Magnetocrystalline and Surface Anisotropy in CoFe<sub>2</sub>O<sub>4</sub> Nanoparticles
The effect of the annealing temperature <i>T</i><sub>ann</sub> on the magnetic properties of cobalt ferrite nanoparticles embedded in an amorphous silica matrix (CoFe<sub>2</sub>O<sub>4</sub>/SiO<sub>2</sub>), synthesized by a sol-gel auto-...
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MDPI AG
2020-06-01
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| Col·lecció: | Nanomaterials |
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| Accés en línia: | https://www.mdpi.com/2079-4991/10/7/1288 |
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| author | Alexander Omelyanchik María Salvador Franco D’Orazio Valentina Mameli Carla Cannas Dino Fiorani Anna Musinu Montserrat Rivas Valeria Rodionova Gaspare Varvaro Davide Peddis |
| author_facet | Alexander Omelyanchik María Salvador Franco D’Orazio Valentina Mameli Carla Cannas Dino Fiorani Anna Musinu Montserrat Rivas Valeria Rodionova Gaspare Varvaro Davide Peddis |
| author_sort | Alexander Omelyanchik |
| collection | DOAJ |
| description | The effect of the annealing temperature <i>T</i><sub>ann</sub> on the magnetic properties of cobalt ferrite nanoparticles embedded in an amorphous silica matrix (CoFe<sub>2</sub>O<sub>4</sub>/SiO<sub>2</sub>), synthesized by a sol-gel auto-combustion method, was investigated by magnetization and AC susceptibility measurements. For samples with 15% w/w nanoparticle concentration, the particle size increases from ~2.5 to ~7 nm, increasing <i>T</i><sub>ann</sub> from 700 to 900 °C. The effective magnetic anisotropy constant (<i>K</i><sub>eff</sub>) increases with decreasing <i>T</i><sub>ann</sub>, due to the increase in the surface contribution. For a 5% w/w sample annealed at 900 °C, <i>K</i><sub>eff</sub> is much larger (1.7 × 10<sup>6</sup> J/m<sup>3</sup>) than that of the 15% w/w sample (7.5 × 10<sup>5</sup> J/m<sup>3</sup>) annealed at 700 °C and showing comparable particle size. This indicates that the effect of the annealing temperature on the anisotropy is not only the control of the particle size but also on the core structure (i.e., cation distribution between the two spinel sublattices and degree of spin canting), strongly affecting the magnetocrystalline anisotropy. The results provide evidence that the magnetic anisotropy comes from a complex balance between core and surface contributions that can be controlled by thermal treatments. |
| first_indexed | 2024-03-10T18:47:08Z |
| format | Article |
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| institution | Directory Open Access Journal |
| issn | 2079-4991 |
| language | English |
| last_indexed | 2024-03-10T18:47:08Z |
| publishDate | 2020-06-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Nanomaterials |
| spelling | doaj.art-1b59df9cd24547c79846ddaa721183612023-11-20T05:25:50ZengMDPI AGNanomaterials2079-49912020-06-01107128810.3390/nano10071288Magnetocrystalline and Surface Anisotropy in CoFe<sub>2</sub>O<sub>4</sub> NanoparticlesAlexander Omelyanchik0María Salvador1Franco D’Orazio2Valentina Mameli3Carla Cannas4Dino Fiorani5Anna Musinu6Montserrat Rivas7Valeria Rodionova8Gaspare Varvaro9Davide Peddis10Institute of Structure of Matter–CNR, Monterotondo Stazione, 00016 Rome, ItalyInstitute of Structure of Matter–CNR, Monterotondo Stazione, 00016 Rome, ItalyThe Department of Physical and Chemical Science, University of L’Aquila, Via Vetoio, Coppito, 67100 L’Aquila, ItalyDepartment of Geological and Chemical Sciences, University of Cagliari, Cittadella Universitaria, 09042 Monserrato, ItalyDepartment of Geological and Chemical Sciences, University of Cagliari, Cittadella Universitaria, 09042 Monserrato, ItalyInstitute of Structure of Matter–CNR, Monterotondo Stazione, 00016 Rome, ItalyDepartment of Geological and Chemical Sciences, University of Cagliari, Cittadella Universitaria, 09042 Monserrato, ItalyDepartment of Physics, University of Oviedo, 33204 Gijón, SpainInstitute of Physics, Mathematics and Information Technology, Immanuel Kant Baltic Federal University, 236041 Kaliningrad, RussiaInstitute of Structure of Matter–CNR, Monterotondo Stazione, 00016 Rome, ItalyInstitute of Structure of Matter–CNR, Monterotondo Stazione, 00016 Rome, ItalyThe effect of the annealing temperature <i>T</i><sub>ann</sub> on the magnetic properties of cobalt ferrite nanoparticles embedded in an amorphous silica matrix (CoFe<sub>2</sub>O<sub>4</sub>/SiO<sub>2</sub>), synthesized by a sol-gel auto-combustion method, was investigated by magnetization and AC susceptibility measurements. For samples with 15% w/w nanoparticle concentration, the particle size increases from ~2.5 to ~7 nm, increasing <i>T</i><sub>ann</sub> from 700 to 900 °C. The effective magnetic anisotropy constant (<i>K</i><sub>eff</sub>) increases with decreasing <i>T</i><sub>ann</sub>, due to the increase in the surface contribution. For a 5% w/w sample annealed at 900 °C, <i>K</i><sub>eff</sub> is much larger (1.7 × 10<sup>6</sup> J/m<sup>3</sup>) than that of the 15% w/w sample (7.5 × 10<sup>5</sup> J/m<sup>3</sup>) annealed at 700 °C and showing comparable particle size. This indicates that the effect of the annealing temperature on the anisotropy is not only the control of the particle size but also on the core structure (i.e., cation distribution between the two spinel sublattices and degree of spin canting), strongly affecting the magnetocrystalline anisotropy. The results provide evidence that the magnetic anisotropy comes from a complex balance between core and surface contributions that can be controlled by thermal treatments.https://www.mdpi.com/2079-4991/10/7/1288magnetic nanoparticlescobalt ferritemagnetic anisotropy |
| spellingShingle | Alexander Omelyanchik María Salvador Franco D’Orazio Valentina Mameli Carla Cannas Dino Fiorani Anna Musinu Montserrat Rivas Valeria Rodionova Gaspare Varvaro Davide Peddis Magnetocrystalline and Surface Anisotropy in CoFe<sub>2</sub>O<sub>4</sub> Nanoparticles Nanomaterials magnetic nanoparticles cobalt ferrite magnetic anisotropy |
| title | Magnetocrystalline and Surface Anisotropy in CoFe<sub>2</sub>O<sub>4</sub> Nanoparticles |
| title_full | Magnetocrystalline and Surface Anisotropy in CoFe<sub>2</sub>O<sub>4</sub> Nanoparticles |
| title_fullStr | Magnetocrystalline and Surface Anisotropy in CoFe<sub>2</sub>O<sub>4</sub> Nanoparticles |
| title_full_unstemmed | Magnetocrystalline and Surface Anisotropy in CoFe<sub>2</sub>O<sub>4</sub> Nanoparticles |
| title_short | Magnetocrystalline and Surface Anisotropy in CoFe<sub>2</sub>O<sub>4</sub> Nanoparticles |
| title_sort | magnetocrystalline and surface anisotropy in cofe sub 2 sub o sub 4 sub nanoparticles |
| topic | magnetic nanoparticles cobalt ferrite magnetic anisotropy |
| url | https://www.mdpi.com/2079-4991/10/7/1288 |
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