Field-sweep-rate dependence of the coercive field of single-molecule magnets: A classical approach with applications to the quantum regime

Abstract

A method, based on the Néel-Brown model of thermally activated magnetization reversal of a magnetic single-domain particle, is proposed to study the field-sweep-rate dependence of the coercive field of single-molecule magnets (SMMs). The application to Mn12 and Mn84 SMMs allows the determination of the important parameters that characterize the magnetic properties: the energy barrier, the magnetic anisotropy constant, the spin, τ0, and the crossover temperature from the classical to the quantum regime. The method may be particularly valuable for large SMMs that do not show quantum tunneling steps in the hysteresis loops. © 2005 The American Physical Society.