Ju l 2 00 3 Spin Glasses : A Ghost Story

Extensive experimental and numerical studies of the non-equilibrium dynamics of spin-glasses subjected to temperature or bond perturbations have been performed to investigate chaos and memory effects in different spin glass systems. Temperature shift and cycling experiments were performed on the strongly anisotropic Ising-like system Fe0.5Mn0.5TiO3 and the weakly anisotropic Heisenberg-like system Ag(11 at% Mn) and bond shift and cycling simulations were carried out on a 4d Ising Edwards-Anderson spin glass model. The results of the investigations on the different spin glass systems display qualitatively the same characteristic features and the observed memory phenomena are found to be consistent with predictions from the ghost domain scenario of the droplet scaling model, however in sharp contrast to what is expected from simple length scale arguments.