Full-potential linear-muffin-tin-orbital calculations of the magnetic properties of rare-earth–transition-metal intermetallics. I. Description of the formalism and application to the seriesRCo5(R=rare-earth atom)

For the series R${\mathrm{Co}}_5$ (R=rare-earth atom) various parameters occurring in the two-sublattice model of rare-earth–transition-metal intermetallics (local magnetic moments, intersublattice exchange fields, crystal field parameters, as well as magnetic hyperfine fields and electric field gradients) are calculated within the framework of the local-spin-density approximation (LSDA) and the full-potential linear-muffin-tin-orbital theory. Special emphasis is given to a determination of the crystal field parameter ${\mathit{A}}_2^0$. It is shown that it is absolutely indispensable to include the 5p states at the R site into the valence band and to avoid any spherical approximation for the effective potential. The quantity ${\mathit{A}}_2^0$ depends on the orientation of the aspherical 4f charge density, in contrast to a basic assumption of the two-sublattice model. As a result, the experiments in general yield some kind of average effective values which are different for different experiments. Application of the LSDA introduces rather large uncertainties for ${\mathit{A}}_2^0$ which cannot be totally removed but at least drastically reduced by physically motivated measures. © 1996 The American Physical Society.