Effective anisotropy field variation of magnetite nanoparticles with size reduction |
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Authors: | J. M. Vargas E. Lima Jr R. D. Zysler J. G. S. Duque E. De Biasi M. Knobel |
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Affiliation: | (1) Centro Atómico Bariloche and Instituto Balseiro, 8400 S. C. de Bariloche, RN, Argentina;(2) Instituto de Física “Gleb Wataghin”, Universidade Estadual de Campinas, Campinas (SP), 13081-970, Brazil |
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Abstract: | Size effect on the internal magnetic structure has been investigated on weakly interacting magnetite (Fe3O4) nanoparticles by ferromagnetic resonance experiments at 9.5 GHz as a function of temperature (4–300 K). A set of three samples with mean particle size of 2.5 nm, 5.0 nm and 13.0 nm, respectively, were prepared by chemical route with narrow size distribution (σ < 0.27). To minimize the dipolar interaction, the particles were dispersed in a liquid and a solid polymer matrix at ∼0.6% in mass. By freezing the liquid suspension with an applied external field, a textured was obtained. Thus, both random and textured suspensions were studied and compared. The ferromagnetic resonance experiments in zero-field-cooled and field-cooled conditions were carried out to study the size effect on the effective anisotropy field. The dc magnetization measurements clearly show that the internal magnetic structure was strongly affected by the particle size. |
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Keywords: | KeywordHeading" >PACS 75.50.Tt Fine-particle systems nanocrystalline materials 75.30.Gw Magnetic anisotropy 75.60.Ch Domain walls and domain structure 76.50.+g Ferromagnetic, antiferromagnetic, and ferrimagnetic resonances spin-wave resonance |
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