PHASE ORDERING IN RANDOM-MEDIA

The phase-ordering process in random media, which alters the local exchange coupling, is studied with the nonconserved time-dependent Ginzburg-Landau model. At the late stage of phase ordering the effects of randomness, which are not sufficiently strong to destroy long-range order are essential when the spatial dimension d is less than 4. In cases of nonconserved order-parameter dynamics with negligible noise we find that (i) the characteristic length of domains l(t) displays a crossover from a diffusive growth l(t) is similar to t1/2 to a freezing l(t) is similar to rho0(-1/(4-d)) with the impurity concentration rho0 and (ii) the scaling form of the spatial correlation function is the same as that in a system without randomness.