Investigation of the spin-Peierls phase diagram of CuGeO3: Far-infrared electron spin resonance in high field

Electron spin resonance on single crystals of the spin-Peierls compound CuGeO3 has been performed in magnetic fields up to 17 T in the temperature range 1.8–20 K. Using far-infrared laser frequencies of 245 and 525 GHz we could observe resonance conditions in the three different magnetic phases, i.e., the uniform, the dimerized, and the incommensurate phases for a magnetic field applied parallel to the a axis of the crystal. So for the first time data on electron spin dynamics in the incommensurate phase are reported for fields far from the transition to the dimerised phase. Striking effects concerning the g factor, linewidth, and hysteresis are observed.