Depinning of Spin-Density-Wave in (TMTSF) 2ClO 4

We have performed the electric conductivity measurements in the spin-density-wave (SDW) phase of (TMTSF) 2 ClO 4 to clarify the dynamics of SDW. The temperature dependence of threshold electric field E T associated with the depinning of SDW was investigated with changing the SDW transition temperature T SDW by the control of anion ordering. The steep temperature dependence was observed for the highest T SDW (6 K) and was explained with the weak pinning by the impurity. The temperature dependence of E T becomes moderate with decreasing T SDW . For T SDW =4 K, it is understood with the strong pinning. The crossover of pinning mechanism from the weak pinning to the strong one was discussed with taking account of the effective impurity concentration due to the disordered array of anion orientation.