Reversal mechanisms in Tb/Fe multilayers

Reversal processes in Tb/Fe multilayer films are reported. The form of the hysteresis is explained as a function of the number of bilayers in terms of a two-coercivity model. Remanence measurements have been made which provide an insight into the distribution of the energy barriers for the two coercive processes associated with nucleation or domain-wall motion. The time dependence of magnetization has also been measured and this has been used to evaluate fluctuation fields and activation volumes for the series of films. The variation of the fluctuation field with applied field indicates that the two-coercivity model proposed is consistent with the time dependence. An increase is seen in the average activation volume with the number of bilayers.