Zur Theorie der Jordan-Nachwirkung / Theory of Thermally Activated Relaxation in Ferromagnets

Abstract

Theory of Thermally Activated Relaxation in Ferromagnets The theory of the thermally activated relaxation process in a ferromagnet, leading to the phenomenon of Jordan-type aftereffect, is reinvestigated. The analysis is based on a more general statistical approach than the concept of a macroscopic free energy as a function of a macroscopic state variable usually employed in this field. Within the simplest possible model analytical results are obtained, leading to a re-establishment of the usual concept for small systems and its break-down for systems larger than a critical size. For large systems asymptotic results are obtained differing qualitatively from those of the conventional scheme. The most important result is a temperature-independent viscosity coefficient 5V , defined by Eq. (3) of the text.