Incommensurate state and spin-induced Peierls instability

We propose a novel incommensurate spin state induced by the motion of doped carriers in the one-dimensional double exchange model. The state has an en ergy gap in the charge excitation caused by the 2k(F) instability and an in commensurate structure in the localized spins with k(F) periodicity accompa nied by continuous degeneracy. A metal-insulator transition is proposed in an applied magnetic held. These electronic and magnetic properties are cons istent with the experimental data in the hole doped one-dimensional nickela te Y2-xCaxBaNiO5.