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Interfaces and functional oxydes

Scientific highlights

Atmosphere-Induced Reversible Resistivity Changes in Ca/Y-Doped Bismuth Iron Garnet Thin Films

Resistive changes in Y-substituted bismuth iron garnet (BIG)

Bismuth iron garnet Bi3Fe5O12 (BIG) is a multifunctional insulating oxide exhibiting remarkably the largest known Faraday rotation and linear magnetoelectric coupling. Enhancing the electrical conductivity in BIG while preserving its magnetic properties would further widen its range of potential applications in oxitronic devices. Here, a site-selective co-doping strategy in which Ca2+ and Y3+ substitute for Bi3+ is applied. The resulting p- and n-type doped BIG films combine state-of-the-art magneto-optical properties and semiconducting behaviors above room temperature with rather low resistivity: 40 Ohm cm at 450 K is achieved in an n-type Y-doped BIG; this is ten orders of magnitude lower than that of Y3Fe5O12. High-resolution electron spectromicroscopy unveils the complete dopant solubility and the charge compensation mechanisms at the local scale in p- and n-type systems. Oxygen vacancies as intrinsic donors play a key role in the conduction mechanisms of these doped BIG films. On the other hand, a self-compensation of Ca2+ with oxygen vacancies tends to limit the conduction in p-type Ca/Y-doped BIG. Read more »

Direct Evidence of Fe2+/Fe3+ Charge Ordering in the Ferrimagnetic Hematite-Ilmenite Fe1.35Ti0.65O3-d Thin Films

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Here we report on the direct experimental evidence of Fe2+/Fe3+ charge ordering at room temperature in hematite-ilmenite Fe1.35Ti0.65O3-d epitaxial thin films grown by pulsed laser deposition, using aberration-corrected scanning transmission electron microscopy (STEM) coupled to high-resolution energy electron-loss spectroscopy (EELS). Read more »

Publications

Gloter, A., et al. Atomically resolved mapping of EELS fine structures. Materials Science in Semiconductor Processing 65, 2 - 17 (2017). Download: 1-s2.0-S1369800116302165-main.pdf (5.7 MB)
Popova, E., et al. Interplay between epitaxial strain and low dimensionality effects in a ferrimagnetic oxide. Journal of Applied Physics 121, (2017). Download: Popova_JAP2017_Strain-STEM-GPA.pdf (4.49 MB)
Inan Akmehmet, G., et al. Structure and Luminescence in Long Persistence Eu, Dy, and B Codoped Strontium Aluminate Phosphors: The Boron Effect. Journal of the American Ceramic Society n/a - n/a (2016).doi:10.1111/jace.14188 Download: Akmehmet_et_al-2016-Journal_of_the_American_Ceramic_Society.pdf (505.64 KB)
Chen, S.-Y., et al. Concentration Dependence of Oxygen Vacancy on the Magnetism of CeO 2 Nanoparticles. The Journal of Physical Chemistry C 116, 8707 - 8713 (2012).
Deboudt, K., Gloter, A., Mussi, A. & Flament, P. Red-ox speciation and mixing state of iron in individual African dust particles. Journal of Geophysical Research 117, (2012).
Bocher, L., et al. Atomic and Electronic Structure of the BaTiO 3 /Fe Interface in Multiferroic Tunnel Junctions. Nano Letters 12, 376 - 382 (2012). Download: Bocher-Nanoletters12.pdf (2.76 MB)
Yang, M., Baik, H., Ivanovskaya, V.V., Colliex, C. & Benayad, A. O K-energy loss near-edge structure change induced by tantalum impurity in monoclinic hafnium oxide. Journal Of Applied Physics 109, 053723 (2011).
Valencia, S., et al. Interface-induced room-temperature multiferroicity in BaTiO3. Nature Materials 10, 753 - 758 (2011). Download: Valencia_NatMat11_XMCD-BTOFe.pdf (761.54 KB)
Garcia, V., et al. Ferroelectric Control of Spin Polarization. Science 327, 1106–1110 (2010). Download: Garcia_Science10_ferroelectric_LSMO-BTO-Fe.pdf (400.27 KB)
Sefrioui, Z., et al. All-Manganite Tunnel Junctions with Interface-Induced Barrier Magnetism. Advanced Materials 22, 5029–+ (2010).
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