Determination of the effective anisotropy constant of CoFe{sub 2}O{sub 4} nanoparticles through the T-dependence of the coercive field

Journal Article · Mon Mar 07 00:00:00 EST 2016 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4942535· OSTI ID:22597008

Carvalho, M. H.; Meneses, C. T.; Duque, J. G. S. ^[1]; Lima, R. J. S. ^[2]; Folly, W. S. D. ^[3]; Sarmento, V. H. V. ^[4]; Coelho, A. A. ^[5]

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1. Núcleo de Pós-Graduação em Física, Campus Prof. José Aloísio de Campos, UFS, 49100-000 São Cristóvão, SE (Brazil)
2. Universidade Federal de Campina Grande, Centro de Ciências e Tecnologia, Unidade Acadêmica de Física, 58429-900, Campina Grande, PB (Brazil)
3. Departamento de Geologia, Universidade Federal de Sergipe, 49100-000 São Cristóvão (Brazil)
4. Núcleo de Pós-Graduação em Química, Campus Prof. José Aloísio de Campos, UFS, 49100-000 São Cristóvão, SE (Brazil)
5. Instituto de Física “Gleb Wataghin,” UNICAMP, 13083-970 Campinas, SP (Brazil)

We present a systematic study of the coercive field of CoFe{sub 2}O{sub 4}–SiO{sub 2} nanocomposites. The samples were prepared via the sol-gel method by using the Tetraethyl Orthosilicate as starting reagent. Results of X-ray diffraction, transmission electron microscopy, and X-ray fluorescence confirm the dispersion of the magnetic nanoparticles inside the silica matrix. In addition, the shift in the maximum of Zero-Field-Cooled curves observed by varying the weight ratio of CoFe{sub 2}O{sub 4} nanoparticles to the precursor of silica is consistent with the increasing of average interparticle distances. Because our samples present a particle size distribution, we have used a generalized model which takes account such parameter to fit the experimental data of coercive field extracted from the magnetization curves as a function of applied field. Unlike most of the coercive field results reported in the literature for this material, the use of this model provided a successful description of the temperature dependence of the coercive field of CoFe{sub 2}O{sub 4} nanoparticles in a wide temperature range. Surprisingly, we have observed the decreasing of the nanoparticles anisotropy constant in comparison to the bulk value expected for the material. We believe that this can be interpreted as due to both the migration of the Co{sup 2+} from octahedral to tetrahedral sites.

• OSTI ID: 22597008
• Journal Information: Journal of Applied Physics, Vol. 119, Issue 9; Other Information: (c) 2016 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ANISOTROPY
COBALT IONS
COBALT OXIDES
COMPARATIVE EVALUATIONS
DIAGRAMS
FLUORESCENCE
MAGNETIZATION
NANOCOMPOSITES
NANOPARTICLES
PARTICLE SIZE
SILICA
SILICATES
SILICON OXIDES
SOL-GEL PROCESS
TEMPERATURE DEPENDENCE
TEMPERATURE RANGE
TRANSMISSION ELECTRON MICROSCOPY
X RADIATION
X-RAY DIFFRACTION