Determination of susceptibility and specific heat critical exponents for weak itinerant-electron ferromagnets from vibrating reed experiments

Abstract

We report the observation of a linear relationship between the magnetic contribution to Young's modulus, ΔE/E₀, and inverse magnetic susceptibility χ^-1 for amorphous weak itinerant-electron ferromagnets Fe₉₀Zr₁₀ and Fe₉₁Zr₉ in the asymptotic critical region near the ferromagnetic-paramagnetic phase transition. The proportionality ΔE(T)/E₀∝χ^-1(T) is shown to provide as accurate a means of determining the asymptotic critical exponent γ and the leading "correction-to-scaling" amplitudes for susceptibilty from the ΔE/E₀ data as a direct measurement of magnetic susceptibilty does. Similarly, the well-known relation between the magnetic contributions to sound velocity and specific heat is fully exploited to extract accurate estimates for the universal critical amplitude ratio A⁺/A^- and the asymptotic critical exponents α^± for the specific heat from the sound velocity data. The presently determined values of α^± and γ, together with the reported value for spontaneous magnetization critical exponent β, not only obey the scaling equalities α⁺=α^- and α+2β+γ =2 but also assert that the atomic magnetic moments in the alloys in question interact with one another through an attractive interaction which decays faster than 1/r⁵ with the interatomic spacing, r.