Mössbauer characterization of 119Sn4 + Dopant ions in the antiferromagnetic ilmenite NiTiO3

Magnetic hyperfine splitting of the 119Sn4+ nuclear levels in the antiferromagnetic NiTiO3 was for the first time observed using the Mössbauer effect. For the majority of the 119Sn4+ dopant ions, the saturation value of the transferred hyperfine field (at 4.2 K, H=5.25T) is found to be equal to that previously reported for 119Sn4+ in the antiferromagnetic MnTiO3. This finding shows that in both ilmenites the spin polarization of Sn4+ is produced by the divalent cation half-filled eg2 orbitals involved in interlayer superexchange interactions and implies the location of the dopant within titanium (111) layers. The principal VzzVzz component of the EFG at the Sn4+ site in NiTiO3 is found to have a positive sign and be aligned along the [111] axis, as it was the case for Sn4+ in MnTiO3. Lattice-sum calculations on the basis of a simple ionic point-charge model, lead to an erroneous result (in either titanate the sign of VzzVzz on the Ti4+ site would be negative) and thus demonstrate their failure in identifying the Sn sites.