Domain growth by aging in nonequilibrium two-dimensional random Ising systems.

Abstract

The ac susceptibility in the two-dimensional Ising spin glass ${\mathrm{Rb}}_{2}$${\mathrm{Cu}}_{0.67}$${\mathrm{Co}}_{0.33}$${\mathrm{F}}_{4}$ and the two-dimensional random-exchange Ising ferromagnet ${\mathrm{Rb}}_{2}$${\mathrm{Cu}}_{0.89}$${\mathrm{Co}}_{0.11}$${\mathrm{F}}_{4}$ is observed to relax towards equilibrium on a time scale of hours following fast quenching to 3.9 K. Scaling of the in-phase and out-of-phase susceptibilities yields that the ordered domains grow according to (lnt${)}^{1/\mathrm{\ensuremath{\psi}}}$, with t expressed in units of a microscopic time, and \ensuremath{\psi}=1.07\ifmmode\pm\else\textpm\fi{}0.10 and 0.20\ifmmode\pm\else\textpm\fi{}0.05, respectively. Both values are in agreement with recent theoretical results and numerical simulations.