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Los fonones polarizados llevan el momento angular en la desmagnetización ultrarrápida
S R Tauchert1,2, M Volkov1,2, D Ehberger2
1Universität Konstanz, Fachbereich Physik, Konstanz, Germany.
Nature
|February 3, 2022
Resumen
Los pulsos láser ultrarrápidos desmagnetizan rápidamente las películas de níquel excitando fonones anisotrópicos únicos y duraderos. Estos fonones polarizados circularmente absorben el momento angular del sistema de espín, lo que explica la rápida pérdida de orden magnético.
Área de la Ciencia:
- Ciencias de los materiales
- Física de la materia condensada
- Fenómenos ultrarrápidos
Sus antecedentes:
- Los fenómenos magnéticos son cruciales para la tecnología, pero el control rápido del orden magnético es un reto.
- Los pulsos láser ultracortos pueden desmagnetizar materiales como el níquel en escalas de tiempo de femtosegundos, abriendo caminos para la espintrónica ultrarrápida.
Objetivo del estudio:
- Para investigar el mecanismo detrás de la desmagnetización ultrarrápida en películas de níquel.
- Para identificar el destino del momento angular durante la rápida pérdida de orden magnético.
Principales métodos:
- Utilizó difracción de electrones ultrarrápida para sondear la dinámica atómica.
- Analizó la evolución temporal de las propiedades del material después de la excitación con láser.
Principales resultados:
- Se observó una población instantánea y duradera de fonones anisotrópicos de alta frecuencia (150-750 fs) en el níquel.
- Se determina que el plano de anisotropía del fonón es perpendicular a la magnetización inicial con una amplitud de oscilación de 2 pm.
- Los fonones polarizados circularmente propuestos absorben el momento angular del sistema de espín.
Conclusiones:
- El tiempo de desmagnetización está vinculado a la aceleración atómica a través de la excitación de fonones.
- Proporciona una explicación atómica para el efecto Einstein-de Haas.
- Destaca la importancia de los fonones polarizados en la dinámica de no equilibrio y las transiciones de fase.
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