Using high-resolution SQUID magnetometry the dynamics of a 30-Å Cu-Mn spin-glass film have been investigated in the time range ${10}^{\mathrm{-}5}$${<10\mathrm{}}^4$ sec. It is found that the temperature dependence of the relaxation times obeys a generalized Arrhenius law, lnτ∝$T^{\mathrm{-}2.6}$, in accord with predictions for two-dimensional systems from Monte Carlo simulations and the droplet scaling theory. In comparison, results on a ${10}^4$-Å 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.

• Received 24 March 1989

DOI:https://doi.org/10.1103/PhysRevB.40.869