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Local Structure of Amorphous EuO–TiO 2 Thin Films Probed by X ‐Ray Absorption Fine Structure
Author(s) -
Zong Yanhua,
Fujita Koji,
Akamatsu Hirofumi,
Nakashima Seisuke,
Murai Shunsuke,
Tanaka Katsuhisa
Publication year - 2012
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1551-2916.2011.04849.x
Subject(s) - extended x ray absorption fine structure , amorphous solid , xanes , coordination number , materials science , absorption (acoustics) , thin film , x ray absorption fine structure , crystallography , pulsed laser deposition , absorption spectroscopy , analytical chemistry (journal) , absorption edge , ion , ferromagnetism , spectroscopy , chemistry , optics , nanotechnology , band gap , condensed matter physics , optoelectronics , physics , organic chemistry , chromatography , quantum mechanics , composite material
We have investigated the local structure of amorphous oxides in EuO–TiO 2 system to understand the mechanism that gives rise to curious ferromagnetic properties recently observed in the system. X ‐ray absorption spectroscopy has been performed on amorphous EuTiO 3 and Eu 2 TiO 4 thin films prepared by the pulsed‐laser‐deposition method. The Ti K ‐edge X ‐ray absorption near‐edge structure ( XANES ) and extended X ‐ray absorption fine structure ( EXAFS ) data analyses reveal that the coordination number of Ti 4+ in the amorphous thin films is around 4, which is in sharp contrast to their crystalline counterparts, where Ti 4+ ions are octahedrally coordinated by oxide ions. It is therefore inferred that Ti 4+ acts as a network‐forming cation in the random network structure of the amorphous oxides. From the Eu L 3 ‐edge EXAFS data analyses, it is found that the coordination number of Eu 2+ is much lower and the nearest Eu–O bond length is shorter in the amorphous thin films than in the crystalline counterparts. The amorphization‐induced enhancement of ferromagnetic interactions observed in the EuO–TiO 2 system is discussed in terms of the local environment around Eu 2+ ions.