Density of energy barriers in fine magnetic particle systems

Summary form only given. Recently we have developed a numerical method based on the minimization of the Onsager-Machlup functional which allows to calculate energy barriers for the transition between any two metastable states in magnetic systems with arbitrary interparticle interaction. Using this method we have performed the systematic study of energy barriers in systems of fine magnetic particles with the uniaxial anisotropy and dipolar interparticle interaction. In such systems the two most important parameters are (i) the reduced single particle anisotropy /spl beta/ = 2K/M/sub S//sup 2/ (where K is the ´normal´ anisotropy constant and M/sub s/ the material saturation magnetization) and (ii) the particle volume concentration c. The interplay of these parameters determines whether the single-particle or collective remagnetization modes dominate the system behaviour.