Observation of standard spin-switch effects in ferromagnet/superconductor/ferromagnet trilayers with a strong ferromagnet

We have measured the superconducting transition temperature T-c of ferromagnet/superconductor/ferromagnet trilayers using Permalloy (Py=Ni84Fe16) as a strongly polarized ferromagnetic material. For a parallel (P) or antiparallel (AP) alignment of the magnetization directions of the outer ferromagnets, we observe a T-c difference as large as 20 mK, with a stronger suppression of superconductivity in the P state than in the AP state. This behavior is opposite to the recent observations of Rusanov [Phys. Rev. B 73, 060505 (2006)] in Py/Nb/Py trilayers, but is consistent with earlier results on trilayers with Ni or CuNi alloy as the ferromagnetic material.