Magnetic Order and Spin Fluctuations in the Spin-1/2 Three-Dimensional Frustrated Magnet Clinoatacamite, Cu$_{2}$(OH)$_{3}$Cl

We have performed thermodynamic and neutron scattering measurements on the S=1/2 three-dimensional antiferromagnet clinoatacamite, Cu$_{2}$(OH)$_{3}$Cl. The crystal lattice feature Cu$^{2+}$ ions arranged on a distorted kagom\'{e} lattice with weak magnetic coupling between adjacent planes. Long range magnetic order with a weak ferromagnetic moment emerges at the N\'{e}el ordering temperature, T$_{N}$ = 6.2 K. The value of $\Theta_{CW}$ is roughly 30 times larger than T$_{N}$, demonstrating that the material is highly frustrated. Magnetic Bragg peaks are not observed above background for temperatures between 6.2 and 18 K, even though previous $\mu$SR measurements observed muon oscillations in this temperature range. We present a possible model of the magnetic transitions and analyze the inelastic spectrum of the ordered state, taking into account anisotropic terms in the spin Hamiltonian.