Mِssbauer characterization of tin dopant ions in the antiferromagnetic ilmenite MnTiO3

Mössbauer parameters of 119Sn diamagnetic dopant cations in an antiferromagnetic compound having the ilmenite structure are for the first time reported. The spectra reveal a well resolved hyperfine splitting pattern of combined magnetic and quadrupole interactions (at 5 K, δ=0.19 mm/s, H1=52.5 kOe, eVZZQ3/2=−0.80 mm/s, θ≈0°). This spectral component whose contribution (A1=82%) represents more than four fifths of the total amount of the dopant (Sn/(Mn+Ti)=1/200) is assigned to Sn(IV) ions located in the bulk of MnTiO3, on the Mn(II) site, and with a Mn(II) vacancy in their nearest surrounding. Two spectral components with minor contributions are also observed: one of them (H2≈25 kOe, A2=8%) can be assigned to Sn(IV) ions, in the MnTiO3 lattice as well, on a site where they exhibit a weaker spin polarization (this site could be the Ti(IV) one) and the other (H3=0 kOe, A3=10%) to SnO2 or/and Ti1−xSnxO2 clusters. The Néel temperature of MnTiO3 probed by the 119Sn dopant (TN=69±2 K) agrees well with the values previously provided by ESR and antiferromagnetic resonance measurements. Variation of H1 with temperature follows close the Brillouin function for S=5/2. No perturbation appears in the Mössbauer spectra around T=90 K where a broad peak, characteristic of 2D magnetic interactions, is observed on the static magnetic susceptibility curve.