title: Measurement of magnetic exchange in ferromagnet-superconductor La2/3Ca1/3MnO3/YBa2Cu3O7 bilayers.
abstract: The existence of coherent magnetic correlations in the normal phase of cuprate high-temperature superconductors has proven difficult to measure directly. Here we report on a study of ferromagnetic-superconductor bilayers of La2/3Ca1/3MnO3/YBa2Cu3O7 (LCMO/YBCO) with varying YBCO layer thicknesses. Using x-ray magnetic circular dichroism, we demonstrate that the ferromagnetic layer induces a Cu magnetic moment in the adjacent high-temperature superconductor. For thin samples, this moment exists at all temperatures below the Curie temperature of the LCMO layer. However, for a YBCO layer thicker than 12 unit cells, the Cu moment is suppressed for temperatures above the superconducting transition, suggesting this to be a direct measurement of magnetic coherence in the normal state of a superconducting oxide.
authors.affiliation: ISIS Facility, Rutherford Appleton Laboratory, Chilton, Oxfordshire, United Kingdom.
authors.forename: S R
authors.initials: SR
authors.lastname: Giblin
authors.forename: J W
authors.initials: JW
authors.lastname: Taylor
authors.forename: J A
authors.initials: JA
authors.lastname: Duffy
authors.forename: M W
authors.initials: MW
authors.lastname: Butchers
authors.forename: C
authors.initials: C
authors.lastname: Utfeld
authors.forename: S B
authors.initials: SB
authors.lastname: Dugdale
authors.forename: T
authors.initials: T
authors.lastname: Nakamura
authors.forename: C
authors.initials: C
authors.lastname: Visani
authors.forename: J
authors.initials: J
authors.lastname: Santamaria