Consequences of the intrachain dimer-monomer spin frustration and the interchain dimer-monomer spin exchange in the diamond-chain compound azurite Cu3(CO3)2(OH)2

The spin lattice appropriate for azurite Cu-3(CO3)(2)(OH)(2) was determined by evaluating its spin exchange interactions on the basis of first principles density functional calculations. It is found that azurite is not well described as an isolated diamond chain with no spin frustration, but is better modeled as a two-dimensional spin lattice in which diamond chains with spin frustration interact through the interchain spin exchange in the ab-plane. Our analysis indicates that the magnetic properties of azurite at low temperatures can be approximated on the basis of two independent contributions, i.e., isolated dimer and effective uniform chain contributions. This prediction was verified by analyzing the magnetic susceptibility and specific heat data for azurite.