  In a superconductor/ferromagnet hybrid, a magnetically controlled
singlet-to-triplet Cooper pair conversion can modulate the superconducting
critical temperature. In these triplet superconducting spin valves, such
control usually requires inhomogeneous magnetism. However, in the presence of
spin-orbit coupling from an interfacial heavy-metal layer, the singlet/triplet
conversion rate and thus the critical temperature, can be controlled via the
magnetization direction of a single homogeneous ferromagnet. Here, we report
significantly enhanced controllable pair conversion to a triplet state in a
Nb/Pt/Co/Pt superconducting spin valve in which Pt/Co/Pt is homogeneously
magnetized and proximity-coupled to a superconducting layer of Nb. The Co/Pt
interface furthest away from Nb is modified by a sub-nanometer-thick layer of
Cu or Au. We argue that the enhancement is most likely associated from an
improvement of the Co/Pt interface due to the insertion of Cu and Au layers.
Additionally, the higher normalized orbital moments in Au measured using X-ray
magnetic circular dichroism shows that increasing spin-orbit coupling enhances
the triplet proximity effect - an observation supported by our theoretical
calculations. Our results provide a pathway to enhancing triplet pair creation
by interface engineering for device development in superspintronics.
