Spin glasses in low DC fields. II. Magnetic viscosity

Abstract

Studies of magnetic viscosity in Au-Fe alloys containing 2 at.% and 7 at.% Fe are presented. The time decays of the remanences IRM and TRM are given for a range of temperatures up to and including the spin glass temperature, T_f. All the decays are best described by the relation M=M₀-Snlnt. S_TRM(T), S_IRM(T) both have maxima at 0.6 T_f. The IRM data suggests a linear relation between S and M₀. Plots of S/M₀=V against T suggest the existence of two regimes of temperature below T_f: (1)Tf, V_IRM nearly constant, independent of T, and much larger than V_TRM. (2) 0.8f, both V_IRM and V_TRM strongly dependent on T and of nearly the same magnitude. These results at low temperatures can be qualitatively reproduced using a very simple activation model for noninteracting fine particles.