Quasi-one-dimensional diffusive motion of spin solitons in the spin-Peierls state of (DMe-DCNQI)2Li

(DMe-DCNQI)(2)Li is a 1/4 filled spin-Peierls (SP) system with the SP transition temperature T-sp similar to 65 K. Using frequency variable ESR at temperatures enough below T-sp, the existence of spin solitons which could arise from domains with finite chain length, is demonstrated. It is also found that T-sp is enhanced by hydrostatic pressure and can be reproduced well with Cross-Fisher's relation. Within our knowledge, this is the first example of such good consistency with theory in pressure dependence of T-sp. This is probably due to a high one dimensionality of the electronic structure in (DMe-DCNQI)(2)Li, even under high pressures. (C) 2003 Elsevier Science B.V. All rights reserved.