A.C. Lima, M.A. Morales, J.H. Araújo, J.M. Soares, D.M.A. Melo, A.S. Carriço. Evaluation of (BH)max and magnetic anisotropy of cobalt ferrite nanoparticles synthesized in gelatin.
Publicado em 02.08.2015 às 18:25:37
Abstract CoFe2O4 nanoparticles were synthesized using gelatin as a polymerizing agent. Structural, morphological and magnetic properties of samples treated at different temperatures were investigated by X-ray diffraction, scanning electron microscopy, Mössbauer spectroscopy and magnetization measurements. Our results revealed that the samples annealed at 623 K and temperatures above 973 K have a cation distributions given by (Co0.19Fe0.81)[Co0.81Fe1.19]O4 and (Co0.06Fe0.94)[Co0.94Fe1.06]O4, respectively. The particle sizes varied from 73 to 296 nm and the magnetocrystalline anisotropy, K1, has values ranging from 2.60×106 to 2.71×106 J/m3, as determined from the law of approach to saturation applied to the M×H data at high field. At 5 K, the saturation magnetization, coercive field and (BH)max varied from 76 to 95 Am2/kg, 479.9 to 278.5 kA/m and 9.7 to 20.9 kJ/m3, respectively. The reported values are in good agreement with near-stoichiometric cobalt ferrite samples.
Keywords Gelatin; CoFe2O4; Mössbauer spectroscopy; Magnetic properties; Nanoparticles; Anisotropy constant