Superconducting transition tuned by spin-polarized carrier injection in YBa 2Cu 3O y/LaAlO 3/La 0.7Ca 0.3MnO 3 heterostructures

Abstract

The effect of spin-polarized carrier injection on superconducting transition has been studied on YBa 2Cu 3O y /LaAlO 3/La 0.7Ca 0.3MnO 3 (superconductor/insulator/ferromagnet) heterostructures. Under the influence of spin-polarized current I inj injected from the ferromagnetic layers, we have observed a strong suppression of the critical current I c 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 ( I inj– V T) characteristics between the ferromagnetic layer and the superconducting one, a continuous kink, which leads to a drastic decrease in the differential conductance d I inj/d V T is found at a current, where R appears and I c disappears. This anomaly is ascribed to the second order phase transition from the superconducting state to the normal one induced by I inj.