Dynamics of Cu-Mn spin-glass films

Using high-resolution SQUID magnetometry the dynamics of a 30-A{} Cu-Mn spin-glass film have been investigated in the time range 10^-5{10}⁴sec. It is found that the temperature dependence of the relaxation times obeys a generalized Arrhenius law, lnτ∝{T}^{{{-}}2.6}$, in accord with predictions for two-dimensional systems from Monte Carlo simulations and the droplet scaling theory. In comparison, results on a ${10}⁴$-A{} Cu-Mn film show typical three-dimensional dynamics with a finite spin-glass temperature. To our knowledge this is the first experimental indication of a crossover behavior from three to two dimensions.