Abstract
The longitudinal and the transverse magnetoresistances of disordered NiMn alloys with about 21, 26, 28, and 30 at. % Mn have been measured in magnetic fields up to ∼75 kG and in the temperature range 1.2–80 K. For the 21 at. % Mn alloy the magnetoresistance is anisotropic (Δ ρ>0, Δ ρ0 vs H curves. When the sample is prepared with a remanent magnetization both Δ ρ/ρ0 and its field derivative undergo a discontinuity at H∼−1 kG and T=1.2 K.