Coupling of superconductors through a half-metallic ferromagnet: Evidence for a long-range proximity effect

Abstract

Here we examine the ferromagnetic/superconducting proximity effect in half-metallic ferromagnetic ${\text{La}}_{0.7}{\text{Ca}}_{0.3}{\text{MnO}}_3$ and high-$T_{\mathrm{c}}$ superconducting ${\text{YBa}}_2{\text{Cu}}_3{\mathrm{O}}_7$ artificial structures. We have found experimental evidence for the coupling between superconducting layers through ferromagnetic spacers in superlattices. This is consistent with a long-range proximity effect in half-metal ferromagnet/$d$-wave superconductor structures.