Tin-doped LuCrO<sub>3</sub>: A new type of material allowing the location of a <sup>119</sup>Sn Mössbauer spectroscopic probe on the gas–solid interface
Language
en
Article de revue
This item was published in
Solid State Communications. 2009, vol. 149, n° 33-34, p. 1333-1336
Elsevier
English Abstract
In situ 119Sn Mössbauer measurements show that annealing in hydrogen atmosphere of co-precipitated chromium and lutetium hydroxides, doped with 0.2 at.% Sn<sup>4+</sup>, results in the formation of Sn<sup>2+</sup> cations ...Read more >
In situ 119Sn Mössbauer measurements show that annealing in hydrogen atmosphere of co-precipitated chromium and lutetium hydroxides, doped with 0.2 at.% Sn<sup>4+</sup>, results in the formation of Sn<sup>2+</sup> cations on the surface sites of LuCrO<sub>3</sub> microcrystals. Such a distribution of dopant cations is consistent with the anomalously high concentration of tin revealed by X-ray photoelectron spectroscopy (XPS). The 19Sn spectrum recorded above the Néel point of LuCrO<sub>3</sub> attests to the distribution of Sn<sup>2+</sup> ions over two kinds of site. For both of them, the isomer shift and quadrupole splitting values agree with those previously reported for 119Sn<sup>2+</sup> on surface sites of several oxides other than the perovskite-type one. The instantaneous oxidation of tin upon contact with ambient air did not allow us to characterize the cationic surrounding of Sn<sup>2+</sup> by measurements involving sample transfer into a liquid-helium cryostat. Relevant information is obtained for the Sn<sup>2+→4+</sup> oxidized species located on the sites with unchanged <i>cationic</i> surroundings. The spectrum recorded at 4.2 K shows that nearly two-thirds of the Sn<sup>2+→4+</sup> species are spin-polarized to different extents. Comparison with Mössbauer parameters reported for 119Sn ions sitting in the regular Cr-substitution site in the bulk of LuCrO<sub>3</sub> allows us to ascribe the diffuse magnetic contribution to a distribution of Sn<sup>2+→4+</sup> species over Cr-substitution sites with lower (than in the bulk) number of neighboring Cr<sup>3+</sup> ions. The presence of an additional non-magnetic component in the spectrum of Sn<sup>2+→4+</sup> ions points to the location of the remaining Sn<sup>4+</sup> ions and, very likely, the predecessor Sn<sup>2+</sup> ones, on Lu-substitution sites with magnetically compensated (2Cr↑+2Cr↓) surroundings.Read less <
English Keywords
Magnetically ordered materials
Chemical synthesis
Point defects
Nuclear resonances
Origin
Hal imported