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Conocimientos mecanicistas sobre la expansión térmica negativa impulsada por la superinteracción en CuO
Yuanpeng Zhang1,2, Marshall McDonnell1, Stuart A Calder1
1Neutron Scattering Division , Oak Ridge National Laboratory (ORNL) , Oak Ridge , Tennessee 37831 , United States.
Journal of the American Chemical Society
|April 2, 2019
Resumen
La expansión térmica negativa en el óxido de cobre (CuO) es impulsada por la transferencia de electrones. Esta interacción de superecambio mejorada a lo largo de una dirección específica hace que el CuO se contraiga cuando se calienta, ofreciendo un nuevo control sobre las propiedades del material.
Área de la Ciencia:
- Ciencias de los materiales
- Física de la materia condensada
- Química del estado sólido
Sus antecedentes:
- La expansión térmica negativa (NTE) es un fenómeno contrario a la intuición en el que los materiales se contraen al calentarse.
- El óxido de cobre (CuO) presenta NTE, pero el mecanismo subyacente, en particular el vínculo entre el acoplamiento de la red de espín y NTE, sigue sin estar claro.
Objetivo del estudio:
- Para aclarar el mecanismo detrás de la expansión térmica negativa en CuO.
- Investigar la relación entre el acoplamiento de la red de espín y el NTE en CuO.
- Identificar los factores clave que rigen el NTE en CuO.
Principales métodos:
- Experimentos de dispersión de neutrones para sondear las interacciones magnéticas.
- Análisis de los ejes de deformación principales para determinar la expansión térmica direccional.
- Cálculos de la teoría funcional de la densidad (DFT) para modelar las propiedades electrónicas y magnéticas.
Principales resultados:
- La transferencia de electrones mejora significativamente la interacción de superecambio a lo largo de la dirección [101̅] a medida que disminuye la temperatura.
- Esta interacción mejorada a lo largo de [101̅] se identifica como el principal factor de NTE en CuO.
- La NTE ocurre solo cuando la vía de superecambio [101̅] se fortalece preferentemente sobre las interacciones magnéticas competidoras.
Conclusiones:
- El estudio explica la NTE en CuO a través de la interacción de superintercambio impulsada por la transferencia de electrones.
- Los hallazgos destacan el papel crítico del acoplamiento de la red de espín y las interacciones magnéticas direccionales en el control de la expansión térmica.
- Los resultados sugieren estrategias potenciales para manipular la expansión térmica a través de interacciones de superecambio, como la manipulación óptica o el dopaje.
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