Generalized Stoner-Wohlfarth model and the non-langevin magnetism of single-domain particles

In order to develop a model of magnetic dynamics for quantitative analysis of the temperature dependences of the magnetization of an ensemble of nanoparticles in various regimes of the preliminary cooling of a sample, the phenomenological Stoner-Wohlfarth model is generalized for single-domain particles to the case of a more accurate description of relaxation processes in a magnetic system. Calculations in this model and their detailed analysis exhibit a number of qualitative features, including the asymptotic behavior of magnetization and susceptibility in the high-temperature limit, which is different from the Langevin limit for ideal superparamagnetic particles.