Evidence for logarithmic corrections to the mean-field critical behavior in the weak itinerant ferromagnetNi3Al

Abstract

The results of an elaborate analysis of high-resolution magnetization and ac suceptibility data unambiguously establish the existence of multiplicative logarithmic corrections (MLC) to single power laws in the asymptotic critical region near the ferromagnetic--paramagnetic phase transition in well-characterized polycrystalline ${\mathrm{Ni}}_{3}\mathrm{Al}$ samples. A crossover from this asymptotic critical behavior to the Gaussian fixed point occurs gradually over a fairly wide temperature range outside the critical regime. Accurate determination of the universal amplitude ratio ${R}_{\ensuremath{\chi}}{=DB}^{\ensuremath{\delta}\ensuremath{-}1}\ensuremath{\Gamma},$ the asymptotic critical exponents $\ensuremath{\beta},$ $\ensuremath{\gamma},$ and $\ensuremath{\delta}$ and the MLC exponents ${x}^{\ensuremath{-}},$ ${x}^{+},$ and ${x}^{0}$ for spontaneous magnetization, initial susceptibility and the magnetization versus field isotherm at ${T=T}_{C}$ (the Curie temperature), respectively, and a detailed comparison between theory and experiment indicate that the weak itinerant ferromagnet ${\mathrm{Ni}}_{3}\mathrm{Al},$ so far as its asymptotic critical behavior is concerned, is an experimental realization of an isotropic $d=3,$ $n=3$ ferromagnet in which the interactions between magnetic moments decay with distance (r) as $J(r)\ensuremath{\sim}{1/r}^{(3/2)d}.$