Rate-dependent coercivity and activation volumes in nanocrystalline FeZrBCu alloys

Summary form only given. In nanocrystalline grain/amorphous matrix systems well above the Curie temperature of the amorphous part, the system does not behave like a system of superparamagnetic particles, as it should be at those temperatures, but still exhibits hysteresis. This effect could be explained by invoking the existence of some correlation length larger then the grain size. Since thermal activation is connected to a typical activation volume, this correlation length may also be estimated by studying the rate dependence of hysteresis properties. We have applied this method to the study of Fe/sub 86/Zr/sub 7/B/sub 6/Cu/sub 1/ ribbons. Hysteresis loops have been measured as a function of temperature and crystalline fraction. The coercivity was studied as a function of the field rate in the range 10/sup 2/-10/sup 7/ Am/sup -1/ s/sup -1/.