TIME-DEPENDENT MAGNETIZATION IN SYSTEMS WITH DISTRIBUTED ENERGY BARRIERS

In this paper the origin of non-linear behaviour in the ln(t) law of t ime dependence of magnetisation is examined. We calculate the time dep endence of magnetisation in a negative field after a previous saturati on in a positive field for a system of fine particles. Also we derive an analytical expression based on a series expansion in ln(t) for the change in magnetisation with time. The non-linear behaviour in the ln( t) law is found to arise from the distribution of energy barriers f(DE LTAE) within the system, and the magnitude of the non-linearity is gov erned by the width of the energy barrier distribution.