Time dependence and mechanisms of magnetization reversal in Tb–Fe–Co films

Measurements have been made of the time dependence of magnetization, under constant applied field conditions, of thin films of Tb–Fe–Co alloy. The results have been analyzed using a model in which it is assumed that magnetization proceeds by thermal activation of irreversible switching of the magnetic moments of identical elementary volumes. It is assumed that the activation energy for switching, intrinsically the same for all elementary volumes, varies according to local interactions. Values of the fluctuation field Λ are derived and it is found that for the films examined, Λ is independent of magnetization M and the applied field. It is shown that information about the magnetic interactions between the elementary volumes, due to exchange and demagnetizing fields, may be derived from graphs of dM/dt vs M.