Improved analysis of hyperfine fields in Fe, Co and Ni, and application to orbital magnetism in intermetallic compounds

Abstract

The nuclear hyperfine fields for elemental bcc Fe, fcc and hcp Co, and fcc Ni are analyzed in terms of the separate Fermi contact, orbital, and dipolar contributions. In contrast with earlier analyses, we have corrected the results from first-principles band structure calculations of these contributions for errors in the calculated spin and orbital moments, using experimental data. The absolute values of the resulting predicted hyperfine fields are about 30% smaller than the experimental values. The error amounts for the systems studied to about −4 T per unit of 3d spin magnetic moment (in μ B). This result establishes the systematic nature of errors in first-principles hyperfine field calculations, and is consistent with the point of view put forward earlier that the local spin density approximation, used in the calculations, fails to describe correctly the intra-atomic s-d exchange interaction which gives rise to the Fermi contact hyperfine field. It is proposed that after a correction for this error the orbital magnetic moments may be derived from the experimental saturation magnetization and hyperfine field, combined with results of a scalar relativistic calculation of these quantities. The analysis is applied to orbital magnetism at Fe and Co sites in the intermetallic compounds FePd, YFe 2, Fe 2B, FeB and Co 2B.