Time Decrease of Magnetic Permeability in Alnico

The formal theory, based on the concept of thermal activation of domain processes, previously proposed to account for the phenomenon of magnetic viscosity, has been extended to describe time decrease of permeability Within certain limits the predictions of the theoretical analysis are verified by measurements made on time decrease of permeability using an alnico rod specimen. It is shown that the quantitative results of these measurements are in good agreement with those obtained from the magnetic viscosity experiments The possible physical mechanisms responsible for both magnetic viscosity and time decrease of permeability in alnico are discussed