HYPERFINE FIELD ANISOTROPY ON IRON NUCLEI IN BARIUM HEXAFERRITE

The NMR spectra of Fe-57 nuclei in a barium hexaferrite single crystal were measured by spin-echo technique at 4.2 K. An external magnetic h eld of 1.4 and 2.7 T was applied in several different directions in th e hexagonal plane in order to detect the influence of the hyperfine an isotropy on the resonance line positions. The number of observed NMR l ines was found to agree with our prediction, based on the site symmetr y analysis. The dependences of the NMR frequencies on the magnetizatio n direction were fitted to determine (after subtracting the dipolar he ld anisotropy) the hyperfine field anisotropy tensors for each iron si te. (C) 1998 Elsevier Science B.V. All rights reserved.