Thermally activated demagnetization in Co/Ni multilayers involving discrete identifiable stages

Abstract

We present data, obtained from measured Co/Ni multilayers, that indicate that the magnetic relaxation processes take place through a nucleation-coalescence sequence, and thus crucially implicates the existance of exchange and dipolar interactions. Depending on the layer thickness the relaxation proceeds either through a single global stage or through several partial ones. In both cases the relaxation stages involve a time lapse during which the macroscopic state of the system evolves very slowly, followed by a sharp variation of the total moment of the sample. Such behavior clearly implies a significant departure from the conventionally accepted Arrhenius relaxation kinetics.