The Isomer Shift in119Sn and the Quadrupole Moment of the First Excited State

Local properties and phase transitions in Sn doped antiferroelectric PbHfO3single crystal

Pb(Hf1-xSnx)O3single crystals withx= 0.23 were characterized using single-crystal x-ray diffraction in the wide temperature range. The information on the structure of two intermediate phases, situated between low temperature antiferroelectric and high temperature paraelectric phases, has been obtained. The lower-temperature intermediate AFE2 phase is characterized by incommensurate displacive modulations in the Pb sublattice. The higher temperature intermediate IM phase is characterized by rotations of oxygen octahedra, primarily in the form of anti-phase tilts, which are also present in the lower-temperature AFE2 phase. For the same crystal,119Sn Mossbauer effect in the temperature range from 300 K to 600 K has been used to study phase transitions mechanism. Two kinds of quadruple splitting have been found. It implies that two different environments of the central Sn ion exist. The observed two kinds of quadruple splitting do not disappear in the whole investigated temperature range which confirm that even far aboveTCthe structure of paraelectric phase is locally non-centrosymmetric.

Tailoring the physical and chemical properties of Sn1-xCoxO2 nanoparticles: an experimental and theoretical approach

In this work, we present a coupled experimental and theoretical first-principles investigation on one of the more promising oxide-diluted magnetic semiconductors, the Sn_1-xCo_xO₂ nanoparticle system, in order to see the effect of cobalt doping on the physical and chemical properties. Our findings suggest that progressive surface enrichment with dopant ions plays an essential role in the monotonous quenching of the surface disorder modes. That weakening is associated with the passivation of the oxygen vacancies as the Co excess at the surface becomes larger. Room-temperature ¹¹⁹Sn Mössbauer spectroscopy data analysis revealed the occurrence of a distribution of isomer shifts, related to the different non-equivalent surroundings of Sn⁴⁺ ions and the coexistence of Sn²⁺/Sn⁴⁺ at the particle surfaces provoked by the inhomogeneous distribution of Co ions, in agreement with the X-ray photoelectron spectroscopy measurements. Magnetic measurements revealed a paramagnetic behavior of the Co ions dispersed in the rutile-type matrix with antiferromagnetic correlations, which become stronger as the Co content is increased. Theoretical calculations show that a defect with two Co mediated by a nearby oxygen vacancy is the most likely defect. The predicted effects of this defect complex are in accordance with the experimental results.

The stannides RE 3Au6Sn5 (RE = La, Ce, Pr, Nd, Sm) – synthesis, structure, magnetic properties and 119Sn Mössbauer spectroscopy

The Ce3Pd6Sb5-type rare earth stannides RE 3Au6Sn5 (RE = La, Ce, Pr, Nd, Sm) were synthesized by arc-melting of the elements and subsequent annealing in open tantalum crucibles within sealed evacuated silica ampoules. The polycrystalline samples were studied by powder X-ray diffraction. The structures of three crystals were refined from single crystal X-ray diffractometer data: Pmmn, a = 1360.3(9), b = 455.9(2), c = 1023.6(4) pm, wR2 = 0.0275, 1069 F 2 values, 48 variables for Ce3Au6Sn5, a = 1352.4(4), b = 455.1(1), c = 1023.7(3) pm, wR2 = 0.0367, 1160 F 2 values, 48 variables for Nd3Au6Sn5, and a = 1339.8(2), b = 452.80(7), c = 1012.4(2) pm, wR2 = 0.1204, 1040 F 2 values, 49 variables for Sm3Au5.59(2)Sn5.41(2). One of the gold sites of the samarium compound shows a significant degree of Au/Sn mixing. The RE 3Au6Sn5 structures are composed of three-dimensional [Au6Sn5] polyanionic networks with the two crystallographically independent rare earth atoms in larger cages, i.e., RE1@Au10Sn6 and RE2@Au8Sn8. The [Au6Sn5] network is stabilized by Au–Sn (266–320 pm), Au–Au (284–301 pm) as well as Sn–Sn (320 pm; distances given for the cerium compound) interactions. Temperature-dependent magnetic susceptibility measurements reveal an antiferromagnetic ordering only for Sm3Au6Sn5, while the other compounds exhibit Curie–Weiss paramagnetism. 119Sn Mössbauer spectroscopy shows resonances in the typical range for intermetallic tin compounds where tin takes part in the polyanionic network [isomer shifts between 1.73(1) and 2.28(1) mm·s−1]. With the help of theoretical electric field gradient calculations using the WIEN2k code it was possible to resolve the spectroscopic contributions of all three crystallographically independent atomic tin sites in the 119Sn spectra of RE 3Au6Sn5 (RE = La, Ce, Pr, Nd, Sm).

Thiostannate tin-tin bond formation in solution: in situ generation of the mixed-valent, functionalized complex [{(RSn(IV))2(mu-S)2}3Sn(III)2S6]

In broad daylight: The double-decker thiostannate [(RSn(IV))(4)S(6)] (1, R = CMe(2)CH(2)COMe) condenses to form [{(RSn(IV))(2)(mu-S)(2)}(3)Sn(III)(2)S(6)] (2; see picture). This mixed-valent complex, which formally contains both Sn(III) and Sn(IV) atoms as confirmed by Mössbauer spectroscopy and DFT calculations, forms by a complicated, concerted mechanism. Additionally, 2 provides six carbonyl groups for further derivatization.

Chemical aspects of the Mössbauer effect

The Mössbauer parameters ΔE Q (quadrupole splitting) and δ (the chemical shift) for iron compounds are discussed in relation to the electronic properties of the iron atoms, the known structural and magnetic properties of the compounds, their absorption spectra, and the ligand field strengths. The structural significance of the results obtained for some of the compounds experimentally studied in this work and elsewhere is given.

Mossbauer Effect in Hemoglobin with Different Ligands

Recoil-free nuclear gamma-ray resonance adsorption was observed in the iron-57 of blood. The spectral parameters are dependent on the ligand bound to the iron atoms in hemoglobin. The results are interpreted in terms of isomeric shifts and quad rupole splittings.