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

We present data, obtained from measured Co/Ni multilayers, that indicate th at the magnetic relaxation processes take place through a nucleation-coales cence sequence, and thus crucially implicates the existance of exchange and dipolar interactions. Depending on the layer thickness the relaxation proc eeds either through a single global stage or through several partial ones. In both cases the relaxation stages involve a time lapse during which the m acroscopic state of the system evolves very slowly, followed by a sharp var iation of the total moment of the sample. Such behavior clearly implies a s ignificant departure from the conventionally accepted Arrhenius relaxation kinetics. (C) 1999 American Institute of Physics. [S0003-6951(99)04432-0].