Relaxation time of weakly interacting superparamagnets

The relaxation time of weakly interacting classical spins is calculated by introducing the averages of the local dipolar field, obtained by thermodynamic perturbation theory, in a rigorous expression for the single-spin thermoactivation rate in a weak but arbitrarily oriented field. At low temperatu...

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Bibliographic Details
Published in:Europhysics letters 2001-08, Vol.55 (3), p.418-424
Main Authors: Jönsson, P. E, García-Palacios, J. L
Format: Article
Language:English
Subjects:
75.10.Hk
75.50.Tt
76.20.+q
Condensed matter: electronic structure, electrical, magnetic, and optical properties
Diamagnetism and paramagnetism
Diamagnetism, paramagnetism and superparamagnetism
Exact sciences and technology
Fine-particle systems
Magnetic properties and materials
Physics
Small particles and nanoscale materials
Studies of specific magnetic materials
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Summary:The relaxation time of weakly interacting classical spins is calculated by introducing the averages of the local dipolar field, obtained by thermodynamic perturbation theory, in a rigorous expression for the single-spin thermoactivation rate in a weak but arbitrarily oriented field. At low temperatures the non-trivial dependence of the superparamagnetic blocking on the damping coefficient, numerically found by Berkov and Gorn, is reproduced by our model and interpreted in terms of the deviations from uniaxial anisotropy associated to the transversal component of the dipolar field acting on each spin.
ISSN:0295-5075
1286-4854
DOI:10.1209/epl/i2001-00430-0