Coexistence of Spin-Glass and Antiferromagnetic Orders in the Ising System Fe0.55Mg0.45Cl2

The low-temperature phase of the dilute Ising antiferromagnet Fe0.55Mg0.45Cl2 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. © 1985 The American Physical Society.