Local environment and vibrational characteristics of 119Sn(II) Mِssbauer probe atoms located on the surface of Cr2O3 microcrystals

Two different sites have been evidenced for SN(II) dopant atoms located at the surface of the Cr2O3 substrate. Their inequivalence appears to be essentially due to the number of neighboring Cr(III) cations which are responsible for the magnetic hyperfine fields H transferred at the 119Sn nuclei. While a large difference is observed in the saturation values of H, the isomer shift and quadrupole splitting—which are predominantly determined by tin-oxygen bonding—differ for the two sites to a lesser extent. Moreover, the main component Vzz of the electric field gradient at 119Sn nuclei is found, in both cases, to be negative and oriented at the same angle with respect to the c-axis of the Cr2O3 lattice. The magnetic ordering temperature detected by the surface-located 119Sn(II) atoms appears to be in good agreement with that previously determined from antiferromagnetic resonance experiments for undoped Cr2O3. The Goldanskii-Karyagin effect, which is observed for Sn(II) dopant atoms in the paramagnetic region, indicates that the mean square vibration amplitudes are smaller along the Vzz axis than perpendicular to this direction.