An impurity in the vicinity of the Fe-57 nucleus induces a specific structu
re of satellite lines in the NMR spectrum, the intensities of which are pro
portional to the impurity concentration. Recently achieved sensitivity make
s it possible to detect as little as 0.02% impurity. Spectra of nominally p
ure YIG epitaxial films, containing Pb, Ga, Al, Si, Pt, Ca impurities and '
antisite' defects are presented to illustrate the approach. (C) 1999 Elsevi
er Science B.V. All rights reserved.