Critical Dynamics in Spin Glasses: Experimental Study and Fractal Model Interpretation

The analysis of the a.c. and d.c. susceptibility of an insulating spin glass allows to determine the temperature dependence of the edge of the distribution of the relaxation times. A fractal model provides a clear physical picture of the critical dynamic behaviour. The value of J can be deduced from that of the critical exponents z , γ, β: J = 0.8 T c . The implications for the field-cooled magnetization behaviour are discussed.