Effects of Ni-doping on the high-magnetic field transport and magnetization properties of single crystals of YBa/sub 2/Cu/sub 3/O/sub 7/

Transport and magnetization measurements are presented for YBa/sub 2/Cu/sub 3-x/Ni/sub x/O/sub 7/ single crystals, where x ranges from 0.0 to 0.03. The presence of nickel systematically sharpens the resistive transition of the material in a high magnetic field, but it does not correlate with the critical current as determined from magnetization measurements. The breadth of the transition for both pure and doped samples, although different, scales according to the model proposed by M. Tinkham Phys. Rev. Lett., (vol.61, p.1658, 1988).