Predicted spin-orbit coupling effect on the magnetic ordering of crystalline uranium dioxide

摘要

The magnetic ordering of fluorite structure uranium dioxide has been investigated using fully-relativistic linear combinations of Gaussian type orbitals-fitting function (LCGTO-FF) calculations, within the generalized gradient approximation (GGA) to density functional theory. Three types of collinear spin-orderings were considered; ferromagnetic with spins aligned in the (001) direction and two antiferromagnetic (001) layer structures with spins aligned either perpendicular to each plane (001) or parallel to each plane (100). For each ordering, the total energy and spin-moment were calculated both with and without spin-orbit coupling. The ferromagnetic ordering is found to be energetically preferred to the antiferromagnetic orderings, contrary to experiment, whether or not spin-orbit coupling is included. Spin-orbit coupling is shown to have a significant quenching effect on the spin-moment and also introduces a strong magnetic anisotropy in the antiferromagnetic state that favors the (001) alignment over the (100) alignment.