The magnetic properties of ultra-small (3 nm) CoFe2O4 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 TmaxH40 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.
Spin-glass-like freezing and enhanced magnetization in ultra-small CoFe2O4 nanoparticles
Peddis D;Agostinelli E;Fiorani D
2010
Abstract
The magnetic properties of ultra-small (3 nm) CoFe2O4 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 TmaxH40 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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
