THE MAGNETISM OF 3D IMPURITIES IN ALKALI-METALS

Cluster calculation of the spin local magnetic moment of Fe in alkali metals is performed. A large Fe moment is retained, independent of the cluster size, even under relatively large compressions. The Fe 3d majority sub-band for both E(g) and T-2g symmetries are full, indicating a larger magnetic exchange splitting than the crystal field, as has been confirmed by direct computation. The 3d local density of states at the Fe site is found to consist of a single narrow, structureless peak independent of the alkali matrix; however, a small split appears in the minority sub-band in the case of Li and under compression in other metals. The bond order between the 3d atom and the neighboring alkali atoms is found to be vanishingly small for the majority electrons whereas the minority electrons retain a large value. The magnetic hyperfine field at the Fe site, due to the spin contact term, is found to be positive in spite of the large local moment. This is attributed to the cancellation resulting from the large positive valence contribution. The local magnetic moment and exchange splitting at 3d impurities in Na show a maximum at Cr and their ratio, which gives the exchange integral, increases from about 0.7 eV/mu(B) at Sc to about 0.9 eV/mu(B) at Ni. The Stoner type criterion is consistent with the retained local magnetic moment.