By tempered Monte Carlo simulations, we study site-diluted Ising systems of
magnetic dipoles. All dipoles are randomly placed on a fraction x of all L^3
sites of a simple cubic lattice, and point along a given crystalline axis. For
x_c< x<=1, where x_c = 0.65, we find an antiferromagnetic phase below a
temperature which vanishes as x tends to x_c from above. At lower values of x,
we find an equilibrium spin-glass (SG) phase below a temperature given by k_B
T_{sg} = x e_d, where e_d is a nearest neighbor dipole-dipole interaction
energy. We study (a) the relative mean square deviation D_q^2 of |q|, where q
is the SG overlap parameter, and (b) xi_L/L, where xi_L is a correlation
length. From their variation with temperature and system size, we determine
T_{sg}. In the SG phase, we find (i) the mean values and decrease
algebraically with L as L increases, (ii) double peaked, but wide,
distributions of q/ appear to be independent of L, and (iii) xi_L/L rises
with L at constant T, but extrapolations to 1/L -> 0 give finite values. All of
this is consistent with quasi-long-range order in the SG phase.Comment: 15 LaTeX pages, 15 figures, 3 tables. (typos fixed in Appendix A
