Stoner exchange interaction in transition metals

The theory of magnetism in transition metals is often expressed in terms of a Stoner exchange parameter I. Results for I are presented from electronic-structure calculations with correlations for a d-band-only Hubbard type of Hamiltonian. The main effects are: (a) Due to correlation, I depends substantially on the volume via the bandwidth. (b) There are analogous corrections to lattice constants calculated with the local-density approximation (LDA). (c) I also depends on magnetization, band filling, and crystal structure. (d) In Ni the reduction of charge and spin fluctuations almost eliminates the contribution to I of exchange between different orbitals. (e) I computed in the LDA is usually overestimated by 10%--20% because the LDA largely neglects spin correlations.