ANTIFERROMAGNETIC LONG-RANGE ORDER CAUSED BY NONMAGNETIC IMPURITIES -MAGNETIZATION OF SINGLE-CRYSTAL CU1-XZNXGEO3

The magnetization was obtained as a function of temperature and magnet ic field of a Cu1-xZnxGeO3 single-crystal with x similar to 0.04. The temperature dependence of the magnetic susceptibility in 0.1 T paralle l to the c axis shows a clear cusp around 4.5 K and decreases rapidly below 4.5 K. There is no hysteresis between the data measured in zero- field-cooling and held-cooling processes, The field dependence of the magnetization parallel to the c axis at 2.0 K exhibits an apparent inc rease around 1.OT, which corresponds to a spin-flop transition. The te mperature and held dependences, the anisotropy, and the absence of the hysteresis undoubtedly prove the occurrence of an antiferromagnetic l ong-range order below 4.5 K instead of the spin-glass-like transition reported previously. Spins below the transition temperature are ordere d almost parallel to the c axis. This is the first report of magnetic long-range order caused by nonmagnetic impurities.