Controlled Injection of Spin-Triplet Supercurrents into a Strong Ferromagnet

Abstract

Maintaining the Supercurrent When a superconductor is placed in contact with a ferromagnet, the antiparallel spin pairs that form the supercurrent are expected to be broken almost immediately upon entering the ferromagnet, which tends to orient spins parallel to each other. If the supercurrent survives for more than a few nanometers, it is assumed that a change of pairing symmetry has taken place, with the spin-singlet pairs having been converted into spin-triplets. Magnetic inhomogeneity at the superconductor-ferromagnet interface is thought to account for this change. Robinson et al. (p. 59 , published online 10 June) have now been able to observe long-ranged supercurrents in a symmetric junction consisting of a superconductor, a conical magnet, and a ferromagnet. The conical magnet layer provided the required inhomogeneity, and varying its thickness enabled control over the magnitude of the current.