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Efecto magnetoelástico gigante en la apertura de una brecha de giro en Ba3BiIr2O9
Wojciech Miiller1, Maxim Avdeev, Qingdi Zhou
1School of Chemistry, The University of Sydney, Sydney 2006, Australia.
Journal of the American Chemical Society
|February 3, 2012
Resumen
Este estudio revela un efecto magnetoelástico gigante en Ba3BiIr2O9, un compuesto metálico de transición 5d. Este raro fenómeno está relacionado con una apertura de spin-gap y un cambio significativo en las distancias atómicas.
Área de la Ciencia:
- Ciencia de los materiales Ciencia de los materiales.
- Física del estado sólido Física del estado sólido
- El magnetismo cuántico es el magnetismo cuántico.
Sus antecedentes:
- Los metales de transición 4d y 5d poseen orbitales de valencia difusa, lo que hace que los fenómenos de cooperación cuántica como la magnetoelasticidad sean raros.
- La magnetoelasticidad, el acoplamiento entre las propiedades magnéticas y elásticas, es crucial para comprender los nuevos comportamientos de los materiales.
Objetivo del estudio:
- Para investigar la aparición de magnetoelasticidad en compuestos de metales de transición 5d.
- Para caracterizar las propiedades únicas de Ba3BiIr2O9 y su potencial para efectos de cooperación cuántica.
Principales métodos:
- Síntesis y caracterización estructural de la 6H-perovskita Ba3BiIr2O9.9.
- Mediciones de susceptibilidad magnética para identificar las transiciones magnéticas y la apertura de la brecha de giro.
- Dilatometría y mediciones de expansión térmica para cuantificar los efectos magnetoelásticos.
Principales resultados:
- Ba3BiIr2O9 exhibe un efecto magnetoelástico gigante, el más grande observado en cualquier compuesto 5d.
- Se produce una transición de fase de primer orden en T* = 74 K, marcada por una apertura de giro.
- La transición implica un aumento significativo del 4% en la distancia Ir-Ir y una expansión del volumen térmico negativo del 1%.
Conclusiones:
- El efecto magnetoelástico gigante observado es impulsado por una competencia entre la unión directa Ir-Ir y el súper intercambio magnético Ir-O-Ir.
- Ba3BiIr2O9 sirve como un sistema modelo para estudiar los fenómenos de cooperación cuántica en los compuestos metálicos de transición 5d.
- Este descubrimiento abre nuevas vías para el diseño de materiales con propiedades magnetoelásticas sintonizables.
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