The hyperfine structure of the low-temperature Mössbauer spectra of dopant 119Sn4+ ions (0.4 at. %) in a fine crystalline MnO sample, characterized by X-ray diffraction and magnetic measurements, has been studied. The 119Sn spectra show that tin is distributed over positions with an inhomogeneous cationic environment. The appearance of such positions is explained by the local compensation for the excess charge of Sn4+ by manganese vacancies V Mn and segregation of defects resulting in precipitation of MnSnO3 clusters. The non-uniform distribution of Sn4+ and the related dependence of the number of broken magnetic bonds on the local tin concentration are responsible for the fluctuation of the T N values, which is “perceived” by 119Sn in different MnO crystallites. The 119Sn spectra exclude the possibility that tin enters into the composition of superpara-magnetic particles.

Magnetic hyperfine fields transferred at 119Sn probe atoms (in both Sn(II) and Sn(IV) valence states) in antiferromagnetic α-MnS have been for the first time investigated. At 6 K, a unique hyperfine splitting pattern (H = 27 kOe) was observed for the Sn(II) substituant, isovalent with Mn(II), and two for the Sn(IV) heterovalent substituant (H1 = 392 kOe and H2 = 296 kOe). The charge compensation mechanism is shown to mainly involve Mn(II) vacancy location in the vicinity of Sn(IV), the two magnetically non-equivalent surroundings of Sn(IV) being related to the two possible spin orientations of the missing nearest neighbor Mn(II). The large difference in H values observed for Sn(II) and Sn(IV) is interpreted as an indication of the prevalent contribution of 3d-5s transfer in the spin polarization of the diamagnetic impurity. The Mössbauer lattice temperature for the Sn(IV) probe (ΘM = 240 K) is found to be slightly higher than for the Sn(II) one (ΘM = 217 K).