Thermal fluctuation of fine ferromagnetic particles

Fine ferromagnetic particles jump spontaneously from one locally stable state to another; they surmount intervening energy bartiers with the aid of thermal agitation. A theory of this phenomenon has as its primary goal the calculation of time constants. The elements of such a theory are presented. The emphasis is on calculations that require only elementary methods and on results that are simple enough to be easily applicable. The reader is assumed to be acquainted with the basic properties of ferromagnetic materials but not necessarily with Brownian-motion theory, on which the present theory is based.