| Issue |
Europhys. Lett.
Volume 47, Number 1, July 1999
|
|
|---|---|---|
| Page(s) | 122 - 127 | |
| Section | Condensed matter: electronic structure, electrical, magnetic and optical properties | |
| DOI | https://doi.org/10.1209/epl/i1999-00361-2 | |
| Published online | 01 September 2002 | |
Dynamical properties of non-interacting Co nanoparticles
1
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
Received:
4
December
1998
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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