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Ferromagnetismo en suspensiones de plaquetas magnéticas en cristales líquidos
Alenka Mertelj1, Darja Lisjak1, Miha Drofenik2
1J. Stefan Institute, SI-1000 Ljubljana, Slovenia.
Nature
|December 17, 2013
Resumen
Los investigadores lograron el ordenamiento ferromagnético a temperatura ambiente en cristales líquidos utilizando nanopartículas ferromagnéticas. Este avance permite nuevas posibilidades para los dispositivos magneto-ópticos mediante el control de la magnetización con campos magnéticos mínimos.
Área de la Ciencia:
- Física de la materia blanda Física de la materia blanda
- Ciencia de los materiales Ciencia de los materiales.
- El magnetismo es el magnetismo.
Sus antecedentes:
- Las suspensiones de cristal líquido ferromagnético-nemático se propusieron teóricamente hace décadas.
- La realización experimental de la magnetización espontánea ha sido un desafío.
- Los sistemas anteriores exhibieron paramagnetismo, no ferromagnetismo verdadero, sin campos externos.
Objetivo del estudio:
- Lograr y caracterizar experimentalmente fases ferromagnéticas macroscópicas en cristales líquidos.
- Investigar el papel de la forma de las partículas y las interacciones en la formación del orden ferromagnético.
- Para explorar las posibles aplicaciones en dispositivos magneto-ópticos.
Principales métodos:
- Suspensión de plaquetas ferromagnéticas de tamaño nanométrico en un cristal líquido nemático.
- Refrigeración controlada (apagado) desde la fase isotrópica para inducir el ordenamiento.
- Caracterización de las propiedades magnéticas con y sin campos magnéticos externos.
Principales resultados:
- Se logra el ordenamiento ferromagnético al enfriarse desde la fase isotrópica.
- Muestras de polidominio observadas con estados de magnetización opuestos sin un campo.
- Muestras de monodominio creadas con capacidad de conmutación mediante la inversión del campo magnético.
- Demostró que las propiedades surgen de las interacciones dipolares elásticas y magnéticas nemáticas.
Conclusiones:
- La forma de las nanopartículas y las interacciones nemáticas son clave para el ferromagnetismo a temperatura ambiente en estos sistemas.
- El fluido ferromagnético resultante responde a campos magnéticos muy bajos.
- Existen aplicaciones potenciales para nuevos dispositivos magneto-ópticos.
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