title: Search for ferromagnetic order in overdoped copper-oxide superconductors.
abstract: In copper-oxides that show high-temperature superconductivity (HTS), the critical temperature (Tc) has a dome-shaped doping dependence. The cause of demise of both Tcand superfluid density nson the overdoped side is a major puzzle. A recent study of transport and diamagnetism in a large number of overdoped La2-xSrxCuO4(LSCO) films shows that this cannot be accounted for by disorder within the conventional Bardeen-Cooper-Schrieffer theory. This brings to focus an alternative explanation - competition of HTS with ferromagnetic order, fluctuating in superconducting samples and static beyond the superconductor-to-metal transition. Here, we examine this proposal by growing single-crystal LSCO thin films with doping on both sides of the transition by molecular beam epitaxy, and using polarized neutron reflectometry to measure their magnetic moments. In a heavily overdoped, metallic but non-superconducting LSCO (x = 0.35) film, the spin asymmetry of reflectivity shows a very small static magnetic moment (~2 emu/cm3). Less-doped, superconducting LSCO films show no magnetic moment in neutron reflectivity, both above and below Tc. Therefore, the collapse of HTS with overdoping is not caused by competing ferromagnetic order.
authors.affiliation: Brookhaven National Laboratory, Upton, NY 11973, USA.
authors.forename: J
authors.initials: J
authors.lastname: Wu
authors.affiliation: Quantum Condensed Matter Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
authors.forename: V
authors.initials: V
authors.lastname: Lauter
authors.affiliation: Instrument and Source Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
authors.forename: H
authors.initials: H
authors.lastname: Ambaye
authors.affiliation: Applied Physics Department, Yale University, New Haven, CT 06520, USA.
authors.forename: X
authors.initials: X
authors.lastname: He
authors.affiliation: Brookhaven National Laboratory, Upton, NY 11973, USA.|Applied Physics Department, Yale University, New Haven, CT 06520, USA.
authors.forename: I
authors.initials: I
authors.lastname: Božović