Enhancement of the superconducting critical temperature in Nb/Py/Nb trilayers

Superconducting critical temperature, Tc, have been measured in a series of Nb/Py/Nb (here Py = Ni80Fe20) trilayers having constant Py thickness, dPy = 432 nm, and variable Nb thickness, dNb, in the range 20-30 nm. We have observed that, for dNb between 23 and 27 nm, resistive transitions shift towards higher temperature if stripe domains are present in the Py layer. We relate those observations to the non-homogeneous magnetization in the Py layer due to the presence of stripe domain structures.