NMR-STUDY OF GA AND AL SUBSTITUTED HEXAGONAL FERRITES WITH MAGNETOPLUMBITE STRUCTURE

Fe-57 NMR spectra and relaxation rates in lead hexaferrite single crys tals PbFe12O19, PbFe12-xGaxO19, (x=0.42, 1.2) and PbFe12-xAlxO19, (x=0 .21) have been measured at 4.2 K using spin echo technique. Besides th e main lines corresponding to the nonequivalent positions of Fe3+ ions in the magnetoplumbite structure, the satellite lines caused by subst itution in the vicinity of resonating nuclei have been observed. The d ependence of the NMR spectrum on the external magnetic field has been used to separate the overlapped satellites from different iron sites. The most distant satellites have been assigned to the resonance of iro n nuclei at 4f1 site with substitution at 12k and 2a sites in their vi cinity. A strong preference of 2a site for Al substitution has been fo und.