Artículo
High temperature emissivity, reflectivity, and x-ray absorption of BiFeO3
Massa, Nestor Emilio
; del Campo, Leire; de Sousa Meneses, Domingos; Echegut, Patrick; Fabbris, Gilberto F. L.; Azevedo, Gustavo; Martínez Lope, María Jesus; Alonso, José Antonio
Fecha de publicación:
05/2010
Editorial:
American Institute of Physics
Revista:
Journal of Applied Physics
ISSN:
0021-8979
Idioma:
Inglés
Tipo de recurso:
Artículo publicado
Clasificación temática:
Resumen
We report on the lattice evolution of BiFeO3 as function of temperature using far infrared emissivity, reflectivity, and x-ray absorption local structure. A power law fit to the lowest frequency soft phonon in the magnetic ordered phase yields an exponent = 0.25 as for a tricritical point. At about 200 K below TN 640 K it ceases softening as consequence of BiFeO3 metastability. We identified this temperature as corresponding to a crossover transition to an order-disorder regime. Above 700 K strong band overlapping, merging, and smearing of modes are consequence of thermal fluctuations and chemical disorder. Vibrational modes show band splits in the ferroelectric phase as emerging from triple degenerated species as from a paraelectric cubic phase above TC 1090 K. Temperature dependent x-ray absorption near edge structure XANES at the Fe K edge shows that lower temperature Fe3+ turns into Fe2+. While this matches the FeO wüstite XANES profile, the Bi LIII-edge downshift suggests a high temperature very complex bond configuration at the distorted A perovskite site. Overall, our local structural measurements reveal high temperature defect-induced irreversible lattice changes, below, and above the ferroelectric transition, in an environment lacking of long-range coherence. We did not find an insulator to metal transition prior to melting.
Palabras clave:
BiFeO3
,
MULTIFERROIC
,
FAR INFRARED EMISSIVITY
,
FAR INFRARED REFLECTIVITY
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Articulos(CEQUINOR)
Articulos de CENTRO DE QUIMICA INORGANICA "DR. PEDRO J. AYMONINO"
Articulos de CENTRO DE QUIMICA INORGANICA "DR. PEDRO J. AYMONINO"
Citación
Massa, Nestor Emilio; del Campo, Leire; de Sousa Meneses, Domingos; Echegut, Patrick; Fabbris, Gilberto F. L.; et al.; High temperature emissivity, reflectivity, and x-ray absorption of BiFeO3; American Institute of Physics; Journal of Applied Physics; 108; 8; 5-2010; 84114-84122
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