  We studied the magnetoresistance due to a spin spiral by solving the
Boltzmann equation. The scattering rates of conduction electrons are calculated
by using the non-perturbative wave function of the conduction electrons and the
non-equilibrium distribution function is obtained by numerically solving the
Boltzmann equation. These enable us to calculate the resistivity of a
sufficiently thin spin spiral. A magnetoresistance ratio of more than 50% is
predicted for a spin spiral with high spin polarization (>0.8) and a small
period (about 1-2 nm).
