Interfaceless Exchange Bias in CoFe2O4 Nanocrystals

Oxidized cobalt ferrite nanocrystals with a modified distribution of the magnetic cations in their spinel structure give place to an unusual exchange-coupled system with a double reversal of the magnetization, exchange bias, and increased coercivity, but without the presence of a clear physical inte...

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Bibliographic Details
Published in:Nano letters 2023-03, Vol.23 (5), p.1688-1695
Main Authors: Rivas-Murias, Beatriz, Testa-Anta, Martín, Skorikov, Alexander S., Comesaña-Hermo, Miguel, Bals, Sara, Salgueiriño, Verónica
Format: Article
Language:English
Subjects:
Chemical Sciences
Letter
Material chemistry
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Summary:Oxidized cobalt ferrite nanocrystals with a modified distribution of the magnetic cations in their spinel structure give place to an unusual exchange-coupled system with a double reversal of the magnetization, exchange bias, and increased coercivity, but without the presence of a clear physical interface that delimits two well-differentiated magnetic phases. More specifically, the partial oxidation of cobalt cations and the formation of Fe vacancies at the surface region entail the formation of a cobalt-rich mixed ferrite spinel, which is strongly pinned by the ferrimagnetic background from the cobalt ferrite lattice. This particular configuration of exchange-biased magnetic behavior, involving two different magnetic phases but without the occurrence of a crystallographically coherent interface, revolutionizes the established concept of exchange bias phenomenology.
ISSN:1530-6984
1530-6992
DOI:10.1021/acs.nanolett.2c04268