Critical properties of the double-exchange ferromagnet Nd 0.6 Pb 0.4 MnO 3

Results of a study of dc magnetization $M(T,H),$ performed on a ${\mathrm{Nd}}_{0.6}{\mathrm{Pb}}_{0.4}{\mathrm{MnO}}_{3}$ single crystal in the temperature range around ${T}_{C}$ (Curie temperature) which embraces the supposed critical region $|\ensuremath{\varepsilon}|=|T\ensuremath{-}{T}_{C}|{/T}_{C}l~0.05$ are reported. The magnetic data analyzed in the critical region using the Kouvel-Fisher method give the values for the ${T}_{C}=156.47\ifmmode\pm\else\textpm\fi{}0.06\mathrm{K}$ and the critical exponents $\ensuremath{\beta}=0.374\ifmmode\pm\else\textpm\fi{}0.006$ (from the temperature dependence of magnetization) and $\ensuremath{\gamma}=1.329\ifmmode\pm\else\textpm\fi{}0.003$ (from the temperature dependence of initial susceptibility). The critical isotherm ${M(T}_{C},H)$ gives $\ensuremath{\delta}=4.54\ifmmode\pm\else\textpm\fi{}0.10.$ Thus the scaling law $\ensuremath{\gamma}+\ensuremath{\beta}=\ensuremath{\delta}\ensuremath{\beta}$ is fulfilled. The critical exponents obey the single scaling equation of state $M(H,\ensuremath{\varepsilon})={\ensuremath{\varepsilon}}^{\ensuremath{\beta}}{f}_{\ifmmode\pm\else\textpm\fi{}}(H/{\ensuremath{\varepsilon}}^{\ensuremath{\beta}+\ensuremath{\gamma}}),$ where ${f}_{+}$ for $Tg{T}_{C}$ and ${f}_{\ensuremath{-}}$ for $Tl{T}_{C}.$ The exponent values are very close to those expected for the universality class of three-dimensional Heisenberg ferromagnets with short-range interactions.