NUCLEAR MAGNETIC RESONANCE OF Fe57 NUCLEI IN COBALT-SUBSTITUTED YTTRIUM ORTHOFERRITE.

The spin echo of the Fe**5**7 nuclei was used to study YFeO//3 crystals in which Fe**3** plus was substituted with Co**2** plus and which exhibited spin reorientation transitions. The strongest NMR signals were observed at temperatures which, according to the results of measurements of the magnetic anisotropy constants, corresponded to the beginning or end of spin reorientation. The temperature dependence of the frequencies of NMR in domains was compared with the results of an earlier investigation of the frequencies of NMR in domain boundaries. The comparison confirmed the validity of the theory proposed by A. K. Zvezdin to explain the characteristics of the boundary NMR spectra of orthoferrites.