title: Antiferromagnetic S=1/2 spin chain driven by p-orbital ordering in CsO2.
abstract: We demonstrate, using a combination of experiment and density functional theory, that orbital ordering drives the formation of a one-dimensional (1D) S=1/2 antiferromagnetic spin chain in the 3D rocksalt structure of cesium superoxide (CsO2). The magnetic superoxide anion (O2(-)) exhibits degeneracy of its 2p-derived molecular orbitals, which is lifted by a structural distortion on cooling. A spin chain is then formed by zigzag ordering of the half-filled superoxide orbitals, promoting a superexchange pathway mediated by the p(z) orbitals of Cs(+) along only one crystal direction. This scenario is analogous to the 3d-orbital-driven spin chain found in the perovskite KCuF3 and is the first example of an inorganic quantum spin system with unpaired p electrons.
authors.affiliation: Zernike Institute for Advanced Materials, University of Groningen, Groningen, The Netherlands.
authors.forename: Syarif
authors.initials: S
authors.lastname: Riyadi
authors.forename: Baomin
authors.initials: B
authors.lastname: Zhang
authors.forename: Robert A
authors.initials: RA
authors.lastname: de Groot
authors.forename: Antonio
authors.initials: A
authors.lastname: Caretta
authors.forename: Paul H M
authors.initials: PH
authors.lastname: van Loosdrecht
authors.forename: Thomas T M
authors.initials: TT
authors.lastname: Palstra
authors.forename: Graeme R
authors.initials: GR
authors.lastname: Blake