Pbnm), is known to be nonferroelectric. Here we report, contrary to this common knowledge, that an epitaxial YFeO3 thin film fabricated by adopting a hexagonal template is characterized by a six-fold hexagonal symmetry and exhibits ferroelectricity with a ferroelectric Curie temperature (T-c) of similar to 460 K. According to first-principles calculations, the P6(3)/mmc-P6(3)cm structural phase transition at T-c by the freezing-in of the zone-boundary K-3 phonon is primarily responsible for the observed room-temperature ferroelectricity and the asymmetric Y 4d(z)(2)-O 2pz orbital overlapping along the c-axis of P6(3)cm over the Gamma-M first Brillouin zone is the electronic origin of this artificially imposed ferroelectricity. For temperatures between 115 K (Neel point) and 20 K, the present thin film interestingly shows meta-magnetism-like responses. (C) 2013 Elsevier B.V. All rights reserved.