Barlowite: A Spin-1/2 Antiferromagnet with a Geometrically Perfect Kagome Motif

• Published in: Physical review letters Vol. 113; no. 22; p. 227203
• Main Authors: Han, Tian-Heng, Singleton, John, Schlueter, John A
• Format: Journal Article
• Language: English
• Published: United States 28.11.2014
• ISSN: 1079-7114
• DOI: 10.1103/PhysRevLett.113.227203

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.