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 CoxNi1-xFe2O4 (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 CoFe2O4: ∼130 A m2 kg-1) 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. This journal is © The Royal Society of Chemistry.

Evolution of the magnetic structure with chemical composition in spinel iron oxide nanoparticles

MUSCAS, GIUSEPPE;CONCAS, GIORGIO;CANNAS, CARLA;MUSINU, ANNA MARIA GIOVANNA;
2015-01-01

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 CoxNi1-xFe2O4 (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 CoFe2O4: ∼130 A m2 kg-1) 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. This journal is © The Royal Society of Chemistry.
2015
Cobalt, Crystallography, Iron compounds, Iron oxides, Magnetic properties, Magnetic structure, Magnetism, Magnetization, Magnetocrystalline anisotropy, Metal nanoparticles, Nanoparticles, Saturation magnetization, Temperature, Cationic distribution, Chemical compositions, Collinear spin structures, Intense magnetic fields, Iron oxide nanoparticle, Noncollinear spin structures, Mossbauer spectroscopies, Superexchange interaction, Nanomagnetics, Cobalt-ferrite nanoparticles, Nickel ferrite, NIFE2O4 nanoparticles, Inversion degree, Polyol medium, Anisotropy, Mossbauer, Size, Co, Nanocrystals
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11584/120532
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