Magnetization-dependent T_c shift in F/S/F trilayers with a strong ferromagnet

We have measured the superconducting transition temperature $T_c$ of Ni/Nb/Ni trilayers when the magnetizations of the two outer Ni layers are parallel (P) and antiparallel (AP). The largest difference in $T_c$ occurs when the Nb thickness is just above the critical thickness at which superconductivity disappears completely. We have observed a difference in $T_c$ between the P and AP states as large as 41 mK - a significant increase over earlier results in samples with higher $T_c$ and with a CuNi alloy in place of the Ni. Our result also demonstrates that strong elemental ferromagnets are promising candidates for future investigations of ferromagnet/superconductor heterostructures.