Evidence for Magnetic Interactions between Distant Cations in Yittrium Iron Garnet

The NMR spectrum of ${}^{57}\mathrm{Fe}$ nuclei in high purity ${\mathrm{Y}}_3{\mathrm{Fe}}_5{\mathrm{O}}_{12}$ garnet (YIG) is reported. The satellite structure of this spectrum is caused by an antisite defect ( ${\mathrm{Y}}^{3+}$ ion replacing an ${\mathrm{Fe}}^{3+}$ ion). Resolved satellite lines, which correspond to the ${\mathrm{Fe}}^{3+}$ ion in six different cation coordination spheres around the defect, are observed. In particular, satellite lines arising from the ${\mathrm{Fe}}^{3+}$ ions' distance of which from the defect is as large as 1.07 nm (11th coordination sphere) are identified unambiguously. The results yield information on the range of magnetic interactions in YIG.