MAGNETIC MEASUREMENTS OF CUGEO3 BY MEANS OF HIGH MAGNETIC-FIELD

Magnetic properties of CuGeO3 single crystal which shows the spin-Peierls transition below T-sp = 14 K were investigated by means of high field magnetization and susceptibility measurements. The stepwise magnetization was observed in the magnetic fields along the a-, b-, and c-axes up to about 35 T. The magnetization process is different from the case of conventional uniaxially anisotropic antiferromagnets. Such a magnetization process is explained by the crossover model between the ground singlet and the excited magnetic discomensulate state. The main exchange parameter is antiferromagnetic and the estimated value from the high-field magnetization curves is 140 K (97 cm(-1)). A decrease of the critical fields with increasing temperature was observed up to 14 K, the origin of which is considered to be the effect of soft phonons in the spin-Peierls transition.