MAGNETORESISTANCE OF SUPERCONDUCTING SINGLE-CRYSTALS OF THE ELECTRON-DOPED COMPOUND ND2-XCEXCUO4-Y

Magnetoresistance measurements on superconducting Nd2-xCexCuO4-y singl e crystals with T(c) varying from 7 to 19 K were made with magnetic fi elds H applied parallel (H parallel-to c) and perpendicular (H perpend icular-to c) to the tetragonal c axis. For H parallel-to c, the resist ive superconductive transition curves gradually develop Structure at l ow temperatures and high magnetic fields as T(c) decreases. For the cr ystals with T(c) less than or similar to 1.1 K, this structure evolves into a double resistive transition with a resistivity maximum near T almost-equal-to 1.1 K, followed by an extremely sharp transition into the superconducting state. In this region, the resistivity exhibits no n-Ohmic behavior for low current densities and Ohmic behavior for larg er measuring currents. The resistivity for H perpendicular-to c does n ot exhibit any anomalous behavior or a maximum. The irreversibility li ne inferred from these measurements is sample dependent.