Spin injection in perovskite YBa 2Cu 3O 7/La 0.7Ca 0.3MnO 3 double layers and YBa 2Cu 3O 7/SrTiO 3/La 0.7Ca 0.3MnO 3 trilayers in magnetic fields

Abstract

Oxide heterostructures of perovskite YBa 2Cu 3O 7/La 0.7Ca 0.3MnO 3 double layers and YBa 2Cu 3O 7/SrTiO 3/La 0.7Ca 0.3MnO 3 trilayers were made to study quasiparticle injection effects in high- T c superconducting thin films. Transport measurements of the superconducting layer shows that the insulating layer between YBa 2Cu 3O 7 and La 0.7Ca 0.3MnO 3 is important for the spin injection effect. It is found that spin injection effect differs with different injection configurations and it becomes strong with decreasing temperature. Magnetic field was harmful to the spin injection effect. The effect becomes weak with the increasing of magnetic field. It even disappears at high temperature in high magnetic fields. These results can give a useful information to the application of a variety of high- T c superconductor/ferromagnetic heterostructure based devices.