Coexistence of spin-glass and antiferromagnetic orders in the Ising system Fe0.55Mg0.45Cl2.
The low-temperature phase of the dilute Ising antiferromagnet Fe/sub 0.55/Mg/sub 0.45/Cl/sub 2/ in zero field is studied by specific-heat, ac-susceptibility, and neutron-scattering experiments. We find that in this phase, spin-glass behavior and antiferromagnetic long-range order coexist. Such a mixed-order phase is predicted by the mean-field theory of reentrant spin-glasses, but has never been observed before.