title: Correlated trends of coexisting magnetism and superconductivity in optimally electron-doped oxypnictides.
abstract: We report on the recovery of the short-range static magnetic order and on the concomitant degradation of the superconducting state in optimally F-doped SmFe(1-x)Ru(x)AsO(0.85)F(0.15) for 0.1≤x≲0.5. The two reduced order parameters coexist within nanometer-size domains in the FeAs layers and eventually disappear around a common critical threshold x(c)~0.6. Superconductivity and magnetism are shown to be closely related to two distinct well-defined local electronic environments of the FeAs layers. The two transition temperatures, controlled by the isoelectronic and diamagnetic Ru substitution, scale with the volume fraction of the corresponding environments. This fact indicates that superconductivity is assisted by magnetic fluctuations, which are frozen whenever a short-range static order appears, and totally vanish above the magnetic dilution threshold x(c).
authors.affiliation: Dipartimento di Fisica A. Volta and Unità CNISM di Pavia, I-27100 Pavia, Italy. Samuele.Sanna@unipv.it
authors.forename: S
authors.initials: S
authors.lastname: Sanna
authors.forename: P
authors.initials: P
authors.lastname: Carretta
authors.forename: P
authors.initials: P
authors.lastname: Bonfà
authors.forename: G
authors.initials: G
authors.lastname: Prando
authors.forename: G
authors.initials: G
authors.lastname: Allodi
authors.forename: R
authors.initials: R
authors.lastname: De Renzi
authors.forename: T
authors.initials: T
authors.lastname: Shiroka
authors.forename: G
authors.initials: G
authors.lastname: Lamura
authors.forename: A
authors.initials: A
authors.lastname: Martinelli
authors.forename: M
authors.initials: M
authors.lastname: Putti