Magnetic properties of iron oxide nanoparticles with spinel structure are strictly related to a complex interplay between cationic distribution and the presence of a non-collinear spin structure (spin canting). With the aim to gain better insight into the effect of the magnetic structure on magnetic properties, in this paper we investigated a family of small crystalline ferrite nanoparticles of the formula Co<inf>x</inf>Ni<inf>1-x</inf>Fe<inf>2</inf>O<inf>4</inf> (0 <= x <= 1) having equal size (?4.5 nm) and spherical-like shape. The field dependence of magnetization at low temperatures indicated a clear increase of magnetocrystalline anisotropy and saturation magnetization (higher than the bulk value for CoFe<inf>2</inf>O<inf>4</inf>: ~130 A m<sup>2</sup> kg<sup>-1</sup>) with the increase of cobalt content. The magnetic structure of nanoparticles has been investigated by Mössbauer spectroscopy under an intense magnetic field (8 T) at a low temperature (10 K). The magnetic properties have been explained in terms of an evolution of the magnetic structure with the increase of cobalt content. In addition a direct correlation between cationic distribution and spin canting has been proposed, explaining the presence of a noncollinear spin structure in terms of superexchange interaction energy produced by the average cationic distribution and vacancies in the spinel structure.
Evolution of the magnetic structure with chemical composition in spinel iron oxide nanoparticles
Foglietti V;Sangregorio C;Peddis D
2015
Abstract
Magnetic properties of iron oxide nanoparticles with spinel structure are strictly related to a complex interplay between cationic distribution and the presence of a non-collinear spin structure (spin canting). With the aim to gain better insight into the effect of the magnetic structure on magnetic properties, in this paper we investigated a family of small crystalline ferrite nanoparticles of the formula CoI documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.