Artículos de revistas
Different Approaches To Analyze The Dipolar Interaction Effects On Diluted And Concentrated Granular Superparamagnetic Systems
Registro en:
Journal Of Magnetism And Magnetic Materials. Elsevier Science Bv, v. 428, p. 105 - 118, 2017.
0304-8853
1873-4766
WOS:000397200800017
10.1016/j.jmmm.2016.12.019
Autor
Moscoso-Londono
O.; Tancredi
P.; Muraca
D.; Mendoza Zelis
P.; Coral
D.; Fernandez van Raap
M. B.; Wolff
U.; Neu
V.; Damm
C.; de Oliveira
C. L. P.; Pirota
K. R.; Knobel
M.; Socolovsky
L. M.
Institución
Resumen
Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Controlled magnetic granular materials with different concentrations of magnetite nanoparticles immersed in a non-conducting polymer matrix were synthesized and, their macroscopic magnetic observables analyzed in order to advance towards a better understanding of the magnetic dipolar interactions and its effects on the obtained magnetic parameters. First, by means of X-ray diffraction, transmission electron microscopy, small angle X-ray scattering and X-ray absorption fine structure an accurate study of the structural properties was carried out. Then, the magnetic properties were analyzed by means of different models, including those that consider the magnetic interactions through long-range dipolar forces as: the Interacting Superparamagnetic Model (ISP) and the Vogel-Fulcher law (V-F). In systems with larger nanoparticle concentrations, magnetic results clearly indicate that the role played by the dipolar interactions affects the magnetic properties, giving rise to obtaining magnetic and structural parameters without physical meaning. Magnetic parameters as the effective anisotropic constant, magnetic moment relaxation time and mean blocking temperature, extracted from the application of the ISP model and V-F Law, were used to simulate the zero-field-cooling (ZFC) and fieldcooling curves (FC). A comparative analysis of the simulated, fitted and experimental ZFC/FC curves suggests that the current models depict indeed our dilute granular systems. Notwithstanding, for concentrated samples, the ISP model infers that clustered nanoparticles are being interpreted as single entities of larger magnetic moment and volume, effect that is apparently related to a collective and complex magnetic moment dynamics within the cluster. 428 105 118 FAPESP [2014/26672-8, 2011/01235-6, 2011/02356-11] CONICET ANPCyT Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)