Evidence for spin solitons in spin-Peierls system (DMe-DCNQI)2Li

(DMe-DCNQI) 2 Li has a 1/4-filled π electron system and a spin-Peierls ground state. At low temperatures below 30K, the quasi-one dimensional spin diffusive motion of Curie electron spins are observed with variable frequency ESR measurement. It is a strong evidence for a presence of the spin solitons in a spin gap state of the tetramerized DCNQI chains. The intrachain diffusion rate obeys ∼T 2 below 30 K. The interchain hopping would be originated by the exchange interaction. Under pressure up to 1.5GPa, (DMe-DCNQI) 2 Li maintains highly one dimensional, and the spin soliton diffusion is affected only a little by the pressures.