title: Hyperhoneycomb Iridate β-Li2IrO3 as a platform for Kitaev magnetism.
abstract: A complex iridium oxide β-Li(2)IrO(3) crystallizes in a hyperhoneycomb structure, a three-dimensional analogue of honeycomb lattice, and is found to be a spin-orbital Mott insulator with J(eff)=1/2 moment. Ir ions are connected to the three neighboring Ir ions via Ir-O(2)-Ir bonding planes, which very likely gives rise to bond-dependent ferromagnetic interactions between the J(eff)=1/2 moments, an essential ingredient of Kitaev model with a spin liquid ground state. Dominant ferromagnetic interaction between J(eff)=1/2 moments is indeed confirmed by the temperature dependence of magnetic susceptibility χ(T) which shows a positive Curie-Weiss temperature θ(CW)∼+40  K. A magnetic ordering with a very small entropy change, likely associated with a noncollinear arrangement of J(eff)=1/2 moments, is observed at T(c)=38  K. With the application of magnetic field to the ordered state, a large moment of more than 0.35  μ(B)/Ir is induced above 3 T, a substantially polarized J(eff)=1/2 state. We argue that the close proximity to ferromagnetism and the presence of large fluctuations evidence that the ground state of hyperhoneycomb β-Li(2)IrO(3) is located in close proximity of a Kitaev spin liquid.
authors.affiliation: Max Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany.|Department of Physics and Department of Advanced Materials, University of Tokyo, 7-3-1 Hongo, Tokyo 113-0033, Japan.
authors.forename: T
authors.initials: T
authors.lastname: Takayama
authors.affiliation: Department of Physics and Department of Advanced Materials, University of Tokyo, 7-3-1 Hongo, Tokyo 113-0033, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Kato
authors.affiliation: Max Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany.
authors.forename: R
authors.initials: R
authors.lastname: Dinnebier
authors.affiliation: Max Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Nuss
authors.affiliation: Department of Physics and Department of Advanced Materials, University of Tokyo, 7-3-1 Hongo, Tokyo 113-0033, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Kono
authors.affiliation: Instituto de Física "Gleb Wataghin", Universidade Estadual de Campinas, Campinas, São Paulo 13083-859, Brazil.|Laboratório Nacional de Luz Síncrotron, Campinas, São Paulo 13083-970, Brazil.|Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: L S I
authors.initials: LS
authors.lastname: Veiga
authors.affiliation: Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA.|Department of Physics, Washington University, St. Louis, Missouri 63130, USA.
authors.forename: G
authors.initials: G
authors.lastname: Fabbris
authors.affiliation: Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: D
authors.initials: D
authors.lastname: Haskel
authors.affiliation: Max Planck Institute for Solid State Research, Heisenbergstrasse 1, 70569 Stuttgart, Germany.|Department of Physics and Department of Advanced Materials, University of Tokyo, 7-3-1 Hongo, Tokyo 113-0033, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Takagi