We report on magnetic properties in the spin density wave (SDW) phase
of (TMTSF)2X through analyses of H-1-NMR and static magnetization meas
urements. We observed a large enhancement of the spin-lattice relaxati
on rate of H-1 below the SDW transition temperature (T(SDW)). The temp
erature of this peak is proportional to the T(SDW). The measurements o
f magnetization also support this result. These are attributed to the
new phase transition within the SDW state.