Effective field theory for layered quantum antiferromagnets with nonmagnetic impurities

We propose an effective two-dimensional quantum nonlinear sigma model combined with classical percolation theory to study the magnetic properties of site diluted layered quantum antiferromagnets such as (Formula presented) We calculate the staggered magnetization at zero temperature, (Formula presented) the magnetic correlation length, (Formula presented) the NMR relaxation rate, (Formula presented) and the Néel temperature, (Formula presented) in the renormalized classical regime. Due to quantum fluctuations we find a quantum critical point at (Formula presented) at lower doping than the two-dimensional percolation threshold (Formula presented) We compare our results with the available experimental data.