Low-temperature magnetoresistance of γ-phase Fe_xNi_80−xCr₂₀ alloys near the critical composition for ferromagnetism

Abstract

We present a comprehensive study of magnetoresistance (MR) of the crystalline pseudobinary γ-phase Fe alloy series Fe_xNi_80−xCr₂₀ (50≤x≤66). This alloy series shows exotic magnetic phases as the composition (x) is varied. It has a critical composition for ferromagnetism at x=x_c≃59-60. MR was measured in the temperature range 1.7-110 K and up to a field of 7 T. The observed MR was small and the change was ≤1%. The temperature dependence of MR was found to contain a positive and a negative contribution. The positive term was found to be ∝H² and it dominates at high field and high temperatures. We explain this as a manifestation of Kohler's rule. The negative MR was found to have a quadratic dependence on magnetization M. The magnitude of the negative MR reaches a maximum as x→x_c.