Critical behavior in the antiperovskite ferromagnet AlCMn3

Abstract

We have investigated the critical behavior of the antiperovskite ferromagnetic AlCMn${}_{3}$ by bulk magnetization study. The critical exponents ($\ensuremath{\beta}$, $\ensuremath{\gamma}$, and $\ensuremath{\delta}$) 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 $m={f}_{\ifmmode\pm\else\textpm\fi{}}(h)$, where $m$ and $h$ are renormalized magnetization and field, respectively. The critical exponents are confirmed by the Widom scaling law $\ensuremath{\delta}=1+\ensuremath{\gamma}{\ensuremath{\beta}}^{\ensuremath{-}1}$. Apart from a slight increase in $\ensuremath{\beta}$ and $\ensuremath{\gamma}$, 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 $J(r)\ensuremath{\sim}{r}^{\ensuremath{-}4.7}$. 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.