Dilution-induced order in quasi-one-dimensional quantum antiferromagnets

We consider a quasi-one-dimensional spin-S quantum antiferromagnet as a function of dilution x. We show that in some regimes, dilution suppresses quantum fluctuations. For small enough interchain coupling and integer S, the ground state is disordered for x=0, but antiferromagnetically ordered for x>${\mathit{x}}_{\mathit{c}}$. We estimate that for large S, ${\mathit{x}}_{\mathit{c}}$ is exponentially small. This is a novel diffusion-induced ordering transition.