resumo
Self-doped h-LuMnxO3 +/-delta multiferroic ceramics with 0.92 <= x <= 1.12 were studied for the dependence of: magnetic properties on x. Interlocking of lattice distortion at the nanoscale with ferroelectric (FE) domains in bulk RMnO3 materials is, mostly unknown. Here we report occurrence of nanodomains in transmission electron microscopy (TEM) images with the presence of antiphase boundaries/ferroelectric domain walls separating nano-FE domains. Observed chemical inhoi-nogeneity across the crystalline grains of the ceramics causes distortion in the lattice. Formation of nanostructural domains revealed across particles of Mn deficient or Lu, deficient samples includes bands of Strained atomic planes, structural antiphase boundaries, and planar defects similar to stacking fault ribbons. Nanotwins exist in the basal plane, the twin boundary representing disorder of the stacking of atomic planes along the [110] direction. Image contrast in high resolution HRTEM images and TEM linage simulation confirm the role of planar defects,on switching of polarisation, which, cause topology breaking of sixfold vortices,of FE domains in h-RMnO3 oxides. The local orbital arrangements of ions are investigated by EELS spectroscopy of O K-edge supported by theoretical analysis: Irreversibility in magnetization below the Neel temperature of antiferromagnetic ordering of the h-LuMnxO3 +/-delta multiferroic solid solution is found for all ceramics showing dependence on cation vacancy type and nominal content. The main features Observed in the irreversibility of magnetization were correlated to defects and inhomogeneity in the nanoscale images of the lattice of ceramics. The interplay of lattice distortion linked to extended defects and magnetic/ferroelectric properties of multiferroic ceramics is further discussed.
palavras-chave
STRUCTURAL ANTIPHASE DOMAIN; MULTIFERROIC YMNO3; MAGNETIC-STRUCTURE; VORTEX DOMAINS; WALLS; OXIDE; MANGANITES
categoria
Chemistry; Science & Technology - Other Topics; Materials Science
autores
Baghizadeh, A; Vieira, JM; Goncalves, JN; Willinger, MG; Ferro, MC; Amaral, VS
nossos autores
Ali Baghi Zadeh
Bolseiro de pós-Doutoramento
João Nuno Santos Gonçalves
Investigador Júnior
Joaquim Manuel Vieira
Professor(a) Jubilado(a)
Marta Ascenção Carmona Ferro
Técnico de Laboratório
Vitor Brás Sequeira Amaral
Professor Catedráticoagradecimentos
A.B. and J.N.G. acknowledge the financial support of FCT fellowships SFRH/BPD/80663/2011 and SFRH/BPD/82059/2011, respectively. We also acknowledge the Electron Microscopy Group in Fritz Habor Institute, Berlin for providing the equipment for TEM Studies. A.B. acknowledges Achim Klein-Hoffmann for teaching sample preparation and his support and also the help of staff in the Microscopy Center of the Aveiro University, Portugal and access to the electron microscopy equipment within the FCT project REDE/1509/RME/2005. This work was developed within the scope of the project CICECO-Aveiro Institute of Materials, POCI-01-0145-FEDER-007679 (FCT ref. ULD/CTM/50011/2013), financed by national funds through the FCT/MEC and when appropriate cofinanced by FEDER under the PT2020 Partnership Agreement.