Effect of Impurity on Magnetic Phase of Spin-Peierls System; Magnetization of Cu1-xZnxGeO3

Magnetizations of spin-Peierls cuprates Cu 1- x Zn x GeO 3 with x =0, 0.005, 0.010, and 0.020 were measured in order to investigate influence of impurities on a magnetic phase. A characteristic change of the magnetization related to a phase transition from dimerized to other phases was seen below a spin-Peierls-transition temperature. The magnetization above 16.0 T shows weak x and temperature dependences. A critical field associated with the phase transition decreases with increasing x . We derived a result that the effects of impurities on the magnetic phase are weaker than on the dimerized phase.