Mössbauer Study of Isomer Shift, Quadrupole Interaction, and Hyperfine Field in Several Oxides ContainingFe57

Mössbauer absorption by ${\mathrm{Fe}}^{57}$ was used to study isomer shift, quadrupole splitting, and hyperfine fields in several oxides containing iron. The established relations between isomer shifts and ionic states of Fe were further confirmed by measurements on ${\mathrm{Fe}}^{2+}$ ${\mathrm{Ti}}_2$ ${\mathrm{O}}_5$, ${\mathrm{Fe}}_2^{3+}$Ti${\mathrm{O}}_5$ and several other mixed oxides. By utilizing this relation, in turn, to identify the ionic states when these are in doubt, it has been found that ${\mathrm{}(\mathrm{F}\mathrm{e},\mathrm{V})\mathrm{}}_2$ ${\mathrm{O}}_3$ incorporates the cation pair ${\mathrm{Fe}}^{3+}$ - ${\mathrm{V}}^{3+}$, rather than ${\mathrm{Fe}}^{2+}$ - ${\mathrm{V}}^{4+}$, and that "SrFe${\mathrm{O}}_3$" contains ${\mathrm{Fe}}^{4+}$ and ${\mathrm{Fe}}^{3+}$ in the ratio of 3:1. A well-defined quadrupole splitting was observed in ${\mathrm{Fe}}_{1-x}\mathrm{O}$ and in a number of the solid solutions (Fe,Mg)O, although their over-all symmetry is cubic. This is explained by the assumption of local asymmetry at the Fe nuclei caused either by vacancies or foreign ions. Hyperfine fields at the ${\mathrm{Fe}}^{3+}$ nuclei in ${\mathrm{}(\mathrm{F}\mathrm{e},\mathrm{C}\mathrm{r})\mathrm{}}_2$ ${\mathrm{O}}_3$, ${\mathrm{}(\mathrm{F}\mathrm{e},\mathrm{V})\mathrm{}}_2$ ${\mathrm{O}}_3$, and ${\mathrm{}(\mathrm{F}\mathrm{e},\mathrm{A}\mathrm{l})\mathrm{}}_2$ ${\mathrm{O}}_3$ have values between 520 and 540 koe when extrapolated to 0°K, and the results are discussed in conjunction with their magnetic properties.