We have measured the superconducting transition temperature $T_c$ of $\mathrm{Ni}/\mathrm{Nb}/\mathrm{Ni}$ 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.

• Received 20 June 2005

DOI:https://doi.org/10.1103/PhysRevLett.96.037004