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El efecto Kondo en presencia del ferromagnetismo
Abhay N Pasupathy1, Radoslaw C Bialczak, Jan Martinek
1Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, NY 14853, USA.
Science (New York, N.Y.)
|October 2, 2004
Resumen
El túnel asistido por Kondo a través de moléculas de C60 se estudió en electrodos de níquel ferromagnéticos. El pico de Kondo se dividió debido al ferromagnetismo, con una división dependiente de la alineación magnética de los electrodos, lo que indica una división de intercambio.
Área de la Ciencia:
- Física de la materia condensada Física de la materia condensada
- La mecánica cuántica es la mecánica cuántica.
- Ciencia de los materiales Ciencia de los materiales.
Sus antecedentes:
- El efecto Kondo describe la dispersión de electrones de conducción por impurezas magnéticas.
- Comprender el transporte de electrones a través de las uniones moleculares es crucial para la electrónica molecular.
- La influencia del ferromagnetismo en las correlaciones moleculares de Kondo no se entiende completamente.
Objetivo del estudio:
- Para investigar el túnel asistido por Kondo en moléculas de C60 contactadas por electrodos ferromagnéticos.
- Para analizar el impacto de la magnetización de electrodos en las correlaciones de Kondo.
- Para explorar el mecanismo detrás de la división del pico Kondo observado.
Principales métodos:
- Fabricación de uniones moleculares utilizando moléculas de C60 y electrodos de níquel ferromagnético.
- Medición de la conductividad diferencial a través de las uniones moleculares.
- Variación sistemática de la alineación magnética de los electrodos (paralelo y antiparalelo).
- Análisis de la dependencia del voltaje, la temperatura y el campo magnético de la conductancia.
Principales resultados:
- Se observó que las correlaciones de Kondo persisten a pesar de la presencia de ferromagnetismo.
- Se midió una división del pico de Kondo en la conductividad diferencial.
- La división del pico de Kondo disminuyó a medida que los momentos magnéticos de los electrodos pasaron de la alineación paralela a la antiparalela.
- La división observada era demasiado grande para ser atribuida a un campo magnético local, pero consistente con las predicciones de división de intercambio.
- Se observaron valores negativos de magnetorresistencia significativamente mayores que la estimación de Julliere.
Conclusiones:
- El ferromagnetismo en los electrodos conduce a la división de intercambio de la resonancia Kondo en las uniones moleculares C60.
- El efecto Kondo en tales sistemas puede dar lugar a una gran magnetorresistencia negativa.
- Este estudio proporciona información sobre la interacción entre el magnetismo y los fenómenos cuánticos en la electrónica molecular.
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