ANOMALOUS MAGNETORESISTANCE BEHAVIOR OF SUPERCONDUCTING ND2-XCEXCUO4-Y SINGLE-CRYSTAL

Magnetoresistance measurements on a superconducting Nd2-xCexCuO4-y Sin gle crystal with T(c) almost-equal-to 7 K were made with magnetic fiel ds H applied parallel (H parallel-to c) and perpendicular (H perpendic ular-to c) to the tetragonal c-axis. For H parallel-to c, the resistiv e superconductive transition curves exhibit a double transition at low temperatures and high magnetic fields. This double resistive transiti on has a maximum near T almost-equal-to 1.1 K, followed by an extremel y sharp transition into the superconducting state. For applied fields of 1 kOe, the resistivity first goes to zero, increases again to a fin ite value and then goes through a second transition. In this region, t he resistivity exhibits non-ohmic behavior for low current densities a nd ohmic behavior for larger measuring currents. The resistivity for H perpendicular-to c does not exhibit any anomalous behavior or a maxim um for 0 less-than-or-equal-to H less-than-or-equal-to 60 kOe and 4 K less-than-or-equal-to T less-than-or-equal-to 7 K.