DYNAMICS OF THE DILUTED ISING ANTIFERROMAGNET FE0.46ZN0.54F2 IN THE (H,T) PLANE

We present a detailed study of the dynamics of the diluted Ising antiferromagnet Fe0.46%Zn0.54%F2, a test model for the random-field Ising model, over a wide range of temperatures and magnetic fields below the equilibrium - transition temperature T(c)(H). Using a high-field superconducting-quantum-interference-device magnetometer, we measure the macroscopic magnetization M through a variety of cooling and field-cycling protocols. We find a dynamic behavior, at high fields below the transition temperature, considerably richer than expected in both magnetization-relaxation and field-cycling experiments. At very low temperatures the dynamics are frozen because of the Ising excitation gap. Our results are summarized in a dynamical phase diagram.