High-field ESR study of the dimerized-incommensurate phase transition in the spin-Peierls compound CuGeO3

The dimerized-incommensurate phase transition in the spin-Peierls compound CuGeO3 is probed using the tunable-frequency high-resolution electron spin resonance technique in magnetic fields up to 17 T. A field-induced development of the soliton-like incommensurate superstructure is clearly indicated as a pronounced increase of the magnon spin resonance linewidth DeltaB, with a DeltaB(max) at B-c similar to 13.8 T. The anomaly is explained in terms of the magnon-soliton scattering and suggests that the soliton-like phase exists close to the boundary of the dimerized-incommensurate phase transition. In addition, magnetic excitation spectra in 0.8% Si-doped CuGeO3 are studied. Some features of the high-field high-resolution tunable-frequency ESR facility recently developed in Tallahassee are presented. (C) 2004 Elsevier B.V. All rights reserved.