  We study conductance and spin-polarization fluctuations in one-dimensional
wires with spin-5/2 magnetic impurities (Mn). Our tight-binding Green function
approach goes beyond mean field thus including s-d exchange-induced spin-flip
scattering. In a certain parameter range, we find that spin flip suppresses
conductance fluctuations while enhancing spin-polarization fluctuations. More
importantly, spin-polarization fluctuations attain a universal value 1/3 for
large enough spin flip strengths. This intrinsic spin-polarization fluctuation
may pose a severe limiting factor to the realization of steady spin-polarized
currents in Mn-based 1D wires.
