Dynamics of Cu-Mn spin-glass films

Abstract

Using high-resolution SQUID magnetometry the dynamics of a 30-A\r{} Cu-Mn spin-glass film have been investigated in the time range ${10}^{\mathrm{\ensuremath{-}}5}$${10}^{4}$ sec. It is found that the temperature dependence of the relaxation times obeys a generalized Arrhenius law, ln\ensuremath{\tau}\ensuremath{\propto}${T}^{\mathrm{\ensuremath{-}}2.6}$, 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\r{} 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.