We report on measurements of supercurrents through the half-metallic ferromagnet ${\text{CrO}}_2$ grown on hexagonal ${\text{Al}}_2{\text{O}}_3$ (sapphire). The current was observed to flow over a distance of 700 nm between two superconducting amorphous ${\text{Mo}}_{70}{\text{Ge}}_{30}$ electrodes which were deposited on the ${\text{CrO}}_2$ 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.

• Received 9 August 2010

DOI:https://doi.org/10.1103/PhysRevB.82.100501