Hyperfine field in YIG with charged substitution

Fe-57 NMR spectra were measured on thin films of yttrium iron garnet with d ivalent (Ca2+) and tetravalent (Ge4+) cation substitutions using the spin e cho technique at 4.2 K. A series of Y3-xCaxFe5-xGexO12 samples with 0 less than or equal to x less than or equal to 0.05 was prepared by an epitaxial growth from BaO/B2O3/BaF2 flux on gadolinium gallium garnet substrate. Sate llite lines corresponding to the iron ions having the Ge4+ and Ca2+ in thei r neighbourhood were identified. The sample with the germanium content of x (Ge) = 0.004 and (110) substrate orientation was used for a detailed study: NMR spectra of this sample were measured in an external magnetic field of 0.1 T applied along several directions in the plane of the film. The modifi cation of the isotropic part and the anisotropy tensor of the hyperfine int eraction caused by the Ge4+ substituent were obtained from the experimental data. The results were compared with those previously reported for trivale nt substitution (Ga3+).