Spin-glass-like freezing and enhanced magnetization in ultra-small CoFe2O4 nanoparticles.
The magnetic properties of ultra-small (3 nm) CoFe(2)O(4) nanoparticles have been investigated by DC magnetization measurements as a function of temperature and magnetic field. The main features of the magnetic behaviour are blocking of non-interacting particle moments (zero-field-cooled magnetization T(max) approximately 40 K), a rapid increase of saturation magnetization (up to values higher than for the bulk material) at low T and an increase in anisotropy below 30 K due to the appearance of exchange bias. The low temperature behaviour is determined by a random freezing of surface spins. Localized spin-canting and cation distribution between the two sublattices of the spinel structure account quantitatively for the observed increase in saturation magnetization.
Peddis
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D
CNR-Istituto di Struttura della Materia, Monterotondo Stazione, (RM), Italy.
Cannas
C
C
Piccaluga
G
G
Agostinelli
E
E
Fiorani
D
D