Magnetization isotherms on ErNi2B2C, Er0.8Tb0.2Ni2B2C and Er0.8Lu0.2Ni2B2Csingle crystals

The magnetic and superconducting properties of ErNi2B2C, Er0.8Tb0.2Ni2B2C a nd Er0.8Lu0.2Ni2B2C single crystals have been studied by DC magnetization m easurements. Those crystals were grown by a floating zone method. The super conducting transitions (T-C) were observed at 8.9, 4.0 and 11.1 K in ErNi2B 2C, Er0.8Tb0.2Ni2B2C and Ero(0.8)Lu(0.2)Ni(2)B(2)C, respectively. The field dependence of magnetization in ErNi2B2C showed a drastic change from negat ive to positive just over H-C1 (400 Oe) in increasing applied field at 1.8 K near the weak ferromagnetic transition. A double meta-magnetic transition at 11 and 19 kOe was also observed, Although the opposite effects on ErNi2 B2C doped with magnetic Tb and non-magnetic Lu were expected, all such anom alies were absent in Ero(0.8)Tb(0.2)Ni(2)B(2)C and Er0.8Lu0.2Ni2B2C. (C) 20 01 Elsevier Science B.V. All rights reserved.