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We present a combined experimental and theoretical study of the mineral atacamite Cu2Cl OH 3. Density functional theory yields a Hamiltonian describing anisotropic sawtooth chains with weak 3D connections. Experimentally, we fully characterize the antiferromagnetically ordered state. Magnetic order shows a complex evolution with the magnetic field, while, starting at 31.5 T, we observe a plateaulike magnetization at about Msat 2. Based on complementary theoretical approaches, we show that the latter is unrelated to the known magnetization plateau of a sawtooth chain. Instead, we provide evidence that the magnetization process in atacamite is a field driven canting of a 3D network of weakly coupled sawtooth chains that form giant moments

Low temperature neutron diffraction and NMR studies of field induced phases in linarite are presented for magnetic fields H amp; 8741;b axis. A two step spin flop transition is observed, as well as a transition transforming a helical magnetic ground state into an unusual magnetic phase with sine wave modulated moments amp; 8741; H. An effective J 1 amp; 8722;J 2 single chain model with a magnetization dependent frustration ratio amp; 945;ef f amp; 8722;J 2 J 1 is proposed. The latter is governed by skew interchain couplings and shifted to the vicinity of the ferromagnetic critical point. It explains qualitatively the observation of a rich variety of exotic longitudinal collinear spin density wave, SDWp, states 9 amp; 8805; p amp; 8805; 2

We study the strongly anisotropic quasi one dimensional S 1 quantum magnet NiCl2 amp; 8901;4SC NH2 2 using elastic and inelastic neutron scattering. We demonstrate that a magnetic field splits the excited doublet state and drives the lower doublet state to zero energy at a critical field Hc1. For Hc1 lt; H lt; Hc2, where Hc2 indicates the transition to a fully magnetized state, three dimensional magnetic order is established with the AF moment perpendicular to the magnetic field. We mapped the temperature magnetic field phase diagram, and we find that the total ordered magnetic moment reaches mtot 2.1 amp; 956;B at the field amp; 956;0H 6 T and is thus close to the saturation value of the fully ordered moment. We study the magnetic spin dynamics in the fully magnetized state for H gt; Hc2, and we demonstrate the presence of an AF interaction between Ni2 on the two interpenetrating sublattices. In the antiferromagnetically ordered phase, the spin waves that develop from the lower energy doublet are split into two modes. This is most likely the result of the presence of the AF interaction between the interpenetrating lattices

Azurite, a natural mineral made up of CuO chains, is also an intriguing spin-1/2 quantum magnet. There has been much debate as to the 1-dimensional (1D) nature of this material by theorists and experimentalists alike. The focus of this debate lies in the interactions between Cu-ions within the antiferromagnetically ordered state below 1.9 K. We present high-resolution inelastic neutron scattering data which highlight the complexity of the magnetic ground state of azurite. The application of magnetic fields and temperatures were used to probe the excitations revealing important information about the dynamics in this system. From this we are able to conclude that the 1D Heisenberg antiferromagnetic spin chain model is not sufficient to describe the dynamics in azurite. Instead additional coupling including interchain interactions and an anisotropic staggered field are necessary to fully model the observed excitations., Comment: 8 pages, 11 figures