Volume 47, Number 1, July 1999
|Page(s)||122 - 127|
|Section||Condensed matter: electronic structure, electrical, magnetic and optical properties|
|Published online||01 September 2002|
Dynamical properties of non-interacting Co nanoparticles
LPMC-SNCMP, Insa, Complexe Scientifique de Rangueil 31077 Toulouse Cedex, France
2 Laboratoire Louis Néel - 25 avenue des Martyrs, 38042 Grenoble Cedex, France
3 Laboratoire de Chimie de Coordination 205 route de Narbonne, 31077 Toulouse Cedex, France
Accepted: 20 April 1999
The dynamical properties of the magnetic moment of non-interacting cobalt nanoparticles dispersed in a polymer were investigated by ac-susceptibility (). We thus estimated the relaxation time of the magnetisation (τ) associated to the superparamagnetic properties of the particles. τ was found to follow the general Néel-Brown relaxation dynamics, with a pre-exponential relaxation time of for temperatures between 10 and 20 K. By combining the experimental results from ferromagnetic resonance, ac-susceptibility, and magnetisation, measurements giving the microscopic and macroscopic parameters, we demonstrate for the first time that the Coffey theoretical expressions were able to predict both τ and values. Finally, the thermal dependence of is discussed.
PACS: 75.50.Tt – Fine-particle systems / 76.60.Es – Relaxation effects
© EDP Sciences, 1999
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