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Transición de fase cuántica desde el estado superparamagnético al estado superparamagnético cuántico en puntos
Weiwei Zheng1, Pushpendra Kumar, Aaron Washington
1Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306-4390, USA.
Journal of the American Chemical Society
|November 15, 2011
Resumen
Este estudio demuestra el ferromagnetismo a temperatura ambiente en puntos cuánticos de selenuro de cadmio dopados con cromo (QD). Una sorprendente transición de fase a baja temperatura a 20 K sugiere el inicio del ordenamiento magnético de largo alcance en estos QDs de semiconductores magnéticos diluidos.
Área de la Ciencia:
- Ciencia de los materiales Ciencia de los materiales.
- Física de la materia condensada Física de la materia condensada
- Nanotecnología La nanotecnología es la nanotecnología.
Sus antecedentes:
- El origen del magnetismo en semiconductores magnéticos diluidos (DMS) sigue siendo un tema controvertido a pesar de una extensa investigación.
- Los puntos cuánticos dopados con metales de transición (QD) se han mostrado prometedores, con DMS II-VI dopados con CrII exhibiendo ferromagnetismo a alta temperatura debido a las interacciones de intercambio p-d.
Objetivo del estudio:
- Para investigar las propiedades magnéticas de puntos cuánticos de selenuro de cadmio con dopaje de cromo ultrapequeños (CdSe DMSQDs con dopaje de Cr (II)).
- Para explorar las predicciones teóricas del ferromagnetismo en estos nanomateriales.
Principales métodos:
- Síntesis de CdSe DMSQDs ultrasmall (~3.1 nm) dopado con Cr (II) y CdSe DMSQDs.
- Caracterización de las propiedades magnéticas, incluido el ferromagnetismo a temperatura ambiente.
Principales resultados:
- CdSe DMSQDs Ultrasmall Cr{II}-doped exhiben ferromagnetismo a temperatura ambiente, alineándose con las expectativas teóricas.
- Se observó una nueva transición de fase a baja temperatura a 20 K, lo que indica el inicio de la ordenación de largo alcance en DMSQD de un solo dominio.
Conclusiones:
- Los hallazgos apoyan el marco teórico para el magnetismo en DMSQDs.
- La transición de fase observada a baja temperatura ofrece nuevos conocimientos sobre los mecanismos de ordenamiento magnético en semiconductores magnéticos diluidos a nanoescala.
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