title: Ferromagnetically coupled Shastry-Sutherland quantum spin singlets in (CuCl)LaNb₂O₇.
abstract: A thorough crystal structure determination at very low temperature of (CuCl)LaNb₂O₇, originally proposed as a spin-1/2 square-lattice antiferromagnet, is reported thanks to the use of single-crystal x-ray diffraction and powder neutron diffraction. State-of-the-art calculations (maximum entropy method) reveal that (CuCl)LaNb₂O₇ is orthorhombic with Pbam symmetry. First-principles calculations demonstrate that the dominant magnetic interactions are antiferromagnetic between fourth nearest neighbors with a Cu-Cl-Cl-Cu exchange path, which lead to the formation of spin singlets. The two strongest interactions between the singlets are ferromagnetic, which makes (CuCl)LaNb₂O₇ the first system of ferromagnetically coupled Shastry-Sutherland quantum spin singlets.
authors.affiliation: Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Kyoto 615-8510, Japan.
authors.forename: C
authors.initials: C
authors.lastname: Tassel
authors.forename: J
authors.initials: J
authors.lastname: Kang
authors.forename: C
authors.initials: C
authors.lastname: Lee
authors.forename: O
authors.initials: O
authors.lastname: Hernandez
authors.forename: Y
authors.initials: Y
authors.lastname: Qiu
authors.forename: W
authors.initials: W
authors.lastname: Paulus
authors.forename: E
authors.initials: E
authors.lastname: Collet
authors.forename: B
authors.initials: B
authors.lastname: Lake
authors.forename: T
authors.initials: T
authors.lastname: Guidi
authors.forename: M-H
authors.initials: MH
authors.lastname: Whangbo
authors.forename: C
authors.initials: C
authors.lastname: Ritter
authors.forename: H
authors.initials: H
authors.lastname: Kageyama
authors.forename: S-H
authors.initials: SH
authors.lastname: Lee