title: Unusual Multiferroic Phase Transitions in PbTiO3Nanowires.
abstract: Unconventional phases and their transitions in nanoscale systems are recognized as an intriguing avenue for both unique physical properties and novel technological paradigms. Although the multiferroic phase has attracted considerable attention due to the coexistence and cross-coupling of electric and magnetic order parameters, mutually exclusive mechanism between ferroelectricity and ferromagnetism leaves conventional ferroelectrics such as PbTiO3simply nonmagnetic. Here, we demonstrate from first-principles that ultrathin PbTiO3nanowires exhibit unconventional multiferroic phases with emerging ferromagnetism and coexisting ferroelectric/ferrotoroidic ordering. Nanometer-scale and nonstoichiometric effects intrinsic to the nanowires bring about nonzero and nontrivial magnetic moments that coexist with the host ferroelectricity. The multiferroic order is susceptible to surface termination and nanowire morphology. Furthermore, calculations suggest that the nanowires undergo size-dependent ferroelectric-multiferroic-ferromagnetic phase transitions. This work therefore provides a route to multiferroic transitions in conventional nonmagnetic ferroelectric oxides.
authors.affiliation: Department of Mechanical Engineering and Science, Kyoto University , Nishikyo-ku, Kyoto 615-8540, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Shimada
authors.affiliation: Department of Mechanical Engineering and Science, Kyoto University , Nishikyo-ku, Kyoto 615-8540, Japan.
authors.forename: Tao
authors.initials: T
authors.lastname: Xu
authors.affiliation: Department of Mechanical Engineering and Science, Kyoto University , Nishikyo-ku, Kyoto 615-8540, Japan.
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Uratani
authors.affiliation: Department of Engineering Mechanics, School of Aeronautics and Astronautics, Zhejiang University , Hangzhou 310027, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Mechanical Engineering and Science, Kyoto University , Nishikyo-ku, Kyoto 615-8540, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Kitamura
keywords: ferroelectrics; multiferroic phase transition; nanowires; nonstoichiometry; size effects