title: Dimensionality driven spin-flop transition in layered iridates.
abstract: Using resonant x-ray diffraction, we observe an easy c-axis collinear antiferromagnetic structure for the bilayer Sr3Ir2O7, a significant contrast to the single layer Sr2IrO4 with in-plane canted moments. Based on a microscopic model Hamiltonian, we show that the observed spin-flop transition as a function of number of IrO2 layers is due to strong competition among intra- and interlayer bond-directional pseudodipolar interactions of the spin-orbit entangled J(eff)=1/2 moments. With this we unravel the origin of anisotropic exchange interactions in a Mott insulator in the strong spin-orbit coupling regime, which holds the key to the various types of unconventional magnetism proposed in 5d transition metal oxides.
authors.affiliation: Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: J W
authors.initials: JW
authors.lastname: Kim
authors.forename: Y
authors.initials: Y
authors.lastname: Choi
authors.forename: Jungho
authors.initials: J
authors.lastname: Kim
authors.forename: J F
authors.initials: JF
authors.lastname: Mitchell
authors.forename: G
authors.initials: G
authors.lastname: Jackeli
authors.forename: M
authors.initials: M
authors.lastname: Daghofer
authors.forename: J
authors.initials: J
authors.lastname: van den Brink
authors.forename: G
authors.initials: G
authors.lastname: Khaliullin
authors.forename: B J
authors.initials: BJ
authors.lastname: Kim