title: Evidence for zero- and pi-phase order parameters of superconducting Nb/Co tri- and pentalayers from the oscillatory behavior of the transition temperature.
abstract: The oscillation behavior of the superconducting transition temperature Tc as a function of the ferromagnetic Co layer thickness (dCo) has been examined for Nb/Co superconductor(S)/ferromagnetic(F) trilayer series (F/S/F) and pentalayer series (F/S/F/S/F). Tc of the pentalayer series takes a local maximum between dCo=2.0-3.2 nm, where Tc of the trilayer shows a local minimum. This difference in the Tc versus dCo curves provides a clear evidence for the occurrence of the pi phase in the pentalayers, which has been theoretically predicted by Buzdin et al., Radovic et al., and Tagirov.
authors.affiliation: Institute for Materials Research, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Obi
authors.forename: M
authors.initials: M
authors.lastname: Ikebe
authors.forename: H
authors.initials: H
authors.lastname: Fujishiro