Crystal and Magnetic Structure of Two New Frustrated quantum Magnets

Frustration in Heisenberg spin systems originates from antiferromagnetic networks of triangles or tetrahedra. Of the possible model systems, the 3-dimensional network of corner-shared triangles (known as the hyperkagome lattice) has not been explored experimentally despite predictions that it should give rise novel ground states. We have successfully synthesized powder samples of two new cuprates. The 1st, 2nd and 3rd neighbour interactions couple the Cu ions into isolated triangles, a hyperkagome lattice and uniform chains respectively. Our magnetic susceptibility reveals a broad maximum in both samples while long-range magnetic order occurs at a much lower temperature as is typical of quantum magnets. Here we wish to determine the crystal and magnetic structure. The nature of the magnetic ordering will reflect the exchange interactions and provide insights into the underlying physics.