1202.4729 (Tianheng Han et al.)

Refining the Spin Hamiltonian in the Spin-1/2 Kagome Lattice
Antiferromagnet ZnCu$_{3}$(OH)$_{6}$Cl$_{2}$ using Single Crystals    [PDF]

Tianheng Han, Shaoyan Chu, Young S Lee

We report thermodynamic measurements of the S=1/2 kagome lattice
antiferromagnet ZnCu$_{3}$(OH)$_{6}$Cl$_{2}$, a promising candidate system with
a spin liquid ground state. Using single crystal samples, the magnetic
susceptibility both perpendicular and parallel to the kagome plane has been
measured. A small, temperature-dependent anisotropy has been observed, where
$\chi_{z}/ \chi_{p} > 1$ at high temperatures and $\chi_{z}/ \chi_{p} < 1$ at
low temperatures. Fits of the high-temperature data to a Curie-Weiss model also
reveal an anisotropy. By comparing with theoretical calculations, the presence
of a small easy-axis exchange anisotropy can be deduced as the primary
perturbation to the dominant Heisenberg nearest neighbor interaction. These
results have great bearing on the interpretation of theoretical calculations
based on the kagome Heisenberg antiferromagnet model to the experiments on
ZnCu$_{3}$(OH)$_{6}$Cl$_{2}$.

View original: http://arxiv.org/abs/1202.4729