  The study of randomness in low-dimensional quantum antiferromagnets is at the
forefront of research in the field of strongly correlated electron systems, yet
there have been relatively few experimental model systems. Complementary
neutron scattering and numerical experiments demonstrate that the spin-diluted
Heisenberg antiferromagnet La2Cu(1-z)(Zn,Mg)zO4 is an excellent model material
for square-lattice site percolation in the extreme quantum limit of spin
one-half. Measurements of the ordered moment and spin correlations provide
important quantitative information for tests of theories for this complex
quantum-impurity problem.
