  Magnetization measurements were performed on two sigma-phase samples of
Fe(100-x)V(x) (x=35.5, 34.1) vs. temperature, T, and in DC magnetic field, of
various amplitudes. Using three characteristic temperatures, magnetic phase
diagrams in the H-T plane have been designed testifying to a re-entrant
character of magnetism. The ground magnetic state, a spin glass (SG), was
evidenced to be composed of two sub phases: one with a weak irreversibility and
the other with a strong irreversibility. Two critical lines were reconstructed
within the SG state. Both of them show a crossover from the Gabay-Toulouse
behavior (low field) to a linear and/or quasi-Almeida-Touless behavior. A
strong difference in the effect of the applied magnetic field on the SG phase
in the two samples was revealed.
