Correlation of the internal fields, magnetic moments, and site preferences inFe3−xMnxSialloys

Abstract

A detailed study of changes in the internal fields at Mn, Fe, and Si nuclei in the solid solutions of ${\mathrm{Fe}}_{3-x}{\mathrm{Mn}}_x\mathrm{Si}$, $0\le x\le 1.6$, as a function of composition has been made by spin-echo NMR at 1.28 K and in zero external magnetic field. Resonances due to Mn in three crystallographically different sites are observed. For $x<\mathrm{}0.75\mathrm{}$, Mn enters predominantly the site with eight Fe first near neighbors and has an internal field of 259 kG shifted about 5.4 kG to lower values for each added Mn third near neighbor. For $x>\mathrm{}0.75\mathrm{}$, Mn atoms also enter the other transition-metal site which has four Fe and Mn, and four Si first near neighbors and has an internal field of about 28 kG at $x=0.75\mathrm{}$. This field shifts to lower values as $x$ increases. Mn enters the Si sites due to a small residual disorder of about 3% between Si and the Fe site with eight Fe first near neighbors. The internal field of Mn in these sites is about 127 kG at $x=0.08\mathrm{}$ and shifts slowly to higher values. The Fe and Si fields are compared with those in ${\mathrm{Fe}}_3$Si alloys. The values of the internal fields and their variation with concentration at all sites are consistent with the magnetic moment and magnetization data of Yoon et al. Contributions to the internal fields from various neighbors are analyzed.