  Josephson junctions with s-wave superconductors (S) and multiple
ferromagnetic (F) layers carry spin-triplet supercurrents in the presence of
magnetically inhomogeneous spin-mixer interfaces. Here, we report magnetic
Josephson junctions with exchange-spring and double exchange-spring
("spin-mixer") Co/Py interfaces. At the Co/Py interface, exchange coupling is
strong with respect to the magnetic anisotropy of Py and so, depending on the
direction and magnitude of an external magnetic field, a non-collinear magnetic
structure forms in Py creating the necessary magnetic inhomogeneity for
singlet-to-triplet pair conversion. We detect supercurrents through Py with a
thickness exceeding 10 nm, which is much larger than the singlet pair coherence
length, suggesting the propagation of magnetically tuneable triplet
supercurrents.
