Crossover induced by spin-density-wave interference in the coherence of singlet electron pairs in Cr

To study the interaction of s-wave superconductivity with spin-density waves (SDWs), we have measured a series of Nb/Cr/Nb Josephson junctions and determined the coherence length ξ describing the decay of the critical current with Cr thickness, L. We observe a crossover in ξ from approximately 14 nm to 4 nm as L increases to 10 nm, which is consistent with a transition from commensurate to incommensurate SDWs expected for this thickness range.