  The ground state properties of random-exchange spin-1/2 Heisenberg
antiferromagnets on the square lattice are investigated using a combination of
quantum Monte Carlo simulations, exact numerical diagonalizations, and spin
wave calculations. Whereas arbirarily weak disorder has a drastic effect on 1d
Heisenberg AFM, we find that in two dimensions the characteristics of the
ground state like long-range order is robust even against strong disorder.
While the antiferromagnetic order parameter and the spin stiffness are
exponentially reduced for singular exchange distributions, they vanish only in
the limit of infinite randomness.
