An investigation of the relaxation process in the ${\mathrm{Cu}}_3$Au-alloy order-disorder phase transition near the transition point has been performed by observing the time dependence of the electrical resistivity of samples which are quenched from the disordered state to the ordered one very near the phase-transition point. It is found that the relaxation time becomes longer with the approach of the temperature to the order-disorder phase-transition point. The critical index of the Ising relaxation time $\tau$ is obtained as $\Delta =1.20\pm 0.16$.

• Received 27 May 1975

DOI:https://doi.org/10.1103/PhysRevB.13.1119