Hierarchical geometric frustration in La3Cu2VO9

The crystallographic structure and magnetic properties of La3Cu2VO9 were investigated by powder neutron diffraction and magnetization measurements. The compound materializes geometric frustration at two spatial scales, within clusters and between clusters, and at different temperature scales. It is shown by exactly solving the Hamiltonian spectrum that collective spins are formed on each cluster at low temperature before inter-cluster coupling operates.