FAR-INFRARED ESR STUDY OF CUPRATE COMPOUNDS

Electron spin resonance (ESR) was investigated on the spin-Peierls sys tem CuGeO3 and antiferromagnetic Ba2Cu3O4Cl2 at X-band and far-infrare d regions (FIR). The g-values of CuGeO3 were determined to be 2.17, 2. 26 and 2.11 for Hparallel-toa, Hparallel-tob and Hparallel-toc-axes, r espectively. The temperature dependence of FIR and X-band ESR spectra of CuGeO3 clarified the difference of character among uniform, dimeriz e and high-field magnetic phases. In the Ba2Cu3O4Cl2 system, the reson ance field for Hparallel-toc drastically changes around 30 K, and anti ferromagnetic resonance (AFMR) was observed at 5 K.