Oxidation-induced change in spin polarization of the antimony Mِssbauer dopant on the surface of Cr2O3 crystallites

121Sb Mössbauer measurements show that oxidation of Sb(III) dopant ions located on the surface of Cr2O3 increases the value of the transferred magnetic hyperfine field H(121Sb) by a factor of about 2. This change is analogous to that previously reported for the 119Sn Mössbauer dopant located on the surface of the same matrix. In both cases, the increase in H values, which can be related to removal of the Sb(III) or Sn(II) lone-pair electrons, indicates that spin polarization of both Sb(V) and Sn(IV) dopants within magnetically ordered insulators is governed by 3d-electron density transfer from neighboring magnetic cations into 5s orbitals of the diamagnetic ones. Further comparison of relevant H(121Sb) and H(119Sn) values points to location of Sb(III) dopant ions mainly on sites with only one neighboring Cr(III) while isoelectronic Sn(II) dopant was shown to occupy surface sites of two types with one and three Cr(III) neighbors, respectively. Lower values of H characterizing both Sb(III) and Sn(II) are probably due to another spin polarization mechanism which involves participation of weakly magnetized 2s and 2p-electrons of neighboring O2−.