  Non-linear ac magnetic susceptibility terms viz. quadratic, chi2, and cubic,
chi3, were measured versus temperature and frequency for a series of the
sigma-phase Fe(100-x)Mo(x) (47<x<53) compounds. Clear evidence was found that
the ground magnetic state of the samples is mixed i.e. constituted by two
phases: a spin glass (SG) and a ferromagnet (FM), hence the magnetism of the
investigated samples can be regarded as re-entrant (RSG). Based on the present
data, previously reported magnetic phase diagram has been upgraded [J.
Przewoznik, S. M. Dubiel,J. Alloy. Comp., 630 (2015) 222].
