  Random quenched dilution of the triangular-lattice antiferromagnetic Ising
model locally relieves frustration, leading to ordering phenomena. We have
studied this system, under such dilution of one sublattice, using hard-spin
mean-field theory. After a threshold dilution, two sublattices develop non-zero
magnetizations of equal magnitude and opposite signs, as all three sublattices
exhibit spin-glass order. In this phase, multiple sets of ordered solutions
occur. A phase diagram is obtained in dilution fraction and temperature.
