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Pana, O., Soran, M. L., Leostean, C., Macavei, S., Gautron, E., Teodorescu, C. M., Gheorghe, N. & Chauvet, O. (2012) Interface charge transfer in polypyrrole coated perovskite manganite magnetic nanoparticles. J. Appl. Phys. 111 044309.
Added by: Laurent Cournède (2016-03-10 21:28:40) |
| Type de référence: Article DOI: 10.1063/1.3686662 Numéro d'identification (ISBN etc.): 0021-8979 Clé BibTeX: Pana2012 Voir tous les détails bibliographiques  |
Catégories: PMN Mots-clés: dependence, fine-particle, gamma-fe2o3 nanoparticles, granular perovskites, magnetoresistive manganites, mn-k-edge, relaxation, size, transition, transport-properties Créateurs: Chauvet, Gautron, Gheorghe, Leostean, Macavei, Pana, Soran, Teodorescu Collection: J. Appl. Phys. |
Consultations : 1/486
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Different hybrid structures were obtained by coating magnetic nanoparticles of perovskite type manganite at optimal doping (La0.67Sr0.33MnO3, LSMO) with different quantities of polypyrrole (PPy). The amorphous layer of polypyrrole surrounding the crystalline magnetic core was observed by high resolution transmission electron microscopy (HRTEM) and analyzed by using X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) measurements in near edge structure (XANES) techniques. By analyzing the magnetic behavior of the samples one can observe that the surface modification of magnetic nanoparticles by PPy results in an increase in the saturation magnetization of the composites. The process is ascribed to paired electrons transferred from the delocalized p states of the PPy into the outer disordered layers of the manganite. The analysis of pre-edge peak of the Mn K-edge XANES spectra in the case of PPy coated LSMO nanoparticles indicates that the charge transfer between polymer and nanoparticles is (directed) going to missing or distorted oxygen positions, hence increasing the 3d electrons' mobility and orbital hybridization between the neighboring manganese ion. As a consequence, within the surface layers of LSMO nanoparticles, both energy bands disrupted the structure, and the double exchange process between Mn ions was reestablished determining the saturation magnetizations and pre-edge features increase, respectively. (C) 2012 American Institute of Physics. [doi:10.1063/1.3686662]
Added by: Laurent Cournède |