title: Study of atomic structure and electronic structure of an AA'3B4O12 double-perovskite CaCu3Ir4O12 using STEM imaging and EELS techniques.
abstract: A newly discovered 1:3 A-site-ordered AA'3B4O12 perovskite oxide CaCu3Ir4O12 which has unusual electrical and magnetic properties was investigated using STEM imaging and EELS techniques in a probe corrected microscope. The target sample was compared with the other two iso-structural oxides of CaCu3Ru4O12 and CaCu3Ti4O12 with dissimilar physical properties. It has been found by STEM HAADF imaging that Ca and Cu on A and A' sites are ordered as expected. Oxygen atoms are imaged with STEM ABF imaging. The fine structures of the Cu L2,3 core loss and O-K edges show that the electronic structure of CaCu3Ir4O12 is very close to that of CaCu3Ru4O12, but different from CaCu3Ti4O12. The O-K near edge fine structures show extensive hybridization of Ir 5d and O 2p band. Cu L2,3 peaks indicate Cu in CaCu3Ir4O12 has 2+ valence, though Cu(2+) electrons mainly localized, they might have strong interactions with Ir(4+) 5d electrons through Ir-O-Cu, similar to the strong coupling of Ru with Cu in CaCu3Ru4O12.
authors.affiliation: National High Magnetic Field Laboratory, Florida State University, Tallahassee, FL 32310, USA. xin@magnet.fsu.edu
authors.forename: Y
authors.initials: Y
authors.lastname: Xin
authors.forename: H D
authors.initials: HD
authors.lastname: Zhou
authors.forename: J G
authors.initials: JG
authors.lastname: Cheng
authors.forename: J S
authors.initials: JS
authors.lastname: Zhou
authors.forename: J B
authors.initials: JB
authors.lastname: Goodenough