title: Barlowite: A Spin-1/2 Antiferromagnet with a Geometrically Perfect Kagome Motif.
abstract: We present thermodynamic studies of a new spin-1/2 antiferromagnet containing undistorted kagome lattices-barlowite Cu_{4}(OH)_{6}FBr. Magnetic susceptibility gives θ_{CW}=-136  K, while long-range order does not happen until T_{N}=15  K with a weak ferromagnetic moment μ<0.1μ_{B}/Cu. A 60 T magnetic field induces a moment less than 0.5μ_{B}/Cu at T=0.6  K. Specific-heat measurements have observed multiple phase transitions at T≪∣θ_{CW}∣. The magnetic entropy of these transitions is merely 18% of k_{B}ln2 per Cu spin. These observations suggest that nontrivial spin textures are realized in barlowite with magnetic frustration. Comparing with the leading spin-liquid candidate herbertsmithite, the superior interkagome environment of barlowite sheds light on new spin-liquid compounds with minimum disorder. The robust perfect geometry of the kagome lattice makes charge doping promising.
authors.affiliation: James Frank Institute and Department of Physics, University of Chicago, Chicago, Illinois 60637, USA and Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA.
authors.forename: Tian-Heng
authors.initials: TH
authors.lastname: Han
authors.affiliation: National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
authors.forename: John
authors.initials: J
authors.lastname: Singleton
authors.affiliation: Materials Science Division, Argonne National Laboratory, Argonne, Illinois 60439, USA and Division of Materials Research, National Science Foundation, Arlington, Virginia 22230, USA.
authors.forename: John A
authors.initials: JA
authors.lastname: Schlueter