Superconducting transition tuned by spin-polarized carrier injection in YBa2Cu3Oy/LaAlO3/La0.7Ca0.3MnO3 heterostructures

The effect of spin-polarized carrier injection on superconducting transition has been studied on YBa2Cu3Oy/LaAlO3/La0.7Ca0.3MnO3 (superconductor/insulator/ferromagnet) heterostructures. Under the influence of spin-polarized current Iinj injected from the ferromagnetic layers, we have observed a strong suppression of the critical current Ic with the efficiency as large as 4.4 and a shift of the resistive transition curve R(T) to the low temperature side in the superconducting layer. In the measurements of the tunnel current-voltage (Iinj-VT) characteristics between the ferromagnetic layer and the superconducting one, a continuous kink, which leads to a drastic decrease in the differential conductance dIinj/dVT is found at a current, where R appears and Ic disappears. This anomaly is ascribed to the second order phase transition from the superconducting state to the normal one induced by Iinj