Spin injection in oxide ferromagnet/superconductor structures.

摘要

High-quality films and heterostructures of ferromagnets ;The composition, crystal lattice and surface of the films and heterostructures have been characterized by reflection high energy electron diffraction, high-resolution X-ray diffraction, Rutherford backscattering, ion channeling, scanning electron microscopy, and scanning tunneling microscopy. Electrical properties of the films and heterostructures have been studied in the wide range of temperatures and magnetic fields using four probe measurements in flow-through and conventional cryostats. Magnetic properties have been studied using SQUID magnetometry.;It was shown that the injection of the spin-polarized carriers from the ferromagnet into the superconductor leads to a suppression of such characteristics of the superconductor as its critical temperature and critical current density.;The electric properties of the ferromagnet/superconductor interface have also been investigated. It was shown that the differential resistance of the interface depends strongly on the voltage bias across the interface. This dependence has a peak around zero-bias that is temperature and magnetic field dependent. The peak in differential resistance vs. voltage bias disappeared above the superconducting transition temperature.;The scientific significance of the observed effects is discussed and possible applications are proposed.