Structural and magnetic properties of core-shell Au/Fe$_3$O$_4$ nanoparticles
Authors
León Félix, L
Coaquira, JAH
Martínez, MAR
Goya, GF
Mantilla, J
Sousa, MH
Morais, PC
Publication Date
2017-02-06Journal Title
Scientific Reports
ISSN
2045-2322
Publisher
Nature Publishing Group
Volume
7
Number
41732
Language
English
Type
Article
This Version
VoR
Metadata
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León Félix, L., Coaquira, J., Martínez, M., Goya, G., Mantilla, J., Sousa, M., De Los Santos Valladares, L., et al. (2017). Structural and magnetic properties of core-shell Au/Fe$_3$O$_4$ nanoparticles. Scientific Reports, 7 (41732)https://doi.org/10.1038/srep41732
Abstract
We present a systematic study of core-shell Au/Fe$_3$O$_4$ nanoparticles produced by thermal decomposition under mild conditions. The morphology and crystal structure of the nanoparticles revealed the presence of Au core of $d$ = (6.9 ± 1.0) nm surrounded by Fe$_3$O$_4$ shell with a thickness of ~3.5 nm, epitaxially grown onto the Au core surface. The Au/Fe$_3$O$_4$ core-shell structure was demonstrated by high angle annular dark field scanning transmission electron microscopy analysis. The magnetite shell grown on top of the Au nanoparticle displayed a thermal blocking state at temperatures below $T_\text{B}$ = 59 K and a relaxed state well above $T_\text{B}$. Remarkably, an exchange bias effect was observed when cooling down the samples below room temperature under an external magnetic field. Moreover, the exchange bias field ($H_\text{EX}$) started to appear at $T$~40 K and its value increased by decreasing the temperature. This effect has been assigned to the interaction of spins located in the magnetically disordered regions (in the inner and outer surface of the Fe$_3$O$_4$ shell) and spins located in the ordered region of the Fe$_3$O$_4$ shell.
Keywords
structural properties, synthesis and processing
Sponsorship
This work was supported by the Brazilian agencies CNPq and CAPES (BEX 6932/15-0) through a financial support in the PhD Student Exchange Program performed in the Institute of Nanoscience of Aragón. The work in Spain was also supported by the Spanish Ministerio de Economia y Competitividad (MINECO) through project MAT2013-42551 and the Aragon Regional Government (DGA, Project No. E26) Technical support from LMAINA and SAI-UZ is acknowledged.
Embargo Lift Date
2100-01-01
Identifiers
External DOI: https://doi.org/10.1038/srep41732
This record's URL: https://www.repository.cam.ac.uk/handle/1810/263099
Rights
Attribution 4.0 International, Attribution 4.0 International, Attribution 4.0 International, Attribution 4.0 International