CRITICAL-CURRENT SUPPRESSION IN A SUPERCONDUCTOR BY INJECTION OF SPIN-POLARIZED CARRIERS FROM A FERROMAGNET

The critical current of a thin film of the high-T-c superconductor DyB a2Cu3O7, when incorporated in a heterostructure in which it is separat ed from a ferromagnetic underlayer of La2/3Sr1/3MnO3 by an undoped ult rathin Lq(2)CuO(4) film, has been found to be strongly suppressed by c urrent flowing in the ferromagnetic film. A control experiment with a Au film replacing the ferromagnet did not shaw such a response, and re sistive heating was ruled out by additional measurements. The effect w ould appear to be caused by pair breaking associated with spin-polariz ed carriers being injected into the superconductor.