Long-range supercurrents through half-metallic ferromagnetic CrO 2

Abstract

We report on measurements of supercurrents through the half-metallic ferromagnet CrO2 grown on hexagonal Al2 O3 (sapphire). The current was observed to flow over a distance of 700 nm between two superconducting amorphous Mo70 Ge30 electrodes which were deposited on the CrO2 film. The critical current Ic increases as function of decreasing temperature. Upon applying an in-plane magnetic field, Ic 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. © 2010 The American Physical Society.