Electrical resistivities of γ-phase Fe_xNi_80−xCr₂₀ alloys

Abstract

In this paper we present a comprehensive investigation of electrical resistivities [ρ(T)] of the γ-phase pseudobinary Fe alloy series Fe_xNi_80−xCr₂₀ in the temperature range 0.4-300 K. These alloys exhibit exotic magnetic behavior at and near the critical composition for ferromagnetism x_c⋍59-63. Special attention has been given to the critical region (x⋍x_c) where we find sharp changes in ρ₀ (zero temperature resistivity) as well as in the temperature dependence of ρ(T). These observations have been explained as arising due to the absence of long-range magnetic order and a change in effective carrier concentration at x⋍x_c. For all x (≤66) these alloys exhibit a resistivity minimum at T=T_min. T_min continuously decreases from approximately 35 K for x≊12 to approximately 6 K for x≊59. ρ(T) for T<T_min shows a rise (ρ∼−√T ) that does not depend on the magnetic state of the alloy. For T_min<T<80 K, ρ(T) away from x_c follows a predominantly T² dependence arising from electron-spin-wave scattering which shows a drastic reduction for x≊x_c. We also compare our data with an α-phase Fe₂₅Cr₇₅ alloy.