Critical Current Suppression in a Superconductor by Injection of Spin-Polarized Carriers from a Ferromagnet

Abstract

The critical current of a thin film of the high- $T_c$ superconductor ${\mathrm{DyBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_7$, when incorporated in a heterostructure in which it is separated from a ferromagnetic underlayer of ${\mathrm{La}}_{2/3}{\mathrm{Sr}}_{1/3}{\mathrm{MnO}}_3$ by an undoped ultrathin ${\mathrm{La}}_2{\mathrm{CuO}}_4$ film, has been found to be strongly suppressed by current flowing in the ferromagnetic film. A control experiment with a Au film replacing the ferromagnet did not show such a response, and resistive heating was ruled out by additional measurements. The effect would appear to be caused by pair breaking associated with spin-polarized carriers being injected into the superconductor.