COMPARATIVE-STUDY OF LINEAR AND NONLINEAR SUSCEPTIBILITIES OF FINE-PARTICLE AND SPIN-GLASS SYSTEMS - QUANTITATIVE-ANALYSIS BASED ON THE SUPERPARAMAGNETIC BLOCKING MODEL

The ac linear (chi(0)) and nonlinear (chi(2)) susceptibilities of ferr omagnetic cobalt fine particles (which were precipitated in a Cu97Co3 alloy) and of a spin-glass Au96Fe4 alloy have been measured and analyz ed based on the Wohlfarth superparamagnetic blocking model with no int eraction between the particles. The linear susceptibility chi(0) of Cu 97Co3 exhibits the spin-glass-like behavior, and chi(2) has a broad ne gative peak at low temperature and is proportional to T-3 at high temp eratures. The blocking model reproduced the features of observed chi(0 ) and chi(2) in Cu97Co3. On the other hand, chi(2) of Au96Fe4 has a sh arp negative peak at the transition temperature. The behavior of chi(2 ) in Au96Fe4 cannot be explained by the blocking model. It is conclude d that chi(2) gives the key to clarify the difference between the spin -glass transition and the progressive freezing of the particle moments .