title: Multiferroic Domain Walls in Ferroelectric PbTiO3 with Oxygen Deficiency.
abstract: Atomically thin multiferroics with the coexistence and cross-coupling of ferroelectric and (anti)ferromagnetic order parameters are promising for novel magnetoelectric nanodevices. However, such ferroic order disappears at a critical thickness in nanoscale. Here, we show a potential path toward ultrathin multiferroics by engineering an unusual domain wall (DW)-oxygen vacancy interaction in nonmagnetic ferroelectric PbTiO3. We demonstrate from first-principles that oxygen vacancies formed at the DW unexpectedly bring about magnetism with a localized spin moment around the vacancy. This magnetism originates from the orbital symmetry breaking of the defect electronic state due to local crystal symmetry breaking at the DW. Moreover, the energetics of defects shows the self-organization feature of oxygen vacancies at the DW, resulting in a planar-arrayed concentration of magnetic oxygen vacancies, which consequently changes the deficient DWs into multiferroic atomic layers. This DW-vacancy engineering opens up a new possibility for novel ultrathin multiferroic.
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: 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: Yasumitsu
authors.initials: Y
authors.lastname: Araki
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: Dilute ferromagnetism; defects; domain walls; ferroelectrics; multiferroic monolayer; self-assembly