Critical behavior in the antiperovskite ferromagnet AlCMn3

We have investigated the critical behavior of the antiperovskite ferromagnetic AlCMn3 by bulk magnetization study. The critical exponents (beta, gamma, and delta) have been obtained by different methods, such as a modified Arrott plot, the Kouvel-Fisher method, and critical isotherm analysis. With these critical exponents, the experimental M-T-H relations below and above Curie temperature collapse into two universal branches, fulfilling the single scaling equation m = f(perpendicular to)(h), where m and h are renormalized magnetization and field, respectively. The critical exponents are confirmed by the Widom scaling law delta = 1 + gamma beta(-1). Apart from a slight increase in beta and gamma, the deduced critical exponents are very close to the theoretical values of the mean-field model, indicating the existence of a long-range ferromagnetic interaction. In addition, the exchange distance is obtained as J(r) similar to r(-4.7). We suggest that the competition between the localized Mn-Mn magnetic interaction and itinerant Mn-C hybridization should be responsible for the critical behavior in this system.