Long range supercurrents in ferromagnetic CrO2 using a multilayer contact structure

We report measurements of long ranged supercurrents through ferromagnetic and fully spin-polarized CrO₂ deposited on TiO₂ substrates. In earlier work, we found supercurrents in films grown on sapphire but not on TiO₂. Here, we employed a special contact arrangement, consisting of a Ni/Cu sandwich between the film and the superconducting amorphous Mo₇₀Ge₃₀ electrodes. The distance between the contacts was almost a micrometer, and we find the critical current density to be significantly higher than found in the films deposited on sapphire. We argue this is due to spin mixing in the Ni/Cu/CrO₂ layer structure, which is helpful in the generation of the odd-frequency spin triplet correlations needed to carry the supercurrent.