Validity of the generalized Curie-Weiss law in ferromagnetic systems with 'frozen' disorder

Abstract

Contrary to the popular belief that the use of nonlinear scaling variables enhances the width of the asymptotic critical region enormously and hence the asymptotic value of the critical exponent γ can be deduced from susceptibility data taken over a wide temperature range above T_c (Curie point), our results unambiguously demonstrate that, though the scaling in nonlinear variables (generalized Curie-Weiss law) is valid over as wide a temperature range as T_c ≤T ≤1.7T_c, width of the asymptotic critical region as well as the values of T_c, γ, asymptotic and non-analytic correction amplitudes remain unaltered when instead of the linear scaling variables nonlinear scaling variables are used. The generalized Curie-Weiss law permits an accurate determination of the atomic moment in the paramagnetic state, q_c. The finding that the ratio q_c /q_s » 1 and scales with T_c ^-1 or T_c ^-2/3 provides a strong experimental evidence for weak itinerant ferromagnetism in the investigated amorphous alloys.