title: A-site ordering versus electronic inhomogeneity in colossally magnetoresistive manganite films.
abstract: Epitaxial La(3/4)Ca(1/4)MnO3/MgO(100) (LCMO) thin film shows an unusual rhombohedral (R-3c) structure with a new perovskite superstructure at room temperature due to the CE-type ordering of La and Ca with modulation vector q=1/4[011]. A-site ordered film was found to be electronically homogeneous down to the 1 nm scale as revealed by scanning tunnelling microscopy/spectroscopy. In contrast, orthorhombic and A-site disordered LCMO demonstrate a mesoscopic phase separation far below the Curie temperature (TC). Unique La/Ca ordering compensates the cation mismatch stress within one supercell, a(S) approximately 1.55 nm, and enhances the electronic homogeneity. The phase separation does not seem to be a unique mechanism for the colossal magnetoresistance (CMR) as very large CMR approximately 500% was also observed in A-site ordered films.
authors.affiliation: Erstes Physikalisches Institut, Universität Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen, Germany.
authors.forename: V
authors.initials: V
authors.lastname: Moshnyaga
authors.forename: L
authors.initials: L
authors.lastname: Sudheendra
authors.forename: O I
authors.initials: OI
authors.lastname: Lebedev
authors.forename: S A
authors.initials: SA
authors.lastname: Köster
authors.forename: K
authors.initials: K
authors.lastname: Gehrke
authors.forename: O
authors.initials: O
authors.lastname: Shapoval
authors.forename: A
authors.initials: A
authors.lastname: Belenchuk
authors.forename: B
authors.initials: B
authors.lastname: Damaschke
authors.forename: G
authors.initials: G
authors.lastname: van Tendeloo
authors.forename: K
authors.initials: K
authors.lastname: Samwer