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+).