Magnetic relaxation in small-particle systems: ln(t/ tau 0) scaling
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Although most of the experimental work dealing with the magnetic relaxation of systems characterized by the existence of an energy-barrier distribution have been analyzed in terms of the so-called logarithmic approximation, this is not a good approximation because obviously it cannot describe the behavior for the whole range of temperatures and times. An alternative method called ln(t/τ0) scaling is proposed. This scaling method allows one to extrapolate the relaxation behavior at times that are experimentally completely unaccessible. From this scaling it is also possible to determine the attempt frequency 1/τ0, and if a certain distribution of energy barriers is assumed the width σ and the mean energy barrier is also obtained. The validity of the logarithmic approximation is critically discussed.