Influence of Si on spin and charge density changes in bcc-iron

Abstract

The influence of Si on the 57Fe and 119Sn site hyperfine (hf) fields and isomer shifts has been studied for a series of Fe-Si alloys containing up to ca. 13 at% Si and ca. 0.9 at% 119Sn. The observed changes of the hf fields and the isomer shifts have been interpreted as reflecting spin and charge density changes, respectively. The following correlations could be established: hf field H(0,0) vs. isomer shift IS(0,0) of undisturbed atomic neighbour configurations (0,0), average hf field, H̄ vs. average isomer shift, IS ; average hf field, H̄ vs. average number of Si atoms within the first two neighbour shells, N̄. Based on the f correlations the following hf coupling constants have been determined: a) the hf coupling constant for s-like itinerant electrons are 690 kOe/s-el for Fe and 2100 kOe/s-el for Sn, b) the average hf coupling constants are 660 kOe/s-el and 2100 kOe/s-el for Fe and Sn, respectively. From the correlation between H̄ and N̄ the changes in the spin or charge densities caused be one Si atom per unit cell, η, have been deduced as follows: η(Fe)=0.17 and η(Sn)=0.03. Comparison is made with previously reported equivalent results for the Fe-Al system.