  Over the last decade it has been shown that magnetic non-collinearity at a
s-wave superconductor/ferromagnet interface is a key ingredient for
spin-singlet to spin-triplet pair conversion. This has been verified in several
synthetic non-collinear magnetic structures. A magnetically soft and hard
ferromagnetic layer combination in a bi-layer structure can function as a field
tunable non-collinear magnetic structure which may offer magnetic-field
tuneability of singlet-to-triplet pair conversion. From magnetization
measurements of Nb/Co/Py/Nb multilayers we demonstrate a reversible enhancement
of the superconducting critical temperature of 400 mK by measuring Tc with and
without a non-collinear magnetic structure between Co and Py. The sensitivity
of Tc in these structures offers the potential for realizing magnetic field
tunable Josephson junctions in which pair conversion and Josephson critical
currents are controllable using modest magnetic fields.
