Universal curve and long-range ferromagnetic order in the intermetallic compound Mn_0.92Sn_0.08CoGe

In this work, the universal curve, critical behavior and magnetocaloric effect of the intermetallic compound Mn_0.92Sn_0.08CoGe around room temperature have been investigated. Magnetic data indicate that Mn_0.92Sn_0.08CoGe exhibits the characteristic of second-order transition around the room temperature 286 K. Moreover, the universal curve, well fitted by a Lorentz function, further proves second-order nature of the transition. The critical exponents obtained from various techniques such as modified Arrott plot (MAP), Kouvel-Fisher (KF) method, and critical isotherm analysis (M(T _C)) are found to basically fulfill the Widom scaling relation: δ = 1 + γ/β and obey the scaling equation of M (H, ε) = ε ^β f _±(H/ε ^β+γ), revealing the extracted critical exponents are reliable. The obtained critical exponents are close to the prediction of the mean-field model, suggesting the existence of long-range magnetic interactions coupling with the exchange distance decaying as J (r) ≈ r ^−4.4. (paper)