Dynamical studies of the response function in a spin glass

Abstract

Experiments on the time dependence of the response function of a Ag(11 at% Mn) spin glass at a temperature below the zero-field spin glass temperature are used to explore the non-equilibrium nature of the spin glass phase. It is found that the response function is only governed by the thermal history in the very neighbourhood of the actual measurement temperature. The thermal history outside this narrow region is irrelevant to the measured response. This implies that the thermal history during cooling (cooling rate, wait times, etc.) is imprinted in the spin structure and that the fragment of this history surrounding any higher temperature can be recalled when this temperature is recovered. The observations are discussed in the light of a real-space droplet/domain phenomenology. The results also emphasise the importance of using controlled cooling procedures to acquire interpretable and reproducible experimental results on the non-equilibrium dynamics in spin glasses.