Theory of pinning of a spin-density wave by nonmagnetic impurities

In the vicinity of a nonmagnetic impurity locally, a charge-density wave is formed (Friedel oscillation). The pinning of a linearly polarized spin-density wave by an impurity is due to the mismatches of the charge and spin oscillations. For comparison it is shown that for an intermediate-strength impurity the ratio of the pinning energies of a spin-density wave and of a charge-density wave with the same gap is larger than 10^-1 which is well beyond any previous estimation. The experimental consequences are also discussed.