Magnetization-orientation dependence of the superconducting transition temperature in the ferromagnet-superconductor-ferromagnet system: CuNi/Nb/CuNi

The superconducting critical temperature (T(c)) of ferromagnet-superconductor-ferromagnet systems has been predicted to exhibit a dependence on the magnetization orientation of the ferromagnetic layers such that T(AP)(c)>T(P)(c) for parallel (P) and antiparallel (AP) configurations of the two ferromagnetic layers. We have grown CuNi/Nb/CuNi films via magnetron sputtering and confirmed the theoretical prediction by measuring the resistance of the system as a function of temperature and magnetic field. We find an approximately 25% resistance drop occurs near T(c) in Cu0.47Ni0.53(5 nm)/Nb(18)/CuNi(5) when the two CuNi layers change their magnetization directions from parallel to antiparallel, whereas there is no corresponding resistance change in the normal state.