Abstract
In this article, we study the decay rate for system of coupled semi-linear wave equations with power external forces in R-n, including damping term of memory type which is very meaningful. We use the weighted spaces to deal with unbounded domain. Owing to the Faedo-Galerkin method combined with the stable set, we prove the existence of global solution. With the help of some special estimates and generalized Poincare's inequality, we obtain a non classical decay rate for the energy function to generalize a similar result in literature.