CRITICAL-BEHAVIOR OF LINEAR AND NONLINEAR SUSCEPTIBILITIES NEAR CURIE-TEMPERATURE IN AU82FE18 ALLOY

The ac linear (chi0) and nonlinear (chi2) susceptibilities of Au82Fe18 alloy have been studied around the Curie temperature T(c), to make clear the feature of the magnetic phase transition. In very low field measurements, the nonlinear susceptibility chi2 is observed only in the vicinity of T(c) and the temperature dependence of chi2 is in good agreement with theoretical expectations in the transition from a ferromagnetic phase to a paramagnetic phase. Analysis of the critical behavior of chi0 and chi2 yields the susceptibility exponent gamma=1.33+/-0.05 and the nonlinear susceptibility exponent gamma2=4.82+/-0.50. These values are very close to theoretical predictions for 3d-Heisenberg pure ferromagnets.