DYNAMIC STUDY OF IRON-NITRIDE FINE-PARTICLE SYSTEM - FIELD-DEPENDENCEOF THE BLOCKING TEMPERATURE

The AC susceptibility chi' + i chi'' of frozen iron-nitride magnetic f luids was measured in static fields. The blocking temperature is estim ated from the maximum of out-of-phase component chi'' against the freq uency of measurement, For a diluted sample, the field dependence of th e blocking temperature is explained by the Ni el superparamagnetic (bl ocking) model for an isolated particle. For a dense sample, the blocki ng temperature is much higher than that for the diluted sample in a ze ro field and intensively decreases with the power of 2/3 of the magnet ic field in the lower field range. (C) 1998 Elsevier Science B.V. All rights reserved.