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Magnetism of Sigma-Phase Fe68V32 Compound

The magnetic phase diagram in the H-T coordinates has been determined for σ-Fe68V32 from the ZFC/FC magnetization measurements. The re-entrant character of magnetism, going from paramagnetic through ferromagnetic to spin-glass (SG) states, has been evidenced. The SG phase is magnetically heterogeneous, because two sub phases can be identified i.e. with the strong (SG-SI) and the weak (SG-WI) irreversibility. The ireversibility, T_irr and the crossover, T_cros, temperatures were quantitatively analysed using the mean-field theory and ϕ_irr=1.6(2) and ϕ_cros=0.91(9) values were obtained. A qualitative agreement with the Gabay-Toulouse model was reached. The isothermal magnetization measurements point to a soft magnetic behaviour of the studied sample. The γ critical exponent was determined with the Kouvel-Fisher approach yielding the value of γ=1.0(1) in line with the mean-field theory.