mar
28
2017
By zevaldir
Palestrante:
Prof. Dr. Antonio Martins Figueiredo Neto, FEP-IFUSP
Data do Seminário:
30/03/2017 - 14:30
Local:
Ala 1, sala 201 (Sala de Seminários), IFUSP
Resumo:
Magnetic fluids based on manganese ferrite nanoparticles were studied from the structural point of view through small angle x-rays scattering (SAXS) and from the magnetic point of view through zero-field cooling and field cooling (ZFC-FC) and ac susceptibility measurements (MS). Three different colloids with particles mean diameters of 2.78, 3.42, and 6.15 nm were investigated. The size distribution obtained from SAXS measurements follows a log-normal behavior. The ZFC-FC and MS results revealed the presence of an important magnetic interaction between the nanoparticles, characterized by a magnetic correlation distance .The colloidal medium can be pictures as composed by magnetic cluster constituted by Ninteracting particles. These magnetic clusters are not characterized by a physical aggregation of particles. The energy barrier energy obtained is consistent with the existence of this magnetic clusters. Besides the magnetic interaction between particles, confinement effects must be included to account for the experimental values of the magnetic energy barrier encountered.