Long-range supercurrents through half-metallic ferromagnetic CrO2

We report on measurements of supercurrents through the half-metallic ferromagnet CrO2 grown on hexagonal Al2O3 (sapphire). The current was observed to flow over a distance of 700 nm between two superconducting amorphous Mo70Ge30 electrodes which were deposited on the CrO2 film. The critical current I-c increases as function of decreasing temperature. Upon applying an in-plane magnetic field, I-c goes through a maximum at the rather high field of 80 mT. We believe this to be a long-range proximity effect in the ferromagnet, carried by odd-frequency pairing correlations.