EXTENDED STONER FACTOR CALCULATIONS FOR THE HALF-METALLIC FERROMAGNETS NIMNSB AND CRO2

The electronic structures of NiMnSb and CrO2 were calculated using a spin-polarised scalar relativistic linear muffin-tin orbital (LMTO) method. The self-consistent calculations were performed for the observed experimental lattice constants. Cubic NiMnSb (MgAgAs-type structure) and rutile-structure CrO2 are found to be 'half-metallic ferromagnets', i.e. they have a semiconducting gap in the minority-spin bands but metallic majority-spin bands. The calculated magnetic moments in both compounds were found to be in good agreement with the experimental values. The possibility of metastable magnetic states is investigated via extended Stoner factor calculations. It is shown that the position of the Fermi level with respect to the bandgap is extremely sensitive to the exchange-correlation potential approximation.