INFLUENCE OF IMPURITIES AND DEFECTS ON THE NUCLEAR-RELAXATION IN YIG-FILMS

The relaxation of Fe-57 nuclei in yttrium iron garnet (YIG) is very se nsitive to the way in which charge compensation is achieved in these m agnetic insulators. Charge compensation becomes necessary either if no ntrivalent impurities are incorporated in the garnet structure or in t he presence of intrinsic defects. From measurements of the nuclear rel axation times T-1 and T-2 in epitaxial MG films doped with small amoun ts of Ca, Si or Pb, we conclude that the relaxation behavior at low te mperatures depends critically on the presence of certain intrinsic def ects, namely Fe2+. These ions also increase the optical absorption in the near infrared.