Charge and Spin Density Perturbation on Iron Nuclei by 4d and 5d Impurities Substituted on the Iron Sites in a-Fe

摘要

The paper is aimed at the review of the charge and spin density perturbation on the iron nucleus in the BCC iron-based binary alloys containing either 4d (Is Mo, Ru, Rh, Pd) or 5d (Os, Ir, Au) metals as an impurity. Additionally, Ga has been used as such an impurity as well. Measurements have been performed by means of the 'Fe transmission Mossbauer spectroscopy at room temperature. Mossbauer data were treated assuming random distribution of the impurity over the iron sites and additive effect for the charge density perturbation, and additive effect, in the algebraic sense, for the corresponding spin density perturbation. Hence, the effect of the impurity depends solely on the distance between the impurity and the iron nucleus under above assumptions. It has been found that impurities being further away than a third or, in some cases, than the second neighbor do not contribute directly to the charge and spin perturbation. On the other hand, they usually have some minor effect on the average charge and spin density. Generally, the perturbation to either charge or spin density has some oscillatory character versus distance from the impurity. Substitution of the impurities with the increasing number of 4d or 5d electrons leads to the lowering the electron density on the iron nucleus and causes decreased band spin density on this nucleus. Impurities with 5d electrons have generally stronger effect on the charge and spin density perturbation than impurities with 4d electrons.