Covalency effects reflected in the magnetic form factor of low-dimensional cuprates

We analyze the magnetic form factor of Cu2+ in low-dimensional quantum magnets by taking the metal-ligand hybridization into account explicitly. In this analysis, we use the form of magnetic Wannier orbitals, derived from first-principles calculations, and identify contributions of different atomic sites. We demonstrate that covalency of metal-ligand interactions has a strong effect on the magnetic form factor and must be taken into account in the evaluation of magnetic neutron scattering. The use of covalent form factors facilitates quantitative description of inelastic neutron-scattering data for BaCuSi2O6 that would not be possible when ionic form factors are used. We also propose easy-to-use approximations of the partial orbital contributions to the magnetic form factor in order to give microscopic explanation for the results obtained in previous first-principles studies. © 2015 American Physical Society