HYSTERESIS IN THE INCOMMENSURATE PHASE OF THE SPIN-PEIERLS COMPOUND CUGEO3 - ELECTRON-SPIN-RESONANCE IN HIGH-FIELD

The far-infrared electron spin resonance (ESR) technique is used to pr obe the incommensurate I phase of the spin-Peierls compound CuGeO3. At sufficiently low temperature, the ESR signal is seen to display hyste resis effects. Depending on the sweeping field direction, drastic chan ges are observed on both the linewidth and the resonance field H-r. Fr om accurate determinations of H-r, the observed hysteresis is defined quantitatively. Observed on a large field range, this hysteretic behav ior appears to be a new and basic property of the incommensurate I pha se.