Magnetism and magnetic phase diagram of sigma-phase Fe68V32 compound

Abstract 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 Tirr and Tcros were quantitatively analysed using the mean-field theory and values of related critical exponents ϕirr = 1.6 (2) and ϕcros = 0.91 (9) were obtained. A qualitative agreement with the Gabay-Toulouse model was reached. The isothermal magnetization measurements point to a soft magnetic behavior 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.