Influence of Spin Injection on the In-Plane and Out-of-Plane Transport Properties of BSCCO Single Crystal

We have studied the influence of spin injection on the in-plane and out-of-plane transport properties of Bi₂Sr₂CaCu₂O_y. Two different types of samples have been fabricated. One is a mesa composed of Co/Au/Bi₂Sr₂CaCu₂O_y for the out-of-plane transport measurement, and another is Bi₂Sr₂CaCu₂O_y single crystal bridge for the in-plane transport measurement. For the former, the hysteretic field dependence of I_c of intrinsic Josephson junctions (IJJs) in the mesa, due to the spin injection effect, was observed at 77 K. Moreover, it was observed that the hysteresis in the I_c-B curves decreased with increasing the number of IJJs in mesas. This suggests that the contribution of the Josephson effect to the c-axis transport property becomes larger than that of the spin injection effect with the increase in the number of junction. On the other hand, for the latter, hysteretic field dependence of the magnetoresistance was observed. These results give us the evidence for the superconductivity suppression of Bi₂Sr₂CaCu₂O_y due to the injection of spin-polarized quasiparticles.