Dynamics of azurite Cu_3(CO_3)_2(OH)_2 in a magnetic field as determined by neutron scattering

摘要

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 one-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 that 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.