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Estructuras cristalinas y magnéticas y propiedades del BiMnO (((3+delta)
Alexei A Belik1, Katsuaki Kodama, Naoki Igawa
1International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan. Alexei.BELIK@nims.go.jp
Journal of the American Chemical Society
|May 22, 2010
Resumen
Las estructuras cristalinas y magnéticas de la manganita de bismuto (BiMnO3+delta) se determinaron mediante difracción de neutrones. El contenido de oxígeno (delta) influye en la simetría del cristal, el ordenamiento magnético y el tamaño del momento magnético, con BiMnO ((3.14) exhibiendo un estado de vidrio giratorio.
Área de la Ciencia:
- Química del estado sólido.
- Ciencia de los materiales Ciencia de los materiales.
- La cristalografía es una técnica de cristalografía.
- El magnetismo es el magnetismo.
Sus antecedentes:
- La manganita de bismuto (BiMnO(3+delta)) es un material con estructuras cristalinas y magnéticas complejas.
- Se sabe que las propiedades de las manganitas de perovskita son sensibles a la estequiometría del oxígeno y a los defectos.
Objetivo del estudio:
- Para determinar las estructuras cristalinas y magnéticas de BiMnO ((3+delta) para variar el contenido de oxígeno (delta = 0.03, 0.08, 0.14).
- Investigar la influencia de la estequiometría de oxígeno en la simetría estructural, el ordenamiento magnético y los momentos magnéticos.
- Para comparar las propiedades de BiMnO(3+delta) con las de las manganitas de lantano relacionadas (LaMnO(3+delta)).
Principales métodos:
- Refinamiento de Rietveld de los datos de difracción de neutrones recogidos a bajas temperaturas (8-10 K) y a temperatura ambiente (290 K).
- Análisis de las estructuras cristalinas, incluyendo la determinación de grupos espaciales y parámetros de celosía.
- Determinación de las estructuras magnéticas, las temperaturas de ordenamiento magnético (T) y los momentos magnéticos refinados.
Principales resultados:
- BiMnO ((3.03) y BiMnO ((3.08) se cristalizan en sistemas monoclínicos (C2 / c y P2 ((1) / c, respectivamente), exhibiendo ferromagnetismo por debajo de 82 K y 68 K, respectivamente, con momentos magnéticos de 2,88 ((2) μB y 2,33 ((2) μB a 10 K.
- Las vacantes de Mn se localizan en sitios específicos, lo que potencialmente impulsa los cambios observados en la simetría del cristal.
- BiMnO ((3.14) se cristaliza en un sistema ortorrómbico (Pnma) y muestra un estado magnético de vidrio de espín sin ordenamiento magnético hasta 8 K.
Conclusiones:
- Los cambios sistemáticos en la estructura cristalina, el ordenamiento magnético y las propiedades magnéticas de BiMnO ((3+delta) son fuertemente dependientes del contenido de oxígeno (delta).
- La ordenación de vacantes y la ordenación de cargas se proponen como mecanismos para las transiciones estructurales observadas.
- El estudio proporciona una caracterización estructural y magnética detallada de BiMnO ((3+delta), destacando su sintonizabilidad con estequiometría de oxígeno.
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