Uniform and non-uniform thermal switching of magnetic particles

The pulse-noise approach to systems of classical spins weakly interacting with the bath has been applied to study thermally-activated escape of magnetic nanoparticles over the uniform and nonuniform energy barriers at intermediate and low damping. The validity of approximating a single-domain particle by a single spin is investigated. Barriers for a non-uniform escape of elongated particles for the uniaxial model with transverse and longitudinal field have been worked out. Pulse-noise computations have been done for finite magnetic chains. The linear stability of the uniform barrier state has been investigated. The crossover between uniform and nonuniform barrier states has been studied with the help of the variational approach.