First-principles investigation of magnetism and electronic structures of substitutional $3d$ transition-metal impurities in bcc Fe

摘要

The magnetic and electronic structures of $3d$ impurity atoms from Sc to Znin ferromagnetic body-centered cubic iron are investigated using theall-electron full-potential linearized augmented plane-wave method based on thegeneralized gradient approximation (GGA). We found that in general, the GGAresults are closer to the experimental values than those of the local spindensity approximation. The calculated formation enthalpy data indicate theimportance of a systematic study on the ternary Fe-C-$X$ systems rather thanthe binary Fe-$X$ systems, in steel design. The lattice parameters areoptimized and the conditions for spin polarization at the impurity sites arediscussed in terms of the local Stoner model. Our calculations, which areconsistent with previous work, imply that the local spin-polarizations at Sc,Ti, V, Cu, and Zn are induced by the host Fe atoms. The early transition-metalatoms couple antiferromagnetically, while the late transition-metal atomscouple ferromagnetically, to the host Fe atoms. The calculated totalmagnetization ($M$) of bcc Fe is reduced by impurity elements from Sc to Cr asa result of the antiferromagnetic interaction, with the opposite effect forsolutes which couple ferromagnetically. The changes in $M$ are attributed tonearest neighbor interactions, mostly between the impurity and host atoms. Theatom averaged magnetic moment is shown to follow generally the well-knownSlater-Pauling curve, but our results do not follow the linearity of theSlater-Pauling curve. We attribute this discrepancy to the weak ferromagneticnature of bcc Fe. The calculated Fermi contact hyperfine fields follow thetrend of the local magnetic moments. The effect of spin-orbit coupling is foundnot to be significant although it comes into prominence at locations far fromthe impurity sites.