title: Direct observation of finite size effects in chains of antiferromagnetically coupled spins.
abstract: Finite spin chains made of few magnetic ions are the ultimate-size structures that can be engineered to perform spin manipulations for quantum information devices. Their spin structure is expected to show finite size effects and its knowledge is of great importance both for fundamental physics and applications. Until now a direct and quantitative measurement of the spatial distribution of the magnetization of such small structures has not been achieved even with the most advanced microscopic techniques. Here we present measurements of the spin density distribution of a finite chain of eight spin-3/2 ions using polarized neutron diffraction. The data reveal edge effects that are a consequence of the finite size and of the parity of the chain and indicate a noncollinear spin arrangement. This is in contrast with the uniform spin distribution observed in the parent closed chain and the collinear arrangement in odd-open chains.
authors.affiliation: ISIS facility, Rutherford Appleton Laboratory, Chilton, Didcot, OX11 0QX Oxfordshire, UK.
authors.forename: T
authors.initials: T
authors.lastname: Guidi
authors.affiliation: Laboratoire Léon Brillouin CEA-CNRS, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France.
authors.forename: B
authors.initials: B
authors.lastname: Gillon
authors.affiliation: Institut Laue-Langevin, 71 avenue des Martyrs, 38042 Grenoble Cedex 9, France.
authors.forename: S A
authors.initials: SA
authors.lastname: Mason
authors.affiliation: Dipartimento di Fisica e Scienze della Terra, Università di Parma, Parco Area delle Scienze n.7/A, 43124 Parma, Italy.
authors.forename: E
authors.initials: E
authors.lastname: Garlatti
authors.affiliation: Dipartimento di Fisica e Scienze della Terra, Università di Parma, Parco Area delle Scienze n.7/A, 43124 Parma, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Carretta
authors.affiliation: Dipartimento di Fisica e Scienze della Terra, Università di Parma, Parco Area delle Scienze n.7/A, 43124 Parma, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Santini
authors.affiliation: Institut Laue-Langevin, 71 avenue des Martyrs, 38042 Grenoble Cedex 9, France.
authors.forename: A
authors.initials: A
authors.lastname: Stunault
authors.affiliation: European Commission, Joint Research Centre (JRC), Institute for Transuranium Elements (ITU), Postfach 2340, D-76125 Karlsruhe, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Caciuffo
authors.affiliation: Institut für Physikalische Chemie, Universität Stuttgart, D-70569 Stuttgart, Germany.
authors.forename: J
authors.initials: J
authors.lastname: van Slageren
authors.affiliation: Helmholtz Zentrum Berlin für Materialien und Energie, D-14109 Berlin, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Klemke
authors.affiliation: Laboratoire Léon Brillouin CEA-CNRS, CEA Saclay, 91191 Gif-sur-Yvette Cedex, France.
authors.forename: A
authors.initials: A
authors.lastname: Cousson
authors.affiliation: School of Chemistry and Photon Science Institute, University of Manchester, M13 9PL Manchester, UK.
authors.forename: G A
authors.initials: GA
authors.lastname: Timco
authors.affiliation: School of Chemistry and Photon Science Institute, University of Manchester, M13 9PL Manchester, UK.
authors.forename: R E P
authors.initials: RE
authors.lastname: Winpenny