title: Spin-glass-like freezing and enhanced magnetization in ultra-small CoFe2O4 nanoparticles.
abstract: 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.
authors.affiliation: CNR-Istituto di Struttura della Materia, Monterotondo Stazione, (RM), Italy.
authors.forename: D
authors.initials: D
authors.lastname: Peddis
authors.forename: C
authors.initials: C
authors.lastname: Cannas
authors.forename: G
authors.initials: G
authors.lastname: Piccaluga
authors.forename: E
authors.initials: E
authors.lastname: Agostinelli
authors.forename: D
authors.initials: D
authors.lastname: Fiorani