Interplay between superconductivity and spin polarization in thin-film bilayers - An experimental study

Abstract

Thin-film bilayers of the high temperature superconducting compound YBa2Cu3O7−δ (YBCO) and the half-metallic colossal magnetoresistive material La0.67Ca0.33MnO3 (LCMO) have been investigated with electronic transport measurements to study the two materials' competing order parameters to clarify how these interact: whereas ferromagnetism tends to align spin in one direction, superconductivity is based on paring of electron with opposite spin. The focus have been on studying the effect of polarized spin injection coming from LCMO into both the normal and superconducting state of YBCO. One will see that the two materials' competing order parameters lead to fascinating and novel physics emerging close to their interface, like resistive states found both when the superconductor is in its superconducting and normal state. To the authors knowledge, the effect of spin polarized injection into the normal state of a superconductor have not formerly been studied.