  The static critical phenomenology near the Curie temperature of the
re-entrant metallic alloys Au_0.81Fe_0.19, Ni_0.78Mn_0.22, Ni_0.79Mn_0.21 and
amorphous a-Fe_0.98Zr_0.08 is studied using a variety of experimental
techniques and methods of analysis. We have generally found that the values for
the exponents alpha, beta, gamma and delta depart significantly from the
predictions for the 3D Heisenberg model and are intermediate between these
expectations and the values characterizing a typical spin glass transition.
Comparing the exponents obtained in our work with indices for other re-entrant
systems reported in the literature, a weak universality class may be defined
where the exponents distribute within a certain range around average values.
