Han Tian-Heng, Singleton John, Schlueter John A
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.
National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
Phys Rev Lett. 2014 Nov 28;113(22):227203. doi: 10.1103/PhysRevLett.113.227203. Epub 2014 Nov 25.
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.
我们展示了对一种新型含未畸变 kagome 晶格的自旋 1/2 反铁磁体——钡解石 Cu₄(OH)₆FBr 的热力学研究。磁化率给出居里 - 外斯温度 θ₍CW₎ = -136 K，而直到奈尔温度 T₍N₎ = 15 K 才出现长程有序，且具有弱铁磁矩 μ < 0.1μ₍B₎/Cu。在 T = 0.6 K 时，60 T 的磁场诱导出的磁矩小于 0.5μ₍B₎/Cu。比热测量在 T ≪ |θ₍CW₎| 时观测到多个相变。这些相变的磁熵仅为每个 Cu 自旋 k₍B₎ln2 的 18%。这些观测结果表明，在具有磁阻挫的钡解石中实现了非平凡的自旋织构。与主要的自旋液体候选物赫伯史密斯石相比，钡解石优越的层间 kagome 环境为具有最小无序的新型自旋液体化合物提供了线索。kagome 晶格稳健的完美几何结构使电荷掺杂具有前景。
