Effective intersublattice exchange couplings in rare-earth–transition-metal intermetallics from anab initiocalculation

A method is outlined for the ab initio determination of effective intersublattice exchange couplings ${\mathit{J}}_{\mathrm{RT}}$ in rare-earth–transition-metal intermetallics. The results obtained for ${\mathit{R}}_2$ ${\mathrm{Fe}}_{14}$B (R=Gd,Tb,Dy) and ${\mathrm{Ho}}_2$ ${\mathrm{Fe}}_{17}$ by the linear-muffin-tin-orbital theory in atomic sphere approximation are in excellent agreement with experimental data. It is shown that ${\mathit{J}}_{\mathrm{RT}}$ is not exclusively determined by the exchange-correlation part, but also strongly by other contributions to the total energy.