Synthesis, structure and magnetic properties of copper hydroxysulfates

Cu-3(OH)(4)SO4 and Cu-4(OH)(6)SO4, synthetic equivalent of antlerite and brochantite minerals, have been obtained by hydrothermal synthesis from copper sulfate, soda and H2O or D2O. Their structures have been refined from single crystal X-ray and/or powder neutron diffraction data. They consists of edge-shared copper octahedron infinite chains connected to each other to define either triple chains in the case of antlerite or corrugated planes in the case of brochantite. Sulfate groups connect the former copper entities. From magnetic susceptibility measurements, both samples reveal a transition towards a 3D antiferromagnetic long range order at low temperature. In the paramagnetic domain, AF interactions are predominant for brochantite whereas ferromagnetic ones are evidenced for antlerite. The magnetic structures have been determined from powder neutron diffraction data and reveal the presence of ferromagnetic chains AF coupled. The magnetic results have been related to the Cu-O-Cu bridge angle values. (C) 2003 Elsevier Science Ltd. All rights reserved.