Critical behavior of the layered ferromagnet Fe_1/4TaS₂

The critical behavior of single-crystalline layered ferromagnet Fe_1/4TaS₂ were studied by bulk dc magnetization around the paramagnetic to ferromagnetic phase transition. Critical exponents β = 0.459(6) and γ = 1.205(11) are extracted from the Kouvel-Fisher plot, whereas δ = 3.69(1) is obtained by the critical isotherm analysis at T_c = 100.7 K. These critical exponents obey the Widom scaling relation δ=1+γ/β. Moreover, the self-consistency and reliability of the results are further verified by scaling equations. The determined exponents match well with those calculated from the results of renormalization group approach, and our analysis suggests that Fe_1/4TaS₂ possesses three-dimensional long-range magnetic interactions with the exchange distance decaying as J(r) ≈ r^−4.8.