LOW-TEMPERATURE MAGNETORESISTANCE OF GAMMA-PHASE FEXNI80-XCR20 ALLOYSNEAR THE CRITICAL COMPOSITION FOR FERROMAGNETISM

We present a comprehensive study of magnetoresistance (MR) of the crys talline pseudobinary gamma-phase Fe alloy series FexNi80-xCr20 (50 les s than or equal to x less than or equal to 66). This alloy series show s exotic magnetic phases as the composition (x) is varied. It has a cr itical composition for ferromagnetism at x=x(c) similar or equal to 59 -60. MR was measured in the temperature range 1.7-110 K and up to a fi eld of 7 T. The observed MR was small and the change was less than or equal to 1%. The temperature dependence of MR was found to contain a p ositive and a negative contribution. The positive term was found to be proportional to H-2 and it dominates at high field and high temperatu res. We explain this as a manifestation of Kohler's rule. The negative MR was found to have a quadratic dependence on magnetization M. The m agnitude of the negative MR reaches a maximum as x --> x(c).