High Temperature Magnetic Stabilization of Cobalt Nanoparticles by an Antiferromagnetic Proximity Effect.
Phys Rev Lett
; 115(5): 057201, 2015 Jul 31.
Article
en En
| MEDLINE
| ID: mdl-26274435
ABSTRACT
Thermal activation tends to destroy the magnetic stability of small magnetic nanoparticles, with crucial implications for ultrahigh density recording among other applications. Here we demonstrate that low-blocking-temperature ferromagnetic (FM) Co nanoparticles (T(B)<70 K) become magnetically stable above 400 K when embedded in a high-Néel-temperature antiferromagnetic (AFM) NiO matrix. The origin of this remarkable T(B) enhancement is due to a magnetic proximity effect between a thin CoO shell (with low Néel temperature, T(N), and high anisotropy, K(AFM)) surrounding the Co nanoparticles and the NiO matrix (with high T(N) but low K(AFM)). This proximity effect yields an effective antiferromagnet with an apparent T(N) beyond that of bulk CoO, and an enhanced anisotropy compared to NiO. In turn, the Co core FM moment is stabilized against thermal fluctuations via core-shell exchange-bias coupling, leading to the observed T(B) increase. Mean-field calculations provide a semiquantitative understanding of this magnetic-proximity stabilization mechanism.
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01-internacional
Banco de datos:
MEDLINE
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En
Revista:
Phys Rev Lett
Año:
2015
Tipo del documento:
Article
País de afiliación:
España