ANTISITE DEFECTS IN YTTRIUM-IRON-GARNET

NMR of Fe-57 nuclei is used to study the (Y) over dot antisite defects (yttrium ions on the sites nominally occupied by iron) in yttrium-iro n garnet (YIG). In spectra of both tetrahedral and octahedral Fe(3+)io ns, satellite lines appear, corresponding to Fe3+ ions with this defec t in their vicinity. NMR was measured on a number of nominally pure YI G samples - single crystals, thin films as well as polycrystalline sam ples. The content x(y) per formula unit of the Y antisite defect (Y-a) was determined from the amplitude of the satellite lines and it lies in the interval 0.001<x(y)<0.03. In most cases the satellite lines cau sed by the Y-a defect are obscured by the satellites originating from other impurities. In two high purity single crystals the satellites ca used by Y-a dominate, however. In the NMR spectra of these single crys tals the satellite lines which correspond to the FC3+ ions in seven di fferent crystallographically inequivalent positions with respect to th e defect are resolved at low temperatures. Further unresolved satellit es emerge from the main lines as the temperature is increased.