Triplet superconducting correlations in oxide heterostructures with a composite ferromagnetic interlayer

The superconducting current induced by the penetration of the long-range triplet component of superconducting correlations into a composite ferromagnetic interlayer has been detected in mesa-heterostructures based on oxide cuprate superconductors YBa$_2$Cu$_3$O$_{7-\delta}$ and Au/Nb bilayer films with the composite oxide interlayer that is made of ferromagnetic films of manganite La$_{0.7}$Sr$_{0.3}$MnO$_3$ and ruthenate SrRuO$_3$ and has a thickness much larger than the length of correlations determined by the exchange field. The deviation of the superconducting current in the mesa-heterostructure with the fraction of the second harmonic of $13\%$ from a sinusoidal current-phase relation has been detected; this deviation can also be due to the generation of the triplet component of superconducting correlations in the ferromagnet.