HIGH-FIELD ELECTRON-SPIN-RESONANCE OF CU1-XZNXGEO3

High-field electron spin resonance measurements were made on powder sa mples of Cu1-xZnxGeO3 (x = 0.00, 0.01, 0.92, 0.03, and 0.05) at differ ent frequencies (95, 110, 190, 220, 330, and 440 GHz) at low temperatu res. The spectra of the doped samples show resonances whose positions are dependent on Zn concentration, frequency, and temperature. The ana lysis of the intensity variation of these lines with temperature allow s us to identify them as originating from transitions within states si tuated inside the spin Peierls gap. A qualitative explanation of the d etails of the spectra is possible if we assume that these states in th e gap are associated with ''loose'' spins created near the Zn impuriti es, as recently theoretically predicted. [S0031-9007(98)05429-5].