Ferromagnetism in Melt-spun Gd$_{0.946}$Fe$_{0.054}$*

The ac susceptibility and dc magnetization at various temperatures have been measured for a melt-spun Gd$_{0.946}$ Fe$_{0.054}$ alloy. The grain size was $\approx $100 nm. A sharp paramagnetic-to-ferromagnetic transition was observed at a temperature close to that of pure Gd. Effective critical exponents and the critical temperature $T_{C}$ were extracted by using modified Arrott plots and Kouvel-Fisher analysis. The values obtained were \textit{$\beta $}$_{eff}$ = 0.398 $\pm $ 0.004, \textit{$\gamma $}$_{ eff}$ = 1.24 $\pm $ 0.02, \textit{$\delta $}$_{ eff}$ = 3.83 $\pm $ 0.05, and $T_{C}$ = 290.25 $\pm $ 0.17 K. These exponent values do not satisfy the Widom scaling relation \textit{$\beta \delta $ }= (\textit{$\beta $}+\textit{$\gamma $}). The \textit{$\beta $}$_{eff}$ and \textit{$\gamma $}$_{eff}$ values for ms-Gd$_{0.946}$ Fe$_{0.054}$ are similar to those obtained for pure Gd in the same temperature interval around $T_{C}$. This is in consonance with x-ray microanalysis measurements indicating that the grains are nearly pure Gd. The lower-than-expected value of \textit{$\delta $}$_{eff}$\textit{${\rm g}$ }may be due to the effect of increased anisotropy due to the presence of Fe in the grain-boundary regions.