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

Magnetoresistance measurements on superconducting Nd2-xCexCuO4-y single crystals with T(c) varying from 7 to 19 K were made with magnetic fields H applied parallel (H parallel-to c) and perpendicular (H perpendicular-to c) to the tetragonal c axis. For H parallel-to c, the resistive superconductive transition curves gradually develop Structure at low temperatures and high magnetic fields as T(c) decreases. For the crystals 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 non-Ohmic behavior for low current densities and Ohmic behavior for larger measuring currents. The resistivity for H perpendicular-to c does not exhibit any anomalous behavior or a maximum. The irreversibility line inferred from these measurements is sample dependent.