Isomer Shifts of ${\mathrm{Fe}}^{57}$ in ${\mathrm{Fe}}_2$${\mathrm{O}}_3$ and Rare-Earth Iron Garnets

The electron densities associated with the molecular complex used previously to explain the quadrupole coupling constants of ${\mathrm{Fe}}^{57}$ have been shown to explain consistently the isomer shifts for equivalent iron sites in ${\mathrm{Fe}}_2$ ${\mathrm{O}}_3$ and two inequivalent iron sites in several rare-earth iron garnets as well. The relative change in the charge radius of ${\mathrm{Fe}}^{57}$ nucleus has been deduced as -4.1 × ${10}^{-4\mathrm{}}$ (including relativistic effects).