Phase Transition from Superconducting to Normal State Induced by Spin Injection in Manganite/Cuprate/Au Double Tunnel Junctions

摘要

We have studied the voltage-current characteristics in La_(0.7)Ca_(0.3)MnO_(3)/YBa_(2)Cu_(3)O_(y)/Au, ferromagnet/superconductor/nonmagnetic metal, double tunnel junctions. Near T_(c), the tunnel conductance G(V) reveals a step-like decrease, which can be ascribed to the phenomenon of the phase transition from superconducting state to normal one caused by the spin accumulation effect. With decreasing temperature T, the step in G(V) changes to the sharp peak. Our results indicate that the spin-injection-induced phase transition has a nature of a first order transition at low T.